Executive Summary

EPA Issues Public Draft of 

Transportation Conformity Guidance 

for Quantitative Hot-spot Analyses 

in PM and PM Nonattainment and 2.5 10

Maintenance Areas 

Overview 

For the first time, the U.S. Environmental Protection Agency (EPA) has released 

draft conformity guidance for quantifying the local air quality impacts of certain 

transportation projects on the PM and PM national ambient air quality 2.5 10 

standards (NAAQS). Once finalized, this guidance will be used by state and local 

agencies to conduct “hot-spot analyses” for new highway and transit projects that 

involve significant diesel emissions. EPA intends to finalize the guidance later 

this year, and, after a grace period, quantitative hot-spot analyses would apply in 

PM and PM nonattainment and maintenance areas. Until then, qualitative 2.5 10

analyses continue to apply in PM areas, using previously issued joint EPA-FHWA 

guidance on such analyses. EPA has not issued this PM hot-spot modeling guidance 

in the past because appropriate models were not available for quantifying PM 

emissions from individual transportation projects. Now that EPA has released its 

new MOVES2010 emissions model, an appropriate model is available for EPA 

to use to develop guidance for the use of quantitative PM hot-spot analyses in 

conformity determinations. EPA developed this draft guidance in coordination with 

the Department of Transportation, state and local agencies, and other stakeholder 

groups. 

EPA is seeking public comment on all aspects of the draft guidance by July 19, 2010; 

see below for further details on how to submit comments. 

Purpose of the Draft Guidance 

This draft guidance describes how to complete quantitative PM hot-spot analyses. 

A hot-spot analysis is an analysis of a project’s impact on the NAAQS in the local 

Office of Transportation and Air Quality 

EPA-420-F-10-036 

May 2010 
Executive Summary 

 

 

area of the project. A hot-spot analysis is required only for new highway and transit projects that 

involve significant diesel truck or bus traffic. 

This draft guidance describes how to estimate project emissions using EPA’s MOVES2010 

model, California’s EMFAC2007 model, and other methods. It also outlines how to apply air 

quality models (AERMOD and CAL3QHCR) for PM hot-spot analyses. Finally, the draft 

guidance includes appendices that provide additional resources and examples that may assist 

state and local agencies in conducting quantitative PM hot-spot analyses. A description of each 

section of the draft guidance is included below. 

Background 

Transportation conformity is a Clean Air Act requirement that ensures that federally supported 

highway and transit projects are consistent with state air quality implementation plans. Conformity helps protect public health through early consideration of the air quality impacts of transportation decisions in places where air quality does not currently meet the NAAQS or has not 

met them in the past. 

Steps for Completing a Quantitative PM Hot-spot Analysis 

The flowchart on the next page illustrates the basic steps for completing a quantitative PM 

hot-spot analysis as described in the draft guidance. In general, a hot-spot analysis compares the 

air quality concentrations with the proposed project (the “build” scenario) to air quality concentrations without the project (the “no-build” scenario). For either scenario, it is necessary to 

consider emissions from the project and any nearby sources, as well as determine background 

concentrations. From this information, design values can be calculated to determine if a project 

conforms. If the build design values are less than or equal to the relevant NAAQS, the project is 

considered to conform. A project will also conform if the build scenario design values are greater 

than the NAAQS but less than or equal to the design values for the no-build scenario. 

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Overview of the Quantitative PM Hot-spot Analysis Process 

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Summary of Contents of Draft Guidance 

The following is a section-by-section description of the contents of the draft guidance: 

Section 1: Introduction 

This section provides general information about PM hot-spot analyses and introduces the 

guidance. 

Section 2: Transportation Conformity Requirements 

This section outlines the transportation conformity requirements for quantitative PM hot-spot 

analyses. This section also describes general statutory and regulatory requirements, specific 

analytical requirements, and the different types of agencies that are involved in developing hotspot analyses. 

Section 3: Overview of a Quantitative PM Hot-Spot Analysis 

This section provides an overview of the process for conducting a quantitative PM hot-spot 

analysis. This section may be particularly helpful to those who are looking for a general understanding of this process. All individual elements or steps presented in this section are covered 

in more depth throughout the remainder of the guidance. 

Section 4: Estimating Project-level PM Emissions Using MOVES 

This section describes how to use EPA’s MOVES2010 emissions model to estimate a project’s 

exhaust, brake wear, and tire wear emissions for PM hot-spot analyses outside of California. 

This section focuses on determining what the appropriate project-level inputs are and how 

MOVES should be run to provide the necessary information to complete air quality modeling. 

Section 5: Estimating Project-Level PM Emissions Using EMFAC (in California) 

This section addresses the necessary steps to use the EMFAC model to estimate a project’s exhaust, brake wear, and tire wear emissions for PM hot-spot analyses in California. The California Air Resources Board maintains EMFAC, which is approved by EPA for developing on-road 

motor vehicle emission inventories and conformity analyses in California. 

Section 6: Estimating Emissions from Road Dust, Construction, and Other Emission Sources 

This section describes how to estimate re-entrained road dust and transportation-related construction dust emissions. This section also includes information on quantifying emissions from 

construction vehicles and equipment, locomotives, and other sources of emissions in the project 

area, when applicable. 

Section 7: Selecting an Air Quality Model, Data Inputs, and Receptors 

This section describes the recommended air quality models (AERMOD and CAL3QHCR), data 

inputs, and receptor considerations for PM hot-spot analyses. This guidance is consistent with 

the conformity rule and recommendations for air quality modeling in EPA’s “Guideline on Air 

Quality Models” (Appendix W to 40 CFR Part 51). 

Section 8: Determining Background Concentrations from Nearby and Other Emission Sources 

This section describes how to determine background concentrations for PM hot-spot analyses, 

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which can include nearby sources (e.g., locomotive emissions at a freight terminal) and other 

sources of emissions not from the project itself. 

Section 9: Calculating PM Design Values and Determining Conformity 

This section describes how to combine all previous steps of a PM hot-spot analysis into a design 

value so that a project sponsor can determine if conformity requirements are met. For conformity purposes, a design value is a statistic that describes a future air quality concentration in the 

project area that can be compared to a particular NAAQS. 

Section 10: Mitigation and Control Measures 

This section describes mitigation and control measures that could be considered by project sponsors to reduce emissions and any new or worsened PM NAAQS violation that is predicted in a 

PM hot-spot analysis. 

Appendices 

The draft guidance also contains the following appendices to supplement the above sections and 

assist state and local agencies when conducting PM hot-spot analyses: 

•	 Appendix A is a clearinghouse of information and resources external to this guidance 

which may be useful when completing PM hot-spot analyses. 

•	 Appendix B gives examples of projects of local air quality concern. 

•	 Appendix C discusses what projects need a hot-spot analysis if a state’s approved 

conformity SIP is based on pre-2006 requirements. 

•	 Appendix D demonstrates how to characterize links in an intersection when running
 

MOVES.
 

•	 Appendices E and F are abbreviated PM hot-spot analysis examples (using MOVES) for 

a highway and transit project, respectively. 

•	 Appendices G and H are examples of how to configure and run EMFAC for a highway 

and transit project, respectively. 

•	 Appendix I includes guidance for estimating locomotive emissions in the project area. 

•	 Appendix J includes details on how to input air quality modeling data and run AERMOD 

and CAL3QHCR for a PM hot-spot analysis and prepare outputs for design value 

calculations. 

•	 Appendix K has examples of how to calculate design values and determine transportation 

conformity. 

Request for Comments 

EPA is seeking public comment on all aspects of the draft guidance by July 19, 2010. In particular, 

EPA is seeking comments on the following: 

•	 Does the guidance provide sufficient information on how to configure and run
 

MOVES2010 and EMFAC2007 at the project level?
 

•	 Do the air quality modeling sections of the guidance and references to other existing 

documents provide sufficient detail for air quality modelers to conduct PM hotspot analyses using AERMOD or CAL3QHCR? 

•	 Is there sufficient information in the guidance to calculate design values and determine 

appropriate receptors? If not, what additional information is necessary? 

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•	 Are there issues that the draft guidance does not address that should be addressed in the 

final guidance or in other EPA efforts? 

•	 What types of outreach, training, and other technical assistance would be helpful in 

implementing the final guidance? 

EPA encourages those submitting comments to provide specific details and/or examples wherever possible. 

Submitting Comments 

Comments can be submitted to EPA via the following methods: 

Email: Comments can be sent electronically to PMhotspot-comments@epa.gov 

Mail: Comments sent by mail should be addressed to 

Meg Patulski
 

State Measures and Conformity Group
 

Transportation and Regional Programs Division
 

U.S. Environmental Protection Agency
 

2000 Traverwood Drive
 

Ann Arbor, MI 48105
 

Fax: Comments can also be faxed to the attention of Meg Patulski at (734) 214-4052. 

For More Information 

The draft quantitative PM hot-spot guidance can be found on EPA’s Office of Transportation 

and Air Quality website at: www.epa.gov/otaq/stateresources/transconf/policy.htm. 

For further information on the draft guidance, please contact: 

Meg Patulski 

U.S. Environmental Protection Agency
 

Office of Transportation and Air Quality
 

2000 Traverwood Drive
 

Ann Arbor, MI 48105
 

734-214-4842
 

E-mail: patulski.meg@epa.gov (Note that comments on the guidance should be submitted directly to PMhotspot-comments@epa.gov) 

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