California Department of Transportation

Division of Environmental Analysis (DEA) LINKS

square icon

Adobe Acrobat Reader is required to view and print PDF files. Adobe Acrobat is required to edit online forms and save them to your computer.

Get Acrobat Reader Image


Last Updated: Wednesday, January 17, 2018 12:34 PM


Emission factors that represent the vehicle fleet, speeds, and environmental conditions associated with a project are needed to perform project-level air quality modeling.The EMFAC model issued by the California Air Resources Board is used for this process in California. For more details regarding project-level "hot spot" modeling, please refer to the CO Protocol, Appendix B and the U.S. EPA's latest guidance Exit Caltrans website for particulate matter hot spot analysis.

The California Air Resources Board (CARB) officially released EMFAC 2014 Exit Caltrans website on December 31, 2014. On December 14, 2015, the U.S. EPA approved EMFAC 2014 for use in state implementation plan (SIP) development and transportation conformity analysis in California. The U.S. EPA allows a 24-month grace period from the approval date to transition to EMFAC 2014. More detail is available at the Federal Register notice Exit Caltrans website.

Do not use EMFAC 2007 for new studies. Conformity studies begun with EMFAC 2007 may be completed with it as long as, in general, studies are completed within 3 years of starting work. For project-level conformity purposes, EPA will generally accept a project-level conformity determination if the Final NEPA document is completed and the project approved within 3 years of circulating the Draft NEPA document based on the older model version.

EMFAC software should be obtained from the ARB website Exit Caltrans website.

The EMFAC model and all supporting data are provided and supported by the California Air Resources Board Exit Caltrans website.


CT-EMFAC has been updated based on EMFAC 2014 and MSAT specification factors from the CARB and the U.S. EPA. For more information and to download the software package, see the CT-EMFAC page.

DO NOT USE CT-EMFAC 4 (EMFAC 2007) FOR ENVIRONMENTAL DOCUMENT AIR QUALITY STUDIES STARTED ON OR AFTER OCTOBER 1, 2011. Do not use CT-EMFAC 4 (EMFAC 2007) for ANY air quality studies (including conformity) started after September 5, 2013.

FOR CONFORMITY ANALYSIS: use EMFAC 2011-SG and -PL as documented in the latest EPA quantitative hot spot analysis guidance pending availability of CT-EMFAC 5 for that purpose. CT-EMFAC 5, if and when approved by EPA, will be an alternative model for conformity use.


Return to Air Quality Home Page