A MACROSCOPIC RELATION BETWEEN STOCK OF TRAFFIC CONTROL DEVICES AND NUMBER OF TRAFFIC ACCIDENTS . PROCEEDINGS INTERNATIONAL CONFERENCE ON NEW WAYS AND MEANS FOR IMPROVED SAFETY, TEL AVIV, ISRAEL, FEBRUARY 20-23, 1989

From 1970 until 1979, the number of traffic accidents decreased dramatically in Japan. The number of fatalities was almost halved in these years. Since then, however, the number has gradually been increasing. Many studies were carried out to explain the change in the accident number from various points of view. The author focuses on engineering methods of accident prevention in this paper. Traffic control devices such as traffic signal, traffic signs or road markings are particularly good for reducing traffic accidents. In Japan, a large amount of money has been spent on such devices since 1970, but any device loses its initial efficiency as time elapses. Therefore, deterioration should be taken into account in the analysis of the effectiveness of traffic control devices for traffic accident prevention. In this analysis, deterioration is interpreted as depreciation of the stock value of each device. By such a consideration, a time series change in the stock of traffic control devices is estimated, using the annual budgets from 1971 to 1985. It is found that this change corresponds well with the change in the number of traffic accidents per trip kilometers. The model is applicable for the estimation of traffic accident numbers for the future, and will be useful for making traffic accident prevention policy. (TRRL)