Transportation Conformity Basic Guide & Reference Guide

Under the 1990 Clean Air Act Amendments, the U.S. Department of Transportation cannot fund, authorize, or approve Federal actions to support programs or projects which are not first found to conform to the Clean Air Act requirements. The FHWA and the FTA jointly make conformity determinations within air quality nonattainment and maintenance areas to ensure that Federal actions conform to the "purpose" of State Implementation Plans (SIPs). With DOT concurrence, the EPA issues regulations pertaining to the criteria and procedures for transportation conformity.

Transportation conformity applies to all ozone, carbon monoxide, particulate matter, and NO2 nonattainment and maintenance areas, regardless of classification. A nonattainment area is a geographic region that EPA has designated as not meeting the National Ambient Air Quality Standards (NAAQS). A maintenance area is an area that was previously designated nonattainment, but is currently attaining the NAAQS, subject to a maintenance plan.

"Transportation Conformity" (or PDF 54 KB) is a short brochure that answers some simple questions regarding transportation conformity

An Introduction to Particulate Matter for Transportation Officicals (or PDF - 296 KB) is a short brochure that answers some simple questions regarding particulate matter.

"Transportation Conformity: A Basic Guide for State and Local Officials" (or PDF - 2.5 MB) is a guide to the basic provisions of the conformity process

"Transportation Conformity Reference Guide" is a comprehensive guide to conformity regulations, guidance and policy

EPA's "Green Book" lists those areas of the country that are currently designated nonattainment or maintenance.

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