Abstract
In this paper the author examines the validity of accident externality pricing in determining the optimum mix of traffic in an urban situation. He shows that the conventional justification of accident externality charges is that the motorist collective does not bear all accident costs. In a situation of mixed traffic of heavy lorries, cars, and unprotected road users, the distribution of the total accident externality charges between the different road user categories should be markedly unequal, in case different road users constitute systematically different threats to each other.