The tests were performed to gather vehicle emissions data to evaluate deterioration effects of exhaust emissions over short periods of time. The deterioration effects were determined by measuring the exhaust emissions after inspection and maintenance, measuring the exhaust emissions after a specific time interval, and comparing the results of the two test sequences. The time intervals selected were one month, two months, and three months. To assist in determining the cause of deterioration, vehicles that exhibited significant deterioration in exhaust emissions were adjusted to manufacturers specifications, tested and then retested after one month. The intention of Test Group No. 7 was to evaluate the effects of mechanic training on emission reductions achieved by motor vehicle inspection and maintenance (I/M) programs.