AN EXPERIMENTAL EVALUATION OF THE EFFECTS OF PERIODIC MOTOR-VEHICLE INSPECTION ON ACCIDENT RATES

204,000 cars were randomly assigned to three different experimental conditions. 46,000 cars were inspected annually during a period of three years: 46.000 cars were inspected once during three years; and 112,000 cars were not inspected. The number of accidents was recorded for a period of four years. No differences in accident rates were found between the groups. The technical condition of inspected vehicles improved compared to those not inspected. The experiment did not have any unintended side-effects. It is concluded that periodic motor vehicle inspection has no preventive effect on the technical condition of cars in a system where roadside inspections also exist.