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Transportation Conformity

What is Transportation Conformity?

Transportation conformity ("conformity") is a way to ensure that Federal funding and approval goes to those transportation activities that are consistent with air quality goals. Conformity applies to transportation plans, transportation improvement programs (TIPs), and projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration (FTA) in areas that do not meet or previously have not met air quality standards for ozone, carbon monoxide, particulate matter, or nitrogen dioxide. These areas are known as "nonattainment areas" or "maintenance areas," respectively.

Relationship to Air Quality and SIPs

The Clean Air Act (CAA) requires that, in areas experiencing air quality problems, transportation planning must be consistent with air quality goals. This is determined through the transportation conformity process. In some areas, this process has forced State and local transportation officials to make tough decisions in order to meet both air quality and mobility goals. Where CAA goals were not being met, some State and local transportation officials have been challenged to find ways to reduce vehicle emissions by developing transportation plans, TIPs, and projects that will alter travel patterns, reduce the number of single-occupant vehicles, and make alternative modes of transportation (such as transit and bicycles) an increasingly important part of the transportation network.

Air Quality and Sustainability Highlights

Air Quality and Sustainability Highlights is a bi-monthly publication produced by FHWA. The purpose of this bi-monthly update is to keep conformity stakeholders up to date on issues related to transportation conformity, including upcoming training opportunities.


Answers to some of the frequently asked questions (FAQs) about transportation conformity are provided below.

Updated: 9/7/2021
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