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Transportation Conformity

Information about transportation conformity in Texas, including applicable state implementation plan (SIP) and rule revisions, and information for areas with transportation conformity requirements

The SIP files on this page are hosted by the Texas Records and Information Locator (TRAIL) web archive . If you need assistance with a file, please contact siprules@tceq.texas.gov

Background

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 (NAAQS) (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 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 finalized approval effective December 12, 2014.

Latest state rule revision:

2007 EPA approval effective December 12, 2014: ( 79 FR 67068 )

Previous state SIP and rule revisions:

2005 EPA approval effective September 6, 2005 ( 70 FR 38776 )

2003 EPA approval effective September 6, 2005: ( 70 FR 38776 )

1998 EPA approval effective September 7, 1999 ( 64 FR 36790 )

1994 EPA approval effective January 8, 1996 ( 60 FR 56244 )

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 Dallas-Fort Worth and Houston-Galveston-Brazoria Serious Classification Reasonable Further Progress (RFP) State Implementation Plan (SIP) Revision for the 2008 Eight-Hour Ozone National Ambient Air Quality Standard and found adequate by the EPA for transportation conformity purposes effective May 24, 2023 ( 88 FR 24693 ).

El Paso Coarse PM (PM10) Nonattainment Area, CO Maintenance Area, and El Paso County Ozone Nonattainment Area (Part of the El Paso-Las Cruces Texas-New Mexico Nonattainment 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 maintenance area is under a limited maintenance plan and is no longer required to perform a regional emissions analysis for CO to demonstrate conformity to that standard. The El Paso Limited Maintenance Plan for the Eight-Hour Primary Carbon Monoxide National Ambient Air Quality Standard was approved by the EPA effective October 10, 2017 ( 82 FR 42454 ). 

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 portion of the  Dallas-Fort Worth and Houston-Galveston-Brazoria Reasonable Further Progress State Implementation Plan Revision to Meet the 2008 Eight-Hour Ozone National Ambient Air Quality Standard (Project No. 2016-017-SIP-NR) and found adequate by the EPA for transportation conformity purposes effective June 9, 2021 ( 86 FR 24717 ).

Bexar County Eight-Hour Ozone Nonattainment Area

The Bexar County eight-hour ozone nonattainment area is required to demonstrate transportation conformity for ozone precursors, VOC and NOX. There are no SIP MVEBs for the area, so transportation conformity must be demonstrated using the interim tests provided in 40 CFR §93.119 .

Beaumont-Port Arthur (BPA) Eight-Hour Ozone Maintenance Area

The BPA eight-hour ozone maintenance area is required to demonstrate transportation conformity in a limited capacity under the revoked 1997 eight-hour ozone standard. Similar to an area under an approved limited maintenance plan, the BPA maintenance area is not required to perform a regional emissions analysis for VOC or NOX to demonstrate conformity.

Contact Us

Jamie Zech
Air Quality Division, TCEQ
Phone: 512-239-3935
Email: jamie.zech@tceq.texas.gov