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The Congestion Mitigation and Air Quality Improvement Program

CMAQ and Transportation Conformity

Note: This information was archived in September 2013. For current information, see

In order to fund the best projects, transportation and air quality planning must be fully integrated. Without a comprehensive picture of an urban, nonattainment area's transportation and air quality needs, including detailed understanding of the interrelationship between congestion, travel growth, and transportation-related emissions, it will be extremely difficult to maximize the effectiveness of an area's CMAQ funding. At the nexus of transportation and air quality planning is transportation conformity. And CMAQ funding has, in many instances, been critical to making a conformity determination and maintaining the flow of Federal transportation funds without disruption.

Transportation planning in metropolitan communities strives to maximize mobility and accessibility while simultaneously minimizing air pollution. The MPOs are composed of representatives from regional transportation organizations and local governments. Planning activities are initiated by MPOs and in order to achieve transportation goals, follow a formal "continuing, comprehensive and cooperative" planning process. The process begins with public participation and input that reflects the values and priorities of the community.

Conformity is a requirement of the CAA which states that transportation plans, programs and projects must "conform" to a state's plans to attain the air quality standards. A demonstration of conformity is required to receive federal funds and approvals before advancing projects. If the demonstration cannot be made, only certain projects may proceed until it can be.

Conformity brings together transportation and air quality planning. The MPO creates a 20 year transportation plan and the Transportation Improvement Program (TIP) which is a prioritized list of transportation activities in the MPO area. For an MPO in a nonattainment (or maintenance) area, the predicted air emissions from the plan and TIP must not exceed an emissions limit established by the State air quality agency. These documents embody the MPO's vision for addressing the area's transportation needs in consultation with the State DOT. By contrast, each State air quality agency is responsible for developing a plan to achieve the national air quality standards. The State Implementation Plan, referred to as the SIP, describes emission reduction efforts to attain the NAAQS and is subject to EPA approval. Without adequate planning to address both the transportation needs and for attainment of the standards, the conformity process can become unbalanced, making the demonstration of conformity problematic.

The CMAQ program, which has sometimes been referred to as the funding arm of the Clean Air Act, has a direct and important relationship with conformity and air quality compliance. It can be an important funding strategy for implementing such measures as CAA-required inspection and maintenance programs or conversions to alternative fuels. One of its greatest benefits has been toward assisting the demonstration of conformity.

When preliminary analysis indicates that conformity cannot be established, it may mean that the MPO and the State DOT must change the timing or mix of transportation projects in the Plan/TIP, delaying or eliminating needed transportation improvements. An alternative to this is to identify emissions-reducing projects as offsets which may be funded under the CMAQ program. In this way, CMAQ funding has been crucial to avoiding costly disruptions in the Federal funding process.


Updated: 9/23/2013
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