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Last Updated: Wednesday, May 11, 2016 1:00 PM
Air quality analysts usually use the models and guidance documents described below for transportation projects in California. Many are from external agencies 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.
- CT-EMFAC (CT-EMFAC 2014 (Version 6.0 based on EMFAC 2014 - NOT FOR CONFORMITY USE)
- EMFAC 2011 at ARB (Use EMFAC 2011-SG and/or -PL for most conformity analysis)
- 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.
DO NOT USE CALINE4 FOR CONFORMITY_RELATED PM10 or PM2.5 HOT SPOT MODELING.
- 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)
- FHWA Interim Guidance (Web Page | PDF)
- Sacramento AQMD Land Use Protocol
- See also CT-EMFAC, which integrates speciation for Mobile Source Air Toxics with EMFAC emission factor and emission burden estimation.
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:
- The current version of the Sacramento AQMD Road Construction Model is available from the AQMD's CEQA Tools web page.
- OFFROAD emission inventory model and procedures
- 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
This is a stand-alone tool to assist with developing design values from dispersion model output, such as from U.S. EPA's AERMOD.
- 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.
- Chapter 11 (Air Quality)
- Chapter 13 (Energy/Climate Change)
- Chapter 38 (NEPA Delegation - see Air Quality section)