U.S. EPA Policy and Technical Guidance on Transportation Conformity

This page contains policy guidance issued by EPA and/or the U.S. Department of Transportation to assist state and local transportation and air quality agencies implement the transportation conformity program. Policy guidance can be found on the following topics:

Transportation Planning and Conformity Requirements

Baseline Year for the Baseline Year Test (in 40 CFR 93.119)
This page provides a table showing the baseline year to be used for each NAAQS and the regulatory provision where it is found.
Transportation Conformity Guidance for 2008 Ozone NAAQS Nonattainment Areas (PDF) (24pp, 180K, EPA-420-B-12-045, July 2012)
This document provides guidance for meeting transportation conformity requirements in areas designated nonattainment for the 2008 ozone national ambient air quality standards (“2008 ozone NAAQS”). It also addresses the revocation of the 1997 ozone NAAQS for transportation conformity purposes.
Contact: David Bizot at 734-214-4432 or bizot.david@epa.gov
Guidance for Transportation Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas (PDF) (54 pp, 589K, EPA-420-B-12-046, July 2012)
This guidance describes how transportation conformity determinations are done in areas where multiple metropolitan planning organizations (MPOs), states and/or other agencies have jurisdiction in a nonattainment or maintenance area. This guidance updates and supersedes the July 2004 “Companion Guidance for the July 1, 2004 Final Transportation Conformity Rule: Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards”. This guidance has been updated to apply to existing and future NAAQS, consistent with the Transportation Conformity Rule Restructuring Amendments.
Contact: Laura Berry at 734-214-4858 or berry.laura@epa.gov

Updated guidance on substituting and adding transportation control measures to approved state air quality plans(PDF) (35 pp, 401K, EPA420-B-09-002, January 2009 )
This document provides updated guidance to state and local air quality and transportation agencies on implementing the Clean Air Act provision that establishes a streamlined process for substituting or adding transportation control measures to an approved state air quality plan. Transportation control measures, such as public transit and carpooling, can provide alternatives to the public that reduce motor vehicle emissions. This document supersedes the section of the February 14, 2006 interim guidance on implementing the Clean Air Act amendments made by SAFETEA-LU that addressed this provision.
Contact: Rudy Kapichak at 734-214-4574 or kapichak.rudolph@epa.gov
EPA and DOT Joint Guidance for the Use of Latest Planning Assumptions in Transportation Conformity Determinations (23 pp, 343K, EPA420-B-08-901, December 2008)
This guidance document supersedes the January 18, 2001 guidance memorandum to address the July 1, 2004 transportation conformity final rule revisions on the use of latest planning assumptions in transportation conformity determinations.
Contact: Patty Klavon at 734-214-4476 or klavon.patty@epa.gov

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Project-Level Conformity

Please see www.epa.gov/otaq/stateresources/transconf/projectlevel-hotspot.htm for EPA’s policy and technical guidance related to project-level conformity, including:
- Guidance for PM and CO hot-spot analyses
- Information on approved emissions and air quality models for project-level analyses
- Tools, training, Frequently Asked Questions (FAQs), and other project-level analysis resources
- Contact information for project sponsors

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Emission Models and Conformity

MOVES2010 model and minor revisions are now available
EPA’s Office of Transportation and Air Quality (OTAQ) has developed the new MOtor Vehicle Emission Simulator (MOVES). See the MOVES website for further details on the model’s development and other technical supporting materials. MOVES2010b, the latest version of the MOVES2010 emissions model, is now available and incorporates new features and a number of performance improvements.
- Policy Guidance on the Use of MOVES2010 and Subsequent Minor Revisions for State Implementation Plan Development, Transportation Conformity, and Other Purposes (PDF) (19 pp, 290K, EPA-420-B-12-010, April 2012)
  This document describes how and when to use the MOVES2010 (and subsequent minor revisions like MOVES2010b) for SIP development, transportation conformity, general conformity, and other purposes.

Using MOVES to Prepare Emission Inventories in State Implementation Plans and Transportation Conformity: Technical Guidance for MOVES2010, 2010a and 2010b (63 pp, 482k, EPA-420-B-12-028, April 2012)
This document provides guidance on appropriate input assumptions and sources of data for the use of MOVES2010, MOVES2010a, and MOVES2010b in SIP submissions and regional emissions analyses for transportation conformity purposes.

Federal Register Notice of Availability: Official Release of the MOVES2010a and EMFAC2007 Motor Vehicle Emissions Models for Transportation Conformity Hot-Spot Analyses and Availability of Modeling Guidance (PDF) (December 20, 2010)
This notice approves MOVES2010a official use for quantitative CO and PM hot-spot analyses outside of California, and starts a two-year grace period before MOVES2010a is required to be used in these analyses for project-level conformity determinations outside California. This notice is applicable to current and future versions of the MOVES model, unless EPA notes otherwise when approving the model for conformity purposes. This notice also announces the availability of new guidance documents for: (1) completing quantitative PM hot-spot analyses using MOVES and other models; and (2) completing project-level CO analyses using MOVES.
Contact: Meg Patulski at 734-214-4842 or patulski.meg@epa.gov.

Federal Register Notice of Availability: Official Release of MOVES2010 Motor Vehicle Emissions Model for Emissions Inventories in SIPs and Transportation Conformity
This notice approves the use of MOVES2010 in official SIP submissions and starts a two-year grace period before MOVES2010 is required to be used in new regional emissions analyses for transportation conformity determinations outside of California.
Contact: For transportation conformity questions, contact Meg Patulski at 734-214-4842 or patulski.meg@epa.gov. For SIP questions, contact Rudy Kapichak at 734-214-4574 or kapichak.rudolph@epa.gov.
Note: EPA subsequently extended the grace period to March 2, 2013 before MOVES2010 and minor revisions is required for regional emissions analyses for transportation conformity determinations (“regional conformity analyses”). See February 2012 final rule that provides an additional year to the previously established two-year conformity grace period at: www.epa.gov/otaq/stateresources/transconf/conf-regs.htm.
Use of EMFAC2007 model in California
- Federal Register Notice of Availability: Official Release of the MOVES2010a and EMFAC2007 Motor Vehicle Emissions Models for Transportation Conformity Hot-Spot Analyses and Availability of Modeling Guidance (PDF) (December 20, 2010)
  This notice approves EMFAC2007 for quantitative PM hot-spot analyses for transportation conformity purposes within California and announces a two-year grace period before EMFAC2007 is required to be used for quantitative PM hot-spot analyses for project-level conformity determinations in California. This notice is applicable to current and future versions of the EMFAC model, unless EPA notes otherwise when approving the model for conformity purposes. This notice also announces the availability of a new guidance documents for completing quantitative PM hot-spot analyses using EMFAC and other models.
  Contact: Karina O’Connor, Region 9, at 775-833-1276 or oconnor.karina@epa.gov.
- Federal Register Notice of Availability: Official Release of EMFAC2007 Motor Vehicle Emission Factor Model for Use in the State of California | PDF version (4 pp, 112K). This notice describes EPA’s approval of the EMFAC2007 model for SIP and transportation conformity purposes in California. EPA’s approval of the model does not affect MOBILE model users in other states.
  Contacts: Karina O’Connor, Region 9, at 775-833-1276 or oconnor.karina@epa.gov.
Guidance on other models
- Federal Register Announcement of Availability: Official Release of January 2011 AP-42 Methods for Estimating Re-Entrained Road Dust from Paved Roads (PDF) (3 pp, 62K, February, 2011)
  This announcement describes EPA’s approval of the January 2011 AP-42 methods for use in SIPs and transportation conformity. A two-year grace period, which ends February 4, 2013, applies before the January 2011 AP-42 methods must be used for new regional emissions analyses for transportation conformity determinations. This document also supersedes the portions of the August 2007 guidance memo (next item, below) that cover estimating dust from paved roads.
  Contact: David Bizot at 734-214-4432 or bizot.david@epa.gov
- Policy Guidance on the Use of the November 1, 2006, Update to AP-42 for Re-entrained Road Dust for SIP Development and Transportation Conformity (PDF) (7 pp, 110K, EPA420-B-07-005, August, 2007)
  This guidance provides details about the changes made to the AP-42 methods for road dust and how and when to use them in PM2.5 state implementation plan development and transportation conformity determinations. This guidance supersedes the AP-42 portions of EPA’s February 24, 2004, guidance, which addressed both MOBILE6.2 and AP-42 (next item, below). Note that the portions of this guidance referring to paved road dust are no longer in effect, as they have been replaced by EPA’s Federal Register announcement of February 4, 2011, found immediately above.
- Policy Guidance on Use of MOBILE6.2 for SIP Development and Transportation Conformity (PDF) (13 pp, 672K)
  This memorandum describes how and when to use MOBILE6.2 in state implementation plan development and transportation conformity determinations. The time period requirements set forth in this policy document became effective upon publication of the May 19, 2004 Federal Register notice of availability that announced EPA’s approval of the new model for official purposes. Note that the AP-42 portions of this guidance are no longer in effect as they have been replaced by EPA’s August 2007 memo and February 2011 Federal Register announcement, both found immediately above.Federal Register Notice of Availability: Official Release of MOBILE6.2 Motor Vehicle Emissions Factor Model and the December 2003 AP-42 Methods for Re-Entrained Road Dust
  Contact: Gary Dolce at 734-214-4414 or dolce.gary@epa.gov
- Clarification of Question 5 of Policy Guidance for MOBILE6 SIPs in Mid-course Review Areas (PDF) (2 pp, 113K)
  This memorandum clarifies the approach for determining that attainment SIPs in mid-course review areas continue to demonstrate attainment with revised MOBILE6 inventories. The EPA memorandum was issued on February 12, 2003.
  Contact: Gary Dolce at 734-214-4414 or dolce.gary@epa.gov
- Policy Guidance on Use of MOBILE6 for SIP Development and Transportation Conformity (PDF) (14 pp, 105K)
  This memorandum describes how and when to use MOBILE6 in state implementation plan development and transportation conformity determinations. The time period requirements set forth in this policy document became effective upon publication of the January 29, 2002 Federal Register notice of availability that announced EPA’s approval of the new model for official purposes.January 29, 2002, Federal Register Notice of Availability: Official Release of the MOBILE6 Motor Vehicle Emissions Factor Model | PDF version (4 pages, 48K)
  Contact: Meg Patulski at 734-214-4842 or patulski.meg@epa.gov

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State Implementation Plans (SIPs) and Conformity

Implementation Guidance for the 2006 24-Hour Fine Particle (PM2.5) National Ambient Air Quality Standards (NAAQS)
This page provides guidance regarding the development of state implementation plans (SIPs) to demonstrate attainment with the 2006 24-hour PM2.5 NAAQS.

Guidance for Developing Transportation Conformity State Implementation Plans (PDF) (31 pp, 277K, EPA420-B-09-001, January 2009)
This document provides guidance on the statutory and regulatory requirements for states to develop conformity state implementation plans. This document supersedes the November 2004 Conformity SIP Guidance and Section 7 of the Interim Guidance for Implementing the Transportation Conformity Provisions in the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) (February 2006).
- Checklist for Developing a Conformity SIP (PDF) – Appendix A (6 pp, 115K)
- Editable Rule Model (DOC) – Appendix B (8 pp, 98K, free Word viewer )
Contact: Astrid Larsen at 734-214-4812 or larsen.astrid@epa.gov
Phase 2 8-hour Ozone Implementation Rule Provision for RFP Reductions Obtained From Outside a Nonattainment Area (PDF) (2 pp, 95K)
EPA issued a memorandum on October 11, 2007 stating that the Agency cannot approve 8-hour ozone reasonable further progress (RFP) state implementation plans (SIPs) that have obtained VOC or NOx reductions from outside an 8-hour nonattainment area. The memorandum also advises that motor vehicle emissions budgets cannot be found adequate if contained in these RFP SIPs. When EPA issued the memorandum, the U.S. Court of Appeals for the District of Columbia Circuit had not yet responded to EPA’s request for a partial remand and Plaintiff’s request for vacatur. On November 2, 2007, the Court issued an order that vacates and remands the portion of the Phase 2 8-hour implementation rule for which EPA had previously sought a voluntary partial remand. The October 11, 2007 memorandum remains applicable as it is consistent with the Court’s order.
Court Decision on the Phase 1 Ozone Implementation Rule
On June 8, 2007, the U.S. Court of Appeals for the District of Columbia Circuit responded to our petition for rehearing on the Court’s December 22, 2006, decision on the Phase 1 Rule to implement the 8-hour ozone national ambient air quality standard (NAAQS). To assist Regions, Federal, State, local agencies, and Tribes, amemo (PDF) (4 pp, 827K) was issued to the EPA regional offices on June 15, 2007. The memo summarizes the Court’s opinion, and its implications for transportation conformity and the June 15, 2007, due date for submission of state implementation plans for nonattainment areas.
Contact: Meg Patulski at 734-214-4842 or patulski.meg@epa.gov or
Rudy Kapichak at 734-214-4574 or kapichak.rudolph@epa.gov
Guidance for Creating Annual On-Road Mobile Source Emission Inventories for PM2.5 Nonattainment Areas for Use in SIPs and Conformity (PDF) (17 pp, 181K, EPA420-B-05-008, August 2005)
This guidance document describes how state and local agencies should prepare annual inventories for PM2.5 SIPs or regional conformity analyses. It provides a range of methods for producing those inventories and guidance on how to decide which method is most appropriate. For state and local agencies currently preparing a regional conformity analysis before a SIP is developed, this guidance provides the option of using a simpler inventory approach than what they might eventually use in the SIP. This document also addresses the possible use of the National Mobile Inventory Model (NMIM) in SIPs and conformity analyses.
Contact: Gary Dolce at 734-214-4414 or dolce.gary@epa.gov
Guidance for Determining the “Attainment Year” for Transportation Conformity in New 8-Hour Ozone and PM2.5 Nonattainment Areas (PDF) (12 pp, 144K, EPA420-B-05-002, March 2005)
This document provides guidance for 8-hour ozone and PM2.5 nonattainment areas in selecting attainment dates for use in transportation conformity determinations both before and after state implementation plans (SIPs) are submitted. This guidance also describes some flexibilities that are available to areas using interim emission or budget tests in choosing which years to perform a regional emissions analysis.
- July 1, 2004, Transportation Conformity Final Rule.
Contact: Rudy Kapichak at 734-214-4574 or kapichak.rudolph@epa.gov
2001 Limited Maintenance Plan for moderate PM10 (PDF) (11pp, 335K)
- Attachment A – Critical Design Value Estimation and Its Applications (PDF) (11pp, 294K)
1995 Limited Maintenance Plan for nonclassifiable CO Nonattainment Areas(PDF) (7pp, 1.3M)

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Quantifying Benefits of Control Measures in SIPs and Conformity

SmartWay SIP and Conformity Guidance (PDF) (35 pp, 306K, EPA420-B-07-004, June 2007)
This document describes how to quantify and use reductions in nitrogen oxides (NOx) that result when trucks are outfitted with two specific SmartWay fuel-efficient technologies: trailer aerodynamic kits and low-rolling resistant tires.
- Fact Sheet | PDF version (3 pp, 106K, EPA420-F-07-045, June 2007)
Contact: Laura Berry at 734-214-4858 or berry.laura@epa.gov or
Gary Dolce at 734-214-4414 or dolce.gary@epa.gov
Diesel Retrofits: Quantifying and Using Their Benefits in SIPs and Conformity – Guidance for State and Local Air and Transportation Agencies (PDF) (69 pp, 531K, EPA420-B-06-005, June 2006)
This document provides guidance on quantifying and using emission reductions from highway and nonroad diesel vehicles, engines, and equipment that have been retrofitted. The guidance discusses how emission reductions from diesel retrofit projects can be used in a SIP and in transportation conformity and general conformity determinations.
- Fact Sheet (PDF) (7 pp, 195K, EPA420-F-06-034, June 2006)
Contact: Meg Patulski at 734-214-4842 or patulski.meg@epa.gov or
Gary Dolce at 734-214-4414 or dolce.gary@epa.gov
Guidance for Quantifying and Using Emission Reductions from Best Workplaces for Commuter Programs in State Implementation Plans (SIPs) and Transportation Conformity Determinations
This guidance describes how to credit commuter benefit programs, such as EPA’s Best Workplaces for Commuters, in a SIP or transportation conformity determination. The guidance also includes instruction on using EPA’s 2005 COMMUTER Model (ZIP XLS, 13M), a tool for quantifying emissions and emission reductions associated with commuter benefit programs.
Contact: Meg Patulski at 734-214-4842 or patulski.meg@epa.gov
Guidance on Quantifying NOx Benefits for Cetane Improvement Programs for use in SIPs and Transportation Conformity (PDF) (32 pp, 253K, EPA420-B-04-005, June 2004)
This document, issued in June 2004, provides guidance on quantifying emission reductions from the use of cetane improvement additives in diesel fuel. These emission reductions may be used either to meet state implementation plan requirements such as reasonable further progress or attainment or in transportation conformity determinations.
Guidance for Quantifying and Using Long Duration Truck Idling Emission Reductions in State Implementation Plans and Transportation Conformity (PDF) (33 pp, 379K, EPA420-B-04-001, January 2004)
The January 2004 Long Duration Truck Idling Emission Reduction Guidance provides information on quantifying emission reductions from the use of technologies which reduce long duration truck idling emissions. These emission reductions may be used either to meet state implementation plan requirements such as reasonable further progress or attainment or in transportation conformity determinations.
Guidance for Quantifying and Using Long Duration Switch Yard Locomotive Idling Emission Reductions in State Implementation Plans(PDF) (24 pp, 399K, EPA-420-B-09-037, October 2009)
This document provides guidance to state air pollution control agencies and the general public on how control measures to reduce truck idling emissions may be used to meet SIP requirements.

Land Use and Conformity

Comparing Methodologies to Assess Transportation and Air Quality Impacts of Brownfields and Infill Development (PDF) (49 pp, 17K, EPA-231-R-01-001, August 2001)
This document describes four methods for characterizing the air quality benefits resulting from infill development, compares these methodologies, and examines their advantages and disadvantages. It also includes the June 7, 2001 guidance memo listed directly below.
Guidance on Applicable Methodologies to Account for the Benefits of Infill in SIPs and Conformity Determinations (PDF), June 7, 2001 (7 pp, 113K)
This memo guides the use of the four methods in preparing SIPs and transportation conformity determinations.
Contact: Laura Berry, OTAQ, at 734-214-4858 or berry.laura@epa.gov or
Mary Kay Santore, OPEI, at 202-260-8745 or santore.marykay@epa.gov
Final Policy Guidance: Improving Air Quality Through Land Use Activities. January 2001
This document discusses how to include land use activities in a SIP. It includes examples of land use activities and discusses requirements. (See Chapter 8 for conformity requirements and examples.)
- Announcement (PDF) (1p, 10K)
- Brochure: Improving Air Quality Through Land Use Activities (PDF) (4pp, 3M)
- Complete Report: Improving Air Quality Through Land Use Activities (PDF) (110 pp, 1.1M, EPA420-R-01-001, January 2001)
Contact: Laura Berry at 734-214-4858 or berry.laura@epa.gov

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March 2, 1999 Conformity Court Decision

(subsequently incorporated into July 2004 rulemaking)

EPA’s Conformity Guidance on Implementation of March 2, 1999, Conformity Court Decision (PDF) (11 pp, 46K, EPA420-F-99-025, May 1999)
This guidance includes details about using submitted budgets in conformity, EPA’s new adequacy review process, non-federal projects, SIP disapprovals, and certain safety margins consistent with the court decision. EPA released this guidance on May 14, 1999.
U.S. DOT’s Revised Guidance for the Implementation of March 2, 1999, Conformity Court Decision
This guidance document was released on January 2, 2002, and supersedes and replaces all previous FHWA and FTA guidance implementing the Court’s decision, including the supplemental guidance issued on June 18, 1999. It covers projects that can proceed during a conformity lapse.
Revised Guidance for Implementing the March 1999 Circuit Court Decision Affecting Transportation Conformity | PDF version (4 pp, 48K)
U.S. DOT’s February 7, 2002 Federal Register Notice announcing their revised guidance on projects that can proceed during a conformity lapse. This notice provides DOT’s rational and justification for revising the guidance.
May 20, 2003, FHWA/FTA Guidance: Clarification of Transportation Conformity Requirements for FHWA/FTA Projects Requiring Environmental Impact Statements (PDF) (2 pp, 107K)
April 9, 2003, FTA Guidance: Revised FTA Procedures for a conformity lapse (PDF) (2 pp, 2.3M) addresses funding and approval of FTA projects during a conformity lapse.
June 10, 1999, Federal Register Notice: Adequacy Status of Submitted State Implementation Plans for Transportation Conformity Purposes
Contact: Laura Voss Berry at 734-214-4858 or berry.laura@epa.gov

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