See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/273694365
Synthesis of Safety Aspects of Highway Design Features - Alignment and Access
Management
Technical Report · March 2015
DOI: 10.13140/RG.2.1.3697.3603
CITATIONS
READS
0
949
1 author:
Sohrab Siddiqui
Montana State University
8 PUBLICATIONS 8 CITATIONS
SEE PROFILE
All content following this page was uploaded by Sohrab Siddiqui on 18 March 2015.
The user has requested enhancement of the downloaded file.
Research Exercise II
Synthesis
of
Safety Aspects of Highway Design Features
Alignment and Access Management
by
Sohrab Siddiqui
for
ECIV 554-Transportation Safety
Date: 03/10/2015
Abstract
The United States has developed an extensive transportation network that is unsurpassed by any country in
the world. It has provided unprecedented mobility for its citizens by connecting the vast road networks to
air, rail, and urban transit services. Freight is easily moved via intermodal network of shipping, ports, rail,
and highway freight carriers. This system is not without any failings. The most critical problem facing the
transportation industry in the United States is to assure as safe environment for the drivers and passengers.
Many analyses of motor vehicle crashes indicate driver error as the major contributor to crashes (1).
However it should not be construed to mean there is little that the highway designer can do to improve the
level of safety for drivers and passengers. In fact, a highway designed with explicit attention to safety can
significantly reduce the frequency of crashes and their severity. Such a highway is called “forgiving”
because its design mitigates the consequences of driver error.
In a sense, the roadway provides instructions to the road users on what they should be doing. Negative road
engineering factors directly triggers a crash and misleads a road user to commit human errors. As the first
element of a safe road, geometry of the roadway plays a significant role in road crash frequencies as well
as crash severity levels.
The purpose of this report is to point out two of the most important highway design features that if not taken
care of can have serious impacts on safety. These elements include horizontal and vertical alignment of a
highway and access management. The paper is organized in a synthesis format and reports on current
knowledge and practice, in a compact form, without any detailed directions that are usually found in
handbooks or design manuals. Author’s discussion of various safety statistics is provided for every topic
discussed in the pertaining section. A conclusion/discussion in the last part of the report reflects the author’s
overall perspectives on the issues presented.
Introduction
During the past few decades a considerable amount of research has been performed on all aspects of
geometric design affecting the way roads are designed, the way they operate, and, ultimately, the safety of
these facilities. Using and applying this knowledge is sometimes limited because of the sheer volume of
information that exists and the rapid pace in which it is produced and published. Besides that, various
researches done on Geometric design research are scattered across a variety of different tools and
publications that are not easily accessible to highway and street designers and policy makers. This report
would try to synthesize the most recent updates on two of the most important issues of geometric design
namely, alignment and access management.
New interests were attracted to safety and geometric design by late 1980s. Beginning in 1988, a series of
sessions were launched by Transportation Research Board (TRB) committees on Geometric Design and
Operational Effects of geometric Design. The sessions were organized to discuss the state of the practice
of five geometric design topics: sight distance, interchanges, intersection, alignment and cross sections (2,
3). These sessions continued for five years and as a result of it a broad range of research problem statements
were submitted to and funded under the National Cooperative Highway Research Program (NCHRP).
Meanwhile, Federal Highway Administration (FHWA) management designated Highway Safety Design
Practices and Criteria as a high-priority research and development (R&D) area in March 1988. The main
purpose of this program was to develop an integrated design process considering roadway and roadside to
develop cost effective design alternatives.
2
A series of computer modules were developed as part of this project including a roadway module (which
covered multivehicle accidents); a roadside module (which covered single-vehicle accidents); a consistency
module (which was based on speed profiles, since large changes in speed between successive roadway
sections are believed to contribute to accidents); and a physics module (which measured speeds and lateral
accelerations based on a computer simulation of the interaction between the vehicle and the roadway). This
program was envisioned by first selecting a design alternative developed by a highway designer in
accordance with the guidelines and then checking for potential safety problems against safety data in each
of the modules. The designer would have to decide how to solve any potential safety problems identified
through the process.
The initial concept of the components of the integrated design process developed by FHWA management
team is shown in Figure 1 (4).
Design
Alternatives
Roadside Module
Roadway Module
INTEGRATED
DESIGN
PROCESS
Consistency Module
Physics Module
Revised
Alternatives
Figure 1- Initial Concept of Integrated Design
The program's first product was a six-volume synthesis on highway safety research.(5) This study
specifically addressed access control, alignment, cross sections, interchanges, intersections, and pedestrians
and bicyclists; topics selected based on recommendations from TRB and earlier synthesis studies.(6,7)
These issues clarified the concept of what is now known as the Interactive Highway Safety Design Model
(IHSDM).
IHSDM is a software currently used for evaluating safety and operational effects of geometric design
decisions on two-lane rural highways but is expected to expand very soon to incorporate all other types of
highways. The software can easily be downloaded from FHWA website and the link is provided for the
reader in the references section of the report. (31)
Several other methods were also developed to relate the series of events in a road crash to categories of
crash-contributing factors. One such method is the Haddon Matrix (8). According to this matrix developed
by William Haddon Jr. in 1970, there are three different types of factors that contribute to road crashes: a)
Human Factors b) Vehicle Factors and c) Roadway/Environment Factors. Roadway Factors include
3
roadway and roadside design elements. According to the Highway Safety Manual (HSM) (9) of the
American Association of State Highway and Transportation Officials (AASHTO), three percent (3%) of
road crashes are due to only roadway factors, but thirty four percent (34%) of road crashes are a combination
of roadway factors and other factors (see Figure 2).
93%
34%
Human
Factors
27
Roadway
Factors
57
3
3
6
1
Vehicle
Factors
3
3%
Figure 2- Contributing factors to Vehicular Crashes
A major percentage of roadway/roadside crashes can be contributed to poorly-designed vertical and
horizontal alignment and poorly managed access to different types of land uses. In the next section of this
report a roughly detailed investigation is conducted on the safety aspects of these highway design features.
Horizontal and Vertical Alignment
Design of vertical and horizontal alignment is integral part of any highway design project. Usually design
is governed by design speed which is based partially on safe stopping sight distance. Therefore one can say
that horizontal and vertical curvature of a highway determines the safe sight distance and operating speed
of that highway. The correct combination of vertical and horizontal alignment promotes uniform speed for
the motorist traveling on the highway, and thus contributes to a safe design. A more thorough investigation
of the safety remediation is beyond the scope of this paper. This paper only presents safety issues associated
with horizontal and vertical alignment.
a) Stopping Sight Distance (SSD)
Minimum safe stopping sight distance is one of the major factors affecting the cost and environmental
impacts of a road design. It has direct influence on size and other design elements. Very little is known
about the relationship between sight distance and safety. These researches are part of the general literature
about safety implications of SSD:





Yagar and Van Aerde (10) found that sight distance was not a major contributory factor in
controlling vehicle speeds.
A study done in UK (11) showed that accident rates rise steeply at sight distances below 100m and
sight distance above 500m have little effects on accidents.
According to TRB Special Report 214 (12), accident frequencies were 52 percent higher in
locations with sight reduction than locations with adequate sight distance
A study by Hall and Turner (13) indicated that inadequate sight distance does not guarantee that
accidents will occur.
A study in Sweden (14) indicated that accident rates decrease with increasing average sight distance
especially for single-vehicle crashes in dark environment.
4
b) Horizontal Curvature
Studies indicate that the rate of accident are higher in horizontal curves compared to tangent segments. This
rate can range from one and a half to four times greater than the tangent segments (15-17). According to
the past literature, the following features are related to safety of horizontal curves:
•
•
•
•
•
•
•
•
•
•
Traffic volume on the curve and traffic mix (e.g., percent trucks).
Curve features (degree of curve, length of curve, central angle, superelevation, and presence of
spiral or other transition curves).
Cross-sectional curve elements (lane width, shoulder width, shoulder type, shoulder slope).
Roadside hazard on the curve (clear zone, sideslope, rigidity and types of obstacles).
Stopping sight distance on curve (or on curve approach).
Vertical alignment on horizontal curve.
Distance to adjacent curves.
Presence/distance from curve to the nearest intersection, driveway, bridge, etc.
Pavement friction.
Presence and type of traffic control devices (signs and delineation).
Based on a study of 3,427 curve/tangent pairs in Washington State by Zegeer, et al. it was indicated that
accident factors are overrepresented on curves compared to tangents. Accidents on curves included more
severe (fatal and A-type injury) crashes, head-on and opposite direction sideswipe crashes, fixed-object and
rollover crashes, crashes at night, and those involving drinking drivers. Table 1 indicates the distribution of
curve crashes by severity and type (17):
Table. 1- Summary of Accident Statistics on Washington State Curve
Sample
Variable
Frequency
Percentage
Total Accidents
12,123
100.0
PDO Accidents
6,500
53.6
Injury Accidents
5,359
44.2
Fatal Accidents
264
2.2
People Injured
8,434
N.A.
People Killed
314
N.A.
Head-On Accidents
517
4.3
Opp. Direction Sideswipe Accidents 468
3.9
Fixed Object Accidents
5,045
41.6
Rollover Accidents
1,874
15.5
Same-Direction Sideswipe
139
1.1
Rear-End Both Moving
303
2.5
Other Collision Types
3,777
31.2
Dry Road Accidents
Wet Road Accidents
Snowy/Icy Road Accidents
Daylight Accidents
Dark, Dawn, Dusk Accidents
5
6,914
2,609
2,600
6,828
5,295
57.0
21.5
21.4
56.3
43.7
In a study done by Srinivasan (18), it was noted that an isolated narrow curve in an otherwise straight
alignment is more dangerous than a succession of curve of the same radius. It was also noted that horizontal
curves are more dangerous when they are combined with gradients and surfaces of low friction coefficients.
Brenac (19) indicated that short radius curves are only dangerous if there is a road alignment anomaly like
a difficult isolated bend in an otherwise easy section. A number of other studies indicate that horizontal
realignment of rural highways is the most efficient way of increasing safety; reduction in number of
accidents of the order of 80 percent have been reported (18). Table 2 shows the results of a Swedish study
on accident reduction factors for various increases in horizontal radii:
Table.2- Accident Reduction Factors for various increases in horizontal
radii
To (m)
500
700
1500
From (m)
300
0.25
0.35
0.45
500
0.10
0.30
700
0.20
As we can see from the table, increasing the radius from 300m to 1500m has more effects than increasing
the radius from 500m to 1500m.
Brenac (19) also found that curve radii below 200m limited the speed on curves to less than 90 km/h.
Simpson and Kerman (20) also found that there is only a minor decrease in speed by driver approaching
horizontal curves.
Wider lanes and shoulders on curves are also associated with a reduction in curve-related accidents. Percent
reductions in total accidents are given in Table 3 for improvements involving widening lanes and/or
shoulders on horizontal curves. (17)
Table.3- Percent reduction in accidents due to lane and shoulder widening.
Total Amount of Lane or
Shoulder Widening (ft)
Total
Per Side
2
4
6
8
10
12
14
16
18
20
1
2
3
4
5
6
7
8
9
10
Percent Accident Reduction
Lane
Widening
5
12
17
21
-
6
Paved Shoulder
Widening
4
8
12
15
19
21
25
28
31
33
Unpaved Shoulder
Widening
3
7
10
13
16
18
21
24
26
29
Other factors are also influential in reducing the number of horizontal curve crashes but are not presented
here to respect the word limits. These factors include but are not limited to spiral transitions, superelevation
improvements and roadside improvements on curves.
c) Vertical Curvature
The vertical alignment of a highway is described by vertical lines or grades, and vertical curves. The vertical
curve can be crest or sag based on ground conditions. According to studies, downgrades have 63% more
accidents than upgrades, considering uniform vehicular traffic for both. Table 4 shows the number of
accidents and fatality rates for different types of vertical curves. It shows that downgrade accidents are more
frequent and result in higher percentages of injuries and fatalities than upgrade accidents. Also, injury and
fatality rates on vertical curves are higher than on level or upgrade locations. (21)
Table.4- Accident frequency and severity by vertical alignment.
Vertical
Number of
Percent of Total
Percent
Percent
Alignment
Accidents
Accidents
Injured
Killed
Level
2001
34.6
53.6
4.7
Upgrade
943
16.3
55.6
3.9
Downgrade
1533
26.5
58.4
5.1
Up on crest
373
6.5
59.5
6.0
Down on crest
461
8.0
62.6
5.9
Up on sag
258
4.5
57.8
6.3
Down on sag
211
3.7
61.7
6.8
Total Known
5780
100.0
Unknown
2192
Total
7972
Mullins, et al, showed that the reason for higher number of accidents on the peak of the crests and uphill
portions of sag is the general lack of sight distance. (22)
Other studies (23) assessed the safety of various truck combinations on vertical curves. It was found that
truck are more prone to accidents on grades than on level terrain. Table 5 shows the distribution of accidents
by truck type and grade measurement of the roadway. (23)
Table.5- Distribution of accidents by vertical grade measurement and truck type
Vertical Slope Measurement
Truck
Type
Straight
N
%
(%)
Singles
Doubles
%
(%)
N
%
(%)
Down
Down
Down
Level
Up
Up
Up
Total
6-7%
3
1
(7
27
2
(12
20
8
(34
4-5%
8
3
20
19
4
21
23
9
39
2-3%
30
14
73)
152
12
67)
16
6
27)
234
74
851
66
163
62
-
2-3%
30
9
(71
151
12
(70
19
7
(48
4-5%
7
2
17
44
3
20
11
4
28
6-7%
5
2
12)
20
2
9)
10
4
25)
317
100
1294
100
262
100
-
7
As can be seen from the table, double trailer combinations appear to have more problems on downgrades
than other truck or trailer combinations.
Table 6 provides information on vertical slope by different types of roadways. (23) As we can see
accident are more acute to rural freeways.
Table. 6- Distribution of truck accidents by vertical grade measurement and roadway type
Vertical Slope Measurement
Roadway
Down Down Down
Level
Up
Up
Up
Type
6-7%
4-5%
2-3%
2-3%
4-5%
6-7%
Rural
N
43
62
93
388
95
33
38
Freeway
%
6
8
12
51
13
6
3
Rural
11
14
13
111
12
8
6
Non-freeway
%
6
8
7
63
7
5
0
Urban
N
18
103
675
104
22
1
Freeway
%
2
11
73
11
2
0
Urban
N
3
185
7
Non-freeway
%
2
95
4
Total
N
54
94
212
1359
218
68
43
%
3
5
10
66
11
3
2
8
Access Management
According to 2003 TRB Access Management Manual (24), Roadway access management is defined as
follows:
The systematic control of the location, spacing, design, and operation of driveways, median openings,
interchanges, and street connections to a roadway. It also involves roadway design applications, such as
median treatments and auxiliary lanes, and the appropriate spacing of traffic signals. The purpose of access
management is to provide vehicular access to land development in a manner that preserves the safety and
efficiency of the transportation system.
Access-related vehicular maneuvers and volumes can have serious consequences on the performance of
traffic operations and road safety. Managing access requires several trade-offs between land access and
through-traffic mobility functions that are implicit in functional classification of all roadways. Access
Management as a function of functional hierarchy according to TRB Access Management Manual (24) is
illustrated in Figure 3.
Figure 3- Conceptual roadway functional hierarchy.
According to Williams and Levinson (25), during the past several decades, access management has grown
dramatically from its origin when it was applied on the boulevards to the comprehensive systemwide
programs. Many NCHRP reports, work by TRB Access Management Committee and publications by
FHWA, ITE and TRB have focused on this issue and have provided the research community with plethora
of researches.
Since the purpose of this paper is to only discuss the safety issues associated with access management, there
will be no description of other aspects of this topic.
Access Control and Safety
From a traffic engineer’s point of view, it is always safe to eliminate unexpected events and to separate the
decision points for the driver. One way to do this is to control the access. It reduces the variety and spacing
of events to which a driver should respond. In a report to congress (26), the effects of access on accidents
and fatalities in urban and rural areas were highlighted. It consisted of data from 30 states and the conclusion
9
was that full control of access is the most safe design factor for accident reduction. According to Table 7
accidents and fatalities on facilities with full control of access is ½ that of the rural highways with no access
control and 1/3 that of urban highways with similar design.
Table.7 – Effect of control of access on accidents and fatalities
in urban and rural areas
Accident Rates per million vehicle miles
Urban
Rural
Access
Control
Total
Fatal
Total
Fatal
Full
1.86
0.02
1.51
0.03
Partial
4.96
0.05
2.11
0.06
None
5.26
0.04
3.32
0.09
Another study was conducted in 1959 by Bureau of Public Works (BPR) to determine the safety of interstate
system. The study sites included the primary highways which were built before the interstates that either
remained parallel to the interstates or replaced by them. The results are documented in several reports with
the most comprehensive one in report by Fee et al. (27) Table 8 indicates the accident, injury and fatality
rates by highway type and type of area for primary highways and interstates. As we can see, interstates have
consistently better safety records as compared to primary existing roads before or after the interstate opened.
Table.8 – Accident, injury and fatality rates by highway type and type of area
Total Urban
Total Rural
Accidents
Safety Rates per million vehicle miles
Interstate
Before
After
Interstate
Corridor
637
601
194
332
Injuries
259
280
102
162
Fatalities
3.4
3.4
2.6
2.9
Accidents
213
230
94
131
Injuries
137
151
57
83
Fatalities
7.6
6.8
3.3
4.3
The study also documented the types of accidents occurring on the interstates. We can see from Table 9
that head-on crashes are virtually eliminated and angle collisions are reduced to a greater extent.
Table.9- Percentage of Accident Type on rural and urban interstate and primary
highways
Rural
Highway Type Head-on
Single Veh.
Rear-end
Angle
Other
Interstate
2.6%
51.1%
30.7%
4.0%
11.6%
Existing
12.4%
30.1%
40.7%
13.8%
3.0%
Urban
Interstate
2.0%
28.9%
59.7%
8.0%
1.4%
Existing
7.3%
10.5%
56.3%
22.2%
3.7%
10
Roadside Access
Besides the comparative analysis, various regression models were also developed in this report to indicate
that which elements of a non-interstate highway contributed most to the safety problems. (27) Effects of
roadside development and intersection frequency were studied. Figure 4 and Figure 5 show the effects of
such developments:
Figure 4- Accident Rate on non-interstate
highways by number of businesses per mile
Figure 5- Accident Rate on non-interstate highways
by number of at-grade intersections per mile
As we can see from above, as the number of roadside developments or intersections increase, the accident
rates increase as well.
McGuirk found a number of interacting variables affecting accidents which includes number of lanes,
commercial driveways, intersections and interchanges per mile, commercial driveways per mile, driveways
per mile and urban area population. (28)
Median Treatments
Presence of medians can have significant impacts on highway safety as it can increase the number of left
turners which in turn increases the number of vehicular conflicts with pedestrians and bicyclists. (24).
In a study documented in NCHRP Report 420 (29), the effects of roadway medians were noted as important
bearing on how well the roadways operate, their safety experience and the access they provide to different
land uses. Three types of median treatment can be part of any highway project:
•
•
•
Whether to install a continuous Two-way-left-turn-lanes (TWLTL)
Whether to install a non-traversable (physical) median on an undivided roadway
Whether and when to replace a TWLTL with a non-traversable median
Different studies report different crash statistics for median treatments. Gattis compiled the studies on
median treatments done over half a century into a single document. Table 10 can be a general comparison
between different types of median treatments. The general trend is that non-traversable medians are
11
associated with lower crash frequency. Continuous two-way left-turn lanes generally are preferable to
undivided roadways, but generally are not preferable to non-traversable medians (30).
Table. 10- Relative safety of cross-section design alternatives
Interchanges
Interchanges are now very important means of moving traffic between freeways and arterials. An
interchange area attracts much land development activity because of the traffic volumes in the vicinity.
Although access is needed to be managed along the entire length of a freeway, including the interchange
area, many transportation agencies apply little, if any, access management along the crossroad (29).
12
Often intersections very close to ramp termini develop heavy weaving volumes requiring complex traffic
signal operations and frequent accidents and congestion problems. Therefore, land development at
interchanges should be sufficiently separated from ramp terminals. However, street intersections along the
arterial often are spaced too close to interchanges.
Many transportation agencies have a growing recognition that access separation distances and roadway
geometry should be improved from an access management perspective. NCHRP Synthesis 332 was
prepared to document and summarize practices relating to access location and design in the vicinity of
interchanges. It basically recognizes the ways to retrofit existing interchanges and strategies to use on new
interchanges.
Conclusion/Discussion
Although the relationship between geometric design factors and accident rates is complex and usually it not
fully understood, this report provided many information about these relationships. It has been clearly shown
that restrictive geometric design elements like short sight distances or sharp curves can be associated with
higher accident rates. It is also shown that significant reductions in values of some of the elements of
geometric standards do not result in large increases in crash rates.
One limitation of this study can be the different definitions and different parameters used by different
researchers. These parameters can include the types of accident, omission of traffic volume, speed and
traffic composition, presence of bicyclists and pedestrian and etc. Driver behavior, enforcement practices
and actual road environment in different countries or different states within the United States can also be
contributors in limiting the way we can interpret the results.
International experiences have shown that interventions in terms of road infrastructure to improve the road
environment can pay for themselves and the financial investments can be recovered within a reasonable
period of time. This can itself be an indication of the importance of investing to improve safety. Although,
as discussed, driver behavior can have a major impact on safety, building a safe environment for the drivers
and passengers can decrease safety issues considerably. This is very well presented by Ernest Greenwood
in a quote, “Accidents, and particularly street and highway accidents, do not happen - they are caused”.
References
1- Highway Safety Design and Operations Guide 1997, American Association of State Highway and
Transportation Officials, Washington D.C.
2- Neuman, T.R. (1989). "New Approach to Design for Stopping Sight Distance." Transportation
Research Record, 1208.
3- Holzmann, F.D. and Marek, M.A. (1993). "Interchange Study and Selection Process."
Transportation Research Record, 1385
4- D.W. Hardwood, J.M. Mason, and J.L. Graham. Conceptual Plan for an Interactive Highway
Safety Design Model, FHWA-RD-93-122, Federal Highway Administration, Washington, D.C.,
February 1994.
5- Safety Effectiveness of Highway Design Features, Volume I: Access Control (FHWA-RD-91044), Volume II: Alignment (FHWA-RD-91-045), Volume III: Cross-Sections (FHWA-RD-91046), Volume IV: Interchanges (FHWA-RD-91-047), Volume V: Intersections (FHWA-RD-91048), Volume VI: Pedestrians and Bicyclists (FHWA-RD-91-049), Federal Highway
Administration, Washington, D.C., 1992.
6- Designing Safer Roads--Practices for Resurfacing, Restoration, and Rehabilitation, Special
Report 214, National Research Council, Transportation Research Board, Washington, D.C., 1987.
13
7- Synthesis of Safety Research Related to Traffic Control and Roadway Elements, Volume 1
(FHWA-TS-82-232), Volume 2 (FHWA-TS-82-233), Federal Highway Administration,
Washington, D.C., 1982.
8- Haddon, W. A Logistic Framework for Categorizing Highway Safety Phenomena and Activity.
The Journal of Trauma, Vol. 12, Lippincon Williams and Wilkins, Washington, DC, 1972 pp.
193-207
9- American Association of State Highway and Transportation Officials (AASHTO). 2010.
Highway Safety Manual. 1st Ed. Washington, DC.
10- Yager, M. and Van Aerde, R. Geometric and Environmental Effects on Speeds of 2-Lane
Highways. Transportation Research, Vol. 17A, No 4. 1983
11- Halcrow Fox and Associates. The Effect of Safety of Marginal Design Elements. A Report for the
Department of Transport, 1981.
12- Transportation Research Board, SR 214, Designing Safer Roads, Practices for Resurfacing,
Restoration and Rehabilitation, 1987.
13- Hall J.W., Turner D.S., Stopping Sight Distance: Can we see where we now stand?
Transportation Research Record 1208. 1989.
14- Andersson, K., Nilsson, G. Models for a Description of Relationships between Accidents and the
Road’s Geometric Design. VTI Report 153, 1978
15- Smith, S., Purdy, J., McGee, H., Harwood, D., St. John, A., and Glennon, J. Identification.
Quantification and Structuring of Two Lane Rural Highway Safety Problems and Solutions.
Volumes I and II, Report Nos. FHWA/RD-83/021 and 83/022, Federal Highway Administration,
Washington, D. C., June 1983.
16- Glennon, J., Newman, T., and Leisch, J. Safety and Operational Considerations for Design of
Rural Highway Curves, Report No. FHWA/RD-86/035, Federal Highway Administration,
Washington, D.C., December, 1985.
17- Zegeer, C., Stewart, J., Council, F., and Reinfurt, D. Cost- Effective Geometric Improvements for
Safety Upgrading of Horizontal Curves, Report No. FHWA-RD-90-021, Federal Highway
Administration, Washington, D.C., October, 1991.
18- Srinivasan, S. Effect of Roadway Elements and Environment on Road Safety. Institution of
Engineers, Vol. 63, 1982
19- Brenac, T., Speed, Safety and Highway Design. Recherche Transports Securite, English Issue,
No. 5, 1990
20- Simpson D., Kerman J.A., The Research and Development Background to Highway Link Design,
Traffic Engineering and Control. 23 (9), 1982.
21- Brinkman, C., and Perchonok, K. Hazardous Effects of Highway Features and Roadside Objects
Highlights. Public Roads, Federal Highway Administration, Washington, D.C., 1979, pp. 8-14.
22- Mullins, B., and Reese, C. Freeway Traffic Accident Analysis and Safety Study, Highway
Research Board Bulletin 291, Texas Transportation Institute, A&M. College of Texas, College
Station, TX, 1961, pp. 26-78.
23- Vallette, G., McGee, H., Sanders, I., and Enger, D. The Effect of Truck Size and Weight on
Accident Experience and Traffic Operations. Biotechnology. Inc., Falls Church, VA, 1981, pp. 1138.
24- Access Management Manual, Transportation Research Board, Washington, D.C., 2003.
25- Williams, K.M. and H.S. Levinson, Access Management: Past, Present, and Future, presented at
the 8th National Access Management Conference, Baltimore, Md., July 14, 2008.
14
26- Stover, Vergil G., Tignor, Samuel C., and Rosenbaum, Merton J., Chapter 4- Access Control and
Driveways, Synthesis of Safety Research Related to Traffic Control and Roadway Elements Vol.
1, FHWA-TS-82-232, Washington, D.C., 1982.
27- Fee, Julie Anna, Beatty, Richard L., Dietz, Stephen K., Kaufman, Stephen F., and Yates, John G.,
Interstate System Accident Research Study 1, U.S. Government Printing Office, Washington,
D.C., October 1970.
28- McGuirk, W.W., Evaluation of Factors Influencing Driveway Accidents, Joint Highway Research
Project Report Number 10, Purdue University, West Lafayette, Indiana, 1973.
29- Gluck, J.S., H.S. Levinson, and V. Stover, NCHRP Report 420: Impacts of Access Management
Techniques, Transportation Research Board, National Research Council, Washington, D.C.,
1999.
30- Gattis, J.L., Assess the Need for Implementing an Access Management Program, TRC 04-04,
Arkansas State Highway and Transportation Department, Little Rock, Sep. 2005.
31- IHSDM software download link, http://www.ihsdm.org/wiki/Download_Registration
15
View publication stats