Transportation Conformity in Multi-jurisdictional (Complex) Nonattainment and Maintenance Areas

The boundaries of a metropolitan planning organization (MPO) do not always correspond to the nonattainment or maintenance area boundary, nor does a nonattainment or maintenance area always contain a single MPO. In addition, a nonattainment or maintenance area boundary may encompass portions of more than one State. Also, there may be some portion of the nonattainment or maintenance area that is not included in any MPO's planning area.

EPA has released guidance to address Conformity Implementation in Multi-jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards. A PDF copy of this guidance can be downloaded from the EPA website.

NOTE:On October 20, 2006, the DC Circuit U.S. Court of Appeals vacated 40 CFR 93.109(e)(2)(v). 8-hour ozone areas that do not have adequate or approved 8-hour budgets can no longer utilize this provision to use the interim emissions tests instead of their 1-hour budgets to demonstrate conformity. Please see: (Circuit Court Ruling)

Transportation Conformity Practices in Complex Areas. In addition, FHWA has completed a study of current transportation conformity practices in these types of areas. This study documents how conformity determinations and regional emissions analyses are being done in multi-State nonattainment/maintenance areas, multi-MPO nonattainment/maintenance areas, nonattainment/maintenance areas with "donut" areas, and MPOs with multiple nonattainment/maintenance areas for the same pollutant.