Emission Standards Development for an Inspection/Maintenance Program

This paper presents the results of vehicle exhaust measurements that were used to establish emission standards for an inspection/maintenance (I/M) program. For this purpose, a total number of 100 private autos distributed across model years ranging between 1972 and 2002 were tested under idling conditions. The monitored indicators included air to fuel ratio (%), CO (%), CO2 (%), HC (parts per million, ppm), NOx (ppm), and O2 (%). Private autos with model years greater than 1994 were found to be compliant with international standards and are relatively well maintained. Emissions from older models increased significantly with a lack of engine maintenance. The paper concludes with criteria for proposing I/M emission standards based on exhaust measurements taking country-specific socioeconomic characteristics into consideration.