California Department of Transportation

Last Updated: Thursday, February 6, 2014 12:48 PM



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 ONLY EMFAC 2011 Links exit the Caltrans web site - privacy and other policies may differ as published by ARB.

For general environmental analysis purposes (not related to conformity), CT-EMFAC 5 (based on EMFAC 2011) should be used.


CT-EMFAC is an interpretation of the California Air Resource Board's EMFAC model (more EMFAC information) that simplifies the process of developing composite emission factors for highway project air quality analysis. It also extends EMFAC to include EPA's 2007 priority mobile source air toxics, which require off-model speciation of Total Organic Gases (TOG) when the standard EMFAC model is used.

CT-EMFAC was developed in consultation with ARB staff, and and is designed to be used in place of the full EMFACmodel when the detailed fleet and other planning assumptions used by EMFAC are not available or not needed. Typical use would be to develop composite emission factors for running CALINE4 using Appendix B procedures from the CO Protocol, or for basic emission analysis of a highway project.

CT-EMFAC 5 is based on EMFAC 2011 Links exit the Caltrans web site - privacy and other policies may differ. It should be used for environmental analysis purposes, but cannot be used for conformity analysis purposes until it is approved by U.S. EPA Region 9 following the process defined in the March 2013 EMFAC 2011 availability notice Links exit the Caltrans web site - privacy and other policies may differ. Until EPA approves CT-EMFAC 5, project-level conformity analysis should use EMFAC 2011 as distributed by the California ARB, especially the EMFAC 2011-PL component. CT-EMFAC 5 includes napthalene and POM analysis as part of the main user interface, and does not require a separate spreadsheet as was used with CT-EMFAC 4.1.

A "Databridge" tool is also available to help format link-based travel data for use with the batch mode of CT-EMFAC. This tool is a "beta" product and could contain errors or inconsistencies - if you discover problems please let us know.

Installation Notes

CT-EMFAC requires .NET 4 or higher Links exit the Caltrans web site - privacy and other policies may differ runtime support. and Windows XP or later. Multiple versions of the .NET runtime can be used side-by-side on one computer.

Administrator access to the computer is required to install or upgrade .NET; however, most WIndows 7 installations should have .NET 4 or higher as part of the standard system image.

CT-EMFAC itself does not require administrative rights to install or use, because it should not be placed in the "Program Files" folder or some other restricted-access location. Create a new folder where the user has full (read/write) access, then extract all the files in the CT-EMFAC ZIP archive to it maintaining the file and folder structure and names in the zip file.

Download CT-EMFAC 5


  • Databridge tool (beta product) - consult the help file included in the zip file for usage instructions


CT-EMFAC was developed for Caltrans by UC Davis and Sonoma Technology Inc.
CT-EMFAC is copyright © 2007-2013 by the State of California.

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