Transportation Planning : Air Quality Conformity

With the passage of the 1990 Clean Air Act Amendments (CAAA) and the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA), the requirements of transportation and air quality modeling changed to address air quality concerns. The federal standards developed by the Environmental Protection Agency (EPA), set allowable concentrations and exposure limits for various pollutants to be met by urban areas based on a sliding scale of implementation.

Today, federal regulations and procedures require Metropolitan Planning Organizations (MPO) to analyze the impact of regional transportation plans on their region's air quality and perform a conformity analysis to ensure that the plans do not degrade the region's air quality. PBS&J’s professionals have extensive experience assisting MPOs in performing regional conformity analyses and implementing procedures to estimate the impact of regional and local transportation plans on mobile source emissions.

PBS&J’s air quality experts use the EPA recommended mobile source emission factor models (Mobile5 and more recently the Mobile6 version) for planning and implementing air quality management projects. A variety of methodologies is used to estimate the impact of transportation improvements on mobile emissions including the impact of projects that are not large enough to be accounted for in a regional travel demand model. Our professionals understand the importance of and routinely participate in the public involvement process and interagency coordination needed to assure consistency between emissions and conformity analysis among different jurisdictions.