Air quality toolkit
The Clean Air Act, the National Environmental Policy Act (NEPA) and the Federal-Aid Highways Code regulate the potential effects caused by proposed transportation projects on air quality in Texas.
Use the following tools to document project-level compliance with laws, regulations and guidance.
Questions? Contact the Air Quality Section of the Environmental Affairs Division at 512-416-3001.
View frequently asked questions at online forms FAQs.
Accessing documents
| Title | Date | Description |
| Running ERLT | 04/26 | Provides tabular emission rates for running emissions for MSAT analyses. |
| Idling ERLT | 04/26 | Provides tabular emission rates for idling emissions. |
| Extended Idling ERLT | 04/26 | Provides tabular emission rates for extended idling of heavy-duty trucks. For limited special case uses. |
| Starts ERLT | 04/26 | Provides tabular emission rates for vehicle starts. For limited special case uses. |
| CO TAQA Running ERLT | 04/26 | This table provides the running emission rates to be used solely for the CO TAQA. |
| CO TAQA Idling ERLT | 04/26 | Provides tabular emission rates for idling emissions. For use in CO TAQAs for intersection queueing. |
| Frequently Asked Questions – Air Quality | 04/26 | Answers commonly asked questions concerning project-level compliance with transportation-related air quality requirements. |
| Air Quality Compliance Flowchart for FHWA/FTA and State-Only Projects | 07/21 | Outlines the steps to comply with the Clean Air Act (CAA), NEPA and the Federal-Aid Highways Code regarding potential project effects on air quality |
| Air Quality Compliance Flowchart for Other Federal Projects | 07/21 | Outlines the steps to comply with the CAA, NEPA and the Federal-Aid Highways Code regarding potential project effects on air quality |
| Environmental Handbook for Air Quality | 03/26 | Outlines the steps to comply with the CAA, NEPA and the Federal-Aid Highways Code regarding potential project effects on air quality |
| Guidance for Preparing Air Quality Statements | 08/26 | Contains the applicable finding and negative declaration statements for documenting air quality compliance with applicable laws, regulations and guidance |
| Title | Date | Description |
| Texas Air Quality Nonattainment or Attainment-Maintenance Areas and Counties - May 7, 2026 | 05/26 | Provides tabular information on nonattainment/maintenance counties and transportation plan conformity dates |
| Review Standard for a Conformity Report | 04/26 | Verifies that a project-level conformity report meets requirements |
| Transportation Conformity Report Form | 08/26 | Used to prepare the conformity report |
| Title | Date | Description |
| Review Standard for a Hot-Spot Analysis Technical Report | 10/26 | Verifies that a Hot-Spot Analysis report meets requirements |
| Documentation Standard for a Hot-Spot Analysis Technical Report | 04/26 | Lists the required sections and components of a Hot-Spot Analysis Technical Report |
| Decision Form: Project of Local Air Quality Concern (POAQC) | 04/23 | After a metropolitan planning organization (MPO) schedules a conference call, the project sponsor completes and sends this form to partners to determine whether the proposed project is "of air quality concern" |
| POAQC Decision Sheet | 08/23 | This chart is a quick reference guide that shows common types of projects that require a POAQC decision and common types of projects that are exempt from a POAQC decision. |
| Title | Date | Description |
| Documentation Standard for Quantitative MSAT Technical Report | 06/26 | Used to prepare a quantitative MSAT technical report for TxDOT projects |
| Review Standard for Quantitative MSAT Technical Report | 04/26 | Used by TxDOT to review a quantitative MSAT technical report for TxDOT projects |
| Title | Date | Description |
| Report: Ambient Near-Road Mobile Source Air Toxics Concentrations in the United States | 12/19 | Analysis of near-road MSAT monitor concentrations and the potential contribution from roadways. |
| Report: Near-Road Particulate Pollution: PM2.5 Black Carbon, and Ultrafine Particles at U.S. Near-Road Monitoring Sites | 12/19 | Analysis of near-road PM2.5, black carbon, and ultrafine particle monitor concentrations and the potential contribution from roadways. |
| Report: Influence of Roadway Emissions on Near-Road PM2.5: Monitoring Data Analysis and Implications for Determining Transportation Projects of Local Air Quality Concern (POAQC) | 10/19 | Identifies the influence of roadways on near-road PM2.5 emissions |
| Aviation Emissions and Air Quality Handbook | Explains Federal Aviation Administration (FAA) air quality guidelines and procedures for projects involving civilian airports and air force bases when FAA is the lead federal agency | |
| Determining Conformity of Federal Actions to State or Federal Implementation Plans (40 CFR 93) | EPA-administered code implementing Section 176(c) of the CAA (42 USC 7401) and the related requirements of 23 USC 109(j) and establishing policy, criteria and procedures to demonstrate and ensure project conformity with an implementation plan developed pursuant to Section 110 and Part D of the CAA | |
| Supplement to Jan. 28, 2008 Transportation Planning Requirements and their Relationship to NEPA Process Completion (02/09/11) Distribution Memo | Provides a detailed description of how transportation planning relates to the NEPA process (i.e., project-level consistency and conformity) | |
| Transportation Conformity: A Basic Guide for State and Local Officials | Provides FHWA's high-level overview of transportation conformity and how requirements relate to transportation investments and the implications on metropolitan transportation plans, transportation improvement programs and transportation projects | |
| Transportation Conformity Brochure | FHWA answers to basic questions about transportation conformity | |
| Transportation Conformity Guidance for Quantitative Hot-Spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas | EPA guidance for quantitative PM hot-spot analyses for projects of “air quality concern” in PM nonattainment/maintenance areas where a hot-spot analysis is started post December 2012 | |
| Guidelines for Modeling Carbon Monoxide from Roadway Intersections | EPA guidance on how to model CO at roadway intersections for CO hot-spot analyses | |
| Using MOVES in Project-Level Carbon Monoxide Analyses | EPA guidance for using its mobile vehicle emission simulator (MOVES) emission model rather than the older MOBILE emissions model in CO hot-spot analyses where the analysis was started post December 2012 | |
| FHWA Technical Advisory for Preparing and Processing Environmental and Section 4(f) Documents T 6640A | FHWA guidance on preparing environmental documents outlining the requirements for performing a CO TAQA and disclosing construction emissions under NEPA | |
| Interim Guidance Update on Mobile Source Air Toxic Analysis in NEPA Memorandum | Provides an update to FHWA guidance on MSAT analyses | |
| A Methodology for Evaluating Mobile Source Air Toxic Emissions Among Transportation Project Alternatives | Detailed guidelines on performing quantitative MSAT analysis | |
| Frequently Asked Questions (FAQ) Conducting Quantitative MSAT Analysis for FHWA NEPA Documents | Provides FHWA recommendations for project sponsors using MOVES for NEPA MSAT analysis concerning defining the scope of MOVES work, gathering input data, and post-processing results |
| Title | Date | Description |
| Documentation Standard for a CO TAQA Technical Report | 05/26 | Used to prepare a CO TAQA technical report |
| Review Standard for CO TAQA Technical Report | 04/26 | Used by TxDOT to review a CO TAQA technical report for TxDOT projects |