Road-accident data: interpreting the British experience with particular reference to the risk homoeostasis theory

Wilde (1984) recently defended the risk homoeostasis theory, which predicts that conventional (non-motivational) safety measures will fail to reduce the accident rate per unit time of exposure in an activity. Support for RHT was claimed from an analysis of U.S. road accident data. However, there were problems with Wilde's analysis, which are outlined. British road-accident data, comparable with the U.S. data used by Wilde, are analysed, showing a substantial post-war reduction in mortality rate per vehicle distance. Various possible explanations for the results are described. Little support is found for risk homoeostasis theory.