Vehicle maintenance and exhaust emissions

Abstract

In most of the world, light duty vehicles and the engines used in heavy duty vehicles are designed to comply with legal limits for exhaust emissions. The manufacturer must demonstrate that this is the case by submitting vehicles or engines for testing. There is considerable evidence, though, that many vehicles operating on the roads would not achieve the appropriate emission standards. Perhaps the main reason for this is inadequate maintenance of the vehicles: if engine settings are not in accordance with manufacturers' specifications, it is not surprising that their performance deteriorates. Methods of addressing this problem include requirements on manufacturers to produce durable and stable components and a compulsory periodic test for vehicles in use. This paper reviews information on emissions from road vehicles in service and how they are related to the vehicle's condition and state of maintenance. The often conflicting criteria for in-service testing are discussed with reference to a number of current and potential test procedures.