The latest research at TRL, UK into how speed affects road safety is reviewed. Speeders are defined as drivers who drive above the mean speed of all drivers for a road and not just those who exceed the speed limit or drive at very high absolute speeds. Speeders are more likely to be involved in accidents and this risk rises sharply for driving at high speeds. They are more likely to be young, male, drive high mileages on business and have a tendency to violate traffic regulations. Cross-sectional and before-after road based studies are described. For each one mile per hour reduction in mean vehicle speed, accident reductions of between 2 and 9% are achievable. Targeting the problems of the fastest drivers is likely to be of most accident reduction benefit.
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