Enforcement Of Vehicle Emissions Standards By Local Authorities To Help Improve Local Air Quality PDF Download

GAO was requested to examine the operation of the Environmental Protection Agency's (EPA) automotive emission control standards. EPA estimates that about 80 percent of the 100 million registered motor vehicles exceed Federal emission standards. About half the cars pass beyond acceptable emission limits within a year of manufacture, with the rate steadily increasing thereafter. Poor owner maintenance and infrequent inspections account for most of this figure. According to EPA, these failures are due to maladjusted engine settings, premature parts failure, use of leaded fuels, improper car use, tampering with emission control systems, and poor design or production practices. Mandatory annual inspection and maintenance programs can identify and correct many of these problems, but a short test is needed to check compliance. EPA claims to have such a test available, but manufacturers question its applicability. The Clean Air Act requires inspection and maintenance programs in areas where car emissions contribute significantly to air pollution; EPA has identified 110 of these areas, but only 6 currently have such programs. Other enforcement efforts are also below par, including assessment of emissions performance at all stages of vehicle life: design, production, and use. The EPA prototype certification program overlooks the deterioration of engine system components, among other factors.