The need to protect the public from the serious adverse health effects of motor vehicle emissions has been recognized as an important public health goal since the 1960s. Evidence of adverse health effects associated with vehicle emissions of carbon monoxide (CO), benzene, ozone, and lead was the primary driving force behind the enactment of the Air Quality Act of 1967, which set in motion the federal regulation of tailpipe emissions from motor vehicles. The environmental impacts of highways were also cited as a major factor behind the enactment in 1969 of the National Environmental Policy Act (NEPA). The growing pall of pollution that shrouded most large U.S. cities contributed to the groundswell for action that lead President Richard M. Nixon to call for enactment of what became the Clean Air Act (CAA) of 1970, and the leadership of the U.S. Senate Air Pollution subcommittee to add air pollutant control provisions to the 1970 Amendments to the Federal-Aid Highway Act (Highway Act). Together, these three statutes provide the framework for all federal efforts, and most state programs, to protect the public from the health effects of vehicle emissions.

Despite the enactment after NEPA of broad, regulatory statutes aimed at controlling emissions from motor vehicles and mitigating the adverse environmental effects of highways, NEPAcontinues to play an important role in decisions affecting the assessment and mitigation of impacts attributable to air pollution from vehicles and highways. One of NEPA's most important contributions may be the rule that requires agencies to fill major data gaps by obtaining new information needed to provide meaningful consideration of the comparative impacts of alternatives.