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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 archiveExit the TCEQ. 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: (application/pdf79 FR 67068Exit the TCEQ)

Previous state SIP and rule revisions:

2005 EPA approval effective September 6, 2005 (application/pdf70 FR 38776Exit the TCEQ)

2003 EPA approval effective September 6, 2005: (application/pdf70 FR 38776Exit the TCEQ)

1998 EPA approval effective September 7, 1999 (application/pdf64 FR 36790Exit the TCEQ)

1994 EPA approval effective January 8, 1996 (application/pdf60 FR 56244Exit the TCEQ)

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 application/pdfDallas-Fort Worth (DFW) 2008 Eight-Hour Ozone Nonattainment Area Attainment Demonstration (AD) State Implementation Plan (SIP) Revision for the 2017 Attainment Year (Project No. 2015-014-SIP-NR)Exit the TCEQ and found adequate by the EPA for transportation conformity purposes effective November 23, 2016 (application/pdf81 FR 78591Exit the TCEQ).

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 application/pdf1991 PM10 SIP for Moderate Area – El PasoExit the TCEQ, which was approved by the EPA effective February 17, 1994 (59 FR 02532Exit the TCEQ). 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 application/pdfEl Paso Limited Maintenance Plan for the Eight-Hour Primary Carbon Monoxide National Ambient Air Quality StandardExit the TCEQ was approved by the EPA effective October 10, 2017 (application/pdf82 FR 42454Exit the TCEQ). 

Effective December 30, 2021 (application/pdf86 FR 67864Exit the TCEQ), the EPA designated El Paso County nonattainment for the 2015 eight-hour ozone standard (70 parts per billion) and added the newly designated area to the previously designated Doña Ana County (Sunland Park) nonattainment area in New Mexico. The El Paso-Las Cruces Texas-New Mexico ozone nonattainment area is required to demonstrate transportation conformity for ozone precursors, VOC and NOX. Based on the EPA’s Transportation Conformity Guidance for 2015Exit the TCEQ Ozone NAAQS Nonattainment Areas , an area may meet transportation conformity requirements using adequate or approved MVEBs from a previous standard. El Paso County was previously designated nonattainment for the 1979 one-hour ozone standard, and VOC and NOX MVEBs from the 1994 application/pdfSection 818 Demonstration for the El Paso Nonattainment AreaExit the TCEQ were found adequate for conformity purposes effective January 12, 1998 (application/pdf64 FR 31217Exit the TCEQ). The El Paso County portion of the El Paso-Las Cruces Texas-New Mexico ozone nonattainment area will meet transportation conformity requirements using the previously approved one-hour ozone standard MVEBs. The Doña Ana County portion of the El Paso-Las Cruces Texas-New Mexico ozone nonattainment area has no previously approved VOC and NOX MVEBs and meets transportation conformity requirements through an interim emissions test provided in 40 CFR §93.119Exit the TCEQ.

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 application/pdfDallas-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 (application/pdf86 FR 24717Exit the TCEQ).

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 an interim test provided in 40 CFR §93.119Exit the TCEQ.

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