Chapter 1 - Motor Vehicle Emissions Control: Past Achievements, Future Prospects

Abstract

Motor vehicles—cars, trucks, and buses—are a major source of air pollution. This air pollution or smog formed in the atmosphere as a result of complex photochemistry between hydrocarbons— called volatile organic compounds (VOC), and the oxides of nitrogen (NOx)— results in high ambient levels of ozone and other oxidants. In addition, automobiles are the dominant source of carbon monoxide (CO) and lead. So do stationary combustion systems. Even natural (i.e., biogenic) hydrocarbon emissions are important. However, it is the changes in seasonal emissions—winter for CO and summer for VOC and NOx—that matter, and significant differences exist from one urban area to another. It also has become clear that photochemical smog with its high ozone levels is now a large-scale regional problem transported by the prevailing winds with ozone concentrations in rural areas reaching about half the urban peaks. The chapter discusses the currently available techniques to control emissions and the future efforts to reduce them. Currently remote sensing is used to quantify the extent and impact of high-emitting cars. The future efforts to reduce emissions from light-duty vehicles are focusing on three areas: improvements in fuels, stricter new car emission standards, and means for enforcing better in-use compliance.