This paper describes a study by the Transport Research Laboratory (TRL), which aims to increase knowledge about speed distributions and provide a better understanding of the speed-accident relationship for urban roads in the UK. In 1992, TRL commissioned Wootton Jeffreys Consultants to collect data on speeds and speed distributions on urban roads in 100 randomly selected locations, 94 of which were in 30 mph speed zones and six in 40 mph zones. Speed data were collected separately in each of two directions, and analysed statistically, using non-hierarchical cluster analysis and linear discrimant analysis. As a result, the links were classified into: (1) highly congested town roads; (2) typical inner city link roads; (3) suburban link roads; and (4) country (fast) link roads. The mean link speeds of these classes were 20.7 mph, 24.5 mph, 28.7 mph and 33.1 mph, respectively. A well-fitting statistical model was developed, that provided some remarkable insights into the relationship between speed and accidents. Further research is needed, to understand this relationship well enough to develop practical strategies for accident reduction.
Samenvatting