Mobile Source Emissions Inventory -- Categories

This page last updated on February 03, 2016

Category specific emissions estimates have been developed over the past several years in support of specific agency regulatory objectives. Documentation and emissions estimates are available through the regulatory process. This site provides links to available information for each rulemaking.

On-Road Motor Vehicles:

The EMFAC emissions model is developed and used by ARB to assess emissions from on-road vehicles including cars, trucks, and buses in California, and to support ARB's regulatory and air quality planning efforts to meet the Federal Highway Administration's transportation planning requirements. USEPA approves EMFAC for use in State Implementation Plan and transportation conformity analyses. The most recent approved version is EMFAC2014 (Federal Register Notice).

Recommended Tools to Use for On-Road Emissions Analyses
Analysis Recommended Tool
Criteria Pollutant Emissions EMFAC, EMFAC Web Database
Greenhouse Gas Emissions Greenhouse Gas Inventory
State Implementation Plans EMFAC with MPO Activity
Conformity Analyses EMFAC with MPO Activity
SB375 Analyses EMFAC with MPO Activity and SB375
CEQA with Localized Data EMFAC Emission Rates Mode (PL)

EMFAC2014 (USEPA Approved)

Effective December 14, 2015, the USEPA has approved the EMFAC2014 emissions model for SIP and conformity purposes (Federal Register Notice). As the latest version of the model, EMFAC2014 represents ARB's current understanding of motor vehicle travel activities and their associated emission levels. Compared to previous versions of EMFAC, there has been a variety of changes to the Graphical User Interface and to the overall flow of using EMFAC. As a result, it is strongly recommended that users thoroughly read the User's Guide before installing and running the model. Please join the MSEI mailing list if you would like to be informed of general developments related to EMFAC2014. For EMFAC2014 related questions please email us at



Over the years ARB has also developed emissions inventories for regulatory purposes. Historical documentation and methods are posted below.

On-Road Passenger Cars and Light Trucks:


On-Road Heavy Duty Diesel Trucks:


Go to Off-Road Diesel Emissions Inventory Webpage

Off-road diesel categories include diesel equipment in construction and mining, agriculture, cargo handling equipment, transport refrigeration units, commercial harborcraft, locomotives, and ocean-going vessels.

Off-Road Gasoline Motor Vehicles:

In the past ARB released the OFFROAD model which calculated emissions from off-road sources.  The OFFROAD model is now being replaced by category specific methods and inventory models that are being developed for specific regulatory support projects.  The categories listed below have been or are being updated with new methods and data.  Where available, new inventories and models are provided.  If a category is not listed below, OFFROAD2007 is the current tool for estimating emissions.  It is available here.