Congestion Mitigation and Air Quality (CMAQ) Program
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Congestion Mitigation and Air Quality (CMAQ) Background
The Congestion Mitigation and Air Quality (CMAQ) Program (23 U.S.C. 149) was established by the 1991 Federal Intermodal Surface Transportation Efficiency Act (ISTEA) and was most recently reauthorized with the passage of the Infrastructure Investment and Jobs Act (IIJA) in 2021. CMAQ funds are directed to transportation projects and programs which contribute to the attainment or maintenance of National Ambient Air Quality Standards (NAAQS) in nonattainment or air quality maintenance areas for ozone, carbon monoxide, or particulate matter (PM) under provisions in the Clean Air Act (Title 42, United States Code).
As the direct recipient of federal funds for California, the California Department of Transportation (Caltrans) has statewide oversight responsibility for the CMAQ program. In areas of California represented by a federally designated Metropolitan Planning Organization (MPO), the selection of CMAQ projects takes place at the regional level by the state’s MPOs. In rural areas of the State that are not represented by a federally designated MPO, Caltrans coordinates with the state designated Regional Transportation Planning Agencies (RTPAs) on CMAQ project selection. (Map of MPOs and RTPAs in California (PDF download))
Under the CMAQ program, State Departments of Transportation (DOTs) and MPOs are encouraged to consult with State air quality agencies such as the Californai Air Resources Board (CARB) on the estimated emission reductions from proposed congestion mitigation and air quality improvement programs and projects. CARB helps estimate the emissions benefits of the state's CMAQ projects by providing technical assistance and tools that can optionally be used by MPOs, RTPAs and project sponsors.
Virtual Public Workshop: Improved Tools to Evaluate Air Quality Benefits of Transportation Projects
CARB invites you to participate in a virtual public workshop to learn about technical resources and tools that CARB is developing to help evaluate the air quality benefits of transportation projects, including updates to the CMAQ and MV Fees quantification methodologies document and automated tool.
- Notice of virtual public workshop (en español)
- Public workshop presentation (en español)
- Public workshop recording (en español)
Cost Effectiveness Analysis
Quantification Methodologies
The Methods to Find the Cost-Effectiveness of Funding Air Quality Projects document includes methods and examples for evaluating the emission reductions and cost-effectiveness of CMAQ projects and Assembly Bill (AB) 2766 Motor Vehicle (MV) Fees projects.
Automated Tool
The following tool enables staff and decision-makers to quantify the cost-effectiveness of proposed projects in terms of cost per pound (or ton) of pollutants reduced. This tool is used to evaluate projects and to report on both the CMAQ and the Motor Vehicle Registration Fee Program.
This automated Access database program allows users to quantify emissions benefits for the following project categories: cleaner on- and off-road vehicle purchases and re-powers; cleaner street sweepers; new bus service operations; vanpool and shuttle service; traffic signal coordination; bicycle facilities; telecommute programs; ridesharing, pedestrian facilities, or any other project that reduces auto trips or auto trip lengths.
- Automated Cost-effectiveness Calculation Tool (MS Access database download*)
*Note that, in order to use the MS Access database (.mdb) file, after downloading the file you may need to open the file properties and check the box labeled “unblock.”
Emission Factor Tables
The latest emission factor tables below are to be applied in the Automated Cost-effectiveness Calculation Tool.
- Emission Factors Tables (September 2025)
Additional Resources
FHWA CMAQ Emissions Calculation Tools
The Federal Highway Administration (FHWA), in cooperation with the Federal Transit Administration, has also developed cost-effectiveness analysis methods for various types of CMAQ projects. Staff may also apply these analysis methods developed by FHWA to estimate the cost-effectiveness of CMAQ projects when appropriate:
FHWA CMAQ Project Eligibility Information
On November 6, 2024, the U.S. Department of Transportation (DOT) and FHWA announced the availability of FHWA CMAQ Program Interim Guidance (2024 Interim Guidance) in the Federal Register. That guidance and accompanying fact sheet are provided below for reference:
CARB Contact Information
If you have any questions on the CMAQ program, please send an email to CMAQ@arb.ca.gov