What is this?
A process required under the Clean Air Act (CAA) Section 176(c) to ensure that federally supported transportation activities are consistent with (“conform to”) the purpose of a state’s State Implementation Plan (SIP). Transportation conformity establishes the framework for improving air quality to protect public health and the environment. Conformity to the purpose of the SIP means Federal Highway Administration (FHWA) and Federal Transit Administration (FTA) funding and approvals are given to highway and transit activities that will not cause new air quality violations, worsen existing air quality violations, or delay timely attainment of the relevant air quality standard, or any interim milestone.
Conformity determinations must demonstrate consistency between emissions expected from the implementation of the long-range transportation plan and Motor Vehicle Emission Budgets (MVEBs) in the applicable SIP. To meet this criterion, conformity determinations in nonattainment areas with adequate MVEBs from an applicable SIP must perform an MVEB test. For the MVEB test, the emissions analysis must demonstrate the estimated emissions are less than the MVEBs in the applicable implementation plan.
More about current MVEBs...
On November 8, 2016, the Environmental Protection Agency (EPA) published the Adequacy Status of the Dallas-Fort Worth, Texas Attainment Demonstration 8-Hour Ozone Motor Vehicle Emission Budgets for Transportation Conformity Purposes, effective November 23, 2016. This notice of adequacy establishes the use of the 2017 MVEBs for the transportation conformity demonstration.
What happened now?
On November 21, 2018, the Federal Highway Administration (FHWA) and Federal Transit Administration (FTA) ruled that the Dallas-Fort Worth area's recently adopted Metropolitan Transportation Plan (Mobility 2045) and Transportation Improvement Program (2019-2022 TIP) complies with federal air quality regulations. This means a four-year window began during which projects, programs, and policies may move toward implementation.
For more information: https://www.nctcog.org/trans/quality/air/federal-air-quality/conformity