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State and Local Transportation Resources

Policy and Technical Guidance


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This page contains policy guidance issued by EPA and/or the U.S. Department of Transportation to assist state and local transportation and air quality agencies implement the transportation conformity program. Policy guidance can be found on the following topics:

Transportation Planning and Conformity Requirements

  • Baseline Year for the Baseline Year Test (in 40 CFR 93.119)
    This page provides a table showing the baseline year to be used for each NAAQS and the regulatory provision where it is found.

  • Transportation Conformity Guidance for 2008 Ozone NAAQS Nonattainment Areas (PDF) (24pp, 180K, EPA-420-B-12-045, July 2012)
    This document provides guidance for meeting transportation conformity requirements in areas designated nonattainment for the 2008 ozone national ambient air quality standards (“2008 ozone NAAQS”). Note:  On December 23, 2014, the DC Circuit Court vacated EPA’s revocation of the 1997 ozone NAAQS for transportation conformity purposes only in NRDC v. EPA (12/23/2014).  On March 6, 2015 EPA published a final rule revoking the 1997 ozone NAAQS for all purposes.  (80 FR 12264) The final rule will be effective on April 6, 2015.

  • Guidance for Transportation Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas (PDF) (54 pp, 589K, EPA-420-B-12-046, July 2012)
    This guidance describes how transportation conformity determinations are done in areas where multiple metropolitan planning organizations (MPOs), states and/or other agencies have jurisdiction in a nonattainment or maintenance area. This guidance updates and supersedes the July 2004 “Companion Guidance for the July 1, 2004 Final Transportation Conformity Rule: Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards”. This guidance has been updated to apply to existing and future NAAQS, consistent with the Transportation Conformity Rule Restructuring Amendments.
    Contact:  Laura Berry at berry.laura@epa.gov

  • Updated guidance on substituting and adding transportation control measures to approved state air quality plans(PDF) (35 pp, 401K, EPA420-B-09-002, January 2009 )
    This document provides updated guidance to state and local air quality and transportation agencies on implementing the Clean Air Act provision that establishes a streamlined process for substituting or adding transportation control measures to an approved state air quality plan. Transportation control measures, such as public transit and carpooling, can provide alternatives to the public that reduce motor vehicle emissions. This document supersedes the section of the February 14, 2006 interim guidance on implementing the Clean Air Act amendments made by SAFETEA-LU that addressed this provision.
    Contact: Rudy Kapichak at kapichak.rudolph@epa.gov

  • EPA and DOT Joint Guidance for the Use of Latest Planning Assumptions in Transportation Conformity Determinations  (23 pp, 343K, EPA420-B-08-901, December 2008)
    This guidance document supersedes the January 18, 2001 guidance memorandum to address the July 1, 2004 transportation conformity final rule revisions on the use of latest planning assumptions in transportation conformity determinations.
    Contact: Meg Patulski or patulski.meg@epa.gov

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Project-Level Conformity

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Emission Models and Conformity

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