Mobile Source Emission Inventory -- Current Methods and Data

This page last updated on January 2013


EMFAC2011 - Updated: January 2013
The California Air Resources Board is releasing an update to EMFAC2011 that affects EMFAC2011-LDV and EMFAC2011-SG. All EMFAC users should download the latest version of these two modules.

The re-release includes:

  • Updated emission factor web-tools and training modules that allow easier access to emission factor data and provide some tips for obtaining and using emission factor data for project assessment
  • Updates to EMFAC2011-LDV and EMFAC2011-SG that corrects the number of starts in several smaller categories of gasoline vehicles in Santa Clara County, which had led to an overestimate of emissions. No other counties were affected, and no model algorithms were changed in the update
  • Technical documentation has been updated to reflect these improvements


EMFAC2011 is the latest installment of the EMFAC series of models, which is ARB's tool for estimating emissions from on-road vehicles. The model has been updated since EMFAC2007 and is now comprised of three separate modules.  Because running the model is more complex now than for EMFAC2007, we recommend users obtain EMFAC2011 output from our new web-based data access tools provided below. 



Web Based Training:

  • Introduction to Models and Website: MP4, Quicktime
  • Using EMFAC2011 for Project Level Assessment: MP4, Quicktime (UPDATED January 2013)
  • Introduction to EMFAC2011-HD: Demonstration: MP4, Quicktime
  • Introduction to EMFAC2011-SG: Demonstration: MP4, Quicktime


EMFAC2011 Web Based Data Access:

On-line data tools provide access to EMFAC2011 emissions and emission rates to many different levels of detail. These databases have been updated as discussed above. Click on the link below to access the web data tools. 


Using EMFAC2011 for Project Level Assessment:

Here the user will find our handbook that describes how EMFAC2011 can be used for project level analysis. The handbook describes a tiered approach depending on the complexity of the assessment. For most assessments a new tool (EMFAC2011-PL) may be used that outputs emission rates in units consistent with project level assessment at the vehicle class and calendar year level by process. These emission rates are consistent with EMFAC2011-modules and on-line databases. The handbook also describes how for the most detailed assessments the EMFAC2011-LDV module may be required.

The  U.S. EPA has released a revision to the Quantitative PM Hot-spot Guidance, dated November 2013.  This guidance, which was originally released in 2010, has been updated to reflect California’s currently-approved motor vehicle emissions model (EMFAC2011) and changes to the air quality modeling section based on U.S. EPA’s 2012 PM NAAQS final rule.   These changes are summarized in a guidance change bulletin, which can be found on the following website, along with the revised guidance, appendices, and fact sheet:


Technical Documentation and User's Guides:


EMFAC2011 Modules:


Off-Road Emissions Modeling Methods: