Road design can have an important impact on the choice of speeds, discouraging access and inappropriate speeds. Measures and effectiveness of these measures differ according to the type of road.
In the design of single carriageway rural roads, consistency and continuity are often lacking, and there can be large speed differences between different kinds of user. A range of engineering measures can encourage a steady, safe speed and make hazards perceptible.
On the approaches to towns and villages on busy routes, transition zones from high speed to low speed roads are required. Design features can be used to produce a cumulative influence on drivers' perception of appropriate speed culminating in a gateway feature marking the start of the speed limit for the built-up area.
There are also a range of well-established techniques to manage speed on urban roads ranging from discouraging traffic from entering certain areas to installing physical speed-reducing measures. Experience in several EU Member States has shown that accident reductions of between 15 and 80 per cent can be achieved by comprehensive treatment of residential areas. Application of speed management measures in such areas throughout the EU could reduce injury accidents by 5 per cent.
It is not yet clear how to use design to reduce inappropriately high speeds on motorways and expressways without being counter-productive to safety.
Each road improvement or construction scheme should be subject to a safety audit to check that its design and implementation are consistent with safety principles. The likely effects of a scheme on choice of speed, and the consistency of its design with the speeds that drivers are intended to choose, are an important aspect of the safety audit.
Links
ETSC: Reducing traffic injuries resulting from excess and inappropriate speed (1995)
SWOV: The effect of altered road markings on speed and lateral position (2003)
SWOV: Traffic calming schemes (2003)
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