Policy & Guidance

A variety of guidance documents pertaining to transportation conformity have been issued by FHWA. These documents cover a wide range of subject areas. Note that these guidance documents are not a substitute for any laws or regulations, thus do not impose legally binding requirements on EPA, DOT, states, or the regulated community. In addition, they may not apply to a particular situation based upon the circumstances. EPA and DOT retain the discretion to adopt approaches on a case-by-case basis that may differ from this guidance, but still comply with the statutes and SIP, conformity, and planning regulations. Additional transportation conformity policy and guidance documents can be found on EPA's webpage at this link.

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Frequently Asked Questions

Transportation Conformity: A Basic Guide for State and Local Officials (February 2017) - Guide that provides the basic provisions of the conformity process.
Revocation of the 1997 Primary Annual Particulate Matter (PM2.5) National Ambient Air Quality Standard (NAAQS) and Implementation of the 2012 PM2.5 NAAQS (April 2017) - FAQs to provide information on the transportation conformity and transportation planning implications as a result of implementation of the 2012 PM2.5 NAAQS and the revocation of the 1997 primary annual PM2.5 NAAQS.
Implementing the 2008 Ozone National Ambient Air Quality Standard (NAAQS) Frequently Asked Questions (May 2013) - FAQs to address when conformity applies to the metropolitan transportation plan and TIP and at the project level; transitioning from the 1997 to 2008 8-hour ozone standard for areas nonattainment or maintenance for both; and how the planning process will be impacted by the transition to/from attainment.
Frequently Asked Questions on the Transportation Conformity Lapse Grace Period (May 2012) - FAQs to clarify the implementation of the transportation conformity lapse grace period.
Transportation and General Conformity Frequently Asked Questions (April 2011) - FAQs regarding common questions and scenarios where the transportation and general conformity regulations may intersect for certain transportation projects and clarification on how the requirements can be met.
PM2.5 Project-Level Conformity and Hot-Spot Analyses FAQs (09/19/2007) - FAQs about PM2.5 project-level conformity and hot-spot analyses.

Air Quality Planning and SIPs

Transportation Conformity Alert (August 2000) - This message alerted FHWA Division staff to several issues at the time associated with various transportation conformity requirements. It covered peak and off-peak speeds, PM qualitative analysis, latest planning assumptions, motor vehicle emissions budgets in SIPs, TCMs in SIPs, and partial implementation of TCMs.
Limited Maintenance Plans (September 2001) - Memorandum from EPA detailing instances when moderate PM10 nonattinment areas can be redesignated to attainment with a streamlined maintenance plan.

Emissions Analysis

Analyzing Exempt Projects in the Conformity Process (February 1995) - This policy memo to Regional FHWA Administrators explains whether it is permissible to estimate the emissions effects of highway or transit projects which are listed as exempt projects in the transportation conformity rule and use the results of this analysis in determining conformity of the transportation plan and TIP. It also explains whether these projects lose their exempt status if an area decides to take emissions reduction credit for them in the plan/TIP conformity analysis.
Guidance for the Use of Latest Planning Assumptions in Transportation Conformity Determinations (December 2008) - Joint USDOT and EPA guidance to clarify expectations for implementing the transportation conformity rule's latest planning assumptions requirements.

Conformity Lapse / Grace Period

Revised FTA Procedures for a Conformity Lapse (April 2003) - Memorandum from FTA clarifying project development procedures for New Starts projects in the event of a conformity lapse.
Guidance on the Implementation of the March 2, 1999 Court Decision (January 2002) - Updated guidance from FHWA and FTA concerning approval for projects in nonattainment and maintenance areas that do not have a currently conforming transportation plan and transportation improvement program. Changes resulted from a case brought against EPA by the Environmental Defense Fund.
Memorandum of Understanding between DOT and EPA on Transportation Conformity (April 2000) - MOU between DOT and EPA to provide for timely review and comment on transportation and air quality planning documents and to establish a framework for resolving outstanding issues to facilitate timely conformity decisions.

Multi-Jurisdictional (Complex) Areas

Court Decision on Transportation Conformity Rule (October 2006) - The U.S. Court of Appeals vacated a provision of the Transportation Conformity Rule (40 CFR 93.109(e)(2)(v)), a provision that allowed areas to use the interim emissions tests instead of the 1-hour budgets where the interim tests could be shown to be more appropriate for ensuring that the plan, TIP, or project would not create new violations, worsen existing violations, or delay timely attainment of the 8-hour standard, as determined through interagency consultation.

NAAQS and Designations

Transportation Conformity Alert to FHWA Divisions on PM2.5 Project-Level Conformity (November 2005) - This message alerted FHWA Division staff to transportation conformity requirement deadlines associated with the 1997 PM2.5 standard for which original designations were made on April 5, 2005. Conformity determinations for Plans/TIPs were due on April 5, 2006 and project-level conformity determinations, which may require a PM hot-spot analysis, were required after this date.

Project Level Conformity

2023 FHWA Carbon Monoxide (CO) Categorical Hot-Spot Finding (January 2023) – FHWA's 2023 carbon monoxide (CO) categorical hot-spot finding per the transportation conformity rule at 40 CFR 93.123(a)(3) for highway projects that include one or more intersections in CO maintenance areas, except in California. This finding is based on MOVES3. Project sponsors may be able to rely on the categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project-level conformity determination in CO maintenance areas.
Clarification to the "Transportation Conformity Guidance for Qualitative Hot-spot Analysis in PM2.5 and PM10 Nonattainment and Maintenance Areas" (June 2009) - This clarification to the March 2006 qualitative PM hot-spot guidance was issued by FHWA in June 2009 as part of a settlement agreement for a lawsuit challenging a project's conformity determination.
Clarification of Transportation Conformity Requirements for FHWA/FTA Projects Requiring Environmental Impact Statements (May 2003) - Memorandum from FHWA and FTA to clarify how full compliance with the CAA transportation conformity requirements is to be achieved for FHWA and FTA projects requiring an EIS under the National Environmental Policy Act, especially regarding whether conformity of a project must be determined prior to approval of the final EIS or prior to the issuance of the record of decision.
Transportation Conformity Guidance for Qualitative Hot-spot Analysis in PM2.5 and PM10 Nonattainment and Maintenance Areas (March 2006) - Memorandum from FHWA and EPA on how to perform qualitative hot-spot analyses in PM2.5 and PM10 nonattainment and maintenance areas, as required by the March 10, 2006, final transportation conformity rule.

Superseded Guidance

2017 FHWA Carbon Monoxide Categorical Hot-Spot Finding (July 2017) - FHWA's 2017 carbon monoxide (CO) categorical hot-spot finding per the transportation conformity rule at 40 CFR 93.123(a)(3) for urban highway projects that include one or more intersections in CO maintenance areas, except in California. This finding is based on MOVES2014a. Project sponsors may be able to rely on the categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project-level conformity determination in CO maintenance areas.
Guidance for Qualitative Project Level "Hot-Spot" Analysis in PM10 Nonattainment and Maintenance Areas (September 2001) - FHWA guidance (and accompanying examples) for conducting PM10 qualitative hot-spot analyses - note this guidance pertains only to those hot-spot analyses begun prior to March 29, 2006.
Interim Guidance for Implementing the Transportation Conformity Provisions in SAFETEA-LU (February 2006) - Memorandum from FHWA, FTA, and EPA concerning guidance on implementing the transportation conformity-related provisions contained in SAFETEA-LU - this interim guidance pertained to the time period before the federal transportation conformity rule was revised.
2014 FHWA Carbon Monoxide Categorical Hot-Spot Finding (February 2014) - FHWA's 2014 carbon monoxide (CO) categorical hot-spot finding per the transportation conformity rule at 40 CFR 93.123(a)(3) for urban highway projects that include one or more intersections in CO maintenance areas, except in California. Project sponsors may be able to rely on the categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project-level conformity determination in CO maintenance areas. *Note: This Finding was based on MOVES2010 which is no longer the latest emissions model for transportation conformity and SIP purposes as of October 7, 2016. Therefore, this Finding may no longer be relied upon for any CO hot-spot analyses begun after October 7, 2016

Archived Guidance

Transportation Conformity and the New Air Quality Standards - Frequently Asked Questions (June 2005) - These FAQs address questions associated with transportation conformity requirements for the 1997 8-hour ozone and 1997 PM2.5 annual standard.