Welcome to EMFACWeb

This website provides California's emissions inventories of on-road mobile sources and tools to perform project-level assessment with custom meteorological conditions and scenario analysis with custom vehicle activity. It also provides detailed vehicle population information aggregated up to the census block group level. This website is named after , a model that estimates the official emissions inventories of onroad mobile sources in California.

Updates

2026

  • August 2026: A pivot table feature has been added to Emissions Inventory and Fleet Database. To use it, click on the upper right corner of the output table. A pivot table allows you to quickly reorganize and summarize the data by selecting the fields you want to group or aggregate.
  • June 2026: EMFAC2025 Technical Documentation is released and available online along with EMFAC2025 v2.1.1. Please see the Appendix of the Technical Documentation for details about the updates in EMFAC2025 v2.1.1.
  • April 2026: EMFAC Web is updated to better support processing Project Analysis requests and generating Scenario Analysis templates by implementing a queuing system similar to the one used for Scenario Analysis template processing. Users can now also see the position of their requests in the queue.
  • March 2026: EMFAC2025 v2.1.0 is released. This EMFAC Web Platform has been updated to support the new version, and the EMFAC2025 PC Application v2.1.0 is also available for download here. After EMFAC2025 v2.0.0 was released in May 2025, three unlawful congressional resolutions purported to disapprove U.S. EPA's actions to grant California waivers for several regulations in the model, including Advanced Clean Cars II, Advanced Clean Trucks (ACT), Zero-Emission Airport Shuttle, Heavy-Duty Vehicle and Engine Emission Warranty and Maintenance Provisions (Warranty Phase 1), and Heavy-Duty Omnibus (Omnibus). While these illegal actions are being contested, the updated EMFAC2025 v2.1.0 is released to reflect the current regulatory conditions. Please note EMFAC2025 v2.1.0 is not yet approved by U.S. EPA for SIP and transportation conformity purposes.
  • March 2026: Fleet Database is updated with data generated from the 2024 vehicle registration database.
  • January 2026: Community-Level Heavy-Duty Vehicle Emission Inventory is provided under Community-Level.

2025

  • May 2025: EMFAC2025 v2.0.0 has been released. This EMFAC Web Platform has been updated to support EMFAC2025, and the EMFAC2025 PC Application is now available for download, along with the User's Guide.

2024

  • October 2024: Fleet Database is updated with data generated from the 2023 vehicle registration database.
  • May 2024: Fleet Database is updated with data generated from the 2022 vehicle registration database.
  • October 2023: All Off-Road tools have moved to the Off-Road WebTool

Tutorials on How to Use EMFAC Web Platform

1. Introduction to the website

Related Resources

Contact Us

This website is operated by the Mobile Source Analysis Branch in the Air Quality Planning and Science Division at the California Air Resources Board. EMFAC source code is available upon request. For questions or comments, please contact the EMFAC team.