Laws and Regulations

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The air quality provisions of the Clean Air Act as amended (42 USC Sections 7401-7671q) establish restrictions on emission reductions from transportation sources. Regulations governing transportation conformity are found in Title 40 of the Code of Federal Regulations (40 CFR Parts 51 and 93).

Baseline Year for the Baseline Year Test (in 40 CFR 93.119): Refer to this page for a table showing the baseline year to be used for each NAAQS and the regulatory provision where it is found.
Complete Transportation Conformity Rule (HTML version) or (PDF version)
Transportation Conformity Rulemakings - Chronological listing of all amendments (and related documents) to the Transportation Conformity Rule since the original rule was implemented in 1993
23 USC Part 135 - Statewide Transportation Planning
23 USC Part 134 - Metropolitan Transportation Planning
Title 23 CFR Part 450 - Statewide and Metropolitan Transportation Planning and Programming
Title 40 CFR Part 51 - Requirements for preparation, adoption, and submittal of implementation plans.
Title 40 CFR Part 93 - Determining conformity of Federal actions to State or Federal Implementation Plans
49 USC Part 53 - Public Transportation
Clean Air Act - Section 176(c) - Section 176 (42 USC 7506) requires that transportation plans, transportation improvement programs (TIPs), and projects conform to the purpose of the state implementation plan (SIP). Conformity to the purpose of the SIP means that the transportation activities will not cause new violations of the National Ambient Air Quality Standards (NAAQS), worsen existing violations, or delay timely attainment of the NAAQS.
Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) - Section 6011 details the SAFETEA-LU changes impacting Section 176(c)(2) of the Clean Air Act.
NAAQS - Details on air quality standards for criteria pollutants, along with information related to the implementation of control programs for each pollutant
2006 PM2.5 and PM10 Standards - Details on the particulate matter (PM10 and PM2.5) standards established by EPA
2008 8-hour Ozone Standards - Details on the 8-hour ozone standards established by EPA
Nonattainment Designations under the 1997 8-Hour Ozone and PM2.5 Standards - Details on EPA's designation of nonattainment areas for the 1997 8-hour ozone and PM2.5 air quality standards
NEPA - Contains the laws, regulations, and guidance that guide NEPA implementation at FHWA.

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