Road accident external effects: an empirical assessment

The relationship between the number of road accidents and the volume of traffic is econometrically estimated in this paper. A stratified random sample of 399 road segments covering urban and rural roads in New York State(USA) in 1985 is analysed. No significant externality is detected. On ver high volume urban roads the marginal to average accident rate ratio is 1.06. On all other roads, a ratio of 0.98 is estimated. These findings contrast sharply with those of Vickrey, who estimated a ratio of 1.5 for California freeways in 1962. The results are, however, consistent with the ‘official view’ of both the US and UK highway authorities that no significant accident externality exists.