On-Road Evaluation of Inspection/Maintenance Effectiveness

Publication Date


Document Type


Organizational Units

Chemistry and Biochemistry


Atmospheric chemistry, Emissions, Pollutants, Inspection and Maintenance


This study presents an evaluation of inspection and maintenance (I/M) programs in terms of their effect on motor vehicle carbon monoxide (CO) and hydrocarbon (HC) exhaust emissions as measured on-road by remote sensing technology. The results show that the performance of past I/M programs at several monitored locations has been less effective than predicted by the U.S. Environmental Protection Agency. The emissions from I/M and non-I/M vehicles measured in Tucson, AZ, and in rural Colorado show no statistically significant difference. An apparent I/M effect observed in El Paso, TX, and in Denver, CO, is smaller than predicted. Comparisons of CO emissions by vehicle age for several years at the same locations in Chicago and Denver show no evidence that the Chicago centralized I/M program was more effective than the Denver decentralized I/M program.

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Copyright held by the American Chemical Society.

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