Controlling emissions from motor vehicles

US. ozone levels exceed the National Ambient Air Quality Standard (NAAQS) of 0.12 ppm in virtually every major urban area and in many nonurban areas in the East (1). Hydrocarbon emissions are a primary contrib ut01 to the photochemical reactions that produce ozone (2). These emissions from cars and light duty trucks (LDTs) account for approximately 35% of total man-made hydrocarbon emissions (I).