Factors influencing drivers' speed behaviour and adaptation : Summary report on research area 2

This report summarises the findings of Research Area 2 within the European project MASTER (MAnaging Speeds of Traffic on European Roads) and addresses the question "what are the key factors influencing drivers' choice of speed?" It deals with present speeds and speed management methods, speed enforcement, motivation and acceptability of driving speeds, road design and speed behaviour, and cognitive rfication processes and driving speed. Results are based upon literature reviews, survey studies, behavioural studies in a driving simulator, and laboratory experiments.
Speed limits in built-up areas are harmonised for most European countries, but on rural roads and motorways speed limits vary largely among countries. The results strongly support the need for harmonising speed limits at a European level. Police enforcement measures may be adequate but are expensive and difficult to maintain. Automatic speed enforcement seems to have some potential to reach a higher compliance level, but in some countries legislative changes are needed for that. An interview survey on road users' attitudes to driving speeds and speed limits and the acceptability of speeds and speed limits to the road users clearly showed that traffic safety implications are aspects that all road users consider as important. Selling traffic safety measures including speed management measures according to general marketing models is promising. For communicating with the public one should focus on the advantages of lower speeds and what people can contribute themselves (by making them more aware of consequences of their behaviour) to increase life quality for residents and vulnerable road users.
Road design and the manner the road is perceived by the road user contribute considerably to drivers' speed choice. Speed-reducing measures have a larger moderating effect when they affect the driving task more directly. Combined measures, especially when the image of the entire road section is changed, have the largest effects. To meet drivers' expectancy consistently, a limited set of road categories with each maximally distinguishable from each other by the road users is needed, with appropriate speed levels dependent on the function of the road and its design. A more system-atic application of road design elements results in a subjective road categorisation that is more in correspondence with the officiahe official road classification and in a reduced variation in driving speeds within a given road category. Cognitive learning experiments show that the classification process of both artificial and road environments is based on similar principles of human classification with prototypical representations and schemata. People are able to learn categorising on the basis of one or two stimulus dimensions, but cannot correctly learn to use information from three dimensions together. Implications for road design are that providing redundant information does not help, since individual road users only use a few of the available characteristics for individual road classification. Only specific dimensions such as lane width and the presence of bicycle lanes seem to affect drivers' speed choice directly.