CARB’s Latest On-Road Emissions Inventory Model
May 14, 2025
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On Tuesday, May 13, 2025, the California Air Resources Board (CARB) officially released EMFAC2025 to the public.
EMFAC2025 is the latest emission inventory model that CARB uses to assess emissions from on-road motor vehicles, including cars, trucks, and buses in California. It supports CARB’s planning and policy development efforts. The newest model incorporates CARB’s current understanding of statewide and regional vehicle activities, emissions, and recently adopted regulations such as Advanced Clean Cars II, the Federal Clean Trucks Plan, and the Federal Heavy-Duty Phase 3 Greenhouse Gas (GHG) Rule. It represents a significant step forward in the ongoing improvement of the EMFAC model.
The EMFAC2025 Web Platform and personal computer (PC) Application can be accessed at:
While EMFAC2025 retains a similar user interface as EMFAC2021, users are strongly encouraged to review the User's Guide before installing and running the model. The EMFAC2025 User's Guide can be found on CARB’s Mobile Source Emission Inventory (MSEI) website.
Detailed updates to emissions inventory methodologies and data will be described in the EMFAC2025 Technical Documentation, which is scheduled for release in Summer 2025. Please note that the model has not yet been approved by the United States Environmental Protection Agency (U.S. EPA) for use in State Implementation Plan (SIP) development and transportation conformity in California.
Background
Development of EMFAC2025 began with public engagement, through a user survey conducted in Summer 2021. Staff presented updated methods, data and inventory during four public workshops held in October 2022, January 2024, October 2024 and April 2025.
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