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Guidance on the Congestion Mitigation and Air Quality Improvement (CMAQ) Program Under the Flexible, Efficient Transportation Equity Act: A Legacy for Users

[Note: This document has been incorporated into and/or superseded by the Final Guidance for the CMAQ Program which was published in the Federal Register on October 20, 2008 and became effective on November 17, 2008. This Final Guidance can be accessed at: HTML version: PDF version: (394KB). - ed.]

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DOT Trisk Symbol
U.S. Department of Transportation
Federal Highway Administration
Subject: INFORMATION: Guidance on the Congestion Mitigation and Air Quality Improvement (CMAQ) Program Under the Flexible, Efficient Transportation Equity Act: A Legacy for Users Date: October 31, 2006
From: April Marchese, Director
Office of Natural and Human Environment
Reply to: HEPN-10
To: FHWA Division Administrators
Resource Center Directors
Federal Lands Highway Division Engineers

The purpose of this memo is to transmit new guidance for the CMAQ program as reauthorized under SAFETEA-LU. This document, which replaces the April 1999 guidance, discusses the changes to the CMAQ program as a result of SAFETEA-LU and clarifications of our policy based on 7 years of feedback since the last guidance document.

The SAFETEA-LU placed a renewed focus on advancing cost-effective transportation projects that improve air quality. Specifically, the bill highlighted diesel engine retrofits as a priority for CMAQ expenditures, due to the cost-effective emissions reduction benefits that can be achieved through many retrofit technologies. The FHWA encourages States to consider this legislative priority when selecting projects for CMAQ funding. Appendix 4 of this guidance document provides relative cost-effectiveness data on various eligible project types to help inform decision-makers with the CMAQ project selection process. Further information on diesel retrofits is included in Appendix 5.

The SAFETEA-LU also establishes priority funding consideration for cost-effective congestion mitigation activities that improve air quality. In May 2006, the Secretary announced a new department-wide initiative to tackle the growing problem of congestion on our Nation's transportation system. The goals of the CMAQ program support this initiative in three main ways: promoting operational and technological improvements, targeting major freight bottlenecks, and relieving urban congestion. The CMAQ program is one of the key tools the department will employ in the coming years to help relieve congestion -- a goal that will save time and money while helping to improve the air.

This updated interim guidance includes comprehensive discussions and direction on a host of new or highlighted areas under SAFETEA-LU. As we develop knowledge and experience with these new areas, such as diesel retrofits, we will augment this formal program guidance with intervening policy memoranda as appropriate. We have updated earlier volumes of our formal guidance in this manner, e.g. the 2003 memorandum on transit station expansions. In addition, since this is interim guidance, we will publish the full volume for comment in the Federal Register and issue final guidance thereafter.

Copies of this guidance (PDF - 291 KB or HTML) will be available online at the FHWA web site at: The FHWA has created a series of brochures on the CMAQ program that are also available to those interested in further information on the program. For copies of those brochures or for further information on the CMAQ program, please contact Michael Koontz at or (202) 366-2076.

The above document is in Adobe Portable Document Format, (PDF). Download Adobe Reader here.

Updated: 8/29/2017
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