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Transportation Conformity

Transportation conformity is required by the Clean Air Act (CAA) Section 176(c) which ensures that Federal (FHWA/FTA) funding and approval are given to transportation (highway/transit) activities that are consistent with air quality goals. It is a link between Transportation and Air Quality planning ensuring that transportation improvement programs (TIPs) and Federal projects must conform to the purpose of the SIP.

  • Cause or contribute to any new violations of the national ambient air quality standards (NAAQS)
  • Increase the frequency of severity of NAAQS violations
  • Delay timely attainment of the NAAQS or any required interim milestone

Transportation conformity only addresses air pollution from on-road mobile sources such as cars, trucks and transit in areas that are designated as nonattainment or maintenance for the following pollutants and their appropriate precursors:

  • Ozone (O3);
  • Particulate matter (PM10 and PM2.5);
  • Nitrogen dioxide (NO2); and
  • Carbon monoxide (CO)

Transportation activities subject to transportation conformity are:

  • Metropolitan transportation plans
  • Metropolitan transportation improvement programs (TIPs)
  • Federal projects receiving FHWA/FTA funding or approvals

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