Transportation conformity is the process that is used to review the current transportation plan and program in a region to ensure they conform to the state’s air quality plan. Each state’s air quality plan, also known as the State Implementation Plan (SIP) determines how the states will meet National Ambient Air Quality Standards (NAAQS), for multiple sources of air pollution including transportation. In the SIP, there is a motor vehicle emissions budget, which is a limit on the maximum level of emissions allowable from the region’s on-road vehicles, as whole. The estimated level of emissions must stay within the budget for the region to be “in conformity.”
The Clean Air Act Amendments of 1990 set the law requiring the transportation conformity process. Transportation conformity regulations were developed by the U.S. EPA and FHWA, and are contained in Federal Regulation: Title 40, Chapter I, Part 93 - Determining Conformity of Federal Actions to State or Federal Implementation Plans.
The Baltimore Region
Metropolitan Planning Organizations (MPOs) in areas that are designated “nonattainment” or “maintenance” for NAAQS are required to perform transportation conformity. The BRTB transportation planning area encompasses the Baltimore nonattainment area for 8-hour ozone, which includes Baltimore City, and the surrounding counties. The BRTB regularly performs air quality conformity determinations for short-range transportation programs (TIPs) and long range transportation plans, along with major changes to the plan or TIP, as required by regulation.