TG „Road Safety“
Self-explaining roads (SER)
Fact sheet and common conclusions (1st draft)
1. Definition
Self-explaining roads are intended to provide information to road users on the course and the
situation on the road ahead and aim at inducing an adequate driving behaviour by the road
layout itself.
The technical term “self-explaining roads” should be clearly distinguished from telematic
systems or “intelligent roads”. Although systems like VMS or Speed Alert are used for similar
reasons and can support the self-explanatory character of a road, the basis for “selfexplaining roads” are road design elements.
2. Self-explaining roads – Concepts, Effects and Benefits
Generally, two different approaches of self-explaining roads can be distinguished:
1. The “self-enforcing” road
2. The “standardised” road
The layout of self-enforcing roads should prevent road users from driving at inadequate
speeds and encourages motorists to overtake only at stretches where overtaking would be
safely possible. However, more knowledge on the effect of road layout and road elements on
driving behaviour is required to design roads which match these high demands in every
situation. These difficulties especially concern rural roads where most fatalities are caused
by speed related driving and overtaking accidents.
Therefore current self-explaining road approaches follow the concept of standardisation to
reduce contradictions between road user’s expectations and the actual situation on the road.
This is done by assigning traffic regulations and a clear, unambiguous road design to road
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categories. In comparison to self-enforcing roads in this way the driving behaviour is only
indirectly influenced.
The requirements for standardised road concepts are:

Roads of the same road category (same function, traffic mix and speed limit –
functionality-) have to look similar

Roads with different functions, different traffic modes or speed limits have to be
markedly different from roads of other categories

The layout has to match the expectations of the road users and help to induce the
appropriate behaviour (recognizabilty and predictability of the road, homogeneity of
speed and direction)),

The road gives the possibility to correct mistakes (forgiveness of road and roadside)
One pre-condition for the successful implementation of this concept is the definition of a
limited number of different road categories and layouts, as well as the clear assignment of
the whole road network to these road categories. The different layouts have to include
elements which help road users to distinguish between different road categories. These
elements have to be continuously visible like road markings and cross-section dimensions.
Adequate regulations as well as compatible intersection types support the acceptability of the
concept.
Effects/Benefits
Road users' behaviour is considered to be one very important source of improvement for
road safety. Approximately 90% - 95% of all road accidents are caused by human errors. By
avoiding unexpected situations, the number and the consequences of driving errors can be
reduced.
Existing SER concepts for the rural road network use different types of cross-sections and
intersections for different road categories, as well as traffic regulations which are appropriate
to the function and safety needs of the particular road categories such as gradual speed
limits or the regulation of overtaking and traffic mixes.
Self explaining road concepts have two possible positive effects. Assigning safe and
appropriate road design elements to regulations has a direct effect on road safety, while
influencing the driving behaviour has an additional potential to increase road safety.
*** Results of ERA-Net Road project ? ***
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3. CEDR member countries’ experience with SER
Table 1 summarizes the current status of the application of SER in the CEDR member
countries.
Three practical examples of self-explaining road concepts for rural roads have been
identified in Europe. These concepts introduce different speed and traffic regulations for
different road categories and provide similar solutions to prevent head-on collisions.
Although similar layouts can be identified there also are some differences due to design
philosophies and local conditions. The distinguishability is mostly achieved by conspicuous
markings and considerable different cross-section dimensions.
In the Netherlands self-explaining roads are one part of the sustainable safety concept.
Based on a reorganisation of the functional categorisation plan in 1997, three categories for
the rural road network have been defined according to the traffic functions mobility,
distribution and access. From 1997 onwards, all the measures and modifications of parts of
the network, are in line with this categorisation plan. One of the most important modifications
was a coherent marking-plan during the last 5 years to improve the recognisability of the
function of the road.
In Denmark a system of road categorisation according to speed-classes has been proposed
and applied in a pilot study which uses eight road categories according to the traffic functions
(mobility, distribution and access) and different speed levels (high, medium, low).
In Germany the forthcoming road design guidelines for rural roads propose four different
road types, categorised according to their function and the importance of connections, each
type comprising a distinguishable and standardised road layout.
Sweden?
In France several projects have been started to better understand the influence of road
infrastructure on driving behaviour in order to further increase road safety. Among others, the
projects comprise the collection of experiences on national and local road networks, the
analysis of determinative factors and road user behaviour, the improvement of road legibility
processes (guide book and technical notes do exist), field tests of new road designs such as
2 x 1 lane layout with overtaking lanes, mini-roundabouts in interurban zones, and a full scale
test on a road project. Moreover in 2006, the French Ministry organised a seminar with more
than 600 participants on recent developments to induce calm driving. The seminar also
included presentations from Switzerland and the Netherlands.
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Table 1: SER in CEDR member countries
CEDR
Country
Austria
Belgium
Denmark
Estonia
Finland
France
Germany
Greece
Hungary
Iceland
Ireland
Italy
Latvia
Lithuania
Luxembourg
Netherlands
Self-explaining roads in CEDR member countries
Application
Whole road network? Guideline/directive
[yes/no]
[Y/N]
Yes (Pilot
project)?
?
Yes (Pilot
projects)
Forthcoming
N
planned
Richtlinien für die
Anlage von
Landstraßen RAL
(Draft)
Yes
Yes
Richtlijn Essentiële
Herkennbaarheitkenmerken van
weginfrastructuur
Veje og stier i åbent
land Hæfte 0
Planlægning af veje
i det åbne land
Norway
Poland
Portugal
Slovenia
Sweden
Switzerland
Spain
UK
3.
Common Conclusion of the CEDR TG “Road Safety” on SER
The concept of self-explaining roads can be seen as a further step to reduce the number of
accidents on rural road networks. Existing concepts should be monitored and evaluated to
facilitate a further application of self-explaining roads in Europe.
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APPENDIX 1 - Comments from CEDR Countries
Self explaining roads, French experience (2009-02-17)
The process in France consists in acting on infrastructure and it's surroundings so as to naturally incite
the users to have a safe driving behaviour and reduce their speed. From the acknowledgement that
the road and its surroundings influence, in an automatic way, the behaviour and so the speed of
drivers, the point is to understand these automatisms so as to see whether it is possible to construct or
make-up roads which should naturally incite to drive less fast.
Moreover, important gains of security have been obtained largely by enforcing controls. These have
made the behaviours evolve, and the point is to make this evolution sustainable by the means of a
better understanding of the infrastructure on the user part.
The project process follows nowadays several tracks :

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Collecting experiences on the national network as well as on the network under command of
local authorities, analysis of determinative factors
Studying more thoroughly the user behaviours facing the infrastructure
Implementing road legibility processes (guide book and technical notes do exist)
Studying and testing devices as 2 x 1 lane with overtaking lengths, mini-roundabouts in
interurban zone
Testing in full scale on a road project
In 2006 a seminar has gathered the French community on the subject and has too made it
possible to present experiences from Netherlands and Switzerland.
Which network is concerned : the State sets the process in motion associating the local authorities so
as every contracting authority can adhere. The local authorities have on their side adopted initiatives
in this direction.
Reference documents
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Experience collection for landscape and legibility, landscape and road safety (2003)
Road legibility and driver behaviour, Study on arrangements realized on RN 23 ( 2008)
Legibility memento, Contribution to an understanding of driving by the means of a territorial
approach ( 2006)
Landscape and road legibility : Food for thought about a process associating road safety and
landscape (2006)
Proceedings of 2006 seminar about the pacified road
Testing leaflets about 2 x 1 lane and mini- roundabouts : in progress
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