Abstract
Research on the incompatibility of vehicle types on the roads has thus far focused on the fatality risks associated with the occupants in each type of vehicle involved in a crash, and the fatal crash involvement rates of different types of vehicles, with little attention directed at the marginal effects of changes in the vehicle mix on road safety. This paper found that increasing the number of cars and buses in the vehicle population would reduce the number of fatal crashes, whereas increasing the number of motorcycles, trucks, sport utility vehicles, and vans will increase the frequency of fatal crashes. (Author/publisher).