A comparison of the Michigan checklane and periodic motor vehicle inspections

Abstract

A two-year study evaluated the Michigan checklane motor vehicle inspection system as a trial substitute for a periodic motor vehicle inspection program. Two counties served as test areas. One county had a checklane inspection of 15% of its cars per year; the other county had a simulated periodic motor vehicle inspection. Random checklanes were used in 1975 and 1976 to estimate the condition of the cars in each county, with minimum sample sizes of 2000 cars in each group. The rates of mechanical outages were found to depend strongly on the age of the cars. Cars involved in the simulated PMVI had to have the same owner over a two year period and proved to be a self-selected group. The PMVI vehicles were in somewhat better mechanical condition than the general population even before being subject to the PMVI. After adjusting for this and the age of the vehicle, no significant differences were found in the rates of vehicles passing the inspection, even though the design had a power of at least 90% of detecting a difference of 0.05 in the rate of passing the inspection. Estimates of repair for several components were also developed and are presented.