Mobile Source Emission Inventory -- Categories

This page last updated on November 2014

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:

ARB has released EMFAC2011, which is ARB’s official model for estimating emissions from on-road cars, trucks, and buses in California.  The easiest way to access information is to start with new web-based databases that provide emissions and emission rate output at various levels of detail. 

Over the past 8 years ARB has also developed emissions inventories for regulatory purposes.  Historical documentation and methods are posted below.  Staff is currently engaged in developing emissions estimates for the Advanced Clean Cars rulemaking.


EMFAC2014 Initial Public Release (New)
ARB is releasing a draft version of EMFAC2014 on Friday, November 14, 2014 for public testing and commenting. The draft version of EMFAC2014 is capable of generating emissions estimates using EMFAC default or custom activity data as well as emission rates for project-level assessments. However, since it is an initial public release, please treat outputs as preliminary draft information.  Please do not use model results for any purposes other than for model testing because the numbers are still subject to change until the official version of EMFAC2014 is released toward the end of the year.

Software & Supporting Document:

On-Road Passenger Cars and Light Trucks:


On-Road Heavy Duty Diesel Trucks:


Off-Road 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.


Off-Road Diesel Equipment:

  • Ocean Going Vessels

Off-Road Gasoline-Fueled Equipment: