In Norway, motor vehicles are inspected both by means of random, roadside inspections and by means of periodic inspections. This paper describes an experiment which was conducted during the years 1986-1990, in order to estimate the effects of periodic inspections on automobile accident rates. A total of 205,000 cars took part in the experiment. These were randomly assigned to three groups. One group was inspected annually for three years, one group was inspected in 1986 only and one group was not inspected at all. Effects on accident rates and technical condition were measured. Toward the end of this experiment, another study was started with the purpose of developing a more effective system of vehicle inspections. effective system of vehicle inspections. A random sample of 5,000 cars were stopped in traffic and referred to the nearest inspection hall of the Department of Motor Vehicles, where their technical condition was determined by means of an ordinary inspection. Subsequent analysis uncovered the relationships between technical condition and a number of variables recorded in the motor vehicle registration file, like age of car, make a model, and sex and age of the owner. Based on the results of these analyses, a preliminary computer programme was written that will make it easier to select vehicles that are likely to have technical defects for inspection.
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