UC Davis Institute of Transportation Studies

Under the requirement of the Clean Air Act (CAA), states are required to prepare air quality plans that outline how areas currently violating national ambient air quality standards (non-attainment areas) will achieve the standards and will avoid future significant deterioration of their air quality. On November 24, 1993, the U.S. Environmental Protection Agency (USEPA) adopted the transportation conformity rule (Rule), pursuant to Section 176(c)(4) of the CAA. The Rule requires that transportation plans, programs and projects funded or approved by the federal government of their agents under Title 23 (Highways) U.S.C. or the Federal Transit Act conform with state or Federal air quality implementation plans.