Evaluation of Factors Affecting Vehicle Emission Compliance Using Regional Inspection and Maintenance Program Data

In-use vehicle regional inspection and maintenance (I/M) programs in the United States (US) and Canada generate a tremendous volume of data that provides a means for evaluating vehicle emissions compliance in actual consumer use. In this study, IM240 test data for several 1996 to 2001 vehicle models are analyzed from different regional programs in the US and Canada to confirm the suitability of using these data for evaluation of vehicles equipped with advanced emission control technology and to examine the various potential factors responsible for emissions noncompliance. Relative comparisons between US and Canadian program data are made for vehicle models used in the Alliance of Automobile Manufacturers (AAM) MMT® Test Program to examine the potential impact of differences in fuel properties on consumer experience and vehicle compliance. The compliance rate during IM240 testing is additionally examined for a number of 2000 and 2001 models that were certified by EPA with emissions levels equal to or less than Tier 2 Bin 5 standards. The totality of these analyses demonstrate the continued compatibility of the gasoline additive MMT® in consumer or in-use vehicles equipped with advanced emission control technologies.