Air Quality Conformity

Transportation planning in the region is heavily influenced by air quality planning, which is a federal requirement. During the solicitation of projects for the metropolitan transportation plan, an implementing agency may submit a proposal for capacity expansion or reduction on the region's highway or transit networks. 

Once the TPB approves the projects, they are tested to ensure that the plan's projects collectively contribute to the air quality improvement goals embodied in the Clean Air Act Amendments of 1990. A series of tests are performed with computer models that predict how much air pollution will be generated over the next 25 years by facilities in the plan, and how much the air will be improved by cleaner gasoline standards and many other factors. 

If the plan is found by the TPB to meet regional air quality goals, federal agencies certify that the plan is "in conformity." In other words, the TPB ensures that the plan "conforms" to air quality improvement goals. If the TPB encounters difficulty in meeting conformity conformity—or expects to—it may choose to adopt Transportation Emission Reduction Measures (TERMs), such as ridesharing and telecommuting programs, improved transit and bicycling facilities, clean fuel vehicle programs or other possible actions.  

Visualize 2050
Air Quality Conformity Analysis

As the latest version of the National Capital Region Transportation Plan, Visualize 2050 is the update to Visualize 2045. In 2025, TPB staff completed an air quality conformity analysis of the regionally significant projects in the draft Visualize 2050 plan. To learn more, view the Visualize 2050 Air Quality Conformity FAQs. 

The TPB approved the air quality conformity analysis results of Visualize 2050 and the FY 2026-2029 Transportation Improvement Program (TIP) at its December 17, 2025, meeting. Read more.

Full Document:  

Air Quality Conformity Analysis Report of Visualize 2050 and the FY 2026-2029 Transportation Improvement Program

By Section:

Main Document of the Air Quality Conformity Analysis Report

Appendices:

Appendix A: Scope of Work

Appendix B: Project Inputs

Appendix C: Documentation of Data Development Process for Mobile Source Emissions Calculations

Appendix D: Transportation Control Measures (TCMs) Implementation Reports

Appendix E: Interagency Consultations and Public Involvement Process

Appendix F: TPB C-SMMPO Agreement

Visualize 2050

For more information on Visualize 2050, visit visualize2050.org.