Policy & Guidance
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A variety of guidance documents pertaining to transportation conformity have been issued by FHWA, FTA, EPA, an doccasionally, jointly issued by these agencies. These documents cover a wide range of subject areas. Note that these guidance documents are not a substitute for any laws or regulations, thus do not impose legally binding requirements on EPA, DOT, states, or the regulated community. In addition, they may not apply to a particular situation based upon the circumstances. EPA and DOT retain the discretion to adopt approaches on a case-by-case basis that may differ from this guidance, but still comply with the statutes and SIP, conformity, and planning regulations.
- Transportation Conformity Guidance for 2012 PM2.5 Nonattainment Areas (EPA, November 2015) - Guidance for meeting transportation conformity requirements in areas designated nonattainment for the 2012 PM2.5 national ambient air quality standards.
- MOVES2014 Technical Guidance: Using MOVES to Prepare Emission Inventories for State Implementation Plans and Transportation Conformity (PDF) (EPA, January 2015) - This document provides guidance on appropriate input assumptions and sources of data for the use of MOVES2014 in SIP submissions and regional emissions analyses for transportation conformity purposes.
- Transportation Conformity Guidance for Areas Reaching the End of the Maintenance Period (PDF) (EPA, October 2014) - This guidance explains when transportation conformity requirements end for maintenance areas. This subject is relevant when areas approach the end of the 20 year maintenance period for certain national ambient air quality standards.
- Policy Guidance on the Use of MOVES2014 and Subsequent Minor Revisions for State Implementation Plan Development, Transportation Conformity, and Other Purposes (PDF) (EPA, July 2014) - This document describes how and when to use the MOVES2014 for SIP development, transportation conformity, general conformity, and other purposes.
- MOVES2014 Questions and Answers (PDF) (EPA, July 2014) This document highlights the differences between MOVES2014 and earlier versions of MOVES and explains EPA policy on using MOVES2014 in State Implementation Plans and Transportation Conformity Analyses.
- Diesel Retrofits: Quantifying and Using Their Emission Benefits in SIPs and Conformity - Guidance for State and Local Air and Transportation Agencies (EPA, February 2014) - Guidance on quantifying and using emission reductions from on-road and nonroad diesel vehicles, engines, and equipment that have been retrofitted with emission reduction technology. This guidance supersedes EPA's June 2006 guidance under the same name.
- Commuter Programs: Quantifying and Using Their Emission Benefits in SIPs and Conformity (EPA, February 2014) - Guidance on how to estimate the emission benefits of commuter programs and, under appropriate circumstances, take credit for them in SIPs and conformity determinations. This guidance supersedes EPA's October 2007 document, "Guidance for Quantifying and Using Emission Reductions from Best Workplaces for Commuter Programs in State Implementation Plans and Transportation Conformity".
- Carbon Monoxide Categorical Hot-Spot Finding (February 2014) - FHWA's carbon monoxide (CO) categorical hot-spot finding per the transportation conformity rule at 40 CFR 93.123(a)(3) for urban highway projects that include one or more intersections in CO maintenance areas, except in California. 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.
- Transportation Conformity Guidance for Quantitative Hot-spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas (EPA, November 2013) - 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. Update of November 2013: This guidance was originally released in December 2010, and Sections 5, 7.6, and 9.4 have been updated to reflect EMFAC2011 and EPA's 2012 PM NAAQS final rule. The November 2013 guidance supersedes the December 2010 guidance.
- Implementing the 2008 Ozone National Ambient Air Quality Standard (NAAQS): Frequently Asked Questions (May 2013) or (PDF - 128KB) - FAQs to address when conformity applies to the metropolitan transportation plan and TIP and at the project level; transitioning from the 1997 to 2008 8-hour ozone standard for areas nonattainment or maintenance for both; and how the planning process will be impacted by the transition to/from attainment.
- Federal Register Notice of Availability: Official Release of EMFAC2011 Motor Vehicle Emission Factor Model for Use in the State of California (March 2013) - In this notice, EPA is approving and announcing that EMFAC2011 is available to use in statewide California SIP development and for regional emissions analyses and CO, PM 10 and PM 2.5 hot-spot analyses for transportation conformity. EMFAC2011 must be used for all new regional emissions analyses and CO, PM 10 and PM 2.5 hot-spot analyses that are started on or after September 6, 2013.
- Program Guidance on High Occupancy Vehicle Lanes (or PDF) (November 2012) - FHWA guidance on the planning, design, operation, and management of HOV facilities, as well as examples to follow in evaluating proposed significant changes to the operation of an HOV lane (e.g., conversion of an HOV lane to an HOT lane)
- Guidance for Transportation Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas (EPA, July 2012) This document updates and supersedes EPA's 2004 "Multi-jurisdictional guidance." It 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. The revised guidance is consistent with the Transportation Conformity Restructuring Rule and applies to any current and future NAAQS, including the 2008 ozone NAAQS.
- Transportation Conformity Guidance for 2008 Ozone Nonattainment Areas (EPA, July 2012) - Guidance for meeting transportation conformity requirements in areas designated nonattainment for the 2008 ozone NAAQS and revocation of the 1997 ozone NAAQS for transportation conformity purposes.
- Frequently Asked Questions on the Transportation Conformity Lapse Grace Period (HTML) (May 2012) or (PDF - 73Kb) - FAQs to clarify the implementation of the transportation conformity lapse grace period.
- MOVES2010b Questions and Answers (PDF) (April 2012) - This document highlights the differences between MOVES2010b and earlier versions of MOVES and explains EPA policy on using MOVES2010b in State Implementation Plans and Transportation Conformity Analyses.
- Policy Guidance on the Use of MOVES2010 and Subsequent Minor Revisions for State Implementation Plan Development, Transportation Conformity, and Other Purposes (PDF) (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 (PDF) (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.
- PM2.5 Project-Level Conformity and Hot-Spot Analyses (July 2011)- FAQs about PM2.5 project-level conformity and hot-spot analyses
- Transportation and General Conformity Frequently Asked Questions (HTML)(April 2011) or (PDF - 40Kb) - FAQs regarding common questions and scenarios where the transportation and general conformity regulations may intersect for certain transportation projects and clarification on how the requirements can be met.
- Using the MOVES and EMFAC Emissions Models in NEPA Evaluations (EPA, February 2011) - This memo describes how EPA's emissions models MOVES and EMFAC can be incorporated into the NEPA process.
- Federal Register Announcing EPA's Official Release of the January, 2011, AP-42 Method for Estimating Re-entrained Road Dust from Paved Roads and the Start of a 2-year Grace Period for Regional Conformity Analyses. On February 4, 2011, EPA officially approved the latest revision of the method for estimating re-entrained road dust emissions from cars, trucks, buses, and motorcycles on paved roads in AP-42 for use in PM10 and PM2.5 SIPs and regional emissions analyses for transportation conformity determinations. The Federal Register also starts a 2-year grace period for the 2011 AP-42 method to be used for regional conformity emissions analyses in PM10 and PM2.5 nonattainment and maintenance areas. At the end of the grace period, (i.e., after February 4, 2013), 2011 AP-42 method is required to be used in regional conformity analyses in PM10 nonattainment and maintenance areas and any PM2.5 nonattainment and maintenance areas where EPA regional administrator or the state air quality agency determined that re-entrained road dust is a significant contributor to the area's PM2.5 problem, or if the area has a PM2.5 motor vehicle emissions budget that includes re-entrained road dust.
- Using MOVES in Project-Level Carbon Monoxide Analyses (EPA, December 2010) - This guidance describes how to use the MOVES emissions model to estimate CO emissions from transportation projects, including roadway intersections, highways, transit projects, parking lots and intermodal terminals.
- 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 (December 2010) - This notice approves MOVES2010a for PM and CO hot-spot analyses (and EMFAC2007 for PM hot-spot analyses in California) with a 2-year conformity grace period. EPA also announced the availability of its final PM hot-spot guidance and CO project-level MOVES guidance.
- Federal Register Notice of Availability: Official Release of MOVES2010 Motor Vehicle Emissions Model for Emissions Inventories in SIPs and Transportation Conformity (March 2010) - 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.
- MOVES2010 Mobile Source Emissions Model: Questions and Answers (PDF) (December 2009) - This document describes the model and provides general information for model use.
- Clarification to the "Transportation Conformity Guidance for Qualitative Hot-spot Analysis in PM2.5 and PM10 Nonattainment and Maintenance Areas" (June 2009)
- Guidance for Implementing the Clean Air Act Section 176(c)(8) Transportation Control Measure Substitution and Addition Provision (January 2009) - EPA guidance on implementing the CAA 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 CAA amendments made by SAFETEA-LU that addressed this provision.
- Guidance for Developing Transportation Conformity State Implementation Plans (January 2009) - EPA guidance on the statutory and regulatory requirements for states to develop conformity SIPs. 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).
- Guidance for the Use of Latest Planning Assumptions in Transportation Conformity Determinations (or PDF, 308 KB) (December 2008) - Joint USDOT and EPA guidance to clarify expectations for implementing the transportation conformity rule's latest planning assumptions requirements
- Area Designations for the Revised 24-hour Fine Particle National Ambient Air Quality Standard (June 2007) - EPA guidance on the timeline for designating areas for the purpose of implementing the revised PM2.5 NAAQS
- SmartWay SIP and Transportation Conformity Guidance: Accounting for NOx Reductions from Trailer Aerodynamic Kits and Low Rolling Resistance Tires (June 2007) - EPA guidance that 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 resistance tires
- Transportation Conformity and the Revised 24-hour PM2.5 Standard (April 2007) - EPA guidance that addresses how transportation conformity will be implemented under the revised 24-hour PM2.5 standard
- Court Decision on Transportation Conformity Rule (October 2006) - The U.S. Court of Appeals vacated a provision of the Transportation Conformity Rule (40 CFR 93.109(e)(2)(v)), a provision that allowed areas to use the interim emissions tests instead of the 1-hour budgets where the interim tests could be shown to be more appropriate for ensuring that the plan, TIP, or project would not create new violations, worsen existing violations, or delay timely attainment of the 8-hour standard, as determined through interagency consultation.
- Transportation Conformity Guidance for Qualitative Hot-Spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas (March 2006) - Memorandum from FHWA and EPA on how to perform qualitative hot-spot analyses in PM2.5 and PM10 nonattainment and maintenance areas, as required by the March 10, 2006, final transportation conformity rule.
- Transportation Conformity Alert to FHWA Divisions on PM2.5 Project-Level Conformity (November 2005) - Alert to FHWA Divisions concerning PM2.5 Project-Level Conformity requirements as of April 5, 2006.
- Guidance on Incorporating Bundled Measures in a State Implementation Plan (August 2005) - EPA guidance on SIP credit from a group ("bundle") of pollution control measures or strategies considered in the aggregate
- Guidance for Creating Annual On-Road Mobile Source Emission Inventories for PM2.5 Nonattainment Areas for Use in SIPs and Conformity (August 2005) - EPA guidance on preparation of annual inventories for PM2.5 SIPs or regional conformity analyses by state and local agencies. It also addresses the possible use of the National Mobile Inventory Model (NMIM) in SIPs and conformity analyses.
- Guidance for Determining the "Attainment Years" for Transportation Conformity in New 8-Hour Ozone and PM2.5 Nonattainment Areas (March 2005) - EPA guidance for 8-hour ozone and PM2.5 nonattainment areas in selecting attainment dates for use in transportation conformity determinations both before and after SIPs are submitted. It 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.
- Conformity Information to Inform PM-2.5 Designations (October 2004) - EPA guidance on the transportation conformity burden associated with designating areas for the PM2.5 air quality standard.
- Guidance on Quantifying NOx Benefits for Cetane Improvement Programs for Use in SIPs and Transportation Conformity (June 2004) - EPA guidance quantifying emission reductions from the use of cetane improvement additives in diesel fuel. These emission reductions may be used either to meet SIP requirements or in transportation conformity determinations.
- Guidance for Quantifying and Using Long Duration Truck Idling Emission Reductions in State Implementation Plans and Transportation Conformity (January 2004) - EPA guidance on quantifying and using long duration truck idling emission control programs in SIPs and transportation conformity
- Clarification of Transportation Conformity Requirements for FHWA/FTA Projects Requiring Environmental Impact Statements (May 2003) - Memorandum from FHWA and FTA to clarify how full compliance with the CAA transportation conformity requirements is to be achieved for FHWA and FTA projects requiring an EIS under the National Environmental Policy Act, especially regarding whether conformity of a project must be determined prior to approval of the final EIS or prior to the issusance of the record of decision.
- Revised FTA Procedures for a Conformity Lapse (April 2003) - Memorandum from FTA clarifying project development procedures for New Starts projects in the event of a conformity lapse.
- Designations for the Fine Particle National Ambient Air Quality Standards (April 2003) - EPA guidance on the process for designating areas for the purpose of implementing the PM2.5 NAAQS
- Guidance on the Implementation of the March 2, 1999 Court Decision (January 2002) - Updated guidance from FHWA and FTA concerning approval for projects in nonattainment and maintenance areas that do not have a currently conforming transportation plan and transportation improvement program. Changes resulted from a case brought against EPA by the Environmental Defense Fund.
- Information: Limited Maintenance Plans (September 2001) - Memorandum from EPA detailing instances when moderate PM10 nonattinment areas can be redesignated to attainment with a streamlined maintenance plan.
- Guidance on Applicable Methodologies to Account for the Benefits of Infill in SIPs and Conformity Determinations (June 2001) - EPA guidance on four methodologies to quantify the air quality benefits associated with infill development
- Improving Air Quality Through Land Use Activities (January 2001) - EPA guidance on accounting for the air quality impacts of voluntary land use policies and projects
- Memorandum of Understanding between DOT and EPA on Transportation Conformity (April 2000) - MOU between DOT and EPA to provide for timely review and comment on transportation and air quality planning documents and to establish a framework for resolving outstanding issues to facilitate timely conformity decisions.
Archived Guidance
Superseded Guidance
