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Last Updated: Friday, December 8, 2017 12:21 PM

Project-Level Air Quality Analysis Tools

Air quality analysts usually use the models and guidance documents described below for transportation projects in California. Many are from external agencies Exit Caltrans website including: U.S. Environmental Protection Agency , California Air Resources Board , or a local air pollution control or air quality management district .

Climate Change or Greenhouse Gas analysis may use air quality models in some cases, but other types of analysis are often preferred. See the Climate Change page at this site for more information.

Microsoft Excel™ files require use of Microsoft Excel™ or compatible spreadsheet software, or an Excel™ Viewer from Microsoft Corp .

Always check the EPA and ARB web sites for updated versions of their models when starting project analysis.

EMFAC Guidance

  • CT-EMFAC (CT-EMFAC 2014 (Version 6.0 based on EMFAC 2014)
  • EMFAC 2011 at ARB (Use EMFAC 2011-SG and/or -PL for most conformity analysis)

Carbon Monoxide (CO) Analysis Tools

Particulate Matter Hot Spot Analysis Tools

  • EPA Qualitative and Quantitative Analysis Guidance - see EPA Conformity Policy Guidance web page
    EPA's Quantitative Analysis Guidance requires use of one of the following dispersion models.
  • AP-42 for Paved Roads (EPA - see 13.2.1) | Statewide (ARB) | San Joaquin Valley (ARB) | Bay Area (not SIP-approved))
    The latest EPA revision for Paved Road dust should be used statewide for conformity analysis. Silt loading factors by county from the Statewide ARB method may be used with the newer EPA version.

    For regional analysis using AP-42, freeway emissions are commonly scaled by centerline miles, rather than by lane miles as for other types of roads; however, this procedure has not yet been fully documented, tested, and accepted by EPA for project-level use. Use of centerline mile scaling helps to adjust for the lower-than-average silt loading found on heavily used roads where most dust remains suspended. The PM10 or (in some areas) PM2.5 SIPs may provide additional local guidance regarding use of this method.
  • "Appendix W" (EPA's basic regulations regarding air quality modeling)

Air Toxics Tools

See the Standard Environmental Reference, Chapter 11 for more information on how air toxics analysis is integrated with NEPA documents.

Construction Emission Analysis

The SER currently describes a qualitative approach for construction-stage (short term) air quality analysis. In some cases, analysts may wish to quantify emissions. If you are considering conducting a quantitative analysis of construction emissions, consult with the Headquarters Environmental Coordinator assigned to the project area. Several options exist for analysis and evaluation, but there is no statewide standard method. These may be helpful as starting points:

Other Tools

  • Other Tools Page
    Other analysis tools/guidance developed by or for Caltrans, that don't fit easily in a category above, are available at this page.
  • CalEEMod land development emission model
    CalEEMod is not ideal for road construction emission analysis – it is oriented mainly at general land development analysis – but may be useful under special circumstances..
    EMFAC 2011 version was released late in September 2013 - download the new version if this tool is to be used.
  • Direct Travel Impact Model (DTIM) Manual
    This model applies EMFAC to a loaded travel demand model network, producing link-by-link emissions and "gridded" emissions that are used to adjust EMFAC regional emission burden for input to photochemical models. Intended mainly for regional air quality analysis and currently used only in SIP development, but potentially useful for very large projects that use a travel demand model or similarly structured traffic model. The model itself can be obtained by contacting
  • DVTOOL (Updated version posted on April 28, 2017)
    This is a stand-alone tool to assist with calculating ‘Design Value’ in a PM hot-spot analysis.
  • AERMOD View Guidance
    This is a set of guidance documents developed for Caltrans staff to assist with use of Lakes Environmental's AERMOD View software.
  • EM4AQ (Posted on April 28, 2017) New Item
    This is a tool to assist with generating emissions input for AERMOD modeling.
  • Ethylbenzene Emissions Calculator (Posted on April 28, 2017) New Item
    This is a tool to assist with generating ethylbenzene emissions.
  • DataBridge (Posted on May 9, 2017) New Item
    DataBridge is a travel activity data process tool for generating input data for project-level emissions calculation in CT-EMFAC2014 and EM4AQ.

Caltrans Standard Environmental Reference

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