MassDOT Planning routinely conducts a various air quality planning and analysis to meet the transportation “conformity” requirements of the federal Clean Air Act (CAA) of 1990. Transportation conformity is a process which establishes the framework for improving air quality to protect public health and the environment. The goal of transportation conformity is to ensure that FHWA and FTA funding and approvals are given to highway and transit activities that are consistent with air quality goals.
The CAA requires that regional transportation plans, transportation improvement programs, and federal projects conform to the purpose of the State Implementation Plan (SIP).
Conformity to a SIP means that such activities will not cause or contribute to any new violations of the National Ambient Air Quality Standards (NAAQS), increase the frequency or severity of NAAQS violations, or delay timely attainment of the NAAQS or any required interim milestone.
Through the use of travel demand models, vehicle emission rates, and the latest planning assumptions for future transportation projects, MassDOT Planning estimates statewide and regional vehicle emissions for certain pollutants to determine whether they fall within the on-road mobile source emission limits (budgets) established by the SIP. Planning staff works closely with federal, state, and regional agencies to consult on data, modeling, and other issues related to conformity determinations.
For more information, visit the FHWA Conformity