Witnesses' estimates of the speeds of traffic accidents

Abstract Using as data base the fatal pedestrian accidents occurring in London in 1970–1971, the usefulness of police reports for estimating the speeds of road traffic accidents was investigated. Two approaches were used: correlating estimates by different people of the initial speeds, and relating vehicle damage to estimated impact speed. The first approach established quite high correlations (around 0.6) between different estimates, and in the second a positive association was found between speed and damage. Furthermore, the average difference between estimates made by independent witnesses and by the drivers of the vehicles involved was small (3 m.p.h.). In addition, a table is given showing the distribution of estimated impact speeds for this sample of accidents.