The Regional Transportation Plan (RTP)  must conform to air quality improvement goals and like financial constraint, air quality conformity is a federal requirement. Federal law requires that the Regional Transportation Plan and the Regional Transportation Improvement Program (RTIP) are updated at least every four (4) years.  Birmingham MPO staff tests the draft RTP and RTIP to ensure that the projects in the plan, when considered collectively, meet specific requirements for each air quality plan (called a State Implementation Plan, or SIP) promulgated under the Clean Air Act Amendments of 1990. The analysis is documented within an Air Quality Conformity Report which is a technical appendix to the RTP.  The Air Quality Conformity Report includes documentation of elements such as travel demand forecasting, emissions calculation procedures and impacts of transportation emission reduction measures. The analysis demonstrates that mobile source emissions, estimated for the TIP and for each analysis year of the regional transportation plan, adhere to all carbon monoxide, ozone season volatile organic compound and nitrogen oxide emissions budgets established by the Alabama Department of Environmental Management (ADEM) and approved by the EPA.  Tests are also done to ensure that emissions of fine particles (PM2.5) pollutants (direct PM2.5 and precursor nitrogen oxide) are not greater than base year 2002 emissions.

Once the Birmingham MPO finds that the RTP meets regional air quality requirements, federal agencies certify that the plan is “in conformity.” In other words, the Birmingham MPO ensures that the RTP “conforms” to air quality improvement goals. If the RTP encounters difficulty in meeting conformity—or expects to—it may choose to adopt Transportation Emission Reduction Measures (TERMs), such as ridesharing and telecommuting programs, improved transit and bicycling facilities, clean fuel vehicle programs or other possible actions.

Transportation is integral to air quality planning. The regional air quality plan includes a ceiling (“an emissions budget”) for emissions from mobile sources (cars, trucks and buses), as well as emissions reduction requirements for other sources of air pollution, such as power plants. The Birmingham MPO must show that its transportation plans will conform to the mobile source emissions ceilings for specific milestone years established in the regional air quality plan and transportation plans.