The air quality provisions of the Clean Air Act (CAA) and the metropolitan transportation planning provisions of Title 23 and Title 49 of the United States Code3 require a planning process that integrates air quality and metropolitan transportation planning such that transportation investments support clean air goals. This process is known as transportation conformity and is carried out in accordance with 40 CFR Parts 51 and 934. Exhibit 1 illustrates how conformity plays a central role as the link between transportation and air quality planning.
Exhibit 1: Conformity Links Air Quality and Transportation Planning
3Title 23 and Title 49 of the United States Code (U.S.C.) codify the transportation laws including the Fixing America's Surface Transportation Act (FAST Act). These include transportation planning provisions that govern the programs of the FHWA and the FTA.
4The transportation conformity rule is available at www.fhwa.dot.gov/environment/air_quality/conformity/laws_and_regs/.