Transportation conformity is a requirement of the federal Clean Air Act (CAA) to ensure that air quality in nonattainment and maintenance areas for transportation-related National Ambient Air Quality Standards (ozone, particulate matter (PM), carbon monoxide (CO), and nitrogen dioxide (NO2)) is not negatively impacted by federal funding and approval of transportation activities. Nonattainment areas are those that do not currently meet an air quality standard, and maintenance areas are those that were previously nonattainment for an air quality standard. Transportation conformity applies to transportation plans, transportation improvement programs, and projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration (FTA).
Transportation conformity requires an affected area to conduct an analysis to estimate emissions for the pollutant(s) under which the area is nonattainment or maintenance that are expected to result from the area’s transportation system. The analysis must demonstrate that those estimated emissions do not exceed the emissions limit established in the state’s air quality SIP. The emissions limit is referred to as the motor vehicle emissions budget (MVEB).
Conformity determinations also ensure that transportation and air quality agencies are in consultation with one another, and that transportation control measures in an approved state air quality SIP are being timely implemented. Consultation partners include the affected metropolitan planning organization (MPO) and local transit and air quality offices, the Texas Department of Transportation, the Texas Commission on Environmental Quality, the United States Environmental Protection Agency (EPA), FTA, and FHWA.
Transportation Conformity Links
- State Transportation Conformity Rule, 30 Texas Administrative Code (TAC) Chapter 114.260
- EPA’s Transportation Conformity Webpage
- FHWA’s Transportation Conformity Webpage
State SIP and Rule Revisions
The Texas transportation conformity rule describes the state's interagency consultation procedures and incorporates by reference the federal transportation conformity rule. Transportation conformity was incorporated into the state SIP in 1994 as required under the CAA Amendments of 1990, §176(c). Since 1994, the state SIP and transportation conformity rule have been revised to incorporate amendments to the federal transportation conformity rule. The most recent revision was adopted by the Commission on June 27, 2007, and the EPA proposed approval on May 13, 2014.
Latest state rule revision:
2007 (EPA approval pending)
- Revisions to 30 TAC Chapter 114, Control of Air Pollution from Motor Vehicles (Rule Project No. 2006-046-114-EN)
Previous state SIP and rule revisions:
2005 EPA approval effective September 6, 2005 (70 FR 38776)
- Revisions to 30 TAC Chapter 114, Control of Air Pollution from Motor Vehicles (Rule Project No. 2005-002-114-AI)
- Transportation Conformity SIP for Texas Nonattainment and Maintenance Areas (SIP Project No. 2005-002-114-NR)
2003 EPA approval effective September 6, 2005: (70 FR 38776)
- Revisions to 30 TAC Chapter 114, Control of Air Pollution from Motor Vehicles (Rule Project No. 2003-008-114-AI)
- Transportation Conformity SIP for Texas Nonattainment and Maintenance Areas (Project No. 2003-008-114-AI)
1998 EPA approval effective September 7, 1999 (64 FR 36790)
- Revisions to 30 TAC Chapter 114, Control of Air Pollution from Motor Vehicles (Rule Project No. 98003-114-AI)
- Transportation Conformity SIP for Texas Nonattainment and Maintenance Areas (Project No. 98003-114-AI)
1994 EPA approval effective January 8, 1996 (60 FR 56244)
- Transportation Conformity SIP for Dallas-Fort Worth, El Paso, Beaumont-Port Arthur, , Houston-Galveston, and Victoria Nonattainment and Maintenance Areas
Areas with Conformity Requirements
Dallas-Fort Worth (DFW) Eight-Hour Ozone Nonattainment Area
The DFW eight-hour ozone nonattainment area is required to demonstrate transportation conformity for ozone precursors, volatile organic compounds (VOC) and nitrogen oxides (NOX). The VOC and NOX MVEBs to which the area must currently conform were established in the DFW 1997 Eight-Hour Ozone Standard Reasonable Further Progress SIP Revision (Project No. 2010-023-SIP-NR) and found adequate by the EPA for transportation conformity purposes effective February 19, 2013 (78 FR 7429).
El Paso Coarse PM (PM10) Nonattainment Area and CO Maintenance Area
The city of El Paso is nonattainment for PM10, and a portion of the city is maintenance for CO; therefore, transportation conformity must be demonstrated for both pollutants. The PM10 MVEB to which the area must currently conform was established in the 1991 PM10 SIP for Moderate Area – El Paso, which was approved by the EPA effective February 17, 1994 (59 FR 02532). The CO MVEB to which the area must currently conform was established in the El Paso Revised Maintenance Plan for CO (Project No. 2007-014-SIP-NR) and approved by the EPA for transportation conformity purposes effective October 3, 2008 (73 FR 45162).
Houston-Galveston-Brazoria (HGB) Eight-Hour Ozone Nonattainment Area
The HGB eight-hour ozone nonattainment area is required to demonstrate transportation conformity for ozone precursors, VOC and NOX. The VOC and NOX MVEBs to which the area must currently conform were established in the HGB 1997 Eight-Hour Ozone Standard Nonattainment Area MVEB Update SIP Revision (Project No. 2012-002-SIP-NR) and approved by the EPA effective February 3, 2014 (79 FR 57 and 79 FR 51).
Air Quality Division, TCEQ
For information concerning general conformity in Texas, please visit TCEQ’s Understanding General Conformity in Texas webpage.