EPA420-B-06-901	 	 	 	 	 	 	 	 	 	 February 2006

Interim Guidance for 

Implementing the 

Transportation Conformity 

Provisions in the Safe, 

Accountable, Flexible, 

Efficient Transportation 

Equity Act: A Legacy for 

Users (SAFETEA-LU)
EPA420-B-06-901	 	 	 	 	 	 	 	 	 February 2006

Interim Guidance for Implementing the

Transportation Conformity Provisions in the 

Safe, Accountable, Flexible, Efficient 

Transportation Equity Act:

A Legacy for Users (SAFETEA-LU)

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

Office of Natural and Human Environment

Federal Highway Administration

Office of Planning and Environment

Federal Transit Administration
TABLE OF CONTENTS 

Page 

Section 1: Introduction.................................................................................1 

1.1 What is the purpose of this interim guidance?

1.2 What is transportation conformity?

1.3 Does this guidance create new requirements?

1.4 What are EPA’s plans for revising the conformity rule to address the changes made in 

SAFETEA-LU?

1.5 Who can I contact for more information?

1.6 Where can I find more information on the web? 

Section 2: Conformity Redeterminations............................................................................5 

2.1 What does this provision do?

2.2 When does this provision apply? 

2.3 Does this provision have any effect on when adequacy and approval clocks begin? 

2.4 How do EPA and DOT interpret “approves a SIP that establishes a motor vehicle emissions 

budget if that budget has not yet been determined to be adequate”?

2.5 How does the requirement to redetermine conformity relate to the transportation planning 

update clocks?

Section 3: Frequency of Conformity Determinations.......................................................7 

3.1 What does this provision do?

3.2 When does this provision apply?

3.3 Does the discussion in DOT’s May 25, 2001, guidance that aligns the transportation 

planning update and conformity update requirements still apply?

Section 4: Time Horizon for Conformity Determinations in Nonattainment Areas.....9 

4.1 What does this provision do?

4.2 When does this provision apply?

4.3 Can an election made under this provision be made at the same time as a conformity 

determination? 

4.4 Does an “election of the MPO” require an MPO policy board action? 

4.5 Does an MPO that elects to shorten the horizon need to make this election each time it 

makes a conformity determination, or only once? 

4.6 If an MPO elects to shorten the horizon, can it in the future elect to go back to having 

conformity apply for the entire length of the transportation plan?

4.7 What constitutes “consultation with the air pollution control agency,” and does that agency 

need to concur? Does this election need to be part of the interagency consultation 

procedures and conformity SIP?

i 
4.8 What is an “air pollution control agency?” Might the requirement to consult with such 

agency actually apply to multiple agencies? 

4.9 Does this election need to be included in the public involvement procedures for the MPO? 

4.10 If the MPO does make the election under this provision, what analysis years should be used 

for the regional emissions analysis? 

4.11 What constitutes “the first 10-year period of any such transportation plan” when an area 

amends its plan or TIP? 

4.12 What is meant by “applicable SIP?” 

4.13 If an MPO has elected to shorten its horizon, and wants to amend its plan in the years 

beyond the conformity horizon, will this trigger the need to redetermine conformity? 

4.14 Does the phrase “the project requires approval before the subsequent conformity 

determination” apply to non-federal projects? 

4.15 Can an MPO that is subject to conformity for multiple pollutants elect to shorten the 

conformity horizon year for one pollutant, but not for another? 

4.16 Can an MPO that has made this election rely on a previous regional emissions analysis that 

was completed prior to the election? 

4.17 Prior to adequate or approved budgets, if a nonattainment or maintenance area contains 

multiple MPOs, do all of the MPOs have to make this election, or can only one MPO make 

this election? 

4.18 Once there are adequate or approved budgets, if a nonattainment or maintenance area within 

the same state contains multiple MPOs, do all of the MPOs have to make this election, or 

can only one MPO make this election? 

4.19 Prior to adequate or approved budgets, if a nonattainment or maintenance area contains 

multiple states, does the MPO(s) have to make this election for all states, or can an MPO 

make a separate election for a state? 

4.20 Once there are adequate or approved budgets, if a nonattainment or maintenance area 

contains multiple states, does the MPO(s) have to make this election for all states, or can an 

MPO make a separate election for a state? 

4.21 How does this provision apply in donut areas? 

4.22 Does this provision apply in isolated rural areas? 

4.23 What is meant by “if the project is included in the TIP?” 

4.24 What is meant by “the project requires approval before the subsequent conformity 

determination?” 

4.25 Can non-regionally significant, non-exempt projects be found to conform even if the 

completion date of the project is beyond the shortened horizon? 

4.26 Under this election, does the appropriate conformity test have to be met for the last year of 

the transportation plan? What about for any year shown to exceed emission budgets by a 

prior analysis? 

4.27 How would the provision “and for any year shown to exceed emission budgets by a prior 

analysis” apply if there were no applicable emissions budgets? 

4.28 Do MPOs that utilize this provision in the case of an adequate or approved second ten-year 

maintenance plan have to develop a regional emissions analysis for the last year of the plan? 

4.29 Does this provision change the requirement to analyze hot-spot emissions required under 

section 93.116 for the full length of the transportation plan? 

ii 
Section 5: Substitution of Transportation Control Measures...............................19 

5.1 What does this provision do? 

5.2 When does this provision apply? 

5.3 How does this provision affect EPA’s April 7, 2004, guidance on TCM substitution 

mechanisms? 

5.4 What does SAFETEA-LU require in order for a TCM substitution to occur? 

5.5 What does SAFETEA-LU require in order for a new TCM to be added to an area’s SIP? 

5.6 Who must concur for EPA on the substitution or addition of TCMs? 

5.7 How does an MPO or state/local transportation or air agency demonstrate that a substitute 

TCM provides equivalent emissions reductions? 

5.8 What additional information should be provided to support a TCM substitution or addition? 

5.9 Can the TCM substitution process be used to remove a TCM from the applicable SIP 

without providing a substitute measure? 

5.10 If a substitute TCM cannot be implemented on the same schedule as the original TCM, what 

is necessary in order to fulfill SAFETEA-LU’s requirement that “the replacement TCM 

must be implemented as soon as practicable but not later than the date on which emission 

reductions are necessary to achieve the purpose of the implementation plan?” 

5.11 Would EPA concur on a substitution if the substitute TCM could not be implemented until 

after the date on which emission reductions are necessary to achieve the purpose of the 

implementation plan? 

5.12 Are TCMs in 1-hour ozone SIPs subject to the Clean Air Act and conformity rule 

requirements for timely implementation? And, can a TCM in an approved 1-hour ozone 

SIP in an 8-hour ozone nonattainment area be replaced by a substitute TCM through the 

TCM substitution process? 

5.13 What is necessary in order for an MPO or other implementing agency to show that it has 

adequate personnel and funding to implement the substitute or additional TCM? 

5.14 What is necessary in order for an MPO or other implementing agency to demonstrate that 

there is adequate authority under state or local law to implement, monitor and enforce the 

substitute or additional TCM? 

5.15 What agencies would be involved in the collaborative process used to develop substitute 

and additional TCMs? 

5.16 What is necessary in order to demonstrate that the collaborative process used to develop 

substitute and additional TCMs included reasonable public notice and opportunity for 

comment? 

5.17 How do the involved agencies indicate their concurrence on the substitution or addition? 

5.18 When can an MPO make a conformity determination based on a substitution? 

5.19 What action will EPA take to incorporate the substitute or additional TCM into the codified 

SIP? 

5.20 Is a conformity determination or a SIP revision required when a substitution is made or 

when a TCM is added? 

5.21 What process should areas outside of metropolitan areas follow to implement this 

provision? 

iii 
Section 6: Lapse of Conformity......................................................................31 

6.1 What does this provision do?

6.2 When does the provision take effect? 

6.3 To which “applicable deadlines” does this provision apply?

6.4 Does this provision apply to newly designated nonattainment areas? 

6.5 Does this provision apply to ‘donut’ areas (as defined in 40 CFR 93.101)? 

6.6 How can projects be advanced pursuant to transportation planning requirements during the 

conformity lapse grace period?

6.7 Can conformity lapse grace periods accumulate, one after another, in a given area? 

6.8 What happens if an area misses the two-year trigger to redetermine conformity after an EPA 

action establishing a new motor vehicle emissions budget?

6.9 If a nonattainment of maintenance area has subarea budgets and one subarea is in a lapse 

grace period, can other subareas make conformity determinations? 

6.10 What happens at the end of the 12-month conformity lapse grace period? 

6.11 Can project-level conformity be determined and final environmental documents be 

approved during the conformity lapse grace period? 

6.12 Can regionally significant non-federal projects be approved during the grace period? 

Section 7: Inclusion of Criteria and Procedures in SIP.........................................................35 

7.1 What does this provision do?

7.2 When does this provision apply?

7.3 Are any new conformity SIP deadlines created by SAFETEA-LU? 

7.4 How does SAFETEA-LU impact areas that have not previously submitted or approved 

conformity SIPs?

7.5 How does SAFETEA-LU impact areas that have previously submitted or approved 

conformity SIPs?

7.6 How does this provision affect the 12-month conformity SIP submission clocks that were 

started by the July 1, 2004, and May 6, 2005, final conformity rules?

7.7 How does this provision affect EPA’s November 2004 conformity SIP guidance?

7.8 Can states continue to include provisions in their SIPs that are more stringent than the 

federal rule? 

Appendix: Clean Air Act Section 176 as Amended by SAFETEA-LU..........................39 

iv 
Section 1: Introduction 

1.1 What is the purpose of this interim guidance? 

The purpose of this document is to provide areas that are subject to transportation conformity 

with guidance on implementing the transportation conformity-related provisions contained in the 

Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users 

(SAFETEA-LU), which was signed into law on August 10, 2005.1

 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 state 

implementation plan (SIP) motor vehicle emissions budgets are either found adequate, 

approved or promulgated; 

• changing the frequency requirements for transportation conformity determinations; 

• providing an option for reducing the time period covered by conformity determinations; 

• providing procedures for areas to use in substituting or adding transportation control 

measures (TCMs) to approved SIPs; 

• adding a one-year grace period for conformity lapses; and 

• streamlining requirements for conformity SIPs. 

This guidance explains how to apply the transportation conformity-related changes made in 

SAFETEA-LU during the period before the federal conformity rule is revised to address the 

changes made by SAFETEA-LU. 

1.2 What is transportation conformity? 

Transportation conformity is required under Clean Air Act section 176(c) to ensure that federally 

supported highway and transit project activities are consistent with (“conform to”) the purpose of 

the SIP. Conformity currently applies to areas that are designated nonattainment, and those 

redesignated to attainment after 1990 (“maintenance areas” with plans developed under Clean 

Air Act section 175A) for the following transportation-related criteria pollutants: ozone, 

particulate matter (PM2.5 and PM10), carbon monoxide (CO), and nitrogen dioxide (NO2). 

Conformity to the purpose of the SIP means that transportation activities will not cause new air 

quality violations, worsen existing violations, or delay timely attainment of the relevant national 

ambient air quality standards (NAAQS or “standards”). The transportation conformity 

regulation is found in 40 CFR part 93 and provisions related to conformity SIPs are found in 40 

CFR 51.390. 

 Areas are subject to transportation conformity if they are nonattainment or maintenance for ozone, carbon 

monoxide, PM2.5, PM10 or nitrogen dioxide. 

1 

1
1.3 Does this guidance create new requirements?

No, this guidance is based on Clean Air Act transportation conformity requirements as 

revised by SAFETEA-LU and existing associated regulations and does not create any 

new requirements. This guidance merely explains how to implement the transportation 

conformity-related provisions contained in SAFETEA-LU. 

The statutory provisions and the US Environmental Protection Agency (EPA) and US 

Department of Transportation (DOT) regulations described in this document contain 

legally binding requirements. This document is not a substitute for those provisions or 

regulations, nor is it a regulation itself. Thus, it does not impose legally binding 

requirements on EPA, DOT, states, or the regulated community, and 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 statute and SIP, conformity and planning regulations. Any decisions 

regarding a particular SIP, conformity determination or TCM substitution or addition will 

be made based on the statute and regulations, after appropriate public input and 

rulemaking procedures where applicable. This guidance may be revised periodically 

without public notice. 

1.4 What are EPA’s plans for revising the conformity rule to address the changes 

made in SAFETEA-LU?

SAFETEA-LU section 6011(g) requires that EPA, within two years of the date that 

SAFETEA-LU was enacted, revise the transportation conformity rule as necessary to

address the new statutory provisions. 

1.5 Who can I contact for more information?

For specific questions concerning a particular nonattainment or maintenance area, please 

contact the SIP or transportation conformity staff person responsible for your state at the 

appropriate EPA regional office, Federal Highway Administration (FHWA) division 

office or Federal Transit Administration (FTA) regional office. A listing of EPA regional 

offices, the states they cover, and contact information for EPA regional conformity staff 

can be found at the following website: www.epa.gov/otaq/transp/conform/contacts.htm. 

Contact information for FHWA division offices can be found at: 

www.fhwa.dot.gov/field.html and contact information for FTA regional offices can be 

found at: www.fta.dot.gov/about/offices/4978_ENG_HTML.htm. 

General questions about this guidance can be directed to: 

Rudy Kapichak at EPA’s Office of Transportation and Air Quality, 

kapichak.rudolph@epa.gov or 734-214-4574; 

Cecilia Ho at FHWA’s Office of Natural and Human Environment, 

cecilia.ho@fhwa.dot.gov or 202-366-9862; or 

2 
Abbe Marner at FTA’s Office of Planning and Environment, 

abbe.marner@fta.dot.gov or 202-366-4317. 

1.6 Where can I find more information on the web?

Additional information on the transportation conformity rule and associated guidance can 

be found on EPA’s website at: www.epa.gov/otaq/transp/conform. 

Similarly, information on the conformity rule and associated guidance along with 

additional information on SAFETEA-LU implementation can be found at: 

www.fhwa.dot.gov/environment/conform.htm and 

www.fhwa.dot.gov/safetealu/index.htm. 

Information on SAFETEA-LU can also be found at FTA’s website at: 

www.fta.dot.gov/17003_ENG_HTML.htm. 

3 
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4 
Section 2: Conformity Redeterminations

SAFETEA-LU section 6011(a) reads as follows:

(a) Conformity Redeterminations.--Section 176(c)(2) of the Clean Air Act (42 U.S.C. 

7506(c)(2)) is amended by adding at the end the following: 

``(E) The appropriate metropolitan planning organization shall redetermine 

conformity of existing transportation plans and programs not later than 2 years 

after the date on which the Administrator-- 

``(i) finds a motor vehicle emissions budget to be adequate in accordance 

with section 93.118(e)(4) of title 40, Code of Federal Regulations (as in 

effect on October 1, 2004); 

``(ii) approves an implementation plan that establishes a motor vehicle 

emissions budget if that budget has not yet been determined to be adequate 

in accordance with clause (i); or 

``(iii) promulgates an implementation plan that establishes or revises a 

motor vehicle emissions budget.''.

2.1 What does this provision do?

This provision gives areas two years, increased from the previous 18 months, to 

determine conformity after actions that establish new motor vehicle emissions budgets: 

• the effective date of EPA’s finding a motor vehicle emissions budget adequate; 

• EPA’s approval into the SIP of a budget that has not yet been found adequate; or 

• EPA’s promulgation a of federal implementation plan that establishes a budget. 

2.2 When does this provision apply?

This provision took effect on August 10, 2005, when SAFETEA-LU was signed into law. 

The SAFETEA-LU conference report states that, “In the case where conformity is 

triggered by and EPA SIP action, this section provides metropolitan areas with 2 years to 

determine conformity (currently, areas have 18 months).” Therefore, all 18-month clocks 

that started prior to August 10, 2005, have been extended by six months by statute, 

bringing the total time of the existing clocks to two years. Additionally, all clocks started 

by adequacy findings or approvals after August 10, 2005, are now two-year clocks. 

2.3 Does this provision have any effect on when adequacy and approval clocks 

begin? 

No, this provision does not change the point at which these clocks begin. The clocks 

begin on the effective date of EPA’s adequacy finding or the effective date of EPA’s SIP 

approval or federal implementation plan promulgation action, which is consistent with 

EPA’s conformity rule. (For more details see sections XV and XIX of the July 1, 2004, 

final rule, 69 Federal Register pages 40038 and 40050, respectively.) 

5 
2.4 How do EPA and DOT interpret “approves a SIP that establishes a motor 

vehicle emissions budget if that budget has not yet been determined to be 

adequate”?

The language in SAFETEA-LU specifies that the clock associated with a budget that is 

approved into the SIP only starts if the budget was not previously found adequate. If a 

budget had previously been found adequate, a clock for that budget would already have 

started on the effective date of EPA’s adequacy finding, so no new clock would start at 

the time of EPA’s approval of the budget into the SIP. This interpretation is consistent 

with how EPA and DOT have implemented section 93.104(e)(1) and (2) of the 

transportation conformity rule.

2.5 How does the requirement to redetermine conformity relate to the 

transportation planning update clocks?

The two-year trigger to redetermine conformity is not directly related to the 

transportation planning update clock. Under SAFETEA-LU the update cycle for 

transportation plans in nonattainment and maintenance areas and for all transportation

improvement programs (TIPs) is four years. 

Any of the three criteria for conformity redeterminations could trigger the need for a new 

conformity determination prior to the time that a transportation plan or TIP update would 

be needed under the statute as revised. Conversely, a planning update clock could trigger 

the need for a new conformity determination because a plan or TIP update was required 

prior to the end of the two-year conformity redetermination clock. In such a case, the 

conformity determination on the updated transportation plan or TIP would need to be 

based on the newly adequate or approved budgets and would satisfy the two-year 

redetermination requirement. 

6 
Section 3: Frequency of Conformity Determinations

SAFETEA-LU section 6011(b) reads as follows:

(b) Frequency of Conformity Determination Updates.--Section 176(c)(4)(B)(ii) of the 

Clean Air Act (42 U.S.C. 7506(c)(4)(B)(ii)) is amended to read as follows: 

``(ii) address the appropriate frequency for making conformity 

determinations, but the frequency for making conformity determinations 

on updated transportation plans and programs shall be every 4 years, 

except in a case in which-- 

``(I) the metropolitan planning organization elects to update a 

transportation plan or program more frequently; or 

``(II) the metropolitan planning organization is required to 

determine conformity in accordance with paragraph (2)(E); and''. 

3.1 What does this provision do?

This provision replaces the three-year conformity update cycle for transportation plans 

and TIPs previously included in the Clean Air Act. This provision revises the Clean Air 

Act to provide that the frequency for making conformity determinations on updated 

transportation plans and TIPs shall be every four years, except in cases in which the 

metropolitan planning organization (MPO) elects to update a plan or TIP more 

frequently, or the MPO is required to determine conformity to meet a two-year trigger 

after the effective date of EPA’s adequacy finding, SIP approval, or promulgation of 

motor vehicle emissions budgets. 

3.2 When does this provision apply?

This provision took effect immediately on August 10, 2005, upon enactment of 

SAFETEA-LU, and the minimum frequency for making conformity determinations is 

now every four years. MPOs in nonattainment and maintenance areas may opt to apply 

the SAFETEA-LU four-year transportation plan update cycle to their existing conforming 

transportation plan. However, if they choose to do so, the subsequent transportation plan 

must reflect all SAFETEA-LU planning provisions at the time of the FHWA/FTA 

conformity determination.

Many areas have developed or are continuing to develop TIPs according to the preSAFETEA-LU metropolitan planning requirements. Such TIPs continue to be subject to 

two-year updates. Conformity determinations continue to be required at the time when 

such updates are made. 

SAFETEA-LU section 6001(b) specifically states that “The Secretary shall not require a 

State or metropolitan planning organization to deviate from its established planning 

update cycle to implement changes” made by SAFETEA-LU prior to July 1, 2007. 

Therefore, states and MPOs are allowed to continue to comply with existing planning 

regulations for any metropolitan transportation plans and TIPs developed prior to July 1, 

7 
2007, including adherence to transportation plan and TIP update cycles and content 

requirements. Therefore, transportation plans and TIPs that are updated in accordance 

with the pre-SAFETEA-LU transportation planning cycles will have to demonstrate 

conformity according to those pre-SAFETEA-LU cycles. 

However, if a state or MPO opts to implement all of the SAFETEA-LU section 6001 

planning provisions prior to July 1, 2007, then the four-year update cycle would apply to 

the area’s transportation plan and TIP, which would be in line with the four-year 

frequency for conformity determinations. 

For transportation plans and TIPs developed after July 1, 2007, FHWA/FTA would be 

able to make a conformity determination only if the SAFETEA-LU planning provisions 

have been met. Please see FHWA/FTA interim guidance on SAFETEA-LU planning, 

environment, and air quality provisions for more information 

(http://www.fhwa.dot.gov/hep/legreg.htm). 

3.3 Does the discussion in DOT’s May 25, 2001, guidance that aligns the 

transportation planning update and conformity update requirements still apply?

Yes. The transportation planning update clock and the conformity update clock both 

begin upon the date of the FHWA and FTA conformity determination for the respective 

plan and/or TIP. The May 25, 2001, guidance is available at 

http://www.fhwa.dot.gov/environment/conformity/planup_m.htm. 

8 
Section 4: Time Horizon for Conformity Determinations in Nonattainment Areas

SAFETEA-LU section 6011(c) reads as follows:

(c) Time Horizon for Conformity Determinations in Nonattainment Areas.--Section 

176(c) of the Clean Air Act (42 U.S.C. 7506(c)) is amended by adding at the end the 

following: 

``(7) Conformity horizon for transportation plans.-- 

``(A) In general.--Each conformity determination required under this 

section for a transportation plan under section 134(i) of title 23, 

United States Code, or section 5303(i) of title 49, United States Code, 

shall require a demonstration of conformity for the period ending on 

either the final year of the transportation plan, or at the election of the 

metropolitan planning organization, after consultation with the air 

pollution control agency and solicitation of public comments and 

consideration of such comments, the longest of the following periods: 

``(i) The first 10-year period of any such transportation plan. 

``(ii) The latest year in the implementation plan applicable to 

the area that contains a motor vehicle emission budget. 

``(iii) The year after the completion date of a regionally 

significant project if the project is included in the 

transportation improvement program or the project requires 

approval before the subsequent conformity determination. 

``(B) Regional emissions analysis.--The conformity determination 

shall be accompanied by a regional emissions analysis for the last year 

of the transportation plan and for any year shown to exceed emission 

budgets by a prior analysis, if such year extends beyond the applicable 

period as determined under subparagraph (A). 

``(C) Exception.--In any case in which an area has a revision to an 

implementation plan under section 175A(b) and the Administrator has 

found the motor vehicles emissions budgets from that revision to be 

adequate in accordance with section 93.118(e)(4) of title 40, Code of 

Federal Regulations (as in effect on October 1, 2004), or has approved 

the revision, the demonstration of conformity at the election of the 

metropolitan planning organization, after consultation with the air 

pollution control agency and solicitation of public comments and 

consideration of such comments, shall be required to extend only 

through the last year of the implementation plan required under 

section 175A(b). 

``(D) Effect of election.--Any election by a metropolitan planning 

organization under this paragraph shall continue in effect until the 

metropolitan planning organization elects otherwise. 

``(E) Air pollution control agency defined.--In this paragraph, the term

`air pollution control agency' means an air pollution control agency (as 

defined in section 302(b)) that is responsible for developing plans or 

9 
controlling air pollution within the area covered by a transportation 

plan.''.

4.1 What does this provision do?

This provision provides the option to shorten the horizon of plan/TIP conformity 

determinations. This provision amends the Clean Air Act to require a demonstration of 

conformity for the period ending with either the final year of the transportation plan, or at 

the election of the MPO, after consultation with the air pollution control agency and 

solicitation of public comments and consideration of such comments, the longest of the 

following periods: 

• The first 10-year period of any such transportation plan. 

• The latest year in the SIP applicable to the area that contains a motor vehicle 

emission budget. 

• The year after the completion date of a regionally significant project2 if the 

project is included in the TIP, or the project requires approval before the 

subsequent conformity determination. 

If the MPO elects to demonstrate conformity for less than the full length of the 

transportation plan, the conformity determination must be accompanied by a regional 

emissions analysis, for informational purposes only, for the last year of the transportation 

plan and for any year beyond the term of the conformity determination shown to exceed 

emission budgets by an informational emissions analysis that accompanied a previous 

conformity determination. 

In addition, if an area has an approved second 10-year maintenance plan, or has 

submitted a second 10-year maintenance plan and EPA has found its budgets adequate 

the MPO may elect to demonstrate conformity through the last year of the second 

maintenance plan. This election would be made after consultation with the air pollution 

control agency and solicitation of public comments and consideration of such comments. 

Any election by an MPO to shorten the horizon for conformity shall continue in effect 

until the metropolitan planning organization elects otherwise. 

The term “air pollution control agency” means an air pollution control agency that is 

responsible for developing plans or controlling air pollution within the area covered by a 

transportation plan.

2

 Regionally significant project, as defined in 40 CFR 93.101, means a transportation project (other than an

exempt project that is on a facility which serves regional transportation needs (such as access to and from

the area outside of the region, major activity centers in the region, major planned developments such as

new retail malls, sports complexes, etc., or transportation terminals as well as most terminals themselves) 

and would normally be included in the modeling of a metropolitan area’s transportation network, including

at a minimum all principal arterial highways and all fixed guideway transit facilities that offer an 

alternative to regional highway travel. 

10 
4.2 When does this provision apply?

This provision took effect on August 10, 2005, when SAFETEA-LU was signed into law. 

However, MPOs must continue to demonstrate conformity through the final year of the 

transportation plan, unless they make an election under this provision. 

4.3 Can an election made under this provision be made at the same time as a 

conformity determination?

We encourage MPOs to make this election prior to the beginning of a public comment 

period on any conformity determination. However, if MPOs do wish to take public 

comment on the election at the same time as on a conformity determination, we think it is 

appropriate that the conformity information presented to the public include both an 

analysis reflecting the election, as well as an analysis that reflects the full length of the 

transportation plan. 

4.4 Does an “election of the MPO” require an MPO policy board action? 

Yes, the MPO policy board must make this election, similar to their responsibility to 

determine conformity. 

4.5 Does an MPO that elects to shorten the horizon need to make this election each

time it makes a conformity determination, or only once?

An election under this section need only be made once for a given pollutant or pollutants, 

and then it would apply for all future conformity determinations for that pollutant(s). As 

discussed in the SAFETEA-LU Conference Report, the decision to address a portion of 

the transportation plan rather than the entire plan when demonstrating conformity only 

needs to be made once, not each time a conformity determination is made.

4.6 If an MPO elects to shorten the horizon, can it in the future elect to go back to 

having conformity apply for the entire length of the transportation plan?

Yes. The MPO can elect to return to demonstrating conformity for the entire length of

the plan. We will address the specifics in our rulemaking to incorporate SAFETEA-LU 

provisions into the conformity rule. If an MPO that has elected to shorten the horizon 

wishes to elect to go back to determining conformity for the entire length of the plan prior 

to the rulemaking, please consult with your EPA regional office, and your FHWA 

division office and/or FTA regional office. 

4.7 What constitutes “consultation with the air pollution control agency,” and does 

that agency need to concur? Does this election need to be part of the interagency 

consultation procedures and conformity SIP?

Consultation with the air pollution control agency should include meaningful and timely 

discussion. The air pollution control agency is not required to concur in this election. 

11 
SAFETEA-LU does not specify a consultation process, but the MPO should incorporate 

consultation on an election into their normal interagency consultation with the air agency. 

In order for consultation with the air agency to be meaningful it should occur at an early 

stage in the decision making process. The MPO is not required to revise its existing 

interagency consultation procedures to include this consultation with the air agency and 

the air agency is not required to revise the conformity SIP for the area to address this 

consultation. 

4.8 What is an “air pollution control agency?” Might the requirement to consult 

with such agency actually apply to multiple agencies?

The air pollution control agency is the agency or agencies responsible for developing 

SIPs for the nonattainment or maintenance area or areas that include the MPO. This 

could include the state agency or local agencies specifically responsible for SIP 

development, and in some areas, agencies responsible for multi-state SIP development. 

Therefore, the MPO may be required to consult with multiple agencies. Please see 

Section 302(b) of the Clean Air Act (http://www.epa.gov/air/caa/caa302.txt) for the 

definition of an air pollution control agency. 

4.9 Does this election need to be included in the public involvement procedures for 

the MPO?

MPOs are required to solicit public comments and consider them in their election. MPOs 

should follow their normal process for public participation regarding conformity actions 

for this election. The MPO is not required to revise its public involvement procedures 

required by SAFETEA-LU section 6001 to address public consultation on reducing the 

area’s conformity horizon.

4.10 If the MPO does make the election under this provision, what analysis years 

should be used for the regional emissions analysis?

If an MPO makes this election, except in the case of an adequate or approved second tenyear maintenance plan, they should interpret references to “the last year of the 

[transportation] plan’s forecast period” in 40 CFR 93.118(b), 93.118(d)(2), and 93.119(g) 

to then be the latest of the following years: 

• The tenth year of the plan, 

• The latest year in the SIP applicable to the area that contains a motor vehicle 

emission budget, or 

• The year after the completion date of a regionally significant project if the project 

is included in the TIP, or the project requires approval before the subsequent 

conformity determination. 

All other analysis year requirements provided in 40 CFR 93.118(b), 93.118(d)(2) and 

93.119(g) must still be met whether or not the MPO makes this election. 

Where an area has an adequate or approved second ten-year maintenance plan, if an MPO 

elects to shorten the conformity horizon, they should interpret references to “the last year 

12 
of the [transportation] plan’s forecast period” in 40 CFR 93.118(b), and 93.118(d)(2) to 

be the last year of the second ten-year maintenance period. 

4.11 What constitutes “the first 10-year period of any such transportation plan” 

when an area amends its plan or TIP?

For FHWA and FTA actions on plans/TIPs and associated amendments and 

transportation conformity determinations that meet the requirements of 40 CFR 93.122(g) 

of the transportation conformity rule, which allows conformity determinations to rely on 

a previous regional emissions analysis, a long-range transportation plan initially found to 

conform with a 10-year conformity horizon remains sufficient. For example, an MPO 

has adopted a 2006 to 2026 transportation plan and made the conformity determination 

using a 10-year conformity horizon (i.e., 2016). In 2008, the MPO can adopt a new TIP 

that relies on the previous regional emissions analysis; that is, the conformity horizon 

year could remain 2016. 

However, if the long-range transportation plan is amended to add, delete, or significantly 

change the design concept or scope of a regionally significant project, or a regionally 

significant project is rescheduled such that it crosses conformity horizon years,3 the 

transportation plan's conformity horizon would need to be at least 10 years at the time of 

the MPO's action. For example, an MPO has adopted a 2006 to 2026 transportation plan 

with a 10-year conformity horizon (i.e., 2016). In 2008, the MPO amends the plan and 

TIP to add a regionally significant project. In this case, the conformity horizon year 

would need to be 2018. Note, in this example the 2018 horizon assumes that no new SIP 

budgets have been found adequate or approved beyond 2018, and that there are no 

regionally significant projects in the amended TIP with a completion date in 2018 or 

beyond. If however, a new SIP budget has been found adequate or approved beyond 

2018, the conformity horizon would need to be extended to the year for which the budget 

was established. For example if the budget was established for 2020, the conformity 

horizon would be 2020. 

4.12 What is meant by “applicable SIP?”

In general, the “applicable SIP” is the SIP for the standard and pollutant for which the 

conformity analysis is being done. However, for 8-hour ozone areas that are 

demonstrating conformity with budgets in 1-hour ozone SIPs, the 1-hour SIP will be 

treated as the “applicable SIP” until such time as 8-hour budgets are found adequate or 

approved. At that time, the 8-hour SIP would become the “applicable SIP.” 

3

 A conformity horizon year is defined in 40 CFR 93.101 as a year for which the transportation plan

describes the envisioned transportation system according to 40 CFR 93.106.

13 
4.13 If an MPO has elected to shorten its horizon, and wants to amend its plan in

the years beyond the conformity horizon, will this trigger the need to redetermine 

conformity?

Yes. Although this SAFETEA-LU provision addressed the conformity horizon, it did not 

change the requirement that a conformity determination is required for transportation 

plan revisions.

4.14 Does the phrase “the project requires approval before the subsequent 

conformity determination” apply to non-federal projects?

Yes. This provision applies to regionally significant non-federal projects that would 

require approval prior to the subsequent conformity determination. 

4.15 Can an MPO that is subject to conformity for multiple pollutants elect to 

shorten the conformity horizon year for one pollutant, but not for another?

Yes. If an MPO is nonattainment and/or maintenance for more than one pollutant it 

could shorten the horizon for one pollutant and its precursor(s) but not the other(s) and its 

precursor(s). For example, an area could maintain a 20-year horizon for ozone precursors 

but shorten the horizon to 10 years for CO. 

However, an MPO should retain the same horizon year for a pollutant and its precursors.

For example, a PM2.5 conformity determination would have the same horizon for PM2.5

and all applicable PM2.5 precursors. An 8-hour ozone conformity determination would 

have the same horizon for its precursors - NOx and volatile organic compounds (VOCs). 

4.16 Can an MPO that has made this election rely on a previous regional emissions 

analysis that was completed prior to the election?

Yes. However, the previous regional emissions analysis must have included an analysis 

for the new horizon year as defined by this section and must meet the requirements of 40 

CFR 93.122(g). For example, if the MPO now is using the tenth year of its plan (e.g., 

2016) for conformity purposes, then it can rely on the previous regional emissions 

analysis if an analysis was performed for that year (e.g., 2016). Also, please note that

according to 40 CFR 93.122(g)(3), reliance on a previous regional emissions analysis 

does not satisfy the frequency requirements in 40 CFR 93.104(b) and (c). 

4.17 Prior to adequate or approved budgets, if a nonattainment or maintenance 

area contains multiple MPOs, do all of the MPOs have to make this election, or can

only one MPO make this election?

This provision specifically applies at the MPO level, so it might appear that one MPO in 

a multi-MPO nonattainment or maintenance area could make this election even if the 

others do not. However, different analysis years may then apply to each MPO which 

could be in conflict with certain provisions under 40 CFR 93.119. 

14 
Therefore, for MPOs that are subject to 40 CFR 93.119 requirements, all of the MPOs 

within the nonattainment area would need to make the election to ensure that the regional 

emissions analysis covered the entire nonattainment area and that the same analysis years 

were used. 

(See EPA’s guidance “Conformity Implementation in Multi-jurisdictional Nonattainment 

and Maintenance Areas for Existing and New Air Quality Standards” for more 

information. A PDF copy of this guidance can be downloaded from the EPA website.) 

4.18 Once there are adequate or approved budgets, if a nonattainment or 

maintenance area within the same state contains multiple MPOs, do all of the MPOs 

have to make this election, or can only one MPO make this election?

For nonattainment and maintenance areas with multiple MPOs, but a single budget for 

the entire area, all of the MPOs within the nonattainment area would need to make the 

election to ensure that the regional emissions analysis covered the entire 

nonattainment/maintenance area and that the same analysis years were used. 

For MPOs with sub-area budgets who are conducting separate regional emissions 

analyses, an MPO could elect to shorten the conformity horizon regardless of any other 

MPO within the nonattainment or maintenance area that is not subject to that same subarea budget. 

4.19 Prior to adequate or approved budgets, if a nonattainment or maintenance 

area contains multiple states, does the MPO(s) have to make this election for all 

states, or can an MPO make a separate election for a state?

All of the MPOs within the nonattainment area would need to make the election to ensure 

that the regional emissions analysis covered the entire nonattainment area and that the 

same analysis years were used. 

4.20 Once there are adequate or approved budgets, if a nonattainment or 

maintenance area contains multiple states, does the MPO(s) have to make this 

election for all states, or can an MPO make a separate election for a state?

For nonattainment and maintenance areas with a single budget for the entire multi-state 

area, the MPO(s) within the area would need to make the election for all states to ensure 

that the regional emissions analysis covered the entire nonattainment/maintenance area 

and that the same analysis years were used. 

For MPOs with separate budgets for each state who are conducting separate regional 

emissions analyses, the election could be done separately for each state that is not subject 

to that same budget. 

15 
4.21 How does this provision apply in donut areas?

The regional emissions analysis for a donut area must be consistent with that of the 

associated MPO. Interagency consultation should be used to discuss the regional 

emissions analysis as required under 40 CFR 93.105(c)(3). 

4.22 Does this provision apply in isolated rural areas?

We will address how this provision applies in isolated rural areas in our rulemaking to 

incorporate SAFETEA-LU provisions into the conformity rule. If anyone in an isolated 

rural area would like to take advantage of this provision prior to the rulemaking, please 

consult with your EPA regional office, and your FHWA division office and/or FTA 

regional office. 

4.23 What is meant by “if the project is included in the TIP?”

For the purposes of determining a shortened horizon, a project is “included in the TIP” if 

any phase of the project other than an exempt phase, such as preliminary engineering to 

assess social, economic, and environmental effects of the proposed action or alternatives 

to that action, is included in the TIP. “Project” refers to the all required phases of a 

project necessary for implementation as reflected in the selected alternative in the NEPA 

document. In other words, if the TIP includes funding for any phase of final design, 

right-of-way acquisition, or construction, the horizon year must extend to the year beyond 

the completion date of the entire “project” as defined in the final NEPA document. 

4.24 What is meant by “the project requires approval before the subsequent 

conformity determination?”

This provision requires that the conformity horizon extend to the year beyond the 

completion date of a regionally significant project before the regionally significant 

project can be determined to conform and be approved. In general, this provision applies 

to approval of any phase of a project other than an exempt phase such as preliminary 

engineering to assess social, economic, and environmental effects of the proposed action 

or alternatives. For example, the conformity horizon must extend to the year beyond the 

completion date of a regionally significant project before FHWA/FTA, for such project, 

can issue a Record of Decision (ROD), make a Finding of No Significant Impact 

(FONSI), or determine that the project is Categorically Excluded (CE). With FTA’s 

major transit capital investment projects, the project must be included in a conforming 

transportation plan before preliminary engineering can be approved. Therefore, the 

conformity horizon must extend to the year beyond the completion date of such project 

before FTA can approve preliminary engineering. 

16 
4.25 Can non-regionally significant, non-exempt projects be found to conform even 

if the completion date of the project is beyond the shortened horizon?

Yes, but the project would still need to meet the requirements for project-level 

conformity. 

4.26 Under this election, does the appropriate conformity test have to be met for the 

last year of the transportation plan? What about for any year shown to exceed 

emission budgets by a prior analysis?

No. The regional emissions analysis described in Clean Air Act section 176(c)(7)(B), 

must be performed for the last year of the plan and for any year beyond the term of the 

conformity determination shown to exceed the emissions budgets by a prior 

informational analysis, but the analysis is for informational purposes only. This analysis

does not need to meet the requirements of the budget test (40 CFR 93.118) or the interim

emissions test(s) (40 CFR 93.119) for that year or years. 

4.27 How would the provision “and for any year shown to exceed emission budgets 

by a prior analysis” apply if there were no applicable emissions budgets? 

If there were no applicable emissions budgets at the time of the prior analysis, then the 

informational analysis would only need to be conducted for the last year of the plan. 

4.28 Do MPOs that utilize this provision in the case of an adequate or approved 

second ten-year maintenance plan have to develop a regional emissions analysis for 

the last year of the plan?

No. The requirement to develop an informational analysis does not apply to MPOs that 

elect to only demonstrate conformity through the end of the second ten-year maintenance 

period. 

4.29 Does this provision change the requirement to analyze hot-spot emissions 

required under 40 CFR 93.116 for the full length of the transportation plan?

No. This provision of SAFETEA-LU applies to the regional emissions analysis 

requirements for plans and TIPs, but does not apply to project-level hot-spot air quality 

analyses. 

17 
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18 
Section 5: Substitution of Transportation Control Measures

SAFETEA-LU section 6011(d) reads as follows:

(d) Substitution of Transportation Control Measures.--Section 176(c) of the Clean Air 

Act (42 U.S.C. 7506(c)) (as amended by subsection (c)) is amended by inserting after 

paragraph (7) the following: 

``(8) Substitution of transportation control measures.-- 

``(A) In general.--Transportation control measures that are specified in 

an implementation plan may be replaced or added to the 

implementation plan with alternate or additional transportation control 

measures— 

``(i) if the substitute measures achieve equivalent or greater 

emissions reductions than the control measure to be 

replaced, as demonstrated with an emissions impact analysis 

that is consistent with the current methodology used for 

evaluating the replaced control measure in the 

implementation plan; 

``(ii) if the substitute control measures are implemented— 

``(I) in accordance with a schedule that is consistent 

with the schedule provided for control measures in 

the implementation plan; or 

``(II) if the implementation plan date for 

implementation of the control measure to be 

replaced has passed, as soon as practicable after the 

implementation plan date but not later than the date 

on which emission reductions are necessary to 

achieve the purpose of the implementation plan; 

``(iii) if the substitute and additional control measures are 

accompanied with evidence of adequate personnel and 

funding and authority under State or local law to implement, 

monitor, and enforce the control measures; 

``(iv) if the substitute and additional control measures were 

developed through a collaborative process that included-- 

``(I) participation by representatives of all affected

jurisdictions (including local air pollution control 

agencies, the State air pollution control agency, and 

State and local transportation agencies); 

``(II) consultation with the Administrator; and 

``(III) reasonable public notice and opportunity for 

comment; and 

``(v) if the metropolitan planning organization, State air 

pollution control agency, and the Administrator concur with 

the equivalency of the substitute or additional control 

measures. 

19 
``(B) Adoption.--(i) Concurrence by the metropolitan planning

organization, State air pollution control agency and the Administrator 

as required by subparagraph (A)(v) shall constitute adoption of the 

substitute or additional control measures so long as the requirements 

of subparagraphs (A)(i), (A)(ii), (A)(iii) and (A)(iv) are met. 

``(ii) Once adopted, the substitute or additional control 

measures become, by operation of law, part of the State 

implementation plan and become federally enforceable. 

``(iii) Within 90 days of its concurrence under subparagraph 

(A)(v), the State air pollution control agency shall submit the 

substitute or additional control measure to the Administrator

for incorporation in the codification of the applicable 

implementation plan. Notwithstanding any other provision of 

this Act, no additional State process shall be necessary to 

support such revision to the applicable plan. 

``(C) No requirement for express permission.--The substitution or 

addition of a transportation control measure in accordance with this 

paragraph and the funding or approval of such a control measure shall 

not be contingent on the existence of any provision in the applicable 

implementation plan that expressly permits such a substitution or 

addition. 

``(D) No requirement for new conformity determination.--The

substitution or addition of a transportation control measure in 

accordance with this paragraph shall not require— 

``(i) a new conformity determination for the transportation 

plan; or 

``(ii) a revision of the implementation plan. 

``(E) Continuation of control measure being replaced.--A control 

measure that is being replaced by a substitute control measure under 

this paragraph shall remain in effect until the substitute control 

measure is adopted by the State pursuant to subparagraph (B). 

``(F) Effect of adoption.--Adoption of a substitute control measure 

shall constitute rescission of the previously applicable control 

measure.''. 

5.1 What does this provision do? 

SAFETEA-LU amends the Clean Air Act to provide nonattainment and maintenance 

areas with a streamlined process for either replacing TCMs in approved SIPs with 

alternate TCMs or for adding TCMs to their approved SIPs. Under this provision, states 

are no longer required to include a TCM substitution mechanism in their SIPs in order to 

expedite the process for making TCM substitutions. 

5.2 When does this provision apply?

This provision took effect on August 10, 2005, when SAFETEA-LU was signed into law. 

20 
Nonattainment and maintenance areas that do not have TCM substitution mechanisms in 

their approved SIPs may begin using this statutory mechanism immediately to make 

substitutions or to add TCMs to their SIPs. 

Several nonattainment and maintenance areas have TCM substitution mechanisms in 

their approved SIPs.4 These areas must continue to use their SIP-approved TCM 

substitution mechanisms in addition to the new statutory mechanism as applicable to 

make substitutions. However, there may be conflicts between an already approved 

mechanism and the provision contained in SAFETEA-LU. In the event of such a conflict 

the area would follow the requirement contained in SAFETEA-LU. EPA, FHWA and 

FTA will work with areas with approved mechanisms on a case-by-case basis to answer 

any questions. These areas may elect to revise their SIPs to remove the approved TCM 

substitution mechanism. EPA will act expeditiously to approve requests to remove 

previously approved TCM substitution mechanisms. EPA will consider using either 

parallel processing or a direct final approval, as appropriate, to expedite such approvals. 

5.3 How does this provision affect EPA’s April 7, 2004, guidance on TCM 

substitution mechanisms?

EPA is withdrawing the April 7, 2004, guidance document and replacing it with today’s 

guidance. While much of the earlier guidance remains relevant, the TCM substitution 

provision in SAFETEA-LU makes large portions of the existing guidance unnecessary. 

For example, the portion of the guidance that discusses what a state must include in its 

SIP in order to have an approvable TCM substitution mechanism is no longer relevant

because the provision in SAFETEA-LU allows states to make substitutions without 

having a substitution mechanism approved into their SIPs. 

We are including the portions of the April 7, 2004, guidance that remain relevant in this 

guidance document. 

5.4 What does SAFETEA-LU require in order for a TCM substitution to occur?

For a TCM in an approved SIP to be removed and replaced with an alternate TCM 

SAFETEA-LU requires that: 

• the substitute TCM(s) must achieve equal or greater emission reductions; 

• the substitute TCM(s) must be implemented on a schedule that is consistent with 

the schedule for the TCM(s) being removed from the SIP; or, if the 

implementation date has passed for the TCM(s) being replaced, the replacement 

TCM must be implemented as soon as practicable but not later than the date on 

which emission reductions from the TCM(s) are necessary to achieve the purpose 

of the implementation plan; 

4

 Portland, OR; Albuquerque, NM; Texas; and Boston, MA have TCM substitution mechanisms in their 

approved SIPs.

21 
• the substitute TCM(s) must be accompanied by evidence of adequate personnel, 

and funding and authority under state or local law to implement, monitor and 

enforce the TCM(s); 

• the substitute TCM(s) must be developed through a collaborative process that 

includes participation by all affected jurisdictions (state and local air pollution 

control agencies and state and local transportation agencies such as the MPO, 

state and city DOTs, and transit providers); consultation with EPA; and 

reasonable notice and opportunity for public comment; and 

• the equivalency of the substitute TCM(s) must be concurred on by the MPO, the 

state air pollution control agency and EPA. 

5.5 What does SAFETEA-LU require in order for a new TCM to be added to an 

area’s SIP?

SAFETEA-LU requires that in order for a new TCM to be added to an approved SIP: 

• the new TCM(s) must be accompanied by evidence of adequate personnel, and 

funding and authority under state or local law to implement, monitor and enforce 

the TCM(s); 

• the new TCM(s) must be developed through a collaborative process that includes 

participation by all affected jurisdictions and agencies (e.g., state and local air 

pollution control agencies and state and local transportation agencies); 

consultation with EPA; and reasonable notice and opportunity for public 

comment; and 

• the MPO, the state air pollution control agency and EPA must concur on the 

addition of the new TCM to the SIP. 

5.6 Who must concur for EPA on the substitution or addition of TCMs?

SAFETEA-LU requires concurrence by the Administrator of EPA. EPA intends to 

prepare a delegation of authority that will enable the Regional Administrators to concur

on substitutions and additions. However, for any substitutions or additions that occur 

before the delegation is finalized, the EPA regional office should participate in the 

collaborative process that is used to develop the TCMs and keep the EPA Administrator’s 

office informed as the process proceeds. If the substitution or addition fulfills all of the 

requirements contained in SAFETEA-LU, the regional office would transmit the package 

to the Administrator for concurrence. After concurrence, the Administrator would send a 

letter to the MPO and the state air agency. 

5.7 How does an MPO or state/local transportation or air agency demonstrate that 

a substitute TCM provides equivalent emissions reductions?

To demonstrate that the new TCM provides equal or greater emission reductions, the 

emission benefits of the substitute TCM should be analyzed in a manner that is consistent 

with the methodology used for analysis of the existing TCMs in the approved SIP, unless 

a better methodology is currently available. If a better methodology is available, the 

22 
project sponsor should recalculate the emissions benefits of the original TCM and use 

that emissions estimate in determining if the substitute TCM provides equivalent

emissions reductions. EPA and US DOT believe that the Clean Air Act requires that the 

latest planning assumptions, and emissions models must also be used, as generally 

required for conformity and SIP purposes. If hot-spot analyses are needed, they should 

use the applicable air quality models, data bases, and other requirements specified in 40

CFR part 51, Appendix W (Guideline on Air Quality Models) or follow other relevant 

EPA guidance or approved methodologies for hot-spot analyses. 

It should be noted that some approved SIPs include TCMs for which no emission 

reduction credit was claimed. If such a TCM is to be replaced through a TCM 

substitution, an emissions analysis should be performed for both the existing SIPapproved TCM and the proposed substitute TCM. It should be demonstrated that there 

will be an equivalent reduction in emissions as a result of the substitution. 

In determining whether or not a substitute TCM provides equivalent emission reductions, 

the area should document that the substitute TCM provides emission reductions that are: 

$ permanent for the time period relied upon in the applicable SIP; 

$ for the same time of year (e.g., during the winter carbon monoxide season) or 

during a specific time of day (e.g., the morning or evening rush hour) relied upon 

in the applicable SIP; 

$ for the same pollutant or precursor as the original SIP TCM, unless the area has a 

SIP-approved trading mechanism that would allow trading between precursors or 

between a pollutant and its precursor(s); and 

$ for the same geographic location, if the such a location is identified as critical for 

the emission reductions for the applicable SIP (e.g., to meet applicable hot-spot 

requirements). 

An area should also consider whether or not the substitution will have an effect on any 

other SIPs for the area. For example, if a TCM is relied upon in more than one SIP (e.g., 

a TCM is included in both an ozone attainment demonstration and a carbon monoxide 

maintenance plan) or is included in the baseline emissions, the emissions analysis that is 

performed for the substitution would need to consider the impacts on all the affected SIPs 

and motor vehicle emissions budgets. 

It should also be noted that nonattainment areas must continue to meet the Clean Air 

Act’s requirements for implementation of Reasonably Available Control Measures 

(RACM);5

 and serious PM10 nonattainment areas must continue to meet requirements for 

implementation of Best Available Control Measures (BACM).6 Serious, severe and 

5

 RACM requirements do not apply in maintenance areas. 6

 Provided that all applicable RACM and BACM requirements are met, EPA believes that TCMs

substituted through the use of the mechanism contained in SAFETEA-LU would fulfill the requirements of

Clean Air Act section 193 because the substitute TCMs provide equivalent emission reductions and 

therefore would not interfere with reasonable further progress or attainment. The requirements in Clean 

Air Act section 110(l) would not apply to substitutions made through the mechanism contained in

23 
extreme ozone areas and moderate and serious carbon monoxide areas that have adopted 

TCMs to comply with Clean Air Act sections 182(c)(5), 182(d)(1)(A), 182(e)(4), 

187(a)(2)(A) or 187(b)(2) may substitute TCMs; however, they must also continue to 

comply with those Clean Air Act requirements. 

5.8 What additional information should be provided to support a TCM substitution 

or addition?

The material prepared to support a substitution or addition should clearly identify and 

describe the TCM in the approved SIP and the substitute TCM or the additional TCM. 

The substitute or additional TCM should meet all of the requirements of Clean Air Act 

section 110 and EPA’s TCM SIP Guidance (EPA 450/2-89-020). Specifically, the 

documentation for each substitution or addition should include: 1) the name of the TCM 

in the approved SIP that is proposed to be replaced; 2) the name of the proposed 

substitute or additional TCM; 3) a brief but thorough description of both the original and 

substitute or additional TCMs including their locations and implementing agencies; 4) 

the steps and schedule for completing and operating the substitute or additional TCM; 

and 5) a brief explanation of why the substitution is necessary. 

5.9 Can the TCM substitution process be used to remove a TCM from the 

applicable SIP without providing a substitute measure? 

No. The TCM substitution process established in SAFETEA-LU does not provide legal 

authority for an area to remove a TCM from the applicable SIP unless it is replaced with 

a TCM that provides equivalent emissions reductions. TCMs can be removed from an 

applicable SIP through a SIP revision. Such a SIP revision would have to be shown to 

meet Clean Air Act section 110(l) requirements (e.g., the area would have to show that 

removal of the TCM would not interfere with any applicable requirement concerning 

attainment and reasonable further progress, or any other applicable Clean Air Act 

requirement). 

5.10 If a substitute TCM cannot be implemented on the same schedule as the 

original TCM, what is necessary in order to fulfill SAFETEA-LU’s requirement 

that “the replacement TCM must be implemented as soon as practicable but not 

later than the date on which emission reductions are necessary to achieve the 

purpose of the implementation plan?”

If it is not possible for the substitute TCM to be implemented by the same deadline as the 

original TCM, the substitute TCM would have to be implemented as expeditiously as 

practicable so that emission reductions can be achieved by the year required by the SIP. 

For example, if the TCM being replaced was to be implemented in 2008 and was 

included in the area’s 2010 ozone attainment demonstration, the substitute TCM should 

be fully implemented no later than the beginning of the 2009 ozone season (i.e., the final 

complete ozone season before the maximum June 2010 attainment date). The substitute 

SAFETEA-LU because section 110(l) only applies to control measures approved into the SIP by EPA and

these substitutions do not require EPA SIP approval. 

24 
TCM would be implemented by the time reductions are needed to support the SIP, in this 

case by the beginning of the 2009 ozone season. 

5.11 Would EPA concur on a substitution if the substitute TCM could not be 

implemented until after the date on which emission reductions are necessary to 

achieve the purpose of the implementation plan?

EPA would not concur on a given substitution if it would interfere with any applicable 

requirement for reasonable further progress or timely attainment or maintenance of any 

NAAQS. Reliance on the TCM substitution provision in SAFETEA-LU would not be 

appropriate in the case where both the implementation date for the original TCM and SIP 

milestone date have passed. For example, if a TCM that was included in an area’s 2010 

ozone attainment demonstration was to be in place in 2009 and became delayed, it would 

not be appropriate to use a TCM substitution mechanism to replace it with one that could 

not be implemented until 2011. In this case, a formal SIP revision would be required to 

address the attainment demonstration as well as the substitute TCM, to ensure that

sufficient control measures are in place to demonstrate timely attainment. 

5.12 Are TCMs in 1-hour ozone SIPs subject to the Clean Air Act and conformity 

rule requirements for timely implementation? And, can a TCM in an approved 1-

hour ozone SIP in an 8-hour ozone nonattainment area be replaced by a substitute 

TCM through the TCM substitution process?

EPA addressed requirements for the timely implementation of TCMs contained in 1-hour 

ozone SIPs in areas that are now designated as nonattainment or maintenance for the 8-

hour ozone standard in the July 1, 2004 new standards rulemaking. Specifically, EPA 

stated that: 

“Section 93.113 of the existing conformity rule requires that transportation plans, 

TIPs, and projects which are not from a conforming plan and TIP must provide 

for the timely implementation of TCMs from an approved SIP. EPA notes that 

today's final rule does not change the implementation of these requirements for 

any existing or new nonattainment or maintenance area, including 8-hour 

nonattainment areas that have approved 1-hour SIPs that contain TCMs. 

Clean Air Act section 176(c) requires that TCMs in approved SIPs be 

implemented in a timely manner according to the schedules in the SIP. This 

requirement is not contingent on what type of SIP, pollutant, or standard for 

which the approved TCM was established. Conformity determinations for any 

pollutant and standard must provide for the timely implementation of TCMs in 

approved SIPs, including TCMs in approved SIPs for the 1-hour ozone standard 

after that standard is revoked. Such TCMs can only be removed from the 1-hour 

SIP through the SIP process.” (69 FR 40013) 

Any area 8-hour ozone area considering changes to TCMs in an approved 1-hour SIP 

should consult with the EPA regional office in order to determine the appropriate 

mechanism for making the desired changes. 

25 
5.13 What is necessary in order for an MPO or other implementing agency to show

that it has adequate personnel and funding to implement the substitute or additional 

TCM?

TCMs that are included in an area’s transportation plan and TIP need to meet all 

applicable requirements in US DOT’s metropolitan planning regulations, including the 

metropolitan plan and TIP fiscal constraint requirement (23 CFR 450). Therefore, 

inclusion of the substitute or additional TCM in a fiscally constrained metropolitan plan 

and TIP generally would serve as sufficient evidence that adequate resources are 

available to implement the TCM. It is possible that situations will arise where an MPO 

would need to make a TCM substitution and revise its TIP to remove the original TCM 

and add the substitute TCM simultaneously. In such situations the MPO should use the 

consultation process to reach agreement on the details of these simultaneous actions. 

However, if the TCM is not federally funded or is not part of the plan and TIP, the 

implementing agency should provide additional information on the availability and 

commitment of adequate resources as necessary to implement the substitute TCM. 

5.14 What is necessary in order for an MPO or other implementing agency to 

demonstrate that there is adequate authority under state or local law to implement, 

monitor and enforce the substitute or additional TCM?

Generally, inclusion of the substitute or additional TCM in a metropolitan area’s plan and 

TIP, or in the case of a rural area, inclusion of the substitute TCM in the Statewide 

Transportation Improvement Program (STIP), would indicate that the implementing 

agency had legal authority to carry out the project. However, if the TCM is not federally 

funded or is not part of the plan and TIP, the implementing agency should provide 

additional information on its legal authority to implement the substitute TCM. 

Because the substitute or additional TCM becomes part of the approved SIP for the area, 

Clean Air Act sections 113 and 179(a) grant EPA the authority to enforce the 

implementation of such a TCM. Implementation of the substitute and additional TCMs 

may also be enforced by citizen suits under Clean Air Act section 304. 

5.15 What agencies would be involved in the collaborative process used to develop 

substitute and additional TCMs?

The agencies involved in the collaborative process used to develop substitute and 

additional TCMs would be similar to the group that participates in the area’s conformity

interagency consultation process. The involved agencies would include the state and 

local air quality and transportation agencies. The MPO and all of the jurisdictions 

affected by the substitution or addition that is being considered should also be involved. 

The process must also include the EPA regional office, who would be responsible for 

keeping the Administrator informed prior to the Administrator’s delegation of

concurrence to the Regional Administrator, and should also include the relevant FHWA 

and the FTA offices. Early consultation with federal agencies is essential to facilitate 

26 
subsequent concurrence on each substitution by EPA, and on conformity determinations 

based in part on timely implementation of substituted TCMs by FHWA and FTA. 

5.16 What is necessary in order to demonstrate that the collaborative process used 

to develop substitute and additional TCMs included reasonable public notice and 

opportunity for comment?

Reasonable public notice and a public comment period must be provided when the TCM 

substitution or addition is made. The public has to be provided access to all material 

relevant to the substitution, and all public comments submitted have to be considered and 

responded to. The state and/or local air agency should ensure that the TCM substitution 

process complies with all applicable laws and regulations for public participation 

including state or local sunshine laws. Copies of any prepared supporting documentation 

should be sent to the EPA regional office, which would be responsible for keeping the 

Administrator informed prior to the Administrator’s delegation of concurrence to the 

Regional Administrator, FHWA division office, the FTA regional office and any other 

relevant state and local air and transportation agencies. Because EPA’s concurrence on a 

specific substitution or addition would be EPA’s conclusion that the substitution or 

addition complies with the requirements set forth in SAFETEA-LU, commenters should 

be made aware through the announcement that they should submit comments not only on 

whether the state should concur on the substitution or addition but also on whether EPA 

should concur with that substitution or addition.

5.17 How do the involved agencies indicate their concurrence on the substitution or 

addition?

Following the close of the comment period, the state or local air agency and MPO as 

appropriate would summarize the comments received and prepare responses. Those 

agencies along with the EPA regional office should review the comments and responses 

and all material related to the substitution or addition. If the substitution or addition 

fulfills all of the requirements specified in SAFETEA-LU, the state air agency and EPA 

would each indicate its concurrence by sending a letter to the MPO and each other (i.e.,

the state air agency would send its letter to the EPA and vice versa). The MPO would 

indicate its concurrence by resolution of the MPO’s policy body. A substitution or

addition could not go into effect unless EPA, the state air agency and the MPO have all 

concurred on the substitution. Within 90 days of its concurrence, the state air agency 

must submit the substitute or additional control measure and all supporting information to 

the EPA regional office so that the TCM can be incorporated in the codified applicable 

SIP. 

Agencies should use their consultation process to establish the exact point in the process 

that concurrence will be given so that it meets SAFETEA-LU's requirements. 

SAFETEA-LU requires that concurrence by the air agency and EPA occur after 

equivalency of the substitute measure(s) is demonstrated and the SAFETEA-LU

conference report clarifies that "adoption occurs when the MPO, state air agency and 

EPA concur that all four of the general requirements in subparagraph (A) of the provision 

27 
have been fulfilled." Therefore, concurrence would have to occur sufficiently late in the 

process so that the agencies are sure that all four criteria have been met.

5.18 When can an MPO make a conformity determination based on a substitution?

An MPO can make a conformity determination based on a substitution as soon as the 

MPO, the state air pollution control agency and EPA have concurred on the substitution. 

Once all of these agencies have concurred, the substitute TCM is considered to be 

adopted. Once adopted under this process, the substitute TCM becomes part of the 

federally enforceable SIP for the area. The adoption of the substitute TCM also serves to 

remove the original TCM from the federally enforceable SIP. Therefore, once the 

adoption occurs, the original TCM is no longer subject to the Clean Air Act and 

transportation conformity rule requirements for timely implementation of TCMs. It 

should be noted that the original TCM remains in the approved SIP and subject to the 

timely implementation requirements until the replacement TCM is adopted. Subsequent 

to adoption, EPA will incorporate the substitute or new TCM(s) into the federal 

codification of the SIP to clarify which TCMs are part of the federally enforceable SIP.

5.19 What action will EPA take to incorporate the substitute or additional TCM 

into the codified SIP?

Once a state has submitted the substitute or additional TCM to EPA for incorporation in 

the codified applicable SIP, EPA will need to update the Code of Federal Regulations 

(CFR) to reflect the changes to the SIP. This would be done through the publication of a 

notice in the Federal Register. When a state that has been converted to the “SIP notebook 

system”7 substitutes or adds a non-regulatory TCM through the process established by

SAFETEA-LU, EPA would publish an informational notice in the rules section of the 

Federal Register to update the CFR. In states that have not yet been converted to the 

notebook system, or for TCMs that require regulations to be implemented, EPA would 

need to take a final action in the Federal Register to incorporate the substitute or 

additional TCM into the CFR. 

Since EPA will have concurred on any substitutions or additions that comply with the 

procedure established by SAFETEA-LU, EPA would take the final action incorporating 

the specific substitution or addition into the CFR without additional notice-and-comment 

rulemaking. EPA believes that it would have good cause under the Administrative 

Procedure Act to take these actions without additional opportunity for public comment 

because the substitution or addition was made through the process established by 

7

 The notebook system for compiling SIPs is a process under which EPA revises 40 CFR Part 52 by: 1) 

revising charts listed in the Identification of Plan section; 2) submitting State regulatory revisions for 

incorporation by reference into the SIP by means of a revised annual compilation (generally in a looseleaf 

notebook) of all State regulations listed in these Identification of Plan charts rather than by piecemeal 

regulation updates; and 3) updating the list of non-regulatory measures in the State’s SIP through the use of

an informational notice in the rules section of the Federal Register. Non-regulatory measures are not 

incorporated by reference into the Code of Federal Regulations; therefore, these materials are maintained in 

the notebook for the State at the EPA regional office and in a notebook maintained in the Office of the 

Federal Register. 

28 
SAFETEA-LU, and because the public would have had the opportunity to comment on 

the specific substitution or addition during the public comment period on the specific 

substitution or addition. 

5.20 Is a conformity determination or a SIP revision required when a substitution is 

made or when a TCM is added?

No, neither a conformity determination nor a SIP revision is required when an area makes 

a substitution or adds a new TCM to the approved SIP. However, if the plan and/or TIP 

need to be amended in order to implement the substitute TCM, all other transportation 

planning requirements would have to be met. 

5.21 What process should areas outside of metropolitan areas follow to implement 

this provision?

For donut areas (i.e., those areas within a nonattainment or maintenance area but outside 

the metropolitan planning area), this provision should be implemented as above and the 

MPO associated with the donut area should concur in any substitution. 

For isolated rural areas (i.e., those areas within a nonattainment or maintenance area that 

does not contain any metropolitan area), this provision should be implemented as above, 

except the state DOT should concur on the substitution or addition because there is no 

MPO in such an area. 

29 
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30 
Section 6: Lapse of Conformity

SAFETEA-LU section 6011(e) reads as follows:

(e) Lapse of Conformity.--Section 176(c) of the Clean Air Act (42 U.S.C. 7506(c)) (as 

amended by subsections (c) and (d)) is amended by inserting after paragraph (8) the 

following: 

``(9) Lapse of conformity.--If a conformity determination required under this 

subsection for a transportation plan under section 134(i) of title 23, United 

States Code, or section 5303(i) of title 49, United States Code, or a 

transportation improvement program under section 134(j) of such title 23 or 

under section 5303(j) of such title 49 is not made by the applicable deadline and 

such failure is not corrected by additional measures to either reduce motor 

vehicle emissions sufficient to demonstrate compliance with the requirements 

of this subsection within 12 months after such deadline or other measures 

sufficient to correct such failures, the transportation plan shall lapse. 

``(10) Lapse.--In this subsection, the term `lapse' means that the conformity 

determination for a transportation plan or transportation improvement program

has expired, and thus there is no currently conforming transportation plan or 

transportation improvement program.''. 

6.1 What does this provision do? 

If a nonattainment or maintenance area is not able to determine conformity for its 

transportation plan and/or TIP by a prescribed conformity deadline, this provision allows 

an additional 12 months from the missed deadline for the area to correct the problem

before a conformity lapse occurs. This provision also provides a statutory definition for 

the term “conformity lapse.” 

6.2 When does the provision take effect? 

The provision took effect on August 10, 2005, when SAFETEA-LU was signed into law. 

6.3 To which “applicable deadlines” does this provision apply? 

This provision applies to two kinds of conformity determination deadlines: 1) the 

deadlines resulting from the requirement to determine conformity for the transportation 

plan and TIP at regular intervals; and 2) the deadlines resulting from the requirement to 

redetermine transportation plan/TIP conformity within two years of an EPA action 

establishing a new motor vehicle emissions budget. 

The regular interval for redetermining conformity has now been amended to four years to 

coincide with the interval for updating the transportation plan and TIP. During the 

transition to the new SAFETEA-LU planning requirements, the conformity lapse grace 

period provision applies to the old three-year and two-year intervals for updating and 

determining conformity for transportation plans and TIPs, respectively. 

31 
The requirement to redetermine conformity after a new motor vehicle emissions budget is 

established has also been amended by SAFETEA-LU. Previously, conformity needed to 

be determined within 18 months; SAFETEA-LU increases that period to two years. The 

requirement to redetermine conformity within two years of EPA’s action establishing a 

new motor vehicle emissions budget applies to: a finding of adequacy; approval of a SIP 

with a budget that had not previously been found adequate; or promulgation of a federal 

implementation plan with a budget. (For a more thorough discussion of the deadlines, 

please refer to the “Frequency of Conformity Determination Updates” and “Conformity 

Redeterminations” sections of this interim guidance.) 

6.4 Does this provision apply to newly designated nonattainment areas?

No. This provision does not apply to the deadline for newly designated nonattainment 

areas to make the initial transportation plan/TIP conformity determination within 12 

months of the effective date of the nonattainment designation, as required under Clean 

Air Act section 176(c)(6) and 40 CFR 93.102(d). Thus, the restrictions of a conformity 

lapse will remain in effect for any nonattainment area for the 8-hour ozone standard that 

did not have a conforming transportation plan/TIP in place by June 15, 2005. For the fine 

particulate matter (PM2.5) standard, a lapse will occur for any PM2.5 nonattainment area 

that does not have a conforming transportation plan/TIP by April 5, 2006. Although 

DOT and EPA will continue to use the term “lapse” to describe these situations, the 

statutory and regulatory definition of “lapse” does not cover the newly designated areas 

since no conformity determination was ever made. 

6.5 Does this provision apply to ‘donut’ areas (as defined in 40 CFR 93.101)?

Yes. The conformity lapse grace period applies to donut areas in the same manner as it 

applies to metropolitan areas. 

6.6 How can projects be advanced pursuant to transportation planning 

requirements during the conformity lapse grace period? 

The 12-month conformity lapse grace period begins when the conformity determination 

required for a transportation plan or TIP is not made by the applicable deadline. During 

the grace period, the state or MPO may continue to advance projects as long as there is a 

valid STIP/TIP in place. Project-level conformity requirements must be met. Three 

specific scenarios are presented below to show how expiration of the plan and/or 

STIP/TIP at the time of the missed deadline affects the ability to advance projects: 

1. If the transportation plan has expired, but the STIP/TIP are still in effect, the 

nonattainment or maintenance area can continue to authorize and take action on 

projects in the STIP/TIP throughout the duration of the grace period or the duration of 

the STIP/TIP, whichever is shorter. The TIP and affected portion of the STIP cannot 

be amended once the transportation plan expires. Prior to plan expiration, MPOs and 

32 
states should ensure their STIP/TIP have the desired projects from their transportation 

plan to continue to operate during the conformity lapse grace period. 

2. If the transportation plan is still in effect, but the STIP/TIP have expired, FHWA/FTA 

cannot authorize projects. In order to advance projects, a new STIP/TIP must be 

developed containing only non-exempt and/or exempt projects that are consistent 

with the transportation plan. A conformity determination must be made for the new 

TIP unless it includes only exempt projects or TCMs in an approved SIP. For 

example, including a non-exempt project from the out-years of the transportation plan 

in the new TIP would require a conformity determination. 

3. If both the transportation plan and the STIP/TIP have expired, FHWA/FTA will not 

authorize projects. 

6.7 Can conformity lapse grace periods accumulate, one after another, in a given 

area? 

No. If an area fails to meet an applicable deadline for the transportation plan or TIP, and 

then while in the conformity lapse grace period also fails to meet an applicable deadline 

for the other document, there will only be one 12-month grace period, running from the 

date of the first missed deadline. 

Similarly, for example, an area that misses its four-year conformity determination clock 

gets a 12-month grace period from that point. If during the grace period, the area misses 

a two-year clock running because new budgets were established, the grace period 

continues to run from the date of the first missed deadline. 

6.8 What happens if an area misses the two-year trigger to redetermine conformity 

after an EPA action establishing a new motor vehicle emissions budget?

If, after two years, an area is unable to demonstrate conformity using the new emissions 

budget, and the transportation plan and STIP/TIP are still in effect, then the area will 

enter the conformity lapse grace period. The area can continue advancing projects in the 

existing transportation planning documents as long as project-level conformity 

requirements are met. 

6.9 If a nonattainment or maintenance area has subarea budgets and one subarea is 

in a lapse grace period, can other subareas make conformity determinations?

Yes, if an area has subarea budgets and one subarea is in a lapse grace period, other 

subareas can continue to make conformity determinations because the subarea in the 

lapse grace period does not enter a conformity lapse until the end of the 12-month grace 

period. 

33 
6.10 What happens at the end of the 12-month conformity lapse grace period?

A conformity lapse will occur if an area is unable to demonstrate conformity of its 

transportation plan and TIP at the end of the grace period. The restrictions on the types 

of projects that can proceed during a conformity lapse did not change with SAFETEALU. Please see the joint guidance memorandum issued by FHWA and FTA in January 

2002 (http://www.fhwa.dot.gov/environment/conformity/con_guid.htm) and the April 9, 

2003, FTA revised procedures for a conformity lapse 

(http://www.fhwa.dot.gov/environment/conformity/ftalapse.htm) for more information 

about advancing projects during a conformity lapse. 

6.11 Can project-level conformity be determined and final environmental 

documents be approved during the conformity lapse grace period?

Yes. Records of decision, FONSIs, and CEs may be approved during the grace period. 

Projects must meet all applicable project-level conformity requirements, including any 

required hot-spot analyses, and must come from the previously conforming transportation 

plan and TIP. In donut areas, projects must have been included in the regional emissions 

analysis supporting the previously conforming transportation plan and TIP of the 

associated MPO. 

6.12 Can regionally significant non-federal projects be approved during the grace 

period?

Yes. However, the project must have been included in the regional emissions analysis 

supporting the previously conforming transportation plan and TIP. 

34 
Section 7: Inclusion of Criteria and Procedures in SIP

SAFETEA-LU section 6011(f)(4) reads as follows:

(f) Conforming Amendments.--Section 176(c)(4) of the Clean Air Act (42 U.S.C. 

7506(c)(4)) (as amended by subsection (b)) is amended-- 

(4) by striking subparagraph (E) (as redesignated by paragraph (1)) and inserting 

the following: 

``(E) Inclusion of criteria and procedures in sip.--Not later than 2 

years after the date of enactment of the SAFETEA-LU the procedures 

under subparagraph (A) shall include a requirement that each state 

include in the state implementation plan criteria and procedures for 

consultation required by subparagraph (D)(i), and enforcement and 

enforceability (pursuant to sections 93.125(c) and 93.122(a)(4)(ii) of 

title 40, Code of Federal Regulations) in accordance with the 

Administrator's criteria and procedures for consultation, enforcement 

and enforceability.''. 

7.1 What does this provision do?

This provision streamlines the requirements for state conformity SIPs.8 Prior to 

SAFETEA-LU being signed into law, states were required to address all of the federal 

conformity rule’s provisions in their conformity SIPs. Most of the sections of the federal 

rule were required to be copied verbatim from the federal rule into a state’s SIP, as 

previously required under 40 CFR 51.390(d). States were also required to tailor all or 

portions of the following three sections of the federal rule to meet their state’s individual 

circumstances: 

• 40 CFR 93.105, which addresses consultation procedures; 

• 40 CFR 93.122(a)(4)(ii), which addresses written commitments to control 

measures that are not included in an MPO’s plan and TIP that must be obtained 

prior to a conformity determination and the requirement that such commitments 

must be fulfilled; and 

• 40 CFR 93.125(c), which addresses written commitments to mitigation measures 

that must be obtained prior to a project-level conformity determination, and the 

requirement that project sponsors must comply with such commitments. 

Now, under SAFETEA-LU, states are required to address and tailor only these three 

sections of the conformity rule in their conformity SIPs. In general, states are no longer 

required to submit conformity SIP revisions that address the other sections of the 

conformity rule, except for limited cases that are described below. 

7.2 When does this provision apply?

This provision took effect on August 10, 2005, when SAFETEA-LU was signed into law. 

8

 Conformity SIPs are different from control strategy SIPs or maintenance plans, as they only include state 

conformity procedures and not motor vehicle emissions budgets or air quality demonstrations. 

35 
7.3 Are any new conformity SIP deadlines created by SAFETEA-LU?

No. SAFETEA-LU does not create any new deadlines for conformity SIPs. Any 

nonattainment or maintenance area that has missed earlier deadlines to submit conformity 

SIP revisions (e.g., after previous conformity rulemakings, or new nonattainment 

designations) continues to be subject to these previous deadlines, but only in regard to the 

three provisions now required under SAFETEA-LU. 

In addition, states are required to submit a conformity SIP revision due to any future 

rulemaking that substantively changes the three specified sections in the current 

conformity rule. For example, SAFETEA-LU requires EPA to complete a rulemaking 

reflecting all SAFETEA-LU conformity provisions by August 10, 2007. If EPA 

substantively changes any of the three specified provisions in that rulemaking, a 

conformity SIP revision would be required one year from the publication date of the 

SAFETEA-LU final conformity rule (40 CFR 51.390(a)). 

7.4 How does SAFETEA-LU impact areas that have not previously submitted or 

approved conformity SIPs? 

States that do not currently have submitted or approved conformity SIPs are only 

required to address the three provisions listed in SAFETEA-LU in their conformity SIPs 

according to any existing conformity SIP deadline, as described in the previous question. 

Once a state has an approved conformity SIP that addresses only the three sections that 

SAFETEA-LU requires, the state would only revise its conformity SIP if either EPA 

revises the conformity rule and it affects one of these sections, or the state elects to revise 

how it addresses one of these three provisions. Any future changes to the federal 

conformity rules beyond these three provisions would take effect immediately in all states 

that have only these three provisions in their approved conformity SIP. 

7.5 How does SAFETEA-LU impact areas that have previously submitted or 

approved conformity SIPs? 

States that have previously approved conformity SIPs that decide to eliminate the 

provisions that are no longer mandatory will need to go through a formal SIP revision

process to eliminate those provisions from their SIPs. EPA will have to conduct 

rulemaking to approve the changes to the states’ conformity SIPs. EPA will act 

expeditiously to approve these revisions. EPA will consider using either parallel 

processing or direct final approval to expedite the approval of such SIP revisions. Such 

SIP revisions should not be controversial since the provisions are no longer required by 

the Clean Air Act as amended by SAFETEA-LU.

A state with a previously approved conformity SIP may decide to retain all or some of the 

federal rule in its SIP. In such a case, the state should be aware that the conformity 

determinations in the state continue to be governed by the state’s conformity SIP. Such a 

36 
state would need to revise its conformity SIP when EPA makes changes to the federal 

rule in order to have those changes apply in the state. For more information please refer 

to EPA’s November 2004 Conformity SIP Guidance which is found at: 

http://www.epa.gov/otaq/transp/conform/policy.htm. 

In addition, some states have submitted conformity SIPs to EPA for approval, but EPA 

may not have acted on these revisions yet. These states may write their EPA regional 

office and request that EPA approve only the three provisions that are required to be 

included in their SIPs and that EPA take no action on the remainder of the submission. 

States could also leave the full conformity SIP pending before EPA for rulemaking 

action, however as noted above if EPA approves the full SIP states would need 

subsequent SIP revisions to coordinate their SIPs with any future changes to the federal 

conformity rules. 

7.6 How does this provision affect the 12-month conformity SIP submission clocks 

that were started by the July 1, 2004, and May 6, 2005, final conformity rules?

EPA and DOT believe that those clocks have been eliminated because those rulemakings 

did not contain any substantive revisions to any of the three sections of the rule that states 

are now required to address in their SIPs. 

It should be noted that both final rules made very minor changes to section 93.105. The 

July 2004 final rule changed a reference to a later section of the conformity rule and the 

May 2005 rule contained a technical correction to a reference to a section of DOT’s 

regulations. EPA and DOT do not believe that either of those changes is significant 

enough by itself to warrant states being required to update their conformity SIPs within 

12 months of the publication of those final rules. 

7.7 How does this provision affect EPA’s November 2004 conformity SIP guidance?

EPA intends to revise this guidance in the near future in order to make it consistent with 

the revised conformity SIP requirements contained in SAFETEA-LU. 

7.8 Can states continue to include provisions in their SIPs that are more stringent 

than the federal rule?

Yes, states can continue to include provisions in their conformity SIPs that are more 

stringent than the federal rule as long as they apply equally to federal and non-federal 

entities, pursuant to 40 CFR 51.390(a). This aspect of the current conformity regulation 

is not affected by SAFETEA-LU. 

37 
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38 
APPENDIX 

Clean Air Act Section 176 

As Amended by SAFETEA-LU

NOTES: 

This appendix includes Clean Air Act section 176 as amended by SAFETEA-LU. 

EPA and US DOT are providing this document for informational purposes only as 

an official version of the revised section is not yet available. 

The revised portions of this section of the Clean Air Act are shown in bold. 

From the U.S. Code Online via GPO Access 

[wais.access.gpo.gov] 

[Laws in effect as of January 7, 2003] 

[Document not affected by Public Laws enacted between 

 January 7, 2003 and February 12, 2003] 

[CITE: 42USC7506] 

TITLE 42--THE PUBLIC HEALTH AND WELFARE 

CHAPTER 85--AIR POLLUTION PREVENTION AND CONTROL 

SUBCHAPTER I--PROGRAMS AND ACTIVITIES 

Part D--Plan Requirements for Nonattainment Areas 

subpart 1--nonattainment areas in general 

Sec. 7506. Limitations on certain Federal assistance 

(a), (b) Repealed. Pub. L. 101-549, title I, Sec. 110(4), Nov. 15, 1990, 

 104 Stat. 2470 

(c) Activities not conforming to approved or promulgated plans 

 (1) 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, 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-- 

39 
 (A) conformity to an implementation plan's purpose of eliminating or reducing the 

severity and number of violations of the national ambient air quality standards and 

achieving expeditious attainment of such standards; and 

 (B) that such activities 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 emission 

reductions or other milestones in any area. 

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. 

 (2) Any transportation plan or program developed pursuant to title 23 or chapter 53 of 

title 49 shall implement the transportation provisions of any applicable implementation 

plan approved under this chapter applicable to all or part of the area covered by such 

transportation plan or program. No Federal agency may approve, accept or fund any 

transportation plan, program or project unless such plan, program or project has been 

found to conform to any applicable implementation plan in effect under this chapter. In 

particular-- 

 (A) no transportation plan or transportation improvement program may be adopted 

by a metropolitan planning organization designated under title 23 or chapter 53 of title 

49, or be found to be in conformity by a metropolitan planning organization until a final 

determination has been made that emissions expected from implementation of such plans 

and programs are consistent with estimates of emissions from motor vehicles and 

necessary emissions reductions contained in the applicable implementation plan, and that 

the plan or program will conform to the requirements of paragraph (1)(B); 

 (B) no metropolitan planning organization or other recipient of funds under title 23

or chapter 53 of title 49 shall adopt or approve a transportation improvement program of 

projects until it determines that such program provides for timely implementation of 

transportation control measures consistent with schedules included in the applicable 

implementation plan; 

 (C) a transportation project may be adopted or approved by a metropolitan planning 

organization or any recipient of funds designated under title 23 or chapter 53 of title 49, 

or found in conformity by a metropolitan planning organization or approved, accepted, or 

funded by the Department of Transportation only if it meets either the requirements of 

subparagraph (D) or the following requirements-- 

 (i) such a project comes from a conforming plan and program; 

 (ii) the design concept and scope of such project have not changed significantly 

since the conformity finding regarding the plan and program from which the project 

derived; and 

 (iii) the design concept and scope of such project at the time of the conformity 

determination for the program was adequate to determine emissions. 

 (D) Any project not referred to in subparagraph (C) shall be treated as conforming to 

the applicable implementation plan only if it is demonstrated that the projected emissions 

from such project, when considered together with emissions projected for the conforming 

40 
transportation plans and programs within the nonattainment area, do not cause such plans 

and programs to exceed the emission reduction projections and schedules assigned to 

such plans and programs in the applicable implementation plan. 

(E) The appropriate metropolitan planning organization shall redetermine 

conformity of existing transportation plans and programs not later than 2 years 

after the date on which the Administrator— 

(i) finds a motor vehicle emissions budget to be adequate in accordance with 

section 93.118(e)(4) of title 40, Code of Federal Regulations (as in effect on October 

1, 2004); 

(ii) approves an implementation plan that establishes a motor vehicle 

emissions budget if that budget has not yet been determined to be adequate in 

accordance with clause (i); or 

(iii) promulgates an implementation plan that establishes or revises a motor 

vehicle emissions budget. 

 (3) Until such time as the implementation plan revision referred to in paragraph (4)(C) 

is approved, conformity of such plans, programs, and projects will be demonstrated if--

 (A) the transportation plans and programs-- 

 (i) are consistent with the most recent estimates of mobile source emissions; 

 (ii) provide for the expeditious implementation of transportation control measures 

in the applicable implementation plan; and 

 (iii) with respect to ozone and carbon monoxide nonattainment areas, contribute 

to annual emissions reductions consistent with sections 7511a(b)(1) and 7512a(a)(7) of 

this title; and 

 (B) the transportation projects--

 (i) come from a conforming transportation plan and program as defined in 

subparagraph (A) or for 12 months after November 15, 1990, from a transportation 

program found to conform within 3 years prior to November 15, 1990; and 

 (ii) in carbon monoxide nonattainment areas, eliminate or reduce the severity and 

number of violations of the carbon monoxide standards in the area substantially affected 

by the project. 

 With regard to subparagraph (B)(ii), such determination may be made as part of either 

the conformity determination for the transportation program or for the individual project 

taken as a whole during the environmental review phase of project development. 

(4) CRITERIA AND PROCEDURES FOR DETERMINING CONFORMITY

(A) IN GENERAL—The Administrator shall promulgate, and periodically 

update, criteria and procedures for determining conformity (except in the case of 

transportation plans, programs, and projects) of, and for keeping the Administrator 

informed about, the activities referred to in paragraph (1). 

(B) TRANSPORTATION PLANS, PROGRAMS, AND PROJECTS–The Administrator, 

with the concurrence of the Secretary of Transportation, shall promulgate, and 

periodically update, criteria and procedures for demonstrating and assuring conformity 

in the case of transportation plans, programs, and projects. 

(C ) CIVIL ACTION TO COMPEL PROMULGATION—A civil action may be brought 

against the Administrator and the Secretary of Transportation under section 7604 of this 

title to compel promulgation of such criteria and procedures and the Federal district court 

shall have jurisdiction to order such promulgation. 

41 
(D) The procedures and criteria shall, at a minimum-- 

 (i) address the consultation procedures to be undertaken by metropolitan planning 

organizations and the Secretary of Transportation with State and local air quality agencies 

and State departments of transportation before such organizations and the Secretary make 

conformity determinations; 

(ii) address the appropriate frequency for making conformity 

determinations, but; the frequency for making conformity determinations on 

updated transportation plans and programs shall be every 4 years, except in a case 

in which— 

(I) the metropolitan planning organization elects to update a 

transportation plan or program more frequently; or 

(II) the metropolitan planning organization is required to determine 

conformity in accordance with paragraph (2)(E); and 

 (iii) address how conformity determinations will be made with respect to 

maintenance plans. 

(E). INCLUSION OF CRITERIA AND PROCEDURES IN SIP.—Not later 

than 2 years after the date of enactment of the SAFETEA–LU the procedures under 

subparagraph (A) shall include a requirement that each State include in the State 

implementation plan criteria and procedures for consultation required by 

subparagraph (D)(i), and enforcement and enforceability (pursuant to sections 

93.125(c) and 93.122(a)(4)(ii) of title 40, Code of Federal Regulations) in accordance 

with the Administrator’s criteria and procedures for consultation, enforcement and 

enforceability.’’. 

(F) Compliance with the rules of the Administrator for determining the 

conformity of transportation plans, programs, and projects funded or approved under title 

23 or chapter 53 of title 49 to State or Federal implementation plans shall not be required 

for traffic signal synchronization projects prior to the funding, approval or 

implementation of such projects. The supporting regional emissions analysis for any 

conformity determination made with respect to a transportation plan, program, or project 

shall consider the effect on emissions of any such project funded, approved, or 

implemented prior to the conformity determination. 

 (5) Applicability.--This subsection shall apply only with respect to— 

(A) a nonattainment area and each pollutant for which the area is designated as 

a nonattainment area; and 

(B) an area that was designated as a nonattainment area but that was later 

redesignated by the Administrator as an attainment area and that is required to develop a 

maintenance plan under section 7505a of this title with respect to the specific pollutant 

for which the area was designated nonattainment. 

 (6) Notwithstanding paragraph 5,\1\ this subsection shall not apply with respect to an 

area designated nonattainment under section 7407(d)(1) of this title until 1 year after that 

area is first designated nonattainment for a specific national ambient air quality standard. 

This paragraph only applies with respect to the national ambient air quality standard for 

which an area is newly designated nonattainment and does not affect the area's 

requirements with respect to all other national ambient air quality standards for which the 

area is designated nonattainment or has been redesignated from nonattainment to 

attainment with a maintenance plan pursuant to section 7505a \2\ of this title (including 

42 
any pre-existing national ambient air quality standard for a pollutant for which a new or 

revised standard has been issued). 

(7) CONFORMITY HORIZON FOR TRANSPORTATION PLANS.— 

 (A) IN GENERAL.—Each conformity determination required under this 

section for a transportation plan under section 134(i) of title 23, United States Code, 

or section 5303(i) of title 49, United States Code, shall require a demonstration of 

conformity for the period ending on either the final year of the transportation plan, 

or at the election of the metropolitan planning organization, after consultation with 

the air pollution control agency and solicitation of public comments and 

consideration of such comments, the longest of the following periods: 

(i) The first 10-year period of any such transportation plan. 

(ii) The latest year in the implementation plan applicable to the area that 

contains a motor vehicle emission budget. 

(iii) The year after the completion date of a regionally significant project if 

the project is included in the transportation improvement program or the project 

requires approval before the subsequent conformity determination. 

(B) REGIONAL EMISSIONS ANALYSIS.—The conformity determination 

shall be accompanied by a regional emissions analysis for the last year of the 

transportation plan and for any year shown to exceed emission budgets by a prior 

analysis, if such year extends beyond the applicable period as determined under 

subparagraph (A). 

(C) EXCEPTION.—In any case in which an area has a revision to an 

implementation plan under section 175A(b) and the Administrator has found the 

motor vehicles emissions budgets from that revision to be adequate in accordance 

with section 93.118(e)(4) of title 40, Code of Federal Regulations (as in effect on 

October 1, 2004), or has approved the revision, the demonstration of conformity at 

the election of the metropolitan planning organization, after consultation with the 

air pollution control agency and solicitation of public comments and consideration 

of such comments, shall be required to extend only through the last year of the 

implementation plan required under section 175A(b). 

(D) EFFECT OF ELECTION.—Any election by a metropolitan planning 

organization under this paragraph shall continue in effect until the metropolitan

planning organization elects otherwise. 

(E) AIR POLLUTION CONTROL AGENCY DEFINED.—In this paragraph, 

the term ‘air pollution control agency’ means an air pollution control agency (as 

defined in section 302(b)) that is responsible for developing plans or controlling air 

pollution within the area covered by a transportation plan. 

(8) SUBSTITUTION OF TRANSPORTATION CONTROL MEASURES.— 

(A) IN GENERAL.—Transportation control measures that are specified in an 

implementation plan may be replaced or added to the implementation plan with 

alternate or additional transportation control measures 

(i) if the substitute measures achieve equivalent or greater emissions 

reductions than the control measure to be replaced, as demonstrated with an 

emissions impact analysis that is consistent with the current methodology used for 

evaluating the replaced control measure in the implementation plan; 

(ii) if the substitute control measures are implemented— 

43 
(I) in accordance with a schedule that is consistent with the schedule 

provided for control measures in the implementation plan; or 

(II) if the implementation plan date for implementation of the control 

measure to be replaced has passed, as soon as practicable after the implementation

plan date but not later than the date on which emission reductions are necessary to 

achieve the purpose of the implementation plan; 

(iii) if the substitute and additional control measures are accompanied with 

evidence of adequate personnel and funding and authority under State or local law

to implement, monitor, and enforce the control measures; 

(iv) if the substitute and additional control measures were developed through 

a collaborative process that included— 

(I) participation by representatives of all affected jurisdictions 

(including local air pollution control agencies, the State air 

pollution control agency, and State and local transportation 

agencies); 

(II)consultation with the Administrator; and 

(III) reasonable public notice and opportunity for comment; and 

(v) if the metropolitan planning organization, State air pollution control 

agency, and the Administrator concur with the equivalency of the substitute or 

additional control measures. 

(B) ADOPTION.— 

(i) Concurrence by the metropolitan planning organization, State air 

pollution control agency and the Administrator as required by subparagraph (A)(v) 

shall constitute adoption of the substitute or additional control measures so long as 

the requirements of subparagraphs (A)(i), (A)(ii), (A)(iii) and (A)(iv) are met. 

(ii) Once adopted, the substitute or additional control measures become, by 

operation of law, part of the State implementation plan and become federally 

enforceable. 

(iii) Within 90 days of its concurrence under subparagraph (A)(v), the State 

air pollution control agency shall submit the substitute or additional control 

measure to the Administrator for incorporation in the codification of the applicable 

implementation plan. Notwithstanding any other provision of this Act, no additional 

State process shall be necessary to support such revision to the applicable plan. 

(C) NO REQUIREMENT FOR EXPRESS PERMISSION.—The substitution or 

addition of a transportation control measure in accordance with this paragraph and 

the funding or approval of such a control measure shall not be contingent on the 

existence of any provision in the applicable implementation plan that expressly 

permits such a substitution or addition. 

(D) NO REQUIREMENT FOR NEW CONFORMITY DETERMINATION.— 

The substitution or addition of a transportation control measure in accordance with 

this paragraph shall not require— 

(i) a new conformity determination for the transportation plan; or 

(ii) a revision of the implementation plan. 

(E) CONTINUATION OF CONTROL MEASURE BEING REPLACED.—A 

control measure that is being replaced by a substitute control measure under this

44 
paragraph shall remain in effect until the substitute control measure is adopted by 

the State pursuant to subparagraph (B). 

(F) EFFECT OF ADOPTION.—Adoption of a substitute control measure shall 

constitute rescission of the previously applicable control measure. 

 (9) LAPSE OF CONFORMITY.—If a conformity determination required under 

this subsection for a transportation plan under section 134(i) of title 23, United 

States Code, or section 5303(i) of title 49, United States Code, or a transportation 

improvement program under section 134(j) of such title 23 or under section 5303(j) 

of such title 49 is not made by the applicable deadline and such failure is not 

corrected by additional measures to either reduce motor vehicle emissions sufficient 

to demonstrate compliance with the requirements of this subsection within 12 

months after such deadline or other measures sufficient to correct such failures, the 

transportation plan shall lapse. 

 (10) LAPSE.—In this subsection, the term ‘lapse’ means that the conformity 

determination for a transportation plan or transportation improvement program 

has expired, and thus there is no currently conforming transportation plan or 

transportation improvement program.’’. 

--------------------------------------------------------------------------- 

 \1\ So in original. Probably should be ``paragraph (5),''. 

 \2\ See References in Text note below. 

--------------------------------------------------------------------------- 

(d) Priority of achieving and maintaining national primary ambient air quality standards 

 Each department, agency, or instrumentality of the Federal Government having 

authority to conduct or support any program with air-quality related transportation 

consequences shall give priority in the exercise of such authority, consistent with 

statutory requirements for allocation among States or other jurisdictions, to the 

implementation of those portions of plans prepared under this section to achieve and 

maintain the national primary ambient air-quality standard. This 

paragraph extends to, but is not limited to, authority exercised under chapter 53 of title 

49, title 23, and the Housing and Urban Development Act. 

(July 14, 1955, ch. 360, title I, Sec. 176, as added Pub. L. 95-95, title I, Sec. 129(b), Aug. 

7, 1977, 91 Stat. 749; amended Pub. L. 95-190, Sec. 14(a)(59), Nov. 16, 1977, 91 Stat. 

1403; Pub. L. 101-549, title I, Secs. 101(f), 110(4), Nov. 15, 1990, 104 Stat. 2409, 2470; 

Pub. L. 104-59, title III, Sec. 305(b), Nov. 28, 1995, 109 Stat. 580; Pub. L.104-260, Sec. 

1, Oct. 9, 1996, 110 Stat. 3175; Pub. L. 106-377, Sec. 1(a)(1) [title III], Oct. 27, 2000,

114 Stat. 1441, 1441A-44.) 

 References in Text 

 Section 7505a of this title, referred to in subsec. (c)(6), was in the original ``section 

175(A)'' and was translated as reading ``section 175A'', meaning section 175A of act July 

45 
14, 1955, which is classified to section 7505a of this title, to reflect the probable intent of 

Congress. 

 The Housing and Urban Development Act, referred to in subsec. (d), may be the name

for a series of acts sharing the same name but enacted in different years by Pub. L. 89-

117, Aug. 10, 1965, 79 Stat. 451; Pub. L. 90-448, Aug. 1, 1968, 82 Stat. 476; Pub. L. 91-

152, Dec. 24, 1969, 83 

Stat. 379; and Pub. L. 91-609, Dec. 31, 1970, 84 Stat. 1770, respectively. For complete 

classification of these Acts to the Code, see Short Title notes set out under section 1701 

of Title 12, Banks and Banking, and Tables. 

 Codification 

 In subsecs. (c)(2) and (d), ``chapter 53 of title 49'' substituted for ``the Urban Mass 

Transportation Act [49 App. U.S.C. 1601 et seq.]'' and in subsec. (c)(4)(D) substituted for 

``Federal Transit Act'' on authority of Pub. L. 103-272, Sec. 6(b), July 5, 1994, 108 Stat. 

1378 

(the first section of which enacted subtitles II, III, and V to X of Title 49, Transportation), 

and of Pub. L. 102-240, title III, Sec. 3003(b), Dec. 18, 1991, 105 Stat. 2088, which 

provided that 

references in laws to the Urban Mass Transportation Act of 1964 be deemed to be 

references to the Federal Transit Act. 

 Amendments 

 2000--Subsec. (c)(6). Pub. L. 106-377 added par. (6). 

 1996--Subsec. (c)(4)(D). Pub. L. 104-260 added subpar. (D). 

 1995--Subsec. (c)(5). Pub. L. 104-59 added par. (5). 

 1990--Subsecs. (a), (b). Pub. L. 101-549, Sec. 110(4), struck out subsec. (a) which 

related to approval of projects or award of grants, and subsec. (b) which related to 

implementation of approved or promulgated plans. 

 Subsec. (c). Pub. L. 101-549, Sec. 101(f), designated existing provisions as par. (1), 

struck out ``(1)'', ``(2)'', ``(3)'', and ``(4)'' before ``engage in'', ``support in'', ``license or'',

and ``approve, any'', respectively, substituted ``conform to an implementation plan after 

it'' for ``conform to a plan after it'', ``conform to an implementation plan approved'' for

``conform to a plan approved'', and ``conformity to such an implementation plan shall''

for ``conformity to such a plan shall'', inserted ``Conformity to an implementation plan 

means--'' followed immediately by subpars. (A) and 

(B) and closing provisions relating to determination of conformity being based on recent 

estimates of emissions and the determination of such estimates, and added pars. (2) to (4). 

 1977--Subsec. (a)(1). Pub. L. 95-190 inserted ``national'' before ``primary''. 

46