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COST 325
New Road
Monitoring Equipment
and M ethods
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Final Report of the Action
EUROPEAN
COMMISSION
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GENERAL
TRANSPORT
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European Cooperation
in the Field of
Scientific and Technical
Research
COST 325
New Road Monitoring
Equipment and Methods
Final Report of the Action
European Commission
Directorate General Transport
LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of
the Commission is responsible for the use which might be made of
the following information.
The views expressed in this publication do not necessarily
reflect the views of the European Commission
A great deal of additional information on COST Transport is available on the World Wide Web.
It can be accessed through the CORDIS server (http://www.cordis.lu/cost-transport/home.html)
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1997
ISBN 92-828-0307-4
© ECSC-EEC-EAEC, Brussels · Luxembourg, 1997
Reproduction is authorized, except for commercial purposes, provided the source is acknowledged
Printed in Belgium
In Memoriam:
RAY GODDARD
Ray Goddard served as the European Commission (COST Transport) representative and Scientific
Secretary on COST Action 325 (New Pavement Monitoring Equipment and Methods) Technical SubCommittee throughout the preparatory period during 1993 and early 1994. Following the signature of
the Memorandum of Understanding in 1994 by the founder nations, he then carried out the same duties
for the Management Committee until his untimely death in August 1994.
Ray made a huge contribution to the development of the Action as the principal link with the European
Commission, and was well known as a very efficient and hard-working individual who was also a
friend to all the Committee members. He had time for each individual, and used his linguistic abilities
very effectively to make each member feel at home and to encourage communication within the group.
We all miss him both as a friend and as a colleague.
This publication is dedicated to him in memory of his work and to express our gratitude for all his
effort.
CONTENTS
Page
IN MEMORIAM
TABLE OF CONTENTS
1
EXECUTIVE SUMMARY
5
ABSTRACT
7
1.
INTRODUCTION
9
2.
WORKPLAN
11
2.1
2.2
2.3
2.4
11
11
11
12
3.
Introduction
Scope
Methodology
Tasks
INFORMATION GATHERING
17
3.1
3.2
3.3
Source of information
State of practice at national level
Questionnaire overview
17
17
18
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
18
18
19
19
22
Introduction
Participating agencies and countries
Questionnaire outline
General
Summary
SURFACE DISTRESS
23
4.1
State of the art road surface distress assessment
23
4.1.1
4.1.2
4.1.3
4.1.4
23
23
24
26
26
26
29
29
Introduction
Surface distress
Assessment methods
Assessment systems
4.1.4.1
Photographic systems
4.1.4.2
Video systems
4.1.4.3
Holographic system
4.1.4.4
Infrared systems
4.1.4.5
Radarsystem
4.1.4.6
Acoustic systems
4.1.5
Discussion
4.1.6
Conclusions
4.1.7
Bibliography
29
29
30
31
31
4.2
Outcome of questionnaire
32
4.3
System performance requirements
47
4.3.1
Synthesis
47
4.3.2
Requirements
48
4.4
5.
Recommendations
50
4.4.1
4.4.2
50
52
Recommendations for users
Recommendations for research and development
BEARING CAPACITY ASSESSMENT
55
5.1
State of the art on Bearing Capacity Assessment
55
5.1.1
5.1.2
Ground Penetrating Radar
Deflection measurements
5.1.2.1 Manual static or rolling wheel methods
5.1.2.2 Automated rolling wheel methods
5.1.2.3 Automated stationary impulse load methods
5.1.2.4 Automated mobile dynamic load methods
5.1.3
Conclusions
5.1.4
References
57
58
60
62
62
63
66
67
Outcome of questionnaire
68
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.2.6
5.2.7
5.2.8
5.2.9
5.2.10
68
69
71
72
72
72
73
74
74
75
5.2
5.3
Aim of bearing capacity data collection
Methods of evaluating the bearing capacity of roads
Measurements with Benkelman or FWD
Measurements with Lacroix, Curviameter or similar devices
Measurements with other types of deflection meters
Quality assurance
Performance of methods in use
Needs in the field of acquisition of bearing capacity data
Treatment of data
New developments
System performance requirement
75
5.3.1
5.3.2
75
77
Synthesis
Requirements
5.4
6.
7.
Recommendations
79
5.4.1
5.4.2
79
79
Recommendations for users
Recommendations for research and development
PAVEMENT MANAGEMENT SYSTEMS (PMS)
83
6.1
6.2
6.3
6.4
83
84
86
87
Background
Outcome of questionnaire
Conclusions
Bibliography
GLOBAL SYNTHESIS
89
7.1
7.2
7.3
7.4
89
92
94
96
Background
Benefits of new pavement monitoring devices
Conclusions
References
APPENDICES
97
8.1
8.2
8.3
8.4
Technical Annex to the Memorandum of Understanding
State of practice reports
The questionnaire
Questionnaire database
98
104
173
189
8.4.1
8.4.2
189
197
8.5
8.6
8.7
8.8
Table of recipients and respondents
Statistical results
Glossary of common acronyms
Members of the Management Committee
FEHRL information
COST Transport Overview
214
219
222
224
EXECUTIVE SUMMARY
Road transport is the most important mode of surface transport in Europe and is fundamental to its
social and economic development. The total cost of road construction and maintenance, to European
governments, is measured in tens of billions of ECUs. To promote technical advances in these areas
FEHRL (Forum of European National Highway Research Laboratories) proposed, in 1991, a
programme of strategic research that has been supported and extended at European level within the
COST (European Co-operation in the field of Scientific and Technical research) framework. COST
Action 325 "New pavement monitoring equipment and methods" which started in late November 1992
was part of this strategic research programme.
It was recognised that the art of high-speed monitoring was well advanced in the areas of measuring
longitudinal and transverse road profiles, macro- and megatexture and friction. The assessment of road
bearing capacity and the detection and evaluation of surface distress, important from the road
management point of view was, however, being carried out using stationary or slow moving devices
respectively. Stationary or slow survey methods are hazardous for the personnel carrying out road
surveys as well as the travelling public. These methods, including laboratory evaluation of tapes or
filmstrips, are furthermore very time consuming and consequently very expensive. The very low rate of
data acquisition also makes these methods less suitable for network monitoring. With these facts in
mind it was decided that this COST Action should focus on high-speed methods for the assessment of
road bearing capacity and automated detection and evaluation of surface distress.
The COST Action 325 Technical Subcommittee decided to carry out a questionnaire inquiry
concerning currently used survey methods within the above areas, seeking information on current
practice, with a view to establishing a basis for the future development of high-speed devices.
Information on on-going development within these areas was also requested. As the information
collected using current as well as future survey methods are likely to form inputs to different kinds of
Pavement Management Systems (PMS), the Subcommittee decided that it was appropriate also to
inquire about the use of PMS. The inquiry was also supported by state-of-practice reports covering the
situation in the countries participating in this COST Action.
Following the signing of the Memorandum of Understanding (MoU) by eight countries the
Subcommittee was transformed into the COST Action 325 Management Committee with the task to
carry out the work planned by the Technical Subcommittee. The first meeting of the Management
Committee was held in early November 1994.
The questionnaire was sent out to 108 recipients in 21 countries representing central and local road
authorities, consultants and research institutes.
Regarding the detection and evaluation of surface distress the inquiry responses show that the visual
inspection at the site is the most common survey method, while quite a few collect images of the
surface at high-speed followed by visual evaluation in a laboratory. In some cases the automatic
collection is carried out in combination with visual inspection at the site. Automated evaluation of
collected images is reported to be at the development stage from only four countries, again supported
by visual methods. It shows that the users of these methods are relatively satisfied with the accuracy of
the methods even if not all types of surface distress are detected. The few existing automated evaluation
systems seem on the other hand to need further development. A number of needs were reported which
could be summarised as the need for a high-speed, high-resolution distress data collection system
capable of operating in daylight at normal varying traffic speeds and with an on-line data evaluation
system to detect different types of cracking (alligator, block, edge etc.), single cracks of different width,
length and direction as well as other types of distress such as bleeding and ravelling.
The responses to the part of the questionnaire addressing bearing capacity assessment methods show
that most countries rely on deflection measurements for the assessment of bearing capacity. The most
commonly used deflection measuring devices are the Falling Weight Deflectometer (FWD) and
Lacroix deflectograph, showing that most of the deflection surveys carried out in Europe are by means
of stationary devices (FWD) or by a slow moving device such as the deflectograph. Most of the
respondents seem to be satisfied with the performance of the devices they are using but are concerned
about traffic congestion issues and the related safety problem. This is also reflected in the fact that
about half of the responses indicate a need for high-speed measuring devices. A number of high-speed
devices are being developed but none are, as yet, suitable for routine survey work.
(PMS) are used in the majority of the countries covered by the questionnaire. The main purposes of
using the PMS are for the planning and prioritising within budget of multi-year maintenance work, to
determine rehabilitation measures for road sections and to make predictions on the evolution of
network condition.
In conclusion, there is a need for high-speed devices for the measurement of road surface deflection
and for the detection and automated evaluation of surface distress data. Based on the knowledge of the
state of development of presently available devices and of development work in progress it is
anticipated that devices suitable for routine surveys would be available within a timeframe of about
eight years. The combined information on deflection, distress, layer thicknesses and the changes of
road unevenness over time would greatly improve the accuracy of structural condition assessment of a
road network. They would also facilitate and improve the decisions on maintenance measures and the
prediction of the evolution of the network. The use of a multi-purpose high-speed vehicle would reduce
the cost of data collection and improve the safety for the personnel involved in monitoring the
condition of road networks.
ABSTRACT
The Report of COST Action 325 describes the research carried out to establish the operational
requirements for equipment capable of measuring and evaluating the surface distress and load bearing
capacity of roads at traffic speeds. Thirteen countries participated in this four-year study which
provides a basis for the development of suitable equipment to meet the present and foreseeable needs of
road network managers in Europe.
The study comprised, first a questionnaire survey of European countries in which present methods of
evaluating surface distress and load bearing capacity were assessed and needs were identified. Second
a review of the literature on state of the art equipment and of on-going developments. Finally the
information on needs and developments were analysed to define the technical and operational
requirements of equipment that would meet the present and foreseeable future needs of road network
managers.
The Report concludes that fully automated high-speed equipment for the assessment of surface distress
and load bearing capacity could be available for routine use within a period of about eight years.
Further, that the use of multi function equipment, capable of measuring both road surface condition and
load bearing capacity, would enhance the accuracy of condition assessment, reduce the cost of data
collection and improve safety for the personnel involved in monitoring the condition of road networks.
CHAPTER 1
INTRODUCTION
Road transport is the most important mode of surface transport in Europe and is fundamental to its
social and economic development. However rising trends in personal transport and in the amount of
freight transported by road is making increased demands on the capacity and the durability of the
highway infrastructure. Moreover the increasing constraint on infrastructure maintenance budgets is
causing highway authorities across Europe to seek ever greater efficiencies in the management of their
road networks.
To promote technical advances in this area, The Forum of National Highways Research Laboratories
(FEHRL) proposed, in 1991, a programme of strategic research to the Directorate General of Transport
of the European Commission; further details on the FEHRL organisation are given in Appendix 8.7. A
number of proposals from the FEHRL programme have been supported and extended at European level
within the COST (European Co-operation in the field of Scientific and Technical research) framework.
These COST Actions cover a range of research topics including improved designs for road pavements,
studies on the long term performance of pavements, the development of cost effective maintenance
management systems and of new and improved road monitoring technologies; this latter topic is the
subject matter of this report.
The technical requirements for COST Action 325 on «new road monitoring equipment and methods»
are described in Annex 2 of the Memorandum of Understanding (MoU) in Appendix 8.1.
Information on the surface and structural condition of roads is an essential requirement for the efficient
management of road networks. It permits the safety, riding quality and load bearing capacity of road
pavements to be assessed and, with the aid of appropriate pavement performance models and economic
analyses, the development of cost effective maintenance strategies for different categories of road
network. Thus in the COST Action 325 the requirements of other COST Actions, such as those on
pavement performance and pavement management systems, have been noted to ensure maximum
benefit from the research.
A critical requirement at the road network level is that condition data be collected efficiently,
quantitatively and with sufficient accuracy and resolution to allow trends of condition with time and or
traffic to be defined. For most surface condition parameters, such as skid resistance, texture,
longitudinal and transverse profiles a range of equipment is available for the routine measurement of
these parameters at traffic speeds; an inventory of these equipment is given in the PIARC Report
"Inventory of surface characteristics measuring equipment" published in 1995. The position of surface
distress assessment is however less satisfactory. Even with the use of computer-aided video technology
the extraction of surface defects from video films still requires visual assessment with all that this
entails in terms of observer time and lack of reliability due to the subjectivity of the assessment process.
The measurement of load bearing capacity of pavement networks, using equipment that measures
pavement deflection under a specified load, is also a slow and expensive process. Because pavement
deflections are of small amplitude all existing measurement techniques employ a stationary mechanical
frame of reference which limits operating speed. Research is needed into the use of non-contact highspeed deflection measurement systems to overcome this limitation. The use of radar equipment to
provide accurate measurements of road pavement thickness to assist with the interpretation of
deflection data also needs to be considered.
COST Action 325 has therefore focused on the requirements for the development of a fully automated
and high-speed system for surface distress assessment and of a high-speed device for the measurement
of pavement deflection. The development of such systems would not only provide more reliable road
condition data at a lower cost but would also improve the safety of operators engaged in the collection
of this data.
Though some of the information presented in the report could be used for project level work the
emphasis is on the needs of the network manager.
To ensure that the outcome of the action is compatible with the needs of network managers the
following objectives were agreed for COST Action 325.
•
to ascertain the needs of those who use condition data to manage road networks across Europe
with particular reference to their use of road monitoring equipment and formal pavement
management systems
•
to report the state of the art on current research and developments of high-speed automated
systems for the assessment of surface distress and of load bearing capacity
•
to provide recommendations for new and improved measuring systems that would be compatible
with user needs including technical, safety and cost aspects.
The work plan to achieve the MoU objectives is described in Chapter 2. Chapter 3 covers the method
used to survey user practice and needs while Chapters 4 and 5 present state of the art reports, user
survey analyses and the requirement and recommendations for the development of surface distress
assessment and load bearing capacity measurement systems respectively. Chapter 6 describes
developments and use of pavement management systems in Europe. Finally Chapter 7 provides a
synthesis of the results of COST Action 325 and discusses the technical and economic factors
associated with the implementation of the developments proposed in this report.
The main beneficiaries of the information contained in this report are likely to be research institutions
and industry for the technical developments described in Chapters 4 and 5 and central and local
government policy makers for the potential of new developments to further improve efficiency in the
management of road networks.
10
CHAPTER 2
WORKPLAN
2.1
Introduction
To initiate COST Action 325 a Technical Sub-Committee was set up to define:
•
•
•
the scope of the activities to be undertaken
the methodology to be adopted
the tasks to be carried out.
These activities defined the content of the Technical Annex to the Memorandum of Understanding.
In the following sections the decisions and activity plan agreed by the Management Committee of
COST Action 325 in relation to each of these items are briefly summarised.
2.2
Scope
The issues considered before defining the scope of the study included:
•
•
•
whether or not the different requirements of road authorities, research institutions and industry
should be taken into account in the proposed study
whether, or not, the study should be confined to developments within the member COST countries
the form of output required from the study.
It was agreed that the study should:
•
establish the views of road authorities, research institutions and industry on current practice and
their perceived need for improvement
•
evaluate information on new and improved technical developments both within and outside the
COST countries
•
provide a report on new or improved technical developments that would, as far as possible, satisfy
the needs of end users.
The objectives of the COST Action 325 study are set out in the Technical Annex to the Memorandum
of Understanding in Appendix 8.1.
2.3
Methodology
The methodology adopted to achieve the objectives set out in the MoU included:
•
A questionnaire survey of road authorities, research institutions and industry within and outside the
countries participating in COST Action 325. The questionnaire was formulated to elicit detailed
information from each member country on:
II
-
current practice in carrying out surface distress and load bearing capacity assessments
(both measurement and analysis processes)
the use made of these assessments by road managers, researchers etc.
the extent and nature of the road networks on which these assessments are carried
out
any perceived shortcomings in existing practices and identification of future needs with
particular reference to the role of road condition survey devices in providing input data
to pavement management systems
•
A review of state of the art developments in the fields of surface distress and bearing capacity
assessment systems. Much of the information in the state of the art review was provided by
members of the COST Action 325 Management Committee who are listed in Appendix 8.6.
•
Analysis of responses to the questionnaire survey to provide quantitative information on current
practice and needs.
•
A synthesis of the information, on needs, identified from the questionnaire analysis, with that on
developments from the state of the art reviews to establish the requirements for:
•
-
a fully automated surface distress assessment system and
-
high-speed deflection measurement system.
Preparation of the report on the COST Action 325 study
2.4
Tasks
The first task of the COST Action 325 Technical sub-committee was the preparation of the
Memorandum of Understanding (MoU) for the implementation of a European research action on road
monitoring. On obtaining the required approvals for the MoU a management committee was formed to
oversee the COST Action 325 activities.
The management committee formed three working groups to carry out the work defined by the
methodology above. One group worked on surface distress assessment; the second on bearing capacity
measurement and the third on the preparation of the COST Action 325 report. Overall consistency of
approach by the working groups was controlled through meetings of the management committee.
Activities undertaken in the study are shown in Table 1 and are cross-referenced, to the tasks defined in
Annex II of the MoU. Table 1 shows that all of the objectives defined in the MoU were addressed in
the study. In Task 1 information was collected by means of a questionnaire on the practices and needs
of those engaged in the management of road network maintenance in Europe. Tasks 2 and 3 provided
state of the art information on research and developments in the field of high-speed equipment and
methods for the assessment of surface distress and load bearing capacity. In Task 4 the results from
previous tasks were synthesised to establish realistic terms of reference for improved high-speed
measuring equipment and methods that would be compatible with user needs while also being safe and
economic to operate. Task 4 also examined the implications of the report's recommendations for the
management of the road network and for research organisations, industry and network managers
involved in this activity. Task 5 was concerned with the production of the final report incorporating the
findingsfromTasks 2,3 and 4.
12
Dissemination ofinformation from the work of COST Action 325 was ongoing over the period of the
study, including for example, the preparation and distribution of a publicity leaflet and participation in
the COST Congress in Basle. Priority is being given to the dissemination of the final COST Action
325 Report via the Internet while hard copies were sent to targeted people in government, industry and
research organisations.
The work was carried out over a period of 2.5 years and the schedule of the COST activities is shown
in Table 2 including the final seminar held on 5th May 1997.
Technical and impact evaluations of the COST Action 325 study will use information collected from
active members of COST Action 325 and from those who have received information on COST Action
325 activities by attendance at conferences, or through reading the final report in hardcopy or on the
Internet.
The schedule of meetings held in the course of the COST Action 325 study is shown in Table 2
together with those projected for the evaluation exercise.
13
TABLE 1 - TASKS
MoU Annex II
Tasks Reference
TASKl
TASK 2
Working Group
Surface distress and
pavement management
Bearing capacity
Management Committee
Surface distress and
pavement management
Activity
Preparation of sub-questionnaire to obtain information on surface distress assessment and use
of pavement management systems (PMS)
Preparation of sub-questionnaire to obtain information on bearing capacity assessment
Integration of sub-questionnaire into a single questionnaire and distribution to selected road
authorities, research institutions and industries within and outside COST member countries.
Preparation of reports on road monitoring practice in COST member countries
Analysis of responses from questionnaire survey
Preparation of state of the art (SoA) paper on surface distress
Synthesis of SoA and analyses of needsfromquestionnaire to define performance
requirements for a surface distress assessment system within the context of PMS
Analysis of responses from questionnaire survey
TASK 3
TASK 4
Bearing capacity
Management Committee
Final Report
TASK 5
Management Committee
Preparation of SoA paper on bearing capacity
Synthesis of SoA and analyses of needsfromquestionnaire to define performance
requirements for a bearing capacity system
Synthesis of work from both working groups to produce recommendations for future implications of recommendations for network management and for organisations involved in
this management activity
Drafting of study report
Editing and production of final study report
Acceptance of report and delivery of report to E.C.
Dissemination of study resul Is
Table 2 - Schedule of activities
ACTIVITY
Preparation of MoU
Task 1: Information gathering
1.1 Questionnaire design
1.2 Road Monitoring practice
Task 2: Surface distress
2.1 Questionnaire analysis
2.2 R&D analysis
2.3 Synthesis
Task 3: Bearing capacity
3.1 Questionnaire analysis
3.2 R&D analysis
3.3 Synthesis
Task 4: Global synthesis and
network management
Task 5: Reports
5.1 Preparation
Dissemination
Poster/Basle congress
Leaflet
Internet
Seminar
Evaluations
Technical evaluation
Impact evaluation
Meetings
A=
Technical sub-committee
Management committee
X=
Working group
16
CHAPTER 3
INFORMATION GATHERING
3.1
Source of Information
In order to present the latest information on visual distress and bearing capacity assessment systems,
information has been collected from the following sources:
•
•
•
•
knowledge of COST Action 325 members;
papers, publications etc.;
state of practice reports from the COST Action 325 member countries;
questionnaire survey responses.
The members of COST Action 325 are experts in the field of road monitoring and road maintenance.
Their knowledge is used together with the information that was found in technical magazines and
publications. Other information was gathered from conferences, seminars and workshops.
The most relevant papers and publications, gathered from the above-mentioned sources, are listed in
the Bibliography and References of chapters 4, 5, 6 and 7 respectively.
In the state of practice reports provided by the members of the COST Action 325 Management
Committee, a description is given of the use (and development) of monitoring equipment for surface
distress and bearing capacity in most of the participating countries. Information from road authorities,
research institutes and industry (consultancies) has been obtained from responses to a questionnaire
survey. The state of practice reports as well as the questionnaire are further explained in sections 3.2
and 3.3.
3.2
State-of-Practice at National Level
Though the proposed questionnaire survey would provide much useful information on condition
assessment methods and needs it was recognised that it would provide little technical information on
the survey equipment in use in different countries. It was therefore thought that the questionnaire
exercise needed to be supplemented by more detailed information on the state-of-practice regarding
methods and equipment for road condition data acquisition. Ideally such state-of-practice reports would
be collected from all European countries. It was thought, however, that the methods and equipment
utilised in the countries participating in the COST Action 325 Management Committee could be
regarded as representative of the present state-of-practice and that it was unlikely that any significant
method or equipment for road data acquisition work would pass undetected. Only the members of the
Management Committee were therefore requested to provide reports covering the state-of-practice in
their own countries.
Belgium, Denmark, France, Germany, Greece, Italy, the Netherlands, Portugal, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom provided state-of-practice reports.
Information regarding type of measuring device, method of raw data processing, accuracy of recorded
data, operating speed, data acquisition cost and any new development was requested. It was suggested
that the state-of-practice reports should focus on monitoring methods and equipment mainly for the
measurement of road bearing capacity and the detection of road surface distress. However, as
information on other surface characteristics, such as skid resistance, unevenness and rutting and their
17
change over time, also are important aspects of road condition, descriptions of devices and methods for
collection of this type of data would be covered in the reports as well. The state-of-practice reports
provided by the countries listed above are included in Appendix 8.2.
3.3
Questionnaire Overview
3.3.1
Introduction
Information on current practices and needs of road monitoring has been collected through a
questionnaire exercise. The questionnaire was designed to collect data on ways to monitor surface
distress and to assess bearing capacity. Additional information was requested on the identification of
the agency questioned and on the function and extent of the network concerned. The opportunity was
also taken to include in the questionnaire a part related to the use of pavement management systems.
The questionnaire was addressed to central and local road authorities, to industry (for example,
consultancies and engineering firms) and to research institutes. (See Appendix 8.4). A majority of the
countries questioned belong to the E.U., others werefromCentral and Eastern Europe.
The analysis of the responses was carried out by two working groups responsible for :
•
•
Surface distress collection and pavement management systems, and
Bearing capacity measurements.
The results are presented and discussed in Chapters 4, 5 and 6 for surface distress, bearing capacity and
pavement management respectively.
3.3.2
Participating agencies and countries
A list of potential candidates was established and the questionnaire sent to them. This list is given in
Appendix 8.4.
Twenty-one countries responded, and the number of returns from each country was as follows:
Austria (3), Belgium (3), Bulgaria (2), Czech Rep.(l), Denmark (4), Finland (1), France (2), Germany
(1), Greece (1), Hungary (1), Italy (1), Latvia (1), Netherlands (7), Portugal (1), Romania (1), Slovenia
(2), Spain (2), Sweden (6), Switzerland (1), United Kingdom (2), Ukraine (1).
The distribution of responses by institution was:
Central Road Authorities (31%), Local Road Authorities (17%), Industry (17%), Research Institutes
(35%).
An exercise was carried out to analyse whether the responses were representative. The total number of
returns was considered satisfactory and the countries and organisations were sufficient to give a
representative picture.
18
3.3.3
Questionnaire outline
The aim of the questionnaire was to provide information that can contribute to :
•
•
•
an overview of existing practice and an analysis of needs;
set the requirements for specialised measurement equipment;
make recommendations for future systems.
The structure and content of the questionnaire is outlined below. The full questionnaire is presented in
Appendix 8.3.
The questionnaire is divided into three parts:
Part I. Surface Distress Data Collection
Part II. Bearing Capacity Measurement
Part III. Pavement Management Systems
A page of general questions precedes Part I. Responses to the questions posed were requested in the
following formats:
logical (yes/no);
multiple choice ticking;
multiple choice ranking;
numerical (engineering units, unit costs);
text (descriptions, comments).
The statistics of the questionnaire responses were summarised on a spreadsheet.
3.3.4
General
This section requests the identification of the organisation providing the answers. It also asks for a
detailed description of the road network taken into consideration by the organisation: including length,
road category and construction type.
Part I. SURFACE DISTRESS DATA COLLECTION
1.1. General
This item concerns the present status and reasons for collecting or not collecting surface distress data at
network level.
1.2. Methods of collecting surface distress data
Three options are presented : manual (pure visual),
image capturing with manual processing,
image capturing with automated processing.
19
In each case details are requested on the survey procedures, the surface distress detection technique, the
recording media, the processing, the reference used for distress recognition and the safety measures
employed.
Procedures are further detailed into the means of monitoring (continuous or sampling modes).
Processing looks at whether it is done in real time or post-processed. The method used for analysing the
image data is also requested (pattern recognition, or laser data interpretation).
1.3. Quality Assurance
Inquires on the degree of implementation of quality assurance procedures.
1.4. Methods in use
The question is put in the form of tables. The first table shows the distress types, their units of
evaluation and the scales of severity used. The second table states the quality of measurement per
distress type. The third table asks for a description of the performance of the distress collection method
used (capacities, costs, road safety, traffic disturbance).
1.5. Needs in the field of acquisition of surface distress data
A table is provided to describe the needs or required improvements regarding the acquisition of data
per type of surface distress or in relation to capacity, costs, and traffic disturbance.
1.6. Processing surface distress data
This group of questions relates to the pre-processing or interpretation of surface distress data, (use of
weighting factors, indices, homogeneous section determination, display of results).
1.7. New developments
This question seeks information on any new development in the field of automated systems for the
collection of distress data.
Part II. BEARING CAPACITY MEASUREMENTS
II. 1. Aim of bearing capacity measurements
This section is interested in determining the type of road network which is monitored together with the
purpose of the measurements.
II.2. Methods for evaluating the bearing capacity of roads
The questions relate to the type of device used, the measurement procedures (e.g. locations: wheel
tracks,...; and modes: continuous, or sampling), the way bearing capacity is evaluated from the
measurements (residual life, reinforcement thickness,...), and other parameters calculated. Provision is
made for those who do not use bearing capacity measurements.
20
11.3. Measurements with Benkelman or FWD
Information on location of measurements and traffic safety precautions are requested.
11.4. Measurements with Lacroix, Curviameter or other similar devices
Questions were asked on site selection, homogeneity criteria, operational speed, and safety precautions.
11.5. Measurements with other types of deflection meters
The questions are similar in II.3 and II.4.
11.6. Quality assurance
Questions were asked on implementation of quality assurance with respect to bearing capacity
measurements andfrequencyof calibrations.
11.7. Performance of methods in use
A table is set for information on performance aspects of the bearing capacity measurement method
used (load standards, repeatability, capacity, unit cost, road safety precautions, traffic disturbance,
frequency of measurements).
11.8. Needs in thefieldof acquisition of bearing capacity data
Questions were asked re the need for different performance criteria on accuracy, repeatability, capacity,
costs and traffic disturbance.
11.9. Treatment of data
Details are asked concerning the possible use of deflection measurements in combination with surface
distress data, the determination of uniform (homogeneous) road sections, and the form in which the
data are presented.
ILIO. New developments
Questions were asked on new developments under way in the field of deflection measurements.
Part III. PAVEMENT MANAGEMENT SYSTEMS
HI. 1. Involvement with a PMS
If the agency does not have a PMS it is requested to give the reason, either selected from a multiplechoice list or for some other specific reason, and to give an indication of intentions in this area.
21
111.2. Purpose for using a PMS
The questionnaire requests reasons for using a PMS. A list of reasons is provided which should be
ranked in order of importance.
111.3. Road surface characteristics used in the PMS
A table is included for describing which pavement condition parameters are used on different
categories of network and the proportion of the road network monitored each year for each parameter.
3.3.5
Summary
The questionnaire was designed to provide in one survey, information on surface distress data
collection and bearing capacity measurements. It was designed to obtain information on the' interests of
different authorities and institutions. A section devoted to Pavement Management Systems was added
to give an insight into the involvement of data collection procedures in the maintenance decision
processes and also on the extent of road network that might be concerned in condition monitoring. Care
has been taken to assess present practices particularly methods and performances, and to identify needs
for improvement.
22
CHAPTER 4
SURFACE DISTRESS
This chapter first gives a description of the existing assessment methods and systems and provides
information on systems under development. Secondly it describes the current practice in the assessment
of surface distress as provided by the analysis of the questionnaire responses. Based on this
information, requirements for future surface distress assessment systems are defined. Finally,
recommendations are given for the improvement, development and realisation of new high-speed data
collection methods and systems.
4.1
State-of-the-art Road Surface Distress Assessment
4.1.1
Introduction
Sub-chapter 4.1 reviews available systems and ongoing developments aimed at improving the methods
of assessing surface distress. It first examines the different types of surface distress that occur on roads
and identifies those which at present are difficult to quantify using existing road monitoring techniques.
Possible methods of measuring these defects are reviewed and assessment systems based on these
methods that have or are being developed are described. The advantages and disadvantages of the
different assessment systems are discussed and the most promising techniques for future development
are identified.
4.1.2
Surface Distress
Road surfaces are designed and maintained in a cost-effective way, to provide acceptable levels of
safety and riding quality for road users and to preserve the structural integrity of the pavement.
Poor skid resistance, low levels of macrotexture and wheel track rutting are the surface parameters
considered to be of most importance for road safety. Longitudinal unevenness is the dominant surface
characteristic influencing riding quality. Deterioration of these surface condition parameters correlates
broadly with cumulative traffic loading. This has encouraged the development of equipment and
methods for the measurement of these parameters. Over the past twenty years developments in sensing
and computer technologies have led to the production of a range of high-speed survey equipment for
the routine measurement of these surface characteristics. A comprehensive inventory of these
equipment is given in the PIARC Report "Inventory of Road Surface Characteristics Measuring
Equipment", published in 1995.
In contrast to the safety and ride aspects mentioned above, the development of road surface distress is
due as much to the action of climate as to traffic loading. The onset of surface distress is therefore less
predictable than is deterioration in road safety and ride characteristics. Nonetheless surface distress
information is widely used to prioritise the allocation of maintenance resources to roads showing other
forms of deterioration. As a consequence highway authorities are showing increasing interest in the
development of methods for assessing surface distress that are faster and more objective than the
traditional visual inspection approach.
For the purpose of this review paper, surface distress is defined to include the defects shown in the
following table.
23
Classifications of surface distress types
Definition
Surface distress type
Longitudinal cracks
Cracks which follow a course approximately parallel to the
centre line of the pavement. These cracks are mostly situated
at or near the centre of the wheel tracks.
Transverse cracks
Cracks that follow a course approximately atrightangles to
the pavement centre line.
Alligator cracks
Cracks that form a network of multi-sided blocks (resembling
the skin of an alligator). The block size can rangefroma few
centimetres to about a metre.
Edge cracks
Crack that is parallel to and within 30 cm of the pavement
edge and is either a fairly continuous straight crack or consists
of crescent-shaped cracks.
Ravelling
Loss of pavement material from the surface.
Bleeding
The presence of free asphalt binder on the surface resulting
from upward migration of the binder. Most likely to occur in
the wheel tracks during hot weather.
Pot holes
Holes in pavement surface, mostly related to cracking or
ravelling.
Maintenance/repairs
Small-scale repairs of surface distress, like surface treatments,
patching, crack sealing and inlay.
It is the objective of much ongoing research to develop safer and more economic methods of assessing
these surface defects in particular surface cracking.
4.1.3
Assessment Methods
A number of approaches to the measurement and assessment of surface distress are in routine use or are
under development including:•
•
Visual inspection
Optical systems using:
-
•
film and video techniques
image processing techniques
holographic process
laser range finding techniques
Infrared systems
24
•
•
Radar (Ground penetrating)
Acoustic systems.
Visual inspection is widely used to monitor surface defects in both developing and developed
countries. Though slow, and subjective in its assessment, visual inspection permits all of the defects
listed above to be collected in one pass by a road inspector who may also use a programmed portable
computer to record defect information and to transmit this information to a central database via a
telephone link.
Portable computer for recording surface defects
Optical imaging approaches are increasingly used to collect information on surface cracking but
analysis of the images, to quantify crack dimensions, is still a slow process. Laser range finding
techniques can measure surface profile at discrete sampling points along the surface using a number of
laser sensors; the absence or presence of cracks may be inferred from an analysis of the profiles
provided by two or more sensors. Radar technology offers the potential of not only detecting surface
defects but also subsurface cracks and voids. Acoustic systems appear to lack sufficient resolution to
be effective in crack assessment.
25
In the following section details of systems employing these different approaches are presented together
with their status and operating characteristics where available.
4.1.4
Assessment Systems
Though visual inspection of road surface continues to be widely used the subjective assessment of
defects introduces significant variability into the evaluation of pavement condition. Optical, infrared
and Radar based survey methods offer the potential of a more objective evaluation of condition and the
basic elements of these latter systems are briefly summarised below; system acronyms and technical
terms are defined in Appendix 8.5.
4.1.4.1 Photographic systems
The PASCO ROADRECON and GERPHO equipment, developed in Japan and France respectively,
were amongst the earliest road surveying systems that employed film to record road surface defects.
Both pieces of equipment record surface defects using a camera mounted on a boom overhanging the
front of the survey vehicle and looking straight down at the road surface. Surveys are made at night, at
speeds up to 80 km/hour, using lane wide illumination of the surface provided by a string of lights
attached to the bumper of the survey vehicle. Film speed in the camera is synchronised with survey
vehicle speed and the light intensity is adjusted to provide a continuous uniformly exposed film of the
surface of the traffic lane.
The ROADRECON photographic images and the 35 mm film produced by GERPHO are analysed
manually at a cine workstation and cracks down to 1 mm width can be resolved on the film. The
35mm Gerpho film can also be scanned by a video camera to create a digital image that is processed by
the MACADAM image analysis system. Cracks of width down to 3 mm can be resolved using this
system but its performance deteriorates with increase in the levels of macrotexture. Manual processing
is required to quantify fine cracks.
Both of these systems can provide good quality images over the full width of a road lane provided the
road surface is dry and relatively clean.
Other ongoing development work, based on the use of film to record surface distress, includes the
ADAPT project in the United States. The approach being adopted in this project involves the
application of digital signal processing techniques to the analysis of digitised surface distress film data
with the aim of detecting and quantifying different types of surface distress. The project is due for
completion in 1996.
4.1.4.2 Video systems
Video technology is currently employed in a range of road monitoring equipment to collect images of
road surface distress for later analysis either manually or automatically. The manually analysed data
collection systems are referred to as video logging systems. Examples of videologging equipment
includes the Connecticut PHOTOLOG, PAVETECH, and the Transport Research Laboratory's HSV.
26
In these systems one or more video cameras (shutter speed one thousandth of a second) is used to
collect surface ¡mages of half, or more, of a lane width at speeds up to 90 km/hour. The collected
images are stored on one or more video recorders together with location information for later
processing offline at a video workstation.
In general, the performance of videologging systems, in terms of resolving narrow cracks across the
width of a traffic lane, is improved by:
•
•
•
•
the use of two or four cameras to cover the width of a traffic lane
mounting the cameras such that they look down on the surface
increasing the camera shutter speed
ensuring the surface is uniformly illuminated during the image collection phase.
The main disadvantage of these systems is the need for manual analysis of the collected images which
is operator dependent, time consuming and expensive. Since the late 1980s the development of
automated video surveying systems has accelerated due to major advances in optical and computer
technology. These technical advances have provided improved image collection systems and faster
image processing times and the pace of development shows no sign of slackening. Consequently, it is
only possible to provide a "snapshot" of available systems and ongoing developments that may well be
superseded in a few years time.
ARIA, PAVUE and ARAN are examples of available video surveying systems that incorporate
automated ¡mage processing. ARIA is a fully automated system that can analyse images, sampled at 8
to 10 metre intervals, in real time. ARIA employs two cameras, one at the front and one at the rear of
the survey vehicle, mounted so that they face down towards the pavement surface to collect surface
¡mages (2m χ 1 m). These images are analysed to produce binarised crack maps. If a continuous
assessment of surface distress along a road is required then the image analysis is carried out, off line,
with the video tape containing the images played back at a slow speed.
PAVUE developed in the United States consists of four video cameras facing downwards, each
connected to a video recorder. With a horizontal bandwidth of 400 pixels for each recorder there are in
total 2000 pixels covering a road width of 3,2 to 4,0 m. E ach pixel thus covers 1,6 to 2,0 mm which
equals the resolution of the system. The PAVUE system collects shadow free images using computer
controlled strobe lighting. Standard cameras with a shutter time of 1/10000s are used, allowing
measurement speeds up to and including 90 km/h. The final video images are converted in a laboratory
to a continuous filmstrip of road surface information, i.e. not divided in separate frames. This is
important for the subsequent automatic image analysis as a crack otherwise could appear in two
consecutiveframesand thus be counted twice.
The ARAN is a fully automated system that uses two video cameras, and synchronised strobe lighting
mounted at the rear of a van, to record pavement ¡mages (lm χ 4m) onto video tape while the van is
operating at speeds up to 80 km/hour. The collected images, together with computer­recorded distance
and rating information, are processed using the image analysis software, WiseCrax. WiseCrax can be
operated in automatic or interactive mode and is capable of detecting
crack widths down to 2mm.
27
Automated crack detection
system called WiseCrax (Roadware)
Off line processing of
video recordings using
image processing
o
-OuO-
w.
l l l l l l l l l l l I I II I I I I I I I I I II I I I I I I I I I I I I I
' -J ·
—r-i-
50
Lane length (m)
'Crack Map's are produced showing crack type
density, severity, orentation and location.
Some of the ambiguities associated with the detection of cracks may be absent from the HYBRID
system developed in Sweden. It uses a combination of four video cameras and four distance measuring
laser sensors to automatically detect and confirm the presence of a crack. The laser distance
measurements are recorded on a personal computer. It uses online video image analysis before
combining the video and laser sensor data to generate pavement cracking reports. Trials of the
prototype HYBRID system suggest that it can detect cracks of width down to 2.5mm across a 2 metre
lane width at operating speeds up to 90 km/hour. As with the PAVUE system video images are
converted to a continuous filmstrip. The HYBRID uses data from the laser sensors to confirm, or
otherwise, that a crack detected on a video image is real.
Other ongoing development work in the Netherlands and in the United Kingdom is aimed at improving
the quality of images collected using video technology and at reducing the time taken to process
images. Investigations, at the Transport Research Laboratory (TRL) in the UK, into the use of linescan
cameras and better surface illumination has provided much improved images of cracks on surfaces with
coarse texture. In addition, research at the University of Birmingham has shown that the application of
parallel processing techniques to the analysis of video images significantly reduces image processing
times. Work is continuing at both Birmingham and TRL to further improve crack detection on coarsely
28
textured surfaces and to reduce processing times through more refined image processing algorithms
and improved design of the processing software.
4.1.4.3 Holographic system
A novel crack detection system, CREHOS has been developed in Switzerland. The system employs a
focused laser beam to scan the surface laterally to a width of 4 metres - the longitudinal surface scan is
provided by the movement of the survey vehicle. The back-scattered laser light is collected using a
multi-facet holographic light collector. When the light spot falls on a crack, light energy is absorbed
and the intensity of the light signal detected on the collector sharply decreases. This signal is filtered
and binarised to give sets of binary pulses representing the cracks. A custom parallel processor
recognises, processes and stores the sets of binary pulses representing cracks.
A prototype has been constructed and the limited trials carried out to date indicate that it has the
potential to detect cracks down to a width of 1 mm over a surface width of 4 metres at surveying speeds
in the range 40 to 120 km/hour. The project to develop the system was halted in 1995.
4.1.4.4 Infrared systems
Though the principle of crack detection by infrared systems is broadly similar to that of optical systems
they have received less attention. Infrared systems employ thermal cameras to detect small temperature
differences between cracks and the surrounding road surface material. Image processing analysis,
similar to that applied to visual ¡mages, can be used to automatically identify and extract crack
information. The technique has the advantage of being less sensitive to macrotexture than visual image
systems. However their performance is affected by climate and is poor on wet surfaces. Temperature
gradients in the vicinity of cracks causes broadening of the crack image but this positive aspect is offset
by the limited resolution of thermal cameras. This limitation means that a large number of cameras
would be required to provide an acceptable level of resolution over the width of a traffic lane which in
turn has cost implications.
4.1.4.5 Radar systems
Research carried out at the TRL has shown that ground probing radar can be used to detect surface and
sub-surface cracking. However the dipole antennae required for this application only works effectively
when in close proximity to the road surface. This limits its speed of operation to less than 5 km/hour
because of the risk of antennae damage. In addition the processing and analysis of the radar signals is
not as yet an automatic process and requires input from experts for the interpretation of analysis results.
The future role of radar systems in the field of crack detection is therefore likely to be confined to those
sections of deteriorated road where a detailed engineering investigation is required prior to the design
of appropriate maintenance.
4.1.4.6 Acoustic systems
Ultrasonic sensors have been successfully applied in the United Kingdom and the United States to the
measurement of wheel track rutting at survey speeds up to 80 km/hour. Investigations have been made
in Italy into the use of microphonic pick-up systems for the characterisation of road macrotexture and
for the detection of surface cracking from the sound produced by the tyre slap of the survey vehicle on
29
which the system is mounted. The indications from this work suggest that acoustic systems are not
effective in quantifying crack parameters.
Though the sensor technology is inexpensive it has the major disadvantage of poor resolution and low
accuracy in the assessment of cracking due to the relatively large "footprint" of the sonar signal on a
pavement surface. This severely limits its capability in the detection and delineation of individual
cracks.
It may however have some potential, when used in combination with video technology, as an economic
means of detecting surfaces with cracking for more detailed assessment using the slower video image
processing systems. As cracking on most designed pavement is confined to less than 20 per cent of the
pavement length the use of an inexpensive sift system (such as an acoustic sensor) to distinguish
cracked from crack free pavement surfaces would greatly reduce image data storage and the time
required to carry out the more sophisticated, and expensive, video image processing and analysis.
4.1.5
Discussion
The foregoing review indicates that in the assessment of surface distress most of the technical work has
been focused on the development of automated systems for the detection and classification of pavement
cracking. The review shows that for crack detection the most favoured technology is based on optoelectronic systems for the collection of surface image data and on image processing algorithms for the
extraction of crack information from these images. In addition, technical developments in the field of
opto-electronic systems have made rapid progress in recent years and existing crack survey systems are
evolving continuously as new and improved technologies become available.
Because of the continuous evolution of this technology, few evaluations have been made of the
performance of available systems or in the development of criteria against which system performance
could be assessed. There is a need for performance criteria to be developed that would pennit an
evaluation of existing and new surface distress assessment systems.
One of the few evaluations reported is that carried out in 1994 in the United States by the North
Carolina Department of Transportation in conjunction with the Federal Highway Administration of the
US Department of Transportation. In this study three fully automated systems, PAVUE, ARIA and
ARAN and two manually assisted systems, ROADRECON and PAVETECH, were tested and
evaluated on a number of flexible and rigid test pavements with surface distress levels ranging from
low to high severity. In the absence of any standard method of evaluating performance the quality of
the surface distress data collected by the different systems was assessed using the repeatability and
accuracy of distress assessment. The accuracy of the systems was assessed relative to detailed visual
inspections carried out manually using the SHRP Identification Manual which defined severity of
distress for SHRP's Long Term Pavement Performance (LTPP) Project.
The coefficient of variation of the repeat surveys carried out by each system on each test section was
used to define repeatability. For the purpose of the repeatability analyses, coefficients of variation less
than 20 per cent were considered 'reasonable'. Overall, 85 per cent of the repeat surveys were found to
give coefficients of variation of less than 20 per cent. The accuracy analysis, which was based on the
correlation between system and LTPP manual assessment of the total quantity of each classification of
crack, provided less clear cut results. This was due in part to the variation between systems in their
classification of cracks. In general the results varied for each system between test sections and no
system had a consistently better fit to the manual assessments over all sections.
30
Though the evaluation exercise showed that there is scope for further system improvement, progress is
being made in the development of reliable automated crack assessment systems. In particular the
hybrid video and laser ranging systems appear to provide a means of reducing errors associated with
the mistaken identification of shadows for cracks. However further research and development is
required to overcome some of the shortcomings of existing ¡mage processing systems, in particular,
low processing speeds and the difficulty of detecting cracks on surfaces with coarse macrotexture.
The automatic identification and processing of images of other surface defects, such as material loss
and edge deterioration, can use the same technology, as that used for cracks for the collection of
surface images. However new assessment criteria are needed to allow the extraction of information on
these other defects from the image data.
4.1.6
Conclusions
A review of the technologies available and under development for the assessment of road surface
distress, in particular cracking, shows that the most promising developments are based on the use of
video technology allied to high­powered computer processing of the video images.
Ongoing work on improved systems of illuminating pavement surfaces should further enhance the
quality of the surface ¡mages, which in turn will improve the effectiveness of the image processing
techniques in the extracting of defect information.
For the detection of surface defects, other than cracking, new assessment criteria need to be developed.
4.1.7
Bibliography
1. PIARC Technical Committee on Road Surface characteristics:
characteristics measuring equipment. Paris 1995.
Inventory of road surface
2. State of Practice reports from the member countries of the COST Action 325 Management
Committee ­ see Appendix 8.2.
3. Technical papers:
ARIA (1990). Automatic Road Image Analyser. MHM Associates Incorporated, 1920 Rigedale Road,
South Bens, Indiana 46614, USA.
COPP Ρ E (1989). Field test of three video recognition systems. California Department of
Transportation, Automated Pavement Distress Data Recognition Seminar, Ames, Iowa ­ June 15, 1989.
31
GERPHO (1975). Photographic road survey group, high yield apparatus. LCPC. 56 Boulevard
Lefebvre, 75732 Paris, Cedex 15.
HSV (1990). High Speed Survey Vehicle. TRRL Leaflet 26/9/1990. Department of Transport, TRRL
Pavement Engineering Division, Transport and Road Research Laboratory, Crowthorne.
MONTI M (1994). CREHOS: A large laser scanner with holographic detection for real time
recognition of cracks in road pavements. Swiss Federal Institute of Technology. Lausanne.
Switzerland.
PASCO ROADRECON (1970).
Meguro-ku, Tokyo 153, Japan.
Pacific Aero Survey Company Limited. 2-13-5 Higashiyama,
PAVEDEX (1990). The Videometric Data Acquisition and Computer Image Processing System.
Pavedex Incorporated. E 9514 Montgomery Avenue, Suite 26, Spokane, WA 99206. USA.
PAVETECH VIV (1990). Video Inspection Vehicle. Pavement Technology Incorporated. 516 West
California, Suite 103, Oklahoma City, Oklahoma 73102, USA.
PHOTOLOG (1989).
Connecticut, USA.
Connecticut Department of Transportation, 280 West Street Rocky Hill.
MENDELSOHN, D H (1989). Automated pavement crack detection: an assessment of leading
technologies. Contract No. DTFH61-84-C-00077, Federal Highway Administration. Washington,
USA.
TILLOTSON, Η Τ et al. (1996). A modular road condition data collection system for low cost roads.
Journal of the Institution of Highways and Transportation (February 1996), London, UK.
ROAD PROFILER USER GROUP (1995). North Carolina (USA) - test and evaluation of automated
distress survey equipment. 7th Annual Meeting, Orlando, Florida, (October 3-5 1995). North Carolina
Department of Transportation and US Department of Transportation, Federal Highways
Administration, Washington, USA.
NCHRP - IDEA Project 12 (1995). Advanced testing of an automatic non-destructive evaluation
system for highway pavement surface condition assessment. (Professors S. Guralnick and E Suen.
Illinois Institute of Technology, Chicago, USA).
ADAPT (1995). Automated Distress Analysis for Pavement Program. LORAL Defence Systems Arizona, USA. (Interim Status Report October 1995 for Department of Transportation, Federal
Highways Administration, Washington, USA).
4.2
Outcome of Questionnaire
In this sub-chapter a description is given of the different ways that surface distress assessment systems
are used in Europe. Information is provided about the current problems and needs in the field of data
acquisition and processing. Also the purpose for which surface distress is assessed are mentioned as
well as the different ways the data are used. This information is based on the outcome of the COST
Action 325 questionnaire exercise.
32
For the presentation of the outcome of the questionnaire, two numbers are used:
Τ=
number of respondents, taking into account the total number of returned questionnaires.
A=
number of respondents limited to the answers from central or local road authorities.
This distinction is made because it is considered important to base the recommendations for improved
high-speed monitoring equipment especially on the problems and needs identified by central and local
road authorities.
In the reporting each answer is given together with the number of the corresponding question of Part I
of the questionnaire. The full text of the questionnaire is presented in Appendix 8.3. Information on the
design of the questionnaire and the total number of respondents is given in sub-chapter 3.3.
General (QU, 01.2. 01.3)
All 21 countries that responded to the questionnaire collect surface distress data. Only two respondents
(both from Sweden) do not collect data at network level. One of the two is not involved with network
management. The other respondent indicated that the reason for not collecting surface distress data on
roads at network level was that visual inspection is both "time consuming/expensive" and "subjecti­
ve/not reliable". However, he would choose to collect the data if the problems were solved. His answer
to the question on methods of collecting data suggests that the manual surveys are carried out at project
level only.
The three main reasons (considering answers by respondents and per road authority) for collecting
surface distress data are (Ql .4):
to determine a long term budget for road maintenance;
to determine a long term maintenance scheduling plan for roads;
to determine rehabilitation measures for sections of roads.
The other reasons are:
to predict the evolution of the network;
to follow up the efficiency of the maintenance policy;
for research;
other (safety).
All countries collect surface distress data, which shows that there is a definite need for such data. From
the three main reasons we may conclude that the data are especially used both for prioritising sections
of roads at network level according to road surface condition and for making a general assessment of
the type of rehabilitation measure that may be required. Prioritising sections of road is necessary
because available funds may limit the extent of works to be carried out or may influence the choice of
rehabilitation measures. The ratio of planned or executed works against those that are necessary (in
terms of kilometres of roads or funds) is a measure of the ability of the road authority to maintain the
road network in an adequate condition.
33
The ranking of the other reasons may suggest that:
•
•
predicting the evolution of the road network is not the main goal of collecting surface distress data.
However, it is obvious that predicting the condition of the road surface is necessary in order to be
able to determine long term budgeting and scheduling plans for road maintenance.
in some cases, although a prediction of deterioration may be made, the yearly funding may not be
constant nor sufficient to make a practical/viable estimate of future long- tenn expenditure.
Only a few road authorities follow up the efficiency of their maintenance policy or engage in research.
This suggests that there are probably only a few advanced Pavement Management Systems in use by
road authorities.
Methods of collecting data (Q2.1 )
Method
Manual (visual inspection)
Image capturing; manual processing
Image capturing; automated processing
40
16
24
10
Most of the respondents (40), representing all 21 countries, answered that surface distress data are
collected manually; 16 respondents from 10 countries use an image capturing/manual processing
technique (one exclusively, the other 15 in addition to the manual method). Four respondents (from
Greece, Romania, United Kingdom and Sweden) indicate that an image capturing/automated
processing technique is used in addition to the manual method. One respondent (from the Netherlands)
reported that automated processing would be used in the near future to replace manual processing. Two
respondents (from Sweden and the United Kingdom) use all three available methods for collecting
surface distress data.
From the completed questionnaires it was also noted that most of the Western European Countries use
road monitoring machines. Only a few Eastern European countries reported the use of monitoring
equipment.
Manual data collection is still very important. Fourteen respondents use more than one method of
surface distress data collection, which may suggest a possible ongoing transition from manual method
(visual survey) to an image capturing and manual or automated processing method. It seems that
Western European countries are in the middle of a transition to more automated systems. Eastern
European countries are however just beginning this transition process. There is obviously a need to
increase the speed and daily capacity of data collection. This is especially true for large networks,
where a reduction in time and personnel would significantly reduce the overall costs of data collection.
Traffic disruptions are also reduced and safety is consequently improved. The fact that 5 respondents
are developing and/or using image capturing and automated processing methods suggests that manual
processing is tedious and that there is a benefit to be gained from the development of automated
processing techniques. In addition, interpretation of data is less subjective. However, the existing fully
automated methods need to be developed further to include, among other things, capability to monitor
and process all distress parameters simultaneously.
34
Manual Visual Inspection
Continuous versus discontinuous surveys (Q2.2.1 )
Manual inspections are carried out as follows:
Continuous (the total road-length is surveyed)
Discontinuous (parts of the total road-length are surveyed)
Discontinuous (parts of the total road-length are surveyed)
Τ
21
17
1
A
14
9
0
In the case of discontinuous surveying, the following sampling methods are used (Q2.2.1.1):
Selective
Regular
Random
A
8
2
1
Τ
14
4
1
Four main reasons may have influenced survey practice; network length, network category, economic
resources and policy (standards).
Most road authorities use a selective approach for discontinuous surveys. This could have different
reasons:
•
•
•
The road authorities believe they have a good knowledge of their networks. They think they know
the "weak" sections.
There may be a certain policy or standard.
The approach may be based on a prediction model or statistics (probability).
Two road authorities take regular samples. This could also be based on a policy, a standard or a model.
However, regular sampling and random sampling may involve the risk of not covering the "weak"
sections and may therefore lead to maintenance and safety problems. Therefore it is likely that they
have some idea of where to find deterioration on their networks.
In any case, whether surveys are continuous or discontinuous, there is always the question of
frequency: i.e. when and how often to survey.
Way of carrying out visual inspections (Q2.2.2)
On Foot
In a car
Both on foot and in a car
Other
Τ
9
19
19
2
A
6
13
5
2
Visual inspections on foot are still quite common. The fact that 12 respondents use both possibilities
can be interpreted in different ways:
35
They may currently be in a transition phase.
It may depend on what kind of data is being inspected.
It may depend on the network level or type of road.
Some authorities in a country use a car, others go on foot.
Sòme road authorities have specific policies: after an inspection in a car one can detemiine from a
form, whether a visual inspection on foot is required for certain distress data.
Going on foot is a better method of collecting more detailed information, the choice will depend on
whether the information is needed for project level or network level assessment.
Registration of the data (Q2.2.3)
The following methods are used to register the data:
Paper form
(Portable) PC
Both
Other (tape recorder + PC)
Τ
13
14
12
2
A
10
9
5
2
All the countries use at least one of the methods. There is no indication whether the road authorities use
some kind of a standardised or paper form or computer program or whether they use the same forni on
paper and on PC. The fact that 12 respondents use both possibilities can be interpreted in different
ways:
They may currently be in a phase of transition.
It may depend on the network level or type of road.
Some authorities in a country use a paper form, others a PC.
It may depend on what kind of data is being inspected (e.g. sketches).
Data on paper may be fed into a PC through an interface or scanner.
Safety measures (Q2.2.4)
Number of respondents/road authorities that take safety measures during the visual inspections:
Yes
No
Undecided
Ί­
30
7
2
Α
18
5
1
Most respondents adopt safety measures, which is certainly good practice. However, safety measures
also have their drawbacks: interruption and/or disturbance of the traffic and the traffic flow. This has
not only economic consequences; it also has its own safety risks. There might be different reasons why
some road authorities take no safety measures during visual inspection and these include:
36
The network level or a specific road do not require safety measures.
Safety measures are too time consuming on network surveys.
Safety measures are too expensive.
Safety measures are not considered necessary (little traffic).
It is not possible due to traffic, environment (not enough room) or network structure.
Manual (Q2.2.5)
Number of respondents and road authorities that use a manual (surface distress catalogue) for
collecting surface distress data:
Yes
Undecided
Τ
34
2
A
21
1
The names of the manuals, quoted by respondents, are: CROW inspection method (Netherlands), VTI
modified (Sweden), SHRP (Romania, Finland), Skadekatalog Belman (Denmark), Swiss standard
(Switzerland) and National Distress Manual (Portugal, Bulgaria, Belgium, Spain).
A majority of the respondents use a manual. Distress catalogue to help make visual surveys a little less
subjective. They can also be useful to calculate distress indices. The results show that manuals are
rightfully believed to be important. For quality assurance purposes the use of some sort of manual is a
minimal requirement.
Not all the respondents stated the name of their manual. Sometimes, when there was more than one
questionnaire form from a country, not all the authorities answered this question. But it is reasonable to
assume that the authorities from one country would use the same manual.
Performance of the visual inspection
Quality of measurement per distress type (Q=4.2)
The number of respondents and road authorities, that stated, for each distress type, the quality of the
visual inspection (good, acceptable or bad), are shown in the table below:
Longitud, cracks
Transverse cracks
Alligator cracks
Ravelling
Pot holes
Bleeding
Other
good
17
17
15
14
19
14
8
All respondents
acceptable
bad
0
17
2
14
0
19
3
16
0
15
1
18
0
9
good
7
8
7
6
8
6
5
Road authorities
acceptable bad
12
0
9
1
12
0
10
3
11
0
11
1
4
0
"Good" and "acceptable" are the most common answers for all distress types, although it should be
noted that some respondents also gave the answer "bad". This is especially the case for ravelling. This
distress type is more difficult to assess by means of a visual inspection.
It can also be seen that road authorities are less satisfied with the results of a visual inspection than all
respondents. The reason might be that "all respondents" also include industry and consultancy
37
agencies. This group of respondents seems to be more satisfied with the quality of a visual inspection
than road authorities.
The fact that a majority of all respondents thinks that the visual inspection method performs
"acceptable" and that even a few respondents think that the performance is "bad" indicates very
strongly that there is need for improvement (in tenns of quality and in tenns of technical improvement).
Performance of the method in use (Q4.3)
In terms of capacity, costs, road safety and traffic disturbance the perfonnance of the visual inspection
methods is as follows:
Capacity (km/day)
Costs (ECU/km)
answers between 5 and 1 OOkm/day
answers between 10 and 150 ECU/km
All respondents
Road authorities
Road safety
good
moderate
bad
15
15
5
10
10
1
Traffic disturbance
none
little
much
8
23
4
8
15
1
The capacity varies widely. This certainly depends on how the inspection (on foot or in a car) is carried
out, but the length, travelling speed and amount of traffic on the network may also be important.
The costs also show large differences. Possible reasons for these differences include:
Inspection on foot or in a car;
Equipment that is used;
Economic differences (wages);
Number of people that are required for an inspection;
Length, travelling speed and volume of traffic on a network;
Scale of safety measures required or implemented.
The answers concerning road safety indicate that the methods in use are not considered to be high risk,
but it is also clear that there is some hazard. Most respondents implement safety measures, but most of
them still have problems.
Traffic disturbance, which in itself contains some safety risks, is considered a problem, at least to some
degree.
38
Image capturing
Method of recording (Q2.3.1 )
Techniques that are in use for recording surface distress:
Technique
Film
Video
Photo
Infra red light recording
Τ
5
14
2
1
A
3
9
2
1
Most of the respondents use video to record surface distress.
Although film has a higher resolution than video, it is not used very often. The probable reason is that
video equipment is more user friendly and is more accessible (direct play back on a video recorder). It
can also be used under day light conditions (most of the existing equipment with film operate at night
time condition with artificial light). Another reason for using video instead of film might be that it is
easier to develop an automated evaluation method for video-images than for a filmstrip.
Combined measuring techniques (Q2.3.2)
Number of respondents/road authorities that combine their image recordings with:
Laser
Ultra-sonic
Other
Τ
7
3
1
A
3
2
0
The following measurement systems are mentioned as additional infonnation to this question: Laser
RST, SIRANO, ARAN, and HSV.
The current systems do not combine the recordings with laser or sonar in order to detect surface
distresses. This could be helpful because it will add information about the texture of the pavement.
Deteriorated pavements have a variable texture.
Equipment in use (Q2.3.3)
Data acquisition systems (measurement systems), that are cunently in use are: ARAN, SIRANO, Laser
RST, HSV, ROMEO, CALAO and GERPHO. These systems are well known. Most of the systems are
multi-functional with combined measurement of surface distress, rut depth, roughness, texture etc.
Not all existing, well known, measurement systems are used in European countries: PASCO,
ROADRECON, ARIA.
Operating conditions (Q2.3.4)
All cunent video based data acquisition systems operate in daytime.
39
All cunent film based data acquisition systems operate at night-time.
All systems require dry surface conditions.
Night-time operations require the use of artificial light. Night-time conditions are however a
disadvantage due to unavailability of personnel and problems with road safety.
Continuity of recording and processing
The images of the road surface are recorded as fo lows (Q2.3.5):
Continuous
Discontinuous
Both
Τ
12
If recordings are made discontinuously, the following sampling methods are used:
Τ
A
Selective
2
3
Regular
1
1
Random
0
0
The recorded images are processed as follows (Q2.4.2):
Τ
A
Continuous
8
0
Discontinuous
6
2
Both
0
0
If recordings are processed discontinuously, the following sampling methods are used:
Τ
A
2
Selective
5
Regular
1
0
Random
0
0
Twelve of the sixteen respondents, who record surface distress on film or video, make continuous
recordings. However, only eight of these respondents process the recordings continuously.
If discontinuous recordings are made or processed, a selective sampling method is used in most of the
cases (75%) and a regular sampling method in 25% of the cases. Random sampling method is not
used.
It was noted that it is relatively inexpensive to make continuous recordings. Manual processing is
expensive (labour intensive). Therefore the total recorded road length is not processed in all cases.
Also that road authorities are more or less aware of deteriorated sections on their road network.
Therefore a selective sampling method can be used. In the case of discontinuous recording or
processing there is, however, a risk that some deteriorated road sections may not be
recorded/processed.
40
Manual versus automated processing
Recordings of surface distress on film or video are processed as follows (Q2.3.6):
Manual
Automated
Combined
Τ
11
4
2
A
7
3
1
A majority of respondents process their recordings manually. Four respondents process recordings in
an automatic way. However, a closer look at the description of the automated methods that are used
shows that none of the methods to be yet fully operational (systems are still under development or only
detect cracks). Therefore it is likely that in these cases automated methods are used in combination with
manual processing, in order to overcome the present shortcomings of the automated methods.
Methods of manual processing (Q2.4.1 )
Seven respondents gave a description of their method of manual processing. The described methods are
the same as that used in the visual inspection of a road. The film/video is played back frame by frame
while rating the extent and the severity of the distress types. Some respondents use a coarse method
with no distinction of severity levels in the assessment of the overall road surface condition.
The results of manual processing are recorded as follows:
On paper
Use of a keyboard
Τ
1
10
A
2
6
The cunent methods for the visual inspection/manual processing are too time consuming for use on
network level on a road network.
Performance of manual processing methods
Quality of measurement per distress type (Q4.2)
The number of respondents and road authorities, that stated for each distress type the quality of the
manual processing methods (good, bad or acceptable), are shown in the table below:
Longitud, cracks
Transverse cracks
Alligator cracks
Ravelling
Pot holes
Bleeding
Other
good
4
4
3
2
3
3
3
All respondents
acceptable
bad
5
2
5
1
5
3
5
4
7
1
6
1
4
0
41
good
2
2
Road authorities
acceptable
bad
2
1
2
0
1
2
1
3
3
1
2
1
1
0
A majority of respondents/road authorities believe that the quality of the assessment of surface distress
on film or video is good or acceptable. However, the results of the assessment of alligator cracks and
ravelling are not as good as the results of the other distress types: longitudinal cracks, transverse cracks,
pot holes, bleeding and other. It should also be mentioned that the overall quality of manual processing
of surface distress recorded on film or video is not as good as the quality of a visual inspection on foot.
It is conceivable that some of the surface distress, like fine cracks, are not very visible on film on
video.
Performance of the methods in use (Q4.3)
In terms of capacity, costs, road safety and traffic disturbance the perfonnance of the visual inspection
methods is as follows:
Capacity (km/day)
answers between 15 and 400km/day
Costs (ECU/km)
answers between 32 and 240 ECU/km
All respondents
Road authorities
Road safety
good
moderate
bad
10
0
0
5
0
0
Traffic disturbance
none
little
much
9
1
0
5
0
0
It was noted from the questionnaire that:
The mean capacity of manual processing is 176 km/day. There is, however, a large spread in the
answers: from 15 km/day up to 400 km/day.
The mean cost of manual processing is 106 ECU per km. Here also the spread in the answers is
substantial: from 32 ECU/km up to 240 ECU/km per lane.
All the countries that use ¡mage capturing appear not to have road safety problems and traffic
disturbance during measurements.
The capacity and the costs of manual processing are higher than the capacity and the costs of the
visual inspection: 176 versus 37 km/day and 106 versus 52 ECU/km.
Some respondents use coarse methods to process surface distress data on film or video. This might
be the reason for the high capacity of manual processing in some cases. It also explains the large
differences in the costs for manual processing.
Respondents who carry out visual inspections are less positive about road safety and traffic
disturbance during measurement than those who collect surface distress on film or video: only
40% (against 100%) of the respondents who carry out visual inspections state that road safety is
good and 21% (against 90%) state that they have no problems with traffic disturbance.
42
Automated processing
From the total of 44 respondents (representing 21 countries) only 7 respondents (from 6 countries)
answered the questions about automated methods for the collection and processing of surface distress
data. The most relevant answers are presented below.
The place of processing: (Q2.5.1 ):
In the vehicle
In the office
Both
Τ
3
3
1
A
3
1
0
The processing method: (Q2.5.2)
Image processing
Laser
Τ
3
4
A
2
2
Ways of processing: (Q2.5.3)
Continuous
Discontinuous
Τ
4
1
A
1
1
Two main methods are in use for the processing of the collected data. Four respondents report that they
use a laser interpretation method (from Sweden, Denmark, United Kingdom and Spain) and three
respondents (from Greece, Romania and United Kingdom) use ¡mage processing and pattern recogniti­
on. Three respondents process the data in the vehicle and three respondents process the data (images)
in the office. One respondent processes the data in the vehicle as well as in the office. As far as the way
of processing is concerned, four respondents use a continuous method and one respondent a
discontinuous method.
It is also reported that research is under way in order to improve the methods and equipment in use.
TRL and Birmingham University have research programmes in this field. The National Technical
University of Athens and the National Road Administration of Romania report that research is under
way. Also DWW from the Netherlands is developing image processing.
The small number of answers indicates that the automated processing of surface distress data is a new
method and has so far a limited application in the countries surveyed. The fact that automated
processing systems must have a capability of recording cracks on all kinds of road surfaces, including
surfaces with high texture values, indicates a need for more sophisticated techniques.
It is obvious that the wider use of automated methods would improve the efficiency of network surveys
but the need for expensive and sophisticated equipment and/or experienced personnel has resulted in a
low implementation rate to date. Research to improve the methods of automated processing is reported
by four organisations, although it is known that other institutes are also carrying out similar research.
43
Performance of automated processing
Quality of the measurements(04.1 )
Only. 3 respondents reported on the performance of the method. Two respondents report a good
performance of the method in use (image processing). One respondent is not satisfied with their laser
method due to a poor detection rate of longitudinal and transverse cracks, ravelling and bleeding and a
moderate detection of alligator cracks and potholes.
Capacity, costs and road safety (Q4.2 and 4.3)
One respondent reported that the capacity of the method in use is 400 km/day. No infonnation was
given concerning the costs of these methods. Two respondents reported that road safety was good to
moderate and that traffic disturbance was minimal when using automated systems for collecting surface
distress data.
Because of the small number of road authorities who reported on the perfonnance of automated
methods for the collection of surface distress data it is not possible to draw any general conclusions.
However, from the description of the road surface distress assessment systems (sub-chapter 4.1 ) we can
see that automated methods are still under development. This might be the reason why these methods
are still not used very often.
Quality Assurance (Q3)
Seventeen respondents (of whom 11 are road authorities) use a quality assurance procedure for the
assessment of surface distress data. For 15 respondents (of whom 9 are road authorities) the procedures
are applied to data collection and for 13 respondents (of whom 8 are road authorities) the procedures
are used on data processing.
Of all the respondents that collect surface distress data, only 40% use a procedure for quality assurance.
However, visual inspections (including manual processing of ¡mages) are very subjective. Quality
assurance procedures are important to overcome this problem.
Quality assurance procedures that are being used include random checking of results by a panel of
experts, periodical training, engineering judgement and comparison with historical data.
Needs in the field of acquisition of surface distress data (Q5)
Of those that responded to the questionnaire 51 % described their needs and 37% did not, but stated that
they have problems in collecting surface distress data (inaccurate data, traffic disturbance, poor road
safety, high costs, low capacity). The remaining 12% of the respondents do not have any problem nor
any needs. Most of the needs are related to the problems as reported under performance of the methods
in use. (Q4.2 and Q4.5)
The reported needs are listed below and are not listed in order of importance:
44
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
use video equipment
improve the accuracy of image capturing
use ¡mage capturing and automated processing
use automated processing
automated methods for reliable and continuous data collection
minimal traffic disturbance
improve quality of recording and automated crack identification
develop methods for automated processing of distresstypesother than cracks
automated data collection to increase capacity, to lower costs and to reduce traffic disturbance
accelerate implementation of PMSL equipment
improved lighting conditions to detect cracks
use of automated, high-speed data collection equipment at network level
more reliable and accurate surface distress data collection
use a less sophisticated method for data collection at network level
use of portable PC for recording visual inspection data
better resolution offinecracks
procedures for inspection at network level
No further needs
required accuracy for fine cracks, 0,5mm, to allow discrimination between thin and large cracks
required accuracy is 1 mm for crack-widths
Capacity (km/day): 30 to 200
Costs (ECU per km): 12,2 to 100
These needs can be grouped into the following concerns where the numbers in brackets refer to the
listed needs:
Concerns on equipment are expressed at the level of data capture (1,3, 10, 15).
Portable PC's should be available for logging visual inspection data(15). Video equipment (1) is
suggested for the permanent recording and also for batch processing of visual defects. A step further is
the replacement of visual inspection by automated processing (3). This raises two problems: what
transducer best fits the requirements for image capturing and what automated processing is appropriate
to quantify the surface defects in the captured ¡mages.
Processing data in an automated form, whether on line or off line, appears to be the major
preoccupation (4). Automated processing should not be restricted to assessing the extent and severity of
surface distress. It must provide reduced statistical data suitable for electronic transmission to the host
road condition database.
Procedures for carrying out distress monitoring will need to be tailored to the types of roads under
investigation. In particular inspections at network level (14, 17) will have to take into account the need
to aggregate statistically the condition data and to be able to define homogeneous zones.
Performance (costs and capacity) of monitoring methods (9, 12) are linked but not necessarily in a
proportional way. This is probably due to the increase in complexity of managing monitoring activities
as capacity increases. Increased capacity means that more sections of the network will be monitored.
45
Safety issues associated with the collection of distress data is indirectly mentioned: the procedure
should generate the least traffic disturbance (6) which in turn implies some type of recording for either
the visual or automatically processed data.
Accuracy and repeatability of the data collected should be established in order to provide the necessary
and sufficient quality (2,5,7, 13, and 16). This calls for the establishment of criteria defining classes of
quality satisfying different needs.
In the field of new developments contradictory statements have been formulated. On the one hand there
are needs for further developments (1 to 17). On the other hand no further needs are reported (18). This
is of course reflects the views of the different institutions who responded to the questionnaire survey.
The quantified needs (19, 20) can tentatively be translated into the problem of assessing the severity
factor associated with the extent of distresses. This question raises the opportunity for the justification
of quantifying the severity of distresses and its correlative measure in terms of scale and resolution.
The other quantified needs (21, 22) give an idea of what might be the ranges of capacity and cost of
collecting data. This question is important because it raises the issue of the affordability of carrying out
surface distress monitoring. The collection of distress data is required for pavement management and it
must be tailored according to a cost-benefit approach which assesses the benefits of accurate and
quantified condition data against the costs of data collection.
Processing surface distress data (Q6)
Surface distress data iareprocessed as follows:
Use weighting values
Calculation of distress indices for sections of road
Determination of homogeneous road sections
Τ
20
25
34
A
12
16
20
Homogeneous road sections are determined in terms of pavement distress (70% of the respondents),
traffic volumes (75%) and pavement construction (85%). Other, not so often used criteria for
homogenous road sections are deflection, unevenness, last year of maintenance, open or closed
drainage and type of surface.
Most of the countries (road authorities) collect road surface distress data at a detailed level, assessing
the extent and severity of each individual distress patterns. The data is then processed/aggregated to a
less detailed level (distress indices per homogenous road section) in order to produce long tenn
maintenance and budgeting plan on network level.
New developments (Q7)
The following new systems in the field of automated distress data collection were mentioned:
46
ROMEO
Laser RST
ARAN (WiseCrax)
PAVUE
ARIA
GERPHO/SIRANO
ROADRECON
TRL (prototype system)
University of Birmingham (prototype system)
Each of the mentioned developments, except the last two, relate to existing data acquisition systems.
These developments are also mentioned and further described in Chapter 4.1.
4.3
System Performance Requirements
4.3.1
Synthesis
From the outcome of the questionnaire it can be concluded that central as well as local road authorities
have problems and needs in the collection of surface distress data. The problems and needs can be
summarised as follows:
Most of the road authorities collect their surface distress data by means of visual inspections at site.
This method has several disadvantages:
unsafe for inspector and road user;
the data collection causes traffic disturbance;
the results are not reliable (subjective);
visual inspection is time consuming (survey capacity is low).
Quite a few road authorities collect at high-speed, images of the surface on film or video followed by a
visual inspection in the office. This method only solves some of the problems i.e. traffic disturbance
and road safety.
A few countries reported the use of automated systems, however they have limited accuracy and do not
detect all types of surface distress. Therefore, these systems have to be supported by visual methods.
As a consequence of the above mentioned problems, the following needs were expressed:
•
•
•
•
increase the reliability and accuracy of surface distress data collection;
increase the capacity and reduce the cost of data collection systems;
reduce/eliminate traffic disturbance and improve road safety;
collection of different types of cracking of different width, length and direction as well as other
types of distress such as ravelling and bleeding;
The review of the surface distress assessment methods in sub-chapter 4.1 made clear that, despite all
the efforts made by research institutes and industry, fully automated systems for the collection of
surface distress data have not yet been developed. The review also made clear that the developments of
new, promising measurement and processing techniques have made rapid progress in recent years.
Examples of these techniques are:
47
opto-electronic systems;
laser scanning techniques;
strobe-light;
image processing techniques;
computer techniques (increase of processing speed, parallel processing);
software developments (fuzzy logic/expert systems)
Most successful so far is the development of automated crack detection systems, based on image
processing technologies. However, these systems do not detect fine cracks (<2mm) or other surface
distress types, like ravelling and bleeding and further research and development is necessary.
To ensure that the developments will solve the above mentioned problems and fulfil all the listed needs,
requirements for the performance of automated systems have been defined. These requirements
describe terms of reference for future European research- and development-projects. Developers from
research institutes, universities and engineering companies involved in the development of high-speed
data collection devices will find here information about the required capabilities, capacity, accuracy,
repeatability, resolution and measurement speed.
The COST Action 325 Management Committee is aware that the development of automated systems
for distress data collection is very costly and time consuming. Nevertheless, the committee judges the
requirements to be realistic in terms of time and costs. With a good support, co-ordination and cooperation between research institutes, industry and road authorities it should be possible to realise an
affordable, fully automated data collection system within a period offiveto eight years.
For the purpose of this report, the requirements are defined for the collection of visual surface
distresses, like cracking and ravelling. Surface deformations like roughness and rutting are excluded.
Efficient high speed monitoring equipment for these defects are already available.
4.3.2. Requirements
In the following, the requirements are shown by the bullet points and the discussion is in italics.
Capabilities
For pavement management purposes, it is important to have information about the pavement condition
of the total road network. Not knowing where all the weak sections are may lead to maintenance and
safety problems. Therefore it is important to assess the condition of the road network in a complete an
reliable way. Information is needed of the extent and severity of all surface distress types on all types
pavement.
•
Distress types
The data collection equipment should be able to assess the following surface distress types:
cracks
ravelling, loss of surface materials;
48
bleeding (flushing);
potholes;
maintenance/repairs
•
•
•
•
•
Severity
It should be possible to classify the severity of the surface distress into three: low, moderate,
severe. The class boundaries must be adjustable.
Extent
It should be possible to use the following units for the registration for the extent of the distresses:
Cracks/- length, width and direction
Ravelling: m", %,/- area
Potholes:/- number
Bleeding: nr, %/- area
Pavement types
The data collection equipment should be able to detect the various surface distress types on all
types of pavement (flexible pavements, like dense and open graded asphalt, as well as concrete
pavement) with variable surface texture (fine as well as rough texture).
Continuous measurements
It should be possible to carry out continuous measurements.
Lane coverage
The sampling interval of the measuring equipment (video, film, and laser) should allow for full
coverage of a lane width up to 4 metres.
Perfonnance
For long term maintenance plans, it is important to be able to make a reliable estimation of the
residual lifetime of the pavements. Therefore automated surface distress data collection systems should
have a high detection rate and good repeatability.
The devices used to collect of surface distress data should have the following capability:
Cracks: length, width and direction
Ravelling: incidental loss of fine (5 mm) aggregate particles
Pot holes: hole over 2 cm deep and 10 cm diameter
Bleeding: presence of free asphalt binder giving the surface a wet look.
Other:..
The results (data) of repeated measurement runs on the same section of road, made by one or more
similar devices should not differ more than ±5% from each other in the detection of defects and not
more than 10% in the assessment of their extent.
Capacity
It must be possible to assess the pavement condition of large road networks every year.
•
•
capacity of acquiring the surface the data: at least 200 km/day (under free flowing traffic
conditions);
capacity of processing the (raw) data: minimal 100 km/day.
49
Measurement speed
It should be possible to carry out the measurements without causing road safety problems and traffic
disturbance.
•
The devices should be able to operate at variable speeds up to 90 km/hour.
Operational aspects
Most of the measurements are carried out under daylight conditions. However, this is not always
possible in some urban areas due to high traffic volumes/congestion. In this case, measurements can
only be carried out at night, when traffic volumes are low.
•
It should be possible to collect surface distress data under daytime as well as under night time
conditions.
Vehicle dimensions
The measuring equipment, like lasers, cameras and artificial light, is often mounted on the front or
rear of the vehicles. This can lead to an increase of the vehicle dimensions. However, the use of these
vehicles on public roads could be restricted if the vehicle dimensions and axle loads are too great.
•
The dimensions of measurement vehicles should be within the national dimension rules.
4.4
Recommendations
In the following subsection the recommendations are highlighted by bullet points and the discussion is
in italics. It should be noted that the subject of classification of defects was being considered, and dealt
with, to a greater extent within the COST Action 324 (Long Term Pavement Performance) and PARIS
(Performance Analysis of Road Infrastructure) projects. Finally, for the realisation of new, improved
methods and devices for the assessment of surface distress data, recommendations are presented. A
distinction is made between recommendations for the use and implementation of assessment methods
and for research and development of new methods. The first group of recommendations is relevant for
road authorities and consultants who are involved in road management and the collection of condition
data. These recommendations will help to improve global road management processes in the area of
data acquisition with the aim of optimising the allocation of maintenance funds to preserve network
value and to provide a higher level of service to users.
The second group of recommendations is relevant for researcher and developers. These recommendations are a basis for future European research and developments of new acquisition systems and will
help in defining specifications for a fully automated high-speed assessment system that meets the
performance requirements of the previous sub chapter.
4.4.1
Recommendations for users
Surface distress data collection on roads at network level is an important activity that provides a lot o
valuable information to all road authorities. There are different methods available, however the fac
that all road authorities continue to use the manual method alone or in addition to another suggests
that further development of more sophisticated methods and equipment is needed. Although it is to be
expected that automated methods save time and money, they may still be difficult to implement:
employees have to learn to work with new methods and changes in the organisation might be
necessary.
50
•
New assessment technologies require an interface within an organisation - training is essential,
new quality assurance procedures are needed, to mention a few items that need special attention.
For economical, technical and safety reasons it is desirable that surveys provide statistically useful
data. Frequent continuous surveys provide theoretically the best data. However, for less "important"
roads this policy might be too expensive.
•
A guide for road authorities must be drawn up in order to determine the frequency, regularity and
sampling method of the surveys for different types of roads and/or road constructions (including
climate and location).
As construction sites have proved, even with safety measures there are always new safety problems.
Especially when people are walking on or by the road when slow moving vehicles are used for visual
inspections. To minimise the risks, image capturing at normal speed is probably the best solution.
•
The use of image capturing systems should be encouraged to improve road safety conditions and
to prevent traffic disturbance.
Portable PC's (especially with a specific keyboard) are certainly a good aid for visual inspections.
PC's have a large capacity and make it possible to feed the data directly into a database. This makes it
easier to maintain a good database and also to calculate distress indices. PC's tend to be less
dependent on the operator, they also tend to be more uniform (including the analysis) and are
therefore, betterfor quality assurance.
•
Information on available, and specially designed portable PC's for the registration of the visual
inspection data should be disseminated in those countries expressing this need.
Not all road authorities, countries and regions have to face the same surface distress problems.
Therefor they all have their own distress catalogue, with their own distress types, severity classes and
weighingfactors.
•
It is possible to have one harmonised distress catalogue for different countries, regions, road types
and/or network levels. Different classes could be formulated and specific weighing values would
help to meet the requirements of every country, while the basic format of the distress catalogue
could be the same for all.
Visual inspections (including manual processing of recordings) are very subjective. Therefore it is very
important to have a quality assurance procedure. It will help the road authorities to improve the
quality of the measurements. The fact that most road authorities find the quality of the assessment of
surface distress data "acceptable" indicates that they are open to improvements.
•
Visual inspections (including manual processing of recordings) should be carried out in
combination with quality assurance procedures. Procedures that can be used are: random checking
by a panel of experts, periodical training and comparison of historical data.
51
The current methods for the manual processing of visual inspection data are time consumingfor use a
network level. The use of a more simplified method of collecting surface distress data for use at
network level should be considered. This would be less time consuming and less costly. (For project
level, a more detailed way ofdata collection is required).
• For planning of maintenance (budgets) at network level it is recommended that detailed distress
recordings be obtained, but to use a simplified method of processing the data. For project planning
use can be made of the same recordings.
New, improved assessment systems for surface distress, developed by research institutes and industr
arefrequentlypresented to road authorities. The performance specifications of these new products ar
described in leaflets and brochures. However, it is very difficult for road authorities to verify· the
specifications and to compare the capabilities of different systems. There is a lack of terms ofreferenc
for describing the performance of these systems.
•
International terms of reference should be developed for describing the performance of new
surface distress assessment systems.
4.4.2
Recommendations for research and development
In the last 5 to 10 years research institutes and private companies in different countries have put a lo
of effort into the development of automated methods for collecting and processing surface distress
data. However, there is little co-operation between research institutes of different countries. Althou
good progress is being made in the last few years, there is still not a fully operational image
processing system that can replace visual inspection. The development of such systems must be
supported in order to fulfil the needs of a majority (88%) of the respondents (road authorities and
others). It can be accomplished by increasing thefinancingof relevant research programmes and by
closer collaboration between laboratories, universities, research institutes and industries. FEHRL
play a very important role in achieving better co-operation and co-ordination of research and
development activities in Europe. A common research programme would also result in assessment
methods that are acceptable to all the European countries.
•
It is essential that a common research programmes be established, with support from FEHRL, to
achieve harmonisation and uniformity in the performance of equipment and also hamionisation of
standards and requirements. The subject of classification of defects is being considered, to a
greater extent, in COST Action 324 and the PARIS project.
To help with the development of a reliable, fully automated high-speed assessment system the followin
list of elements is drawn up. The list contains the design elements that should be considered in such a
development.
•
camera(s) with shutter speed and resolution sufficient to image cracks down to a width of 1 mm
over the width of a traffic lane.
camera mounting on survey vehicle to be such that the camera looks down on the surface to
minimise geometric distortion of images.
52
•
light sources to be mounted on survey vehicle so as to provide a uniform level of illumination of
the road surface that is being imaged.
•
the system should be capable of producing continuous film from discrete ¡mages for further
processing.
•
a two tier processing system:
that will quickly sift out those sections of surface that have no cracks and
that will provide detailed and accurate analyses of cracks on those sections of road containing
cracks.
•
for systems using real time automated processing - sufficient processing speed to analyse at least
every second image of the road surface.
•
automatic processing systems with the capability of producing unambiguous evidence of cracks on
deeply textured surfaces and on porous asphalt surfacings.
•
processing capabilities for the classification of the extent and severity of the surface distress types.
•
the potential of knowledge based systems in the processing of surface distress images needs to be
explored.
•
quality assurance procedure for online checking of the collected distress data.
Other elements that should also be considered include:
•
Most of the current systems do not combine recordings of distress with laser or sonar
measurements when assessing surface distress. This could be helpful because it will add
information about the texture of the pavement. Deteriorated pavements have a variable texture.
Therefore, the use of laser or sonar sensors, combined with distress recordings on film or video,
should be investigated.
•
Recordings of road surface distress must have high quality and must be easy to access. Therefore
the use of digital recordings, on tape or disk or HDTV need to be investigated. This equipment
will increase the quality of the manual and/or automated processing of the recordings.
•
Night-time survey operations require the use of artificial light. Night-time operations have
disadvantages due to difficulties in obtaining personnel and problems with road safety.
•
The intensity (brightness) of artificial light needs to be such that uniform and good quality
recordings may be made under daylight conditions. This can be achieved by using flash light
synchronised with the camera shutter. This method also reduces energy consumption.
53
54
CHAPTER 5
BEARING CAPACITY ASSESSMENT
Bearing capacity is a general concept that attempts to describe the ability of a pavement to support
heavy vehicle traffic. It thus reflects the structural condition of the road and can be used to assist in
decisions about maintenance measures intended to maintain or restore the ability of the road to carry a
certain volume of heavy traffic over a specified period of time.
A conect estimation of the bearing capacity of a road requires different types of information. It is
necessary to know for example, the thicknesses and materials of the different layers of the road
construction and their mechanistic behaviour at different moisture contents and temperatures. At
project level, it is possible and affordable to collect this information. At network level it would be too
expensive and time consuming to collect it because of the lack of high-speed measuring equipment.
This situation may, however, change in the future as high-speed measuring devices for different survey
purposes are developed.
This chapter is divided into four sections: state of the art on bearing capacity assessment, outcome of
questionnaire, system performance requirements and recommendations. The first section presents the
cunent situation in the field of bearing capacity assessment. Existing methods and measuring devices
are described. Technical development trends and current research are pointed out, where possible. The
basis for the chapter are national state-of-practice reports and a literature survey. An analysis of the
load bearing capacity responses in the questionnaire survey is presented in the second section.
The third section is an analysis of cunent requirements as expressed in responses to the questionnaire
survey and different inquiries made by members of the Management Committee.
The fourth section is a set of recommendations which synthesises the state-of-the-art and the analysis of
requirements. It proposes what could be the starting point of a terms of reference document for highspeed deflection measurement devices for monitoring road bearing capacity at the network level.
5.1
State of the Art on Bearing Capacity Assessment
For the estimation of bearing capacity at the network level, methods that rely on statistical and
empirical knowledge of pavement behaviour have been developed. These methods are based on local
deflection measurements, information on average climatic conditions and moisture content in the road,
pavement designs, the specific behaviour of the different layers based on knowledge about the
mechanistic properties of their materials etc.
There are basically three different methods for the collection of the data required for the assessment of
bearing capacity. All of them can be used as stand-alone methods but all of them also benefit from
additional information collected using one or both of the other methods.
•
Measurement of the thicknesses of the different layers of the road construction by means of
Ground Penetrating Radar (GPR). In this case, to assess the bearing capacity of the pavement,
people need to rely on statistical models for material properties of the layers and their evolution
over time, which depends mainly on age and climatic conditions.
55
•
•
Measurement of surface degradations. Surface degradations can be interpreted as the symptoms ol
the pavement wearing or deterioration. To obtain a correct estimate of bearing capacity, one has to
know the type of pavement.
Measurement of the deflection of the road surface when it is subjected to a known load. It is
generally agreed that deflection is related to bearing capacity, but in order to reach a valid
assessment of this quantity some additional information is required. The bearing capacity thus
depends on the thickness, material properties, the moisture content and the temperature of the
different layers as well as on the temperature of the surface. Surface temperature can be monitored
during the deflection survey. For other parameters, knowledge of the type of pavement and its
mechanistic properties is required.
Each of these methods has its own advantages and disadvantages. For the first one the main advantage
is that there exist high-speed radar monitoring devices. However, there are interpretation and
calibration problems that can only be solved by taking out cores from the road to be monitored; this
increases the time on site and in addition can put the workers and road users at risk.
As the thicknesses of different layers should be constant over time the only use of the radar method for
following-up the bearing capacity changes over time seems to be to monitor changes of the moisture
content in the different layers of the road and to locate the surface of the water table and the
delamination of road layers. There are, however, different opinions regarding the ability of GPR to
detect changes of the moisture content but, again, the main problem is that of the interpretation of the
signal.
The advantage of the visual survey approach is that it is a straightforward method. If there is a visual
degradation due to structural deterioration then there is a bearing capacity inadequacy. The problem is
that it is frequently difficult to distinguish between surface and structural defects. Another problem is
that this method can not give any information that is useful for preventive maintenance. Last, but not
least, there are so far no high-speed automatic devices available, capable of collecting all the data
needed for a reliable assessment of bearing capacity. Information on cracks, for example, their width,
length, direction etc., is an essential piece of information but the ability of existing devices to detect
cracks is limited to cracks wider than 1 mm, while the existence of even hairline cracks need to be
known. These cracks can presently only be found by visual inspection carried out by a person walking
along the road.
Concerning deflection measurement, the main advantage is that the information collected is directly
related to the effects of heavy axle load. When it is followed-up over time, it is to some extent possible
to predict its future evolution. The most common devices used today are stationary or slow moving
when measuring and are thus less suitable for network monitoring, even if exceptions exist. There are
no high-speed deflection devices in use but such devices are presently being developed in some
countries, which suggests that regular network monitoring of road deflection can be envisaged in the
future.
A high-speed measuring device, integrating deflection measurement, automatic collection and
interpretation of road surface distress features and thickness measurement would satisfy many of the
requirements of road managers. The availability of accurate and recent information on bearing capacity,
periodically assessed in an affordable and without traffic disturbance, would facilitate cost effective
decisions about where and when maintenance should be carried out.
56
The following information is based on the state-of-practice reports provided by the members of the
Management Committee covering the situation in their own countries, the state-of-practice reports to
the FEHRL-SERRP (Strategic European Road Research Program) committee meeting for the PAVMON (Pavement Monitoring) project held in Paris, France, 22 September 1992 and the national stateof-practice reports to the »Third Sprint Workshop, Exhibition and Demonstration on Technology
Transfer and Innovation Road Construction» in Barcelona, Spain, 8-10 March 1994. In order to give a
more general state-of-the-art report and not only a European state-of-practice report a number of other
measuring devices presently used in Europe and elsewhere are also presented.
Two of the three methods for the assessment of road bearing capacity, mentioned above, are presented
below. The third method, based on visual survey, is described in Chapter 4 of this report.
1.
2.
Measurement of the thickness of the different layers of the road construction by means of
Ground Penetrating Radar (GPR). Knowing the material properties of the layers the bearing
capacity of the road can then be assessed.
Measurement of the deflection of the road surface when subjected to a known load. It is
generally agreed that deflection is related to bearing capacity, but in order to reach a valid
assessment of this quantity some additional information is required. The bearing capacity thus
depends on the thickness, material properties, the moisture content and the temperature of the
different layers as well as on surface temperature.
The GPR is often regarded as a support to deflection measurement but it can also be used as a standalone method for the assessment of bearing capacity.
5.1.1
Ground Penetrating Radar
GPR can be used to measure pavement thickness, both bituminous and concrete, to an acceptable level
of accuracy. Knowing the pavement thickness and the foundation CBR (approx.) the original design
life of the pavement can be determined from the pavement design chart/catalogue appropriate to the
material used (i.e. cement concrete or bituminous or composite bituminous/concrete). As the pavement
is in service it will have carried a known volume of commercial traffic. Converting this volume of
commercial traffic into the equivalent number of standard axles allows the residual life of the pavement
to be calculated as follows:
Residual life (std. axles) = Design life (std. axles) - Commercial traffic to date (std. axles).
The Residual life is a measure of the bearing capacity of the pavement. This shows that one can
estimate load-bearing capacity using knowledge of pavement thickness and the design method for the
pavement. GPR can also give information on the condition of the pavement through its assessment of
subsurface voids/cracks and the moisture level in the pavement foundation and this information could
be used to prioritise structural maintenance on a road network.
The following description of GPR is taken largely from Benetti (1996). Some additional data from
other sources is, however, also included.
GPR works by transmitting short pulses of electromagnetic energy through materials using an antenna
mounted on a vehicle or guided manually over the target area. When an electromagnetic wave hits the
boundary between two substances with different dielectric constants, part of the wave carries on to the
underlying substance while the rest is reflected or scattered in other directions. The reflected energy is
57
picked up by the antenna's receiver, amplified and displayed on hard copy or monitored and stored or
an appropriate magnetic medium.
The amplitude andfrequencywith which the pulses are reflected gives an indication of the position and
type of dielectric discontinuity in the materials (air/asphalt/cement treated materials/unbound materials,
etc.). The thickness of surface and subsurface layers and their properties can be calculated by
measuring the arrival times and respective amplitude of the relevant wave peaks.
The resolution, the ability to detect thin layers, depends on the wavelength of the electromagnetic wave.
Shorter wavelengths can discriminate between thinner layers while longer wavelengths penetrate
deeper, but can only resolve thicker layers. In road measurements, however, penetration is hardly a
major problem as analysis is limited to layers close to the top. For a high frequency antenna (0,5 - 2,5
GHz) the penetration depth is in the order of 0,5 -1,5 m.
Normally measurements can be carried out at speeds up to about 60 km/h but higher speeds are
envisaged in the future. Tests have shown that at a measurement speed in the range of 60 - 65 km/h and
a sampling space of 120 - 200 mm, layer thicknesses have been measured with an accuracy of 10%. At
this speed, however, it is difficult to identify anomalies shorter than 1 m. The GPR is increasingly used
in a number of European countries for the measurement of layer thicknesses.
5.1.2
Deflection measurements
The bearing capacity of a road is not directly measurable but can be calculated from infonnation about
size, shape and depth of the deflection of the road surface (the deflection bowl) which takes place when
the road is subjected to a load of known magnitude. The order of magnitude of the deflection is in the
range of a micrometre to several millimetres and depends not only on the condition of the road itself
but, due to the visco-elastic nature of the road material, also on the speed of load application. The
structural models used to transform measurements of deflection into information on bearing capacity
will thus depend on the type of loading method used.
According to the state-of-art practice reports presented by members of the COST Action 325
Management Committee (Appendix 8.2) measurements of road surface deflection are carried out in
Europe using a number of different devices. Stationary methods include Plate Loading Tests, the
Benkelman Beam, the Falling Weight Deflectometer (FWD) and the Dynaflect. There is the slow
moving device Lacroix Deflectograph (about 1 m/s), in different guises, a moving version of the
stationary Benkelman Beam. Finally the Curviamètre, measuring at 5 m/s. The FWD is the most
commonly used device, being utilised in all countries where deflection measurements are carried out.
The second most common device is different versions of the Lacroix Deflectograph.
The Benkelman Beam, the Dynaflect and the FWD are almost exclusively used at project level. The
only exception is that the FWD, in a few cases, is reported to be used at network level. The Lacroix
Deflectograph and the Curviamètre are used at project level as well as at network level.
All the devices mentioned above are used on flexible and semi-rigid roads. In one case a modified
Deflectograph is reported to be utilised for the measurement of load transfer of joints on concrete
roads. It is also used to find weak road sections that warrant further investigation using the FWD,
which is regarded as more accurate.
58
Instead of measurements carried out randomly or according to a fixed plan the FWD measurements
sometimes are directed to road sections showing signs of distress, such as:
•
signs of structural distress (e.g. cracking) related to the load bearing capacity of the pavement,
signs of functional distress (e.g. cracking and ravelling) related to aspects of traffic safety, traffic
flow and comfort,
remaining signs related to specific characteristics and composition of the asphalt concrete.
Deflection measurements are earned out for a multitude of purposes, e.g.:
to investigate reinforcement requirements,
to obtain the stiffness moduli of the different layers of the road construction,
to calculate the residual structural life of the pavement,
to evaluate the bearing capacity of the unbound material of the sub-base, base and sub-grade
layers,
to monitor in-situ strength of lengths of the road network,
to identify weak parts of roads,
to establish priorities for road strengthening,
to monitor the strength of each layer during the construction,
for the planning of structural maintenance,
for research purposes.
The measurements are reported in terms of the maximum deflection, the shape of the deflection bowl
and the radius of the deflection as well as different statistical results. Despite the fact that
measurements carried out with stationary or slow moving machinery on roads open to traffic are either
very expensive, if the road is temporarily closed or very dangerous if not, very little ongoing research is
aimed at developing high-speed deflection meters. In Europe only Denmark, Germany and Sweden are
known to be developing high-speed deflection meters. Road surface deflection under an applied load
has for years been measured worldwide using a multitude of devices. Some of them, including those
mentioned above, are briefly described in the following sections.
The different types of deflection measuring devices are classified into the following groups that have
broadly similar operational characteristics:
•
Manual static or rolling wheel load methods - in these methods the road deflections under static or
rolling wheel loads are measured and recorded manually. Survey speed is low.
Automated rolling wheel load methods - road deflection, produced by rolling wheel loads, are
measured with the aid of electric sensors and are recorded automatically on magnetic media.
Survey speeds are in the range 2 to 20 km/h.
Automated stationary impulse load methods - road deflections, produced by impulse loads from
stationary vehicles, are measured and recorded automatically. Survey speed is low.
Automated mobile dynamic load methods - road deflections, produced by vibrating and/or rolling
wheels, are measured and recorded automatically. Survey speed is in the range 5 to 80 km/h.
59
5.1.2.1 Manual static or rolling wheel load methods
The Plate test involves the measurement of the deflection caused by a known static load applied on the
road surface by a circular plate with a specified diameter. For instance the Plate test as used in
Denmark utilises three diameters; 300, 450 and 600 mm with loads up to and including 60 kN. The
Plate test device may be mounted e.g. inside a van or at the rear end of a lorry. The Thumper is an
example of such an instrument carried in a van. It was developed by FHWA in USA and measures at
loads up to and including 40 kN.
The Benkelman Beam consists of two main parts. A stand and a 3,66 m (12 ft) long measurement
beam. One end of the beam rests on the road surface while the other is connected to a dial test
indicator. The beam is suspended in the stand 2,44 m (8 ft) from the end being in contact with the road
surface. This means that when this end moves downwards the other end will move upwards half of that
measure which will be measured by the dial test indicator. The deflection is applied by a heavy lorry
with twin tyres on the rear axle. The vehicle is placed with the twin tyres on either side of the tip of the
measurement beam and the instrument is set to zero. Then the vehicle is driven away and the vertical
movement of the surface is recorded. The only information obtained from this instrument is nonnally
the maximum deflection under a slowly moving load. However, a Portuguese version, called Tyre load
test, allows the recording of the entire deflection bowl over a length of 2,5 m.
Dehlen Curvature Meter also called South African Curvature Meter (Reinslett. 1982) is an
instrument consisting of a 250 or 300 mm beam with feet at each end and a dial test indicator in contact
with the road surface mounted in a hole in the middle of the beam. The instrument is placed on the road
alongside the rear wheel of a heavy lorry, 25 mm away from the tyre. The vehicle is then slowly driven
along the beam and the vertical position of the road surface with respect to the measurement beam is
read from the dial test indicator. The measuring is continued until the wheel has moved at least 3 m
from the starting point. The measurement gives the maximum deflection and is reported to also give the
shape of the deflection bowl. It is, however, not clear how the information on deflection and
longitudinal position of the vehicle is synchronised using the visual reading of the indicator.
The French Flexigraphe laser consists of a laser and a stand with a photocell that can move vertically.
The stand with photocell is placed on the road surface and the laser on firm ground up to 250 in away.
The laser beam is centred on the photocell and when the road surface close to the photocell stand is
loaded the photocell moves downwards and the deflection is recorded as the relative movement on the
photocell of the laser beam. The maximum deflection as well as the shape of the deflection bowl is
obtainable.
5.1.2.2Automated rolling wheel methods
The Lacroix Deflectograph developed in France, works according to the same measurement principle
as the Benkelman Beam but has a different mechanical design. The measurement beam is automatically
displaced along the road while the heavy lorry, utilised as a measurement vehicle, proceeds at a speed
of about 2,5 km/h. Deflection is measured in both wheel paths simultaneously. The equipment consists
basically of a T-shaped frame towed between the axles of the lorry. A measurement beam is, by means
of a joint, connected to each end of the crossbar of the »T». These beams are directed backwards and
the
entire
frame
is
positioned
on
the
road
surface
when
60
measurement takes place. The measurement starts when the rear wheels of the lorry are 1575 mm
behind the tip of the measuring beam and stops when the wheels have reached a point 125 mm in front
of it. Then the entire measurement frame is automatically moved forward a specified distance to be
lowered on the surface and a new measurement cycle is carried out. The axle load was originally 130
kN by design but in some countries the norm is 80 kN. The maximum deflection and the curvature of
the bottom of the bowl are recorded but the length of the measurement beam is normally too short to
give the shape of the entire deflection bowl.
There are different variations of the Lacroix concept. The French Deflecto having a rear axle load of
130 kN, measures every 4 m along the road at 3,5 km/h while the newer Flash measures in the speed
interval of 3 - 10 km/h and is reported to be used also for survey purposes. The shape of the deflection
bowl is recorded in 81 points 20 mm apart. The measurement is repeated with an interval of 5 to 10 m,
depending on measurement speed.
The English version, the Pavement Deflection Data Logging Machine (PDDL) (Kennedy and
Gardiner, 1982), measures at the relatively low rear axle load of 64 kN. A somewhat different design
involving a tractor with semitrailer, but still using the Lacroix measurement principle, is to be found in
the Travelling Deflectometer (Nielsen, 1981), developed in USA and used in a number of countries,
e.g. in Denmark. The semitrailer consists of a frame, which at the rear end is supported by an axle with
twin tyres and at the front by the chassis of the tractor. A longitudinally movable measurement frame is
carried by the semitrailer. The measurement frame carries unsprung axles with steel wheels at each end
and a Lacroix type measurement unit immediately behind the front axle. The vehicle is driven at a
constant speed of 1 - 1,5 km/h and the measurement starts by lowering the measurement frame to the
ground where it rests stationary while the vehicle moves forward. The rear twin tyres of the semitrailer
eventually reach and pass each side of the measurement beam in the same way as for the conventional
Lacroix Deflectograph. The measurement frame is then lifted and moved forward on the semitrailer
frame and again lowered to the surface for another measurement cycle. The distance between
measurement points is in the range 6 to 11 m. The maximum deflection is recorded and due to the
length of the vehicle, which allows a long measurement frame, it would be possible to record the shape
of the entire deflection bowl, except on very stiff surfaces.
Two other deflectometers based on the Lacroix concept exist in Australia. One of them, the PASE
(PAvement Strength Evaluator) is basically an ordinary Lacroix Deflectograph measuring at speeds up
to and including 4 km/h every 4 to 7 m, independent of measurement speed. The Deflectolab (Hill et
al, 1988), on the other hand, is basically a Lacroix Deflectograph but one where the entire T-shaped
frame is carried behind the rear axle of the lorry with the measuring beams directed forwards. With this
arrangement it is possible to measure the shape of the deflection bowl behind the wheel. The measuring
beams are of the same length as the Benkelman Beam and the measurement speed is 5 km/h. The
measurement starts with the tips of the beams 300 mm in front of the vertical plane through the rear
axle of the vehicle and between the twin tyres and stops when the vehicle has moved forward 2 m.
Wheel load can be chosen in the interval 40 to 80 kN and distance between measurement points is in
the range 4 to 20 m.
Also the Curviamètre, developed in France, is based on a heavy lorry with a rear axle load that can be
chosen in the interval 80 to 130 kN. The measurement principle involves the calculation of the
deflection from measurement of the vertical acceleration of a point on the surface when the rear twin
tyres of the measurement vehicle pass the point. The measurement system consists of a 15 m chain
61
with three geophones placed at equal distances along it. The chain is supported by two drums above the
rear axle of the vehicle, one behind the axle and the other in front of it. When the vehicle is driven
along the road to be measured the chain with the geophones is automatically placed on the surface 1 m
in front of the rear wheel and than picked up again 3 m behind the axle. Every point of the chain, of
course including the geophones, is stationary with respect to the road surface when the twin tyres of the
vehicle's rear wheel pass each side of the accelerometer. As the distance between the geophones is 5 m
the deflection of the road is measured at points 5 m apart along the road. The vertical acceleration of
the surface is sampled every 0,008 s, i.e. one measurement point every 40 mm along the road at the
standardised measurement speed of 5 m/s (18 km/h). This means that the shape of the deflection bowls
as well as their maximum depth is recorded. In addition also the air and the surface temperatures are
measured. (For further information see Paquet, 1977).
5.1.2.3 Automated stationary impulse load methods
The Falling Weight Deflectometer (FWD) exists in a number of versions. The FWD is normally
based on a single axle trailer that can be towed by a medium size passenger car, however, mini-van
based versions do exist. The trailer is basically a rolling platform with a guide system that allows a
specified weight to be dropped from a specified height. The weight impacts a plate supported by rubber
dampers which rest on another circular plate with a specified diameter resting on the road. The shock
pulse applied to the road has the shape of a half period of a sine wave. The loading impulse is supposed
to correspond to that produced by a passing vehicle wheel. The deflection is measured by means of a
number of geophones, one placed in the centre of the loading plate and the others in a straight line
radially from it. The load applied to the road surface is in the range of 20 to 150 kN depending on the
size of the instrument. The most common load is 50 kN applied on a loading plate with a diameter of
300 mm. The measurement procedure is normally automatic such that only a short stop is required for
each measurement point and the driver/operator does not have to leave the vehicle to carry out the
measurement.
A modern version of the FWD utilises two falling weights mounted in parallel. The distance between
them is such that there will be an upwards convex surface between the two concave deflection bowls.
This instrument has shown that it is not possible to distinguish between the Ε-moduli of layers close to
the top of the road when measuring with the single FWD (Roque et al, 1992).
The Finnish light-weight instrument Loadman with a total weight of 16 kg utilises a smaller plate, 130
mm in diameter, and of course a much lower loading pulse. It has, however, shown good correlation to
heavy weight instruments.
Dynaplaque is a French impulse generator having a weight that falls on a number of coil springs
arranged in a circle. The quotient between the weights bounce height and the drop height is a measure
of the dynamic modulus of the road. The change of this modulus at repeated measurements on the same
spot is a measure of the fatigue properties of the road.
Impulse loads can also be applied using hydraulic instruments such as The Thumper, which can give
load variations withfrequenciesup to, and including 50 Hz.
Dynaflect, also built on a single axle trailer, combines a static load of about 9 kN with a dynamic load
of about 2,5 kN varying with afrequencyof 8 Hz. The static as well as the dynamic load is transmitted
62
to the road surface by means of two steel wheels mounted beside each other under the trailer with
about 0,5 m between them. The static load is brought about by the weight of the trailer while the
dynamic load comes from two eccentric discs rotating in opposite directions. The measurement of the
deflection is carried out using five geophones, one of them positioned between the steel wheels and the
others in a straight line in front of the steel wheels and with a distance of 300 mm between them. A
local version of the Dynaflect, called the Schwinger, is used in Switzerland.
Road Rater is an instrument of the same type as the Dynaflect. The varying load is, however,
produced by a hydraulic vibrator. The Road Rater comes in three versions with different magnitudes of
the static as well as of the dynamic loads. The amplitude of the dynamic load is half that of the static
load and can be chosen in the range of about 4,4 to 35,6 kN (1 - 8 kip). Thefrequencycan be varied in
the range of 5 to 70 Hz.
Falling Weight Deflectometer
5.1.2.4 Automated mobile dynamic load methods
The so called Measuring ball (Nilsson, 1995) is a vibrating steel wheel mounted in a two wheel one
axle trailer towed by a car at about 5 km/h. The vertical vibration of the wheel is measured by means
of an accelerometer mounted at the wheel hub. The measurement principle is based on the idea that the
stiffness of the ground will cause an acceleration at the wheel. The stiffer the ground the larger the
accelerations. The acceleration is processed in a computer, housed in the towing vehicle and the
relationship between the highest acceleration peak and the exciting sinusoidal acceleration signal is
calculated. The result is a measure of the relative stiffness of the ground and is expressed in a scale
from Oto 150.
63
Rolling Dynamic Deflectometer (RDD) (Bay et ai, 1995) is an instrument similar to the Measuring
ball, but heavier and designed differently. It is a heavy lorry having a total weight of about 20 metric
tons. It carries a servo-hydraulic vibrator capable of producing dynamic loads up to 310 kN in the
frequency range of 5 to 100 Hz superimposed on a static load that can be chosen in the range of 65 to
180 kN. The load is transmitted to the road using two sets of special dual wheels mounted side by side
on separate axles and with a distance of 1180 mm between them, meaning that they are rolling inside of
the road wheels of the lorry. The special wheels are very stiff made from solid aluminium and are
covered by a tread of hard urethane. The diameter of the wheel is 457 mm and each dual wheel can
carry a load of 150 kN, much less than the machine can generate. However, wheels capable of carrying
loads up to 310 kN can be made if requested. The deflection is measured by means of an accelerometer
mounted between another set of dual wheels rolling between the loaded wheel sets and isolated from
the dynamic system. The deflection is given by the double integration of the acceleration signal. Using
an accelerometer, however, means that only deflections caused by the dynamic load variations can be
detected. The measurement speed is 5 km/h.
All the instruments described above are able to produce measurements either in a stationary mode
(discontinuous) or at relatively slow speeds (continuously in a range from 1 to 5 m/s). This monitoring
speed performance (mainly at network level) requires that special safety protections be used on roads
particularly with intense and high-speed traffic. In the latter situation it becomes more and more
difficult to cope with the existing traffic. A high-speed deflection measuring instrument has thus been
asked for in several parts of the world. Such devices have been studied in some countries in Europe as
well as in USA and some are being developed. For trade secret reasons, infonnation on the working
principle of those presently being developed is very scarce, with the exception of the Swedish Rolling
Deflection Meter (RDM) which is close to being ready forfinaltests.
The RDM is designed for continuous high-speed measurement of road surface deflection under the
load of a rolling truck tire. The measurement principle involves the measurement of the road cross
profile twice, first in a non-loaded status, and then loaded by the rear wheels of a heavy two axle truck.
The measurement vehicle is loaded in such a way that the front axle is lightly loaded, about 30 kN.
while the rear axle is heavily loaded, about 110 kN. The two cross profiles are measured by means of
two cross profilometers, each consisting of 20 distance measuring lasers. The first cross profilometer is
mounted between the axles of the truck, behind the small deflection bowl caused by the front axle and
in front of the larger bowl caused by the rear axle, thus measuring the non-loaded cross profile of the
road. The second cross profilometer is mounted immediately behind the rear axle and is used for the
measurement of the same cross section of the road when the rear axle has advanced to this position
along the road. In order to cancel the influence of road macro texture each cross profile is the average
of the distance samples over 50 or 100 mm along the road. The difference between the two cross
profile recordings is the deflection caused by the heavy rear axle. The macro texture of the road surface
can however also cause measurement errors if one point hit by a laser on the rear cross profilometer is
not perfectly aligned with the point hit by the corresponding laser on the front profilometer. This
problem is solved by fitting the discrete 20 point cross profiles with a third order spline function thus
creating continuous profiles prior to the calculation of the difference between them. The measurement
speed is normally 70 km/h and the recorded deflection is given as a mean value over a chosen travelled
distance, e.g. 20 or 50 m. Initial tests carried out using a prototype, not very ideal for the measurement
purpose, showed promising results and a new version based on a lorry especially designed for highspeed deflection measurement is cunently under development.
64
The purpose of the RDM is in the first place to make it possible to carry out bearing capacity surveys
over an entire road network. Weak spots identified can then, if desired, be more accurately studied
using the Falling Weight Deflectometer, thus making more efficient use of this instrument.
An earlier version of the German ARGUS measured road surface deflection using a simplified version
of the RDM method. Three distance-measuring lasers were used for the measurement of the deflected
profile under load of the rear axle of a heavy lorry. One laser was placed under the centre of the rear
axle and one laser each between the twin tyres of the rear wheels. Another set of three lasers was
mounted at the rear of the lorry measuring the surface when unloaded. The deflection was then
calculated as the change of altitude of the centre of the road in relation to straight lines through the
outer measuring points. In contrast to the RDM method which gives maximum deflection as well as the
shape of the deflection bowl the ARGUS method only gives the maximum deflection.
For unknown reasons this method, however, has been abandoned and replaced by a method using five
lasers mounted longitudinally along the side of the lorry. One of the lasers is mounted outside of one of
the rear wheels and the others equidistantly in a straight line. It is not known if the four lasers are all
mounted in front of the rear axle or if one of them is mounted behind the axle. All the lasers are,
anyhow, supposed to repeatedly measure the vertical distance to the same spots on the road surface.
The lasers in front of the rear wheel are supposed to measure the undeflected longitudinal profile of the
road while the profile including the measure picked up by the rear laser represents the loaded profile.
Again the difference between the two profiles constitutes the deflection. This method has been studied
several times in different countries but has always been abandoned due to limited success.
A new device utilising this method is, however, currently being studied in the USA and according to its
developers the reason for the earlier failures was contamination of the measurement signal by relative
movements between the individual sensors, caused by vibrations and/or thermal deformations of the
beam on which they were mounted. In the new instrument, the Rolling Weight Deflectometer
(Johnson and Rich, 1995), the movement of the mounting beam is monitored using a laser beam along
and inside the beam. The laser beam serves as a reference for the measurement of the deformations of
the mounting beam at the locations of the vertically measuring lasers. Knowing these movements they
can be subtracted from the measurement signals. The instrument is developed for use on airfields and
has shown satisfactory measurement results. The measuring speed is 8 km/h but a future version,
intended for road use, is supposed to be capable of measuring at 50 km/h. In both cases a tractor with
semi-trailer is used as the instrument carrying vehicle. The measuring beam is thus mounted at the side
of the semi-trailer and the road load is caused by the single axle of the trailer. One of the problems with
this measurement method is that all the lasers are supposed to consecutively measure at the same spots
along the road. This should not be too much of a problem when measuring on airfields where the
measurements can be earned out in straight lines. Measuring on roads with bends is, however, more
difficult. The suggested solution to the problem is to use lasers with a large light spot that should also
solve the macro texture problem. It is supposed that 50% coverage between two measurements should
be enough to maintain required accuracy. There is, however, another very interesting measurement
method that has been suggested in USA, the Rolling Wheel Deflectometer (Herr and Johnson, 1995).
The idea is still to measure the change of the longitudinal profile from unloaded to loaded state. In this
case two scanning lasers are mounted in line along a single axle semitrailer. The scan line of both
65
lasers is 3,7 m (12 ft) long. The rear laser is mounted outside of the road wheel of the trailer covering
0,3 m (1 ft) behind the wheel foot print and forward to 3,4 m (11 ft) in front of it. The front laser is
mounted so that the rear end of its scan line coincides with the front end of the scan line of the rear
laser. The front one is supposed to give a continuous picture of the unloaded longitudinal profile while
the rear one will give the same profile in the loaded state. As the entire continuous shape of the two
profiles is available and just one laser for each profile is used most of the problem afflicting the
longitudinal laser deflectometers are supposed to be solved. The problem of measuring in curves
remains, but can possibly be reduced by using a wide scan line. The measurement speed is expected to
be up to and including 80 km/h.
Finally, a new High Speed Deflectograph, utilising Laser Doppler frequency shift, is being developed
by Greenwood Engineering in Denmark in co-operation with the Danish Road Directorate and the
Technical University in Delft, Netherlands. Laser Doppler Vibrometers are used to measure the
vertical velocity of the surface deflecting under load from a heavy moving vehicle. By use of a suitable
number of sensors the basin that occurs on the road surface round the wheels of the vehicle is
measured. The measurements are independent of vehicle travelling speed and texture profile
irregularities.
5.1.3
Conclusions
Ground Penetrating Radar is used in a number of countries for the purpose of measuring the thickness
of the different layers of the road. It may be used as a stand-alone device but it is probably more often
used together with other instruments for the measurement of deflection, unevenness and rutting.
Although bearing capacity may be assessed using information on the shape of the deflection bowl, the
accuracy of such assessments will nevertheless be much better knowing the layer thicknesses.
Road surface deflection measurements for the purpose of estimating the road's bearing capacity are
carried out using a number of measurement methods, static as well as dynamic, stationary as well as
mobile. All of those currently available use a stationary frame of reference to measure deflection and
the highest reported measurement speed is 5 m/s (18 km/h). Measurements being carried out with slow
moving machines on roads open to traffic are either expensive if the road is temporarily closed or
hazardous if not. In spite of this fact research work in Europe aimed at developing high-speed
deflection meters is known to be carried out only in Denmark, Germany and Sweden. A new method
for high-speed deflection measurement has also been suggested in the USA.
The measurement method used in the Swedish RDM has been successfully tested but its further
development depends on funds being available. The German instrument uses a method that previously
has shown limited success but recent developments in measurement technique and accuracy as well as
in the domain of data collection and processing appear promising. The American scanning laser
method also seems promising but has not yet been tested. With regard to the Danish device, little has
been disclosed, neither the measurement method nor the state of development.
COST Action 325 was an initiative by European national representatives to find out the most
appropriate way forward for Europe in the development of high-speed devices for the measurement of
road surface deflection. Although very limited development work in this area is at present being
66
carried out it is plausible that once such devices are generally available, most European countries will
be interested in using them. It is known that FHWA in USA is very interested in implementing the idea
of using high­speed deflection meters in all the state DOTs and has commissioned a consultant to carry
out a worldwide inventory of existing high­speed devices.
5.1.4
References
1. Communications from the member countries of the COST Action 325 Management Committee
(Appendix 8.2).
2. FE HRL­SE RRP, PAV-MON - New pavement monitoring equipment and methods. Project
committee meeting, Paris, 22:nd September 1992. Reference document. SE RRP Document VII ­
Original Proposal.
3. »Third Sprint Workshop, E xhibition and Demonstration on Technology Transfer and Innovation
Road Construction». Barcelona, Spain, 8­10 March 1994.
4. Technical papers:
BAY, J A, STOKOE II, K H and JACKSON, J D (1995). Development and Preliminary Investigation
of a Rolling Dynamic Deflectometer. Paper No 950830, Transportation Research Board, 74th Annual
Meeting, Washington DC, USA.
HERR, W J and JOHNSON, W G (1995). Measurement of pavement deflection under a moving wheel
utilizing scanning laser tec hnology. Proceedings Nondestructive E valuation of Ageing Aircraft,
Airports, Aerospace Hardware. Society of Photo­Optical Instrumentation E ngineers and Materials.
Tobie M. Cordell and Raymond D. Rempt Chairs/editors. 6­8 June 1995, Oakland, California, USA.
HILL, P, YOUDALE, G Ρ, MALLON, Ρ, SHELDON, G Ν, HALEY, M, BAGIA, R Κ, LOWE, O,
CAMPBELL, Ν, GLANVILLE , D, KIRBOS, E and HIBBE RD, S (1988). Deflec tolab - A truc k
mounted automated pavement deflec tion measuring devic e. Proceedings 14th Australian Road
Research Conference, Canbena, Australia.
JOHNSON, R F and RISH, J W (1995). Rolling weight deflectometer with thermal and vibrational
bending control. QUE ST Technical Paper No 363, Rev 1. QUEST Integrated, Inc., Kent, Washington,
USA.
KENNEDY, C Κ and GARDINE R, J L (1982). The British Pavement Deflection Data Logging
Machine and its operation. International Symposium on Bearing Capacity of Roads and Airfields,
Trondheim, Norway.
NIELSEN, S (1981). Sammenlignende bæreevnemålinger med forskelligt inventeringsutstyr.
(Comparison of measurements of bearing capacity using different inventory devices). Interne notater
124. Statens Vejlaboratorium, Roskilde, Denmark.
NILSSON, Ρ (1995). Tillståndsbeskrivning, förstärkningsutredning med åtgärdsförslag.
Detaljprojektering for befintliga vägar. (Description of condition, strengthening investigation with
suggestions for measures. Detailed planning for existing roads). PN Svensk Väganalys, Karlskrona,
Sweden.
67
PAQUET, J (April 1977). Un nouvel appareil d'auscultation des chaussées: le cuniamètre. Revue
Général des Routes et Aérodromes.
REINSLETT, E (1982). Vegers bæreevne vurdert ut fra nedbøyning og krumning under provelast.
(The bearing capacity of roads assessed from deflection and bending under a test load). Net­prosjekt
»Taksering», Delprosjekt 2, Vegdirektoratet, Veglaboratoriet, Oslo, Norway.
ROQUE, R, ROME R, Ρ and RUTH, Β E (1992). Evaluation of dual-load nondestructive testing
system to better discriminate between near-surfac e layer moduli. Paper No. 920586. Transportation
Research Board, 71st Annual Meeting, January 12­16, 1992, Washington DC, USA.
5.2
Outcome of Questionnaire
In this sub­chapter a description is given of the different ways that load bearing capacity assessment
systems are used in E urope. Information is provided about the current problems and needs in the
field of data acquisition and processing. Also the purposes for which load bearing capacity is
assessed are mentioned. This information is based on the outcome of the COST Action 325
questionnaire exercise.
The questionnaire and the inquiry procedure have been presented in Chapter 3. The results of Part 2 of
the questionnaire are presented in the following sections. Each question is introduced by its number.
The numerical results are briefly reported together with a short explanation. Then a comment on the
results is presented per subject.
Twotypesof statistics have been processed:
Τ = number of respondents, taking into account the total number of returned questionnaires.
A = number of respondents limited to the answers from central or local road authorities.
In some cases statistics per country are also presented.
This distinction is made because it is considered important to base the recommendations for
improved high­speed monitoring equipment especially on the problems and needs identified by
central and local road authorities.
68
5.2.1
Aim of Bearing Capacity Data Collection
KM
Do you have methods to evaluate the bearing capacity of your roads
at network level?
YES
NO
If yes, do the methods apply to the whole network ?
or only to heavy loaded roads
Τ
A
36
8
28
3
19
9
15
4
Most respondents have methods to evaluate the bearing capacity of their roads. Of the 21countries
that answered the question, 16 have methods which apply to the whole network, 2 have methods only
for heavily loaded roads and 3 do not mention any method. Two countries have methods that apply to
sections with problems (project level) and others have methods that apply to test sections.
[Q1.2]
Give one or more purposes for which you collect data on bearing capacity:
to determine rehabilitation measures on section of roads
to determine a long term maintenance plan for roads
to predict the network evolution
to determine a long term budget for road maintenance
for research
to follow-up the efficiency of a maintenance policy
The bearing capacity data may also be used to calibrate models or to determine the short-term
maintenance plan.
In summary it was noted that bearing capacity is important for pavement management. Methods are
available for all type of roads even if a few respondents focus their answers on heavily trafficked roads,
because bearing capacity is related to fatigue and damage caused by heavy axles of trucks.
Respondents considered that the more important applications of information on bearing capacity to
determine rehabilitation measures on section of roads (first rank) and to determine long term
maintenance plans for roads (second rank).
5.2.2
Methods for Evaluating the Bearing Capacity of Roads
[Q2.1
How do you evaluate bearing capacity of the roads?
- continuously
-discontinuously
in which case is it selective or
regular or
random
69
Τ
15
24
19
4
1
A
6
15
12
2
1
[Q2.2]
The total number of answers was Τ = 37; A = 21.
The bearing capacity is determined as :
- the reinforcement thickness
- the residual lifetime of the pavement
- the residual ESAL capacity for the pavement
- the cost of the maintenance solution of the pavement
Τ
27
25
21
7
A
17
17
8
4
[Q2.3]
Bearing capacity relies mainly (T=37 YES on 38 answers; A=20 YES on 21 answers) on deflection
measurement, but in some cases, methods relying on visual assessment or other parameters as in the
AASHTO guide are used.
[Q2.4]
Because of an indexation error in the questionnaire there are very few answers (T=5; A=3) to Question
2.4.
Does the method involve the evaluation of other condition?
- needs thickness layers
- needs traffic information
- needs surface temperature
- surface distress
- moisture in the pavement
Τ
5
4
4
3
1
A
3
3
2
1
0
[Q2.5]
The deflection measurements are mainly carried out in the wheel tracks (T = 33 YES on 37 answers, A
= 18 YES on 20 answers) with a few answers «between the wheel tracks» or «both».
[Q2.7]
The total number of answers was Τ = 38; A = 21.
Deflection is measured using :
- Benkelman Beam
-FWD
- Lacroix deflectograph or similar
- Curviameter
(Some answers specify two or more devices.)
Τ
7
27
17
4
A
4
14
9
1
More precisely, answers specifying only one bearing capacity measurement device are distributed as
follow from all answers:
- Benkelman beam 5 %
- FWD 44 %
- Lacroix 13 %
- Curviameter 5 %
and when several devices are mentioned:
70
- FWD + Lacroix 16%
- BB + Lacroix 5 %
- Lacroix + Curviameter 5 %
- BB + FWD + Lacroix 5 %
- FWD + Lacroix + Curviameter 3 %
- the four devices 3 %
Among the 21 countries :
- 6 are using Benkelman beam
- 13 are using FWD
- 12 are using Lacroix
- 4 are using Curviameter.
It was noted that bearing capacity is determined as the reinforcement thickness (first choice) and as the
residual lifetime of the pavement (second choice). Combining the results of question 1 and question 2,
it appears that bearing capacity is mainly used for the programming of structural maintenance on
sections of road (project level) or for maintenance plans (network level) with the calculation of the
reinforcement thickness (quantity of maintenance) and of the residual lifetime of the pavement (priority
of maintenance).
Bearing capacity is evaluated on the whole network or on selected sections; in the latter case they are
selected on the basis of other criteria, e.g. surface distress condition. If the bearing capacity of a section
of road is defined as its reinforcement thickness and its residual lifetime then deflection measurement is
a logical parameter to estimate it. But deflection information is not sufficient by itself. The following
additional information is also needed:
the structure of the pavement (type and thickness of the different layers) is needed to calibrate
the models used and to estimate the performance of in-situ materials,
surface temperature during measurement is needed to conect deflection values obtained on
bituminous pavements,
surface distress is needed to guide the diagnosis of structural condition
traffic is needed to estimate the residual life.
Three options for the collection of this information are available:
to collect them at the network level,
to select sections of roads on the basis of other criteria, for instance surface distress, and
then to monitor those selected sections,
to monitor discontinuously the network with a sampling method.
Most answers report thefirsttwo options.
Again there is no significant difference between the road administrations and the whole community
answers, except for the preference for the use of "residual ES AL capacity of the pavement" in Question
2.2.
5.2.3
Measurements with Benkelman or FWD
Concerning the use of the Benkelman beam, the information is very scanty.
71
[Q3.1] Concerning the use of the FWD, measurements are carried out at regular intervals on roads
(T=63 %; A=56 %) or at a few points on homogeneous sections (T=25 %; A=5 %). The average
distance between measurements is close to 130 m with values ranging from 20 to 500 m, more often
from 50 to 200 m.
[Q3.2] Traffic safety precautions are always taken during measurements. Warning signs, lights, mobile
vehicles (trucks or heavy trailers) are used. Sometimes, the lane (motorway) is closed and sometimes
authorisation from the police is required.
[Q7] When measuring with FWD the most frequent load is 50 kN but in some cases other loads,
ranging from 10 to 150 kN, are used. The capacity per day is from 10 to 20 km (mean value: 14 km).
Measurement costs are in the range of 50 to 140 ECU/km depending, in part, on the number of points
where measurements were made.
5.2.4
Measurements with Lacroix, Curviameter or Similar Devices
Deflectograph
[Q4.1] Concerning the use of the Lacroix Deflectograph or similar devices the measurements are
spaced from 3 to 5 m either on selected sections, on an entire project or on the entire network but the
questionnaire does not give the percentage of those situations.
[Q4.2] The operating speed is close to 3 km/h.
[Q4.3] Traffic safety precautions are often taken (82 %) but not always (global results for
Deflectograph and Curviameter). Traffic safety precautions depend on the type of road and on the
traffic. Mobile signs and lights, sometimes with guards or lane closure are used.
[Q7] The loads commonly used range from 100 to 130 kN. The capacity per day is from 17 to 30 km .
The measurement cost is between 80 and 180 ECU/km.
Curviameter
[Q4.1] Concerning the Curviameter, the measurements are made on selected sections (sampling
methods or at the project level) or on the entire network (but the questionnaire does not give the
percentage of these situations).
[Q4.2] The operating speed is 18 km/h.
[Q4.3] For traffic safety see the corresponding section for the Lacroix Deflectograph.
[Q7] The load ranges from 80 to 130 kN. The capacity per day is from 70 to 120 km and the
measurement cost ranges between 60 and 140 ECU/km.
5.2.5
Measurements with other Types of Deflection Meters
No othertypesof deflection meters are used.
72
5.2.6
Quality Assurance.
[Q6]
Τ
19
14
Do you have quality assurance?
YES
NO
A
9
8
The quality assurance procedures referred to are mainly daily or annual calibration procedures
recommended by the manufacturers of the devices. There are no national or international standards to
which road administration (central or local) could refer and which could be the basis of a global quality
assurance procedure. Also cross-tests are mentioned. References to standards are few.
5.2.7
Performance of Methods in Use
[Q7] The performance of the different devices are rated as below.
BB/FWD
Repeatability
Road safety
Traffic distribution
Lacroix/Curviameter
Τ
A
Τ
A
good
25
13
11
5
acceptable
4
3
5
3
poor
0
0
0
0
good
5
4
10
7
moderate
21
10
6
3
bad
3
2
1
0
none
0
0
1
0
acceptable
22
11
14
10
poor
7
4
3
0
Deflection measurements are performed today, in most cases, by three types of devices:
- the FWD which is a stationary device and which is towed from one measuring point to another
along the road,
- the Lacroix Deflectograph, or similar, which is a slow mobile device measures at the speed of 3
km/h,
the Curviameter which is also a mobile device measures at the speed of 18 km/h.
The outputs from the three devices are not the same numerically. There is no significant difference in
terms of measurement costs between these three pieces equipment. The main difference between the
FWD and the other two comes from the fact that, to have the same daily capacity, the distance between
measurement spots for the FWD has to be from 50 to 200 m which is too long to make it suitable for
defining homogeneous sections.
73
The speeds of the mobile devices are too slow to get a substantial benefit in terms of increased safety
and reduced traffic disturbance.
Qualitative comments of users are consistent with the known performance of the devices:
- FWD, Lacroix Deflectograph and Curviameter have good or moderate repeatability with a slight
advantage for the FWD,
- Lacroix Deflectograph and Curviameter are slightly better regarding road safety but all cause traffic
disturbance.
It seems that the road administrations are more concerned than the average opinion about the problems
of quality of measurement (repeatability) and traffic disturbance and more satisfied than the average
opinion about the problem of safety.
5.2.8
Needs in the Field of Acquisition of Bearing Capacity Data
[Q8] Requirements within thisfieldwere reported in only one third of the answers.
Concerning accuracy, the answers range from 5 to 100 microns (absolute value) or from 0.5% to 2%.
For repeatability from 10 to 100 microns absolute value orfrom0.5% to 5% (relative value).
For the daily capacity, the answers range from 25 to 400 km with several answers between 100 and 200
km. For the mean value, road administrations are less demanding than the mean opinion (T=125 km;
A=74 km).
For the cost/km, the answers range from 25 to 250 ECU/km with several answers between 100 and 200
ECU/km and a smaller value for the road administrations (T=62 ECU/km; A=50 ECU/km).
Half of the answers express the need for equipment capable of working at traffic speed with no traffic
disturbance. Finally, three answers express satisfaction with their equipment and one indicates that
most development work should be directed to multifunction equipment and model improvements. The
small number of answers to Question, Q 8, is informative by itself. It seems that a good balance
between needs and the performance of existing equipment has been achieved.
If the information describing existing procedures is compared with the needs it can be seen that:
•
•
•
•
the range of acceptable cost is near the range of today's costs,
a slightly higher daily capacity than that of the Curviameter is requested, 100 to 200 km/day
against the present 70 to 120 km/day
better equipment accuracy is requested, which contradicts the positive comments on existing
equipment in this respect and the intended use of the equipment (pavement maintenance at the
network level),
devices that do not disturb the traffic are requested, which is consistent with the comments on
existing devices.
Unfortunately, the answers to the questionnaire do not give any information concerning the maximum
acceptable sampling distance. The distance between measurement spots using the FWD may be up to
100 m while the sampling distance for the Deflectograph istypically3 to 5 m and for the Curviameter 5
m. These short sampling distances are very useful for the purpose of defining homogeneous sections.
74
5.2.9
Treatment of Data
[09.1]
Do you use deflection measurement data in combination with surface
distress data?
YES
NO
Τ
A
30
5
16
3
The majority of users of deflection measuring equipment combine surface distress information with
deflection measurement data, in order to calculate a global index, to input into their PMS or for the
purpose of designing a rehabilitation solution. The main reason is that the combined information gives
a better insight into the actual structural performance of the road than the deflection measure alone.
[Q9.2]
Do you determine homogeneous (uniform) sections ?
YES
NO
IF YES - based on pavement construction
deflection measurement
traffic volume
pavement distress
Τ
35
2
26
26
23
19
A
19
1
15
14
14
9
Τ
35
19
9
A
19
13
5
Τ
A
18
15
10
7
[Q9.3]
In which form do you present the data ?
- tables
- figures (graphs, histograms)
- geographical (in combination with GIS)
5.2.10 New Developments
[Q10.1]
Are you aware of any new developments in the field of deflection
measurement
YES
NO
A little more than half of those answering the questionnaire are thus aware of new developments in the
field of deflection measurement.
75
5.3
System Performance Requirements
5.3.1
Synthesis
The advances in technology will make it possible to satisfy user needs with respect to new
measurement equipment and methods. The requirements on the new equipment should be the a balance
between available economic and technical resources and the level of satisfaction of the needs that
assure the success of the new technologies.
In the questionnaire most users found it difficult to define their needs because they did not have enough
information about the capability of new technologies. This situation shows a shortage of contact
between those developing new devices and the intended final users of these devices. This COST
Action is an effort to bring about an exchange of information in both directions between these groups
in order to help in the future the development of new equipment and methods for road monitoring.
Needs and requirements of new equipment are commonly defined in terms of technical, economical
and road safety parameters. Road safety related parameters are of increasing importance.
To improve road safety in road monitoring new devices should be of the high-speed type which
requires contactless sensors. It may be noted that road safety requirements affect operating costs, as an
indirect cost, and therefore the economic parameters are also linked to safety. The questionnaire
responses suggest that users agree with the current level of safety costs.
Concerning the bearing capacity there are two different uses of the equipment with different
requirements: namely network and project level assessments. Though the infonnation may be useful
for project investigations the emphasis is on network management requirements.
The type of pavement (flexible, semi-rigid or rigid) is another important aspect to take into account due
to their different structural behaviour. It is well known that the values of bearing capacity parameters,
when they are expressed in terms of deflection, vary widely from one type of pavement to another.
After a careful analysis it is possible to describe the requirements of pavement managers and designers
for the road monitoring equipment. First of all it should be noted that the value of the information in
this field would help the managers to develop decision methods based on more objective criteria. This
kind of information will also improve long-tenn optimisation of road maintenance budgets. These
requirements can be divided into technical and economic aspects. The technical aspects can be
summarised as the following: survey speed, sampling distance, accuracy and precision of the
equipment and quality of data acquisition and interpretation systems. The economic aspects are related
to the technical aspects as well as to the cost of data acquisition and interpretation. The economic
aspects are also related to the problem of knowing whether it is necessary or not to collect more
information in order to improve the basis for decisions taken by road maintenance managers.
The increase of the survey speed is beneficial for the road safety and the measurement efficiency, but
on the other hand the measurement accuracy could be reduced, as well as reproducibility and
76
repeatability of measurement and simplicity of technology. However survey speeds must comply with
local road regulations.
The measurement accuracy is related to the number of samples per unit length, but with high-frequency
technologies, it is possible to get adequate accuracy even at high speed. An increase in accuracy is,
however, required for high-speed devices for collecting surface distress information, especially for the
detection of hairline cracks. Due to lack of experience it is so far not possible to make any statement
about the accuracy needed for high-speed measurement of surface deflection as most new devices at
the present are at the development stage.
An increase in precision is always desirable, especially at the project level. Precision is, however,
related to reproducibility and repeatability. However accurate a measurement device may be, it is
also necessary that its repeatability and reproducibility are good. Applied to measurement tasks of
interest here repeatability may be defined as the closeness of agreement between mutually
independent measurement results obtained on identical road sections with the same device with the
same operator within a short interval of time. Reproducibility may be defined as the closeness of
agreement between measurement results obtained on identical road sections with different devices
and with different operators. Consequently, in order to get acceptable measurement results it is not
enough to have accurate measurement devices but also well trained operators.
The complexity of technology is increased with high-speed measurement devices because the data
acquisition systems become more complex. The greater the volume of data to be processed and the
more complex the data interpretation requirements the greater is the need for faster data transmission
and more powerful processing units.
The performance of data acquisition systems was a limiting factor some years ago. Due to recent
advances in this area such constraints, no longer limit the development of new devices. Data
interpretation is nowadays one of the most important issues regarding development of new devices.
New and future devices are able to acquire more and more data (in terms of number and type). It makes
it more complicated to analyse and evaluate them and introduces the need of combining the knowledge
of expert engineers and data processing specialists. In order to simplify this work it is necessary to
define the kind of data and variables that are really needed. Concerning deflection measurement,
information on the following parameters is required:
maximum deflection,
shape of deflection basin.
Regarding network level information, the maximum deflection is often sufficient. For project level
assessment it is necessary to know the shape of the deflection 'bowl', in order to be able to evaluate the
bearing capacity of the pavement while determining material modulus and residual life.
All existing deflection measuring devices, with the exception of the Swedish RDM, measure the shape
of the deflection basin in the longitudinal direction, i.e. along the road. Roads are, however, normally
weaker at the road edges and thus for future developments it would be advisable to take into account
the possibility of recording the transverse shape of the deflection basin in addition to measurement in
the longitudinal direction. Data interpretation depends on many of parameters. The most important are:
77
type of pavement (flexible, semi-rigid or rigid), pavement damage, layer thickness, material
characteristics and temperature and moisture content of soils.
5.3.2
Requirements
The discussion in Section 5.2 can be summarised in a number of requirements for the development of
future devices as listed below.
Pavement temperature: The device should be provided with a contactless thermometer with an error
less than ± 0,25 ?C. It is nowadays possible to get this accuracy using an infrared technique. For some
purposes also the temperature within the pavement may be needed but the measurement technique is
time consuming. The requirement on the temperature measurements are related to the purpose of the
measurement; network and design project measurements. For the network level measurements it is
sufficient to measure the air and pavement surface temperatures. For project level and flexible
pavements it is necessary to measure the temperature of the layers at the same time as the execution of
the deflection measurements. A method for that is being developed by the COST Action 324 »Long
term performance of pavements».
Pavement structure: Besides the method of taking out cores from the road, the only available
equipment that can provide this information is the Ground Penetrating Radar (GPR). Its advantages are
is that it does not damage the road or limit survey speed and the measurement process is easy. On the
other hand, the interpretation of the radar signal data is complex, especially when the pavement
structure contains many changes. Furthermore the initial cost of this device is high but the measurement
cost is rather low as compared to the coring technique. However, the radar system can not work
correctly with free water in the road structure, as the dipolarity of water makes the dielectric constant
change with the water content in the structure.
Measurement system: The deflection measurement should be carried out at high speed and
consequently it must involve contactless measurement sensors. The very precise requirements on
deflection measurement accuracy presently require the use of distance measuring lasers. Even here
there are some limitations. For the purpose of deflection measurements the road surface must not be
wet as this reduces the accuracy of the distance measuring lasers. For less demanding measurement
tasks e.g. the measurement of rut depths the road surface may be wet but there must not be any water
puddles.
Variability of the measurement load: This is not a limiting factor for the current devices, and for highspeed devices all requirements should be satisfied by a load range of 30 - 130 kN per axle.
Measurement speed: The requirements about measurement speed will be different depending on the
type of roads to be monitored. The reasons for the development of a high-speed device for surveying
bearing capacity on the network level are mainly to minimise traffic disturbance, to increase the data
collection efficiency in order to reduce costs and also to be able to carry out measurements at different
speeds. The last reason is important as the deflection for a given load on visco-elastic pavements is
speed dependent and measurement at different speeds may thus provide more information on the
bearing capacity than measuring at just one speed. The following measurement requirements are
suggested.
78
At network level:
Operating and variable speeds up to 90 km/h are needed because of highway conditions, road safety
and the length of road networks.
Data sampling: The data sampling distance is dependent on the type of road and may also depend on
the measurement speed. The maximum sampling distances for network level are: 5 to 20 m
Measurement accuracy: The requirements on deflection measurement accuracy would vary with the
purpose of the measurement. The maximum accuracy at network level is: <0,05 mm
It is thought that fully operational deflection measuring systems satisfying these requirements could be
achieved within a period of eight to ten years.
Combination of data from deflection, longitudinal and transverse unevenness, surface and thickness
data: This is a very interesting possibility because the road surface data, and especially its variation
over time, should greatly increase the accuracy of the bearing capacity assessment.
Deflection vehicle requirements are similar to those listed for the surface distress vehicle.
5.4
Recommendations
In the following subsection the recommendations are indicated by 'bullet points' and the discussion is in
italics. As with surface distress the recommendations that are relevant to road managers and to
research organisations and equipment developers are presented separately.
5.4.1 Recommendations for users
The analysis and interpretations of pavement deflection measurements to give load bearing capacity
assessments is complex involving consideration of the pavements construction, the physical property of
its materials and of the commercial traffic loading on the pavement. Information on these pavement
and traffic parameters is unlikely to be available to road managers except for the most important road
categories. Thus road managers will need to decide on which road categories load bearing capacity
assessments are needed and to collect the relevant construction and traffic data required to determine
their bearing capacity.
•
Adequate pavement management systems need to be put in place by road authorities to ensure that
relevant pavement and traffic data are available for the road networks on which load bearing
capacity assessments are required.
The load bearing capacity of flexible pavements changes relatively slowly with time and or traffic until
they are approaching the end of their nominal design lives when deterioration tends to accelerate.
Thus for economic as well as technical reasons the extent and frequency of deflection surveys need to
be defined such that road managers obtain adequate information for planning forward road
maintenance programmes at an acceptable cost.
•
A strategy for condition surveys of roads should be developed taking into account all condition
information (visual distress, functional condition and safety assessments) that is collected on the
road networks: the objective being to maximise the value obtained from surveys and to minimise
survey costs.
79
Because the determination of load bearing capacity from deflection survey data is complex it is
important that only good quality deflection data is used and that the personnel involved in the
processing of the survey data have received appropriate training.
•
Quality audit procedures, based on random checks of survey practice, need to be developed by
road authorities. Such checks could entail repeat surveys on randomly selected short sections of
road that had been recently surveyed. In addition suitable training in the data processing
techniques used to determine load bearing capacity need to be put in place to ensure that data are
correctly analysed and interpreted.
5.4.2
Recommendations for research and development
Pavement deflection and pavement thickness are two of the fundamental measurements needed to
assess load bearing capacity. Pavement thickness measurements can now be made using high-speed
radar techniques. Though there is a variety of deflection measuring equipment in routine use worldwide they all require a stationary frame of reference to measure the deflections of pavements,
generated by rolling wheel or impulse loads. A stationaryframeof reference has been needed to date,
to measure the small values of pavement deflection found on heavily trafficked roads. However its use
is the main constraint that limits the operating speed of available European deflection measuring
equipment to 20 km/h or less. As a consequence special traffic management measures are required on
busy roads to protect equipment and operators during deflection surveys, thereby increasing the cost o
these surveys. To increase survey speed it is therefore necessary to develop equipment employing
measurement systems that eliminates the need for a stationaryframeof reference. Remote sensing
distance measurement transducers would appear to have the potential to measure pavement deflection
without the aid of a stationary frame of reference. Several European research and industrial
organisations are making progress in the application of remote sensing techniques to the measuremen
ofpavement deflection at normal traffic speed. However it is important that these developments are
compatible with the needs of users for load bearing capacity assessment at both network and project
level.
•
To accelerate developments it is essential that industry, research organisations and governments
co-operate to develop a high-speed, fully automated and implementable load bearing capacity
assessment system. Such a system should also incorporate a radar based technique for the
measurement of pavement thickness.
•
To ensure compatibility with the needs of users it is also essential that a standard methodology be
established, with support from FEHRL, to evaluate new equipment developments with the aim of
achieving uniformity in their performance and a harmonisation of standards in both survey and
analysis procedures.
•
To help with the development of a reliable, fully automated high-speed deflection measuring, the
following lists the design factors that should be considered in such a development.
the measuring system should be designed to measure absolute deflections with a precision and
resolution equivalent to that achieved by an FWD.
deflection 'bowls' should preferably be measured in the direction of travel of the surveying
equipment. Systems that measure deflection 'bowls' transverse to the direction of travel will need
to show the correlation between transverse and longitudinal deflection 'bowls'.
80
the effect of any smoothing techniques used (e.g. to reduce the influence of macrotexture on the
deflection measurement process) on the magnitude of the deflection values should be clearly
defined.
the system should be capable of operating at variable speeds up to 90 km/h.
a capability of controlling the operating speed (to within 1 km/h) and pavement loading by the test
wheels (to within 1 kg) and surface temperature (to within 0.5°) should be incorporated into the
design of the equipment to allow the deflection measurements to be corrected to a standard speed
and load.
the equipment should be capable of making equally accurate deflection measurements during
daytime and night-time surveys.
all deflection measurements should have an associated distance measurement for location
referencing purposes.
quality assurance procedures should be incorporated into the system software to allow online
checking of deflection measurements and associated operational parameters.
81
82
CHAPTER 6
PAVEMENT MANAGEMENT SYSTEMS (PMS)
Pavement Management Systems (PMS) are addressed in this report for different reasons. First, PMS
are of growing importance for road managers, especially for network management. PMS provides road
managers with a cost-effective means of organising and prioritising maintenance activities. Pavement
monitoring devices, i.e. the data they can deliver, are of growing importance in modern PMS.
This chapter provides some information about Pavement Management Systems, the outcome of the
questionnaire concerning the questions about PMS and the role that new pavement monitoring devices
can play within PMS.
6.1
Background
The term Pavement Management System goes back to the end of the sixties. The basic idea was to
describe the spectrum of activities that relate to the construction and maintenance of roads. A definition
of the term was made by the OECD (Paris 1987):
PMS is the process of co-ordinating and controlling a comprehensive set of activities in order to
maintain pavements, so as to make the best possible use of resources available, i.e. maximise the
benefit for society.
The first generation of PMS were mainly concerned with the technical aspects of pavement condition.
Later on prediction models were included and also the economic aspects became more important. The
development of different PMS during the last twenty years has been influenced by several factors
including:
•
ageing of road networks in the industrialised nations, thus changing the emphasis from building
new roads to maintaining existing networks
increasing budget restraints along with a growing maintenance requirement
knowledge of the effects of road condition on road user costs
new developments concerning construction methods
less natural resources
better equipment to measure road conditions
the possibilities of computers (databases, calculation methods).
Basically PMS should help answer the following questions:
Where are road maintenance actions necessary?
When are road maintenance actions necessary?
What are the best (technical, economic, operational) road maintenance actions?
How much should be done (costs, budget restraints, one big investment or several small steps)?
If one assumes that highway authorities use some kind of systematic method to plan maintenance under
budget constraints using observed pavement conditions, then a PMS will perform broadly the following
functions:
83
evaluation of road condition-> priority assessment -> optimisation of interventions
These actions are necessary for two reasons:
1) They help the managing agency to identify, prioritise and schedule appropriate interventions on the
network or at project level.
2) They support arguments for budget allocation and convince decisions makers (up to the political
level).
An improved PMS would provide an even more effective management tool to assist road managers in
convincing decision-makers of their need for adequate maintenance budgets. The evaluation of road
condition can be improved with better measuring and monitoring systems. This can help formulate
better performance models and, therefore, improved priority assessment. Better performance models
help in predicting intervention and this in turn leads to improved economic models that help budgeting.
Economic restrictions and the rising need to maintain larger road networks make it crucial to have a
better PMS in the future.
6.2
Outcome of Questionnaire
In this sub-chapter information is presented on the extent to which PMS are used in Europe, the
purposes for which PMS are used and to a limited degree the types of network to which they are
applied. This information is based on the outcome of the COST Action 325 questionnaire survey.
In the reporting each answer is presented together with the number of the corresponding question of
Part 3 of the questionnaire. The full text of the questionnaire is given in Appendix 8.3 and information
on its design is presented in sub-chapter 3.3.
General (Q 1, Q 1.1, Q 1.2.)
Most of the organisations stated that they have a pavement management system. Of the 41
organisations that answered this question, 27 of them stated that they have PMS and 18 of the 23 road
authorities (representing 20 countries) answered the question positively.
The reasons for not having a PMS at present were answered as follows:
•
•
•
14 organisations (including 6 authorities representing 5 countries) gave one or more reasons why
they do not have PMS.
4 organisations (including 2 authorities, representing 1 country) stated that their existing
procedures are efficient.
3 organisations (including 2 authorities representing 1 country) stated that PMS systems are too
expensive.
Other reasons for not having a PMS were:
•
•
•
5 organisations (including 13 authorities representing 3 countries) stated that PMS are under
development or they had just started collecting data.
3 organisations (no authorities) declared no need for PMS or are not working on network level.
1 authority had personnel and financial problems
84
Of the 10 organisations that answered the question, whether they would use a PMS if their problems
were solved, 6 organisations (all 5 answering authorities representing 3 countries) responded with a
yes, 1 organisation said no and 3 are uncertain. The results show that practically all institutions see
benefits in having a PMS and express the intention of acquiring a PMS once their problems are solved.
UseOfPMS(Q2.,Q.3)
Thirty organisations answered the question about the reasons for using a PMS.
The ranking of all responses in decreasing order of importance is as follows:
-
To determine a multi-year maintenance scheduling for road maintenance
To determine a multi-year budget for road maintenance
To determine rehabilitation measures for road sections
To predict the evolution of the network
To follow up the efficiency of the maintenance
For research
Other
The ranking of responsesfromthe 21 answering authorities, representing 13 countries, is as follows:
To determine a multi-year budget for road maintenance
To determine a multi-year maintenance scheduling for road maintenance
To determine rehabilitation measures for road sections.
To predict the evolution of the network
To follow up the efficiency of the maintenance
For research
Other
Another stated reason for using a PMS was to identify roads for survey and for detailed inspection.
The results show that multi-year budgeting and scheduling are the most important reasons for using a
PMS. Since it is not known what kind of PMS are in use, it may well be that the ranking is based on the
possibilities and the performance of the used PMS. However, research is apparently not a direct
concern of most users.
The question concerning the road characteristics that are in use had no responses and for this reason the
results do not show on what kind of roads PMS are primarily used. Therefore, no information was
available on the details of the PMS that are used. However, information on the network as requested in
the general section of the questionnaire was given as follows:
85
Road type
Flexible
Composite
Rigid
Total without
regard to
pavement type
Tolled
motorways
Nb. of answ.
Max. [km]
Min. [km]
Total [km]
7
3500
0
4998
7
4340
0
5833
7
638
0
1168
9
8000
10
12508
Free
motorways
Nb. of answ.
Max. [km]
Min. [km]
Total [km]
24
4500
4
13284.2
24
5300
0
8127.5
24
894
0
3036.2
28
11080
0
44670.9
Main
roads
Nb. of answ.
Max. [km]
Min. [km]
Total [km]
25
21523
20
181369.8
25
4000
0
8472
25
308
0
1333.2
29
60000
20
10237.0
Minor
roads
Nb. of answ.
Max. [km]
Min. [km]
Total [km]
19
90000
20
536582.8
19
34880
0
39309
19
321
0
474
22
114680
0
674233.8
Urban
roads
Nb. of answ.
Max. [km]
Min. [km]
Total [km]
6
120000
0
282484
6
10000
0
12458
6
19
0
19
8
120000
1305
359930
Not all answering institutions divided their network by pavement type, so the number of answers in that
columns differ in comparison to the other columns.
In summary, the answers indicate large differences in the road lengths and, therefore, the networks that
have to be managed. The length and importance of a network may well influence the cost/benefit
aspect of a PMS or an assessment method.
6.3
Conclusions
Concerning the PMS and its application to the different types of networks no information was provided
which would permit the components of the systems to be identified. The answers are not clear in tenns
what exactly is considered to be a PMS. However, as can be seen above, maintenance and budget
scheduling are the most important aspects of using a PMS. But it is not clear what their actions are
actually based on. It may be:
safety aspects
technical reasons
cost/benefit aspects
a multicriteria optimisation
When it comes to optimisation based on cost-benefit analysis, it becomes imperative to rely on
prediction models. Existing databases containing road condition infonnation may be used to set up or
86
calibrate such models (see COST Action 324/PARIS Project). As can be seen above the benefits of
PMS are generally acknowledged. However, it has not yet been determined what kind of PMS is
suitable for the individual user. Not every surface distress or bearing capacity means the same for a
given network level or climate. This can make it difficult to have a common prediction model. On the
other hand, similar models or manuals (using for example weighting factors) are useful for different
reasons:
•
•
•
they can open the market for measuring equipment
databases are comparable, comparisons and improvements are easier
a certain standard of PMS improves quality assurance.
The follow up of the efficiency of the maintenance should feed back on research in order to assess the
validity of the tools used in the PMS in particular the prediction models. It should also provide a means
of evaluating the adequacy of the pavement design used.
PMS need data to work on. The level of accuracy of the data, the type of performance factors to collect
have yet to be determined. The criteria on which choices are based include the following:
•
•
•
necessary data : to meet the requirements of the objective function which is optimised in the PMS.
sufficient data: to allow for sensitivity analyses (PMS simulations).
affordable data: to allow for an implementation of PMS at reasonable costs.
It is apparent that PMS databases are most easily managed on computers. How the data are entered
depends on the type of inspection or measurement that is used. In any case, it is clear that improved
monitoring systems can help in improving prediction models and PMS. In the final count high-speed
monitoring systems may well improve the quality of data and, due to their efficiency, reduce costs.
The target for the future is to have a PMS that is flexible enough for individual needs and yet have
comparable data. This is not an easy task, because, as mentioned before, it depends on affordability,
network level and/or climate, intervention levels and cycles of measurements that may differ for certain
condition data. Suitable descriptions of essential condition data are therefore an important goal.
6.4 Bibliography
Pavement Management Systems, Road Transport Research. OECD Paris 1987.
SCAZZIGA I. Samierung Von Strassen. Grundlagen Der Strassenhaltung, Autographie, Zurich 1993.
Systèmes Des Gestion Des Chaussées, OECD Paris 1987.
87
88
CHAPTER 7
GLOBAL SYNTHESIS
7.1
Background
In this chapter a general overview of the results of the previous chapters on surface distress, bearing
capacity and pavement management system is presented and possible benefits of new pavement
monitoring devices are discussed.
Generally, it was found that stationary or slow moving assessment devices and methods are still widely
used and may even be the most economic for certain network levels or even certain distress data, at
least in the near future.
In the case of surface distress these mainly refers to manual visual inspection on foot or in a slow
moving car. Although this method might still be the most accurate for certain distress types, there are
drawbacks that are generally acknowledged:
time consuming
traffic disturbance
safety problems
often subjective
difficult on heavily trafficked roads
not suitable for large networks
These drawbacks have direct and indirect economic consequences that can not be ignored. However, it
is shown that there is room for improvements. Common approaches, computer-based manuals and
definitions, preferably organised in a portable PC, might improve quality assurance and could make the
data comparable and less subjective, as well as making it easier to build a useful data base.
In the case of bearing capacity it became obvious that stationary or slow moving measurements of
deflection are the most common in practice and probably will be for a while, even more so than is the
case for surface distress. The drawbacks of these devices can be summarised as follows:
time consuming
traffic disturbance
safety problems
need for additional data (for example temperature)
difficult on heavily trafficked roads
not suitable for large networks
discontinuous
As in the case with surface distress, these drawbacks have direct and indirect economic consequences
of increasing importance since many road authorities are increasingly confronted with large and ageing
networks that have to be maintained. Improvement of the cunent methods would be a useful first step.
For example:
89
•
•
As could be seen in the Proceedings of the 4th international Conference on the Bearing Capacity
of Road and Airfields (Minneapolis 1994), the interpretations of FWD data are still variable. To
find a common method of interpretation would be a major improvement (COST 336). It could also
help to define standards and common calibration procedures (quality assurance).
Since deflections vary with time, due to changes in moisture contents, and temperature, further
research is needed in order to provide comparable and valid data.
However, the current drawbacks and future tasks call for a broader approach to find solutions to these
problems and they justify the emphasis that COST Action 325 has put on new pavement monitoring
systems. But it is not only a question of data collection, the organisation and interpretation of these data
are just as important. The chapter on pavement management systems (PMS) showed the importance of
such an additional aid.
The previous chapters in this report show that progress is being made in these areas. New pavement
monitoring devices are used or are being developed in order to provide better data and to minimise the
drawbacks of the old methods. One major step is the development of high-speed road monitoring
devices. These devices offer the following advantages:
•
•
•
•
little or no traffic disturbance,
a measurement that is more or less continuously,
increased survey capacity
suitability for network surveys
As seen in the chapters on surface distress, there is a variety of high speed systems with different
features. These systems are not to be seen as single function, they are usually multi-function surface
data collecting systems that include evenness and texture measurements. In the case of GPR (Ground
Penetrating Radar), also with a structural condition assessment capability, it could theoretically be
easily combined with the other surface measurements in one multi-function system.
Concerning the distress types that are mainly addressed in this report (i.e. cracks, potholes, bleeding
etc.) the main targets for the future are improved camera systems, to identify and quantify a distress,
and better automated processing systems, since manual processing is time consuming.
Therefore, future goals for the development of combined assessment devices include:
better camera systems
faster automated data and image processing
common distress (especially crack assessment systems) definitions (quality assurance,
comparability, broader market)
useful and accurate measurement of texture data (skid resistance, noise) is becoming more
important
harmonisation and/or standardisation of profiling methods (transverse and longitudinal profiles,
texture)
improved GPR (Ground Penetrating Radars) for distress data
definition of calibration procedures
90
Since a lot of existing high-speed profiling systems (transverse and longitudinal) could theoretically be
equipped with surface distress assessment, as mentioned before, a lot of data collecting could be carried
out in one pass. PMS can only benefit from such advantages.
As seen in the bearing capacity review, high-speed deflection measurement systems are cunently being
developed, mostly on large trucks. To have such systems operating at network level is a target for the
future as they:
•
•
•
are fast, so that there is less traffic disturbance,
have a high sample rate
could be an efficient tool providing important structural information, especially at network level.
In order to develop such bearing capacity devices future developments should include:
measurement of moisture content in road foundations
reliable contactless thermometers for pavement temperature
measurement at different speeds
data sampling at network level preferably between 5 and 20 m
a capability to collect other structural or surface distress data
Ground Penetrating Radar might become a useful tool to provide improved maintenance and structural
information. It could help to find "weak spots" and the use of stationary deflection measures could be
optimised and hence help to reduce costs. Since GPR is faster then most current deflection
measurement systems it might be more practical for collecting sufficient structural data at network level
(and it also works on concrete roads). It should also be possible to combine GPR with other pavement
monitoring systems in one device.
It has also to be noted, that accuracy requirements may not be the same for road maintenance (network
and/or project level) and research. This also raises the question of when, where and how often should
measurements be made. PMS has proven useful in that respect. It is a noteworthy result in this report
that most road authorities are used to the idea of working with a PMS. A "good" PMS needs valid data
and only valid data can provide good prediction models for a PMS.
The chapter on PMS showed that improved pavement monitoring systems can not only be used to
develop better PMS, they can also help to improve the performance of a PMS. PMS can play an
important role not only for road maintenance but also for research. As pointed out in the chapter on
PMS, consistent PMS that rely on comparable data are of increasing importance. Improved
measurement devices can help to improve prediction models for PMS. Experience with current PMS
has shown that it is important that such systems should be "manageable" and transparent and should be
based on reliable models. If a PMS is too complicated or needs too many, maybe unnecessary data, it is
not very useful.
Condition data should be comparable between PMS, but a PMS should also be flexible enough to
adapt to specific needs in terms of network, traffic and climate. A certain distress does not necessarily
have the same significance for roads everywhere (see also the work of COST Action 324 on this
aspect).
However, in this report the emphasis is on distress monitoring systems and bearing capacity
assessment, but it should also be mentioned that evenness (safety, ride comfort), skid resistance
91
(safety) and maybe texture (skid resistance, noise) are also important parts of PMS, where
improvements (measuring systems, harmonisation, models) are also needed. The PIARC Experiment
on skid resistance in 1992 and its planned experiment on profiling also point in this direction.
Accurate traffic information is also becoming more important (weigh in motion) - developments in
weigh in motion systems at European level are being examined in greater detail in the COST Action
323. Information on COST Action 323 may be obtained via CORDIS on the Internet.
7.2
Benefits of New Pavement Monitoring Devices
Besides the technical improvements described in the respective chapters, there are also potential
benefits on the operational sidefromthese new systems. They can be summarised as follows:
Benefits for authorities:
•
with high-speed systems, less traffic management measures are needed. There is less traffic
disturbance, improved safety and fewer personnel are required.
•
the condition data assessment is less time dependent and the quality of the infonnation is,
therefore, better, be it at project or network level.
•
automated and harmonised data collection and data processing makes the results less subjective
and improves the quality of the data, also when used in a PMS.
•
decision makers have more information on which to base policy decisions.
Benefits for researchers:
•
high-speed monitoring can collect specific data in a relatively short time.
•
comparable data make it easier for researchers to work scientifically, to obtain condition data from
data bases and to develop a better understanding of the mechanisms involved in pavement
deterioration.
•
the new systems could be adapted to specific needs in terms of research.
Benefits for the industry:
•
with high-speed systems consultancies or engineering firms can obtain a good condition survey
tool with a large survey capacity that can measure many condition parameters in one pass of the
survey equipment.
•
with standardised measuring systems firms can easily adapt to the individual needs of a broadened
market of customers.
Besides the technical and operational benefits of high-speed monitoring systems, a very important
aspect is the financial benefits that these systems can bring.
92
The question of possibility versus affordability is directly linked to the equipment used, the
measurement accuracy required and the cycle of condition surveys and, therefore, also to the question
of a suitable PMS for a network. For example, the required accuracy and cycle of measurements, and
therefore the costs, for research may not necessarily be the same as for a PMS for a certain network,
project or region. However, the costs versus benefits of road monitoring, preferably also using other
structural data, for example organised in a PMS, can generally be described as follows:
Road condition may be assessed mainly using information on bearing capacity and surface distress and
their change over time. Information on some other pavement characteristics, for instance materials,
pavement type, layer thicknesses can aid the assessment process. Access to such information,
preferably organised as a PMS, should lead to more effective, and in the long run, less costly
maintenance measures. The overall benefit is the reduced total costs when maintenance measures are
based on such information as compared to the total costs of alternative measures.
The reasons for assessing road condition may now be defined for three levels of information needs: a
strategic level, tactic level and an operative level.
The strategic level means that the collected information on the road or network condition forms a better
base for estimating maintenance needs. Applications for grants may thus be ascribed a higher degree of
trustworthiness, possibly leading to a better agreement between maintenance needs and allotted
resources. The benefits on this level come from this better agreement.
The benefits on the tactic level come from the ability to better prioritise between maintenance needs for
different maintenance alternatives within a region or a network, taking the information on the road or
network condition into account. The increased knowledge makes it possible to distribute allotted
resources in a more effective way.
At the operational level the costs may be reduced if information on the road or network condition is
available, when tenders for road constructions are invited.
The examples above show that improved and reliable road monitoring devices and PMS (in general:
knowledge of the structural condition of a road or a network) can help to reduce costs. The better the
infonnation the larger the benefits. However, it also depends, on the costs of obtaining this information.
Therefore, it not only depends on the possibilities and affordability of a certain measurement, it also
depends on the benefits a measurement brings to the management of the whole system.
Although they might cost more than current assessment methods (and need specifically trained
operators) new high-speed pavement monitoring systems help to reduce costs very specifically in fields
like:
•
•
•
traffic measures (personnel costs, economic costs of traffic disturbances, security measures)
personnel costs (less personnel involved in data assessment and processing)
with their greater capacity the new systems can be used by several authorities covering larger or
several networks
93
7.3
Conclusions
For the management of road networks, road managers can rely on devices and methods for the
collection of virtually all road data they need as input to their PMS. Most measuring equipment are
high-speed but amongst exceptions there is bearing capacity and to some extent surface distress. For
the assessment of the bearing capacity of roads only stationary or low-speed devices presently are
available. The measurement parameter almost universally used is the road surface deflection under a
known load. The practice of managers, laboratories and consultants to assess the bearing capacity
based on deflection measurement is consistent all over the COST countries. In the case of the
collection of surface distress data, visual inspection and subjective evaluation is the current practice.
Although, in some cases, the evaluation is carried out at the office based on images of the road surface
collected at high-speed, visual inspection on site carried out on foot or in slow moving vehicles is still
the general rule.
The stationary or low-speed assessment methods have several shortcomings:
• data collections takes place in hazardous safety conditions for both road users and operators,
unless the road is closed to traffic, in which case it is very expensive,
• data collection is time and cost consuming at network level,
• visual surveys of surface distress are subjective which make the data less reliable
• Road managers have developed their pavement management procedures based on the existing
monitoring methods (models, interpretation, monitoring frequency etc) and the questionnaire
results show that they do not really anticipate technological progress. In the field of road
monitoring methods and devices, a bottom-up scheme to manage technological progress should
therefore be applied. That is, access to high-speed methods and devices will allow road managers,
scientists and engineers to improve existing, or to develop new, pavement management procedures
that are more accurate, more reliable and with a higher degree of certainty in predictions of the
future development of the road.
Road authorities need sufficient and reliable data as input to PMS. However, the consequence of the
slow rate of collecting and evaluating bearing capacity and surface distress data is that the road
condition is not assessed and followed-up as it should be. The frequency of data collection may be too
low or the whole network is not assessed or the information is not available at the requested time in the
process of maintenance planning. A lack of timely data or unsatisfactory data on surface distress and
bearing capacity thus makes it difficult to evaluate the road condition, to prioritise and optimise road
maintenance actions and to determine the maintenance budgets.
Road authorities of course would like to increase the capacity and lower the cost of data collection
systems. Although the investment costs of new fully automated high-speed data collection systems are
high, they will help to reduce costs like personnel costs, costs of traffic disturbance, costs for safety
precautions and last but not least reduce accident risks for personnel involved in the data collection.
The efficiency of these systems means that they can be used for surveying even vast networks thus
increasing the quality of input to PMS and consequently increase the likelihood that correct road
rehabilitation or maintenance measures will be taken.
Presently there are no operational automated high-speed systems available for the collection of surface
distress data and for the assessment of bearing capacity. However, the development of new
measurement and processing techniques has made rapid progress in recent years. The development of
94
prototypes for pavement deflection measurements and for the detection of pavement cracks has been
rather successful. However, these systems do not yet detect all types of surface defects. Further
research and development is necessary.
In terms of efficiency and safety, a general goal for the future is a vehicle that is able to measure at high
speed as many condition parameters as are needed, i.e. surface distress, bearing capacity, as well as
other road characteristics like longitudinal and transverse profile, texture and skid resistance. Within
this context it is essential to establish common research programs in order to standardise data reporting,
harmonise requirements on equipment and achieve quality assurance and uniformity in the use of
equipment. Such projects can be encouraged at the technological level by funding co-operative
research between European laboratories (e.g. under the guidance of FEHRL) and universities. They
can also be encouraged by co-ordinating European countries on the definition and the use of deflection
measurements and distress information at network level. Standardisation concerning data collection
within these areas and procedures to check the quality of methods and equipment should also be dealt
with at a co-operative basis. An appropriate environment in which new equipment and methods could
grow and spread would thus be created.
For the development of new high-speed automated road data collection systems, this report presents
systems performance requirements. These requirements describe terms of reference for future
European research and development projects. Developers from research institutes, universities and
engineering companies involved in the development of high-speed data collection devices will find
information about the required capabilities, capacity, accuracy, repeatability, resolution and
measurement speed. The report, however, also indicates that the needs in terms of e.g. accuracy and
cycle of measurements may differ between agencies involved in research and road maintenance
respectively. In both cases further research work is required in order to establish a consensus about
which performance really is necessary. In the latter case further research is also required concerning
which kind of data is requested for the purpose of the planning of efficient maintenance work for
different types of roads.
The report provides some suggestions for future policies with respect to the fulfilment of the
requirements of different users. The COST Action 325 Management Committee is aware of the fact
that the development of automated high-speed systems for deflection measurements and for distress
data collection are very costly and time consuming. Nevertheless, the committee judges the
requirements to be realistic in terms of time and costs. With a good support, co-ordination and cooperation between research institutes, industry and road authorities it should be possible to realise a
payable, fully automated data collection system within a period of eight years.
The distribution of the final report of this COST Action will increase the knowledge about existing
monitoring equipment in the areas of measurement of road surface deflection and the collection of
surface distress data as well as with a summary of requirements and recommendations for further
development of new devices in these areas. As can be seen from the outcome of the questionnaire
there are rather few monitoring equipment in use in East European countries and so this report can
contribute to the transfer of information about such equipment to these countries together with a
summary of their usefulness for different purposes such as potential for research and the development
of PMS.
95
7.4
References
International PIARC Experiment to Compare and Harmonize Texture and Skid Resistance
Measurements, PIARC Committee on Surface Characteristics C.l, Paris 1995
The 4th International Conference on the Bearing Capacity of Road and Airfields. Proceedings,
University of Minnesota, 1994.
96
CHAPTER 8
APPENDICES
97
8.1 Technical Annex to the Memorandum of Understanding
EUROPEAN COOPERATION
IN THE FIELD OF SCIENTIFIC AND
TECHNICAL RESEARCH
COST/277/93
VII/429/93-EN
Brussels, 16th July 1993
RG/JLA/cv
COST
Secretariat
TECHNICAL SUB-COMMITTEE
ON TRANSPORT
COST-325
(New pavement monitoring equipment and methods)
Subject : Report to the Technical Committee (final version).
COST/277/93
98
On its 50th meeting, the COST-Transport Technical Committee set up a Technical Sub-Committee
with the aim of defining the contents of the project COST-325.
The Technical Sub-Committee held five meetings on :
-20th November 1992.
- 19th February 1993.
-29th June 1993.
- 15th November 1993.
-7th March 1994.
The participating countries were
- Belgium
- Denmark
- Finland
- France
- Germany
- Italy
- The Netherlands
- Slovenia
- Spain
- Sweden
- Switzerland
- United Kingdom
Dr Gorski
Mr Jansen
Mr Laitinen
Mr Philippe
Mr Becker
Mr Benetti
Mr De Wit
Mr Tomsic, Mr Leben
Mrs Cancela Rey
Mr Magnusson
Mr Monti, Mr Vurpillot
Mr Jordan
Chairman
Secretariat
Mr Philippe (France)
Mr Alfaro, Mr Goddard. (C.E.C.)
99
GENERAL DESCRIPTION OF THE PROJECT
1. Introduction.
Strict management of road networks maintenance budgets is a requisite for all authorities, either
national or local, whether in developed or in developing countries, or in countries where the economy
is under transition. In each case, the level of maintenance expenses will be the result of a technicoeconomical compromise.
Management of road networks is a complex operation as various types of network and different
structures at different levels of condition have to be taken into account. Moreover, the evolution of
these conditions depends, inter alia, on weather conditions, levels of traffic and construction conditions.
To tackle this problem, the management policy to be implemented is generally structured at several
levels :
hiérarchisation of the networks,
definition of service levels,
definition of technical policies
knowledge and follow-up of network conditions (through network monitoring)
It can thus be seen that network monitoring is both part of a more global task and an essential
component of any maintenance management policy.
Several road status parameters must be recorded in order to know and follow the condition of the
network. The present co-ordinated research project is aimed at defining new methods and new tools
designed for the measurement of road surface distress and bearing capacity. Currently, these
characteristics, which are essential for knowing the condition of a road, can only be recorded at slow
rates, and in hazardous safety conditions both for road users and operators. It is necessary, on a worldwide scale, to have highly efficient tools and methods available to meet the requirements of network
managers.
2. General background.
State of the art in road network monitoring.
At the network management level, people have to collect data at the scale of a network to fill road data
bases. The information stored in the data bases are then processed to determine maintenance and
rehabilitation priorities for sections of road (short term), to follow-up the efficiency of a maintenance
policy (medium term), and to predict the network evolution (long term). This concerns primary,
secondary and minor road networks for which it is necessary to guarantee levels of service and to
optimise the allocation of maintenance funds. Concerning the interpretation of data, researchers are
working at the establishment of reliable models for medium and long term prediction, based on
evolution observed in the past. The COST Action 325 project will bring a significant contribution to
this domain if adopted.
100
A critical requirement at the network management level is the collection of data on the roads in an
efficient way. This implies collection of the appropriate data (in terms of definition, precision, rate ...),
in a short time (to provide a close feedback), at the lowest cost. For most surface characteristics
parameters (skid resistance, texture, longitudinal and transverse profile, road geometry), more or less
efficient measuring tools are currently available.
A number of other international collaborative projects are also involved in the field of pavement
monitoring :
The PIARC experiment, aimed at comparing texture and skid measurement
equipment ;
Standardisation, on a European scale, of road surface characteristics,
commencing by the standardisation of the testing methods.
The main problem, however, concerns the survey of surface distress. Cunently this is a time
consuming and tedious operation, even when it is computer aided. The examination in laboratory of
video films taken at normal speed avoids the necessity of working under traffic, but introduces the
constraint of working in front of a monitor. However, the major drawback of visual surveys are there
inherent subjectivity and lack of reliability. For this reason many laboratories are involved in automatic
surface distress analysis research.
Concerning the structural evaluation of pavements, the measurement of their bearing capacity is also
time and cost consuming operation at the network level. In this field, all continuous measuring
instruments operate by sequentially moving a static mechanical device to measure the deflexion bowl
and in consequence they cannot be operated at high speed. It is therefore necessary to encourage the
development of research on non-contact high speed deflection measurement principles.
Such projects are of major interest for the assessment and follow-up of road networks.
Motivation.
The proposal is aimed at developing international research co-operation in the fields of high speed
measurement of road bearing capacity and automatic survey of surface distress, which are fundamental
in terms of road management and are cunently the object of individual efforts.
For both fields, co-operation between research and development teams on an international scale will
allow :
pooling of knowledge and research facilities ;
sharing the effort for the accomplishment of difficult topics;
giving a widespread field of application for the future products resultingfromthe research;
3. OBJECTIVES.
The objectives of the COST Action 325 project are :
101
To have a more European view of the needs of people who use data collected on networks
to manage road network maintenance;
To report the state of the art on current research on the development of high speed
measurement tools and methods and on current technologies available to fit the objectives;
To establish realistic terms of reference of new high speed measuring instruments and
methods that would be compatible with users needs, integrating safety, measurement and
cost and would transcend compatibility constraints;
To form a solid basis for future European research and development projects, integrating
developers and users from different countries. The addition of individual efforts should
lead to as a more efficient research and development process with, at the end, more
general applicable products;
To improve global road management processes at the level of data acquisition with the
aim of optimising the allocation of maintenance funds to preserve network value and to
provide a higher level of service to users.
4. WORK PROGRAMME.
The work programme is made up offivetasks whose general organisation is represented in figure 1.
TASK 1 : information gathering.
surface distress analysis and bearing capacity measurements at the level of road networks;
related topics such as the use of data, models and other road parameters measured;
current research and development projects to improve existing measuring apparatus or to
develop new apparatus;
new technologies that could be well adapted to our needs;
TASK 2 : surface distress
The goal of this task is to use the information collected during TASK 1 to get a more general point
of view on :
the current needs of surface distress analysis in Europe, at the level of road network
management, in terms of level of precision, measurement frequency, cost, acquisition
constraints,... depending on the type of network, the geographic situation,...
the cunent projects to improve existing apparatus or to develop new apparatus. The
possible contribution of new technologies will be analysed.
102
This task will lead to a synthesis that will show how current R&D projects fit present needs.
TASK 3 : bearing capacity.
Same as task 2 in thefieldof bearing capacity measurement.
TASK 4 : general synthesis.
Taking into account the global context of road network management and the results of TASK 2
and TASK 3, TASK 4 will have the study and specify requirements for new tools and methods in
both investigated fields and propose recommendations for future systems.
At this stage, connections will be established with other international programmes and especially
with the COST Action 324 project.
TASK 5 : preparation of reports.
This task is the concluding and production stage of the proposed work programme. It will result in:
state of the art and an analysis of needs;
requirements for specialised measuring instruments;
recommendations for future systems.
5. DURATION.
The estimated duration of this action is two years.
6. ESTIMATED COSTS.
The estimated cost of this action is 1 million ECU.
103
8.2
State of Practice Reports
BELGIUM
DENMARK
FRANCE
GERMANY
GREECE
ITALY
THE NETHERLANDS
PORTUGAL
SLOVENIA
SPAIN
SWEDEN
SWITZERLAND
UNITED KINGDOM
104
BELGIUM:
STATE OF PRACTICE REPORT
ROAD MONITORING METHODS AND EQUIPMENT
DR M GORSKI
1.
STRUCTURAL CHARACTERISTICS
1.1
Current practice in Belgium
At present and up to now in Belgium monitoring structural characteristics of roads is obtained by
evaluating the bearing capacity of flexible pavements. The term "flexible pavement" is used to
designate road structures composed of a bituminous surfacing which rests on a crushed stone base and
a granular sub-base. The standard equipment used is the Lacroix type deflectograph. In the case of
cement concrete pavements, the assessment is done by measuring relative slab movements at joints
with specific equipment developed at the Belgian Road Research Centre.
Deflectographs are used both by the Regional Public Works Ministries (Flanders, Wallonia) and by the
Belgian Road Research Centre. Monitoring is carried out on parts of the State roads at network level,
on reinforcement projects and for research purposes. In the particular case of research, bearing capacity
measurements have contributed to setting up the methodology for reinforcement, to studies related with
recycling of foundation materials, and to the evaluation of different techniques of protecting road
structures against water.
All these measurements contribute to determine the actions of road strengthening.
Two strengthening strategies are implemented according to whether strengthening at the road network
level or the strengthening of the whole or part of an individual road is considered.
In the first case the aim is to identify the routes or sections in need of reinforcement and to set an order
of priority based on the assessment of the network condition by high output measuring devices.
In the second case, emphasis is laid on the results of visual inspection of surface distress condition and
on the results of deflection measurements (under 13 tons axle load) every ±4m (bearing capacity). The
measuring parameters involved are the maximum deflection, its derived characteristic deflection which
is the statistical expression for the average bearing capacity of a section. This section can in turn be
determined by applying a criterion of homogeneity to a moving average performed on the set of
maximum deflections.
Combining bearing capacity measurements with past service life expressed through cumulated standard
axles or commercial traffic makes it possible to evaluate the remaining (residual) service life of a
structure. Classes of residual service lives are used; eight years being the threshold for triggering
reinforcement intervention.
Recently the Ministry of Public Works of the Flanders Region has adopted the methodology applying
falling weight deflection measurements for its investigations concerning reinforcements at project level.
One of the advantages advocated is that this approach allows to access semi-rigid pavements.
105
1.2
Innovation
1.2.1 Reasons for upgrading deflection measurements
Although the Lacroix Deflectograph has been in use for over twenty years at the Belgian Road
Research Centre it was felt that it could not meet the new challenges that require to speed up
monitoring and to increase measurement sensitivity. As a reminder the performance of this
deflectograph is fixed by its speed of measurement of one meter per second and its limit sensitivity of
the order of one tenth of a millimetre.
The new constrains are imposed by the following needs:
•
increased to full coverage at network level;
•
access to measuring semi-rigid pavement structures;
•
enhanced deflection measurement capabilities including full digitisation of deflection curve,
analysis of parameters (maximum deflection and radius of curvature) at individual and statistical
level;
•
integration of other measurement equipment to upgrade
multifunction device with simultaneous measuring capabilities.
deflection measurements to a
These reasons have led the Belgian Road Research Centre to acquire a new mean for evaluating road
bearing capacity. The Curviamètre which responded best to the criteria mentioned above was chosen.
This equipment was built by the French CEBTP ("Centre Expérimental de Recherches et d'Etudes du
Bâtiment et des Travaux Publics").
1.2.2 Implementation of the CURVIAMETRE
The CURVIAMETRE (MT15 Model) is an instrumented truck intended for measuring pavement
deflection under a moving wheel load.
The rear axle load can easily be varied from 80 to 130 kN. The latter is the setting used in Belgium.
It allows a relatively rapid and continuous measurement of the movement of the deformation of the
pavement along a wheel track starting one metre in front of the moving twin-wheels load and ending
three metres behind it. This entire deflection bowl is digitised in a hundred samples (spaced 4 cm) and
stored for each measurement. The geometry of the Curviamètre has been designed to prevent influence
of front axle on measurement.
Temperatures of the air and of the pavement surface are stored for each measurement.
The transducer used for detecting deflections is of the geophone type. Three of these are loosely fixed
at equally spaced intervals along a 15 metres closed loop chain. This chain passes between the twinwheels that load the pavement, each geophone being successively deposited at the pavement surface
while the truck is running. A servo system allows the movement of the chain to be well synchronised
with that of the truck avoiding any skidding of the transducers. This is furthermore ensured on curves
and for changes in longitudinal pavement slopes.
106
Monitoring speed is the optimum compromise between the sensitivity and frequency response of the
geophone and the mechanical stability of the chain movement.
Deflections are obtained by transforming the geophone signal into an equivalent acceleration response
which is in turn double integrated. The transducers are calibrated daily against a known standard.
The over all performance thus obtained can be summarised as follows :
one measurement every 5 metres travelled,
measurement sensitivity: 2/100 mm,
monitoring speed 5 m/s,
yield : 3,000 deflections per hour,
typical daily monitoring capacity of 50 to 100 km depending on the type of network.
An on board computer system manages all measurement controls and pre-processing together with data
storage. Visual and software validation of individual measurement during monitoring is available. A
purpose designed software facilitates treatment, analysis and presentation of results via an off line PC
computer. It can deliver for each measurement its position, the complete deflection curve, the
maximum deflection, the radius of curvature, the half width of bowl, surface temperature and air
temperature.
Statistical and graphical interpretation are also displayed allowing for instance to partition measured
sections into homogeneous segments, or analyse the set of products of maximum deflection times
radius of curvature. Moving average filtering is also available for analysing maximum deflections or
radius of curvature.
107
CURVIAMETRE MEASURING DEVICE
GUIDE RAIL
CHAIN
(15 m, 3 geophones)
GEOPHONE
(fixed position on road surface)
1.2.3 Applications
The following fields of investigation have been identified.
•
The evaluation of bearing capacities of networks (primary and secondary, especially collector and
transit roads).
•
The discrimination between pavement condition and soil condition in conjunction with
geographic information systems related to pedology mapping.
•
The location of zones with deficient bearing capacity associated to a diagnosis of the probable
causes responsible for those situations (in association with surface distress condition).
108
•
The gathering of data related to management systems in order to optimise technical/economical
maintenance or reinforcement solutions (use of a global structural index based simultaneously on
maximum deflection and radius of curvature).
•
The collection of pertinent data needed to design reinforcement projects.
•
The assessment of the performance of new structures and new methods of design and construction.
•
The indirect control of compaction during construction.
The procedures to carry out the monitoring and the associated interpretation of the results specific to
each field of investigation are at present being progressively set up. The procedures take account of the
category of road (primary or secondary) and the local management agency needs.
1.2.4 Multifunction upgrading
The Belgian Road Research Centre is presently upgrading the Curviamètre to the status of
multifunction measuring equipment. In order to meet the requirements of the applications objectives
mentioned above, two devices are being added. These have been tested independently and are
operational. In a first stage the two devices and the curviamètre component will be managed
independently each by its own processing computer. The resulting data files will have in common the
road chaînage and referencing.
The first device is a Geographic Positioning System (GPS) receiver which is locked to a satellite based
navigational system. Using a similar fixed base station at the laboratory, the system has been proven to
provide geographic locations to within 5-7 metres accuracy on the road. This is achieved by applying
the technique of differential GPS computation. This enables to monitor the position of the truck at
every second of time interval. The result provides the possibility to draw maps of the travelled road
section that can be conectly overlaid on existing 1/10,000 scale digitised maps.
Two major outputs from this technique are: A) production of thematic maps and, B) links to associate
deflection conditions to the local topography, soil type and overall drainage conditions. The second
device is a computer based keyboard encoder ("SAND", Belgian Road Research Centre design) which
is configured to log visual assessment of surface distress conditions. The keyboard has been set up for
measuring the extent (in percentages of the measured section) of a predefined set of specific defects
belonging to the groups of cracking, deformation, and repairs.
The aim of visual surface condition data is to provide complement information to the deflection
measurements contributing to the diagnosis of the probable causes of surface defects and deflection
deficiencies where they appear. It is also intended to discriminate pavement layer deterioration from
structural deterioration. Thus contribute to avoiding under or over-evaluation of technical intervention
solutions.
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1.3
Conditions of utilisation
The Curviamètre is used in research projects at the Belgian Road Research Centre. It is also made
available to external users on demand either for direct measurements (ex. periodic data collection for
road information systems) or integrated in a complete study (ex a reinforcement project). This service
can be supplied on the basis of one specific study at the time or through a contract establishing a
relative longer term commitment.
2.
SURFACE CHARACTERISTICS
2.1
Computerised visual inspection
The Belgian Road Research Centre has a long experience of recording surface deficiencies during
visual inspections of roads. This experience has led us to develop a tool for collecting such
information. The system is referred to as "SAND" and is characterised by its versatility, modularity
and user friendliness. It has two major advantages :
•
the transmission of information from SAND to the computerised road data base and back is purely
electronic, thus avoiding loss of time and possible errors in manual transcription,
•
the operator can access the results of the visual inspection as recorded as well as after processing,
with a view to validating his data acquisition on site.
The system is built about a central keyboard, where the information is coded. The keys represent
continuous and spot standard defects associated with their distribution across the carriageway or their
severity. The respective longitudinal positions of the defects (distance information) are recorded from
an odometer. The whole of results from the visual inspection of road sections is handled by a portable
microcomputer, which identifies and logs the sections and pre-processes the results with a view to their
validation on site.
The keys of the keyboard are configurable for any other road characteristics, for example the drainage
system, shoulders, footways,....
SAND is generally installed in a vehicle, which increases the safety of its use on roads and speeds up
the visual inspection.
Its use makes it easier to handle data from visual inspections. For instance in the VIAGERENDA
secondary road network management systems, the results of visual inspections can be used to calculate
the quantities and costs of local repairs and are instrumental in determining the overall quality index of
each road section investigated. In the structural evaluation of road pavements (by means of the
CURVIAMETER), visual inspection yields additional information for diagnosing the probable causes
of surface deficiencies. This makes it possible to discriminate between surface and structural
deficiencies.
SAND is used as a working tool in research and applications conducted by the Centre. It is also
implemented in studies requested by external clients.
110
2.2
ARAN : a multifunction survey vehicle
The Belgian Road Research Centre has acquired the ARAN, a multifunction survey vehicle for
collecting data on road surface characteristics.
This equipment manufactured by the Canadian company ROADWARE is used extensively all over the
world. European countries having such a system are France, the Netherlands, Switzerland, Italy,
Ireland and the former Czechoslovakia.
The ARAN complements and strengthens existing capacities for condition surveys. Its purchase was
based on the following considerations.
There was a need, on the one hand, to increase the yield and speed of road conditions surveys - both in
carrying out measurements and in processing and managing measured data. On the other hand, in
surveying roads there had to be a possibility to measure several parameters at the same time, so as to be
able to perform the whole operation in a single pass.
Besides surface condition surveys, the measuring equipment was to enable assessments of road
alignment and geometry components. The survey vehicle was also required to permit the incorporation
of non-standard measuring devices such as developed for example by the Centre.
As a result of all that, the ARAN is now fitted with measuring equipment for the following types of
survey :
longitudinal evenness (two new APL trailers of the Centre),
transverse profile (beam fitted with ultrasonic sensors),
road alignment including gradient, radius of curvature and crossfall (obtained from gyroscopes),
overall or detailed visual inspection using an electronic keyboard data logger (SAND developed at
the Centre),
video image recording (general and detailed views of the road and its shoulders),
automatic geographical positioning of the lanes surveyed, using navigation satellites.
Among the applications envisaged can be mentioned :
monitoring developments in network condition,
databases for optimum maintenance management (linked up for example with the VIAGERENDA
secondary network management system),
thematic mapping in connection with geographical information systems currently implemented for
public heritage management,
111
•
two-dimensional profilometry for regulating wearing courses by removing or adding material.
The ARAN is used as a working tool in research and applications conducted by the Centre. It is also
made available to external clients for carrying out specific studies and tests.
112
DENMARK: STATE OF PRACTICE REPORT
ROAD MONITORING EQUIPMENT
MONITORING OF PAVEMENT CONDITION
JAN M JANSEN, Danish Road Directorate, Danish Road Institute, Roskilde, Denmark.
Pavement maintenance planning of the State Highway network in Denmark is based on the operations
of the PM-System, BELMAN. Monitoring pavement condition is mainly executed to meet the data
requirements of BELMAN.
The system requires data from the network about a pavement's functional and structural condition as
well as traffic data information.
FUNCTIONAL DATA
Functional data is related to pavement surface characteristics and comprises collection of evenness,
rutting and friction data.
Evenness
Evenness is measured by the Danish Profilograph using a laser technique in a GM-principle based
procedure. The evenness is assessed from readings made in the wheel tracks and averaged over 10 cm
sections. Afterwards the measurements are aggregated into 100 m average values and expressed as an
IRI-value, which today also is converted into BI and PSI for post processing purposes.
Evenness measurements are performed primarily in the outer-lane such that both directions will be
monitored in a two year period. On Motorways and dual carriageways also the fast lane and possibly
the middle lane will be monitored in the same manner.
Rutting
Besides the longitudinal evenness the Profilograph also measures the shape of the cross profile at 10
cm intervals to determine the incidence of rutting and the deviation is determined by the Wire method
enveloping the measured shape of the carriage cross profile. The measurements are made in the same
sequence as the evenness measurements.
Friction
Friction tests are made by the Danish Stradograph, by measuring the side force friction coefficient in
both wheel tracks of the outer-lane. The measurements are made of two non-profiled PIARC test tyres
on a wetted pavement surface presumed to have 0.2 mm water film applied. The test is carried out with
free rolling measuring wheels, angled by 12 degrees and at a fixed speed of 60 km/h.
113
Friction tests are performed primarily to monitor presumed critical pavement sections and after wearing
course renewal. As routine, the entire State Highway Network is measured each year in one direction
of the road and next year, the other direction is measured. New wearing courses, however, are
measured in both directions three months after completion of the asphalt works.
STRUCTURAL DATA
Structural data are crucial information in the BELMAN system and comprise information on bearing
capacity and visual inspection of pavement deficiencies.
Bearing Capacity
Bearing capacity tests are performed by means of FWD-Tests which are post processed to show the
calculated residual structural lifetime of the pavement, and only if this value is less than 5 years the
overlay need will be assessed.
Monitoring of the bearing capacity therefore only encompasses sections presumed to have less than
five years residual structural lifetime and newly overlaid pavements for updating of structural
information. After reinforcement pavements are supposed to reduce their residual structural lifetime by
one year until the presumed five years is reached.
Annually, sections requiring monitoring of the bearing capacity are retrieved from BELMAN
excluding sections being rehabilitated the same year. For monitoring purposes FWD tests are executed
at 200 m intervals on both sides of the road staggered by 100 m. For short sections the spacing will be
reduced such that every section always contains at least three test points. Post-processing is based on
structural assessment from trial pits made at the test points every 300 m spacing or less if required.
Visual Inspection
Visual inspections are performed annually for all sections in the network by inspectors travelling
around by car. The information is used for monitoring the residual lifetime of the wearing course and
estimated repair expenses required to keep the carriageway pavement in operation.
TRAFFIC DATA
Traffic data is monitored by a network of automatic counting and weigh-in-motion station
supplemented by regular manual traffic counting on complementary positions. From the automated
stations, statistics are derived on parameters in proportion to vehicle classes, class of road and traffic
datafluctuationsthat enable an improved calculation of precise traffic datafromthe manual counts.
Traffic data is used for evaluation of the above mentioned functional and structural monitoring data.
114
INNOVATIONS
Further development at this moment mainly concentrate on possibilities for deriving more information
from monitoring procedures and data collection already in use.
Investigations are being made to derive texture values from laser reading on the pavement, and
evaluation of drivers comfort from power density spectres is examined. Mapping ability from the laser
measurements of the pavement surface topography are especially being investigated to be used in a
monitoring procedure for detection of potential aquaplaning risk areas on the carriageway.
Possibilities for deriving more structural information from the bearing capacity tests is also being
investigated, of especial interest is the internal strength of asphaltic materials.
Visual inspections are now recorded electronically in the field by data capture devices and this
procedure will be enhanced in future.
The Profilograph
115
116
FRANCE: STATE OF PRACTICE REPORT
ROAD MONITORING DEVELOPMENTS IN FRANCE
H. PHILIPPE
Research on road monitoring is continuing in France in order to modernise existing equipment or in
order to meet new expectations by highway engineers. The development of systems to assist highway
management generates increasing demand for high-performance measurements, if possible using multifunction equipment in order to optimise costs and speed up action. New requirements such as route
safety assessments may, in the long term, justify the development of new equipment for recording
information on the highway environment.
In France public research laboratories, road agencies, private companies, are conducting or are
involved in road monitoring research. The competition background to this area means that little
infonnation is exchanged.
We will describe a wide range of the research in progress on the following subjects :
•
•
•
recording surface distress,
measurement of deflection,
other areas.
1- Recording surface distress
Recent years have been devoted to updating the catalogue of distress and defining stringent methods of
recording surface distress that are suited to the varying study contexts : assessment, diagnosis,
overseeing, etc.
Cunently the recording is only done visually, either on site or, once removed, in the laboratory. A
major effort is currently under way to assess the performance of the visual methods in order to bring the
teams to the required level. This infonnation will also enable realistic quality targets to be set for the
automatic equipment to be developed.
The work on the MACADAM system (Ministry for Equipment - SCETAUROUTE) is for the moment
on hold. The MACADAM system (38mm film taken at night with controlled lighting, image
digitalisation and image processing) was aimed at detecting and pinpointing cracks.
As the Ministry of Equipment's needs now relate more to the recording of global parameters at
elementary road section level (typically 200m, with extent and severity of transverse and longitudinal
cracking, glazing, repairs, surface distress, etc.) avenues of new research have been mapped out. In
conjunction with the LCPC the SETRA (Service d'Etude Technique des Routes et Autoroutes), too, is
assessing the potential of the various techniques currently in existence, the commonly accepted idea
being that the solution probably lies in a combination of several sensors witch are both complementary
and redundant.
17
2- Measurement of deflection
The LACROIX deflectometer has recently been modernised. The name of this new version is FLASH.
Its working speed is roughly 10 km/h with a measuring point every 10 m (instead of 3 km/h and one
point every 3 m). The measurements will be entirely compatible with those supplied by earlier
deflectographs.
The CEBTP, has also modernised its curviameter, mainly within its instrumentation system.
There is currently no project covering a high-performance deflectometer in France. Advances made in
methods of management no longer require that this information be recorded at network level. The
deflection record is focused on areas identified as distressed or doubtful. This being the case a FLASHtype device meets current needs, apart from the traffic disturbance that it will continue to cause.
This chapter provides an opportunity to describe the methods being developed for the structural
assessment of roadways in France. The principle, which is based on a sound knowledge of the nature of
the roadway (four types : gravel watercourse, bituminous base course, non-rigid roadway, concrete)
and on exhaustive regular monitoring of road surfaces degradations and skidding resistance (every 3-5
years depending upon the type of network), consists of observing the overall state of the network in
order to assess the maintenance strategies applied and to detect the problem sections to which, possibly
after additional measurements such as deflection, priority is given according to the criteria available to
the highway authority.
3- Other parameters
3.1- Longitudinal evenness
The APL is a now fully mature device in instrumental terms, as confirmed by a recent meeting of
international users of this type of device. The fact that it belongs to the profilometer family opens up a
very wide range of potential uses. The work thus mainly concerns making use of the signal :
standardisation of the existing indicators (CAPL 25, EBO, IRI), development of local profile analysis
methods, interpretations in term of comfort and safety.
3.2- Regular transverse running surface
The LCPC has developed a transverse profile recording unit based on the principle of ultrasound in
order to assess rutting condition on road networks. The most recent work carried out has been on
optimising the ultrasound pick-ups in order to make them insensitive to the type of running surface
monitored (from large-grain coatings to coated drainage layers, via conventional bitumen layers).
Moreover the LCPC is continuing its work on the PALAS system, a laser blanket transfer profilometer
of which two types exist today (2 monofunctions PALAS 1 and PALAS 2, a multifunction SIRANO).
Technological advance has made this into a promising device for the future : high efficiency, not
outline-driven, very high transverse and altimetric resolution.
118
In general terms it proved necessary to set out in detail the indicators which could be recorded on a
transverse profile in order to have a method that was independent of equipment and provided the basis
for the qualification procedures. This work is in progress.
SIRANO: Multifunction machine
3.3- Road surface thickness
Radar has been use in France for many years. Recent shifts in demand have caused us to launch the
production of a new radar, with an updated set of instruments. In addition the tools for making use of
the signal are still being developed either in order to automate perfectly defined procedures or to ease
interpretation of the signal by the operator.
3.4- Texture of the road surfaces
The LCPC is using and marketing a device for measuring the macrotexture of road surfaces (0,5 mm
to 50 mm). We are working on extending the interpretation range of the signal towards megatexture (5
cm to 50 cm) thus plugging the gap between macrotexture and road evenness.
Once again very particular attention is drawn to the methods of utilising measurements. The aim here
is utilisation at network level, and also the checking and approval of running-surface sites.
3.5- Skidding resistance
ADHERA enables the longitudinal coefficient of friction to be measured at a selected speed between
40 to 144 km/h. The constantly increasing concern with road safety is causing us to examine the
modernisation of our fleet of three ADHERA trailers. The aims pursued are intended mainly to
distinguish between research and expert-assessment needs, and the needs linked with checking, site
acceptance and network monitoring.
At network level, the SCRIM device is used to monitor transverse friction coefficient.
119
4- Conclusion
The experience that we are deriving from our development and operation of high-efficiency roadway
network monitoring equipment is perfectly in line with the action under COST Action 325 :
•
we note first of all that we can now no longer envisage the development of a device outside a
method of operation that is intended to meet one or several clearly identified needs. This is why the
COST Action 325 questionnaire is particularly important in preparing the most general and
consensual terms of reference possible concerning the subjects being studied ;
•
we also confirm the appeal of our research work, in particular that on recording roadway surface
distress in order to expand the area of research while speeding up the scientific progress needed in
order fully to achieve the aims pursued.
120
GERMANY: STATE OF PRACTICE REPORT
MONITORING METHODS AND EQUIPMENT
SURFACE CHARACTERISTICS
Ρ SULTEN
1.
Introduction
Germany's federal highway and autobahn network comprises about 11,000 km of autobahns and
42,000 km of federal highways. The autobahn pavement condition surveys were only possible by
monitoring with high speed survey systems and automated registration (at a survey speed > 60 km/h).
Visual inspection would have placed crews and road users at risk and lead to traffic congestion.
Moreover, survey data density and data precision are considerable advantages of automated
monitoring. Furthermore surveys can be objectively and easily repeated. The survey results at network
level allow to establish a condition rating and to identify sections needing maintenance.
In Germany the decision was taken to collect four main data groups:
longitudinal evenness resp. unevenness profiles,
transversal unevenness profiles
skid resistance and
surface damages.
Based on these characteristics, the pavement condition can be described sufficiently and evaluated with
respect to the objectives. In many cases, maintenance measures can be derived directly from the
network pavement condition data. In cases of doubt not clearly pointing at one or the other
maintenance measure, a second and more detailed survey is necessary including the evaluation of
bearing capacity and core lifting.
2.
Survey and assessment concepts
The relevant characteristics and indicators of the road surface, surveyed either by visual inspection or
by automated monitoring according to the directives set up in the Federal Republic of Germany, are
shown infigure1.
The conesponding condition data have different dimensions (mm, %, etc.). For the subsequent
processing of these data for a particular road section (100 m), they are transformed (with the help of
standardisation functions) into dimensionless and thus comparable condition values, ranging from 1 to
5 (very good to very poor). These values subsequently are weighted and linked by particular
algorithms resulting in two values, namely a service value and a structural value. The poorer of these
two is selected as the relevant overall value of a section.
The standardisation procedure is outlined using the example of rut depth (fig. 2). Target values, alert
values and threshold values have been defined for each condition indicator in which motorways and
federal highways have different levels according to curve 1 and curve 2. They are partly based on tech­
nical requirements and partly on frequency distributions computed from representative road section
121
collectives. Normally, the target value is set at the value required in acceptance specifications for new
or renovated roads, according to the German evenness requirements this is 4 mm for the rut depth.
The alert value describes the situation where maintenance planning is due. It has been set at 10 mm rut
depth.
The threshold value characterises a situation where maintenance measures or traffic restrictions are to
be initiated. It has been set at 20 mm rut depth.
The condition data plotted on the abscissa are translated via the standardisation function into the
condition value grades plotted on the ordinate. Grade 1.5 is assigned to the target value, grade 3.5 to
the alert value and grade 4.5 to the threshold value.
The linkage of the condition values to the service value is shown in figure 3.
The following percentages of the values are taken into account:
maximum of unevenness value or rut depth at 25 %
theoretical water depth at 25 %
skid resistance at 50%
The service value is obtained by linking the weighted values on the basis of a combination law and a
logarithmic function.
The structural value is obtained in a similar manner, however, different weightings for asphalt and
concrete are used (fig. 4).
The service value implies traffic safety and driving comfort and is thus orientated towards the road
user. The structural value, on the other hand, is intended as an orientation for the needs of the
financing authorities.
3.
First survey
Surveys and the assessment of the pavement condition of the federal highways and autobalins in
Germany are at the responsibility of the federal states. The Federal Ministry of Transport (BMV)
financed the first survey on these roads as part of the establishment of a new road information system.
The Bundesanstalt fuer Strassenwesen (Federal Highway Research Institute, BASt) advises and assists
the authorities. It was decided in 1989 to start with the survey of autobahns as they are of paramount
importance for road transport in Germany. Before the unification of Germany, and thus without the
new states, this meant surveying about 40,000 km. At that time, neither the monitoring techniques nor
the assessment concepts had been thoroughly tested. The survey was therefore conducted in two steps.
The first step consisted of a 3,000 km roadway pilot survey in the states of Bavaria, Hesse, Lower
Saxony, and Northrhine-Westphalia. Two, three, and four-lane unidirectional roadways, asphalt and
concrete pavements and sections with and without emergency shoulders were monitored. The
monitoring and organisational results have been taken as a basis for
122
launching a first survey bid for all autobahns
drawing up instructions for survey preparation and execution
developing the basis data for 16 states
limiting the survey to the necessary extent
adapting the existing concepts to the particular conditions of automated monitoring.
After the pilot survey it was possible to start the second step of the first survey at network level in all 16
states.
The original concept envisaged monitoring of about 56,000 km in total. This was reduced to
22,000 km by deciding to survey all traffic lanes in the new states and only the right hand lanes in the
old states.
The survey was started in April 1992 and completed in September of the same year. The computed
values were submitted in the begin of 1993.
Thefirstsurvey of the federal highways was started in September 1993. However, there are 84,000 km
in total to be surveyed. We decided to survey the federal highways with single carriageways just in one
direction and to forget the passages of build-up areas for the present. The survey of the remaining
34,000 km is distributed over a period of 3 years. The first part started 1993 and concerns the states
Brandenburg, Hesse, Lower-Saxony, Northrhine-Westfalia and Saxony-Anhalt - 12,000 km in total.
The greater section of the federal highways was surveyed in 1994 and in 1995.
In 1996 the Federal Minister of Transport and the Federal Minister of Finance decided to finance
repeated condition survey in the future. Beginning in 1997, every three years the first lane of the
motorways and one direction of the two lane federal highways will be surveyed. The overtaking lanes
will be surveyed just every six years. In order to allow the consultants owning the measurement
devices to use their equipment economically, the whole volume of the survey is separated so, that one
part of the survey will be done every year.
4.
Measuring systems
The following measuring systems were used to register pavement condition in the pilot survey on
autobahns:
longitudinal evenness: HRM (High-speed Road Monitor)
transverse evenness: ARAN (Automatic Road Analyser)
skid resistance: SCRIM (Sideway-force Coefficient Routine Investigation Machine)
surface damages: GERPHO (Groupe d'Examen Routier par Photographie).
All measuring devices performed satisfactorily during the pilot survey.
It soon became obvious that simultaneous monitoring of longitudinal and transverse evenness was
necessary to reduce costs.
123
In the subsequent survey of the autobahn network the Swedish system LRST (Laser Road Surface
Tester) was used for this purpose. The remaining characteristics were registered again using SCRIM
and GERPHO devices.
Random checks of the measuring systems, the registration process as well as the evaluation of the data
were made during the entire operation.
Longitudinal and transverse evenness were checked with the newly developed Gennan system ARGUS
(Automatic Road condition Graduating Unit System), skid resistance with SCRIM.
The British HRM registers the longitudinal evenness values using laser probes attached to an inflexible
beam. In Germany, this system is the calibration standard for longitudinal evenness monitoring. The
measuring intervals for the unevenness peaks are 100 mm in the direction of driving. Transverse
evenness profiles cannot be monitored with the HRM.
The Canadian ARAN calculates the longitudinal profile by means of a vibration replace system
including the measurement of vertical acceleration. Transverse profiles are surveyed by means of a
front beam (width up to 3.60 m) equipped with ultrasonic detectors placed at 100 mm intervals.
The Swedish LRST device registers the longitudinal evenness by using a laser probe in combination
with a vertical acceleration meter. The transverse profiles are measured by means of a 2.50 m front
beam fitted with 20 laser probes. They are placed in an angular position permitting a total registration
width of 4.0 m.
The German ARGUS system measures the longitudinal profile on a laser basis using the HRM
principle. Transverse profiles are also measured using laser detectors which are mounted on the front
beam at 100 mm intervals.
For longitudinal evenness it is now accepted that a measuring system must collect profile data
approximating to the real longitudinal profile which enables the calculation of the parameters relevant
for the condition rating.
The profiles resulting from surveys carried out with HRM, LRST, ARGUS and ARAN were compared
and proved to be quite consistent, in particular as far as isolated ¡regularities and longer unevenness
waves are concerned. In Germany the unevenness value fh (W0) is used as relevant indicator in the
condition rating process.
Transverse evenness studies revealed that the rut depth can vary considerably within just 1 m, and does
not remain steady over the distance of longer sections. This has to be considered when comparing
measuring systems calculating the rut depth at different intervals in the driving direction. It was
observed that the results of ARAN, LRST and ARGUS calculations of the average right hand lane rut
depths are quite consistent. Apart from the rut depth, the theoretical water depth is also relevant for the
condition rating. This value is calculated using the transverse profile in connection with the transverse
grade.
Six SCRIM devices are cunently used in Germany for routine skid resistance measurement. The
pavement wetting devices have been significantly improved. Measuring results of the systems have
been compared and proved to be matching.
124
With the French system GERPHO, the pavement surface is filmed continuously at a driving speed of
70 km/h. Cracks of 0.7 mm width can still be registered. Surveys are only carried out at night to
guarantee the same exposure to light. The developed films are assessed according to the procedures of
visual inspection.
Surveys and the assessment of the pavement condition of the federal highways will be realised under
the same principles applied for autobahns. By means of a modified analysis of surface damages and
the multifunctional measuring system 'SCARGUS', a combination of'SCRIM' and 'ARGUS', the price
for 1 km surveying and evaluation would be further reduced.
Random checks of longitudinal and transversal evenness as well as skid resistance are effected with the
systems HRM, LSAQ ("Laser System Analyse Querebenheit" with 34 laser sensors on a rigid beam)
and SCRIM owned by the BASt.
5.
Data processing, evaluation and presentation
In order to allow an accurate and conect allocation of the condition data, a network system which is
independent of possible changes in length or road classification in the road network is needed. In
Germany, this is realised by means of the so-called network nodes coding system serving as a basis of
the road data information system. Roads are subdivided into several network sections, each one being
defined by two network nodes. Signs in the form of triangular boxes are set up in situ.
For each monitored 100-m-section condition data, condition values, service values, and structural
values, as well as overall values are established from the raw data using the mentioned concepts. Most
of the programmes have been developed during the pilot survey. The results were compiled in dBase
data files. Results can be presented in the form of lists, section profiles, network graphs, and frequency
distributions (fig. 5 to 7).
In order to present a condition rating "at one glance" in a map colour or grey shaded classes were
assigned to the respective grades. These classes are divided by the target values, the alert values, and
the threshold values. The colours and grey tones used and their meaning are:
- blue/light grey:
- green/grey:
- yellow/dark grey:
- red/black:
condition of a new road
no measures necessary
attention: reasons for deficiencies should be analysed and
maintenance measures planned
very poor condition: maintenance measures should be carried out and traffic
restrictions introduced.
With these colours or grey tones used the network deficiencies are made visible "at one glance" (fig. 6).
Subsequently it is easy to look at a particular poor section and start a detailed object-orientated study of
the conesponding raw data material.
In order to judge about the condition rating for federal states, autobahns, traffic lanes and construction
types,frequencydistributions were plotted in eight condition categories with half grade steps (fig. 7).
125
ARGUS multifunction machine
Figures
1 : Condition characteristics and parameters for bituminous concrete and cement concrete
2:
Standardisation from condition parameter to condition value
3 : Formation of service value
4: Linkage of the condition values to the service value and the structural value
5: BASt-devices:
HRM for longitudinal evenness,
LSAQ for transverse unevenness,
SCRIM for skid resistance
6: Profiles of service value and the associated condition values
(source: Auswertungen ASTRA)
7: Network representation of the overall value
(source: Auswertungen ASTRA)
8: Frequency Distribution of service values, structural values and overall values (First survey 1992)
(source: Auswertungen ASTRA)
126
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Strasbourgh
[15]
ARNBE RG, P. W., BURKE , M. W., MAGNUSSON, G. U. Α.: The Laser RST: Current
status, RST­Bericht, September 1991
[16]
SULT
E N, P.: E rfassen und Beurteilen der Längsebenheit von Straßen, in: Straße und
Autobahn, 1992, H. 2
[17]
SCHMUCK, Α.: Straßenerhaltung mit System. Grundlagen des Managements. Kirschbaum­
Verlag,.Bonn 1987
[18]
Verkehrs­ und Straßenbauseminar 1990: Systematische Straßenerhaltung ­ E instieg in die
Praxis. Fachhochschule Aachen, Tagungsband 57
128
CEMENT CONCRETE
BITUMINOUS CONCRETE
GROUP OK
CHARACTERISTICS
CONDITION
CHARACTERISTICS
EVENESS
LONGTUDINAL
UNEVENNESS
meas. ?h (??)
[cm 3 |
LONGITUDINAL
UNEVENNESS
meas. ? h ( ? ? )
[cm 3 |
TRANSVERSE
UNEVENNESS
rut depth
water depth
[unni
|mm|
TRANSVERSE
UNEVENNESS
rut depth
water depth
[mm]
[mm|
SKID
RESISTANCE
SKID
RESISTANCE
coefTSFC
l-l
SKID
RESISTANCE
coeff-SFC
l-l
SURFACE
DEFICIENCIES
NET CRACKING
part of surface
|%1
LONGITUDINAL/TRANSVERSE
CRACKS
number of slabs
[m]
CORNER
DEMOLITION
number of slabs
|m 2 |
|%]
number of slabs
|m 2 |
(%]
RAVELLING
PATCHES
CONDITION
PARAMETERS
part of surface
part of surface
l%l
|%|
coNDrnoN
CHRACTERISTICS
EDGE DAMAGES
FIGUREI
grade
ω
3
45
CO
>
JL·
-♦-»
Q.
ω
■σ
*
Í3 5
[2,5 ·
j
3
I—
|J,5J
rut depth parameter
FIGURE 2
129
CONDITION
PARAMETERS
l%l
ilue
longitudinal
unevenness
t depth
;
25%
water
depth
linking
mm
FIGURE 3
BITUMINOUS CONCRETE
CEMENT CONCRETE
SERVICE VALUE
(max) longitudinal/transverse evenness
water depth
skid resistance
STRUCTURAL VALUE
patches
revelling
net cracking
(max) longitudinal/
transverse unevenness
10%
20%
50%
20%
25%
25%
50%
STRUCTURAL VALUE
longitudinal/transverse cracks 30%
corner demolition
20%
edge damages
15%
(max) longitudinal/
transverse unevenness
35%
FIGURE 4
...
FIGURE 5: From left to right, HRM, LSAQ, SCRIM.
130
bituminous concrete
-i
10
cement concrete
1
1
1
1
1
1
1
1
1
1
1
1
1
1
11
12
13
14
15
16
17
18
19
20
21
22
23
24
kilometer
serviceability value
'|n '
threshold value
alert value
target value
longitudinal unevenness
5
i
;
threshold value
4
alert value
Φ
I
3
2
target value
II
1
IMU
skid resistance
5
threshold value
4
Ä*
I3
1
ru
alert value
A/
rW
\
target value
rut depth
threshold value
alert value
target value
water depth
threshold value
alert value
target value
FIGURE 6
131
Condition Evaluation Pilot Survey BAB
Lo
(O
LEGEND
1.0-1.49
1.5-3.49
3.5-4.49
4.5-5.00
FIGURE 7
Frequency Distribution First Survey 1992
bituminous concrete
100%
80%
60%
40%
20% -
1.0-1.49 1.5-1.99 2.0-2.49 2.5-2.99 3.0-3.49 3.5-3.99 4.0-4.49 4.5-5.00
80%
60% -
40% -
20% -
1.0-1.49
1.5-1.99 2.0-2.49
2.5-2.99 3.0-3.49
3.5-3.99 4.0-4.49
4.5-5.00
1.0-1.49
1.5-1.99 2.0-2.49
2.5-2.99 3.0-3.49
3.5-3.99 4.0-4.49
4.5-5.00
FIGURE 8
133
134
GREECE: STATE OF PRACTICE REPORT
MONITORING METHODS AND EQUIPMENT FOR SURFACE DISTRESS AND
BEARING CAPACITY OF ROADS
N.Michas
A.Loizos
GREEK ROAD FEDERATION
67 ZAKYNTHOY, Str. VOYLA
Athens 16673
Greece
tel. (01 )-8950241 -( 01 ) 8991223
fax. (01)-9241863
NATIONAL TECHNICAL UNIVERSITY OF ATHENS
5 Iroon Polytechniou
Athens 157 73
Greece
tel. (01 )-7721341
fax. (01)7721327
1. Bearing Capacity
The Falling Weight Deflectometer (FWD/KUAB) is used for the structural evaluation of asphalt
pavements. The FWD is only used on project level, i.e. there is no operation at network level. The
Deflectometer is mainly used in order to give the practical information to what extent it is necessary to
recommend rehabilitation decisions which have to be made to strengthen the pavement in order to
extend the pavement remaining life. The existing pavement layer thickness is measured by taking
cores.
Several back-calculation techniques are used for the estimation of the existing layer moduli. Laboratory
stiffness measurements using the Nottingham Asphalt Tester are sometimes also used for the "
Calibration " of the back-analysis. The main purpose of the FWD measurements is to obtain the
stiffness moduli of the asphalt layers as well as to evaluate the bearing capacity of the unbound material
of the sub-base, the base and the subgrade layers. Finally the decision for the possible required
strengthening is based on engineering judgement.
2. Surface Distress
2.1 The distress data collection is based upon subjective engineering ratings. This is done only on a
project level basis.
2.2 Developments
A method developed recently by the Laboratory of Highway Engineering of the National Technical
University of Athens ( NTUA ) involves digital image processing techniques to provide suitable digital
imagery input to specialised software developed especially for this project. This software named
APDIS
( Automatic Pavement Digital Imaging System ), determines objectively and fully automatically the
type, the extent and the severity of cracking for flexible and semi-rigid pavements. The developed
method presented substantial agreement, when compared with systematic visual ratings of existing
pavement cracking.
3. Evenness
3.1 The longitudinal unevenness ( roughness ) is measured with the aid of the Bump Integrator of the
Central Laboratory of Public Works (KEDE ).
135
3.1 Developments
The Laboratory of Highway Engineering of the NTUA in co-operation with the KEDE developed a
method which involves systematic subjective panel ratings for the riding quality and roughness
measurements. The method involves also the use of a parameter for needs and repairs and can be
applied by any roughness measuring equipment.
4. Temperature measurements of bituminous layers inflexiblepavements
A temperature recording system has been installed in a flexible pavement, at the NTUA campus,
consisting of 250 mm thick bituminous layer and 150 mm unbound granular material. The system
measures air temperature and temperature in the bituminous layer at 5, 50, 100, 150, 200, and 250 mm
depths in half or one hour intervals,. From the one year data collected, algorithms are developed for
predicting the daily variation of pavement temperature in half hour intervals, at various depths, as a
function of the mean, max and min air temperature. Similar algorithms are developed for the "average "
temperature variation at various depths for each month. This analysis is considered as preliminary and
it will be finalised after collecting data for at least one more year. It is intended to use the results for the
design of the new pavements and for the monitoring of the behaviour of the existing ones.
5. Damage factors of commercial vehicles
Weigh in motion data in more than 20 points of the national highway network have been systematically
collected over the past 5 years. The first data on axle load measurements have been collected with the
use of mats covering one lane at a time. Since 1993 a permanent station covering four traffic lanes has
been installed at strategic points of the national network. Damage factors per type of commercial
vehicle, per axle system and for all the types of commercial vehicles are determined and are used in
pavement design and in estimating the behaviour of existing pavements.
6. Skidding Resistance
Periodical Skid resistance measurements are performed using the ASTM Skid Trailer on main roads
for evaluation purposes. The Skid Trailer is also used in some projects for decision making concerning
rehabilitation or maintenance works.
7. Surface Texture
The surface texture is measured with the use of the Sand Patch Method. The TRL laser texturemeter is
also used for local texture measurements.
136
ITALY: STATE OF PRACTICE REPORT
GROUND PENETRATING RADAR:
THICKNESS MEASUREMENT IN ROAD PAVEMENTS
R BENNETTI
SUMMARY
Accurate knowledge of the thicknesses and properties of the materials which make up road surface and
subsurfaces enables them to be properly maintained and is essential to understand their current state
and future behaviour. Until a few years ago, the only practical way of obtaining the relevant
information was by core sampling. Core sampling is relatively time-consuming, seriously disrupts
normal traffic flows and, last but not least, only give information at the point of coring.
The aim of this document is to see whether fast and accurate information can be supplied by GPR
(Ground-Penetrating Radar) and an automatic or semiautomatic computer analysis of the data obtained.
The radar data were obtained at both low and high speeds up to around 60-65 km/h to assess the
potential problems caused by a gradual increase in speed.
The data were then analysed using a specially developed software which could operate on raw or
filtered data.
After the introduction of appropriate parameters, the program enables a section of the analysed area to
be obtained, highlighting any anomalies and allowing the operator to assess their real importance.
The results of this study showed that GPR data, when properly used and analysed, give extremely
accurate measurements of surfaces and subsurfaces even at high speed and do so quickly, without
major disruption at road or motorway traffic.
1. INTRODUCTION
Radar has been in use since the twenties. Over thirty years ago, the US Army started using a specific
form of radar, GPR, to locate non-metallic mines. The accuracy of the system subsequently proved
useful in geotechnical engineering, archaeology, the mapping of underground objects, etc. For a
number of years it has been widely used to measure the thickness of concrete linings in tunnels,
extrados cavities, honeycombing, humidity, surfaceflaking,etc.
More recently, the need has arisen to investigate road surfaces and subsurfaces. A knowledge of their
make-up can be extremely useful in helping experts to asses the conditions of their roads, and to take
better decisions on planning priorities, repair strategies and operational arrangements: in many cases,
the various road administrations do not know exactly how thick their own roads pavement are (because
of repeated resurfacing) or what state the subsurfaces are in.
Measuring the thicknesses of surfaces is also important in monitoring the construction of new roads
and repairing existing ones.
137
Currently, the only way of obtaining accurate information on the thickness of surfaces is core sampling.
Although accurate, this is a slow process which disrupts traffic flows an uses widely spread samples
thus leaving doubts about how thicknesses vary in between.
The aim of this research is to demonstrate the reliability and practicability of GPR in measuring the
properties of surface and subsurface layers.
2.
TH E PRINCD7LES OF GPR
GPR works by transmitting short pulses of electromagnetic energy through materials using an antenna
mounted on a vehicle or guided manually over the target area
The amplitude and frequency with which the pulses are reflected gives an indication of the position and
type of dielectric discontinuity in the materials (air/asphalt/stabilised earth, etc.).
The reflected energy is picked up by the antenna's receiver, amplified and displayed on hard copy or
monitor and stored on an appropriate magnetic medium.
Antenna
Voltage
Reflected
φ
rays
Surface
<2H
Æ
pgi.
®,
%
Time <ns)
Figure 1 ­ shows a typical, condensed example of the types of wave which can be detected during
monitoring.
The thickness of surface an subsurface layers and their properties can be calculated by measuring the
arrival times and respective amplitudes of the relevant wave peaks.
The journey time of the pulse reflected by one layer together with its dielectric constant determines the
thickness according to the equation:
thickness = velocity χ (time/2)
As the time between two peaks represents the outward­and­return journey of the pulse, it must be
divided by two.
138
The velocity of the radar pulse can be expressed using the dielectric constant of the medium, ε, as
follows:
speed = 30/Ve (centimetres per nanosecond)
where 30 is the speed of the electromagnetic waves in space (in cm(nanosecond).
When an electromagnetic wave hits the boundary between two substances with different dielectric
constants, part of the wave carries on into the underlying substance while the rest is reflected or
scattered in other directions.
If both substances have similar dielectric properties, most of the energy crosses the boundary and a
small amount is reflected. Conversely, if the dielectric constants are very different, most of the energy
is reflected and only a little amount crosses into the adjacent material.
Table 1 gives the dielectric constant values for those materials most frequently used in roads and
motorways. The largest difference is between air (ε =1) and water (ε,=81). All other values fall in
between and vary according to the type of inert substance used, the density, the bonding agent, density
or permeability and whether or not the voids contain water (i.e. moisture content).
Table 1 - Representative dielectric
constants for construction materials
Material
Dielectric
Constant ε,
Air
Water (fresh)
Water (salt)
Sand (dry)
Sand (wet)
Silt (wet)
Clay (wet)
Ice (fresh water)
Granite (dry)
Limestone (dry)
Portland Cement Concrete
Roller-Compacted Concrete
Asphaltic Concrete
1
31
31
4-6
30
10
8-12
4
5
7-9
6-11
5-7
35
Another factor to be considered is resolving power, i.e. the relationship between the wavelength and
frequency. While the speed in a medium remains constant, this relationship is an inverse one.
Resolving power depends on the wavelength: smaller wavelengths can discriminate between smaller,
thinner anomalies while larger ones penetrate further but only resolve bigger discontinuities.
However, in road surface measurement, penetration is hardly ever a major problem as analysis is
limited to sections close to the top. At high frequencies, penetration is shallow (about 0.8-1.0 m for a
900-1000 MHz antenna) while the resolving power high. At low frequencies, penetration is deeper (1040 m with a 100-300 MHz antenna) and the resolving power lower.
139
1. DETERMINING VELOCITY
The procedures for determining velocity are either direct or indirect.
Not surprisingly, direct procedures include bore-sampling for calibration purposes, artificial and/or
natural excavation and the ability to detect an object buried at a known depth.
Of the indirect methods, the most common is of course that based on the CDP (Common Depth Point),
used in the seismic reflection method (also known as WARR or Wide Angle Reflection and
Refraction). However, two basic conditions must be met if this method is to be used: the reflector must
be level and two separable (bistatic) antennae must be used.
Another system requires only on antenna but a target point (a different point in the plan of survey) is
also needed. This can be a stone, a pipeline or any obstacle producing reflections which behave as
though they comefroma point of diffraction.
A newer method is to determine the dielectric constant experimentally of the medium in situ. It is
directly related to the transmission velocity in the medium itself.
1 Indirect methods
CDP, or WARR, is already a measuring technique in itself although there are limits on the distance
between transmitter and receiver. It is widely experimented with and used in reflection seismology but
does, in the case of shallow GPR measurements like those used to check the thickness of road
pavements or tunnel linings, present practical problems which very often detract from its usefulness.
The main difficulty is the positioning of the antennae with respect to each other. As the thicknesses
being checked are small, even slight positioning errors can cause major percentage differences.
3.2 Analysis of direct methods
The only problem with direct methods (calibration bore-sampling, excavation, etc.) is carrying them
out. For limited depths, however, both time and costs are reduced drastically.
Major advantages with the direct method come when the carefully calculated results of the readings are
interpreted. In types of concrete, we often come across areas with large voids, layers put down at
different times, and other anomalous situations which are unlikely to show consistent features.
We can therefore confirm that each has pros and cons, which have to be weighed up on a case by case
basis.
In the case of detailed readings on concrete structure, the best method, is direct calibration bore
sampling with appropriate checks. Where, for particular reasons, this is not feasible, indirect methods
should be used particularly the CDP, which is one of the most sensitive.
2.
RADAR MONITORING OF ROAD PAVEMENTS
Ground Penetrating Radar has been increasingly used in the last few years for monitoring road
pavements in either bituminous or concrete mixes, as it allows information to be acquired rapidly and
economically on both the bituminous or concrete coating and on the conditions of the materials
immediately below it.
140
Radar monitoring ¡s to be understood as an extension of the widely used surface distress measurements
(SCRIM, etc.) and bearing capacity monitoring, (FWD, etc.). It can provide all the information on
dimensions and quality concerning the body of the structure, as it completes the diagnostic picture of
the state of the surface which up to now was determined by means of periodic coring.
The thicknesses of the various layers are calculated automatically by computer using a special software
which measures the times of the phase front corresponding to the reflection concerned and multiplies
them by the different speeds of propagation in the specific materials.
Using the same principle of reading but by means of direct interpretation of the signal, it is possible to
identify, locate, and measure all the anomalies or discontinuities inside the pavement, which can be
identified as secondary reflections of the signal; specifically, it is possible to identify such phenomena
as segregation of the mixture, fillings with cold mixtures, deterioration, etc.
The above also applies to the sub-base, where segregation of the material and/or concentrations of
dampness or clay are normally easily located, as they cause a significant intensity.
Experience gained in this field by SINECO has led to the definition of two different types of
monitoring for application on a commercial scale: the first is carried out at a speed of 60-65 km/h; the
second at 20-25 km/h. In both cases, it is normally sufficient to acquire simultaneously two longitudinal
profiles per lane, in this way providing an extremely complete mapping of the lane examined in a single
pass.
In the first case, with a vehicle running at a speed of 60-65 km/h, disturbance to normal traffic
circulation is not excessive and the minimum distances of the measuring points that can be obtained
range from 12 to 20 cm, depending on the output scans defined. In this case, definition of the
thicknesses has usually an accuracy of 10% up to 5% in best cases. With this acquisition speed,
monitoring can be extended without difficulty up to a depth of about 1 m from the pavement surface,
with good identification of the underlying layers (sub-base and subgrade). Note, however, that the
definition that can be obtained at this speed makes it difficult to identify, within the layers, anomalies
that are shorter than 100 cm.
In the second case, with the acquisition vehicle running at a speed of 20-25 km/h (normally used when
higher definition of the pavement and the underlying layers is required), the measuring points that can
be obtained vary, having a minimum distance of 4 cm and a maximum of 8 cm, depending on the output scans defined. Also in this case, the accuracy of the definition of the thicknesses is in the region of
5%, but at this acquisition speed it is normally possible to identify anomalies with a length of about 3040 cm within the layers and up to a depth of about 1.5 m.
The results of the survey are normally provided both in the form of longitudinal profiles and as printed
reports. The profiles graphically show the thicknesses monitored and the anomalies found: the printed
reports give the thicknesses found and their mean values for defined lengths; the mean values of the
entire survey, with the mean quadratic rejects deducted; and the position and extension of anomalies,
both as regards the pavement and the underlying layers since all the information processed are in digital
form, automatic integration with the results of other types of monitoring would not present any
technical difficulty.
141
The most recent applications of radar monitoring along a number of short stretches of Italian
motorways were aimed at identifying and defining causes of degradation and deformation of the
pavement. In this specific case, simultaneous monitoring of two profiles was carried out at a translation
speed of 20-25 krn/h, with 500 MHz antenna at a height of 3-4 cmfromthe pavement.
The results obtained, which were subsequently checked by means of coring, have made it possible to
confirm that the differences in the thicknesses between the interpretation of the radar signals and direct
measurements were kept below 4%, and that identification of the underlying layers using radar
matched that checked using the direct method.
While the above surveys were being made, an attempt was also made to locate cracks in the pavement,
obtaining satisfactory results in the case of cracked areas where the progress of the fractures was not
developed parallel with the electromagnetic wave. In some zones, water was found to be present
between the pavement and the sub-base; this was the probable cause of cracking, due to the pumping
effect.
Radar monitoring makes also possible to identify the presence of service lines (electric cables,
telephone lines, etc.) which, if not located accurately, could present considerable difficulties when the
pavement has to undergo maintenance.
From the experience gained to date, radar monitoring of pavements and the sub-base has been shown to
be capable of making an effective contribution, at very limited cost, to traditional monitoring systems,
and thus makes it possible to develop increasingly effective programs for the maintenance of motorway
pavements.
3.
DATA ANALYSIS
The software devised and developed to analyse the data is designed principally to locate and map the
thickness of road surfaces and to locate any layers under the surface and at the juncture between the
stabilised earth and the materials in place.
The program requires the operator to definer the horizon (level) to be followed, either by mouse or
keyboard. The system then takes over and only stops when the optimum conditions are no longer met.
In such cases, the program again allows the operator to step in to work out the cause of the anomaly
and decide whether to go on, stop or work manually on the values.
The procedure can be carried out on a number of surfaces and/or occasions using different search
values depending on the characteristics of the data in question.
142
Progr.
Km
Pavement
Thicknesses
medium
min.-ma«. |
Subbase
Thicknesses
medium I
min.-max
To(51
medium I
Thicknesses
Anomalis sones
73*150
79.100
min.-max. |
Ι
73.200
73*221
24
2 ,-2t
20
|
21-24
51-40 I
54-47
5',
70
74-«
ΓΛΊ
|
«
85
| 77-»*
I
1^21
|
17-23
I
I
40
I 33-43
5«
I 50-S4
^
I
20-22
24-31
I
4*
I
2»
I 44-51
ESSSSEg
ΙΛΝ
I
1S-21
23-33
I
1S-21 I
23-34
I
34-47
I
42-55
4*
I
4*
|
41
I
70
I
43-52
I
53-4*
2Í
2*
I 43-54
21
I
^
ΖΣΠ.
20-23
49
41
I 43-74
^
Figure 2 - interpretation reached at the end of the analysis
' " I I j F i i4fi'*Jlf t 'írf 1 li
'
0.25
0.50
-'
ïf/fr^Wsr
Figure 3 - radar substructure with the interpretation superimpos8d.
143
I-
4.
CONCLUSION
The results obtained both in the first phase of experimental tests and from actually using the
measurement and recording system make a significant contribution to the upkeep and management of
roads an motorways.
Clearly, then, with the above methods, this system enables long stretches of highway to be
automatically surveyed and recorded quickly and cheaply.
Remembering that until now the only feasible system for calculating road surface thicknesses has been
core sampling, which disrupts traffic and gives only point-specific results, the radar system opens the
way for continuous, non destructive testing along the whole stretch but does not interfere with traffic
flows.
More especially, the use of radar measurements for monitoring road an motorway networks enables the
physical characteristics of surfaces, foundations an subfoundations to be determined. This means that
physical and geometric parameters can be worked out for one-off road maintenance work such as
structure reinforcing before the structure itself is damaged beyond repair. It also enables the road
authority to make preventive forecasts.
144
THE NETHERLANDS: STATE OF PRACTICE REPORT
MONITORING EQUIPMENT
BEARING CAPACITY
FOR
SURFACE
DISTRESS
AND
BERT DE WIT
Road and Hydraulic Engineering Division,
October, 1996
1. Introduction
In the Netherlands two pieces of equipment are used for collecting data on surface distress and on
the bearing capacity: the Automatic Road ANalyzer (ARAN) and the Falling Weight Deflectometer
(FWD). These pieces of equipment are in full operational use. Research is carried out in order to
increase the productivity of the methods.
2. Bearing capacity
2.1 Present data collection
The FWD is used for evaluating the bearing capacity. The purpose of this use is to be able to
reliably state to what extend it is necessary to recommend rehabilitation measures which strengthen
the pavement. FWD-measurements are carried out in the case of signs of distress on the surface of
the pavement. There are in general three categories, namely:
• signs of structural distress (e.g. cracking), these are related to the load-bearing capacity of the
pavement;
• signs of functional distress (e.g. cracking and ravelling), these are related to aspects of traffic
safety, traffic flow and travelling comfort.
The purpose of the falling weight deflection measurement is to obtain: the stiffness modulus of the
sub-base and base course; the effective thickness of the pavement layers, or the rigidity modulus of
the pavement layers; whether a number of layers are lying loose on top of each other.
The FWD is only used on project level because the instrument can not operate at high speed. At
network level, the FWD-measurement is a time and cost- consuming operation.
2.3 Developments
DWW is not involved in the development of high speed measurement equipment for road deflection.
3. Surface distress
3.1 Present use
DWW uses the ARAN measurement vehicle for collecting surface distress data. In 1996 DWW
purchased a new, upgraded ARAN to replace the old ARAN from 1988.
The ARAN is an integrated measuring system. Several characteristics of roads, such as longitudinal
and transverse unevenness, texture, surface distress, superelevation and gradient are measured
simultaneously with ARAN, which is equipped with ultra-sonic and laser distance meters,
145
accelerometers and video cameras. These measurements are performed at a variable speed up to a
maximum of 90 km/h.
The road picture and the visible damage to the road surfaces are recorded using a video-logging
system in combination with artificial (strobe) lighting. The video-logging system of the ARAN is
fitted out with the following equipment:
• one right of way camera (shutter speed of 1/2000 s, (horizontal) resolution 625 TVL); one
SVHS-video recorder (resolution 460 TVL);
• one monitor (resolution 600 TVL);
• 2 pavement camera's (shutter speed of 1/31,000 s, picture elements (hxv) 756 χ 581); sensitivity
0.5 lux);
• two SVHS video recorders (resolution 460 TVL); two monitors (resolution 600 TVL).
Two people are required to operate the ARAN measuring vehicle: one driver/measuring officer and
one team leader. Data collection is made efficient by combining various measuring systems in a
single measuring vehicle. Approximately 400 kilometres of lane length can be measured daily.
Because of the variable measuring speed of up to 90 km/h at which ARAN operates, little or no
obstruction to traffic is caused by the system. In addition, video logging also excludes the
disadvantages of visual inspection on foot, such as unsafe methods of working (inspectors often
walk without closing off traffic) and disturbance to the level of service (if a lane is closed).
The measured data can be processed in the office by one or more people. Processing involves the
calculation of indicators per 100m road section length and the preparation of reports and database
input files. Around 50 km road length can be processed per man-day.
The video recording of the visual damage to the road surface can be processed manually or
automatically. Manual processing of the video pictures is labour-intensive. A maximum of 15 km
can be processed per man-day. In addition, the interpretation of the video-films is a demanding job.
To overcome these problems, an image processing system (so called WISECRAX system) is
acquired for automatic distress evaluation.
The ARAN measurements are used for:
• Multi year planning. The longitudinal evenness and rut depths of the motorway network are
measured periodically (total length 2 χ 2500km). Surface distress is also recorded and
processed.
• Project planning measurements. These measurements are performed to provide information on
any pavement maintenance required.
• Measurements for research purposes. Research is conducted for example on the use of ARAN
profile data for the re-profiling of roads.
• Compilation of an inventory of location data using video-logging.
3.2 Developments
At this moment DWW is investigating and, if necessary, improving the capabilities of the videologging system for the assessment of surface distress. Especially the following elements are under
research:
•
Strobe lighting. Video images that are taken using daylight are disturbed by the variable amount
of sunlight. Strobe lighting solves this problem.
146
•
•
•
High resolution line scan camera's (> 1000 pixels per line) for the recording of small cracks
(Dlmm);
Digital recording instead of analogue recording;
Image processing techniques (e.g. segmentation, edge detection, auto-correlation).
It is expected that the first results of the research will be reported in 1997.
147
148
PORTUGAL: STATE OF PRACTICE REPORT
MONITORING METHODS AND EQUIPMENT FOR ROAD SURFACE MONITORING
MARIA DA CONCEIÇÃO MONTEIRO AZEVEDO, LNEC (National Civil
Engineering Laboratory)'", Lisbon, Rui Barros, JAE (National Road Administration), Lisbon
1 - INTRODUCTION
The main road network in Portugal has a length of about 10 000 km. JAE - the Road Administration manages 9 500 km and BRISA, the Motorways Administration, manages about 500 km. This road
network involves about 9 500 km offlexiblepavements (98%), and about 140 km of rigid pavements.
All of the road maintenance is carried out by the road administrations with their own resources. In the
last few years JAE ordered to a private company, under its supervision, a pavement maintenance
management system (PMMS) of the road network. That PMMS includes pavement maintenance
planning and therefore also require traffic data information and information concerning surface
condition as well as the structural condition of the pavements.
Nowadays, the Ministry of Public Works is intending to change the traditional way of road
construction and maintenance to a DBFO - Design, Building, Finance and Operate - system.
2 - SURFACE CHARACTERISTICS
The survey operations start with a visual inspection to identify the type and level of surface distress. At
project level the visual inspection is carried out on foot, but at network level it is carried out by car and
the data is stored in a portable PC - DESY system (LCPC-TRONICO).
The other characteristics measured are roughness and transversal evenness, skid resistance, and surface
texture of the pavement.
The devices used to evaluate the roughness are the Wisconsin Road Meter and the APL profilometer
and for the latter an index based on CAPL coefficient is used to define the level and severity of
evenness. The transversal evenness is measured with stationery devices, like straight-edges and a
Wauquier profilometer (a French device), to determine the incidence of rutting and water depth.
The skid resistance is evaluated with the Mu-meter device, mainly used for airport runways and for
research purposes, a SCRIM is used for network level. The tests are to be performed on wetted
pavements and measurements with the Mu-meter are carried out with a 0,5 mm of water film and a
fixed speed of 40 or 60 km/h.
The surface texture is evaluated with the sand patch method, according to ASTM E 965.
Traffic noise is an issue which is gaining more and more importance. In pavements with porous
bituminous mixtures and bituminous thin layers, measurements of tyre/road noise are carried out.
149
Those functional data are collected from readings made in the wheel tracks, mainly in the outer-lane.
On motorways and dual carriageways, the fast lane is also monitored in the same manner.
There are four quality index corresponding to four classes of severity (longitudinal evenness, transverse
evenness and skid resistance) at the Portuguese PMMS.
The second phase includes the feeding of the Data Base and the Management System where the main
parameters regarding the pavement condition need to be observed. In this phase, the main purpose is to
follow-up the evolution of the pavements behaviour throughout their life period. For status parameters
such as surface condition, skid resistance (SCRIM) and roughness (APL), a periodic surveying in the
whole network extension is foreseen.
The surveying interim could vary between 2 years for the surface condition and 4 years for the
roughness and skid resistance, but different intervals should be adjusted to each particular evolution
periods.
3 - STRUCTURAL CHARACTERISTICS
At present and up to now in Portugal, monitoring structural characteristics of roads is obtained by
evaluating the bearing capacity of flexible pavements. In the case of rigid pavements the assessment is
done by measuring relative slab movements at joints with specific equipment developed at LNEC.
Nowadays the axle load of 80 kN is recommended for flexible pavements and the load of 130 kN is
recommended for rigid and semi-rigid pavement structures.
The equipment used at project level are the Benkelman beam and FWD - Falling Weight Deflectometer
(KUAB and DYNATEST). The former ones were used mainly in the sixties, and for over twenty years,
and the latter ones since then and up to now. The Portuguese version of the Benkelman beam, adapted
for registration of the influence line of deflections induced by the truck's rear axle, allows therefore the
recording of the entire deflection bowl, on a length of 250 cm, instead of the usual maximum
deflection.
At network level, because FWD is a time and cost-consuming test, measurements with Lacroix
deflectograph are carried out periodically, every two years, since 1990.
Monitoring is carried out, mainly, on overlays and rehabilitation pavement projects and research
purposes, but also on network level. In the particular case of research, bearing capacity measurement
has contributed to setting up the methodology for monitoring pavement trial sections and for overlay
design.
At network level, within the last five years, measurements have contributed to determine the actions for
road strengthening.
The survey starts with a visual inspection of surface distress condition and simultaneously with the
bearing capacity tests temperature of the air and of the pavement surface are stored, at least every half
of an hour. The aim of visual inspection is to provide complementary data to the deflection
150
measurements to the diagnosis of the probable causes of surface defects and deflection deficiencies to
where they appear. It is also intended to discriminate surface distress from pavement layer structural
deterioration.
Emphasis is laid on the results of visual inspection and on results of bearing capacity. After that, a
criteria of homogeneity is applied and a division of the test section into homogeneous subsections is
done. After that a coring drill is carried out to define the thicknesses of the different layers of the
pavements and to collect samples to laboratory tests. These information helps the data interpretation
and a more accurate back-calculation of the materials moduli.
Combining bearing capacity evaluation with past service life expressed trough cumulated standard
axles or commercial traffic, makes it possible to calculate the remaining service life - residual lifetime of the pavement structure.
The Benkelman beam is associated with an instrumented truck intended for measuring pavement
deflection under a moving wheel load. The rear axle load is usually 90 kN, but can easily vary from 80
to 130 kN. Tests are performed along the outer wheel path, in points located every 50 to 200m. It
allows an easy measurement of the deformation of the pavement along a wheel track, starting one meter
in front of the moving twin-wheels load and ending three meters behind the wheels (entire deflection
bowl).
At project level FWD tests are executed at 50 to 100 m intervals in both sides of the road, staggered by
25 or 50 m, according to the purpose of the study, length of the section, surface distress condition and
importance of the road. For short length pavements or trial sections the spacing can be reduced in such
a way that every section contains the sufficient number of points to enable a statistical analysis. The
equipment existing in Portugal allow for the measurement of 7 deflections, positioned from 0m to 2,5
m, from the centre of the loaded area. There are two possible loading plate diameter, used according to
the type of pavement studied: a 30 cm diameter plate is used for road pavements, and a 45 cm diameter
plate is used on airport pavements. For road pavements, the peak load applied is generally between 45
kN and 65 kN: for airport pavements, the maximum peak load (150 kN, in the case of LNEC's
equipment and 240 kN in the case of a private company) is used. On road pavements, tests are
performed in each direction, in points along the outer wheel paths.
Additionally, the traffic data is acquired by regular manual traffic counting and supplemented
monitoring by a network of automatic counting and weigh-in-motion station on complementary
positions. From these automated stations, statistics are derived on parameters in proportion to vehicle
classes, class of road and datafluctuationthat enable up-calculation of a more accurate traffic data from
the manual counts. Traffic data is usually used for evaluation of the above structural monitoring data.
The data collection methodology is the same for the surface characteristics, described in item 2. In what
concerns deflection surveying, network representative samples should be defined, based upon the
results from the first action to carry out over the whole network, with a 25% sampling percentage. The
deflection surveying will be made periodically on these samples.
151
The surveying scope will include three areas within JAE:
a) periodic survey to feed the Data Base PMMS;
b) the survey of the new network pavements, both newly built-up or strengthened pavements, and;
c) research studies within a protocol with LNEC (National Laboratory of Civil Engineer).
4 - REASONS FOR INNOVATION
It was felt that in Portugal the monitoring methods used for structural characteristics evaluation could
not meet the new challenges that require to speed up monitoring and to increase measurement
sensitivity.
The needs for innovation are:
•
•
•
•
•
full coverage at network level in a short period of time;
surface characteristics measured by laser technique;
integration of other measurement equipment to upgrade deflection measurements to a
multifunction device;
computerised visual inspection or video image recording that could storage the type, level of
severity and length of surface distress, during survey operations, in order to avoid loss of time and
possible human error in manual recording.
survey operations in combination with GPS (Geographic Positioning System), in order to provide
accurate positioning of the local of measurement, using navigation satellites, and the possibility to
draw maps of the travelled road section, that can be correctly overlaid.
REFERENCES:
1] -
Azevedo, M. C; Antunes, M. L. - «Auscultação de Pavimentos- Aspectos Mais Importantes».
Paper presented to Ordem dos Engenheiros Congress. Coimbra, 1991, (in Portuguese).
2] -
JAE/LNEC - «State of the Art Report. Road Pavement Maintenance». Third SPRINT
Workshop, Exhibition and Demonstration on Technology Transfer and Innovation in Road
Construction, Barcelona, 1994.
3] -
Pereira, P. et al - «Informe Nacional de Portugal». Artide presented in CARRETERAS
Review, n° 75. Madrid 1995, (in Spanish).
152
SLOVENIA: STATE OF PRACTICE REPORT
ROAD MONITORING EQUIPMENT
ALES HOEEVAR, BOJAN LEBEN and JANEZ TOMSIE
Dru_ba za dr_avne ceste
Engineering Company for Public Roads
(an "executive agency" of DRSC and DA RS)
and
ZAG - National Building and Civil Engineering Institute
1. Introduction
Transport and roads fall within the jurisdiction of the Ministry of Transport and Communications of the
Government of the Republic of Slovenia. The Ministry also governs railway transport, post and
telecommunications, and maritime and air transport. Within the Ministry, the sphere of roads is the
responsibility of the Directorate of the Republic of Slovenia for Roads (DRSC), an expert service
which prepares and oversees the implementation of programs of construction, rehabilitation and regular
maintenance, and all other developmental and professional tasks concerning roads.
For the purpose of completing the motorway network (the total planned length is 663 km), the
Government established the Motorway Company in the Republic of Slovenia, DARS d.d. It is a public
shareholding company owned by the state, whose tasks are the preparation, organisation and
management of all construction and maintenance works on the motorway network.
Primary (National) Road Network
Pavement Type
flexible
composite
rigid
gravel
Total
(*) with stabilised layer
Motorways
Main Roads
1,283 km
Regional Roads
2,987 km
* 202 km
4 km
73 km
206 km
1,356 km
9 km
400 km
3,396 km
2. Pavement Monitoring
Transverse and skid resistance are both regarded as being very important criteria for assessing
road/traffic safety. Longitudinal evenness is more associated with driver's comfort than road user costs
on the national road network. Other pavement monitoring activities (visual surveys and structural
evaluation) are performed with the primary intent of determining the expected service life of the road.
Furthermore, roads are roughly prioritised for necessary rehabilitation or maintenance measures on the
basis of visual distress surveys (as part of an initial assessment that is to be followed-up by other
monitoring activities).
153
Surface Distress
The condition of the pavement surface is assessed by subjective means. Visual inspection is carried out
from a vehicle equipped with an odometer and a PC. A program pre-processes the stored data (distress,
chaînage, etc.) and makes it available for further analysis.
The ARAN multi-functional survey vehicle was also used at two occasions on our national road
network. The post-processing of video images proved to be quite laborious and the interpretation was
often difficult due to variations in light along the road surface (as a result of time of day, location,
material type, etc.).
Bearing Capacity
The Lacroix deflectograph has been traditionally used for assessing the structural condition of roads. In
1995, the Falling Weight Deflectometer was introduced to enable a more detailed structural evaluation
of pavements. Measurements are performed both at network and project level.
Longitudinal and Transverse profile
The ELE profilograph has been used for the assessment of road unevenness. The evenness of the
national road network was also assessed using the ARAN multi-functional survey vehicle. The
national institute ZAG has just completed the construction of a device for measuring the longitudinal
road profile. Additional information on this device is provided in the appendix to this document.
The ZRMK profilograph (straight-edge technique) is used to assess the transverse profile of roads.
Skid resistance
Skid resistance measurements at the network level are made using the Saab Friction Tester. The
portable Skid Resistance Tester is also used for site investigations. A programme of measurements is
planned for 1997 using the newly purchased SCRIM device.
The ZAG-VP Longitudinal Profilometer
A longitudinal profilometer for measuring the longitudinal profile of road pavement surfaces and
for the evaluation of the results obtained has been developed at ZAG Ljubljana for determining and
monitoring the condition of Slovenia's network of state roads. This equipment works by measuring
the vertical accelerations at a reference point on the chassis of a normal passenger car travelling
over the road surfaces to be measured. At the same time the equipment measures the vertical
distance of this reference point from the road surface by means of a contactless angular measuring
device. After the results have been processed, they consist of records of the longitudinal profile of
the road pavement showing waves lengths from 0.8 to 30 m. Of course these results can be further
processed, so that, for individual road sections, various indices such as the IRI index recommended
by the International Bank for Renewal and Development, can be calculated. The measurements can
be carried out using car speeds suitable to the category of road involved, under normal traffic flow
conditions.
154
The results of measurements on a number of different road sections, and a comparison between these
results and those obtained by rod and level measurements show very good correlation.
During the first stage of measurements, the results of the analysis of longitudinal vertical profiles have
been based on the use of the IRI index which is used by the Road Directorate of the Republic of
Slovenia. While taking into account the instructions of the IBRD for the calculation of this index, we
found that this index is notflexibleenough for all kind of analyses.
Some experts from FEHRL laboratories were asked to make interpretation of longitudinal profile
measurements on one test section and results showed differences in the presentation that lead us to an
conclusion that an harmonisation experiment is needed.
155
156
SPAIN: STATE OF PRACTICE REPORT
ROAD MONITORING EQUIPMENT
M.D. CANCELA REY and G. ALBRECHT ARQUER
1.
INTRODUCTION
There are 160,000 km of roads in Spain. The Ministry of Development manages the 22,500 km which
support 80 % of the heavy vehicles in Spain. The rest of km are managed by Regional (autonomic) and
Local governments. That main network includes 6,000 km of motorways, 1,800 km of which are toll
motorways.
In the last few years the Ministry of Development, as a pioneer, has changed the traditional way of
road maintenance in which all the routine maintenance was carried out with their own resources. The
new methodology of road maintenance, called Integral Maintenance, is recommended to private
companies under the supervision of the Ministry. These companies are in charge of all the routine
works: winter maintenance, inventory works, even road monitoring. Until now this experience
involves 4,000 km.
Following this experience, due to the good results obtained up to the moment, Regional governments
begin to make contracts on the same way.
One of the most important problems related to Road Monitoring in Spain is the semi-rigid pavements,
with cement treated bases and subbases. These types of pavements are near to 40 % in the National
Network. The concrete pavements are about 10 % in this network. Finally the 50 % are bituminous
pavements, more of them are flexible, but there are some of them with more than 20 centimetres of
bituminous mixes. It is well known that the semi-rigid pavements exhibit different parameters when
they are monitored by usual equipment because of that it is needed to develop different approach
models to analyse the results of data collection.
2.
ROAD MONITORING
The present methods and devices which are used at the moment in Spain for road monitoring are now
described. They will be separate into three categories:
1. Surface characteristics
2. Bearing capacity
3. Distresses analysis
2.1
Surface characteristics
The surface characteristics includes the evenness: transversal and longitudinal, the skid resistance and
the texture. In the next paragraph are described the index, devices, normative and solutions that can be
used commonly in Spain to correct the problems.
157
Longitudinal evenness
Index:
Devices:
Normative:
Solutions:
Transversal evenness
Index:
Devices:
Normative:
Skid resistance
Index:
Devices:
Normative:
Solutions:
Texture
Index:
Devices:
IRI
Calculated every 1 m with data of 100 m
Dipstick (Roads under construction)
Response devices (APL, ARS)
Laser profilometers (RST, KJLAW, MRM)
New Roads 50 % length with IRI< 1.5
80 % length with IRI < 2.0
100% length with IRI< 2.5
Old roads
No normative
Milling or extension of an overlay
Rut depth, in centimetres
The calculation of the index depend on the
type of road and the extension of the problem
Laser profilometers (RST, KJLAW)
No Normative
Actually rutting is not an usual damage of
the Spanish roads. In the middle of 70's the
Spanish regulations changes the types of
mixtures to solve this problem, and the
solution has behave satisfactory.
Side Force Coefficient (SFC)
SCRIM
Mu meter devices for airport runways.
Also occasionally is operating at Spain a Grip Tester for
Longitudinal skid resistance.
No Normative
Every two years The MOPTMA surveys all its network
with the SCRIM. Normally when SFC < 40 a surface
treatment or the extension of a new layer is carried out.
Sand Patch Index (SPI)
Sand Patch Method
Laser Texturemeters which simulate the Sand Patch Index continuously along the road
Normative:
New Roads It is required SPI > 0.7
Old Roads
No Normative
An alert value is SPI < 0.5
158
2.2
Bearing Capacity
The bearing capacity can be expressed in terms of deflections. When the modulus are desired it is
necessary the use of backcalculation models for which the thickness of the different layers is required.
The thickness evaluation can be done by boreholes or by others devices in example the ground
penetrating radar.
Deflections
Devices:
Normative:
Thickness and pavement analysis
Devices:
Normative:
2.3
Benkelman beam like pattern.
Lacroix Deflectograph, Curviameter and Falling Weight
Deflectometers (DYNATEST and KUAB).
There is a Ministry standard which regulates the analysis
of the pavement bearing capacity, overlays and
rehabilitation studies. It is based on the Benkelman beam
and the Lacroix Deflectograph. This standard is under
revision and in future will take into account new
measurement devices.
In 1993 the Spanish Administration carried out a
comparison research in order to harmonise the
measurements provided by the Curviameter, the Lacroix
Deflectograph and the Benkelman Beam. The results of
this research has been successfully and promises a lot
about the curviameter.
Ground Penetrating Radar (GPR)
No Normative
Normally is used in combination with any device able to
measure deflections. It helps a lot to their interpretation
and makes possible a more accurate backcalculation of
the module with the data obtained with the Falling
Weight Deflectometers.
Distresses Analysis
The distress analysis can be done by visual or image analysis.
Visual Inspection
It has been used in Spain for thefirsttime in 1924.
Due to the heavy work it takes not always had a
continuity. Nevertheless at this moment the
Ministry of Development is making a big effort in
order to realise annual reports systematically. Since
1990 the Ministry started with a standard procedure
for the annual visual inspections on some selected
roads.
159
Image analysis
Devices:
GERPHO and Video Systems
They are used for specific works, no as routine road
monitoring.
GERPHO analysis is a heavy duty and the results with
the Video Systems is not as good as it is required.
160
SWEDEN: STATE OF PRACTICE REPORT
METHODS FOR THE HIGH-SPEED MEASUREMENT OF SURFACE
CHARACTERISTICS AND ROAD SURFACE DEFLECTION UNDER A MOVING LOAD
By Georg Magnusson, Swedish Road and Transport Research Institute, S-581 95 Linköping, Sweden.
Introduction
Sweden uses high-speed measuring equipment for the measurement of a number of road surface
characteristics. For the measurement of road surface deflection under load a stationary dynamic device
is used, while a new device for the high-speed measurement of road surface deflection under a moving
load is under development. Finally, a new device for high-speed detection and evaluation of surface
distress also is being developed.
The Laser Road Surface Tester (Laser RST) is used for the measurement of the longitudinal and
transversal profile (including crossfall), macro- and megatexture, grade and horizontal curvature. To
some extent also cracking can be monitored with the existing system. For the measurement of road
friction two instruments measuring according to the skiddometer principle, i.e. measurement of
longitudinal friction at constant slip, are used. The bearing capacity has for years been calculated from
measurement of road deflection using the Falling Weight Deflectometer (FWD).
Measurement equipment
Surface characteristics
Laser Road Surface Tester
The multipurpose measurement vehicle Laser Road Surface Tester (Laser RST), developed by the
Swedish Road and Transport Research Institute (VTI), is based on an American van and extensively
used for road surveying in Sweden and several countries all over Europe as well as in the United States.
The measurement of the longitudinal road profile is carried out basically according to a method
developed at General Motor Research in the beginning of the 1960's, however with certain
modifications and improvements. This method involves continuous measurement of the distance
between the measurement vehicle and the road surface when the vehicle is driven along the road to be
measured. The distance measuring device in the Laser RST application is a distance measuring laser
(laser range finder) and the signal obtained represents the longitudinal road profile as seen from the
measurement vehicle. In order to be able to transform this profile to an earth fixed co-ordinate system,
information about the vertical movements of the laser is needed and this information is obtained by
means of an accelerometer mounted on top of the laser. By adding the first derivative of the laser signal
to the acceleration signal integrated once the slope profile is obtained. A final integration of the slope
profile gives the elevation profile. The slope profile and/or the elevation profile can subsequently be
used as a basis for the calculation of any road unevenness measure. Two profilometers of this type are
used on the Laser RST thus enabling the measurement of two longitudinal profiles simultaneously, e.g.
one in each wheel track.
The cross profile is measured using eleven laser range finders mounted on a beam across the front of
the measurement vehicle. Although the width of the vehicle is restricted to 2,5 m the measurement
161
width is 3,2 m using lasers angled 45? to the vertical on each side of the vehicle. For special
measurement tasks the number of lasers can be increased to up to 20, enabling a measurement width of
up to 4 m, still within a vehicle width of 2,5 m. The crossfall of the road is measured by means of an
inclinometer, the output of which is corrected for the effect of lateral accelerations when measuring in
road curves.
The macrotexture as well is measured by means of distance measuring lasers and reported in the form
of RMS­values and divided into fine macrotexture with a wavelength from 2 à 3 mm, depending on
measurement speed, and up to and including 10 mm and rough macrotexture with the wavelength
range 10 to 100 mm. Also the megatexture, wavelengths in range of 100 ­ 500 mm, is reported.
Road surface cracking can to a certain extent be detected using lasers but as normally only four lasers
are used the chance of detecting existing cracks are somewhat limited. Anyway, in some cases rather
satisfactory results have been obtained.
Horizontal curvature is measured by means of an electronic compass while grade is measured by means
of an inclinometer. In the latter case the signal is corrected for errors resulting from longitudinal
accelerations of the measurement vehicle.
Travelled distance is measured by means of a pulse generator, giving 2500 pulses/revolution, mounted
in one of the non­driven front wheels of the van. The use of "Navigation Satellite Timing and Ranging
Global Position System" (Navstar GPS) for localisation purposes is being studied.
Skiddometers
For surveying and control purposes a small trailer, called BV11, is used. It was originally developed for
measurement on airport runways but has subsequently been adapted for road use and measures at a
constant slip value of 15%. The size oftest wheel is 4.00­8«.
The measurement vehicle BV12 is intended for research and is based on a lorry. Road friction can be
measured at variable slip values ranging from ­3%, i.e. spin, up to 50% slip and in addition also at
100% slip, i.e. locked wheel. Test wheel rim size is 13 ­15" and tire widths up to 185 mm can be used.
BV14 is a new instrument measuring thefrictionin two parallel traces and designed to be carried at the
rear end of anyfrontwheel driven vehicle. Each measuring wheel is mounted in the rear end of a beam,
the front end of which is supported by the hub of a rear wheel of the host vehicle. The beam is about
horizontal in the measuring position and contains a chain transmission connecting the rear wheel of the
vehicle with the measuring wheel. The gearing is chosen to give a constant slip of about 15%. The size
of the test wheel is the same as for Β VI1, i.e. 4.00­8«.
The Saab Friction Tester is basically a front wheel driven passenger car with the rear axle replaced by a
ΒVI1. Originally Saab 900 was used while later versions are based on Saab 9000. In the same way as
in the case of BV14 the slip is controlled by the rear wheels of the host vehicle.
Friction measurement is always carried out on wet surfaces which means that all friction measuring
devices mentioned above have their own water supply, carried by the tow vehicle or the host vehicle,
and a water nozzle giving a water depth of normally about 0,5 mm independent of speed.
162
Bearing capacity
Rolling Deflection Meter (RDM)
On behalf of the National Swedish Road Administration VTI is currently developing a new
measurement vehicle for high-speed measuring of road surface deflection under a rolling load.
The purpose of the new method is to make possible to undertake continuous measurements at about
normal traffic speed and also to make use of a loading method more akin to the load the road is
exposed to due to heavy vehicles.
The measurement method involves a heavy two axle truck, especially designed for this purpose, with a
cross profilometer mounted about midway between the front and rear axles and a second cross
profilometer placed immediately behind the rear axle. Each cross profilometer consists of 20 distance
measuring laser devices. The rear axle is loaded to the maximum load that the wide single tyres are
allowed to carry (presently 112 kN), while the front axle is as lightly loaded as legally permitted from a
manoeuvrability point of view (about 30 kN). The distance between the front and rear axles of the truck
is 6 m and the cross profilometer placed between the axles is supposed to measure the cross profile of
the road outside of the deflection basins caused by the front and rear axles respectively. The rear cross
profilometer, on the other hand, measures the cross profile of the same cross section of the road but this
time as deflected by the rear axle. The difference between the two profiles gives what has been called
the «difference profile« which is the deflection caused by the heavily loaded rear axle of the truck.
When measuring the vehicle is driven along the road at about the normal speed for heavy trucks. As the
measured road deflection depends, among other things, on the speed of the truck, a standardised
measuring speed must, however, be defined. Although the top speed of the truck is above 110 km/h the
standardised measurement speed will probably be 70 km/h as the truck is capable of maintaining this
speed over 98% of the Swedish road net.
The distance between the different laser units and the road surface is sampled at a rate of 16 kHz. A
mean distance value for each laser unit is calculated every 100 - 150 mm, thus filtering out the
macrotexture effect on the readings, and a mean profile based on these mean values is determined for
each cross profilometer.
Measurement results are presented in terms of "difference profiles", meaning the difference between
the profiles recorded by the two cross profilometers.
Before the calculation of the «difference profile« the two cross profiles, defined by 20 points, are
smoothed using a third order spline function. When measuring in curves the error caused by the «offtracking« of the rear cross profilometer relative the front one, can be corrected. This correction can be
based either on information of the side-slip angle and the yaw velocity of the vehicle or using the cross
correlation between the two profiles. The second method will, however, only work on rutted roads.
The measurement principle was tested using a prototype measurement vehicle built on an old standard
truck and a rather good correlation with the Falling Weight Deflectometer (FWD) was established for
measurement speeds up to 70 km/h, the maximum speed of the old truck.
163
Ground penetrating radar
For high-speed measurement of layer thicknesses of roads one or two vehicle mounted 2,5 GHz radar
antennas are used. With a sampling distance of 0,5 m and measuring with only one antenna the
measurement speed is about 70 km/h. Using two antennas the speed is reduced to about 35 km/h with
same sampling distance. The penetration depth is normally in the order of 0.6 - 0,7 m but may under
certain condition exceed that figure.
Surface distress
The new distress detection system called HYBRID, is based on a combination of video technique and
distance measuring lasers. A prototype has been developed jointly by the Swedish Road & Transport
Research Institute (VTI), RST (Road Survey Technology) Sweden AB and Infrastructure Management
System (IMS) in USA.
This measurement system, which in the future will be incorporated in the Laser RST system, consists of
four downwards facing video cameras, mounted at the rear of a van, and connected to four video
recorders. With a horizontal bandwidth of 400 pixels for each recorder there are in total 2000 pixels
covering a road width of 3,2 to 4,0 m. Each pixel thus covers 1,6 to 2,0 mm which equals the resolution
of the system. The system collects shadow free images using computer controlled strobe lightning.
Standard cameras with a shutter time of V10ooo s are used, allowing measurement speeds up to and
including 90 km/h.
The idea behind the use of a combination of video cameras and distance measuring lasers for this
measurement task is the ability of the lasers to measure down into a crack and thus make it possible to
decide whether e.g. a black line on the surface, visible on the video image, is a crack or just a black
line.
The final video images are subsequently converted in laboratory to a continuous film strip of road
surface information, i.e. not divided in separate frames. This is important for the subsequent automatic
image analysis as a crack otherwise could appear in two consecutive frames and thus be counted twice.
In a later stage of development this work station will be placed in the measurement vehicle. Together
with automatic image processing this will probably mean that the storing of video images can be
dispensed with.
Presentation of measurement results
The Laser RST measurement results are related to the Swedish road node system and can be presented
in a number of ways. The Laser RST presents on line several numbers characterising the road surface
such as unevenness, rut depth, macrotexture etc. Measurement data can subsequently in the laboratory
be presented on road maps produced on the basis of travelled distance, road curvature and direction of
the road. Different classes of e.g. unevenness or rut depth can be shown on these maps represented by
different colours, thus forming an excellent basis for decisions about priority and location of
maintenance measures to be taken.
The skiddometer data are currently presented on line on paper or on tape or disk. Using the Laser RST
as a tow vehicle for BV11 would open the opportunity to incorporate friction data with the current
Laser RST data. This possibility has, however, so far not been utilised.
The final data presentation system for RDM remains to be developed but it will be compatible with the
one used in Laser RST.
164
The combined information from Laser RST, RDM and HYBRID will give a better insight in the
structural properties of the road and an excellent basis for decisions about maintenance measures to be
taken. A combination of the three measurement devices in a common vehicle is also foreseen for the
future.
D Π
Relling
eflectian Meter
165
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166
SWITZERLAND: STATE OF PRACTICE REPORT
PAVEMENT MONITORING EQUIPMENT AND METHODS IN SWITZERLAND
MHORAT
Pavement Management Systems
In Switzerland standardised and computer based pavement management systems for roads are
currently being developed, installed and tested. These management systems also include pavement
maintenance planning and therefore also require traffic data information and information about the
surface condition as well as the structural condition of the pavements.
Standardised paper forms for visual inspections with weighting values allow the calculation of an
index. There are also three other quality indices (longitudinal evenness, transverse evenness and skid
resistance). The indices stemming from the visual inspection, the longitudinal evenness and the
transverse evenness can be combined (using weighting values) to calculate an overall index
concerning surface condition.
Generally speaking: The acceptance of new equipment and methods is rather low as long as they are
not standardised.
Longitudinal Evenness
Longitudinal evenness is usually measured using a trailer with three wheels in a row and a distance
of one meter between them. Rolling along an uneven road, the different heights of the three wheels
cause a constant changing angle, which is normally measured every 2.5 cm. According to the Swiss
standards the standard deviation of these angles - usually after 250 m - is used to assess the
longitudinal evenness. Additionally, there is also an ARAN in use to measure longitudinal
evenness. The standards specify limits for new pavements and for roads in use.
Rutting
Stationary systems like straight-edges and transverse profilographs are used in order to determine
rutting and water depth. Faster evaluations can be done using the ARAN.
The standards specify limits for new pavements and for roads in use.
Skid Resistance and Texture
Skid resistance and texture data are currently collected by using the pendulum in combination with
the outflow meter (skid resistance and texture), the Skiddometer (skid resistance), the sand patch
method (texture) and the ARAN (texture). There is also a Stuttgarter Reibungsmesser (SRM); a
device based on the same principles as the Skiddometer , but with a better efficiency and the option
of measuring both wheelpaths at the same time. In addition to the measurements with blocked and
fixed slip wheels, there is also the possibility of ABS-measurements. It is planned to replace the
Skiddometer in the near future with the SRM. The current standards specify limits for the pendulum,
the outflow meter and blocked wheel measurements.
167
Noise
Traffic noise is a subject of increasing importance. Tyre/road noise is related to the pavement
condition (mainly texture) and may become a more and more important part of pavement
maintenance planning. The tyre/road noise properties of different types of pavements are currently
the subject of a research project. In order to have near field measurements a trailer is used as the
main device.
Bearing Capacity
According to the standards plate tests and the Benkelman beam are the main (i. e. standardised)
devices for measuring bearing capacity. The Benkelman beam is also used to determine the layer
thicknesses of pavement reinforcements.
Another stationary device is the "Schwinger", which is a similar construction to the better known
Dynaflect. It allows the measurement of deflection curbs using five geophones. Then there is also a
FWD. A current research project is trying to relate the different methods with the aim to find a way
to standardise all of them.
Mainly for research purposes an opto-electronical system is used for dynamic deflection
measurements at a circular test track near Zurich.
Other Devices For Structural Data
Other equipment used to collect structural data without having to take cores are a radar system for
layer thicknesses and nuclear isotopie soil penetrometers. Both devices are stationary. Another
device that is currently being developed uses infra-red-sensors in order to measure the different
temperatures (of whole areas) and also their changes in the course of time, for example during the
construction and compaction of new pavements.
There is also a new mobile system using GPR (Ground Penetrating Radar). The system is currently
being optimised and its main features are the inspection of layer thicknesses, pavement damages,
investigation of sub-pavement structures and the location of rebars in concrete structures.
Visual Inspection and image capturing
The standards provide two forms for visual inspection. One can be used in a slow travelling car, the
other is more detailed and requires walking. The ARAN has Video equipment and visual
observations can be entered using a keyboard. A project to develop a holographic crack detection
system was halted in 1995.
Traffic Data
There is a network of automatic counting stations for traffic data. Weigh-in-motion is also
becoming more important.
168
UNITED KINGDOM: STATE OF PRACTICE REPORT
ROAD MONITORING DEVELOPMENTS
Ρ G JORDAN, TRANSPORT RESEARCH LABORATORY (TRL)
INTRODUCTION
The development of machine based road monitoring systems has progressed markedly in the UK to
meet the increasing demands of road managers. Equipment are now available to monitor most aspects
of surface and structural condition of road pavements. However further development work is needed to
improve the productivity of non destructive methods of assessing structural condition and the
interpretation of surface distress data collected by video techniques.
The following sections briefly describe road monitoring equipment that are in routine use or are at the
prototype stage in the United Kingdom.
SURFACE CONDITION
The traditional method of assessing surface condition using visual inspection is increasingly being
replaced by machine based methods most of which employ laser sensing and video systems.
In the case of skid resistance the well known SCRIM machine, Figure 1, which was developed at TRL
has been in routine use now for over 20 years. Its measurements are used to implement the central
government's skid resistance standards on the trunk road and motorway system. Recent research at
TRL has shown the importance of macrotexture as well as microtexture in reducing skid related
accidents. As a consequence equipment development in this area is now aimed at combining skid
resistance and macrotexture measurements in the one machine i.e. SCRIM.
The laser based multi-friction high-speed road monitor (HRM), developed at TRL, is in routine use
monitoring wheeltrack rutting, macrotexture and longitudinal profile; other trailerless versions of this
machine, called the high speed survey vehicle (HSV), Figure 2, and the multifunction road monitor
(MRM) are also used widely both within the United Kingdom and overseas. The MRM is
manufactured and marketed by the UK company WDM Ltd. All of these pieces of equipment employ
a geometrical principle for the measurement of surface profile, rutting and texture. Laser sensors
provide the basic raw data that are processed and interpreted by algorithms programmed into a
computer that controls the operation of the complete system. The equipment operate at speeds of up to
100 km/hour and the measurement principles are independent of operating speed. The rut measuring
process has been improved in recent years by using three rather than the single laser sensor previously
used. This improvement has made the calibration of the rut measuring system independent of the
mechanical parameters of the operating vehicle. Another similar but more recent development in this
area is the multifunction ORCA machine developed by Devon County Council in the UK which is now
also in routine use.
Work on surface distress assessment is focused on the development of an automated system for the
collection and interpretation of surface cracking and other general distress not measured by the laser
sensors on existing equipment. An improved method of collecting road surface images has been
developed to the prototype stage, at TRL. The system uses a configuration of lighting units (to provide
a uniform surface illumination) and cameras to record high quality images of the road surface at speeds
up to 50 km/hour. The prototype system is capable of operating in daylight hours and collects
169
contiguous images, approximately one metre square, along the nearside wheeltracks in the direction of
travel of the system vehicle.
Surface images collected by the system are processed through prototype image processing systems
developed by TRL and the University of Birmingham in the UK. Initial results from these processing
systems appear promising and work is now in progress to improve the efficiency, in particular the
processing speed of the system.
Figurei: SCRIM
Figure 2: High-speed Survey Vehicle (HSV)
STRUCTURAL CONDITION
Pavement deflection under a rolling, or impulse load is the dominant method of structural assessment
employed in the UK. The well known Deflectograph machine is widely used on trunk and some local
170
roads to provide pavement strength data. These data can be interpreted to give pavement residual life
information for the planning of structural maintenance and, where required, overlay designs to
strengthen structurally weak pavements. The deflection pavement life relationship used to interpret
deflection measurements have recently been reviewed and updated by TRL to cover a wider range of
bituminous pavement designs. A modified version of the Deflectograph, developed by the company
WDM Ltd in the UK, has also been applied to the measurement of load transfer on jointed concrete
roads. Deflectograph operational speeds are typically 2/3 km-hour and because of seasonal
temperature and water table levels its survey periods are usually restricted to the Spring and Autumn
seasons.
A number of Falling Weight Deflectometers (FWD) are also used in the UK mainly for non destructive
detailed structural investigation on deteriorated pavements. Because of its relatively good
measurement accuracy, FWD data can be interpreted using theoretical models of pavement response to
give estimates of pavement layer moduli. These estimates have been found to be sensitive to
measurement accuracy but still provide a useful guide to the source of structural weakness in a
deteriorated pavement. Work is continuing to improve the methods of interpreting FWD
measurements.
Ground RADAR is also used in the UK to provide information to supplement deflection based
structural assessments. Ground RADAR operates by transmitting a pulse of electromagnetic radiation
into the pavement. As the radiation is transmitted down through the pavement its velocity is changed
and its strength is attenuated and part of the radiation is reflected at layer boundaries. This reflected
radiation is collected and processed to provide information about the pavement structure; such as layer
thickness, the presence of voids and the moisture content of subbase and or subgrade.
Tests on ground RADAR at TRL have shown that both dipole and horn antenna RADAR can measure
pavement thickness to an accuracy of 10 per cent in the absence of metal in the pavement. Because
they operate closer to the pavement surface the dipole antenna RADAR project a greater amount of
energy into the pavement and are therefore capable of resolving greater thicknesses of pavement layers
than the horn antenna system. On the other hand the horn antenna can operate successfully at higher
speeds albeit to a lesser depth of pavement.
Research is continuing at TRL on this topic and recent work has suggested that subsurface pavement
cracking can be detected using dipole antenna RADAR operating at speeds in the range 2 to 10
km/hour.
171
172
8.3
The Questionnaire
European Co-operation
in the field of Scientific
and Technical Research
COST 325
Road Monitoring
Questionnaire on road condition monitoring
(surface distress and bearing capacity
European Commission
Directorate General of Transport
173
QUESTIONNAIRE ON ROAD CONDITION MONITORING
General
1. Would you please fill in the table below?
Surname, initials
Job title
Name of employer
Country
Region
City
Phone number
Fax number
2. Please fill in the road-lengths of your network.
Road length (km)
Road type
Flexible
Composite
Rigid
Total
Tolled motorways
Free motorways
Main roads
Minor roads
Urban roads
Part I: Surface Distress Data Collection
Pavement distress occurs as a result of traffic and weather conditions. The distress can be cracking, surface defects or other
irregularities. This surface distress, which is visible as a rule, indicates that the pavement is deteriorating.
/.
General
1.1
Do you collect surface distress data on roads at network level?
D
Yes. (Please go to question 1.4)
D
No.
174
1.2
Give one or more reasons for not collecting data on surface distress?
(If you have more reasons, please rank them with the most important reason being indicated by the number 1.)
D
D
D
D
1.3
1.4
Visual inspection is time consuming/expensive.
Visual inspection is subjective/not reliable.
Inappropriate for road maintenance purposes.
Other
Do you intend to collect surface distress data in the future if the problems mentioned under point 1.2 are solved?
D
Yes.
D
No.
D
Uncertain.
(Please continue with question 5; part I)
Give one or more purposes for which you collect data on surface distress?
(If there are more purposes, please rank them with the most important reason being indicated by the number 1.)
D
D
D
D
D
D
D
To predict the evolution of the network.
To determine a long term budget for road maintenance.
To determine a long term maintenance scheduling plan for roads.
To follow-up the efficiency of the maintenance policy.
To determine rehabilitation measures for sections of road.
For research.
Other:
2.
Methods of collecting surface distress data
2.1
How do you collect surface distress data?
D
Manual (visual inspection of the road surface condition.)
D
Image capturing; manual processing (recording of road surface on film or video; visual inspection of the road
surface condition.)
D
Image capturing; automated processing (fully automated system for the acquisition and processing of the
visual distress data).
2.2
Manual visual inspection.
If not applicable, go to question 2.3.
2.2.1 I low do you survey the condition of your roads?
D
Continuous (the total road-length is surveyed).
D
Discontinuous (parts of the total road-length are surveyed).
If discontinuous, which sampling method do you use?
D
Selective.
D
Regular.
D
Random.
2.2.2 How do you carry out visual inspections?
D
On foot.
D
In a car.
D
Other
2.2.3 I low do you register data:
D
Paper form.
D
Portable PC.
D
Other
175
2.2.4 Do you take safety measures during visual inspections?
D
Yes.
D
No.
D
Sometimes.
2.2.5 Do you use a manual for collecting surface distress data?
D
Yes.
If yes, please state the name of the manual:
D '
No.
2.3
Image Capturing
If not applicable, go to section 3.
2.3.1 Which technique do you use for recording surface distress?
D
film.
D
video.
D
photo.
D
infra-red light recordings.
2.3.2 Do you combine the recordings with other measurement techniques in order to detect surface distress?
D
Yes.
D
No.
D
D
D
If yes, which technique^) do you use?
laser.
ultra-sonic.
other
2.3.3 Please describe the equipment that you use.
* name of the equipment
* system configuration
* specification offilmor video
* resolution
* use of artificial light
* operating speed
2.3.4 What are the operating conditions for your system?
D
Daytime.
D
Dry conditions.
D
Nighttime.
D
Wet conditions.
2.3.5 How do you record images?
D
Continuous (the total road-length is surveyed).
D
Discontinuous (parts of the total road-length are surveyed).
Π
D
D
If discontinuous, which sampling method do you use?
Selective.
Regular.
Random.
176
2.3.6 How do you process your recordings?
D
Manual (go to section 2.4)
D
Automated (go to section 2.5)
D
Combined (go to section 2.4)
2.4
Manual processing
2.4.1 Please give a short description of the method that you use for rating the distress of the road surface, recorded on film or
video?
2.4.2 How do you process the recordings?
D
Continuous (all the recordings are processed).
□
Discontinuous (parts of the recorded road-length are processed).
D
D
D
If discontinuous, which sampling method do you use?
Selective.
Regular.
Random.
2.4.3 How do you record the surface distress, extractedfromfilmor video?
G
On paper.
O
Computer keyboard.
D
Other
2.5
Automated processing
(If not applicable, please go to question 3.)
2.5.1 Where do you process the data?
D
In the vehicle (real-time processing).
D
In the office (post processing).
2.5.2 What is the method of processing?
? Image processing and pattern recognition.
? Laser data interpretation.
? other
Please give the name of the system (processing method) and the status of development (prototype or routine production)?
2.5.3 How do you process the recordings?
D
Continuous.
D
Discontinuous.
If discontinuous, which sampling method do you use?
D
Selective.
D
Regular.
□
Random.
3.
Quality Assurance
3.1
Do you have a quality assurance procedures?
D N o.
D
Yes.
177
If Yes, to what do the procedures apply?
D
Data collection.
D
Data processing.
Please give a short description of the quality assurance procedure(s).
4.
Methods in use
4.1 Please use table below to define:
1. the units that are used for the registration of distress types.
2. the classes (scales) of severity for each distress type.
Distress types
Units
(e.g. m, m2, %)
Classes (scales) of severity
Longitudinal cracks
Transverse cracks
Alligator cracks
Ravelling
Pot holes
Bleeding
Other
178
4.2 Please use table below to state the quality of measurement per distress type.
METHOD
Distress type
visual
inspection
image capturing
manual
good
acceptable
poor
good
acceptable
automated
poor
good
acceptable
Longitudinal cracks
Transverse cracks
Alligator cracks
Ravelling
Pot holes
Bleeding
Other
4.3 Please describe the performance of the method(s) that you use at this moment.
METHOD
Performance
visual
inspection
image capturing
manual
Capacity
km per day
(8 hours)
Costs per km
(ECU)
Road-safety
Traffic
disturbance
good
moderate
poor
good
moderate
poor
179
automated
poor
5.
Needs in thefield of acquisition ofsurface distress data
Please describe, from the previous tables at 4.2 and 4.3, your needs (required improvements) regarding the acquisition of
surface distress data
Needs
Distress types
Longitudinal cracks
Transverse cracks
Alligator cracks
Ravelling
Pot holes
Bleeding
Other
Capacity
km per day
Costs per km
(ECU)
Traffic
disturbance
6.
Processing surface distress data
6.1
Do you use weighting values for surface distress data?
D
No.
D
Yes, please give a short description.
6.2
Do you calculate distress indices for sections of road?
D
No.
D
Yes, please give a short description.
6.3
Do you determine homogeneous (uniform) road sections?
Π
No.
Π
Yes.
180
If yes, which criteria do you use for determining homogeneous road sections?
D
Pavement distress.
D
Traffic volumes.
D
Pavement construction.
D
Other,
6.4
In which form do you want the distress data to be presented?
D
Tables.
D
Figures (graphs, histograms).
O
Geographical (in combination with GIS).
7
New developments
7.1
Are you aware of any new development in the field of automated distress-data collection?
D " No.
D
Yes, please give short description of the method and mention the name of the institute, university or factory
where the development takes place.
Part II: Bearing Capacity Measurement
The effects of continuous heavy axle loadings and climate on pavements lead to the degradation of road structures. To
efficiently manage rehabilitation or restrengthening maintenance operations, one has to understand the current and future
capacity of the network in terms of heavy truck traffic : the bearing capacity. Then one can use this information in models to
estimate the cost of each maintenance operation, the priorities between them, the long term program and/or the overall effects
of the maintenance strategy.
/.
Aim of bearing capacity data collection
1.1
Do you have methods to evaluate the bearing capacity of your roads at network level ?
D
No. Please go to question 5.
D
Yes.
D
On all types of roads.
D
Only on roads supporting heavy traffic (> .... AADT)
D
Other :
1.2
Give one or more purposes for which you collect data on bearing capacity?
(If there are more purposes, please rank them with the most important reason being indicated by the number 1.)
D
D
D
D
D
D
O
To determine rehabilitation measures for sections of road.
To determine a long term maintenance plan for your road network.
To predict the network evolution.
To determine a long term budget for road maintenance.
To follow up the efficiency of a maintenance policy.
For research.
Other:
2.
Methods for evaluating the bearing capacity of roads
2.1
How do you evaluate the bearing capacity of the roads ?
D
Continuously (the total road-length is evaluated).
181
D
Discontinuously (parts of the total road length are evaluated).
If discontinuous, which sampling method do you use?
Π
Selective.
D
Regular.
D
Random.
2.2
Do you determine the bearing capacity as:
D
the residual lifetime of the pavement.
D
the residual ES AL traffic capacity of the pavement.
D
the reinforcement thickness of the pavement.
D
the cost of the maintenance solution of the pavement.
D
Other:
2.3
Do these methods rely on deflection measurement?
D
Yes, go to question 2.5
D
No, please describe your method:
2.3.1 Give one or more reasons for not using deflection measurement.
(If you have more reasons, please rank them with the most important reason being indicated by the number 1.)
D
Not relevant at the network level.
D
Only relevant if combined with other conditions.
D
Too expensive at the network level.
D
Other:
2.3.2 If the problems mentioned under point 2.3.1 are solved, would you re-examine your point of view ?
D
Yes.
D
No.
D
Uncertain.
2.4
Does the method identified in question 2.2 involve the evaluation of other conditions?
D
Pavement temperature.
D
Surface distress.
D
Thickness of layers.
D
Moisture in the road structure.
D
Traffic.
D
Other:
2.5
Where do you measure deflection ?
D
In the wheel tracks.
D
Between the wheel tracks.
D
Both
D
Other ( please give a short description):
2.7
How do you measure deflection ?
D
Benkelman beam.
D
FWD.
D
Lacroix Deflectograph or similar.
D
Curviameter.
G
Other (please give a short description)
182
3.
Measurements with Benkelman or FWD
3.1
How do you select measurement locations on your network?
D
At regular intervals. Distance between measurements
D
At a few points on homogeneous sections.
Number of points:
Homogeneity criteria:
D
Other (please give a short description)
km.
3.2
Do you take traffic safety precautions during measurement?
D
No.
D
Yes, please give a short description.
4.
Measurements with Lacroix, Curviameter or similar devices
4.1
If you do not monitor the entire network, how do you select the locations to be measured?
D
At regular intervals. Distance between measurements
km.
D
A few measurements on homogeneous sections.
Number of measurements:
Homogeneity criteria:
D
Other (please give a short description)
4.2
What is the operational speed?
4.3
Do you take traffic safety precautions during measurement?
_No.
_ Yes (please give a short description)
km/hour.
Measurements with other types of deflection meters
If you do not monitor the entire network, how do you select the locations to be measured?
D
Regular intervals. Distance between measurements
km.
D
A few measurements on homogeneous sections.
Number of measurements:
Homogeneity criteria:
D
Other (please give a short description)
5.2
What is the operational speed?
km/hour
5.3
Do you take traffic safety precautions during measurement?
D
No.
D
Yes (please give a short description)
183
6.
Quality assurance
6.1
Do you have a quality assurance procedure?
D
No.
D
Yes (please give a short description)
6.2
What is the frequency of calibration ?
184
7.
Performance of methods in use
Please use the table below to describe the performance of the method(s) that you presently use?
METHOD
PERFORMANCE
Benkelman/FWD
Lacroix/Curviameter
Range of standard loads
available on the system
Repeatability
. good
. acceptable
. poor
Capacity
km/day
(8 hours)
Cost per km
(ECU)
Road-safety
. good
. acceptable
. poor
Traffic disturbance
. none
. acceptable
. poor
Frequency of measurements?
How many kilometres do
you monitor per day ?
185
Other methods
8.
Needs in the field of acquisition of bearing capacity data
Please use table below to describe your needs regarding the acquisition of bearing capacity data
PERFORMANCE
Needs
Accuracy (mm)
Repeatability
Capacity
km/day (8 hours)
Costs per km
(ECU)
Traffic
disturbance
9.
Treatment of data
9.1
Do you use deflection measurement data in combination with surface distress data?
D
No.
D
Yes (please give a short description)
186
9.2
Do you determine homogeneous (uniform) road sections?
D N o.
D
Yes.
If yes, which criteria do you use for determining homogeneous road sections?
Π
Level of deflection.
D
Pavement distress.
D
Traffic volumes.
D
Pavement construction.
D
Other
9.3
In which form do you present the data ?
D
Tables.
D
Figures (graphs, histograms).
D
Geographical (in combination with GIS).
IO.
New developments
10.1 Are you aware of any new developments in the field of deflection measurement collection ?
D N o.
□
Yes, please give a short description of the method and mention the name of the institute, university or
factory where the development takes place.
Part III: Pavement management systems
The objective of road maintenance management is to optimise maintenance funds allocation taking into account the various
functions of the roads. Most models, and then most pavement management systems (PMS), rely on pavement condition
monitoring to assess the state of the network. We want to know, through this third part, which road conditions are addressed
in road maintenance management systems and, conversely, what progress is necessary in road condition monitoring to
improve pavement maintenance management procedures.
Do you have you a Pavement Management System (PMS)?
D
Yes, go to question 2.
D N o.
1.1
Give one or more reasons for not having a PMS?
(If you have more reasons, please rank them with the most important reason being indicated by the number 1.)
D
□
D
D
D
Existing procedures are efficient.
Setting up such a system is too expensive.
Data acquisition for such a system each year is too expensive.
Benefits of a PMS are not convincing.
Other:
187
1.2
Do you intend to acquire such a system if the problems mentioned under point 1.1 are solved ?
D
Yes.
D
No.
D
Uncertain.
Give one or more purposes for which you use the PMS?
(If you have more reasons, please rank them with the most important reason being indicated by the number 1.)
D
D
D
D
D
D
D
3.
To predict the evolution of the network.
To determine a long term budget for road maintenance.
To determine a long term maintenance scheduling plan for roads.
To follow-up the efficiency of the maintenance policy.
To determine rehabilitation measures for sections of road.
For research.
Other:
Please use the tables below to indicate the road surface characteristics that are used in the PMS.
Pavement
condition
Uneven-ness
Crossfall
Rutting
Macrotexture
Skidding resis- Surface distress
tance
Deflection
Yes No
Yes No
Yes
Yes
Yes
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(1)
Yes
Tolled motorway
Free motorways
Main roads
Minor roads
Urban roads
No
No
No
Yes
No
No
(1) Including megatexture
(2) If you collect this information on this type of road, please state the percentage of the total road length that is monitored
each year.
188
8.4
Questionnaire Database
8.4.1
Table of recipients and respondents
189
Indcxlndcx
Title / Surname / First Name
Title
Function
Country
Name of Organisation
Division
Dip] ­Ing. Dr M. FUCHS
Bundes forsch ungs­ und Prüfzentrum
Arsenal
Gcoicchnischcs Institut ­ Objekt 214
Faradaygassc 3
A­I031 WIE N
1
Prof Dr J L1TZKA
Institut fur Straßenbau und
Straßcncrhaltung
TU­Wicn
Gußhausstraße 28/233
A­1040 WIE N
3
Mr D 0 BRE YE R
4
Director
Ministry of Economic Affairs
Federal Road Administration
Questionnaire
Rclurncd
Telephone
43/1.79,74,74,77
43/1,79,74,75.92
Yes
43/1,588,01 E xt. 40.16
43/1.504.42.09
Yes
Λ
EN
A
EN
ALBANIA
FR­EN
355/42.25 20
355/42.322 56
ALBANIA
EN
355/42260.43
355/42.277 73
1)
NL­FR
Vos
A­ WIE N
Institute of Road and Railway Design
Mr Vcip GURI
Language
ALBANIA­ TIRANA
5
6
Ministry of Transport
Roads and Investment Department
Mr­ Lluka LLUKANI
De Heer R CHARLIE R
Afdclingshoofd­
Dircctcur­Ing
Ministerie van de Vlaamse
Gemeenschap
Afdeling Wegenbouw kunde
ALBANIA­ TIRANA
Olympiadeillaan 10
B­1140 BRUSSE L
Premier Ingenieur en M. ET
Chef-Directeur des DG I - IG 11 - Direction des
Ponts et Chaussées
Structures Routières
Rue de l'Industrie 27
Β-1400 NIVELLES
Yd
s
Dr M GORSKI
Chercheur
Centrede Recherches routières
Boulevard de ta Woluwc. 42
B­1200 Bruxelles
Γ)
FR
32.2.771 20 80
322.77233.74
Yei
')
Mr Dimitar DIMOV
President of General
Road Administration
Ministry of Transpon
Bui "Macedonia" 3
BG­1606 SORA
BG
EN
359/252.1768
359/287 67.98
Ye»
II)
Mr Valentin MANTCE V
Director
Central Road and Bridges Laboratory
114 Bessarabia Str.
BG­1517 SOFIA
FIG
FN
359/2 45 II 18
359/24571.24
Yc·
II
Mr Milan MACHART
Deputy Director
C /eck Ministry of Transport
Odbor po/emnich Kormmikac!
NabnaãL Svorbodv 12
CZ­II015 PRAGUE 1
cz
EN
230/31233/214
231/40 15/232 56 69
12
Mr Josef MIKULIK
Director
Transport Research Center
Botanicka68a
CZ­66312 BRNO
cz
FR­EN
42/5.41 21 20.94
42/5 41 21 15 26
13
Mr Zdenck TRCKA
Pragoprojckl a s
K Rysance 16
CZ­Ì4754 PRAHA 4
cz
FN
42/2 46 34 50­9
42/2 42 01.49
14
Mr Claude MORZIE R
Departement des Ports et Chaussées
ΠΙ
IR
Yes
Yev
CH­ FRIBOURG
1'
Dr KNE PPE R
16
Mr Niels. Β SCHMIDT
1W,„
Bundesanstalt fur StraDcrmtscn (BASO
Postfach 10 01 50
D­5I40I BE RGISCH GLADBACH
D
FN
49/2204 43 711
49/2204 43 673
Dy natesi E ngineering A S
Kroghobngardsvq, 4A
DK­2950 VE DBÆK
DI:
FN
45 42 89 02 11
45 42 89 22 57
Ycv
Mr ErtmanH J L\RSEN
Danish Road Institute
Head of R&D Department
Elisagaardsvcj, 5- P O Bov 2
DK-tOOO ROSKILDE
45 46 30 01 00
Mr Nick GROENSKOV
Greenwood Engineering Acs
Lillcvang. 7
DK-2605 BROENDBY
45/43 % 96 83
Pboni.v Pavement Consultants
Fuglsangs Alle. 16
DK-6600 VEJEN
45/75 36 11 11
4575 36 42 06
Lyscng Alle. I
DK-8270 HOJBJERG
45/89 44.66.66
45/89 44 69 83
45 46 30 til 05
Mr Jom KRISTIANSEN
General Manager
Mr VagnLEERSKOV
Head of Road
Laboratory
Mr Josef JOSEFSEN
District Engineer
Ribe County
Sorsigvcj. 35
DK-6760 RIBE
45/75 42 42 IX)
4575 42 49 11
Mr Bend HEMMINGSEN
District Engineer
Road. 0&M Planning Division
i im. n Counlv
Orbackvcj, KM) - Amtsgaardcn
DK-5220 ODENSE
45/66.1594.00
45/66 15 91 60
Mr Enrique LOPEZ GAMIZ
Technical Director
AUMAR
Mr. Francisco CRIADO
BALLESTEROS
Subdirector General
dc Conservación y
Explotación
Ministerio de Obras Publicas y
Urbonimos
Dirección General de Carreteras
Pasco dc la Castellana. 67
E-28071 MADRID
34 1 597 81 22
Mr Luis FERREIRO MARTINEZ
Director General
AUMAR
c/Montalban, 5
E-28014 MADRID
34 1 522 34 90
Mr Francisco ACHUTEGUI VIADA
Jefe del Sector de
Evaluación a Escala
Real
Centro de Estudios de Carrclcras
(CEDEX)
Autovía de Colmenar, km 18 2
E-28790 EL GOLOSO-MADRID
Mr Jose Angel PRESMANES
RUBIO
Presidente dc
Audcnasa
Mr Aleksander KALDAS
Technical Director
Pia/a Conde dc Rodc/no, 8-7?
E-31003 PAMPLONA
Estonian Road Administration
24 Pamu Road
ESTONIA-OHM TALLINN
Quartier Sic Aime
F-84270 VEDENE
M CHARGROS
Chef du Departement
SETRA
Departement Conception, Realisation et
Entretien des Routes
46, avenue Aristide Briand - BP 100
F-92223 BAGNEUX CEDEX
M. CORBOEUF
Directeur Technique
S.A.P.R.R.
36, rue de Dr. Schmitt
F-21650 DIJON
M. DUMESNIL-ADELEE
Directeur Technique
Technologies Nouvelles
3, me Lipus Carl Pauling - Parc
Technologique de la Valine
F-76130 MONT-SAINT-A1GNAN
34 48 24 32 (Kl
M. FORMENTIN
Directeur de
Département
Service Technique Departement du
Nord
Departement de la Voirie et des
Infrastructures - Hôtel des services
51, avenue Gustave Dclory
F-59000 LILLE
34
M LE
Directeur
Service Technique Departemental du
Finistère
Kcrvir­Izella
8, rue de Kcrhucl
F­29196 QU1MPE R CE DE X
F
FR
35
M.Y.LEROLLE
C.E.B.T Ρ
Domaine de St. Paul
F­78470 SAINT REMY LE S
CHEVREUSES
F
FR
Yes
36
M LE YCURE
Directeur
SAMRA
23,avenue du Centre ­ Sainl­Qucntin­cn­
Yvelines
F­78286 GIYAMCPIRT CE DE X
F
FR
Yes
M. MARCADIER
Directeur de
Département
Service Technique Departemental des
2, rue Antoine Zattera - BP 307
Bouches du Rhône
F-13302 MARSEILLE CEDEX
Departement des Routes, des Transports
et des Equipements
38
M PRUD'HOMME
Directeur Technique
77, avenue R Poincaré
F­75116 PARIS
F
FR
39
M. RICARD
2. rue Gergovic
F­12000 RODE Z
F
FR
40
M GUY
me Saint­Esprit, 24
FR­63000 CLE RMONT­FE RRAND
FR
FR
ROCHÁIS
COFIROUTE
Service Technique Departemental de
ΓΑντιντση
Directeur Généra]
Service Technique Départemental du
Puv de Dôme
Mr. V. LAITANEN
Technical Research Centre of Finland
(VTT)
Road, Traffic and Geotcchnical
Laborator.
Lampomichenkuja, 2A
FIN-02150 ESPOO
42
Mr Nikolaos MICHAS
Ministry­ of UK Environment and Public
Works (KE DE )
Athens Regional Laborators
Kallirrois 144
GR­11741 ATHE NS
GR
FR­EN
30/1.922.27.27
30/1.924.18.63
43
Mr Gabor E CSE DY
KTI
Than Κ. o 3 ­ 5 ­ P O Box 107
H­1119 BUDAPE ST 1518
Η
EN
36/1.166 6901
36/1 166 70 00
44
Mr Laszlo GASPAR
K.T1
Road Management and Bridge Division
Than Κ. η 3 ­ 5 ­ P O Box 107
H­1119 XI BUDAPE ST 1518
Η
EN
36/1 185 03 11
36/1 16692 10
45
Prot Dr Brvin NE ME SDY
Technical University of Budapest
Department of Road fZngtneenng
MucEsctcm rkp 3K mf. 11
H ­ l l l l BUDAPE ST
Η
EN
36 1 166 56 26
361 166 5626
37
Prof Dr Mate SRSEN
Head of Pavement
Institut Grades inarvts a Hrvatskc
Management Division Civil E ngineering Institute of Croatia ­
Transportation Dept
J Rakme 1 ­ P O Box 213
HR­41000 ZAGRE B ­ CROATIA
HR
EN
385/41 61 32.43
385/41.53 47.37
47
Mr Ruggero ΒΕΝΕΤΗ
SINECO S ρ A
Via Felice Coati IA
1­20124 MILANO
I
IT
3 9 2 2 9 4 04513
39 2 294 00 974
48
Mr Alfredo RI VAR A
Soc Autostrada da F ion
Via della Repubblica. 46
1­18100 IMPE RIA
I
IT
39 183 70 71
39 183 256 55
General Director
Directeur General
Yes
Yes
Yes
Mr Francesco BRUNI
Directeur Général
Società Autostrade Romane ed
Abruzzesi
Via G. V Bona, 105
I­OOI56 ROMA
3 9 6 4 1 59 22 25
Mr Marcello CHR1STILLIN
Directeur Général
Società Autostrade Valdostane
Strada Banu, 13
1­11024 CHATILLON (AOSTA)
39 6 41 59 22 25
Mr Giuseppe D'ANGILINO
Amministratore
Straordinario
A.N.A.S.
Via Monzambano, 10
I­OOI85 ROMA
Mr Francesco PROTANO
Directeur Général
Società Autostrada Ligure ­ Toscana
Via Don E . Tazzoli, 9
1­55043 L1D01 DI CAMAIORE
39 584 90 93 00
Società Autostrade
Via Bergamini, 50
1­00159 ROMA
39 6 43 63 40 89
Mr J KASTANOVSKIS
Engineer
Latvian Road Administration
Mr 0 KRONLAKS
General Director
Larvian Road Administration
Gogola Street 3
LV­I9I0 RIGA
Mr. Virgaudas PUODZIUKAS
Technical Director
Lithuanian Road Design Institute
25, Kanto Street
LiTHUANlA-3000 KAUNAS
Vilnius Technical University
Saulcickio al 11
LITHUANIA­2054 VILNIUS
Minister of Transport
Government of the Republic of
Moldova
12a Bureuriey Str.
M0LDOVA­277004 KISHINE V
Mr Donstas CYGAS
Mr Dag ESE
Norwegian Public Roads
Administration
371/2.22.58.27
N­58040 HE RMANSVE RK
Dr Helge MÖRK
Norwegian Institute of Technology
Dr. Joslcin MYRE
Norwegian Road Research laboratory
Mr. Tore SLYNGSTAD
SINTEF
Norwegian Institute of Technology
N­7034 TRONDHE IM
63
Ing B BOEVINK
Rijkswaterstaat
Dicnstlcring Huis ter Heide
Postbus 18
NL-3712 ZG HUIS TER HEIDE
NL
NL
64
Mr. Α. Η. Ε. Μ. GERBRANDS
Rijkswaterstaat
Dicnstkring H aarlem
Amsterdamse Vaart 268
NL-2032 EK HAARLEM
NL
NL
65
Ing. F. J. JORNA
Rijkswaterstaat
Dicnstkring Lclvstad-Randnicren
Postbus 600
NL-8200 AP LELYSTAD
NL
NL
66
Mr. A. G. KNEEPKENS
Provincie Limburg
afd. Verkeer en Vencer, Bureau
projecten
Postbus 5700
NL-6202 MA MAASTRICH T
NL
NL
N­7034 TRONDHE IM
P. O. Box 6390 - Etterstad
N-0604 OSLO 6
371/2.22.78 18
Ing. J. A. KRAM
Rijkswaterstaat
Dicnstkring DAS NoordGcldcrlund/ Apeldoorn
Postbus 1031
NL-7301 BG APELDOORN
68
Ing F M KROESE
Provincie Noord-Holland
Dienst Wegen. Verkeer en Vervoer
Postbus 205
NL-2050 AE OVERVEEN
NL
NL
69
Ing J. MARING
Rijkswaterstaat
Dicnstkring Wegen Hengelo
Postbus 71
NL-7550 AB HENGELO
NL
NL
71)
Mr. D. J. NONNEMANTEL
Ingenieursbureau Amsterdam
Hoofd. Prode. Advies & Omwikkeling
Wibauthuis, kamer 7008, Wibautstraal 3
NL-1091 GH AMSTERDAM
NL
NL
71
Ing J. G PIJNAPPEL
Rijkswaterstaat
Dicnstkring Gorinchcm
Postbus 152
NL-420O AD GORINCHEM
NL
NL
72
Ing 1 G RINKEL
Gemeentewerken Oss
Postbus 5
NL-5340 BA OSS
NL
NL
73
Ing G SCHENK
Rijkswaterstaat
Dicnstkring Groningen
Postbus 52
NL-9750 AB Haren
NL
NL
74
Ing G J C F. SMULDERS
Rijkswaterstaat
Dicnsiknnu DAS Den Bosch
Postbus 5007
NL-5201 GA's-Hcrtogcnbosch
NL
NL
75
Ing K, TILMA
Rijkswaterstaat
Dicnstxring Friesland-Zuid
Postbus 211
NL-8500 AE JOURE
NL
NL
76
Ing S B van HARTSKAMP
Provincie Noord-Brabant
Dienst Waterstaat, milieu en serveer
Postbus 90151
NL-5216 TV s-HERTOGENBOSCH
NL
NL
Yes
77
Dhr R van WUK
Provincie Zuid-Holland
Bureau Wcgbouwkundc
Postbus 90602
NL-2509 LP 's-GRAVENHAGE
NL
NL
Yo
7»
Ing A M J van der ZEIJST
Rijkssvatcrstaat
Dicnstknng N+M Zeeland
Postbus 149
NL-4460 AC GOES
NL
NL
79
Ing, R. C J van der BAN
Provincie Zeeland
CJndcrafocling Wegen, sectie
ftidcrhoiid
Postbus 165
NL-4330 AD MIDDELBURG
NL
NL
Yes
SI)
Ing B 0 A WUGERTZE
Rijkswaterstaat
Dicnstknng ASW St Joost
Postbus 7064
NL-6050 AB MAASBRACHT
NL
NI.
Yes
SI
Mr Ν VERRA
NL
NL
Yes
I'
EN-FR
Yes
Senior Advisor
DWW / RWS
Yes
Yes
NL- DELFT
82
Mr BARROS
Senior Technical
Engmccr
JAE
P- LISBOA
8?
Dr Leszek RAFALSKl
Dnectc,
Roads and Bridges Research Institute
Stalingradzka 40
PL-03301 VARSOVIE
FL
EN
48/22 1103 83
S4
M Danila BUCSA
Director General des
Routes
Ministen: des Transports
Dnncu Oolescu Bvld. 38
RO-77113 BUCAREST 1
KO
Li.
40 131 20 984
48/22 111792
Mr Johan DRUTA
Head Office for
Relation of
International Co­
operation
Road Administration
Bd Dinicu Goicscu. 38
RO­77II3 BUCARE ST 1
M Laurencu STE LE A
Directeur General
Adjoin!
Administration Nationale des Routes
Bid Dinicu Golcscu. 38
RO­77113 BUCARE ST 1
Mr Joan TIGANAS
Mr Andrei RADU
40 163 85 801
40 1 31 20 984
40 1 312 09 84
Calca G m ilei. 393
RO­ BUCARE ST­Scctor I
Deputy Technical
Director
Mr Johan LANG
NRA
Road E ngineering Studies and
Infrastructure
RO­ BUCHARE ST
National Swedish Road Administration
S­78187 BORLÄNGE
Dr Anders LE NNGRE N
National Swedish Road Administration
_
Ρ O Box 1200
S­46284 VÄNE RSBORG
M Rolf MAGNUSSON
Rovai lnslitulcofTcchhnologv
Hit,h»a> E ngineering
S­10144 STOCKHOLM
Mr Bertil MÅRTE NSSON
Västerleden 41
S­27I5I YSTAD
Mr Leif SJOGRE N
Mr Lars­Göran WAGBE RG
Mr LcifG WIMAN
Swedish Road and Transportalion
Research Institute
S­581 95 LINKÖPING
S E N
Swedish Road and Transportalion
Research Institute
S­58195 LINKÖPING
Swedish Road and Transportalion
Research Institute
S­581 95 LINKÖPING
S E N
Mr Peler ONDROUSE K
Senior Adviser for
Maintenance
Communications and Public Works
Milclicova 19
SK­82006 BRATISLAVA
Mr Damijana D1MIC
Acling Dircclor
National Building and Civil
Engineering Institute
ZAG ­ Ljubljana
Dimi_cva 12
SLO­6I109 LJUBLJANA
Prof Dr. Tormax KASTE L1C
Mr, Anton SAJNA
DRC ­ Dra/bc Za Rasiskavc v Ccsmi in
Promctni Stroki
(Road and Transportation Research
Association)
Director of National
Road Dircclorate
DRSC
38/61,26.88 67
SLO­6I109 LJUBLJANA
Dunajska,48
SLO­61000 LJUBLJANA
38/61.31.99.95
Dipl.-lng. Mntija VILHAR
Forschungsgescllschaft für das
Verkehrs* und Straßenwesen
Titova 64
SLO-61109 LJUBLJANA
IDI
Mr Vinko VODOPrVEC
D.R.SC
National Road Directorate
Dunajska, 48
SLO-61000 U U B U A N A
102
Dr. Jancz _MAVC
Head of Department
National Road Company - DDC
Department for Technology and
Development
103
Mr. Oleg SKVORTZOV
104
Mr. Vladislav M. YUMASHEV
EN
38/61.242.22
SLO
EN
38661
386.61.
Dunajska, 48
SLO-61000 U U B U A N A
SLO
EN
38661
38661
First Duputy General Ministry of Transport
Director
Federal Highway Department
Bochkova street, 4
SU-129301 MOSCOU
SU
EN
95 28 72 920
95 28 61550/6666
Deputy Director of
Science
Chaussee of Enthusiasts, 79
SU-143900 BALASHIKHA 6
SU
EN
95 52101 11 OR 18 28
95 521 18 92
EN
95 7 095 229
95 7095 1510331
UK (GB)
EN
44/I344 770668
44/I344.77.03.56
UK (GB)
EN
SOYUZDORNII
State Highway Resemeli Institute
Mr V SILYANOV
Ministry of Science & Technical Policy
ofRussian
Federation Scientific Council for Road
Trafile Safety
Tverskaa Street, 11
SU-103905 MOSCOW
106
Mr Brian FERNE
Transport Research Laboratory
UK (GB)-Crowlhornc Berkshire
107
Mr C. K KENNEDY
W. D. M.
Survcv ¿è Consultancies Service
UK (GB)- BRISTOL
Mr YurryT NESTERENKO
Director
Investment &
Construction Coordination
Adnûnsitraticn of Ukrainian Stale
Concern of Road
Construction-Rcparl & Maintenance
(Uladontnjy)
Fiskultura Street, 9
UKR-252005 KIEV
EN
Yes
Yes
227 40 33/227 51 07
227 31 25
8.4.2
Statistical results
Part I: Surface Distress Data Collection
TY_ORG
NB_PAYS
44
TYPE
Code
Text question
Index of the answer
Name of he answer
Good type
-
42
-
0.95 0.05
-
-
0
1.
CHOICE
-
General
1.1
Do you collect surface distress data on roads at
network level ?
1.2
Give one or more reasons for not collecting
data on surface distress.
2
10
RANK
visual inspection is time consuming/expensive
2
0.5 0.5
RANK
visual inspection is subjective/not reliable
1
10
RANK
inappropriate for road maintenance purposes
TEXT
other
1
1
-
-
10
0
-
-
CHOICE
1.3
Do you intend to collect surface distress data
in the future if the problems mentioned under
point 1.2 are solved?
1.4
Give one or more purposes for which you
collect data on surface distress.
26
2.0 1.2
RANK
to predict the evolution of the network
23
1.5 0.9
RANK
to determine a long term budget for road
maintenance
27
1.6 0.7
RANK
to determine a long term maintenance
scheduling plan for roads
15
2.6 1.9
RANK
to follow-up the efficiency of the maintenance
policy
32
1.8 1.2
RANK
to determine rehabilitation measures for
sections of roads
19
2.2 1.9
RANK
for research
TEXT
other
4
-
-
-
-
2.
Methods of collecting surface distress data.
-
-
-
-
2.1
How do you collect surface distress data ?
197
42
0.05
0
CHOICE
Manual
42
0.38 0.62
0
CHOICE
Image capturing ; manual processing
42
0.10 0.90
0
CHOICE
Image capturing ; automated processing
-
-
-
-
2.2
Manual visual inspection
-
-
-
-.
2.2.1
How do you survey the condition of your roads
38
0.58 0.42
0
CHOICE
continuous
39
0.46 0.54
0
CHOICE
discontinuous
-
-
-
-
2.2.1.1
If discontinuous, which sampling method do
you use ?
17
0.82 0.18
0
CHOICE
selective
17
0.24 0.76
0
CHOICE
regular
CHOCIE
random
-
-
-
-
-
-
-
-
2.2.2
How do you carry out your visual inspections '?
40
0.53 0.48
0
CHOICE
on foot
40
0.78 0.23
0
CHOICE
in a car
TEXT
other
2
-
-
-
-
2.2.3
How do you register data ?
40
0.63 0.38
0
CHOICE
paper form
40
0.65 0.35
0
CHOICE
portable PC
TEXT
other
0
39
0.77 0.18
0.05
CHOICE
2.2.4
Do you take safety measures during visual
inspections ?
39
0.87 0.13
0
CHOICE
2.2.5
Do you use a manual for collecting surface
distress data ?
19
-
TEXT
34
0.50 0.00
the name if YES
0.50
CHOICE
4.
Methods in use
4.2
Distress types/Quality of measurement
Longitudinal cracks
198
33
0.52 0.06
0.42
CHOICE
Transverse cracks
34
0.44 0.00
0.56
CHOICE
Alligator cracks
33
0.42 0.09
0.48
CHOICE
Ravelling
34
0.56 0.00
0.44
CHOICE
Pot holes
33
0.42 0.03
0.55
CHOICE
Bleeding
17
0.47 0.00
0,53
CHOICE
other
0
CHOICE
other
0
CHOICE
other
31
36.37 33.74
VALUE
20
51.83 45.16
VALUE
-
-
-
4.3
capacity (km/day)
costs (ECU/km)
-
road-safety
35
0.43 0.57
0.00
CHOICE
good
35
0.43 0.57
0.00
CHOICE
moderate
34
0.15 0.85
0.00
CHOICE
bad
-
-
-
-
traffic disturbance
35
0.23 0.77
0.00
CHOICE
none
35
0.66 0.34
0.00
CHOICE
little
34
0.12 0.88
0.00
CHOICE
much
-
-
-
-
2.3.
-
-
-
-
2.3.1
Image capturing
which technique do you use for recording
surface distress?
18
0.28 0.72
0.00
CHOICE
film
18
0.78 0.22
0.00
CHOICE
video
18
0.11 0.89
0.00
CHOICE
photo
17
0.06 0.94
0.00
CHOICE
infra-red light recordings
199
0.60 0.40
15
-
-
-
0.00
CHOICE
2.3.2
-
Do you combine the recordings with other
measurement techniques in order to detect
surface distress ?
if YES, which techniques do you use ?
9
0.78 0.22
0.00
CHOICE
laser
9
0.33 0.67
0.00
CHOICE
ultra-sonic
TEXT
other
1
-
-
-
-
2.3.3
Please describe the equipment that you use
16
TEXT
name of the equipment
7
TEXT
system configuration
7
TEXT
specification of film or video
2
TEXT
resolution
7
TEXT
use of artificial light
VALUE
operating speed
11
-
63.09 17.92
-
-
-
2.3.4
What are the operating conditions for your
system?
16
0.94 0.06
0
CHOICE
day time
16
0.19 0.81
0
CHOICE
night time
13
1.00 0.00
0
CHOICE
dry conditions
13
0.08 0.92
0
CHOICE
wet conditions
-
-
-
-
2.3.5
How do you record images?
16
0.81 0.19
0
CHOICE
continuous
16
0.31 0.69
0
CHOICE
discontinuous
-
-
-
-
2.3.5.1
If discontinuous, which sampling method do
you use ?
4
0.75 0.25
0
CHOICE
selective
4
0.25 0.75
0
CHOICE
regular
4
0.00 1.00
0
CHOICE
random
200
-
-
-
-
2.3.6
How do you process your recordings ?
17
0.65 0.35
0
CHOICE
manual
17
0.24 0.76
0
CHOICE
automated
17
0.18 0.82
0
CHOICE
combined
-
-
-
-
2
-
2.4
TEXT
-
-
2.4.1
-
2.4.2
Manual processing
Please give a short description of the method
that you use for rating the distress of the road
surface, recorded on film or video ?
How do you process the recordings ?
14
0.57 0.43
0
CHOICE
continuous
14
0.43 0.57
0
CHOICE
discontinuous
-
-
-
-
2.4.2.1
If discontinuous, which sampling method do
you use ?
6
0.83 0.17
0
CHOICE
selective
6
0.17 0.83
0
CHOICE
regular
6
0.00 1.00
0
CHOICE
random
-
-
-
-
2.4.3
How do you record the surface distress,
extracted on film or video ?
13
0.23 0.77
0
CHOICE
on paper
13
0.77 0.23
0
CHOICE
keyboard
TEXT
other
3
-
-
-
-
4.
Methods in use
4.2
Distress types/Quality of measurement
4.2
Longitudinal cracks
11
0.36 0.18
0.45
CHOICE
10
0.40 0.10
0.50
CHOICE
Transverse cracks
11
0.27 0.27
0.45
CHOICE
Alligator cracks
11
0.18 0.36
0.45
CHOICE
Ravelling
11
0.27 0.09
0.64
CHOICE
Pot holes
201
10
0.30 0.10
0.60
CHOICE
Bleeding
7
0.43 0.00
0.57
CHOICE
other
0
CHOICE
other
0
CHOICE
other
9
173.33 138.62
VALUE
7
99.57 67.29
VALUE
-
-
-
4.3
capacity (km/day)
costs (ECU/km)
-
road-safety
10
1.00 0.00
0.00
CHOICE
good
10
0.00 1.00
0.00
CHOICE
moderate
10
0.00 1.00
0.00
CHOICE
bad
-
-
-
-
trafile disturbance
10
0.90 0.10
0.00
CHOICE
none
10
0.10 0.90
0.00
CHOICE
little
10
0.00 1.00
0.00
CHOICE
much
-
-
-
-
2.5
Automated processing
-
-
-
-
2.5.1
Where do you process the data ?
7
0.43 0.57
0.00
CHOICE
in the vehicle ?
7
0.71 0.29
0.00
CHOICE
in the office ?
-
-
-
-
2.5.2
What is the method of processing ?
7
0.43 0.57
0.00
CHOICE
image processing and pattern recognition
7
0.57 0.43
0.00
CHOICE
laser data interpretation
0
TEXT
other
3
TEXT
please give a short description
-
5
0.80 0.20
0.00
2.5.3
CHOICE
How do you process the recordings ?
continuous
202
0.20 0.80
5
-
-
-
0.00
CHOICE
discontinuous
-
2.5.3.1
if discontinuous, which sampling method ?
1
1.00 0.00
0.00
CHOICE
selective
1
0.00 1.00
0.00
CHOICE
regular
1
0.00 1.00
0.00
CHOICE
random
-
-
-
-
4.
Methods in use
4.2
Distress types/Quality of measurement
3
0.67 0.33
0.00
CHOICE
Longitudinal cracks
3
0.67 0.33
0.00
CHOICE
Transverse cracks
3
0.67 0.00
0.33
CHOICE
Alligator cracks
1
1.00 0.00
0.00
CHOICE
Ravelling
2
0.50 0.00
0.50
CHOICE
Pot holes
2
0.50 0.50
0.00
CHOICE
Bleeding
2
0.50 0.50
0.00
CHOICE
other
0
CHOICE
other
0
CHOICE
other
I
400.00 0.00
VALUE
0
-
4.3
VALUE
-
-
capacity (km/day)
costs (ECU/km)
-
road-safety
2
0.50 0.50
0.00
CHOICE
good
2
0.50 0.50
0.00
CHOICE
moderate
2
0.00 1.00
0.00
CHOICE
bad
-
-
-
-
traffic disturbance
2
0.50 0.50
0.00
CHOICE
none
2
0.50 0.50
0.00
CHOICE
little
203
2
-
0.00 1.00
37
-
0.46 0.54
-
-
0.00
CHOICE
much
0.00
CHOICE
3.
Quality assurance
3.1
Do you have a quality assurance procedure?
-
If YES, to what do the procedure apply?
17
0.88 0.12
0.00
CHOICE
data collection
17
0.76 0.24
0.00
CHOICE
data processing
TEXT
please give a short description
9
-
-
-
-
5.
Needs in the field of acquisition of surface
distress data, describe your needs.
11
TEXT
Longitudinal cracks
3
TEXT
transverse cracks
3
TEXT
alligator cracks
2
TEXT
ravelling
2
TEXT
pot holes
2
TEXT
bleeding
1
TEXT
other
1
TEXT
other
4
132.50 71.89
VALUE
capacity (km per day)
4
43.05 36.52
VALUE
costs (ECU per km)
TEXT
traffic disturbance
3
-
-
-
-
6.
Processing surface distress data
40
0.50 0.50
0
CHOICE
6.1
Do you use weighing values for surface
distress data ?
39
0.64 0.36
0
CHOICE
6.2
Do you calculate distress indices for sections
of road ?
3
41
TEXT
0.83 0.17
0
Yes, please give a short description
CHOICE
6.3.1
204
Do you determine homogeneous road sections'
in terms of pavement distress ?
-
-
-
-
if YES, which criteria do you use for
determining homogeneous road sections ?
34
0.71 0.29
0
CHOICE
pavement distress
33
0.76 0.24
0
CHOICE
traffic volumes
34
0.88 0.12
0
CHOICE
pavement construction
TEXT
other
12
-
-
-
-
-
-
-
-
CHOCE
tables
-
-
-
-
CHOCE
figures
-
-
-
-
CHOCE
geographical
-
-
-
-
39
0.44 0.56
0
17
6.4
In which form do you want the data to be
presented?
7.
CHOICE
New developments
7.1
Are you aware of any new development in the
field of automated distress-data collection ?
TEXT
please give a short description
Part II: Bearing Capacity Measurement
TY_ORG
NB_PAYS
44
TYPE
Code
Text question
Index of answer
Name of the answer
Good type
-
-
-
-
1.
Aim of bearing capacity data collection
44
0.82 0.18
0.00
CHOICE
35
0.80 0.20
0.00
CHOICE
If yes, on all type of roads ?
35
0.09 0.91
0.00
CHOICE
If yes, only on roads supporting heavy traffic?
TEXT
If yes, other ?
6
-
31
1.6 1.0
1.1
-
1.2
RANK
Do you have methods to evaluate the bearing
capacity of your roads at network level ?
Give one or more purposes for which you
collect data on bearing capacity ?
To determine rehabilitation measures for
sections of road
205
21
1.8 1.0
RANK
22
2-.1 1.1
RANK
18
2.4 1.4
RANK
To determine a long term budget for road
maintenance
17
2.9 1.9
RANK
To follow up the efficiency of a maintenance
policy
23
2.6 2.0
RANK
For research
TEXT
Other
3
To determine a long term maintenance plan
for your road network
To predict the network evolution
-
-
-
-
2.
Methods for evaluating the bearing capacity of
roads
-
-
-
-
2.1
How do you evaluate the bearing capacity of
the roads ?
38
0.39 0.61
0.00
CHOICE
Continuously ?
38
0.63 0.37
0.00
CHOICE
Discontinuously ?
-
-
-
-
24
0.79 0.21
0.00
CHOICE
selective ?
24
0.17 0.83
0.00
CHOICE
regular ?
24
0.04 0.96
0.00
CHOICE
random ?
-
-
-
-
2.2
Do you determine the bearing capacity as :
37
0.68 0.32
0.00
CHOICE
the residual lifetime of the pavement
37
0.57 0.43
0.00
CHOICE
the residual ESAL traffic capacity of the
pavement ?
37
0.73 0.27
0.00
CHOICE
37
0.19 0.81
0.00
CHOICE
6
the reinforcement thickness of the pavement
the cost of the maintenance solution of the
pavement
TEXT
38
0.97 0.03
0.00
2
-
If discontinuously, which sampling method do
you use ?
other
CHOICE
2.3
TEXT
-
-
Do these methods rely on deflection
measurement ?
If no, please describe your method ?
-
2.3.1
206
Give one or more reason for not using
deflection measurement.
1
0.00 1.00
0.00
CHOICE
1
0.00 1.00
0.00
CHOICE
only relevant if combined with other
conditions
1
1.00 0.00
0.00
CHOICE
too expensive at the network level
TEXT
other
1
1.00 0.00
-
-
-
0.00
CHOICE
-
2.3.2
If the problems mentioned under point 2.3.1.
are solved, would your re-examine your point of
view?
2.4
Does the method identified in question 2.2
involve the evaluation of other conditions ?
5
0.80 0.20
0.00
CHOICE
pavement temperature
5
0.60 0.40
0.00
CHOICE
surface distress
5
1.00 0.00
0.00
CHOICE
thickness of layers
5
0.20 0.80
0.00
CHOICE
moisture in the road structure
5
1.00 0.00
0.00
CHOICE
traffic
TEXT
other
1
-
-
-
-
2.5
Where do you measure deflection ?
37
0.89 0.11
0.00
CHOICE
in the wheel tracks
37
0.16 0.84
0.00
CHOICE
between the wheel tracks
37
0.16 0.84
0.00
CHOICE
both
TEXT
other
4
-
-
-
-
2.7
How do you measure deflection ?
38
0.18 0.82
0.00
CHOICE
Benkelman beam
38
0.71 0.29
0.00
CHOICE
FWD
38
0.45 0.55
0.00
CHOICE
Lacroix deflectograph or similar
38
O.Il 0.89
0.00
CHOICE
Curviameter
TEXT
other
0
-
not relevant at the network level
-
-
-
3.
207
Measurements with Benkelman or FWD
-
-
-
-
3.1
How do you select measurements locations on
your network ?
30
0.63 0.37
0.00
CHOICE
at regular intervals
31
0.26 0.74
0.00
CHOICE
at a few points on homogeneous sections
TEXT
other
25
31
0.97 0.03
0.00
CHOICE
3.2
TEXT
25
Do you take traffic safety precautions during
measurement ?
please give a short description
20
43.30 28.17
VALUE
3.7
range of standard loads available (min)
20
94.10 53.83
VALUE
range of standard loads available (max)
29
0.86 0.14
0.00
CHOICE
repeatability good ?
29
0.14 0.86
0.00
CHOICE
repeatability acceptable ?
29
0.00 1.00
0.00
CHOICE
repeatability poor ?
26
13.40 5.94
VALUE
capacity km/day
20
168.25 212.63
VALUE
cost per km (ECU)
29
0.17 0.83
0.00
CHOICE
road safety good ?
29
0.72 0.28
0.00
CHOICE
road safety acceptable ?
29
0.10 0.90
0.00
CHOICE
road safety poor ?
28
0.00 1.00
0.00
CHOICE
traffic disturbance none ?
23
0.79 0.21
0.00
CHOICE
traffic disturbance acceptable ?
28
0.25 0.75
0.00
CHOICE
traffic disturbance poor ?
9
3.22 0.79
VALUE
frequency of measurements
-
-
-
-
4.
Measurements with Lacroix, Curviameter or
similar devices.
-
-
-
-
4.1
If you do not monitor the entire network, how
do you select the locations to be measured ?
12
0.17 0.83
0.00
CHOICE
at regular intervals
208
12
0.42 0.58
0.00
8
18
5.28 4.82
19
0.84 0.16
0.00
CHOICE
a few measurements on homogeneous sections
TEXT
other
VALUE
4.2
CHOICE
4.3
TEXT
15
What is the operational speed? [km/h]
Do you take traffic safety precautions during
measurements ?
please give a short description
13
73.64 42.62
VALUE
13
89.33 48.45
VALUE
range of standard loads available (max)
16
0.69 0.31
0.00
CHOICE
repeatability good ?
16
0.31 0.69
0.00
CHOICE
repeatability acceptable ?
16
0.00 1.00
0.00
CHOICE
repeatability poor ?
16
29.41 21.33
VALUE
capacity km/day
15
140.87 88.18
VALUE
cost per km (ECU)
18
0.56 0.44
0.00
CHOICE
road safety good ?
18
0.33 0.67
0.00
CHOICE
road safety acceptable ?
18
0.06 0.94
0.00
CHOICE
road safety poor ?
18
0.06 0.94
0.00
CHOICE
traffic disturbance none ?
18
0.78 0.22
0.00
CHOICE
traffic disturbance acceptable ?
18
0.17 0.83
0.00
CHOICE
traffic disturbance poor ?
4
4.00 0.00
VALUE
frequency of measurements
4.7
range of standard loads available (min)
-
-
-
-
5.
Measurements with other types of deflection
meters.
-
-
-
-
5.1
If you do not monitor the entire network, how
do you select the locations to be measured?
0
CHOICE
at regular intervals
0
CHOICE
a few measurements on homogeneous sections
209
0
TEXT
0
VALUE
5.2
0
CHOICE
5.3
-
33
0.58 0.42
other
0.00
21
What is the operational speed ?
Do you take traffic safety precautions during
measurement?
6.
Quality assurance
CHOICE
6.1
do you have a quality assurance procedure ?
TEXT
6.2
what is the frequency of calibration ?
8
15
0.01 0.01
8
Needs in the field of acquisition of bearing
capacity data.
VALUE
Accuracy (mm)
TEXT
Repeatability
9
125.00 125.76
VALUE
Capacity (km/day = 8h)
7
61.71 44.77
VALUE
Costs per km (ECU)
TEXT
Traffic Disturbance
8
-
-
0.86 0.14
35
0.00
23
9.1
CHOICE
TEXT
37
-
9.
0.95 0.05
-
-
0.00
Treatment of data
Do you use deflection data in combination
with surface distress data ?
give a short description
CHOICE
9.2.
-
9.2.1
Do you determine homogeneous road sections?
If yes which criteria do you use for
determining homogeneous sections ?
35
0.74 0.26
0.00
CHOICE
level of deflection
35
0.54 0.46
0.00
CHOICE
pavement distress
35
0.66 0.34
0.00
CHOICE
traffic volumes
35
0.74 0.26
0.00
CHOICE
pavement construction
TEXT
other
9
-
37
0.95 0.05
0.00
9.3
CHOICE
In which form do you present the data?
tables
210
37
0.73 0.27
0.00
CHOICE
figures (graph, histograms)
37
0.24 0.76
0.00
CHOICE
geographical (in combination with GIS)
-
33
0.55 0.45
0.00
18
10.
CHOICE
New developments
10.1
Are you aware of any new developments in the
field of deflection measurement collection ?
TEXT
please give a short description
Part III: Pavement Management Systems / General
TYORG
44
NBPAYS
TYPE
CODE
Index of the answer
Name of the answer
Good type
40
TEXT
Surname, initials
35
TEXT
Job title
39
TEXT
Name of employer
40
TEXT
Country
1
TEXT
Phone number
1
TEXT
fax number
0
TEXT
-
-
-
-
Type of Institution
44
0.36 0.64
0.00
CHOICE
Road Authorities (central)
44
0.20 0.80
0.00
CHOICE
Road Authorities (local)
44
0.18 0.82
0.00
CHOICE
Industry
44
0.41 0.59
0.00
CHOICE
Research institutes
41
0.66 0.34
0.00
CHOICE
1.
211
Do you have a Pavement Management
System?
-
-
-
-
1.1
Give one or more reason for not having a
PMS.
3
1.0 0.0
RANK
3
1.0 0.0
RANK
setting up such a system is too much
expensive
4
1.0 0.0
RANK
data acquisition for such a system each year is
too much expensive
existing procedures are efficient
0
RANK
benefits of a PMS are not convincing
9
TEXT
other
10
-
0.60 0.10
-
-
0.30
CHOICE
-
1.2
Do you intend to acquire such a system if the
problems mentioned under 2.1. are solved ?
2.
Give one or more purposes for which you use
the PMS
23
2.1 1.1
RANK
to predict the evolution of the network
27
1.5 0.8
RANK
to determine a multi-year budget for road
maintenance
28
1.8 1.1
RANK
to determine a long term maintenance
scheduling plan for roads
18
2.9 1.8
RANK
to follow-up the efficiency of the maintenance
policy
20
2.2 1.5
RANK
to determine rehabilitation measures for
sections of road
10
2.5 2.3
RANK
for research
TEXT
other
1
General
-
-
-
-
-
-
-
-
2.
Please fill in the road-lengths of your network.
tolled motorways length
7
714.00 1177.13
VALUE
flexible
7
833.29 1477.98
VALUE
composite
7
166.86 214.83
VALUE
rigid
9
1389.78 2387.91
VALUE
total
-
24
553.51 950.02
-
free motorways length
flexible
VALUE
212
24
338.65 1142.87
VALUE
composite
24
126.51 247.43
VALUE
rigid
28
1595.39 2882.28
VALUE
total
-
-
-
-
main road length
25
7254.79 6627.05
VALUE
flexible
25
338.88 903.73
VALUE
composite
25
53.33 91.37
VALUE
rigid
29
10236.97 12292.19
VALUE
total
-
-
-
-
minor road length
19
28241.20 30314.65
VALUE
flexible
19
2068.89 7748.69
VALUE
composite
19
24.95 72.87
VALUE
rigid
22
30646.99 34278.65
VALUE
total
-
-
-
-
urban road length
6
47080.67 41902.42
VALUE
flexible
6
2076.33 3588.38
VALUE
composite
6
3.17 7.08
VALUE
rigid
8
44991.25 39709.59
VALUE
total
213
8.5 Glossary of Common Acronyms
Acronym
AASHTO
ASTM
CEEC
CEN
COST
EC
ECU
EU
FEHRL
FHWA
IRRD
MECU
MoU
OECD
PAVMON
PIARC
R&D
SERRP
SHRP
SoA
TRB
WG
General acronyms
Explanation
American Association of State Highway and Transportation Officials
American Society for Testing and Materials
Central East European Countries
Comité Européen de Normalisation,
European Committee for Standardisation
European Co-operation in Science and Technology
European Commission
European Currency Unit
European Union
Forum of European National Highway Research Laboratories
Federal Highway Administration, USA
International Road Research Documentation
Million ECU
Memorandum of Understanding
Organisation for Economic Co-operation and Development
New pavement monitoring equipment and methods, one of SERRP projects
Permanent International Association of Road Congresses
Research and Development
Strategic European Road Research Programme
Strategic Highway Research Programme
State of the art
Transportation Research Board
Working group
214
Acronym
APORBET
BASt
BFPZ
CEDEX
CROW
CRR, OCW
DRI
DWW
EPFL
ΕΤΗ
GEOCISA
IVT
JAE
KEDE
LCPC
LNEC
NTUA
SINECO
Acronyms of institutions of COST Action 325 Members
Explanation
Associação Portuguesa de Fabricantes de Misturas Betuminosas,
Portuguese Asphalt Association, Lisbon, Portugal
Bundesanstalt für Strassenwesen, Bergisch Gladbach,
Federal Highway Research Institute, Germany,
Bundesforschungs­ und Prüfzentrum Arsenal,
The Federal Institute for Testing and Research at "Arsenal" of Vienna,
Austria
Centro de Estudios y Experimentación de Obras Publicas,
Centre of Studies and Research of Public Works, Madrid, Spain
Centre for Research and Contract Standardisation in Civil and Traffic
Engineering, E de, The Netherlands
Centre de Recherches routières, Opzoekingscentrum voor de
Wegenbouw,
Belgian Road Research Centre(BRRC), Brussels, Belgium,
Vejteknisk Institut,
Danish Road Institute, Roskilde Denmark
Dienst Weg­en Waterbouwkunde,
Directorate­General Rijkwaterstaat, Delft, The Netherlands
Ecole Polytechnique Federal de Lausanne, Switzerland
Eidgenössische Techniche Hochschule,
Swiss Federal Institute of Technology, Zürich, Switzerland,
Geotecnia y Cimientos, S.A.,
Geotechnic and Foundations, S.A., Coslada, Madrid, Spain
Institut für Verkehrsplanung, Transporttechnik, Strassen­ und
Eisenbahnbau,
Institute of Transportation, Traffic­, Highway­ and Railway­E ngineering,
Zürich, Switzerland,
Junta Avtonoma de Estradas,
Portuguese Road Administration, Lisbon, Portugal
Kentriko E rgastirio Demosion E rgon,
Central Laboratory of Public works,Athens, Greece
Laboratoire Central des Ponts et Chaussées,
French National Road and Bridge Research Laboratory, Bouguenais,
France
Laboratorio Nacional de Engenharia Civil,
National Laboratory of Civil Engineering, Lisbon, Portugal
Ethniko Metsovio Polytechnio(E MP),
National Technical University of Athens, Greece
Engineering service for maintenance and monitoring of transport
infrastructures
215
TRL
VTI
VTT
ZAG
Transport Research Laboratory, Crowthorne, United Kingdom
Statens vag-och transportforskningsinstitut,
Swedish National Road and Transport Research Institute, Linköping,
Sweden
Valtion Teknillinen Tutkimuskeskus,
Technical Research Centre of Finland, Helsinki, Finland
Zavod za gradbenistvo Slovenije,
Slovenian National Building and Civil Engineering Institute, Ljubljana,
Slovenia
216
Acronym
ABS
ADAPT
ADHERA
APDIS
APL
ARAN
ARGUS
ARIA
ARS
ASTRA
BELMAN
CALAO
CBR
CREHOS
DOT
EBO
ESAL
FWD
GERPHO
GIS
GPR
GPS
HDTV
HSV
HRM
HYBRID
IMS
IRI
KUAB
Acronyms of Measuring devices and technical terms
Explanation
Anti Block System
Automated Distress Analysis for PavemenT Program
Equipment for longitudinal coefficient of friction to be measured at a selected
speed between 40 and 144 km/h, France
Automatic Pavement Digital Imaging System, Greece
Analyseur de Profil en Long, Longitudinal Profile Analyser
Automatic Road ANalyser
Automatic Road condition Graduating Unit System, Germany
Automated Road Image Analyser, USA
Analyser Regularity Superficial, Spain
Profiles of service value and associated condition, Germany
Pavement Management System used at State Highways in Denmark
Connaitre-Ausculter-Localiser-Analyser-Optimiser, France
Californian Bearing Ratio
Crack REcognition Holographic System
Department of Transportation
Energies par Bandes d'Ondes, Energie for Wave lengths Band, France
Equivalent Standard Axle Load
Falling Weight Deflectometer
Groupe d'Examen Routier Par pHOtographie, Photographic road survey group
High-yield apparatus, France
Geographical Information System
Ground Penetrating Radar
Geographic Positioning System
High Definition Television
High-speed Survey Vehicle, United Kingdom
High speed Road Monitor, United Kingdom
A hybrid system consisting of lasers and video cameras, Sweden
Infrastructure Management System
International Roughness Index
Swedish FWD
217
Acronym
Laser RST=LRST
LSAQ
LTPP
MACADAM
MRM
NASTRA
NCHRP-IDEA
ORCA
PALAS
PARIS
PASCO
PASE
PAVEDEX
PAVETECH
PAVUE
PC
PDDL
PHOTOLOG
PMS
PSI
RDD
RDM
RPUG
RST
SAND
SCARGUS
SCRIM
SFC
SIRANO
SPI
SRM
TVL
VIAGERENDA
WISECRAX
Explanation
Laser Road Surface Tester, Sweden
Laser System for analysing the transverse evenness, Germany
Long Term Pavement Performance
Methode Automatique de CAracterisation des Degradations par Analyse
d'IMage, France
Multifunction Road Monitoring, United Kingdom
Network presentation of the overall value, Germany
National Co-operative Highway Research Program - Ideas Deserving
Explanatory Analyses, United States
Multifunction machine for assessing surface condition, United Kingdom
A laser blanket transfer Profilometer, France
Performance Analysis of Road Infrastructure (E.C. project)
Pacific Aero Survey Corporation, Japan
Pavement Strength Evaluator, Australia
The Videometric Data Acquisition and Computer Image Processing
System, USA
Video Inspection Vehicle, USA
Example of available video surveying system that incorporate automatic
image processing, USA
Personal Computer
Pavement Deflection Data Logging Machine, United Kingdom
videologging equipment from Connecticut, USA
Pavement Management System
Present Serviceability Index
Rolling Dynamic Deflectometer,
Rolling Deflection Meter, Sweden
Road Profiler User Group
Road Surface Technology
BRRC computer based keyboard encoder
A combination of SCRIM and ARGUS
Sideways force-coefficient routine machine, United Kingdom
Side Force Coefficient
System d'Inspection des Routes et Autoroutes par Analyse Numérique et
Optique, France
Sand Patch Index
Stuttgarter ReibungsMesser, Germany
television lines
Belgian secondary road network system
Image processing system for automatic distress evaluation, Canada
218
Members of the Management Committee
8.6
BELGIUM
GREECE
Dr. M. GORSKI
Centre de Recherches routières
Boulevard dc la Woluwc, 42
Β­1200 Bruxelles
Tel
32/2.766.03.80
Fax
32/2.767.17.80
E-mail
brre@pophost.eunet.be
Statusimember
Mr. Nikolaos MICHAS
Ministry of the Environment and Public Works (KEDE)
Athens Regional Laboratory
Kallirrois 144
GR­I1741 ATHE NS
Tel
30/1.595.02.41
Fax
30/1.924.18.63
E-mail
Status:member
DENMARK
ITALY
M. .Ian JANSEN
Danish Road Institute
National Road Laboratory
P.O. Box 235 ­ Elisagardsvej 5­7
DK­4000 ROSKILDE
Tel
45/46.30.01.00
E-mail
Status:rnember,expert,deputy,new member
Mr. Ruggero BENETTI
SINECO S.p.A.
Via Felice Casati IA
1­20124 MILANO
Tel
39/2.29.40.45.13
Fax
39/2.29.40.09.74
E-mail
sineco@mbox.vol.it
Status:member
FRANCE
THE NETHERLANDS
M. Hervé PHILIPPE
LCPC
B.P. 19
F­44340 BOUGUE NAIS Cedex
Tel
33/40.84.58.56
Fax
33/40.84.59.98
E-mail
philippe@,accucil. inrets.fr
Statusimember
Mr. B. de WIT
Dienst Weg­ en Waterbouwkunde Rijkswaterstaat
(DWW)
Postbox 5044
NL­2600GA DE LFT
Tel
31/15.69.91.11
Fax
31/15.61.13.61
E-mail
l.b.dwit@dww.rws.minvenw.nl
Statusimember
GERMANY
PORTUGAL
Dr. KNEPPER
Ms M.da Conceição Monteiro Azevedo
Laboratorio Nacional de Engenharia Civil (LNEC)
Praca de Abvelade 6,4°
Ρ­1799 LISBOA Codex
Tel
351/1.792.80.80
Fax
351/1.793.12.12
E-mail
aporbet@mail.telepac.pt
Status:member,expert,deputy,new member
Fax
45/46.30.01.05
Bundesanstalt tur Straßenwesen (BASt)
Brüderstraße 53
Postfach 10 01 50
D­5060 BE RGISCH GLADBACH 1
Tel
49/2204.43.711
Fax
49/2204.43.673
E-mail
Status:expert
219
Mr Rui BARROS
Junta Autonoma de Estradas a (JAE)
Direcção Serviços de Construção
Divisão de Geotecni
Praça da Portagem da 25 de Abril
P-2800 ALMADA
LISBON
Tel
35.11.294.72.38
Fax
35.11.294.77.95
E-mail
Status:new member
Mrs Carmela FILGUEIRA LOIS
Instituto de Estudios del transporte y las Communicaciones
Ministerio de Obras Publicas y Transportes
Plaza san Juan de la Cruz s/n 6a
E-28071 MADRID
Tel
34/1.547.66.64
Fax
34/1.547.66.43
E-mail
Status (Member or expert):
Dr. Guillermo ALBRECHT ARQUER
GEOCISA
Los Llanos de Jerez 10 y 12
E-28820 COSLADA (MADRID)
Tel
34/1.671.53.00
Fax
34/1.671.64.60
E-mail
Status (Member or expert):
Working group:
SLO VENÍAN REPUBLIC
Mr Bojan LEBEN
Zag
Zavod za grad benistvo-ZRMK
Dimiceva 12
Sl-1000 Ljubljana
Tel
386-61-18-88-506
Fax
386-61-348.369
E-mail bojan.leben@zag.si
Status:deputy
SWEDEN
Mr. Georg MAGNUSSON
Swedish Road and Transport Research Institute
S-58195 LINKÖPING
Tel
46/13.20.41.22
Fax
46/13.14.14.36
E-mail georg.magnusson@vti.se
Status:chairman
MrJanezTOMSIC
ZRMK
Dimiceva, 12
SLO-61000 LJUBLJANA
Tel
386/61.168.32.61
Fax
386/61.34.83.69
E-mail
Status:member
SWITZERLAND
M. Martin HORAT
Swiss Federal Institute of Technology Zurich(IVT)
ETH-Hongerberg
CH-8093 ZURICH
Tel
41-16-33-31-99
Fax
41-16-33-10-39
E-mail
Status:member
MrAleSHOCEVAR
Druzba za Drzavne Ceste-D.D.C
Trzaska 19a
1000 LJUBLJANA
Tel
386/61.178.83.80
Fax
386/61.178.83.78
E-mail
Status:deputy
UNITED KINGDOM
SPAIN
Mr. Paddy JORDAN
Transport Research Laboratory (TRL)
Old Wokingham Road
Crowthorne
GB- Berkshire RG45 6AM
Tel
44/1344.77.07.27
Fax
44/1344.77.03.56
E-mail
Status:member
Dña Dolores CANCELA REY
Instituto de Estudios del Transporte y las
Comunicaciones
Plaza San Juan de la Cruz, s/n
E-28071 MADRID
Tel
34/1.597.72.74
Fax
34/1.597.85.92
E-mail
Status:member
220
EUROPEAN COMMISSION
Mr. Rene BASTIAANS
European Commission
DG VII-A4
BU 31 -5/76
Tel
32/2.299.41.15
Fax
32/2.296.83.50
Mr.LucWERRING
Commission des Communautés Européennes
DG VII
BU3106/87
Tel
32/2.296.84.51
Fax
32/2.296.51.96
Mr. Andrew STIMPSON
European Commission
DG VI1.A.4
BU 33 2/27
Tel
32/2.299.19.14
Fax
32/2.296.37.65
221
8.7
FEHRL Information
FEHRL
FORUM of EUROPEAN NA TION AL HIGHWA Y RESEARCH
LABORATORIES
Address:
c/o Transport Research Laboratory
Old Wokingham Road
Crowthorne
UK - BERKSHIRE RG 45 6AU
Tel
(44)1344 77 02 41
Fax
(44)1344 77 03 56
Secretary General
Status
E-mail
RodA@H.trl.co.uk
Mr. Rod ADDIS
Established in 1989 for EU and EFTA countries, based on the application of a Memorandum of
Understanding.
AIMS AND OBJECTIVES OF FEHRL
The Forum of European National Highway Research Laboratories (FEHRL) was formed in 1989 by the national highway
research laboratories in EU and EFTA countries. At present, the Forum comprise, as full members, the national laboratories in
all member states of the Union, and in EFTA countries. Laboratories in the Czech Republic, Hungary, Poland. Romania and
Slovenia are admitted as Associate members.
The purpose of FEHRL is to encourage collaborative research between European Laboratories and Institutes in the field of
highway engineering infrastructure, leading to the provision of relevant knowledge and advice to governments, the European
Commission, the road industry and road users.
The objectives of collaborative research are :
D
D
G
D
G
to provide input to EU and national government policy on highway infrastructure
to create and maintain an efficient and safe road network in Europe
to increase the competitiveness of European road construction and road-using industries
to improve the energy efficiency of highway construction and maintenance
to protect the environment and improve quality of life
THE PROFESSIONAL FIELDS COVERED BY MEMBERS ARE :
G Geotechnics
G Pavement Engineering G
Bridge Engineering Q Construction Materials Q Maintenance Management Q Environmental Issues G Traffic loading G
Safety at roadworks
ORGANISATION OF FEHRL
The operation of the Forum is based on the application of a Memorandum of Understanding that all members are required to
sign. The Memorandum specifies the rights and responsibilities of members and associates, and describes the organisational
arrangements.
Together, the full members of FEHRL constitute the Board, from whom a President is elected to serve for a half-year
222
FEHRL MEMBERS
Austria
BVFA
Bundesversuchs und Prüfzentrum Arsenal
Belgium
CRR
OCW
Centre de Recherches routières
Opzoekingscentrum voor de Wegenbouw
Denmark
DRI
Danish Road Institute
Finland
VTT
Technical Research Centre of Finland
France
LCPC
Laboratoire Central des Ponts et Chaussées
Germany
BASt
Bundesanstalt für Slrassenwesen
Greece
KEDE
Central Public Works Laboratory
Iceland
PRA
Public Roads Administration
Ireland
NRA
National Roads Authority
Italy
ANAS
Centro Sperimentale Stradale
Luxemburg
INRR
Institut National de Recherche Routière
Netherlands
DWW
Dienst Weg- en Waterbouwkunde Rijkswaterstaat
Norway
NRRL
Norwegian Road Research Laboratory
Portugal
LNEC
Laboratório Nacional de Engenharia Civil
Spain
CEDEX
Centro de Estudios y Experimentación de Obras Publicas
Sweden
VTI
Statens väg- och transportforskningsinstitut
Switzerland
LAVOC
Ecole Polytechnique Fédérale de Lausanne
United
Kingdom
TRL
Transport Research Laboratory
ASSOCIATES
Czech
Republic
HungaryKTI
CDV
Centrum Dopravního Viyzkumu
Transport Research Centre
Institute for Transport Sciences Ltd.
223
8.8
COST Transport Overview
COST Transport is one of 17 domains existing in COST at the present time.
This domain was already considered as one of the priorities in the late sixties, when the Council of
Ministers of the six Member States of the Community was considering the launch of what would
later be known as COST. It was to be one of the seven areas seen as best suited for this new form of
collaboration, which was officially set up by a Ministerial Conference in November 1971.
The Transport area lends itself particularly well to the COST framework, both because it combines
aspects from a number of disciplines, and because of the need for harmonisation at European level.
Liaison with the Transport Ministries and Administrations in the various countries is a key element
of these COST Actions.
The COST Transport Secretariat is located within the Directorate General for Transport of the
European Commission. The location with the staff managing the Fourth Framework Transport RTD
Programme, as well as the proximity with the Common Transport Policy Directorates, enables close
collaboration between Transport Research activities and serves as a basis for further political action.
COST Transport Actions are authorised and supervised by the COST Technical Committee on
Transport (TCT) which, in turn, reports to the COST Committee of Senior Officials (CSO). Both of
these decision making bodies comprise representatives of the national governments of the COST
countries.
COST-Transport Actions Underway
COST 317
COST 318
COST 319
COST 321
COST 323
COST 324
COST 325
COST 326
COST 327
COST 328
COST 329
COST 330
COST 331
COST 332
COST 333
COST 334
COST 336
COST 337
COST 335
Socio-economic effects of the Channel Tunnel
Interactions between high speed rail and air passenger transport
Estimation of pollutant emissions from transport
Urban goods transport
Weigh in motion of road vehicles
Long term perfonnance of road pavements
New pavement monitoring equipment and methods
Electronic marine chart display
Motorcycle safety helmets
Integrated strategic infrastructure networks in Europe
Models for traffic and safety development and interventions
Teleinformatics links between ports and their partners
Requirements for pavement markings
Transport and land-use policies
Development of new bituminous pavement design method
Effects of wide single tyres and dual tyres
Falling weight deflectometer
Unbound granular materials for road pavements
Passengers accessibility of heavy rail systems
224
COST-Transport Completed Actions
COST 30:
Electronic aids to traffic on major roads
COST 30bis: Same aim as COST 30 but with demonstration action
COST 33:
Forward study of passenger transport requirements between major European
conurbations
COST 301
Shore based marine navigation aid systems
COST 302
Technical & economic conditions of the utilisation of electric road vehicles in Europe
COST 303
Technical and economic evaluation of dual-mode trolleybus national programmes
COST 304
Alternative fuels for road vehicles
COST 305
Data system for the study of demand for inter-regional passenger transport
COST 306
Automatic transmission of data relating to transport
COST 307
Rational use of energy in inter-regional transport
COST 308
Maintenance of ships
COST 309
Road weather conditions
COST 310
Freight transport logistics
COST 311
Simulation of maritime traffic
COST 312
Effects of the Channel Tunnel on traffic flows
COST 313
Socio-economic cost of road accidents
COST 314
Express delivery services
COST 315
Large containers
COST 320
Effects of E.D.I, on transport
COST 322
Low Floor Buses
COST Transport Actions in Preparation
COST 338:
COST 339:
Information overload in the field of traffic signs
Technical and economic conditions for the use of small containers (logistic box)
at European level
225
European Commission
EUR 17547 —COST 325 — New Road Monitoring Equipment
and Methods
Luxembourg: Office for Official Publications of the European Communities
1997 — 227 pp. — 17,6 χ 25,0 cm
ISBN 92-828-0307-4
Price (excluding VAT) in Luxembourg: ECU 24
The Report of COST Action 325 describes the research carried out to establish the operational
requirements for equipment capable of measuring and evaluating the surface distress and load
bearing capacity of roads at traffic speeds. Thirteen countries participated in this four-year
study which provides a basis for the development of suitable equipment to meet the present
and foreseeable needs of road network managers in Europe.
The study initially involved a questionnaire survey of European countries in which present
methods of evaluating surface distress and load bearing capacity were assessed and needs were
identified. Secondly a review of the literature on state of the art equipment and on-going devel­
opments was undertaken. Finally, the information on needs and developments was analysed to
define the technical and operational requirements of equipment that would meet the present
and foreseeable future needs of road network managers.
The report concludes that fully automated high-speed equipment for assessment of surface dis­
tress and load bearing capacity could be available for routine use within a period of about eight
years. Further, that the use of multi-function equipment, capable of measuring both road sur­
face condition and load bearing capacity, would enhance the accuracy of condition assessment,
reduce the cost of data collection and improve safety for the personnel involved in monitoring
the condition of road networks.
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