Structure of This Guide
Background of Transportation Conformity
History of Transportation Conformity
Statutory Requirements for Transportation Conformity
NAAQS and Nonattainment Areas
Early Action Compact (EAC) Areas
Exhibit l-1: Summary of Transportation Conformity Requirements Inception to Date
Exhibit l-2: National Ambient Air Quality Standards for Key Transportation-Related Pollutants
Exhibit l-3: NAAQS Classification & Requirements for Meeting 1-Hour Ozone Standard
Exhibit l-4: NAAQS Classification & Requirements for Meeting 8-Hour Ozone Standard
Exhibit l-5: NAAQS Classifications & Requirements for Carbon Monoxide
Exhibit l-6: NAAQS Classifications & Requirements for PM10
Exhibit l-7: NAAQS Classifications & Requirements for PM2.5
Exhibit l-8: Early Action Compact Milestones
This transportation conformity reference guide (the Guide) was prepared by the Federal Highway Administration (FHWA), in cooperation with the Federal Transit Administration (FTA) and the Environmental Protection Agency (EPA), as a tool to facilitate compliance by State and local agencies with the transportation conformity requirements. FHWA has designed this Guide so that it can be updated periodically to include new information, guidance, case studies, research findings, or approaches to meeting requirements (e.g. new NAAQS). This Guide is not a "cookbook" on how to work through the transportation conformity process; it does not provide detailed technical modeling guidance and does not prescribe how to make a conformity determination. Rather, it is a reference manual which contains the transportation conformity rule and relevant preamble language, questions and answers, and lists of resource materials. The information is organized according to the requirements, which apply, to all nonattainment and maintenance areas at all times followed by specific requirements for specific pollutants and designations. The Guide is designed to be useful to both seasoned practitioners and newcomers to the transportation conformity process. All relevant materials and information needed for agencies to fully understand transportation conformity are assembled in this Guide in an accessible and easy to read format. The need for this Guide stems from the requirement to integrate transportation and air quality planning which is included in the Clean Air Act Amendments (CAA) of 1990, the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991, the Transportation Equity Act for the 21st Century (TEA-21), and the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for User (SAFETEA-LU). 
The Guide has been updated to reflect the statutory changes made to the transportation planning and conformity processes as a result of SAFETEA-LU. The Guide does not include any interim guidance released since the passage of SAFETEA-LU. Please see the interim guidance on the planning provisions at: www.fhwa.dot.gov/planning/ and the interim guidance on the conformity provision at: www.fhwa.dot.gov/environment/conformity/sec6011guidmemo.htm for further information about how to implement SAFETEA-LU before the regulations are revised.
At the conclusions of publishing this version of the Guide on the internet, EPA issued PM2.5 and revised PM10 hot spot analyses regulations. The Guide does not include the changes made to the conformity rule as a result of the March 2006 regulations.
This Guide does not replace law, regulation, guidance, or requirements. In the case of any discrepancies or differences found between the EPA transportation conformity rule and this Guide, readers should defer to the specific language and requirements included in the transportation conformity rule and subsequent guidance issued by the U.S. Department of Transportation (DOT) and EPA.
The Guide is organized in four major Parts:
Part I summarizes the purpose and need for the Guide and provides a brief explanation of the CAA and ISTEA/TEA-21/SAFETEA-LU statutory requirements. Part II explains how the Guide is organized and how to most effectively use the Guide to find information on specific topics or areas of interest. Part III, transportation conformity requirements, is the major part of this Guide and presents the most current information on requirements. Part III includes references to relevant CAA and ISTEA/TEA-21/SAFETEA-LU statutory requirements, EPA's transportation conformity rule (i.e. regulatory requirements) and relevant preamble language that helps explain the rule, and DOT and EPA guidance. In addition, real world examples and practices are used in order to help readers understand the complex relationship between the elements of the transportation and air quality planning processes, and the requirements of the transportation conformity rule. Each section of Part III is self-contained. However, readers may need to refer to more than one section within Part III to understand the complete relationships and interactions within the process. Part IV provides a discussion of emerging issues that will impact transportation conformity in the near future.
As further assistance to the reader, this Guide includes examples from nonattainment and maintenance areas to show how some areas have complied with specific elements of the rule. For example, some areas use sample checklists to show that all of the conformity requirements are being addressed. We have included these in the appendices along with EPA and DOT informational materials and guidance on transportation conformity and related issues. The bibliography includes reference materials for those seeking additional information on a specific subject and a glossary is included in the back of the Guide.
The concept of coordinating the transportation and air quality planning processes and ensuring that transportation plans and Transportation Improvement Programs (TIPs) are consistent with State Implementation Plans (SIPs) began with the Clean Air Act Amendments of 1977. The most recent update to these requirements was included in the Clean Air Act Amendments (CAA) of 1990. Exhibit l-1 summarizes the transportation conformity requirements from their inception to date and illustrates how the requirements have evolved over the past twenty years. The Exhibit also summarizes the amendments to the transportation conformity rule since 1993.
In order to receive transportation funding or approvals from the FHWA/FTA, State and local transportation agencies with plans, programs or projects in nonattainment or maintenance areas, must demonstrate that they meet the transportation conformity requirements of the CAA as set in the transportation conformity rule. In addition, the ISTEA/TEA-21 (and now SAFETEA-LU), sets forth metropolitan planning provisions that reinforce and complement the CAA conformity provisions. To meet the requirements, Metropolitan Planning Organizations (MPOs) must explicitly show that the anticipated emissions resulting from implementation of transportation plans, programs and projects are consistent with and conform to the purpose of the SIP for air quality. Following the amendment to the CAA in 1990, EPA issued transportation conformity regulations in 1993.
In August 1997 a revised transportation conformity rule was issued in an effort to streamline the transportation conformity process and was based in part, on experience gained since 1993 by Federal, State, and local area transportation and air quality agencies.
On March 2, 1999 the U.S. Court of Appeals for the D.C. Circuit issued a decision which affected several provisions of the 1997 conformity rule, including the use of submitted budgets, the advancement of grandfathered and non-federal projects during a conformity lapse, and the 120-day grace period after SIP disapprovals. DOT and EPA issued guidance to implement the Court decision.
On July 1, 2004, EPA amended the transportation conformity regulations to include criteria and procedures for the new 8-hour ozone and PM2.5 National Ambient Air Quality Standards (NAAQS). The rule also incorporated existing guidance issued by EPA and the Department of Transportation that implemented the March 2, 1999, court decision, and included a few miscellaneous revisions to clarify the existing regulation and improve implementation.
On August 10, 2005, the President signed SAFETEA-LU into law. SAFETEA-LU revised a number of aspects of the Clean Air Act's transportation conformity provisions including:
|Milestone in Conformity History||Key Provisions|
|Federal Aid Highway Act of 1970||§109(j) provides that "The Secretary, after consultation with the Administrator of the Environmental Protection Agency, shall develop and promulgate guidelines to assure that highways constructed pursuant to this title are consistent with any approved plan for the implementation of any ambient air quality standard for any air quality control region designated pursuant to the Clean Air Act, as amended."|
|Clean Air Act Amendments of 1977 (Pub. L. 95-95)||The assurance of conformity was an affirmative responsibility of the head of each Federal agency and no Metropolitan Planning Organization (MPO) could approve any transportation plan, program, or project that did not conform to a State or Federal Implementation Plan. Specifically, the 1977 CAA stated: "No Federal department shall 1) engage in, 2) support in any way or provide financial assistance for, 3) license or permit, or 4) approve any activity which does not conform to a (State Implementation Plan) after it has been approved or promulgated."|
|June, 1978-Memorandum of Understanding||The FHWA and Urban Mass Transportation Administration (now FTA), Memorandum of Understanding provided EPA an opportunity to jointly review and comment on the conformity of transportation plans and programs and provided transportation officials the opportunity to review and comment on State Implementation Plans.|
|June, 1980-EPA and DOT jointly issued "Procedures for Conformance of Transportation Plans, Programs, and Projects with CAA State Implementation Plans"||The guidance required that certifications be made that transportation planning had been conducted according to a continuous, cooperative, and comprehensive planning (3-C) process and consistent with Clean Air Act requirements. Transportation plans and programs were considered to conform with the SIP if they did not adversely affect the transportation control measures (TCMs) in the SIP, and if they contributed to reasonable further progress in implementing those TCMs. Transportation projects would conform if it were a TCM from the SIP, came from a conforming TIP, or did not adversely affect the TCMs in the SIP.|
|Jan., 1981-DOT Interim Final Rule (46 FR 8426, Jan. 26, 1981)||This rule built upon the 1980 joint guidance, and interpreted conformity in the context of agencies implementing agreed upon transportation control measures (TCMs). Compliance with the conformity requirements was to be demonstrated as part of the transportation planning and National Environmental Policy Act (NEPA) processes.|
|Nov., 1990-Clean Air Act Amendments (CAA) of 1990 [CAA §176 (c)(1), 42 U.S.C. §7506 (c)(1)]||The scope and content of transportation conformity provisions were expanded to require the reconciliation of the emissions impacts of transportation plans, programs, and projects with the SIP. Specifically, transportation plans, programs, and projects must conform to the purpose of the SIP. This integration of transportation and air quality planning is intended to ensure that transportation plans, programs, and projects will not: "(i) cause or contribute to any new violation of any standard in any area; (ii) increase the frequency or severity of any existing violation of any standard in any area; or (iii) delay timely attainment of any standard or any required interim emissions reductions or other milestones in any area."|
|June, 1991- Interim Guidance for Determining Conformity of Transportation Plans, Programs, and Projects, June 7, 1991||The Interim guidance was based upon §176(c)(3) of the CAA and provided that, until the conformity SIP revision was approved, conformity of transportation plans, programs, and projects would be demonstrated if plans and programs: 1) were consistent with the most recent estimates of mobile source emissions; 2) provide for the expeditious implementation of transportation control measures in the applicable SIP; 3) with respect to ozone and carbon monoxide nonattainment areas, contribute to annual emissions reductions consistent with sections 182(b)(1) and 187(a)(7); 4) transportation projects must come from a conforming transportation plan and program; and 5) in carbon monoxide nonattainment areas, such projects must eliminate or reduce the severity and number of violations of the CO standards in the area substantially affected by the project.|
|Nov., 1993-Transportation Conformity Rule
(40 CFR Parts 51 and 93), 58 FR 62188, November 24, 1993
|Required by the 1990 CAA, this rule established the criteria and procedures by which FHWA, the FTA, and MPOs determine the conformity of Federally funded or approved highway and transit plans, programs, and projects to SIPs|
|Aug., 1995-Transportation Conformity Rule Amendments
(40 CFR Parts 51 and 93), 60 FR 40098, August 7, 1995
|These amendments aligned the dates of conformity lapses due to SIP failures with the application of Clean Air Act highway sanctions for certain ozone areas and all areas with disapproved SIPs with a protective finding.|
|Nov., 1995- Transportation Conformity Rule Amendments
(40 CFR Parts 51 and 93), 60 FR 57179, November 14, 1995
|These amendments: 1) aligned the date of conformity lapses with the date of application of Clean Air Act highways sanctions for any failure to submit or submission of an incomplete control strategy SIP; 2) extended the grace period before which areas must determine conformity to a submitted control strategy SIP; 3) established a grace period before which transportation plan and program conformity must be determined in newly designated nonattainment areas (the District of Columbia Circuit Court found the grace period to be invalid, but it was later restored by Congress); and 4) changed the nitrogen oxides (NOx) provisions of the transportation conformity rule to be consistent with the (NOx)requirements of the Clean Air Act and previous commitments made by EPA. These amendments also allowed any TCM from an approved SIP to proceed during a conformity lapse, with the expectation that TCMs would be coordinated through the transportation planning process, as required by 23 CFR Part 450 and 49 CFR Part 613, ISTEA's State and Metropolitan Planning Regulations|
|Aug., 1997-Transportation Conformity Rule Amendments
(40 CFR Parts 51 and 93), 62 FR 43780, August 15, 1997
|The revised transportation conformity rule: 1) streamlines and clarifies regulatory text; 2) eliminates the build/no-build test when SIP budgets have been submitted; 3) provides more flexibility even where there are no submitted SIP budgets; 4) allows for previously planned non-Federal projects to go forward when there is no currently conforming transportation plan/TIP (the Court found this provision invalid and it no longer applies); 5) limits network-based modeling requirements to large, urban areas; 6) provides rural areas the flexibility to choose among several conformity tests; 7) streamlines and clarifies modeling requirements; and 8) makes consequences of an EPA SIP disapproval without a protective finding less severe (the Court found this provision invalid and it no longer applies).|
|March 2, 1999- U. S. Court of Appeals for the District of Columbia Circuit, decision on transportation conformity rule||The decision affected five conformity provisions: 1) a provision allowing grandfathered projects (previously conformed projects) to proceed during a conformity lapse once the NEPA process is completed; 2) a provision allowing certain regionally significant non-federal projects to proceed during a conformity lapse; 3) a provision allowing conformity findings based on submitted budgets, prior to EPA approval action; 4) a provision allowing a conformity grace period for 120 days after EPA disapproval of a SIP without a protective finding; and, 5) a provision allowing certain safety margins to be used prior to EPA approval.|
|May 14, 1999-EPA Conformity Guidance on Implementation of March 2, 1999 Conformity Court Decision||The guidance provides information and questions and answers on EPA's new adequacy process for submitted budgets. The guidance also included information about projects requiring federal approval, SIP disapprovals, non-federal projects, and certain safety margins.|
|April 10, 2000- Environmental Protection Agency-Transportation Conformity Rule Amendment: Deletion of Grace Period(40 CFR Part 93), 65 FR 18911, April 10, 2000||This amendment deleted a provision in the transportation conformity rule (§93.102(d) which allowed new nonattainment areas a one-year grace period before conformity began applying. The U.S. Court of Appeals for the District of Columbia overturned the grace period provision in November 1997 and EPA was required by a court settlement with Environmental Defense Fund to finalize rulemaking on this issues and delete the grace period by March 31, 2000.|
|January 2, 2002 - Federal Highway Administration and Federal Transit Administration- Revised Guidance for Implementing the March 1999 Circuit Court Decision Affecting Transportation Conformity||This joint FHWA/FTA guidance supercedes previous guidance that was issued in response to the Court decision. It provides guidance on what projects can proceed during a conformity lapse, and what actions FHWA, FTA, and EPA should take in anticipation of an expected conformity lapse.|
|August 6, 2002- Environmental Protection Agency- Transportation Conformity Rule Amendments: Minor Revision of 18-Month Requirement for Initial SIP Submissions and Addition of Grace Period for Newly Designated Nonattainment Areas (40 CFR Parts 93), 67 FR 50808, August 6, 2002||These amendments implemented a Clean Air Act amendment restoring a one-year grace period before conformity is required in areas that are designated nonattainment for a given air quality standard for the first time, and they changed the point by which a conformity determination must be made following a State's submission of a control strategy implementation plan or maintenance plan for the first time (an ``initial'' SIP submission). The amended rule requires conformity to be determined within 18 months of EPA's affirmative finding that the SIP's motor vehicle emissions budgets are adequate.|
|April 30, 2004 - Environmental Protection Agency - 8-Hour Ozone National Ambient Air Quality Standards; Final Rules (40 CFR Parts 50, 51 and 81), 69 FR 23858, April 30, 2004||This rule designates and classifies all areas in the United States that are nonattainment for the 8-hour ozone National Ambient Air Quality Standard (NAAQS). Moreover, this rule also addresses Early Action Compact (EAC) areas and the milestones that these areas must meet in order to defer the effective date of nonattainment designation for the 8-hour ozone standard.|
|July 1, 2004 - Environmental Protection Agency - Transportation Conformity Rule Amendments for the New 8-Hour Ozone and PM2.5 National Ambient Air Quality Standards and Miscellaneous Revisions for Existing Areas; Transportation Conformity Rule Amendments: Response to Court Decisions and Additional Rule Changes; Final Rule (40 CFR Part 93), 69 FR 40004, July 1, 2004||The final rule amends the transportation conformity regulations to include criteria and procedures for the new 8-hour ozone and fine particulate matter (PM2.5) national ambient air quality standards (NAAQS). Specifically, the rule describes the general requirements for conducting conformity determinations for the new NAAQS, such as the conformity test(s) that apply in new standard areas. In addition, the rule includes PM2.5 as a criteria pollutant subject to transportation conformity and outlines the specific conformity requirements that would apply in PM2.5 nonattainment areas. The rule also incorporates existing guidance issued by EPA and the Department of Transportation that implements the March 2, 1999, court decision. Finally, the rule also includes a few miscellaneous revisions to clarify the existing regulation and improve implementation. Of particular interest are the streamlining of the number of triggers that require a new conformity determination and allowing transportation planners to base regional emission analyses on assumptions available at the time the conformity analysis begins.|
|July 21, 2004 - Environmental Protection Agency - 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 clarifies how conformity determinations and the regional emissions analyses are completed in existing and new nonattainment and maintenance areas, particularly those where multiple agencies or states are involved. The guidance provides examples and interpretations for generic scenarios that are present in the field and that are expected to occur under the new standards. It expands on the final rule by including additional detail, examples, and pictorial representations.|
|January 5, 2005 - Environmental Protection Agency - Air Quality Designations and Classifications for the Fine Particles (PM2.5) National Ambient Air Quality Standards; Final Rule (40 CFR Part 81), 70 FR 944, January 5, 2005||This rule sets forth the initial air quality designations and classifications for all areas in the United States, including Indian country, for the fine particles (PM2.5) National Ambient Air Quality Standards (NAAQS).|
|May 6, 2005 - Environmental Protection Agency - Transportation Conformity Rule Amendments for the New PM2.5 National Ambient Air Quality Standard: PM2.5 Precursors; Final rule(40 CFR Part 93), 70 FR 24280, May 6, 2005||This final rule adds the following transportation-related PM2.5 precursors to the transportation conformity regulations; nitrogen oxides (NOx), volatile organic compounds (VOCs), sulfur oxides (SOx), and ammonia (NH3). The final rule specifies when each of these precursors must be considered in conformity determinations in PM2.5 nonattainment and maintenance areas before and after PM2.5 state air quality implementation plans (SIPs) are submitted.|
|August 10, 2005 - The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) was enacted (PL-109-59)||SAFETEA-LU revised a number of aspects of the Clean Air Act's section 176(c) transportation conformity provisions including: providing an additional six months to re-determine conformity after new motor vehicle emissions budgets are either found adequate or approved; changing the frequency requirements for transportation conformity determinations; providing an option for reducing the time period covered by conformity determinations; adding a one-year grace period for conformity lapses; changing requirements for conformity SIPs; and providing procedures for areas to use in substituting or adding transportation control measures (TCMs) to approved state implementation plans (SIPs).|
|*November 29, 2005 - Environmental Protection Agency - Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard - Phase 2; Final Rule to Implement Certain Aspects of the 1990 Amendments Relating to New Source Review and Prevention of Significant Deterioration as They Apply in Carbon Monoxide, Particulate Matter and Ozone NAAQS; Final Rule for Reformulated Gasoline; Final Rule (40 CFR Parts 51, 52, and 80), 70 FR 71612, November 29, 2005||The final rule takes action on most of the remaining elements of the program to implement the 8-hour ozone NAAQS. The rule addresses: reasonably available control technology and measures (RACT and RACM), reasonable further progress (RFP), modeling and attainment demonstrations, and new source review. The rule was issued so that States and Tribes will know how these statutory controls and planning obligations apply and when State implementation plan (SIP) revisions are due for these obligations. The rule also finalizes several revisions to the regulations governing the nonattainment NSR programs. It also addresses what effect the transition to the 8-hour standard will have on certain aspects of the Reformulated Gasoline program.|
* The reference guide has not been updated to reflect the contents of the Phase 2: 8-hour Ozone Implementation Rule. This rule will become effective on January 30, 2006.
The 1990 CAA prohibits any Federal agency from supporting activities that do not conform to the applicable SIP or Federal Implementation Plan (FIP). Specifically, the CAA prohibits Metropolitan Planning Organizations (MPOs) from approving transportation plans, projects or programs that do not conform to a SIP. Detailed information on SIPs can be found in Part III, Section B of this Reference Guide.
42 U.S.C. §7506(c) (§176(c)(1) of the CAA) reads:
No department, agency, or instrumentality of the Federal Government shall engage in, support in any way or provide financial assistance for, license or permit, or approve, any activity which does not conform to an implementation plan after it has been approved or promulgated under section 7410 of this title. No metropolitan planning organization designated under section 134 of title 23, United States Code, shall give its approval to any project, program, or plan which does not conform to an implementation plan approved or promulgated under section 7410 of this title. The assurance of conformity to such an implementation plan shall be an affirmative responsibility of the head of such department, agency, or instrumentality. Conformity to an implementation plan means-
The determination of conformity shall be based on the most recent estimates of emissions, and such estimates shall be determined from the most recent population, employment, travel and congestion estimates as determined by the metropolitan planning organization or other agency authorized to make such estimates.
(Note: The full text of 42 U.S.C. §7506 is included in Appendix A.)
In short, transportation conformity is a way to,
Taken together with the planning provisions of the ISTEA and SAFETEA-LU, transportation conformity is intended to ensure that integrated transportation and air quality planning occurs in areas designated by EPA as nonattainment or maintenance areas. Together, these provisions require that it be demonstrated that transportation plans, programs, and projects funded or approved by FHWA and/or FTA funds conform to the SIP's purpose, which is to meet the National Ambient Air Quality Standards (NAAQS). The transportation conformity process integrates transportation and air quality planning by requiring that transportation plans, programs, and projects verify that the expected emissions resulting from their implementation are consistent with and conform to the purpose of the SIP.
The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. Currently, EPA has set standards to six principal pollutants, which are called "criteria" pollutants, including carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone, and sulfur dioxides. The Federal standards developed by EPA set allowable concentrations and exposure limits for the various pollutants. Title I of the CAA establishes criteria for attaining and maintaining the NAAQS.
A nonattainment area is a geographic region that EPA has designated pursuant to the CAA as not meeting the NAAQS for any pollutant for which a standard exists. Subsequent to the passage of the CAA, EPA released the nonattainment classifications and exposure limits for transportation-related pollutants. Exhibit l-2 below shows the standards for the key transportation-related pollutants. The standard for nitrogen dioxide (NO2) is not listed because Los Angeles is the only NO2 maintenance area in the United States and there are no NO2 nonattainment areas. Transportation conformity only applies to ozone, carbon monoxide, particulate matter (PM10 and PM2.5), and NO2 nonattainment and maintenance areas.
Officials in each nonattainment area must take specified actions within a specified time frame to reduce emissions and attain the NAAQS. The CAA discusses the specific, detailed planning requirements for nonattainment areas based on designation status. The actions become more stringent and numerous as the air quality problem gets worse. This is discussed more fully in Section B and Section C - Chapter 4 of this Guide. Exhibits l-3 through l-7 show the NAAQS classifications, requirements and attainment dates for 1-hour ozone, 8-hour ozone, carbon monoxide, PM10, and PM2.5 nonattainment areas, respectively.
|Pollutant||Primary Standards||Averaging Time|
|Carbon Monoxide (CO)|| 10 µg/m3 (9 ppm)
40 µg/m3 (35 ppm)
| 8-hour (with one exceedance / year)
1-hour (with one exceedance / year)
|Ozone (O3)|| 235 µg/m3 (0.12 ppm)
156 μg/m3 (0.08 ppm)
| 1-hour Average
| 15 µg/m3
| Annual Average
|Particulate Matter **
| 50 µg/m3
| Annual (Arithmetic Mean)
*PM2.5 is fine particulate matter of 2.5 microns or smaller.
**PM10 is particulate matter 10 microns or smaller.
A maintenance area is any geographic region of the United States previously designated nonattainment pursuant to the CAA, and subsequently redesignated to attainment. Transportation conformity requirements also apply to maintenance areas. In addition, if a nonattainment area pursues redesignation under the CAA, the area is required to develop a maintenance plan that is a revision to the SIP that provides for the maintenance of the NAAQS for the applicable pollutant. The maintenance plan must cover at least the 10-year period of time after EPA approves a State's request for redesignation to attainment pursuant to CAA §107(d). Eight years after redesignation as a maintenance area, each State must submit to EPA a revised maintenance plan for the 10-year period subsequent to the expiration of the first 10-year period. Therefore, the maintenance period would cover a 20-year period after an area's redesignation and the conformity requirements would apply for the entire period.
Since the adoption of the CAA, the air quality in many areas has improved and some areas have been redesignated from nonattainment to maintenance areas. For a current listing of nonattainment and maintenance areas see www.epa.gov/oar/oaqps/greenbk/index.html
|Classification||1-hour Concentration(ppm)||Attainment Date||Requirements/Actions|
|Marginal||0.121 to 0.138||11/15/93|| Existing SIP Commitment-Implement current commitments; correct SIP deficiencies
Basic Inspection and Maintenance Program (I/M)-Basic I/M Program should be revised to meet the requirements in the SIP, or EPA guidance, whichever is more stringent, if such a program were required before enactment of the CAA
|Moderate||0.138 to 0.160||11/15/96|| Basic Inspection & Maintenance Program-The SIP is required to be revised to include a basic I/M program, regardless of whether such a Program was required before the CAA
Stage II Vapor Recovery Program-Submit a Stage II Vapor Recovery Program by November 15, 1992, that is designed to reduce emissions from refueling at retail fuel outlets for facilities that sell more than 10,000 gallons per month (50,000 gallons per month for small businesses)
Contingency Measures-Contingency provisions, which may include transportation control measures (TCMs), must be provided for in the 1993 SIP submittal. TCMs are directed toward reducing emissions by improving traffic flow, reducing congestion, or reducing vehicle use. Contingency measures will take effect without further action by the State or the EPA at any point the State fails to meet the 15 percent emissions reduction targets required by 1996, fails to attain the NAAQS target date, or, in the case of areas designated serious and above, fails to meet the 3-percent annual emissions reductions required after 1996
|Serious||0.160 to 0.180||11/15/99|| Enhanced Inspection and Maintenance Program-Submit an enhanced I/M Program by November 15, 1992, that meets all of EPA's requirements for enhanced I/M. The National Highway System Act of 1995 prohibits EPA from requiring adoption or implementation by a State of a test-only I/M240 enhanced vehicle inspection and maintenance program as a means of compliance with section 182 or 187 of the CAA, but the EPA may approve such a program if a State chooses to adopt the program as a means of compliance with such section.
Clean Fuel Fleet Program-Areas with a 1980 population of 250,000 or more must revise the SIP by May 15, 1994, to contain a clean-fuel vehicle program for centrally fueled fleets of 10 or more vehicles. The SIP must include programs to ensure the effectiveness of the clean-fuel fleet program
0.180 to 0.190
0.190 to 0.280
| Vehicle Miles Traveled (VMT) Limitations-Vehicle miles traveled is the sum of distances traveled by all motor vehicles in a specified region. Submit specific transportation control strategies and measures by November 15, 1992, for implementation to offset growth in emissions from growth in VMT or number of trips. VMT offset SIPs do not establish motor vehicle emissions budgets for conformity determinations.
Reformulated Gasoline-In 1995, reformulated gasoline was mandated in the worst nine ozone areas: Baltimore, Chicago, Hartford (CT), Houston, Los Angeles, Milwaukee, New York City, Philadelphia, and San Diego. In accordance with a January 4, 2000 Court ruling, only moderate and above nonattainment areas may "opt-in" to the reformulated gasoline program.
|Extreme||0.280 and above||11/15/10||Measures for Heavy-duty Vehicles-Extreme areas may submit additional measures to reduce the use of high-polluting or heavy-duty vehicles during peak traffic hours|
Source: Transportation Programs and Provisions of the Clean Air Act Amendments of 1990, U.S.DOT, Federal Highway Administration, 1992, pp. T-1, T-2.
|Classification||8-hour Concentration(ppm)||Attainment Date||*Requirements/Actions
(Will be addressed in Phase 2 of theImplementation Rule)
|These areas were determined based on one hour design values less than 0.121 ppm||06/15/09|
|Marginal||0.085 to 0.092||06/15/07|
|Moderate||0.092 to 0.107||06/15/10|
|Serious||0.107 to 0.120||06/15/13|
0.120 to 0.127
0.127 to 0.187
|Extreme||0.280 and above||06/15/21|
* The reference guide has not been updated to include the requirements and actions contained in the Phase 2 Implementation Rule. Please see the November 29, 2005 rule (70 FR 71612-71705) for more information.
|Classification||8-hour Concentration(ppm)||Attainment Date||Requirements/Actions|
|Moderate||9.1 to 12.7||12/31/95|| Oxygenated Gasoline-Areas with a design value of 95 ppm or above must submit a revision by November 15, 1992, requiring gasoline with no less than 2.7 percent oxygen content in the nonattainment area during the winter months
Basic Inspection and Maintenance Program (I/M)-The SIP is required to be revised to include a basic I/M Program, if such a Program were required before enactment
|Moderate||12.7 to 16.5||12/31/95|| Enhanced Inspection and Maintenance Program-Submit provision for an enhanced I/M Program by November 15, 1992, that meets all of EPA's requirements for such a program. The National Highway System Act of 1995 prohibits EPA from requiring adoption or implementation by a State of a test-only I/M240 enhanced vehicle inspection and maintenance program as a means of compliance with section 182 or 187 of the CAA, but the EPA may approve such a program if a State chooses to adopt the program as a means of compliance with such section.
VMT Forecast -Revise the SIP by November 15, 1992, to include an annual VMT forecast until attainment. Reports shall contain annual updates of the VMT forecasts and estimates of actual VMT levels. Such SIP revisions do not establish budgets for use in conformity determinations.
Contingency Measures-Contingency provisions (some of which could be TCMs) must be identified in the 1992 SIP submittal to implement specific measures if any estimate of VMT exceeds predicted levels or the area fails to attain the NAAQS. These measures take effect without further action by the State or the EPA
Clean-fuel Fleet Program-Areas having a design value at or above 16 ppm and a 1980 population of 250,000 or more must revise the SIP by May 15, 1994, to contain a clean-fuel vehicle program for centrally fueled fleets of 10 or more vehicles. The SIP must include provisions to ensure the effectiveness of the program
|Serious||16.5 and above||12/31/00||Vehicle Miles Traveled Limitations-Submit specific transportation control strategies by November 15, 1992, for implementation to offset growth in emissions from growth in VMT or number of trips. Such SIP revisions do not establish budgets for use in conformity determinations.|
Source: Transportation Programs and Provisions of the Clean Air Act Amendments of 1990, U.S. DOT, Federal Highway Administration, 1992, p. T-3.
|Moderate||All areas initially||12/31/94||SIP Submittal-Submit a SIP by November 15, 1991, demonstrating attainment of the NAAQS by December 31, 1994|
|Serious||Areas determined could not practicably attain by moderate attainment date||Varies||SIP Submittal-Submit a SIP no later than 4 years after reclassification of the area to serious. The SIP must demonstrate attainment of the NAAQS by no later than the 10th calendar year after the area's classification|
Source: Transportation Programs and Provisions of the Clean Air Act Amendments of 1990, U.S. DOT, Federal Highway Administration, 1992, p. T-3.
EPA has deferred the effective date of 8-hour designations for areas participating in Early Action Compacts (EAC). To receive this deferral, EAC areas have agreed to reduce ground-level ozone pollution earlier than the CAA would require (69 FR 23865). The deferral of 8-hour designations in these areas is dependent upon the area's adherence to all the terms and milestones of its EAC as well as EPA's November 14, 2002 memorandum entitled "Schedule for 8-Hour Ozone Designations and its Effect on Early Action Compacts," the December 16, 2003 proposed EAC rule (68 FR 70108), and the April 30, 2004 final designations rule (69 FR 23864).
Conformity for the 8-hour ozone standard will apply in EAC areas only if an area fails to meet any of the terms and milestones of its compact. Consistent with the Clean Air Act section 176(c) and § 93.102(d) of the conformity rule, conformity for the 8-hour ozone standard will not apply until one year after the effective date of an EAC area's 8-hour nonattainment designation. On the other hand, if an area meets all of the terms and milestones outlined in the compact and attains the 8-hour ozone standard by December 2007, conformity for the 8-hour ozone standard would not apply because the area's designation would be attainment. The table below outlines the milestones and submissions that EAC areas are required to complete in order to defer the effective date of nonattainment designation for the 8-hour ozone standard.
|Submittal Date||Compact Milestone|
|December 31, 2002||Submit Compact for EPA signature.|
|June 16, 2003||Submit preliminary list and description of potential local control measures under consideration.|
|March 31, 2004||Submit complete local plan to State (includes specific, quantified and permanent control measures to be adopted).|
|December 31, 2004||State submits adopted local measures to EPA as a SIP revision that, when approved, will be federally enforceable.|
|2005 Ozone Season (or no later than December 31, 2005).||Implement SIP control measures|
|June 30, 2006||State reports on implementation of measures and assessment of air quality improvement and reductions in NOX and VOC emissions to date|
|December 31, 2007||Areas attain 8-hour ozone NAAQS|
Source: Federal Register/Volume 69, No.84/Friday, April 30, 2004/Rules and Regulations
Conformity for the 1-hour standard will continue to apply in EAC areas that are currently 1-hour ozone maintenance areas. If an EAC area meets all of the milestones and terms of its compact and attains the 8-hour standard by December 2007, conformity for the 1-hour standard will be revoked one year after the effective date of EPA's 8-hour attainment designation (i.e. Spring 2009). On the other hand, if a 1-hour ozone maintenance area fails to meet any of the milestones and terms of its EAC, EPA would lift its deferral, and the area's 8-hour ozone nonattainment designation would become effective shortly after the missed milestone. Under this scenario, conformity for the 1-hour ozone standard will continue to apply until one year after the effective date of an areas 8-hour nonattainment designation. Occurring one year after EPA's effective date of designation will be revocation of the 1-hour standard, expiration of the one-year conformity grace period, and the application of conformity for the 8-hour ozone standard under Clean Air Act section 176(c)(6)(69 FR 40014, July 1, 2004).
 42 U.S.C. §7506 and related requirements of 23 U.S.C. §109 (j)
 Intermodal Surface Transportation Efficiency Act of 1991, Public Law 102-240, December 18, 1991
 Transportation Equity Act for the 21st Century, Public Law 105-178, June 9, 1998
 Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for User (SAFETEA-LU), Public Law 109-59, August 10, 2005.
 Throughout this Guide, appropriate reference will be made to either ISTEA, TEA-21 or SAFETEA-LU, as applicable
 42 U.S.C. §7506
 40 CFR, Parts 51 and 93
 23 CFR Part 450, 49 CFR Part 613
 23 U.S.C. §§101-128 (Due to litigation over the applicability of conformity to attainment areas, The National Highway System Designation Act of 1995 specifically restricted the application of the conformity requirements to nonattainment and maintenance areas only.)
 CAA §§101-192, 42 U.S.C. §§7401-7514(a)
 CAA §107(d), 42 U.S.C. §7407(d)
 42 U.S.C. §7410
 The standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm is equal to or less than one, as determined according to 40 CFR Part 50.
 The standard is evaluated on the 4th highest (daily maximum) 8-hour average per year, averaged over 3 years.
 The annual standard will be met when the 3-year average of the annual arithmetic mean PM2.5 concentration is less than or equal to 15 µg/m3.
 The 24-hour standard will be met when the 3-year average of the 98th percentile of 24-hour PM2.5 concentration is less than or equal to 65µg/m3.
 The PM10 annual standard is attained when the expected annual arithmetic mean concentration is less than or equal to 50µg/m3.
 The 24-hour PM10 standard is based on the 99th percentile concentration averaged over three years.
 CAA §175A(a), 42 U.S.C. §7505(a)