Project-Level Conformity and Hot-Spot Analyses
This page contains policy guidance, technical guidance, and other resources issued by EPA to assist agencies in completing project-level conformity analyses, including particulate matter (PM2.5 and PM10) and carbon monoxide (CO) "hot-spot" analyses.
- PM Hot-spot Analyses: Guidance
- CO Hot-spot Analyses: Guidance
- CO Hot-spot Analyses: FHWA Categorical Finding
- Emission Models and Methods
- Air Quality (Dispersion) Models
- Tools for Completing Project-level Analyses
- Training and Other Resources
- Frequently Asked Questions
- Contact Information
Transportation Conformity Guidance for Quantitative Hot-spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas
EPA has released final guidance for modeling the local air quality impacts of certain transportation projects on the PM2.5 and PM10 national ambient air quality standards (NAAQS). This guidance is to be used by state and local agencies to conduct quantitative PM "hot-spot analyses" for new highway and transit projects that involve significant diesel emissions. This guidance describes how to estimate project emissions using EPA's MOVES model, California's EMFAC model, and other methods. It also outlines how to apply air quality models (such as AERMOD and CAL3QHCR) for PM hot-spot analyses. The guidance also includes a list of additional resources that may assist agencies in conducting quantitative PM hot-spot analyses.
Update of November 2015: This guidance has been updated to reflect MOVES2014 and its subsequent minor revisions such as MOVES2014a, to revise design value calculations to be more consistent with other EPA programs, and to reflect guidance implementation and experience in the field. Please see the November 2015 guidance change bulletin below for more information.
Contact: Laura Berry at email@example.com
- Main document only (PDF) (160 pp, 3MB, EPA-420-B-15-084, November 2015)
- Appendices only (PDF) (82 pp, 1MB, EPA-420-B-15-084-Appendices, November 2015)
- Guidance Change Bulletin: November 2015 (PDF) (3 pp, 182K, EPA-420-B-15-090, November 2015)
California: Project sponsors can find guidance in Section 5.2 of the PM Hot-spot Guidance for characterizing a project in terms of links. While the remainder of Section 5 and Appendices G and H no longer apply (as they reference EMFAC2011), all other sections of EPA’s PM Hot-spot Guidance are relevant. For specific guidance on using EMFAC, project sponsors in California should refer to the California Air Resource Board’s Project-Level Handbooks:
- Previous Guidance Change Bulletins:
- Guidance Change Bulletin: November 2013 (PDF) (1 pp, 491K, EPA-420-B-13-056, November 2013)
- Using MOVES2014 in Project-Level Carbon Monoxide Analyses (PDF) (55 pp, 603 K, EPA-420-B-15-028, March 2015)
This guidance describes how to use the MOVES2014 emissions model to estimate CO emissions from transportation projects, including roadway intersections, highways, transit projects, parking lots and intermodal terminals. This guidance can be applied when using MOVES2014 to complete any project-level quantitative CO analysis, including hot-spot analyses for transportation conformity determinations, modeling project-level emissions for SIP development, and completing NEPA analyses.
Contact: Technical questions about this guidance can be directed to firstname.lastname@example.org.
- Guideline for Modeling Carbon Monoxide From Roadway Intersections (PDF) (57 pp, 1.76 MB, EPA-454/R-92-005, November 1992)
This guidance describes how to evaluate CO air quality impacts at intersections to determine if they exceed the National Ambient Air Quality Standards for CO.
- Note: All new quantitative CO hot-spot conformity analyses outside of California must be based on MOVES2014b or MOVES2014, as the grace period for MOVES2014a. See the Federal Register notice (PDF) (5 pp, 230 K, published October 7, 2014) and EPA's latest MOVES policy guidance for details.
On July 17, 2017, the Federal Highway Administration (FHWA) announced the availability of an updated carbon monoxide categorical hot-spot finding for certain projects involving a large urban intersection. Where a project’s parameters fit the conditions of the categorical hot-spot finding, project sponsors may be able to rely on the categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project-level conformity determination in CO maintenance areas outside of California. The interagency consultation process should be used to determine whether the CO categorical hot-spot finding applies to a particular project, and any project-level conformity determination that relies on FHWA’s finding would be subject to public involvement requirements (40 CFR 93.105).
EPA requested additional receptors in this analysis to help demonstrate that the receptors in fact do include the location of highest concentration, and thus the analysis meets the requirements of the Clean Air Act. These additional receptors are shown in the Technical Documentation, Figure 5.
- FHWA Memorandum
- FHWA’s CO Categorical Hot-spot Finding
- FHWA’s CO Categorical Hot-spot Finding Technical Documentation
See FHWA’s CO categorical hot-spot finding website for more information about the finding. Questions about applicability of the finding can be addressed to the appropriate EPA Regional staff or contact email@example.com.
- Approved Versions of Emissions Models
The following is a summary of currently approved on-road emissions models for quantitative PM and CO hot-spot conformity analyses. This is only a summary; refer to the appropriate guidance and model websites for more information about the applicability and use of these models.
See Emission models and conformity for the MOVES3 Policy Guidance.
Emissions Model Geographic Applicability Federal Register Notice of Approval
Link to Model Information MOVES3 All states other than California Official Release of MOVES3 Motor Vehicle Emissions Model for Emissions Inventories in SIPs and Transportation Conformity (PDF) (5 pp, 260K, published January 7, 2021) www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves MOVES2014b, MOVES2014a and MOVES2014 All states other than California Official Release of the MOVES2014 Motor Vehicle Emissions Model for SIPs and Transportation Conformity (PDF) (5 pp, 230K, published October 7, 2014) www.epa.gov/moves/moves-versions-limited-current-use EMFAC2017 California only Official Release of EMFAC2017 Motor Vehicle Emissions Factor Model for Use in the State of California (August 15, 2019) ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-modeling-tools
- Estimating Road Dust Emissions
Road or construction dust can be quantified for a PM hot-spot analysis using EPA's AP-42 method or alternative local methods. AP-42 is EPA's compilation of data and methods for estimating average emission rates from a variety of activities and sources from various sectors. EPA's website AP-42: Compilation of Air Emissions Factors has the latest version of AP-42 and more information about AP-42 in general. The sections of AP-42 that address emissions of re-entrained road dust from paved and unpaved roads and emissions of construction dust are found in AP-42, Chapter 13, "Miscellaneous Sources". The key portions of the chapter include:
- Section 13.2: "Introduction to Fugitive Dust Sources"
- Section 13.2.1: "Paved Roads"
- Section 13.2.2: "Unpaved Roads
- Section 13.2.3: "Heavy Construction Operations" (includes road construction)
- Guidance on New R-LINE Additions to AERMOD 19191 for Refined Transportation Project Analyses (PDF) (23 pp, 749 K, EPA-420-B-19-042, September 2019)
This guidance addresses the use of the new R-LINE features in AERMOD 19191 for dispersion modeling of transportation sources. The guidance also explains that some of these features can be used for transportation conformity purposes only with EPA approval and some of these features cannot be used for regulatory purposes at this time.
- Additional Methods, Determinations, and Analyses to Modify Air Quality Data Beyond Exceptional Events (PDF) (12 pp, 183 K, EPA-457/B-19-002, April 2019)
This guidance clarifies the types of regulatory determinations, actions, and analyses for which EPA may consider certain modified air quality monitoring data, either under the Exceptional Events Rule or under other sections of the Clean Air Act (CAA) and EPA rules or guidance.
- Recommended Air Quality (Dispersion) Models for PM Hot-spot Analyses
The following is a summary of recommended air quality models for completing PM hot-spot analyses for different types of transportation projects. This is a reproduction of Exhibit 7-2 of the Quantitative PM Hot-spot Guidance.
|Type of Project||Recommended Model(s)|
|Highway and intersection projects||AERMOD*|
|Transit, freight, and other terminal projects||AERMOD|
|Projects that involve both highway/intersections and terminals, and/or nearby sources||AERMOD|
*Note, the grace period for the use of CAL3QHCR in PM hot-spot analyses has ended. All new PM hot-spot analyses begun after January 20, 2020 must use AERMOD. For more information, refer to EPA’s refer to EPA’s Revisions to the Guideline on Air Quality Models final rule (PDF) (54 pp, 743 K, published January 17, 2017).
- See Section 7 of the guidance for complete information on selecting an appropriate air quality model. See below for which model versions are currently approved for regulatory use.
- Approved Versions of Air Quality (Dispersion) Models
Please refer to EPA’s web page Air Quality Dispersion Modeling - Preferred and Recommended Models for the currently approved versions of air quality (dispersion) models for quantitative PM hot-spot analyses, as recommended by EPA's "Guideline for Air Quality Models" (Appendix W to 40 CFR Part 51).
- Tool to generate EMISFACT portion of an AERMOD input file
EPA has developed a MySQL script called "MOVES2AERMOD" to automate the process of generating the EMISFACT portion of an AERMOD input file using MOVES output. The tool is intended to be used as part of a quantitative PM hot-spot analysis and can be run directly through the MOVES GUI. To obtain the tool and for more information, see the MOVES tools page.
- Quantitative PM Hot-spot Analysis Training
EPA has developed a three-day training course on implementing EPA's guidance. This technical, hands-on course is geared toward state and local agencies and focuses on using emission models (including EPA's MOVES model) and EPA’s air quality model AERMOD for quantitative PM hot-spot analyses. The PM hot-spot analysis training page provides the latest training materials and other information.
- MOVES Model Information and Training
- The EPA's MOVES page provides complete information about the model, including downloads, technical guidance, and tools.
- The MOVES listserv provides updates on MOVES and other mobile source emissions models. Sign up here.
- EPA has developed a two-day, hands-on course geared toward state and local agencies who will use MOVES for developing SIPs and regional conformity analyses, as well as a shorter web-based course for people interested in a general overview of MOVES. The MOVES training page contains information about this and other MOVES training information, courses, and webinars.
- Air Quality Model Information
- More information about dispersion models (including AERMOD and CAL3QHCR), meteorology preprocessors, and related tools, guidance, and outreach can be found on EPA's Support Center for Regulatory Atmospheric Modeling (SCRAM) website.
- The SCRAM RSS feed provides updates on recent posting and additions to the SCRAM website. Sign up here.
This presentation, given at the January 2020 Transportation Research Board (TRB) annual conference, includes lessons learned about air quality model-to-monitor comparisons and best practices for future dispersion modeling research.
- New R-LINE Additions to AERMOD 19191 for Refined Transportation Projects
This presentation, given via webinar in the fall of 2019, provides an overview of EPA’s Guidance on New R-LINE Additions to AERMOD 19191 for Refined Transportation Project Analyses (PDF) (23 pp, 749 K, EPA-420-B-19-042, September 2019). It focuses on the R-LINE features of AERMOD 19191 and the circumstances under which they can be used.
- PM Hot-spot Modeling: Lessons Learned in the Field
This presentation, given at the January 2014 TRB annual conference, covers some of the modeling issues that have arisen in the field and the correct application of the models for hot-spot modeling.
- Overview of EPA's Quantitative PM Hot-spot Guidance
This general overview was presented several times after the release of the guidance in 2011 and was updated October 2014.
- Additional conformity-related training information and presentations.
- EPA FAQs
The following are frequently asked questions about conducting hot-spot analyses for transportation conformity purposes. EPA will update these periodically.
- PM hot-spot Analysis FAQs (PDF) (7 pp, 151 K, EPA-420-F-18-011, June 2018)
- Frequently asked questions about near roadway air pollution and heath (PDF)(9 pp, 503 K, EPA-420-F-14-044, August 2014)
- Federal Highway Administration PM2.5 FAQs
FHWA has developed a series of FAQs specifically for PM2.5 project-level conformity and hot-spot analyses. These FAQs were coordinated with EPA. The FHWA PM2.5 Project-Level Conformity and Hot-Spot Analyses FAQsExit webpage has more information.
- EPA Regional Conformity Contacts
EPA regional conformity staff are the primary EPA contacts for project sponsors completing project-level analyses for conformity purposes and should be contacted first for information and questions about these analyses. For the complete list of contacts by region, please see State and Local Transportation Regional Contacts.
- Technical questions about using MOVES for project-level analyses can be directed to firstname.lastname@example.org.
- EPA's Office of Air Quality Planning and Standards maintains a list of state air quality modeling staff who have experience that may be useful to a project sponsor when completing a hot-spot analysis, including running the selected air quality model and finding representative background data for a project. See OAQPS's state contacts page for more information.