Transportation Conformity Regulations

Updated March 2010
EPA-420-B-10-006

March 2010

Transportation and Regional Programs Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

Transportation Conformity Regulations

Updated March 2010

Notes: 

This document includes the current transportation conformity rule that 

reflects all transportation conformity rulemakings promulgated by EPA as of 

March 2010, including the PM Amendments final rulemaking (75 FR 14260). 

EPA intends to update this reference document upon publication of any final 

transportation conformity rules.

This document is for informational purposes only, and you should not use the 

page numbers of this document for citation purposes. This document does 

not supersede existing conformity regulations that currently apply for conformity 

determinations. 

.
§51.390(a) – (c) 

TITLE 40--PROTECTION OF 

ENVIRONMENT 

CHAPTER I--ENVIRONMENTAL 

PROTECTION AGENCY 

PART 51--REQUIREMENTS FOR 

PREPARATION, ADOPTION, AND 

SUBMITTAL OF IMPLEMENTATION 

PLANS 

Subpart T--Conformity to State or Federal 

Implementation Plans of Transportation 

Plans, Programs, and Projects Developed, 

Funded or Approved Under Title 23 U.S.C. 

or the Federal Transit Laws 

§51.390 Implementation plan revision. 

(a) Purpose and applicability. The federal 

conformity rules under part 93, subpart A, of 

this chapter, in addition to any existing 

applicable state requirements, establish the 

conformity criteria and procedures necessary 

to meet the requirements of Clean Air Act 

section 176(c) until such time as EPA 

approves the conformity implementation plan 

revision required by this subpart. A state with 

an area subject to this subpart and part 93, 

subpart A, of this chapter must submit to EPA 

a revision to its implementation plan which 

contains criteria and procedures for DOT, 

MPOs and other state or local agencies to 

assess the conformity of transportation plans, 

programs, and projects, consistent with this 

subpart and part 93, subpart A, of this chapter. 

The federal conformity regulations contained 

in part 93, subpart A, of this chapter would 

continue to apply for the portion of the 

requirements that the state did not include in 

its conformity implementation plan and the 

portion, if any, of the state's conformity 

provisions that is not approved by EPA. In 

addition, any previously applicable 

implementation plan conformity requirements 

remain enforceable until the state submits a 

revision to its applicable implementation plan 

to specifically remove them and that revision 

is approved by EPA. 

(b) Conformity implementation plan content. 

To satisfy the requirements of Clean Air Act 

section 176(c)(4)(E), the implementation plan 

revision required by this section must include 

the following three requirements of part 93, 

subpart A, of this chapter: §§93.105, 

93.122(a)(4)(ii), and 93.125(c). A state may 

elect to include any other provisions of part 

93, subpart A. If the provisions of the 

following sections of part 93, subpart A, of 

this chapter are included, such provisions must 

be included in verbatim form, except insofar 

as needed to clarify or to give effect to a stated 

intent in the revision to establish criteria and 

procedures more stringent than the 

requirements stated in this chapter: §§93.101, 

93.102, 93.103, 93.104, 93.106, 93.109, 

93.110, 93.111, 93.112, 93.113, 93.114, 

93.115, 93.116, 93.117, 93.118, 93.119, 

93.120, 93.121, 93.126, and 93.127. A state's 

conformity provisions may contain criteria 

and procedures more stringent than the 

requirements described in this subpart and part 

93, subpart A, of this chapter only if the state's 

conformity provisions apply equally to nonfederal as well as federal entities. 

(c) Timing and approval. A state must submit 

this revision to EPA by November 25, 1994 or 

within 12 months of an area's redesignation 

from attainment to nonattainment, if the state 

has not previously submitted such a revision. 

The state must also revise its conformity 

implementation plan within 12 months of the 

date of publication of any final amendments to 

§§93.105, 93.122(a)(4)(ii), and 93.125(c), as 

appropriate. Any other portions of part 93, 

subpart A, of this chapter that the state has 

included in its conformity implementation 

plan and EPA has approved must be revised in 

the state’s implementation plan and submitted 

to EPA within 12 months of the date of 

1 
§51.390(c) ● §93 Table of Contents 

publication of any final amendments to such 

sections. EPA will provide DOT with a 30-

day comment period before taking action to 

approve or disapprove the submission. In 

order for EPA to approve the implementation 

plan revision submitted to EPA under this 

subpart, the plan revision must address and 

give full legal effect to the following three 

requirements of part 93, subpart A: §§93.105, 

93.122(a)(4)(ii), and 93.125(c). Any other 

provisions that are incorporated into the 

conformity implementation plan must also be 

done in a manner that gives them full legal 

effect. Following EPA approval of the state 

conformity provisions (or a portion thereof) in 

a revision to the state’s conformity 

implementation plan, conformity 

determinations will be governed by the 

approved (or approved portion of the) state 

criteria and procedures as well as any 

applicable portions of the federal conformity 

rules that are not addressed by the approved 

conformity SIP. 

PART 93 – DETERMINING 

CONFORMITY OF FEDERAL ACTIONS 

TO STATE OR FEDERAL 

IMPLEMENTATION PLANS 

Subpart A—Conformity to State or Federal 

Implementation Plans of Transportation 

Plans, Programs, and Projects Developed, 

Funded or Approved Under Title 23 U.S.C. 

or the Federal Transit Laws 

§93.100 Purpose. 

§93.101 Definitions. 

§93.102 Applicability. 

§93.103 Priority. 

§93.104 Frequency of conformity 

determinations. 

§93.105 Consultation. 

§93.106 Content of transportation plans and 

timeframe of conformity determinations. 

. 

§93.107 Relationship of transportation plan 

and TIP conformity with the NEPA 

process. 

§93.108 Fiscal constraints for transportation 

plans and TIPs. 

§93.109 Criteria and procedures for 

determining conformity of transportation 

plans, programs, and projects: General. 

§93.110 Criteria and procedures: Latest 

planning assumptions. 

§93.111 Criteria and procedures: Latest 

emissions model. 

§93.112 Criteria and procedures: 

Consultation. 

§93.113 Criteria and procedures: Timely 

implementation of TCMs. 

§93.114 Criteria and procedures: Currently 

conforming transportation plan and TIP. 

§93.115 Criteria and procedures: Projects 

from a transportation plan and TIP. 

§93.116 Criteria and procedures: Localized 

CO, PM10, and PM2.5 violations (hotspots). 

§93.117 Criteria and procedures: Compliance 

with PM10 and PM2.5 control measures. 

§93.118 Criteria and procedures: Motor 

vehicle emissions budget. 

§93.119 Criteria and procedures: Interim 

emissions in areas without motor vehicle 

emissions budgets. 

§93.120 Consequences of control strategy 

implementation plan failures. 

§93.121 Requirements for adoption or 

approval of projects by other recipients of 

funds designated under title 23 U.S.C. or 

the Federal Transit Laws. 

§93.122 Procedures for determining regional 

transportation-related emissions. 

§93.123 Procedures for determining localized 

CO, PM10, and PM2.5 concentrations (hotspot analysis). 

§93.124 Using the motor vehicle emissions 

budget in the applicable implementation 

plan (or implementation plan submission) 

2 
§93 Table of Contents ● §93.101 

§93.125 Enforceability of design concept and 

scope and project-level mitigation and 

control measures. 

§93.126 Exempt projects. 

§93.127 Projects exempt from regional 

emissions analyses. 

§93.128 Traffic signal synchronization 

projects. 

§93.129 Special exemptions from conformity 

requirements for pilot program areas. 

§ 93.100 Purpose. 

The purpose of this subpart is to implement 

section 176(c) of the Clean Air Act (CAA), as 

amended (42 U.S.C. 7401 et seq. ), and the 

related requirements of 23 U.S.C. 109(j), with 

respect to the conformity of transportation 

plans, programs, and projects which are 

developed, funded, or approved by the United 

States Department of Transportation (DOT), 

and by metropolitan planning organizations 

(MPOs) or other recipients of funds under title 

23 U.S.C. or the Federal Transit Laws (49 

U.S.C. Chapter 53). This subpart sets forth 

policy, criteria, and procedures for 

demonstrating and assuring conformity of 

such activities to an applicable 

implementation plan developed pursuant to 

section 110 and Part D of the CAA. 

§ 93.101 Definitions. 

Terms used but not defined in this subpart 

shall have the meaning given them by the 

CAA, titles 23 and 49 U.S.C., other 

Environmental Protection Agency (EPA) 

regulations, or other DOT regulations, in that 

order of priority. 

Applicable implementation plan is defined in 

section 302(q) of the CAA and means the 

portion (or portions) of the implementation 

plan, or most recent revision thereof, which 

has been approved under section 110, or 

promulgated under section 110(c), or 

promulgated or approved pursuant to 

regulations promulgated under section 301(d) 

and which implements the relevant 

requirements of the CAA. 

CAA means the Clean Air Act, as amended 

(42 U.S.C. 7401 et seq. ). 

Cause or contribute to a new violation for a 

project means: 

(1) To cause or contribute to a new violation 

of a standard in the area substantially affected 

by the project or over a region which would 

otherwise not be in violation of the standard 

during the future period in question, if the 

project were not implemented; or 

(2) To contribute to a new violation in a 

manner that would increase the frequency or 

severity of a new violation of a standard in 

such area. 

Clean data means air quality monitoring data 

determined by EPA to meet the requirements 

of 40 CFR part 58 that indicate attainment of 

the national ambient air quality standard. 

Control strategy implementation plan revision 

is the implementation plan which contains 

specific strategies for controlling the 

emissions of and reducing ambient levels of 

pollutants in order to satisfy CAA 

requirements for demonstrations of reasonable 

further progress and attainment (including 

implementation plan revisions submitted to 

satisfy CAA sections 172(c), 182(b)(1), 

182(c)(2)(A), 182(c)(2)(B), 187(a)(7), 187(g), 

189(a)(1)(B), 189(b)(1)(A), and 189(d); 

sections 192(a) and 192(b), for nitrogen 

dioxide; and any other applicable CAA 

provision requiring a demonstration of 

reasonable further progress or attainment). 

Design concept means the type of facility 

identified by the project, e.g., freeway, 

expressway, arterial highway, grade-separated 

highway, reserved right-of-way rail transit, 

mixed-traffic rail transit, exclusive busway, 

etc. 

3 
§93.101 

Design scope means the design aspects which 

will affect the proposed facility's impact on 

regional emissions, usually as they relate to 

vehicle or person carrying capacity and 

control, e.g., number of lanes or tracks to be 

constructed or added, length of project, 

signalization, access control including 

approximate number and location of 

interchanges, preferential treatment for highoccupancy vehicles, etc. 

DOT means the United States Department of 

Transportation. 

Donut areas are geographic areas outside a 

metropolitan planning area boundary, but 

inside the boundary of a nonattainment or 

maintenance area that contains any part of a 

metropolitan area(s). These areas are not 

isolated rural nonattainment and maintenance 

areas. 

EPA means the Environmental Protection 

Agency. 

FHWA means the Federal Highway 

Administration of DOT. 

FHWA/FTA project, for the purpose of this 

subpart, is any highway or transit project 

which is proposed to receive funding 

assistance and approval through the FederalAid Highway program or the Federal mass 

transit program, or requires Federal Highway 

Administration (FHWA) or Federal Transit 

Administration (FTA) approval for some 

aspect of the project, such as connection to an 

interstate highway or deviation from 

applicable design standards on the interstate 

system. 

Forecast period with respect to a 

transportation plan is the period covered by 

the transportation plan pursuant to 23 CFR 

part 450. 

FTA means the Federal Transit Administration 

of DOT. 

Highway project is an undertaking to 

implement or modify a highway facility or 

highway-related program. Such an 

undertaking consists of all required phases 

necessary for implementation. For analytical 

purposes, it must be defined sufficiently to: 

(1) Connect logical termini and be of 

sufficient length to address environmental 

matters on a broad scope; 

(2) Have independent utility or 

significance, i.e., be usable and be a 

reasonable expenditure even if no additional 

transportation improvements in the area are 

made; and 

(3) Not restrict consideration of alternatives 

for other reasonably foreseeable transportation 

improvements. 

Horizon year is a year for which the 

transportation plan describes the envisioned 

transportation system according to §93.106. 

Hot-spot analysis is an estimation of likely 

future localized CO, PM10, and/or PM2.5 

pollutant concentrations and a comparison of 

those concentrations to the national ambient 

air quality standards. Hot-spot analysis 

assesses impacts on a scale smaller than the 

entire nonattainment or maintenance area, 

including, for example, congested roadway 

intersections and highways or transit 

terminals, and uses an air quality dispersion 

model to determine the effects of emissions on 

air quality. 

Increase the frequency or severity means to 

cause a location or region to exceed a standard 

more often or to cause a violation at a greater 

concentration than previously existed and/or 

would otherwise exist during the future period 

in question, if the project were not 

implemented. 

4 
§93.101 

Isolated rural nonattainment and maintenance 

areas are areas that do not contain or are not 

part of any metropolitan planning area as 

designated under the transportation planning 

regulations. Isolated rural areas do not have 

Federally required metropolitan transportation 

plans or TIPs and do not have projects that are 

part of the emissions analysis of any MPO's 

metropolitan transportation plan or TIP. 

Projects in such areas are instead included in 

statewide transportation improvement 

programs. These areas are not donut areas. 

Lapse means that the conformity 

determination for a transportation plan or TIP 

has expired, and thus there is no currently 

conforming transportation plan and TIP. 

Limited maintenance plan is a maintenance 

plan that EPA has determined meets EPA's 

limited maintenance plan policy criteria for a 

given NAAQS and pollutant. To qualify for a 

limited maintenance plan, for example, an 

area must have a design value that is 

significantly below a given NAAQS, and it 

must be reasonable to expect that a NAAQS 

violation will not result from any level of 

future motor vehicle emissions growth. 

Maintenance area means any geographic 

region of the United States previously 

designated nonattainment pursuant to the 

CAA Amendments of 1990 and subsequently 

redesignated to attainment subject to the 

requirement to develop a maintenance plan 

under section 175A of the CAA, as amended. 

Maintenance plan means an implementation 

plan under section 175A of the CAA, as 

amended. 

Metropolitan planning organization (MPO) 

means the policy board of an organization 

created as a result of the designation process 

in 23 U.S.C. 134(d). 

Milestone has the meaning given in CAA 

sections 182(g)(1) and 189(c) for serious and 

above ozone nonattainment areas and PM10 

nonattainment areas, respectively. For all 

other nonattainment areas, a milestone 

consists of an emissions level and the date on 

which that level is to be achieved as required 

by the applicable CAA provision for 

reasonable further progress towards 

attainment. 

Motor vehicle emissions budget is that portion 

of the total allowable emissions defined in the 

submitted or approved control strategy 

implementation plan revision or maintenance 

plan for a certain date for the purpose of 

meeting reasonable further progress 

milestones or demonstrating attainment or 

maintenance of the NAAQS, for any criteria 

pollutant or its precursors, allocated to 

highway and transit vehicle use and emissions. 

National ambient air quality standards 

(NAAQS) are those standards established 

pursuant to section 109 of the CAA. 

(1) 1-hour ozone NAAQS means the 1-hour 

ozone national ambient air quality standard 

codified at 40 CFR 50.9. 

(2) 8-hour ozone NAAQS means the 8-hour 

ozone national ambient air quality standard 

codified at 40 CFR 50.10. 

(3) 24-hour PM10 NAAQS means the 24-

hour PM10 national ambient air quality 

standard codified at 40 CFR 50.6. 

(4) 1997 PM2.5 NAAQS means the PM2.5 

national ambient air quality standard codified 

at 40 CFR 50.7. 

(5) 2006 PM2.5 NAAQS means the 24-hour 

PM2.5 national ambient air quality standard 

codified at 40 CFR 50.13. 

(6) Annual PM10 NAAQS means the annual 

PM10 national ambient air quality standard 

that EPA revoked on December 18, 2006. 

5 
§93.101 

NEPA means the National Environmental 

Policy Act of 1969, as amended (42 U.S.C. 

4321 et seq.). 

NEPA process completion, for the purposes of 

this subpart, with respect to FHWA or FTA, 

means the point at which there is a specific 

action to make a determination that a project 

is categorically excluded, to make a Finding 

of No Significant Impact, or to issue a record 

of decision on a Final Environmental Impact 

Statement under NEPA. 

Nonattainment area means any geographic 

region of the United States which has been 

designated as nonattainment under section 107 

of the CAA for any pollutant for which a 

national ambient air quality standard exists. 

Project means a highway project or transit 

project. 

Protective finding means a determination by 

EPA that a submitted control strategy 

implementation plan revision contains adopted 

control measures or written commitments to 

adopt enforceable control measures that fully 

satisfy the emissions reductions requirements 

relevant to the statutory provision for which 

the implementation plan revision was 

submitted, such as reasonable further progress 

or attainment. 

Recipient of funds designated under title 23 

U.S.C. or the Federal Transit Laws means any 

agency at any level of State, county, city, or 

regional government that routinely receives 

title 23 U.S.C. or Federal Transit Laws funds 

to construct FHWA/FTA projects, operate 

FHWA/FTA projects or equipment, purchase 

equipment, or undertake other services or 

operations via contracts or agreements. This 

definition does not include private landowners 

or developers, or contractors or entities that 

are only paid for services or products created 

by their own employees. 

Regionally significant project 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. 

Safety margin means the amount by which the 

total projected emissions from all sources of a 

given pollutant are less than the total 

emissions that would satisfy the applicable 

requirement for reasonable further progress, 

attainment, or maintenance. 

Standard means a national ambient air quality 

standard. 

Transit is mass transportation by bus, rail, or 

other conveyance which provides general or 

special service to the public on a regular and 

continuing basis. It does not include school 

buses or charter or sightseeing services. 

Transit project is an undertaking to implement 

or modify a transit facility or transit-related 

program; purchase transit vehicles or 

equipment; or provide financial assistance for 

transit operations. It does not include actions 

that are solely within the jurisdiction of local 

transit agencies, such as changes in routes, 

schedules, or fares. It may consist of several 

phases. For analytical purposes, it must be 

defined inclusively enough to: 

(1) Connect logical termini and be of 

sufficient length to address environmental 

matters on a broad scope; 

6 
 

§93.101● §93.102(b) 

(2) Have independent utility or independent 

significance, i.e., be a reasonable expenditure 

even if no additional transportation 

improvements in the area are made; and 

(3) Not restrict consideration of alternatives 

for other reasonably foreseeable transportation 

improvements. 

Transportation control measure (TCM) is any 

measure that is specifically identified and 

committed to in the applicable implementation 

plan, including a substitute or additional TCM 

that is incorporated into the applicable SIP 

through the process established in CAA 

section 176(c)(8), that is either one of the 

types listed in CAA section 108, or any other 

measure for the purpose of reducing emissions 

or concentrations of air pollutants from 

transportation sources by reducing vehicle use 

or changing traffic flow or congestion 

conditions. Notwithstanding the first sentence 

of this definition, vehicle technology-based, 

fuel-based, and maintenance-based measures 

which control the emissions from vehicles 

under fixed traffic conditions are not TCMs 

for the purposes of this subpart. 

Transportation improvement program (TIP) 

means a transportation improvement program 

developed by a metropolitan planning 

organization under 23 U.S.C. 134(j). 

Transportation plan means the official 

intermodal metropolitan transportation plan 

that is developed through the metropolitan 

planning process for the metropolitan planning 

area, developed pursuant to 23 CFR part 450. 

Transportation project is a highway project or 

a transit project. 

Written commitment for the purposes of this 

subpart means a written commitment that 

includes a description of the action to be 

taken; a schedule for the completion of the 

action; a demonstration that funding necessary 

to implement the action has been authorized 

by the appropriating or authorizing body; and 

an acknowledgment that the commitment is an 

enforceable obligation under the applicable 

implementation plan. 

§ 93.102 Applicability. 

(a) Action applicability. 

(1) Except as provided for in paragraph (c) 

of this section or §93.126, conformity 

determinations are required for: 

(i) The adoption, acceptance, approval or 

support of transportation plans and 

transportation plan amendments developed 

pursuant to 23 CFR part 450 or 49 CFR part 

613 by an MPO or DOT; 

(ii) The adoption, acceptance, approval or 

support of TIPs and TIP amendments 

developed pursuant to 23 CFR part 450 or 49 

CFR part 613 by an MPO or DOT; and 

(iii) The approval, funding, or 

implementation of FHWA/FTA projects. 

(2) Conformity determinations are not 

required under this subpart for individual 

projects which are not FHWA/FTA projects. 

However, §93.121 applies to such projects if 

they are regionally significant. 

(b) Geographic applicability. The 

provisions of this subpart shall apply in all 

nonattainment and maintenance areas for 

transportation-related criteria pollutants for 

which the area is designated nonattainment or 

has a maintenance plan. 

(1) The provisions of this subpart apply 

with respect to emissions of the following 

criteria pollutants: ozone, carbon monoxide 

(CO), nitrogen dioxide (NO2), particles with 

an aerodynamic diameter less than or equal to 

a nominal 10 micrometers (PM10); and 

particles with an aerodynamic diameter less 

than or equal to a nominal 2.5 micrometers 

(PM2.5). 

(2) The provisions of this subpart also 

apply with respect to emissions of the 

following precursor pollutants: 

7 
 

§93.102(b) – (d) 

(i) Volatile organic compounds (VOC) and 

nitrogen oxides (NOX) in ozone areas; 

(ii) NOX in NO2 areas; 

(iii) VOC and/or NOX in PM10 areas if the 

EPA Regional Administrator or the director of 

the State air agency has made a finding that 

transportation-related emissions of one or both 

of these precursors within the nonattainment 

area are a significant contributor to the PM10 

nonattainment problem and has so notified the 

MPO and DOT, or if the applicable 

implementation plan (or implementation plan 

submission) establishes an approved (or 

adequate) budget for such emissions as part of 

the reasonable further progress, attainment or 

maintenance strategy; 

(iv) NOX in PM2.5 areas, unless both the 

EPA Regional Administrator and the director 

of the state air agency have made a finding 

that transportation-related emissions of NOX 

within the nonattainment area are not a 

significant contributor to the PM2.5 

nonattainment problem and has so notified the 

MPO and DOT, or the applicable 

implementation plan (or implementation plan 

submission) does not establish an approved 

(or adequate) budget for such emissions as 

part of the reasonable further progress, 

attainment or maintenance strategy; and 

(v) VOC, sulfur dioxide (SO2) and/or 

ammonia (NH3) in PM2.5 areas either if the 

EPA Regional Administrator or the director of 

the state air agency has made a finding that 

transportation-related emissions of any of 

these precursors within the nonattainment area 

are a significant contributor to the PM2.5 

nonattainment problem and has so notified the 

MPO and DOT, or if the applicable 

implementation plan (or implementation plan 

submission) establishes an approved (or 

adequate) budget for such emissions as part of 

the reasonable further progress, attainment or 

maintenance strategy. 

(3) The provisions of this subpart apply to 

PM2.5 nonattainment and maintenance areas 

with respect to PM2.5 from re-entrained road 

dust if the EPA Regional Administrator or the 

director of the State air agency has made a 

finding that re-entrained road dust emissions 

within the area are a significant contributor to 

the PM2.5 nonattainment problem and has so 

notified the MPO and DOT, or if the 

applicable implementation plan (or 

implementation plan submission) includes reentrained road dust in the approved (or 

adequate) budget as part of the reasonable 

further progress, attainment or maintenance 

strategy. Re-entrained road dust emissions are 

produced by travel on paved and unpaved 

roads (including emissions from anti-skid and 

deicing materials). 

(4) The provisions of this subpart apply to 

maintenance areas through the last year of a 

maintenance area’s approved CAA section 

175A(b) maintenance plan, unless the 

applicable implementation plan specifies that 

the provisions of this subpart shall apply for 

more than 20 years. 

(c) Limitations. In order to receive any 

FHWA/FTA approval or funding actions, 

including NEPA approvals, for a project phase 

subject to this subpart, a currently conforming 

transportation plan and TIP must be in place at 

the time of project approval as described in 

§93.114, except as provided by §93.114(b). 

(d) Grace period for new nonattainment 

areas. For areas or portions of areas which 

have been continuously designated attainment 

or not designated for any NAAQS for ozone, 

CO, PM10, PM2.5 or NO2 since 1990 and are 

subsequently redesignated to nonattainment or 

designated nonattainment for any NAAQS for 

any of these pollutants, the provisions of this 

subpart shall not apply with respect to that 

NAAQS for 12 months following the effective 

date of final designation to nonattainment for 

each NAAQS for such pollutant. 

8 
 

§93.103 ● §93.104(d) 

§ 93.103 Priority. 

When assisting or approving any action with 

air quality-related consequences, FHWA and 

FTA shall give priority to the implementation 

of those transportation portions of an 

applicable implementation plan prepared to 

attain and maintain the NAAQS. This priority 

shall be consistent with statutory requirements 

for allocation of funds among States or other 

jurisdictions. 

§ 93.104 Frequency of conformity 

determinations. 

(a) Conformity determinations and 

conformity redeterminations for transportation 

plans, TIPs, and FHWA/FTA projects must be 

made according to the requirements of this 

section and the applicable implementation 

plan. 

(b) Frequency of conformity 

determinations for transportation plans. 

(1) Each new transportation plan must be 

demonstrated to conform before the 

transportation plan is approved by the MPO or 

accepted by DOT. 

(2) All transportation plan amendments 

must be found to conform before the 

transportation plan amendments are approved 

by the MPO or accepted by DOT, unless the 

amendment merely adds or deletes exempt 

projects listed in §93.126 or §93.127. The 

conformity determination must be based on 

the transportation plan and the amendment 

taken as a whole. 

(3) The MPO and DOT must determine the 

conformity of the transportation plan 

(including a new regional emissions analysis) 

no less frequently than every four years. If 

more than four years elapse after DOT's 

conformity determination without the MPO 

and DOT determining conformity of the 

transportation plan, a 12-month grace period 

will be implemented as described in paragraph 

(f) of this section. At the end of this 12-month 

grace period, the existing conformity 

determination will lapse.

 (c) Frequency of conformity determinations 

for transportation improvement programs. 

(1) A new TIP must be demonstrated to 

conform before the TIP is approved by the 

MPO or accepted by DOT. 

(2) A TIP amendment requires a new 

conformity determination for the entire TIP 

before the amendment is approved by the 

MPO or accepted by DOT, unless the 

amendment merely adds or deletes exempt 

projects listed in §93.126 or §93.127. 

(3) The MPO and DOT must determine the 

conformity of the TIP (including a new 

regional emissions analysis) no less frequently 

than every four years. If more than four years 

elapse after DOT's conformity determination 

without the MPO and DOT determining 

conformity of the TIP, a 12-month grace 

period will be implemented as described in 

paragraph (f) of this section. At the end of 

this 12-month grace period, the existing 

conformity determination will lapse.

 (d) Projects. FHWA/FTA projects must be 

found to conform before they are adopted, 

accepted, approved, or funded. Conformity 

must be redetermined for any FHWA/FTA 

project if one of the following occurs: a 

significant change in the project's design 

concept and scope; three years elapse since the 

most recent major step to advance the project; 

or initiation of a supplemental environmental 

document for air quality purposes. Major steps 

include NEPA process completion; start of 

final design; acquisition of a significant 

portion of the right-of-way; and, construction 

(including Federal approval of plans, 

specifications and estimates). 

9 
§93.104(e) ● §93.105(b) 

(e) Triggers for transportation plan and 

TIP conformity determinations. Conformity of 

existing transportation plans and TIPs must be 

redetermined within two years of the 

following, or after a 12-month grace period 

(as described in paragraph (f) of this section) 

the existing conformity determination will 

lapse, and no new project-level conformity 

determinations may be made until conformity 

of the transportation plan and TIP has been 

determined by the MPO and DOT: (1) The 

effective date of EPA's finding that motor 

vehicle emissions budgets from an initially 

submitted control strategy implementation 

plan or maintenance plan are adequate 

pursuant to §93.118(e) and can be used for 

transportation conformity purposes; 

(2) The effective date of EPA approval of a 

control strategy implementation plan revision 

or maintenance plan which establishes or 

revises a motor vehicle emissions budget if 

that budget has not yet been used in a 

conformity determination prior to approval; 

and 

(3) The effective date of EPA promulgation 

of an implementation plan which establishes 

or revises a motor vehicle emissions budget. 

(f) Lapse grace period. During the 12-

month grace period referenced in paragraphs 

(b)(3), (c)(3), and (e) of this section, a project 

may be found to conform according to the 

requirements of this part if: 

(1) the project is included in the currently 

conforming transportation plan and TIP (or 

regional emissions analysis); or 

(2) the project is included in the most 

recent conforming transportation plan and TIP 

(or regional emissions analysis). 

§ 93.105 Consultation. 

(a) General. The implementation plan 

revision required under §51.390 of this 

chapter shall include procedures for 

interagency consultation (Federal, State, and 

local), resolution of conflicts, and public 

consultation as described in paragraphs (a) 

through (e) of this section. Public consultation 

procedures will be developed in accordance 

with the requirements for public involvement 

in 23 CFR part 450. 

(1) The implementation plan revision shall 

include procedures to be undertaken by 

MPOs, State departments of transportation, 

and DOT with State and local air quality 

agencies and EPA before making conformity 

determinations, and by State and local air 

agencies and EPA with MPOs, State 

departments of transportation, and DOT in 

developing applicable implementation plans. 

(2) Before EPA approves the conformity 

implementation plan revision required by 

§51.390 of this chapter, MPOs and State 

departments of transportation must provide 

reasonable opportunity for consultation with 

State air agencies, local air quality and 

transportation agencies, DOT, and EPA, 

including consultation on the issues described 

in paragraph (c)(1) of this section, before 

making conformity determinations. 

(b) Interagency consultation procedures: 

General factors. 

(1) States shall provide well-defined 

consultation procedures in the implementation 

plan whereby representatives of the MPOs, 

State and local air quality planning agencies, 

State and local transportation agencies, and 

other organizations with responsibilities for 

developing, submitting, or implementing 

provisions of an implementation plan required 

by the CAA must consult with each other and 

with local or regional offices of EPA, FHWA, 

and FTA on the development of the 

implementation plan, the transportation plan, 

the TIP, and associated conformity 

determinations. 

(2) Interagency consultation procedures 

shall include at a minimum the following 

general factors and the specific processes in 

paragraph (c) of this section: 

10 
§93.105(b) – (c) 

(i) The roles and responsibilities assigned 

to each agency at each stage in the 

implementation plan development process and 

the transportation planning process, including 

technical meetings; 

(ii) The organizational level of regular 

consultation; 

(iii) A process for circulating (or providing 

ready access to) draft documents and 

supporting materials for comment before 

formal adoption or publication; 

(iv) The frequency of, or process for 

convening, consultation meetings and 

responsibilities for establishing meeting 

agendas; 

(v) A process for responding to the 

significant comments of involved agencies; 

and 

(vi) A process for the development of a list 

of the TCMs which are in the applicable 

implementation plan. 

(c) Interagency consultation procedures: 

Specific processes. Interagency consultation 

procedures shall also include the following 

specific processes: 

(1) A process involving the MPO, State 

and local air quality planning agencies, State 

and local transportation agencies, EPA, and 

DOT for the following: 

(i) Evaluating and choosing a model (or 

models) and associated methods and 

assumptions to be used in hot-spot analyses 

and regional emissions analyses; 

(ii) Determining which minor arterials and 

other transportation projects should be 

considered “regionally significant” for the 

purposes of regional emissions analysis (in 

addition to those functionally classified as 

principal arterial or higher or fixed guideway 

systems or extensions that offer an alternative 

to regional highway travel), and which 

projects should be considered to have a 

significant change in design concept and 

scope from the transportation plan or TIP; 

(iii) Evaluating whether projects otherwise 

exempted from meeting the requirements of 

this subpart (see §§93.126 and 93.127) should 

be treated as non-exempt in cases where 

potential adverse emissions impacts may exist 

for any reason; 

(iv) Making a determination, as required by 

§93.113(c)(1), whether past obstacles to 

implementation of TCMs which are behind 

the schedule established in the applicable 

implementation plan have been identified and 

are being overcome, and whether State and 

local agencies with influence over approvals 

or funding for TCMs are giving maximum 

priority to approval or funding for TCMs. This 

process shall also consider whether delays in 

TCM implementation necessitate revisions to 

the applicable implementation plan to remove 

TCMs or substitute TCMs or other emission 

reduction measures; 

(v) Notification of transportation plan or 

TIP amendments which merely add or delete 

exempt projects listed in §93.126 or §93.127; 

and 

(vi) Choosing conformity tests and 

methodologies for isolated rural 

nonattainment and maintenance areas, as 

required by §93.109(n)(2)(iii). 

(2) A process involving the MPO and State 

and local air quality planning agencies and 

transportation agencies for the following: 

(i) Evaluating events which will trigger 

new conformity determinations in addition to 

those triggering events established in §93.104; 

and 

(ii) Consulting on emissions analysis for 

transportation activities which cross the 

borders of MPOs or nonattainment areas or air 

basins. 

(3) Where the metropolitan planning area 

does not include the entire nonattainment or 

maintenance area, a process involving the 

MPO and the State department of 

transportation for cooperative planning and 

analysis for purposes of determining 

conformity of all projects outside the 

11 
§93.105(c) – (e) 

metropolitan area and within the 

nonattainment or maintenance area. 

(4) A process to ensure that plans for 

construction of regionally significant projects 

which are not FHWA/FTA projects (including 

projects for which alternative locations, design 

concept and scope, or the no-build option are 

still being considered), including those by 

recipients of funds designated under title 23 

U.S.C. or the Federal Transit Laws, are 

disclosed to the MPO on a regular basis, and 

to ensure that any changes to those plans are 

immediately disclosed. 

(5) A process involving the MPO and other 

recipients of funds designated under title 23 

U.S.C. or the Federal Transit Laws for 

assuming the location and design concept and 

scope of projects which are disclosed to the 

MPO as required by paragraph (c)(4) of this 

section but whose sponsors have not yet 

decided these features, in sufficient detail to 

perform the regional emissions analysis 

according to the requirements of §93.122. 

(6) A process for consulting on the design, 

schedule, and funding of research and data 

collection efforts and regional transportation 

model development by the MPO (e.g., 

household/ travel transportation surveys). 

(7) A process for providing final 

documents (including applicable 

implementation plans and implementation 

plan revisions) and supporting information to 

each agency after approval or adoption. This 

process is applicable to all agencies described 

in paragraph (a)(1) of this section, including 

Federal agencies. 

(d) Resolving conflicts. Conflicts among State 

agencies or between State agencies and an 

MPO shall be escalated to the Governor if 

they cannot be resolved by the heads of the 

involved agencies. The State air agency has 14 

calendar days to appeal to the Governor after 

the State DOT or MPO has notified the State 

air agency head of the resolution of his or her 

comments. The implementation plan revision 

required by §51.390 of this chapter shall 

define the procedures for starting the 14-day 

clock. If the State air agency appeals to the 

Governor, the final conformity determination 

must have the concurrence of the Governor. If 

the State air agency does not appeal to the 

Governor within 14 days, the MPO or State 

department of transportation may proceed 

with the final conformity determination. The 

Governor may delegate his or her role in this 

process, but not to the head or staff of the 

State or local air agency, State department of 

transportation, State transportation 

commission or board, or an MPO. 

(e) Public consultation procedures. 

Affected agencies making conformity 

determinations on transportation plans, 

programs, and projects shall establish a 

proactive public involvement process which 

provides opportunity for public review and 

comment by, at a minimum, providing 

reasonable public access to technical and 

policy information considered by the agency 

at the beginning of the public comment period 

and prior to taking formal action on a 

conformity determination for all transportation 

plans and TIPs, consistent with these 

requirements and those of 23 CFR 450.316(a). 

Any charges imposed for public inspection 

and copying should be consistent with the fee 

schedule contained in 49 CFR 7.43. In 

addition, these agencies must specifically 

address in writing all public comments that 

known plans for a regionally significant 

project which is not receiving FHWA or FTA 

funding or approval have not been properly 

reflected in the emissions analysis supporting 

a proposed conformity finding for a 

transportation plan or TIP. These agencies 

shall also provide opportunity for public 

involvement in conformity determinations for 

projects where otherwise required by law. 

12 
§93.106(a) – (b) 

§ 93.106 Content of transportation plans 

and timeframe of conformity 

determinations. 

(a) Transportation plans adopted after 

January 1, 1997 in serious, severe, or extreme 

ozone nonattainment areas and in serious CO 

nonattainment areas. If the metropolitan 

planning area contains an urbanized area 

population greater than 200,000, the 

transportation plan must specifically describe 

the transportation system envisioned for 

certain future years which shall be called 

horizon years. 

(1) The agency or organization developing 

the transportation plan may choose any years 

to be horizon years, subject to the following 

restrictions: 

(i) Horizon years may be no more than 10 

years apart; 

(ii) The first horizon year may be no more 

than 10 years from the base year used to 

validate the transportation demand planning 

model; 

(iii) The attainment year must be a horizon 

year if it is in the timeframe of the 

transportation plan and conformity 

determination; 

(iv) The last year of the transportation 

plan's forecast period must be a horizon year; 

and 

(v) If the timeframe of the conformity 

determination has been shortened under 

paragraph (d) of this section, the last year of 

the timeframe of the conformity determination 

must be a horizon year. 

(2) For these horizon years: 

(i) The transportation plan shall quantify 

and document the demographic and 

employment factors influencing expected 

transportation demand, including land use 

forecasts, in accordance with implementation 

plan provisions and the consultation 

requirements specified by §93.105; 

(ii) The highway and transit system shall be 

described in terms of the regionally significant 

additions or modifications to the existing 

transportation network which the 

transportation plan envisions to be operational 

in the horizon years. Additions and 

modifications to the highway network shall be 

sufficiently identified to indicate intersections 

with existing regionally significant facilities, 

and to determine their effect on route options 

between transportation analysis zones. Each 

added or modified highway segment shall also 

be sufficiently identified in terms of its design 

concept and design scope to allow modeling 

of travel times under various traffic volumes, 

consistent with the modeling methods for 

area-wide transportation analysis in use by the 

MPO. Transit facilities, equipment, and 

services envisioned for the future shall be 

identified in terms of design concept, design 

scope, and operating policies that are 

sufficient for modeling of their transit 

ridership. Additions and modifications to the 

transportation network shall be described 

sufficiently to show that there is a reasonable 

relationship between expected land use and 

the envisioned transportation system; and 

(iii) Other future transportation policies, 

requirements, services, and activities, 

including intermodal activities, shall be 

described. 

(b) Two-year grace period for transportation 

plan requirements in certain ozone and CO 

areas. The requirements of paragraph (a) of 

this section apply to such areas or portions of 

such areas that have previously not been 

required to meet these requirements for any 

existing NAAQS two years from the 

following: 

(1) The effective date of EPA's 

reclassification of an ozone or CO 

nonattainment area that has an urbanized area 

population greater than 200,000 to serious or 

above; 

(2) The official notice by the Census 

Bureau that determines the urbanized area 

population of a serious or above ozone or CO 

13 
 

§93.106(b) ● §93.107 

nonattainment area to be greater than 200,000; 

or, 

(3) The effective date of EPA's action that 

classifies a newly designated ozone or CO 

nonattainment area that has an urbanized area 

population greater than 200,000 as serious or 

above. 

(c) Transportation plans for other areas. 

Transportation plans for other areas must meet 

the requirements of paragraph (a) of this 

section at least to the extent it has been the 

previous practice of the MPO to prepare plans 

which meet those requirements. Otherwise, 

the transportation system envisioned for the 

future must be sufficiently described within 

the transportation plans so that a conformity 

determination can be made according to the 

criteria and procedures of §§93.109 through 

93.119. 

(d) Timeframe of conformity determination. 

(1) Unless an election is made under 

paragraph (d)(2) or (d)(3) of this section, the 

timeframe of the conformity determination 

must be through the last year of the 

transportation plan’s forecast period. 

(2) For areas that do not have an adequate 

or approved CAA section 175A(b) 

maintenance plan, the MPO may elect to 

shorten the timeframe of the transportation 

plan and TIP conformity determination, after 

consultation with state and local air quality 

agencies, solicitation of public comments, and 

consideration of such comments. 

(i) The shortened timeframe of the 

conformity determination must extend at least 

to the latest of the following years: 

(A) The tenth year of the transportation 

plan; 

(B) The latest year for which an adequate 

or approved motor vehicle emissions 

budget(s) is established in the submitted or 

applicable implementation plan; or 

(C) 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. 

(ii) 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 shown to exceed motor vehicle emissions 

budgets in a prior regional emissions analysis, 

if such a year extends beyond the timeframe 

of the conformity determination. 

(3) For areas that have an adequate or 

approved CAA section 175A(b) maintenance 

plan, the MPO may elect to shorten the 

timeframe of the conformity determination to 

extend through the last year of such 

maintenance plan after consultation with state 

and local air quality agencies, solicitation of 

public comments, and consideration of such 

comments. 

(4) Any election made by an MPO under 

paragraphs (d)(2) or (d)(3) of this section shall 

continue in effect until the MPO elects 

otherwise, after consultation with state and 

local air quality agencies, solicitation of public 

comments, and consideration of such 

comments. 

(e) Savings. The requirements of this 

section supplement other requirements of 

applicable law or regulation governing the 

format or content of transportation plans. 

§ 93.107 Relationship of transportation 

plan and TIP conformity with the NEPA 

process. 

The degree of specificity required in the 

transportation plan and the specific travel 

network assumed for air quality modeling do 

not preclude the consideration of alternatives 

in the NEPA process or other project 

development studies. Should the NEPA 

process result in a project with design concept 

and scope significantly different from that in 

the transportation plan or TIP, the project 

must meet the criteria in §§93.109 through 

14 
§93.107 ● §93.109(c) 

93.119 for projects not from a TIP before 

NEPA process completion. 

§ 93.108 Fiscal constraints for 

transportation plans and TIPs. 

Transportation plans and TIPs must be fiscally 

constrained consistent with DOT's 

metropolitan planning regulations at 23 CFR 

part 450 in order to be found in conformity. 

§ 93.109 Criteria and procedures for 

determining conformity of transportation 

plans, programs, and projects: General. 

(a) In order for each transportation plan, 

program, and FHWA/FTA project to be found 

to conform, the MPO and DOT must 

demonstrate that the applicable criteria and 

procedures in this subpart are satisfied, and 

the MPO and DOT must comply with all 

applicable conformity requirements of 

implementation plans and of court orders for 

the area which pertain specifically to 

conformity. The criteria for making 

conformity determinations differ based on the 

action under review (transportation plans, 

TIPs, and FHWA/FTA projects), the relevant 

pollutant(s), and the status of the 

implementation plan. 

(b) Table 1 in this paragraph indicates the 

criteria and procedures in §§93.110 through 

93.119 which apply for transportation plans, 

TIPs, and FHWA/FTA projects. Paragraphs 

(c) through (k) of this section explain when 

the budget, interim emissions, and hot-spot 

tests are required for each pollutant and 

NAAQS. Paragraph (l) of this section 

addresses conformity requirements for areas 

with approved or adequate limited 

maintenance plans. Paragraph (m) of this 

section addresses nonattainment and 

maintenance areas which EPA has determined 

have insignificant motor vehicle emissions. 

Paragraph (n) of this section addresses 

isolated rural nonattainment and maintenance 

areas. Table 1 follows: 

Table 1—Conformity Criteria 

All Actions at all times: 

§93.110 Latest planning assumptions 

§93.111 Latest emissions model 

§93.112 Consultation 

Transportation Plan: 

§93.113(b) TCMs 

§93.118 and/or Emissions budget and/or Interim 

§93.119 emissions 

TIP: 

§93.113(c) TCMs 

§93.118 and/or Emissions budget and/or Interim 

§93.119 emissions 

Project (From a Conforming Plan and TIP): 

§93.114 Currently conforming plan and TIP 

§93.115 Project from a conforming plan 

and TIP 

§93.116 CO, PM10, and PM2.5 hot-spots. 

§93.117 PM10 and PM2.5 control measures 

Project (Not From a Conforming Plan and TIP): 

§93.113(d) TCMs 

§93.114 Currently conforming plan and TIP 

§93.116 CO, PM10, and PM2.5 hot-spots. 

§93.117 PM10 and PM2.5 control measures 

§93.118 and/or Emissions budget and/or Interim 

§93.119 emissions 

(c) 1-hour ozone NAAQS nonattainment 

and maintenance areas. This paragraph 

applies when an area is nonattainment or 

maintenance for the 1-hour ozone NAAQS ( 

i.e., until the effective date of any revocation 

of the 1-hour ozone NAAQS for an area). In 

addition to the criteria listed in Table 1 in 

paragraph (b) of this section that are required 

to be satisfied at all times, in such ozone 

nonattainment and maintenance areas 

conformity determinations must include a 

demonstration that the budget and/or interim 

15 
§93.109(c) 

emissions tests are satisfied as described in the 

following: 

(1) In all 1-hour ozone nonattainment and 

maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan for the 1-

hour ozone NAAQS is adequate for 

transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(2) In ozone nonattainment areas that are 

required to submit a control strategy 

implementation plan revision for the 1-hour 

ozone NAAQS (usually moderate and above 

areas), the interim emissions tests must be 

satisfied as required by §93.119 for 

conformity determinations made when there is 

no approved motor vehicle emissions budget 

from an applicable implementation plan for 

the 1-hour ozone NAAQS and no adequate 

motor vehicle emissions budget from a 

submitted control strategy implementation 

plan revision or maintenance plan for the 1-

hour ozone NAAQS. 

(3) An ozone nonattainment area must 

satisfy the interim emissions test for NOX, as 

required by §93.119, if the implementation 

plan or plan submission that is applicable for 

the purposes of conformity determinations is a 

15% plan or Phase I attainment demonstration 

that does not include a motor vehicle 

emissions budget for NOX. The 

implementation plan for the 1-hour ozone 

NAAQS will be considered to establish a 

motor vehicle emissions budget for NOX if the 

implementation plan or plan submission 

contains an explicit NOX motor vehicle 

emissions budget that is intended to act as a 

ceiling on future NOX emissions, and the NOX 

motor vehicle emissions budget is a net 

reduction from NOX emissions levels in 1990. 

(4) Ozone nonattainment areas that have 

not submitted a maintenance plan and that are 

not required to submit a control strategy 

implementation plan revision for the 1-hour 

ozone NAAQS (usually marginal and below 

areas) must satisfy one of the following 

requirements: 

(i) The interim emissions tests required by 

§93.119; or 

(ii) The State shall submit to EPA an 

implementation plan revision for the 1-hour 

ozone NAAQS that contains motor vehicle 

emissions budget(s) and a reasonable further 

progress or attainment demonstration, and the 

budget test required by §93.118 must be 

satisfied using the adequate or approved motor 

vehicle emissions budget(s) (as described in 

paragraph (c)(1) of this section). 

(5) Notwithstanding paragraphs (c)(1) and 

(c)(2) of this section, moderate and above 

ozone nonattainment areas with three years of 

clean data for the 1-hour ozone NAAQS that 

have not submitted a maintenance plan and 

that EPA has determined are not subject to the 

Clean Air Act reasonable further progress and 

attainment demonstration requirements for the 

1-hour ozone NAAQS must satisfy one of the 

following requirements: 

(i) The interim emissions tests as required 

by §93.119; 

(ii) The budget test as required by §93.118, 

using the adequate or approved motor vehicle 

emissions budgets in the submitted or 

applicable control strategy implementation 

plan for the 1-hour ozone NAAQS (subject to 

the timing requirements of paragraph (c)(1) of 

this section); or 

(iii) The budget test as required by 

§93.118, using the motor vehicle emissions of 

ozone precursors in the most recent year of 

clean data as motor vehicle emissions budgets, 

if such budgets are established by the EPA 

16 
§93.109(c) – (d) 

rulemaking that determines that the area has 

clean data for the 1-hour ozone NAAQS. 

(d) 8-hour ozone NAAQS nonattainment 

and maintenance areas without motor vehicle 

emissions budgets for the 1-hour ozone 

NAAQS for any portion of the 8-hour 

nonattainment area . This paragraph applies to 

areas that were never designated 

nonattainment for the 1-hour ozone NAAQS 

and areas that were designated nonattainment 

for the 1-hour ozone NAAQS but that never 

submitted a control strategy SIP or 

maintenance plan with approved or adequate 

motor vehicle emissions budgets. This 

paragraph applies 1 year after the effective 

date of EPA's nonattainment designation for 

the 8-hour ozone NAAQS for an area, 

according to §93.102(d). In addition to the 

criteria listed in Table 1 in paragraph (b) of 

this section that are required to be satisfied at 

all times, in such 8-hour ozone nonattainment 

and maintenance areas conformity 

determinations must include a demonstration 

that the budget and/or interim emissions tests 

are satisfied as described in the following: 

(1) In such 8-hour ozone nonattainment 

and maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan for the 8-

hour ozone NAAQS is adequate for 

transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(2) In ozone nonattainment areas that are 

required to submit a control strategy 

implementation plan revision for the 8-hour 

ozone NAAQS (usually moderate and above 

and certain Clean Air Act, part D, subpart 1 

areas), the interim emissions tests must be 

satisfied as required by §93.119 for 

conformity determinations made when there is 

no approved motor vehicle emissions budget 

from an applicable implementation plan for 

the 8-hour ozone NAAQS and no adequate 

motor vehicle emissions budget from a 

submitted control strategy implementation 

plan revision or maintenance plan for the 8-

hour ozone NAAQS. 

(3) Such an 8-hour ozone nonattainment 

area must satisfy the interim emissions test for 

NOX, as required by §93.119, if the 

implementation plan or plan submission that is 

applicable for the purposes of conformity 

determinations is a 15% plan or other control 

strategy SIP that addresses reasonable further 

progress that does not include a motor vehicle 

emissions budget for NOX. The 

implementation plan for the 8-hour ozone 

NAAQS will be considered to establish a 

motor vehicle emissions budget for NOX if the 

implementation plan or plan submission 

contains an explicit NOX motor vehicle 

emissions budget that is intended to act as a 

ceiling on future NOX emissions, and the NOX 

motor vehicle emissions budget is a net 

reduction from NOX emissions levels in 2002. 

(4) Ozone nonattainment areas that have 

not submitted a maintenance plan and that are 

not required to submit a control strategy 

implementation plan revision for the 8-hour 

ozone NAAQS (usually marginal and certain 

Clean Air Act, part D, subpart 1 areas) must 

satisfy one of the following requirements: 

(i) The interim emissions tests required by 

§93.119; or 

(ii) The State shall submit to EPA an 

implementation plan revision for the 8-hour 

ozone NAAQS that contains motor vehicle 

emissions budget(s) and a reasonable further 

progress or attainment demonstration, and the 

budget test required by §93.118 must be 

satisfied using the adequate or approved motor 

17 
§93.109(d) – (e) 

vehicle emissions budget(s) (as described in 

paragraph (d)(1) of this section). 

(5) Notwithstanding paragraphs (d)(1) and 

(d)(2) of this section, ozone nonattainment 

areas with three years of clean data for the 8-

hour ozone NAAQS that have not submitted a 

maintenance plan and that EPA has 

determined are not subject to the Clean Air 

Act reasonable further progress and attainment 

demonstration requirements for the 8-hour 

ozone NAAQS must satisfy one of the 

following requirements: 

(i) The interim emissions tests as required 

by §93.119; 

(ii) The budget test as required by §93.118, 

using the adequate or approved motor vehicle 

emissions budgets in the submitted or 

applicable control strategy implementation 

plan for the 8-hour ozone NAAQS (subject to 

the timing requirements of paragraph (d)(1) of 

this section); or 

(iii) The budget test as required by 

§93.118, using the motor vehicle emissions of 

ozone precursors in the most recent year of 

clean data as motor vehicle emissions budgets, 

if such budgets are established by the EPA 

rulemaking that determines that the area has 

clean data for the 8-hour ozone NAAQS. 

(e) 8-hour ozone NAAQS nonattainment 

and maintenance areas with motor vehicle 

emissions budgets for the 1-hour ozone 

NAAQS that cover all or a portion of the 8-

hour nonattainment area . This provision 

applies 1 year after the effective date of EPA's 

nonattainment designation for the 8-hour 

ozone NAAQS for an area, according to 

§93.102(d). In addition to the criteria listed in 

Table 1 in paragraph (b) of this section that 

are required to be satisfied at all times, in such 

8-hour ozone nonattainment and maintenance 

areas conformity determinations must include 

a demonstration that the budget and/or interim 

emissions tests are satisfied as described in the 

following: 

(1) In such 8-hour ozone nonattainment 

and maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan for the 8-

hour ozone NAAQS is adequate for 

transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(2) Prior to paragraph (e)(1) of this section 

applying, the following test(s) must be 

satisfied: 

(i) If the 8-hour ozone nonattainment area 

covers the same geographic area as the 1-hour 

ozone nonattainment or maintenance area(s), 

the budget test as required by §93.118 using 

the approved or adequate motor vehicle 

emissions budgets in the 1-hour ozone 

applicable implementation plan or 

implementation plan submission; 

(ii) If the 8-hour ozone nonattainment area 

covers a smaller geographic area within the 1-

hour ozone nonattainment or maintenance 

area(s), the budget test as required by §93.118 

for either: 

(A) The 8-hour nonattainment area using 

corresponding portion(s) of the approved or 

adequate motor vehicle emissions budgets in 

the 1-hour ozone applicable implementation 

plan or implementation plan submission where 

such portion(s) can reasonably be identified 

through the interagency consultation process 

required by §93.105; or 

(B) The 1-hour nonattainment area using 

the approved or adequate motor vehicle 

emissions budgets in the 1-hour ozone 

applicable implementation plan or 

implementation plan submission. If additional 

emissions reductions are necessary to meet the 

18 
§93.109(e) 

budget test for the 8-hour ozone NAAQS in 

such cases, these emissions reductions must 

come from within the 8-hour nonattainment 

area; 

(iii) If the 8-hour ozone nonattainment area 

covers a larger geographic area and 

encompasses the entire 1-hour ozone 

nonattainment or maintenance area(s): 

(A) The budget test as required by §93.118 

for the portion of the 8-hour ozone 

nonattainment area covered by the approved 

or adequate motor vehicle emissions budgets 

in the 1-hour ozone applicable implementation 

plan or implementation plan submission; and 

(B) The interim emissions tests as required 

by §93.119 for either: the portion of the 8-

hour ozone nonattainment area not covered by 

the approved or adequate budgets in the 1-

hour ozone implementation plan, the entire 8-

hour ozone nonattainment area, or the entire 

portion of the 8-hour ozone nonattainment 

area within an individual state, in the case 

where separate 1-hour SIP budgets are 

established for each state of a multi-state 1-

hour nonattainment or maintenance area; 

(iv) If the 8-hour ozone nonattainment area 

partially covers a 1-hour ozone nonattainment 

or maintenance area(s): 

(A) The budget test as required by §93.118 

for the portion of the 8-hour ozone 

nonattainment area covered by the 

corresponding portion of the approved or 

adequate motor vehicle emissions budgets in 

the 1-hour ozone applicable implementation 

plan or implementation plan submission where 

they can be reasonably identified through the 

interagency consultation process required by 

§93.105; and 

(B) The interim emissions tests as required 

by §93.119, when applicable, for either: the 

portion of the 8-hour ozone nonattainment 

area not covered by the approved or adequate 

budgets in the 1-hour ozone implementation 

plan, the entire 8-hour ozone nonattainment 

area, or the entire portion of the 8-hour ozone 

nonattainment area within an individual state, 

in the case where separate 1-hour SIP budgets 

are established for each state in a multi-state 

1-hour nonattainment or maintenance area. 

(3) Such an 8-hour ozone nonattainment 

area must satisfy the interim emissions test for 

NOX, as required by §93.119, if the only 

implementation plan or plan submission that is 

applicable for the purposes of conformity 

determinations is a 15% plan or other control 

strategy SIP that addresses reasonable further 

progress that does not include a motor vehicle 

emissions budget for NOX. The 

implementation plan for the 8-hour ozone 

NAAQS will be considered to establish a 

motor vehicle emissions budget for NOX if the 

implementation plan or plan submission 

contains an explicit NOX motor vehicle 

emissions budget that is intended to act as a 

ceiling on future NOX emissions, and the NOX 

motor vehicle emissions budget is a net 

reduction from NOX emissions levels in 2002. 

Prior to an adequate or approved NOX motor 

vehicle emissions budget in the 

implementation plan submission for the 8-

hour ozone NAAQS, the implementation plan 

for the 1-hour ozone NAAQS will be 

considered to establish a motor vehicle 

emissions budget for NOX if the 

implementation plan contains an explicit NOX 

motor vehicle emissions budget that is 

intended to act as a ceiling on future NOX 

emissions, and the NOX motor vehicle 

emissions budget is a net reduction from NOX 

emissions levels in 1990. 

(4) Notwithstanding paragraphs (e)(1) and 

(e)(2) of this section, ozone nonattainment 

areas with three years of clean data for the 8-

hour ozone NAAQS that have not submitted a 

maintenance plan and that EPA has 

determined are not subject to the Clean Air 

Act reasonable further progress and attainment 

demonstration requirements for the 8-hour 

ozone NAAQS must satisfy one of the 

following requirements: 

(i) The budget test and/or interim emissions 

tests as required by §§93.118 and 93.119 and 

19 
§93.109(e) – (g) 

as described in paragraph (e)(2) of this 

section; 

(ii) The budget test as required by §93.118, 

using the adequate or approved motor vehicle 

emissions budgets in the submitted or 

applicable control strategy implementation 

plan for the 8-hour ozone NAAQS (subject to 

the timing requirements of paragraph (e)(1) of 

this section); or 

(iii) The budget test as required by 

§93.118, using the motor vehicle emissions of 

ozone precursors in the most recent year of 

clean data as motor vehicle emissions budgets, 

if such budgets are established by the EPA 

rulemaking that determines that the area has 

clean data for the 8-hour ozone NAAQS. 

(f) CO nonattainment and maintenance 

areas . In addition to the criteria listed in 

Table 1 in paragraph (b) of this section that 

are required to be satisfied at all times, in CO 

nonattainment and maintenance areas 

conformity determinations must include a 

demonstration that the hot-spot, budget and/or 

interim emissions tests are satisfied as 

described in the following: 

(1) FHWA/FTA projects in CO 

nonattainment or maintenance areas must 

satisfy the hot spot test required by §93.116(a) 

at all times. Until a CO attainment 

demonstration or maintenance plan is 

approved by EPA, FHWA/FTA projects must 

also satisfy the hot spot test required by 

§93.116(b). 

(2) In CO nonattainment and maintenance 

areas the budget test must be satisfied as 

required by §93.118 for conformity 

determinations made on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan is adequate 

for transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(3) Except as provided in paragraph (f)(4) 

of this section, in CO nonattainment areas the 

interim emissions tests must be satisfied as 

required by §93.119 for conformity 

determinations made when there is no 

approved motor vehicle emissions budget 

from an applicable implementation plan and 

no adequate motor vehicle emissions budget 

from a submitted control strategy 

implementation plan revision or maintenance 

plan. 

(4) CO nonattainment areas that have not 

submitted a maintenance plan and that are not 

required to submit an attainment 

demonstration (e.g., moderate CO areas with a 

design value of 12.7 ppm or less or not 

classified CO areas) must satisfy one of the 

following requirements: 

(i) The interim emissions tests required by 

§93.119; or 

(ii) The State shall submit to EPA an 

implementation plan revision that contains 

motor vehicle emissions budget(s) and an 

attainment demonstration, and the budget test 

required by §93.118 must be satisfied using 

the adequate or approved motor vehicle 

emissions budget(s) (as described in paragraph 

(f)(2) of this section). 

(g) PM10 nonattainment and maintenance 

areas. In addition to the criteria listed in Table 

1 in paragraph (b) of this section that are 

required to be satisfied at all times, in PM10 

nonattainment and maintenance areas 

conformity determinations must include a 

demonstration that the hot-spot, budget and/or 

interim emissions tests are satisfied as 

described in the following: 

(1) FHWA/FTA projects in PM10 

nonattainment or maintenance areas must 

satisfy the hot spot test required by 

§93.116(a). 

20 
§93.109(g) – (i) 

(2) In PM10 nonattainment and 

maintenance areas where a budget is 

submitted for the 24-hour PM10 NAAQS, the 

budget test must be satisfied as required by 

§93.118 for conformity determinations made 

on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan is adequate 

for transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(3) Prior to paragraph (g)(2) of this section 

applying, the budget test must be satisfied as 

required by §93.118 using the approved or 

adequate motor vehicle emissions budget 

established for the revoked annual PM10 

NAAQS, if such a budget exists. 

(4) In PM10 nonattainment areas the interim 

emissions tests must be satisfied as required 

by §93.119 for conformity determinations 

made: 

(i) If there is no approved motor vehicle 

emissions budget from an applicable 

implementation plan and no adequate motor 

vehicle emissions budget from a submitted 

control strategy implementation plan revision 

or maintenance plan; or 

(ii) If the submitted implementation plan 

revision is a demonstration of impracticability 

under CAA section 189(a)(1)(B)(ii) and does 

not demonstrate attainment. 

(h) NO2 nonattainment and maintenance 

areas. In addition to the criteria listed in Table 

1 in paragraph (b) of this section that are 

required to be satisfied at all times, in NO2 

nonattainment and maintenance areas 

conformity determinations must include a 

demonstration that the budget and/or interim 

emissions tests are satisfied as described in the 

following: 

(1) In NO2 nonattainment and maintenance 

areas the budget test must be satisfied as 

required by §93.118 for conformity 

determinations made on or after: 

(i) The effective date of EPA's finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan is adequate 

for transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(2) In NO2 nonattainment areas the interim 

emissions tests must be satisfied as required 

by §93.119 for conformity determinations 

made when there is no approved motor vehicle 

emissions budget from an applicable 

implementation plan and no adequate motor 

vehicle emissions budget from a submitted 

control strategy implementation plan revision 

or maintenance plan. 

(i) 1997 PM2.5 nonattainment and 

maintenance areas. In addition to the criteria 

listed in Table 1 in paragraph (b) of this 

section that are required to be satisfied at all 

times, in such 1997 PM2.5 nonattainment and 

maintenance areas conformity determinations 

must include a demonstration that the budget 

and/or interim emissions tests are satisfied as 

described in the following: 

(1) FHWA/FTA projects in such 1997 

PM2.5 nonattainment or maintenance areas 

must satisfy the appropriate hot-spot test 

required by §93.116(a). 

(2) In such 1997 PM2.5 nonattainment and 

maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA's finding that 

21 
 

§93.109(i) – (k) 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan is adequate 

for transportation conformity purposes; 

(ii) The publication date of EPA's approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA's approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(3) In such 1997 PM2.5 nonattainment areas 

the interim emissions tests must be satisfied as 

required by §93.119 for conformity 

determinations made if there is no approved 

motor vehicle emissions budget from an 

applicable implementation plan and no 

adequate motor vehicle emissions budget from 

a submitted control strategy implementation 

plan revision or maintenance plan. 

(j) 2006 PM2.5 NAAQS nonattainment and 

maintenance areas without 1997 PM2.5 

NAAQS motor vehicle emissions budgets for 

any portion of the 2006 PM2.5 NAAQS area. 

In addition to the criteria listed in Table 1 in 

paragraph (b) of this section that are required 

to be satisfied at all times, in such 2006 PM2.5 

nonattainment and maintenance areas 

conformity determinations must include a 

demonstration that the budget and/or interim 

emissions tests are satisfied as described in the 

following: 

(1) FHWA/FTA projects in such PM2.5 

nonattainment and maintenance areas must 

satisfy the appropriate hot-spot test required 

by §93.116(a). 

(2) In such PM2.5 nonattainment and 

maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA’s finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan for the 2006 

PM2.5 NAAQS is adequate for transportation 

conformity purposes; 

(ii) The publication date of EPA’s approval 

of such a budget in the Federal Register; or 

(iii) The effective date of EPA’s approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(3) In such PM2.5 nonattainment areas the 

interim emissions tests must be satisfied as 

required by §93.119 for conformity 

determinations made if there is no approved 

motor vehicle emissions budget from an 

applicable implementation plan for the 2006 

PM2.5 NAAQS and no adequate motor vehicle 

emissions budget from a submitted control 

strategy implementation plan revision or 

maintenance plan for the 2006 PM2.5 NAAQS. 

(k) 2006 PM2.5 NAAQS nonattainment and 

maintenance areas with motor vehicle 

emissions budgets for the 1997 PM2.5 NAAQS 

that cover all or a portion of the 2006 PM2.5 

nonattainment area. In addition to the criteria 

listed in Table 1 in paragraph (b) of this 

section that are required to be satisfied at all 

times, in such 2006 PM2.5 nonattainment and 

maintenance areas conformity determinations 

must include a demonstration that the budget 

and/or interim emissions tests are satisfied as 

described in the following: 

(1) FHWA/FTA projects in such PM2.5 

nonattainment and maintenance areas must 

satisfy the appropriate hot-spot test required 

by §93.116(a). 

(2) In such PM2.5 nonattainment and 

maintenance areas the budget test must be 

satisfied as required by §93.118 for 

conformity determinations made on or after: 

(i) The effective date of EPA’s finding that 

a motor vehicle emissions budget in a 

submitted control strategy implementation 

plan revision or maintenance plan for the 2006 

PM2.5 NAAQS is adequate for transportation 

conformity purposes; 

(ii) The publication date of EPA’s approval 

of such a budget in the Federal Register; or 

22 
§93.109(k) 

(iii) The effective date of EPA’s approval 

of such a budget in the Federal Register, if 

such approval is completed through direct 

final rulemaking. 

(3) Prior to paragraph (k)(2) of this section 

applying, the following test(s) must be 

satisfied: 

(i) If the 2006 PM2.5 nonattainment area 

covers the same geographic area as the 1997 

PM2.5 nonattainment or maintenance area(s), 

the budget test as required by §93.118 using 

the approved or adequate motor vehicle 

emissions budgets in the 1997 PM2.5 

applicable implementation plan or 

implementation plan submission; 

(ii) If the 2006 PM2.5 nonattainment area 

covers a smaller geographic area within the 

1997 PM2.5 nonattainment or maintenance 

area(s), the budget test as required by §93.118 

for either: 

(A) The 2006 PM2.5 nonattainment area 

using corresponding portion(s) of the 

approved or adequate motor vehicle emissions 

budgets in the 1997 PM2.5 applicable 

implementation plan or implementation plan 

submission where such portion(s) can 

reasonably be identified through the 

interagency consultation process required by 

§93.105; or 

(B) The 1997 PM2.5 nonattainment area 

using the approved or adequate motor vehicle 

emissions budgets in the 1997 PM2.5 

applicable implementation plan or 

implementation plan submission. If additional 

emissions reductions are necessary to meet the 

budget test for the 2006 PM2.5 NAAQS in 

such cases, these emissions reductions must 

come from within the 2006 PM2.5 

nonattainment area; 

(iii) If the 2006 PM2.5 nonattainment area 

covers a larger geographic area and 

encompasses the entire 1997 PM2.5 

nonattainment or maintenance area(s): 

(A) The budget test as required by §93.118 

for the portion of the 2006 PM2.5 

nonattainment area covered by the approved 

or adequate motor vehicle emissions budgets 

in the 1997 PM2.5 applicable implementation 

plan or implementation plan submission; and 

the interim emissions tests as required by 

§93.119 for either: the portion of the 2006 

PM2.5 nonattainment area not covered by the 

approved or adequate budgets in the 1997 

PM2.5 implementation plan, the entire 2006 

PM2.5 nonattainment area, or the entire portion 

of the 2006 PM2.5 nonattainment area within 

an individual state, in the case where separate 

1997 PM2.5 SIP budgets are established for 

each state of a multi-state 1997 PM2.5 

nonattainment or maintenance area; or 

(B) The budget test as required by §93.118 

for the entire 2006 PM2.5 nonattainment area 

using the approved or adequate motor vehicle 

emissions budgets in the applicable 1997 

PM2.5 implementation plan or implementation 

plan submission. 

(iv) If the 2006 PM2.5 nonattainment area 

partially covers a 1997 PM2.5 nonattainment or 

maintenance area(s): 

(A) The budget test as required by §93.118 

for the portion of the 2006 PM2.5 

nonattainment area covered by the 

corresponding portion of the approved or 

adequate motor vehicle emissions budgets in 

the 1997 PM2.5 applicable implementation 

plan or implementation plan submission where 

they can be reasonably identified through the 

interagency consultation process required by 

§93.105; and 

(B) The interim emissions tests as required 

by §93.119, when applicable, for either: the 

portion of the 2006 PM2.5 nonattainment area 

not covered by the approved or adequate 

budgets in the 1997 PM2.5 implementation 

plan, the entire 2006 PM2.5 nonattainment 

area, or the entire portion of the 2006 PM2.5 

nonattainment area within an individual state, 

in the case where separate 1997 PM2.5 SIP 

budgets are established for each state in a 

multi-state 1997 PM2.5 nonattainment or 

maintenance area. 

23 
§93.109(l) - (n) 

(l) Areas with limited maintenance plans. 

Notwithstanding the other paragraphs of this 

section, an area is not required to satisfy the 

regional emissions analysis for §93.118 and/or 

§93.119 for a given pollutant and NAAQS, if 

the area has an adequate or approved limited 

maintenance plan for such pollutant and 

NAAQS. A limited maintenance plan would 

have to demonstrate that it would be 

unreasonable to expect that such an area 

would experience enough motor vehicle 

emissions growth for a NAAQS violation to 

occur. A conformity determination that meets 

other applicable criteria in Table 1 of 

paragraph (b) of this section is still required, 

including the hot-spot requirements for 

projects in CO, PM10, and PM2.5 areas. 

 (m) Areas with insignificant motor vehicle 

emissions. Notwithstanding the other 

paragraphs in this section, an area is not 

required to satisfy a regional emissions 

analysis for §93.118 and/or §93.119 for a 

given pollutant/precursor and NAAQS, if EPA 

finds through the adequacy or approval 

process that a SIP demonstrates that regional 

motor vehicle emissions are an insignificant 

contributor to the air quality problem for that 

pollutant/precursor and NAAQS. The SIP 

would have to demonstrate that it would be 

unreasonable to expect that such an area 

would experience enough motor vehicle 

emissions growth in that pollutant/precursor 

for a NAAQS violation to occur. Such a 

finding would be based on a number of 

factors, including the percentage of motor 

vehicle emissions in the context of the total 

SIP inventory, the current state of air quality 

as determined by monitoring data for that 

NAAQS, the absence of SIP motor vehicle 

control measures, and historical trends and 

future projections of the growth of motor 

vehicle emissions. A conformity 

determination that meets other applicable 

criteria in Table 1 of paragraph (b) of this 

section is still required, including regional 

emissions analyses for §93.118 and/or 

§93.119 for other pollutants/precursors and 

NAAQS that apply. Hot-spot requirements for 

projects in CO, PM10, and PM2.5 areas in 

§93.116 must also be satisfied, unless EPA 

determines that the SIP also demonstrates that 

projects will not create new localized 

violations and/or increase the severity or 

number of existing violations of such 

NAAQS. If EPA subsequently finds that 

motor vehicle emissions of a given 

pollutant/precursor are significant, this 

paragraph would no longer apply for future 

conformity determinations for that 

pollutant/precursor and NAAQS. 

(n) Isolated rural nonattainment and 

maintenance areas. This paragraph applies to 

any nonattainment or maintenance area (or 

portion thereof) which does not have a 

metropolitan transportation plan or TIP and 

whose projects are not part of the emissions 

analysis of any MPO's metropolitan 

transportation plan or TIP. This paragraph 

does not apply to “donut” areas which are 

outside the metropolitan planning boundary 

and inside the nonattainment/maintenance 

area boundary. 

(1) FHWA/FTA projects in all isolated 

rural nonattainment and maintenance areas 

must satisfy the requirements of §§93.110, 

93.111, 93.112, 93.113(d), 93.116, and 

93.117. Until EPA approves the control 

strategy implementation plan or maintenance 

plan for a rural CO nonattainment or 

maintenance area, FHWA/FTA projects must 

also satisfy the requirements of §93.116(b) 

(“Localized CO, PM10, and PM2.5 violations 

(hot spots)”). 

(2) Isolated rural nonattainment and 

maintenance areas are subject to the budget 

and/or interim emissions tests as described in 

paragraphs (c) through (m) of this section, 

with the following modifications: 

(i) When the requirements of §§93.106(d), 

93.116, 93.118, and 93.119 apply to isolated 

24 
§93.109(n) ● §93.110(b) 

rural nonattainment and maintenance areas, 

references to “transportation plan” or “TIP” 

should be taken to mean those projects in the 

statewide transportation plan or statewide TIP 

which are in the rural nonattainment or 

maintenance area. When the requirements of 

§93.106(d) apply to isolated rural 

nonattainment and maintenance areas, 

references to “MPO” should be taken to mean 

the state department of transportation. 

(ii) In isolated rural nonattainment and 

maintenance areas that are subject to §93.118, 

FHWA/FTA projects must be consistent with 

motor vehicle emissions budget(s) for the 

years in the timeframe of the attainment 

demonstration or maintenance plan. For years 

after the attainment year (if a maintenance 

plan has not been submitted) or after the last 

year of the maintenance plan, FHWA/FTA 

projects must satisfy one of the following 

requirements: 

(A) §93.118; 

(B) §93.119 (including regional emissions 

analysis for NOX in all ozone nonattainment 

and maintenance areas, notwithstanding 

§93.119(f)(2)); or 

(C) As demonstrated by the air quality 

dispersion model or other air quality modeling 

technique used in the attainment 

demonstration or maintenance plan, the 

FHWA/FTA project, in combination with all 

other regionally significant projects expected 

in the area in the timeframe of the statewide 

transportation plan, must not cause or 

contribute to any new violation of any 

standard in any areas; increase the frequency 

or severity of any existing violation of any 

standard in any area; or delay timely 

attainment of any standard or any required 

interim emission reductions or other 

milestones in any area. Control measures 

assumed in the analysis must be enforceable. 

(iii) The choice of requirements in 

paragraph (n)(2)(ii) of this section and the 

methodology used to meet the requirements of 

paragraph (n)(2)(ii)(C) of this section must be 

determined through the interagency 

consultation process required in 

§93.105(c)(1)(vii) through which the relevant 

recipients of title 23 U.S.C. or Federal Transit 

Laws funds, the local air quality agency, the 

State air quality agency, and the State 

department of transportation should reach 

consensus about the option and methodology 

selected. EPA and DOT must be consulted 

through this process as well. In the event of 

unresolved disputes, conflicts may be 

escalated to the Governor consistent with the 

procedure in §93.105(d), which applies for 

any State air agency comments on a 

conformity determination. 

§ 93.110 Criteria and procedures: Latest 

planning assumptions. 

(a) Except as provided in this paragraph, 

the conformity determination, with respect to 

all other applicable criteria in §§93.111 

through 93.119, must be based upon the most 

recent planning assumptions in force at the 

time the conformity analysis begins. The 

conformity determination must satisfy the 

requirements of paragraphs (b) through (f) of 

this section using the planning assumptions 

available at the time the conformity analysis 

begins as determined through the interagency 

consultation process required in 

§93.105(c)(1)(i). The “time the conformity 

analysis begins” for a transportation plan or 

TIP determination is the point at which the 

MPO or other designated agency begins to 

model the impact of the proposed 

transportation plan or TIP on travel and/or 

emissions. New data that becomes available 

after an analysis begins is required to be used 

in the conformity determination only if a 

significant delay in the analysis has occurred, 

as determined through interagency 

consultation. 

(b) Assumptions must be derived from the 

estimates of current and future population, 

employment, travel, and congestion most 

25 
 § §93.110(b) ● §93.112 

recently developed by the MPO or other 

agency authorized to make such estimates and 

approved by the MPO. The conformity 

determination must also be based on the latest 

assumptions about current and future 

background concentrations. 

(c) The conformity determination for each 

transportation plan and TIP must discuss how 

transit operating policies (including fares and 

service levels) and assumed transit ridership 

have changed since the previous conformity 

determination. 

(d) The conformity determination must 

include reasonable assumptions about transit 

service and increases in transit fares and road 

and bridge tolls over time. 

(e) The conformity determination must use 

the latest existing information regarding the 

effectiveness of the TCMs and other 

implementation plan measures which have 

already been implemented. 

(f) Key assumptions shall be specified and 

included in the draft documents and 

supporting materials used for the interagency 

and public consultation required by §93.105. 

§ 93.111 Criteria and procedures: Latest 

emissions model. 

(a) The conformity determination must be 

based on the latest emission estimation model 

available. This criterion is satisfied if the most 

current version of the motor vehicle emissions 

model specified by EPA for use in the 

preparation or revision of implementation 

plans in that State or area is used for the 

conformity analysis. Where EMFAC is the 

motor vehicle emissions model used in 

preparing or revising the applicable 

implementation plan, new versions must be 

approved by EPA before they are used in the 

conformity analysis. 

(b) EPA will consult with DOT to establish 

a grace period following the specification of 

any new model. 

(1) The grace period will be no less than 

three months and no more than 24 months 

after notice of availability is published in the 

Federal Register. 

(2) The length of the grace period will 

depend on the degree of change in the model 

and the scope of re-planning likely to be 

necessary by MPOs in order to assure 

conformity. If the grace period will be longer 

than three months, EPA will announce the 

appropriate grace period in the Federal 

Register. 

(c) Transportation plan and TIP conformity 

analyses for which the emissions analysis was 

begun during the grace period or before the 

Federal Register notice of availability of the 

latest emission model may continue to use the 

previous version of the model. Conformity 

determinations for projects may also be based 

on the previous model if the analysis was 

begun during the grace period or before the 

Federal Register notice of availability, and if 

the final environmental document for the 

project is issued no more than three years after 

the issuance of the draft environmental 

document. 

§ 93.112 Criteria and procedures: 

Consultation. 

Conformity must be determined according to 

the consultation procedures in this subpart and 

in the applicable implementation plan, and 

according to the public involvement 

procedures established in compliance with 23 

CFR part 450. Until the implementation plan 

revision required by §51.390 of this chapter is 

fully approved by EPA, the conformity 

determination must be made according to 

§93.105 (a)(2) and (e) and the requirements of 

23 CFR part 450. 

26 
§93.113 ● §93.114(a) 

§ 93.113 Criteria and procedures: Timely 

implementation of TCMs. 

(a) The transportation plan, TIP, or any 

FHWA/FTA project which is not from a 

conforming plan and TIP must provide for the 

timely implementation of TCMs from the 

applicable implementation plan. 

(b) For transportation plans, this criterion is 

satisfied if the following two conditions are 

met: 

(1) The transportation plan, in describing 

the envisioned future transportation system, 

provides for the timely completion or 

implementation of all TCMs in the applicable 

implementation plan which are eligible for 

funding under title 23 U.S.C. or the Federal 

Transit Laws, consistent with schedules 

included in the applicable implementation 

plan. 

(2) Nothing in the transportation plan 

interferes with the implementation of any 

TCM in the applicable implementation plan. 

(c) For TIPs, this criterion is satisfied if the 

following conditions are met: 

(1) An examination of the specific steps 

and funding source(s) needed to fully 

implement each TCM indicates that TCMs 

which are eligible for funding under title 23 

U.S.C. or the Federal Transit Laws are on or 

ahead of the schedule established in the 

applicable implementation plan, or, if such 

TCMs are behind the schedule established in 

the applicable implementation plan, the MPO 

and DOT have determined that past obstacles 

to implementation of the TCMs have been 

identified and have been or are being 

overcome, and that all State and local agencies 

with influence over approvals or funding for 

TCMs are giving maximum priority to 

approval or funding of TCMs over other 

projects within their control, including 

projects in locations outside the nonattainment 

or maintenance area. 

(2) If TCMs in the applicable 

implementation plan have previously been 

programmed for Federal funding but the funds 

have not been obligated and the TCMs are 

behind the schedule in the implementation 

plan, then the TIP cannot be found to conform 

if the funds intended for those TCMs are 

reallocated to projects in the TIP other than 

TCMs, or if there are no other TCMs in the 

TIP, if the funds are reallocated to projects in 

the TIP other than projects which are eligible 

for Federal funding intended for air quality 

improvement projects, e.g., the Congestion 

Mitigation and Air Quality Improvement 

Program. 

(3) Nothing in the TIP may interfere with 

the implementation of any TCM in the 

applicable implementation plan. 

(d) For FHWA/FTA projects which are not 

from a conforming transportation plan and 

TIP, this criterion is satisfied if the project 

does not interfere with the implementation of 

any TCM in the applicable implementation 

plan. 

§ 93.114 Criteria and procedures: 

Currently conforming transportation plan 

and TIP. 

There must be a currently conforming 

transportation plan and currently conforming 

TIP at the time of project approval, or a 

project must meet the requirements in 

§93.104(f) during the 12-month lapse grace 

period. 

(a) Only one conforming transportation 

plan or TIP may exist in an area at any time; 

conformity determinations of a previous 

transportation plan or TIP expire once the 

current plan or TIP is found to conform by 

DOT. The conformity determination on a 

transportation plan or TIP will also lapse if 

conformity is not determined according to the 

frequency requirements specified in §93.104. 

27 
§93.114(b) ● §93.116(a) 

(b) This criterion is not required to be 

satisfied at the time of project approval for a 

TCM specifically included in the applicable 

implementation plan, provided that all other 

relevant criteria of this subpart are satisfied. 

§ 93.115 Criteria and procedures: Projects 

from a transportation plan and TIP. 

(a) The project must come from a 

conforming plan and program. If this criterion 

is not satisfied, the project must satisfy all 

criteria in Table 1 of §93.109(b) for a project 

not from a conforming transportation plan and 

TIP. A project is considered to be from a 

conforming transportation plan if it meets the 

requirements of paragraph (b) of this section 

and from a conforming program if it meets the 

requirements of paragraph (c) of this section. 

Special provisions for TCMs in an applicable 

implementation plan are provided in 

paragraph (d) of this section. 

(b) A project is considered to be from a 

conforming transportation plan if one of the 

following conditions applies: 

(1) For projects which are required to be 

identified in the transportation plan in order to 

satisfy §93.106 (“Content of transportation 

plans”), the project is specifically included in 

the conforming transportation plan and the 

project's design concept and scope have not 

changed significantly from those which were 

described in the transportation plan, or in a 

manner which would significantly impact use 

of the facility; or 

(2) For projects which are not required to 

be specifically identified in the transportation 

plan, the project is identified in the 

conforming transportation plan, or is 

consistent with the policies and purpose of the 

transportation plan and will not interfere with 

other projects specifically included in the 

transportation plan. 

(c) A project is considered to be from a 

conforming program if the following 

conditions are met: 

(1) The project is included in the 

conforming TIP and the design concept and 

scope of the project were adequate at the time 

of the TIP conformity determination to 

determine its contribution to the TIP's regional 

emissions, and the project design concept and 

scope have not changed significantly from 

those which were described in the TIP; and 

(2) If the TIP describes a project design 

concept and scope which includes projectlevel emissions mitigation or control 

measures, written commitments to implement 

such measures must be obtained from the 

project sponsor and/or operator as required by 

§93.125(a) in order for the project to be 

considered from a conforming program. Any 

change in these mitigation or control measures 

that would significantly reduce their 

effectiveness constitutes a change in the 

design concept and scope of the project. 

(d) TCMs. This criterion is not required to 

be satisfied for TCMs specifically included in 

an applicable implementation plan. 

(e) Notwithstanding the requirements of 

paragraphs (a), (b), and (c) of this section, a 

project must meet the requirements of 

§93.104(f) during the 12-month lapse grace 

period. 

§ 93.116 Criteria and procedures: 

Localized CO, PM10, and PM2.5 violations 

(hot-spots). 

(a) This paragraph applies at all times. 

The FHWA/FTA project must not cause or 

contribute to any new localized CO, PM10, 

and/or PM2.5 violations, increase the 

frequency or severity of any existing CO, 

PM10, and/or PM2.5 violations, or delay timely 

attainment of any NAAQS or any required 

interim emission reductions or other 

milestones in CO, PM10, and PM2.5 

28 
§93.116(a) ● §93.118(b) 

nonattainment and maintenance areas. This 

criterion is satisfied without a hot-spot 

analysis in PM10 and PM2.5 nonattainment and 

maintenance areas for FHWA/FTA projects 

that are not identified in §93.123(b)(1). This 

criterion is satisfied for all other FHWA/FTA 

projects in CO, PM10 and PM2.5 nonattainment 

and maintenance areas if it is demonstrated 

that during the time frame of the 

transportation plan no new local violations 

will be created and the severity or number of 

existing violations will not be increased as a 

result of the project, and the project has been 

included in a regional emissions analysis that 

meets applicable §§93.118 and/or 93.119 

requirements. The demonstration must be 

performed according to the consultation 

requirements of §93.105(c)(1)(i) and the 

methodology requirements of §93.123. 

(b) This paragraph applies for CO 

nonattainment areas as described in 

§93.109(f)(1). Each FHWA/FTA project must 

eliminate or reduce the severity and number of 

localized CO violations in the area 

substantially affected by the project (in CO 

nonattainment areas). This criterion is 

satisfied with respect to existing localized CO 

violations if it is demonstrated that during the 

time frame of the transportation plan (or 

regional emissions analysis) existing localized 

CO violations will be eliminated or reduced in 

severity and number as a result of the project. 

The demonstration must be performed 

according to the consultation requirements of 

§93.105(c)(1)(i) and the methodology 

requirements of §93.123. 

§ 93.117 Criteria and procedures: 

Compliance with PM10 and PM2.5 control 

measures. 

The FHWA/FTA project must comply with 

any PM10 and PM2.5 control measures in the 

applicable implementation plan. This criterion 

is satisfied if the project-level conformity 

determination contains a written commitment 

from the project sponsor to include in the final 

plans, specifications, and estimates for the 

project those control measures (for the 

purpose of limiting PM10 and PM2.5 emissions 

from the construction activities and/or normal 

use and operation associated with the project) 

that are contained in the applicable 

implementation plan. 

§ 93.118 Criteria and procedures: Motor 

vehicle emissions budget. 

(a) The transportation plan, TIP, and 

project not from a conforming transportation 

plan and TIP must be consistent with the 

motor vehicle emissions budget(s) in the 

applicable implementation plan (or 

implementation plan submission). This 

criterion applies as described in §93.109(c) 

through (n). This criterion is satisfied if it is 

demonstrated that emissions of the pollutants 

or pollutant precursors described in paragraph 

(c) of this section are less than or equal to the 

motor vehicle emissions budget(s) established 

in the applicable implementation plan or 

implementation plan submission. 

(b) Consistency with the motor vehicle 

emissions budget(s) must be demonstrated for 

each year for which the applicable (and/or 

submitted) implementation plan specifically 

establishes motor vehicle emissions budget(s), 

for the attainment year (if it is within the 

timeframe of the transportation plan and 

conformity determination), for the last year of 

the timeframe of the conformity determination 

(as described under §93.106(d)), and for any 

intermediate years within the timeframe of the 

conformity determination as necessary so that 

the years for which consistency is 

demonstrated are no more than ten years apart, 

as follows: 

(1) Until a maintenance plan is submitted: 

(i) Emissions in each year (such as 

milestone years and the attainment year) for 

which the control strategy implementation 

plan revision establishes motor vehicle 

29 
§93.118(b) – (d) 

emissions budget(s) must be less than or equal 

to that year's motor vehicle emissions 

budget(s); and 

(ii) Emissions in years for which no motor 

vehicle emissions budget(s) are specifically 

established must be less than or equal to the 

motor vehicle emissions budget(s) established 

for the most recent prior year. For example, 

emissions in years after the attainment year for 

which the implementation plan does not 

establish a budget must be less than or equal 

to the motor vehicle emissions budget(s) for 

the attainment year. 

(2) When a maintenance plan has been 

submitted: 

(i) Emissions must be less than or equal to 

the motor vehicle emissions budget(s) 

established for the last year of the 

maintenance plan, and for any other years for 

which the maintenance plan establishes motor 

vehicle emissions budgets. If the maintenance 

plan does not establish motor vehicle 

emissions budgets for any years other than the 

last year of the maintenance plan, the 

demonstration of consistency with the motor 

vehicle emissions budget(s) must be 

accompanied by a qualitative finding that 

there are no factors which would cause or 

contribute to a new violation or exacerbate an 

existing violation in the years before the last 

year of the maintenance plan. The interagency 

consultation process required by §93.105 shall 

determine what must be considered in order to 

make such a finding; 

(ii) For years after the last year of the 

maintenance plan, emissions must be less than 

or equal to the maintenance plan's motor 

vehicle emissions budget(s) for the last year of 

the maintenance plan; 

(iii) If an approved and/or submitted 

control strategy implementation plan has 

established motor vehicle emissions budgets 

for years in the time frame of the 

transportation plan, emissions in these years 

must be less than or equal to the control 

strategy implementation plan's motor vehicle 

emissions budget(s) for these years; and 

(iv) For any analysis years before the last 

year of the maintenance plan, emissions must 

be less than or equal to the motor vehicle 

emissions budget(s) established for the most 

recent prior year. 

(c) Consistency with the motor vehicle 

emissions budget(s) must be demonstrated for 

each pollutant or pollutant precursor in 

§93.102(b) for which the area is in 

nonattainment or maintenance and for which 

the applicable implementation plan (or 

implementation plan submission) establishes a 

motor vehicle emissions budget. 

(d) Consistency with the motor vehicle 

emissions budget(s) must be demonstrated by 

including emissions from the entire 

transportation system, including all regionally 

significant projects contained in the 

transportation plan and all other regionally 

significant highway and transit projects 

expected in the nonattainment or maintenance 

area in the timeframe of the transportation 

plan. 

(1) Consistency with the motor vehicle 

emissions budget(s) must be demonstrated 

with a regional emissions analysis that meets 

the requirements of §§93.122 and 

93.105(c)(1)(i). 

(2) The regional emissions analysis may be 

performed for any years in the timeframe of 

the conformity determination (as described 

under §93.106(d)) provided they are not more 

than ten years apart and provided the analysis 

is performed for the attainment year (if it is in 

the timeframe of the transportation plan and 

conformity determination) and the last year of 

the timeframe of the conformity 

determination. Emissions in years for which 

consistency with motor vehicle emissions 

budgets must be demonstrated, as required in 

paragraph (b) of this section, may be 

determined by interpolating between the years 

30 
§93.118(d) – (e) 

for which the regional emissions analysis is 

performed. 

(3) When the timeframe of the conformity 

determination is shortened under 

§93.106(d)(2), 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 shown to exceed motor vehicle 

emissions budgets in a prior regional 

emissions analysis (if such a year extends 

beyond the timeframe of the conformity 

determination). 

(e) Motor vehicle emissions budgets in 

submitted control strategy implementation 

plan revisions and submitted maintenance 

plans. 

(1) Consistency with the motor vehicle 

emissions budgets in submitted control 

strategy implementation plan revisions or 

maintenance plans must be demonstrated if 

EPA has declared the motor vehicle emissions 

budget(s) adequate for transportation 

conformity purposes, and the adequacy 

finding is effective. However, motor vehicle 

emissions budgets in submitted 

implementation plans do not supersede the 

motor vehicle emissions budgets in approved 

implementation plans for the same Clean Air 

Act requirement and the period of years 

addressed by the previously approved 

implementation plan, unless EPA specifies 

otherwise in its approval of a SIP. 

(2) If EPA has not declared an 

implementation plan submission's motor 

vehicle emissions budget(s) adequate for 

transportation conformity purposes, the 

budget(s) shall not be used to satisfy the 

requirements of this section. Consistency with 

the previously established motor vehicle 

emissions budget(s) must be demonstrated. If 

there are no previously approved 

implementation plans or implementation plan 

submissions with adequate motor vehicle 

emissions budgets, the interim emissions tests 

required by §93.119 must be satisfied. 

(3) If EPA declares an implementation plan 

submission's motor vehicle emissions 

budget(s) inadequate for transportation 

conformity purposes after EPA had previously 

found the budget(s) adequate, and conformity 

of a transportation plan or TIP has already 

been determined by DOT using the budget(s), 

the conformity determination will remain 

valid. Projects included in that transportation 

plan or TIP could still satisfy §§93.114 and 

93.115, which require a currently conforming 

transportation plan and TIP to be in place at 

the time of a project's conformity 

determination and that projects come from a 

conforming transportation plan and TIP. 

(4) EPA will not find a motor vehicle 

emissions budget in a submitted control 

strategy implementation plan revision or 

maintenance plan to be adequate for 

transportation conformity purposes unless the 

following minimum criteria are satisfied: 

(i) The submitted control strategy 

implementation plan revision or maintenance 

plan was endorsed by the Governor (or his or 

her designee) and was subject to a State public 

hearing; 

(ii) Before the control strategy 

implementation plan or maintenance plan was 

submitted to EPA, consultation among federal, 

State, and local agencies occurred; full 

implementation plan documentation was 

provided to EPA; and EPA's stated concerns, 

if any, were addressed; 

(iii) The motor vehicle emissions budget(s) 

is clearly identified and precisely quantified; 

(iv) The motor vehicle emissions budget(s), 

when considered together with all other 

emissions sources, is consistent with 

applicable requirements for reasonable further 

progress, attainment, or maintenance 

(whichever is relevant to the given 

implementation plan submission); 

(v) The motor vehicle emissions budget(s) 

is consistent with and clearly related to the 

31 
§93.118(e) – (f) 

emissions inventory and the control measures 

in the submitted control strategy 

implementation plan revision or maintenance 

plan; and 

(vi) Revisions to previously submitted 

control strategy implementation plans or 

maintenance plans explain and document any 

changes to previously submitted budgets and 

control measures; impacts on point and area 

source emissions; any changes to established 

safety margins (see §93.101 for definition); 

and reasons for the changes (including the 

basis for any changes related to emission 

factors or estimates of vehicle miles traveled). 

(5) Before determining the adequacy of a 

submitted motor vehicle emissions budget, 

EPA will review the State's compilation of 

public comments and response to comments 

that are required to be submitted with any 

implementation plan. EPA will document its 

consideration of such comments and responses 

in a letter to the State indicating the adequacy 

of the submitted motor vehicle emissions 

budget. 

(6) When the motor vehicle emissions 

budget(s) used to satisfy the requirements of 

this section are established by an 

implementation plan submittal that has not yet 

been approved or disapproved by EPA, the 

MPO and DOT's conformity determinations 

will be deemed to be a statement that the MPO 

and DOT are not aware of any information 

that would indicate that emissions consistent 

with the motor vehicle emissions budget will 

cause or contribute to any new violation of 

any standard; increase the frequency or 

severity of any existing violation of any 

standard; or delay timely attainment of any 

standard or any required interim emission 

reductions or other milestones. 

(f) Adequacy review process for 

implementation plan submissions. EPA will 

use the procedure listed in paragraph (f)(1) or 

(f)(2) of this section to review the adequacy of 

an implementation plan submission: 

(1) When EPA reviews the adequacy of an 

implementation plan submission prior to 

EPA's final action on the implementation plan, 

(i) EPA will notify the public through 

EPA's website when EPA receives an 

implementation plan submission that will be 

reviewed for adequacy. 

(ii) The public will have a minimum of 30 

days to comment on the adequacy of the 

implementation plan submission. If the 

complete implementation plan is not 

accessible electronically through the internet 

and a copy is requested within 15 days of the 

date of the website notice, the comment period 

will be extended for 30 days from the date that 

a copy of the implementation plan is mailed. 

(iii) After the public comment period 

closes, EPA will inform the State in writing 

whether EPA has found the submission 

adequate or inadequate for use in 

transportation conformity, including response 

to any comments submitted directly and 

review of comments submitted through the 

State process, or EPA will include the 

determination of adequacy or inadequacy in a 

proposed or final action approving or 

disapproving the implementation plan under 

paragraph (f)(2)(iii) of this section. 

(iv) EPA will publish a Federal Register 

notice to inform the public of EPA's finding. 

If EPA finds the submission adequate, the 

effective date of this finding will be 15 days 

from the date the notice is published as 

established in the Federal Register notice, 

unless EPA is taking a final approval action 

on the SIP as described in paragraph (f)(2)(iii) 

of this section. 

(v) EPA will announce whether the 

implementation plan submission is adequate 

or inadequate for use in transportation 

conformity on EPA's website. The website 

will also include EPA's response to comments 

if any comments were received during the 

public comment period. 

(vi) If after EPA has found a submission 

adequate, EPA has cause to reconsider this 

32 
§93.118(f) ● §93.119(b) 

finding, EPA will repeat actions described in 

paragraphs (f)(1)(i) through (v) or (f)(2) of 

this section unless EPA determines that there 

is no need for additional public comment 

given the deficiencies of the implementation 

plan submission. In all cases where EPA 

reverses its previous finding to a finding of 

inadequacy under paragraph (f)(1) of this 

section, such a finding will become effective 

immediately upon the date of EPA's letter to 

the State. 

(vii) If after EPA has found a submission 

inadequate, EPA has cause to reconsider the 

adequacy of that budget, EPA will repeat 

actions described in paragraphs (f)(1)(i) 

through (v) or (f)(2) of this section. 

(2) When EPA reviews the adequacy of an 

implementation plan submission 

simultaneously with EPA's approval or 

disapproval of the implementation plan, 

(i) EPA's Federal Register notice of 

proposed or direct final rulemaking will serve 

to notify the public that EPA will be 

reviewing the implementation plan submission 

for adequacy. 

(ii) The publication of the notice of 

proposed rulemaking will start a public 

comment period of at least 30 days. 

(iii) EPA will indicate whether the 

implementation plan submission is adequate 

and thus can be used for conformity either in 

EPA's final rulemaking or through the process 

described in paragraphs (f)(1)(iii) through (v) 

of this section. If EPA makes an adequacy 

finding through a final rulemaking that 

approves the implementation plan submission, 

such a finding will become effective upon the 

publication date of EPA's approval in the 

Federal Register, or upon the effective date of 

EPA's approval if such action is conducted 

through direct final rulemaking. EPA will 

respond to comments received directly and 

review comments submitted through the State 

process and include the response to comments 

in the applicable docket. 

§ 93.119 Criteria and procedures: Interim 

emissions in areas without motor vehicle 

emissions budgets. 

(a) The transportation plan, TIP, and 

project not from a conforming transportation 

plan and TIP must satisfy the interim 

emissions test(s) as described in §93.109(c) 

through (n). This criterion applies to the net 

effect of the action (transportation plan, TIP, 

or project not from a conforming plan and 

TIP) on motor vehicle emissions from the 

entire transportation system. 

(b) Ozone areas. The requirements of this 

paragraph apply to all 1-hour ozone and 8-

hour ozone NAAQS areas, except for certain 

requirements as indicated. This criterion may 

be met: 

(1) In moderate and above ozone 

nonattainment areas that are subject to the 

reasonable further progress requirements of 

CAA section 182(b)(1) if a regional emissions 

analysis that satisfies the requirements of 

§93.122 and paragraphs (g) through (j) of this 

section demonstrates that for each analysis 

year and for each of the pollutants described 

in paragraph (f) of this section: 

(i) The emissions predicted in the “Action” 

scenario are less than the emissions predicted 

in the “Baseline” scenario, and this can be 

reasonably expected to be true in the periods 

between the analysis years; and 

(ii) The emissions predicted in the 

“Action” scenario are lower than: 

(A) 1990 emissions by any nonzero 

amount, in areas for the 1-hour ozone NAAQS 

as described in §93.109(c); or 

(B) 2002 emissions by any nonzero 

amount, in areas for the 8-hour ozone NAAQS 

as described in §93.109(d) and (e). 

(2) In marginal and below ozone 

nonattainment areas and other ozone 

nonattainment areas that are not subject to the 

reasonable further progress requirements of 

CAA section 182(b)(1) if a regional emissions 

analysis that satisfies the requirements of 

33 
§93.119(b) – (e) 

§93.122 and paragraphs (g) through (j) of this 

section demonstrates that for each analysis 

year and for each of the pollutants described 

in paragraph (f) of this section: 

(i) The emissions predicted in the “Action” 

scenario are not greater than the emissions 

predicted in the “Baseline” scenario, and this 

can be reasonably expected to be true in the 

periods between the analysis years; or 

(ii) The emissions predicted in the 

“Action” scenario are not greater than: 

(A) 1990 emissions, in areas for the 1-hour 

ozone NAAQS as described in §93.109(c); or 

(B) 2002 emissions, in areas for the 8-hour 

ozone NAAQS as described in §93.109(d) and 

(e). 

(c) CO areas. This criterion may be met: 

(1) In moderate areas with design value 

greater than 12.7 ppm and serious CO 

nonattainment areas that are subject to CAA 

section 187(a)(7) if a regional emissions 

analysis that satisfies the requirements of 

§93.122 and paragraphs (g) through (j) of this 

section demonstrates that for each analysis 

year and for each of the pollutants described 

in paragraph (f) of this section: 

(i) The emissions predicted in the “Action” 

scenario are less than the emissions predicted 

in the “Baseline” scenario, and this can be 

reasonably expected to be true in the periods 

between the analysis years; and 

(ii) The emissions predicted in the 

“Action” scenario are lower than 1990 

emissions by any nonzero amount. 

(2) In moderate areas with design value 

less than 12.7 ppm and not classified CO 

nonattainment areas if a regional emissions 

analysis that satisfies the requirements of 

§93.122 and paragraphs (g) through (j) of this 

section demonstrates that for each analysis 

year and for each of the pollutants described 

in paragraph (f) of this section: 

(i) The emissions predicted in the “Action” 

scenario are not greater than the emissions 

predicted in the “Baseline” scenario, and this 

can be reasonably expected to be true in the 

periods between the analysis years; or 

(ii) The emissions predicted in the 

“Action” scenario are not greater than 1990 

emissions. 

(d) PM10 and NO2 areas. This criterion 

may be met in PM10 and NO2 nonattainment 

areas if a regional emissions analysis that 

satisfies the requirements of §93.122 and 

paragraphs (g) through (j) of this section 

demonstrates that for each analysis year and 

for each of the pollutants described in 

paragraph (f) of this section, one of the 

following requirements is met: 

(1) The emissions predicted in the “Action” 

scenario are not greater than the emissions 

predicted in the “Baseline” scenario, and this 

can be reasonably expected to be true in the 

periods between the analysis years; or 

(2) The emissions predicted in the “Action” 

scenario are not greater than baseline 

emissions. Baseline emissions are those 

estimated to have occurred during calendar 

year 1990, unless the conformity 

implementation plan revision required by 

§51.390 of this chapter defines the baseline 

emissions for a PM10 area to be those 

occurring in a different calendar year for 

which a baseline emissions inventory was 

developed for the purpose of developing a 

control strategy implementation plan. 

(e) PM2.5 areas. This criterion may be met 

in PM2.5 nonattainment areas if a regional 

emissions analysis that satisfies the 

requirements of §93.122 and paragraphs (g) 

through (j) of this section demonstrates that 

for each analysis year and for each of the 

pollutants described in paragraph (f) of this 

section, one of the following requirements is 

met: 

(1) The emissions predicted in the “Action” 

scenario are not greater than the emissions 

predicted in the “Baseline” scenario, and this 

can be reasonably expected to be true in the 

34 
§93.119(e) – (g) 

periods between the analysis years; or 

(2) The emissions predicted in the “Action” 

scenario are not greater than: 

(A) 2002 emissions, in areas designated 

nonattainment for the 1997 PM2.5 NAAQS; or 

(B) Emissions in the most recent year for 

which EPA’s Air Emissions Reporting 

Requirements (40 CFR Part 51, Subpart A) 

requires submission of on-road mobile source 

emissions inventories, as of the effective date 

of nonattainment designations for any PM2.5 

NAAQS other than the 1997 PM2.5 NAAQS. 

(f) Pollutants. The regional emissions 

analysis must be performed for the following 

pollutants: 

(1) VOC in ozone areas; 

(2) NOX in ozone areas, unless the EPA 

Administrator determines that additional 

reductions of NOX would not contribute to 

attainment; 

(3) CO in CO areas; 

(4) PM10 in PM10 areas; 

(5) VOC and/or NOX in PM10 areas if the 

EPA Regional Administrator or the director of 

the State air agency has made a finding that 

one or both of such precursor emissions from 

within the area are a significant contributor to 

the PM10 nonattainment problem and has so 

notified the MPO and DOT; 

(6) NOX in NO2areas; 

(7) PM2.5 in PM2.5 areas; 

(8) Reentrained road dust in PM2.5 areas 

only if the EPA Regional Administrator or the 

director of the State air agency has made a 

finding that emissions from reentrained road 

dust within the area are a significant 

contributor to the PM2.5 nonattainment 

problem and has so notified the MPO and 

DOT; 

(9) NOX in PM2.5 areas, unless the EPA 

Regional Administrator and the director of the 

State air agency have made a finding that 

emissions of NOX from within the area are not 

a significant contributor to the PM2.5 

nonattainment problem and has so notified the 

MPO and DOT; and 

(10) VOC, SO2 and/or ammonia in PM2.5 

areas if the EPA Regional Administrator or 

the director of the State air agency has made a 

finding that any of such precursor emissions 

from within the area are a significant 

contributor to the PM2.5 nonattainment 

problem and has so notified the MPO and 

DOT. 

(g) Analysis years. 

(1) The regional emissions analysis must 

be performed for analysis years that are no 

more than ten years apart. The first analysis 

year must be no more than five years beyond 

the year in which the conformity 

determination is being made. The last year of 

the timeframe of the conformity determination 

(as described under §93.106(d)) must also be 

an analysis year. 

(2) For areas using paragraphs (b)(2)(i), 

(c)(2)(i), (d)(1), and (e)(1) of this section, a 

regional emissions analysis that satisfies the 

requirements of §93.122 and paragraphs (g) 

through (j) of this section would not be 

required for analysis years in which the 

transportation projects and planning 

assumptions in the “Action” and “Baseline” 

scenarios are exactly the same. In such a case, 

paragraph (a) of this section can be satisfied 

by documenting that the transportation 

projects and planning assumptions in both 

scenarios are exactly the same, and 

consequently, the emissions predicted in the 

“Action” scenario are not greater than the 

emissions predicted in the “Baseline” scenario 

for such analysis years. 

(3) When the timeframe of the conformity 

determination is shortened under 

§93.106(d)(2), the conformity determination 

must be accompanied by a regional emissions 

analysis (for informational purposes only) for 

the last year of the transportation plan. 

35 
§93.119(h) – (i) 

(h) “Baseline” scenario. The regional 

emissions analysis required by paragraphs (b) 

through (e) of this section must estimate the 

emissions that would result from the 

“Baseline” scenario in each analysis year. The 

“Baseline” scenario must be defined for each 

of the analysis years. The “Baseline” scenario 

is the future transportation system that will 

result from current programs, including the 

following (except that exempt projects listed 

in §93.126 and projects exempt from regional 

emissions analysis as listed in §93.127 need 

not be explicitly considered): 

(1) All in-place regionally significant 

highway and transit facilities, services and 

activities; 

(2) All ongoing travel demand management 

or transportation system management 

activities; and 

(3) Completion of all regionally significant 

projects, regardless of funding source, which 

are currently under construction or are 

undergoing right-of-way acquisition (except 

for hardship acquisition and protective 

buying); come from the first year of the 

previously conforming transportation plan 

and/or TIP; or have completed the NEPA 

process. 

(i) “Action” scenario. The regional 

emissions analysis required by paragraphs (b) 

through (e) of this section must estimate the 

emissions that would result from the “Action” 

scenario in each analysis year. The “Action” 

scenario must be defined for each of the 

analysis years. The “Action” scenario is the 

transportation system that would result from 

the implementation of the proposed action 

(transportation plan, TIP, or project not from a 

conforming transportation plan and TIP) and 

all other expected regionally significant 

projects in the nonattainment area. The 

“Action” scenario must include the following 

(except that exempt projects listed in §93.126 

and projects exempt from regional emissions 

analysis as listed in §93.127 need not be 

explicitly considered): 

(1) All facilities, services, and activities in 

the “Baseline” scenario; 

(2) Completion of all TCMs and regionally 

significant projects (including facilities, 

services, and activities) specifically identified 

in the proposed transportation plan which will 

be operational or in effect in the analysis year, 

except that regulatory TCMs may not be 

assumed to begin at a future time unless the 

regulation is already adopted by the enforcing 

jurisdiction or the TCM is identified in the 

applicable implementation plan; 

(3) All travel demand management 

programs and transportation system 

management activities known to the MPO, but 

not included in the applicable implementation 

plan or utilizing any Federal funding or 

approval, which have been fully adopted 

and/or funded by the enforcing jurisdiction or 

sponsoring agency since the last conformity 

determination; 

(4) The incremental effects of any travel 

demand management programs and 

transportation system management activities 

known to the MPO, but not included in the 

applicable implementation plan or utilizing 

any Federal funding or approval, which were 

adopted and/or funded prior to the date of the 

last conformity determination, but which have 

been modified since then to be more stringent 

or effective; 

(5) Completion of all expected regionally 

significant highway and transit projects which 

are not from a conforming transportation plan 

and TIP; and 

(6) Completion of all expected regionally 

significant non-FHWA/FTA highway and 

transit projects that have clear funding sources 

and commitments leading toward their 

implementation and completion by the 

analysis year. 

36 
§93.119(j) ● §93.121(a) 

(j) Projects not from a conforming 

transportation plan and TIP. For the regional 

emissions analysis required by paragraphs (b) 

through (e) of this section, if the project which 

is not from a conforming transportation plan 

and TIP is a modification of a project 

currently in the plan or TIP, the ‘Baseline’ 

scenario must include the project with its 

original design concept and scope, and the 

‘Action’ scenario must include the project 

with its new design concept and scope. 

§ 93.120 Consequences of control 

strategy implementation plan failures. 

(a) Disapprovals. 

(1) If EPA disapproves any submitted 

control strategy implementation plan revision 

(with or without a protective finding), the 

conformity status of the transportation plan 

and TIP shall lapse on the date that highway 

sanctions as a result of the disapproval are 

imposed on the nonattainment area under 

section 179(b)(1) of the CAA. No new 

transportation plan, TIP, or project may be 

found to conform until another control 

strategy implementation plan revision 

fulfilling the same CAA requirements is 

submitted and conformity to this submission is 

determined. 

(2) If EPA disapproves a submitted control 

strategy implementation plan revision without 

making a protective finding, only projects in 

the first four years of the currently conforming 

transportation plan and TIP or that meet the 

requirements of §93.104(f) during the 12-

month lapse grace period may be found to 

conform. This means that beginning on the 

effective date of a disapproval without a 

protective finding, no transportation plan, TIP, 

or project not in the first four years of the 

currently conforming transportation plan and 

TIP or that meets the requirements of 

§93.104(f) during the 12-month lapse grace 

period may be found to conform until another 

control strategy implementation plan revision 

fulfilling the same CAA requirements is 

submitted, EPA finds its motor vehicle 

emissions budget(s) adequate pursuant to 

§93.118 or approves the submission, and 

conformity to the implementation plan 

revision is determined. 

(3) In disapproving a control strategy 

implementation plan revision, EPA would 

give a protective finding where a submitted 

plan contains adopted control measures or 

written commitments to adopt enforceable 

control measures that fully satisfy the 

emissions reductions requirements relevant to 

the statutory provision for which the 

implementation plan revision was submitted, 

such as reasonable further progress or 

attainment. 

(b) Failure to submit and incompleteness. 

In areas where EPA notifies the State, MPO, 

and DOT of the State's failure to submit a 

control strategy implementation plan or 

submission of an incomplete control strategy 

implementation plan revision (either of which 

initiates the sanction process under CAA 

sections 179 or 110(m)), the conformity status 

of the transportation plan and TIP shall lapse 

on the date that highway sanctions are 

imposed on the nonattainment area for such 

failure under section 179(b)(1) of the CAA, 

unless the failure has been remedied and 

acknowledged by a letter from the EPA 

Regional Administrator. 

(c) Federal implementation plans. If EPA 

promulgates a Federal implementation plan 

that contains motor vehicle emissions 

budget(s) as a result of a State failure, the 

conformity lapse imposed by this section 

because of that State failure is removed. 

§ 93.121 Requirements for adoption or 

approval of projects by other recipients of 

funds designated under title 23 U.S.C. or 

the Federal Transit Laws. 

(a) Except as provided in paragraph (b) of 

this section, no recipient of Federal funds 

37 
§93.121(a) - (c) 

designated under title 23 U.S.C. or the Federal 

Transit Laws shall adopt or approve a 

regionally significant highway or transit 

project, regardless of funding source, unless 

the recipient finds that the requirements of one 

of the following are met: 

(1) The project comes from the currently 

conforming transportation plan and TIP (or 

meets the requirements of §93.104(f) during 

the 12-month lapse grace period), and the 

project's design concept and scope have not 

changed significantly from those that were 

included in the regional emissions analysis for 

that transportation plan and TIP; 

(2) The project is included in the regional 

emissions analysis for the currently 

conforming transportation plan and TIP 

conformity determination (or meets the 

requirements of §93.104(f) during the 12-

month lapse grace period), even if the project 

is not strictly included in the transportation 

plan or TIP for the purpose of MPO project 

selection or endorsement, and the project's 

design concept and scope have not changed 

significantly from those that were included in 

the regional emissions analysis; or 

(3) A new regional emissions analysis 

including the project and the currently 

conforming transportation plan and TIP 

demonstrates that the transportation plan and 

TIP would still conform if the project were 

implemented (consistent with the 

requirements of §§93.118 and/or 93.119 for a 

project not from a conforming transportation 

plan and TIP). 

(b) In isolated rural nonattainment and 

maintenance areas subject to §93.109(n), no 

recipient of Federal funds designated under 

title 23 U.S.C. or the Federal Transit Laws 

shall adopt or approve a regionally significant 

highway or transit project, regardless of 

funding source, unless the recipient finds that 

the requirements of one of the following are 

met: 

(1) The project was included in the regional 

emissions analysis supporting the most recent 

conformity determination that reflects the 

portion of the statewide transportation plan 

and statewide TIP which are in the 

nonattainment or maintenance area, and the 

project's design concept and scope has not 

changed significantly; or 

(2) A new regional emissions analysis 

including the project and all other regionally 

significant projects expected in the 

nonattainment or maintenance area 

demonstrates that those projects in the 

statewide transportation plan and statewide 

TIP which are in the nonattainment or 

maintenance area would still conform if the 

project were implemented (consistent with the 

requirements of §§93.118 and/or 93.119 for 

projects not from a conforming transportation 

plan and TIP). 

(c) Notwithstanding paragraphs (a) and (b) 

of this section, in nonattainment and 

maintenance areas subject to §93.109(l) or (m) 

for a given pollutant/precursor and NAAQS, 

no recipient of Federal funds designated under 

title 23 U.S.C. or the Federal Transit Laws 

shall adopt or approve a regionally significant 

highway or transit project, regardless of 

funding source, unless the recipient finds that 

the requirements of one of the following are 

met for that pollutant/precursor and NAAQS: 

(1) The project was included in the most 

recent conformity determination for the 

transportation plan and TIP and the project's 

design concept and scope has not changed 

significantly; or 

(2) The project was included in the most 

recent conformity determination that reflects 

the portion of the statewide transportation plan 

and statewide TIP which are in the 

nonattainment or maintenance area, and the 

project's design concept and scope has not 

changed significantly. 

38 
§93.122(a) 

§ 93.122 Procedures for determining 

regional transportation-related emissions. 

(a) General requirements. 

(1) The regional emissions analysis 

required by §§93.118 and 93.119 for the 

transportation plan, TIP, or project not from a 

conforming plan and TIP must include all 

regionally significant projects expected in the 

nonattainment or maintenance area. The 

analysis shall include FHWA/FTA projects 

proposed in the transportation plan and TIP 

and all other regionally significant projects 

which are disclosed to the MPO as required by 

§93.105. Projects which are not regionally 

significant are not required to be explicitly 

modeled, but vehicle miles traveled (VMT) 

from such projects must be estimated in 

accordance with reasonable professional 

practice. The effects of TCMs and similar 

projects that are not regionally significant may 

also be estimated in accordance with 

reasonable professional practice. 

(2) The emissions analysis may not include 

for emissions reduction credit any TCMs or 

other measures in the applicable 

implementation plan which have been delayed 

beyond the scheduled date(s) until such time 

as their implementation has been assured. If 

the measure has been partially implemented 

and it can be demonstrated that it is providing 

quantifiable emission reduction benefits, the 

emissions analysis may include that emissions 

reduction credit. 

(3) Emissions reduction credit from 

projects, programs, or activities which require 

a regulatory action in order to be implemented 

may not be included in the emissions analysis 

unless: 

(i) The regulatory action is already adopted 

by the enforcing jurisdiction; 

(ii) The project, program, or activity is 

included in the applicable implementation 

plan; 

(iii) The control strategy implementation 

plan submission or maintenance plan 

submission that establishes the motor vehicle 

emissions budget(s) for the purposes of 

§93.118 contains a written commitment to the 

project, program, or activity by the agency 

with authority to implement it; or 

(iv) EPA has approved an opt-in to a 

Federally enforced program, EPA has 

promulgated the program (if the control 

program is a Federal responsibility, such as 

vehicle tailpipe standards), or the Clean Air 

Act requires the program without need for 

individual State action and without any 

discretionary authority for EPA to set its 

stringency, delay its effective date, or not 

implement the program. 

(4) Emissions reduction credit from control 

measures that are not included in the 

transportation plan and TIP and that do not 

require a regulatory action in order to be 

implemented may not be included in the 

emissions analysis unless the conformity 

determination includes written commitments 

to implementation from the appropriate 

entities. 

(i) Persons or entities voluntarily 

committing to control measures must comply 

with the obligations of such commitments. 

(ii) The conformity implementation plan 

revision required in §51.390 of this chapter 

must provide that written commitments to 

control measures that are not included in the 

transportation plan and TIP must be obtained 

prior to a conformity determination and that 

such commitments must be fulfilled. 

(5) A regional emissions analysis for the 

purpose of satisfying the requirements of 

§93.119 must make the same assumptions in 

both the “Baseline” and “Action” scenarios 

regarding control measures that are external to 

the transportation system itself, such as 

vehicle tailpipe or evaporative emission 

standards, limits on gasoline volatility, vehicle 

inspection and maintenance programs, and 

oxygenated or reformulated gasoline or diesel 

fuel. 

(6) The ambient temperatures used for the 

regional emissions analysis shall be consistent 

39 
§93.122(a) – (b) 

with those used to establish the emissions 

budget in the applicable implementation plan. 

All other factors, for example the fraction of 

travel in a hot stabilized engine mode, must be 

consistent with the applicable implementation 

plan, unless modified after interagency 

consultation according to §93.105(c)(1)(i) to 

incorporate additional or more geographically 

specific information or represent a logically 

estimated trend in such factors beyond the 

period considered in the applicable 

implementation plan. 

(7) Reasonable methods shall be used to 

estimate nonattainment or maintenance area 

VMT on off-network roadways within the 

urban transportation planning area, and on 

roadways outside the urban transportation 

planning area. 

(b) Regional emissions analysis in serious, 

severe, and extreme ozone nonattainment 

areas and serious CO nonattainment areas 

must meet the requirements of paragraphs (b) 

(1) through (3) of this section if their 

metropolitan planning area contains an 

urbanized area population over 200,000. 

(1) By January 1, 1997, estimates of 

regional transportation-related emissions used 

to support conformity determinations must be 

made at a minimum using network-based 

travel models according to procedures and 

methods that are available and in practice and 

supported by current and available 

documentation. These procedures, methods, 

and practices are available from DOT and will 

be updated periodically. Agencies must 

discuss these modeling procedures and 

practices through the interagency consultation 

process, as required by §93.105(c)(1)(i). 

Network-based travel models must at a 

minimum satisfy the following requirements: 

(i) Network-based travel models must be 

validated against observed counts (peak and 

off-peak, if possible) for a base year that is not 

more than 10 years prior to the date of the 

conformity determination. Model forecasts 

must be analyzed for reasonableness and 

compared to historical trends and other 

factors, and the results must be documented; 

(ii) Land use, population, employment, and 

other network-based travel model assumptions 

must be documented and based on the best 

available information; 

(iii) Scenarios of land development and use 

must be consistent with the future 

transportation system alternatives for which 

emissions are being estimated. The 

distribution of employment and residences for 

different transportation options must be 

reasonable; 

(iv) A capacity-sensitive assignment 

methodology must be used, and emissions 

estimates must be based on a methodology 

which differentiates between peak and offpeak link volumes and speeds and uses speeds 

based on final assigned volumes; 

(v) Zone-to-zone travel impedances used to 

distribute trips between origin and destination 

pairs must be in reasonable agreement with 

the travel times that are estimated from final 

assigned traffic volumes. Where use of transit 

currently is anticipated to be a significant 

factor in satisfying transportation demand, 

these times should also be used for modeling 

mode splits; and 

(vi) Network-based travel models must be 

reasonably sensitive to changes in the time(s), 

cost(s), and other factors affecting travel 

choices. 

(2) Reasonable methods in accordance with 

good practice must be used to estimate traffic 

speeds and delays in a manner that is sensitive 

to the estimated volume of travel on each 

roadway segment represented in the networkbased travel model. 

(3) Highway Performance Monitoring 

System (HPMS) estimates of vehicle miles 

traveled (VMT) shall be considered the 

primary measure of VMT within the portion 

of the nonattainment or maintenance area and 

for the functional classes of roadways 

included in HPMS, for urban areas which are 

40 
§93.122(b) - (f) 

sampled on a separate urban area basis. For 

areas with network-based travel models, a 

factor (or factors) may be developed to 

reconcile and calibrate the network-based 

travel model estimates of VMT in the base 

year of its validation to the HPMS estimates 

for the same period. These factors may then be 

applied to model estimates of future VMT. In 

this factoring process, consideration will be 

given to differences between HPMS and 

network-based travel models, such as 

differences in the facility coverage of the 

HPMS and the modeled network description. 

Locally developed count- based programs and 

other departures from these procedures are 

permitted subject to the interagency 

consultation procedures of §93.105(c)(1)(i). 

(c) Two-year grace period for regional 

emissions analysis requirements in certain 

ozone and CO areas. The requirements of 

paragraph (b) of this section apply to such 

areas or portions of such areas that have not 

previously been required to meet these 

requirements for any existing NAAQS two 

years from the following: 

(1) The effective date of EPA's 

reclassification of an ozone or CO 

nonattainment area that has an urbanized area 

population greater than 200,000 to serious or 

above; 

(2) The official notice by the Census 

Bureau that determines the urbanized area 

population of a serious or above ozone or CO 

nonattainment area to be greater than 200,000; 

or, 

(3) The effective date of EPA's action that 

classifies a newly designated ozone or CO 

nonattainment area that has an urbanized area 

population greater than 200,000 as serious or 

above. 

(d) In all areas not otherwise subject to 

paragraph (b) of this section, regional 

emissions analyses must use those procedures 

described in paragraph (b) of this section if the 

use of those procedures has been the previous 

practice of the MPO. Otherwise, areas not 

subject to paragraph (b) of this section may 

estimate regional emissions using any 

appropriate methods that account for VMT 

growth by, for example, extrapolating 

historical VMT or projecting future VMT by 

considering growth in population and 

historical growth trends for VMT per person. 

These methods must also consider future 

economic activity, transit alternatives, and 

transportation system policies. 

(e) PM10 from construction-related fugitive 

dust. 

(1) For areas in which the implementation 

plan does not identify construction-related 

fugitive PM10 as a contributor to the 

nonattainment problem, the fugitive PM10 

emissions associated with highway and transit 

project construction are not required to be 

considered in the regional emissions analysis. 

(2) In PM10 nonattainment and 

maintenance areas with implementation plans 

which identify construction-related fugitive 

PM10 as a contributor to the nonattainment 

problem, the regional PM10 emissions analysis 

shall consider construction-related fugitive 

PM10 and shall account for the level of 

construction activity, the fugitive PM10 control 

measures in the applicable implementation 

plan, and the dust-producing capacity of the 

proposed activities. 

(f) PM2.5 from construction-related fugitive 

dust. 

(1) For PM2.5 areas in which the 

implementation plan does not identify 

construction-related fugitive PM2.5 as a 

significant contributor to the nonattainment 

problem, the fugitive PM2.5 emissions 

associated with highway and transit project 

construction are not required to be considered 

in the regional emissions analysis. 

(2) In PM2.5 nonattainment and 

maintenance areas with implementation plans 

41 
§93.122(f) ● §93.123(a) 

which identify construction-related fugitive 

PM2.5 as a significant contributor to the 

nonattainment problem, the regional PM2.5 

emissions analysis shall consider constructionrelated fugitive PM2.5 and shall account for the 

level of construction activity, the fugitive 

PM2.5 control measures in the applicable 

implementation plan, and the dust-producing 

capacity of the proposed activities. 

(g) Reliance on previous regional 

emissions analysis. 

(1) Conformity determinations for a new 

transportation plan and/or TIP may be 

demonstrated to satisfy the requirements of 

§§93.118 (“Motor vehicle emissions budget”) 

or 93.119 (“Interim emissions in areas without 

motor vehicle emissions budgets”) without 

new regional emissions analysis if the 

previous regional emissions analysis also 

applies to the new plan and/or TIP. This 

requires a demonstration that: 

(i) The new plan and/or TIP contain all 

projects which must be started in the plan and 

TIP's timeframes in order to achieve the 

highway and transit system envisioned by the 

transportation plan; 

(ii) All plan and TIP projects which are 

regionally significant are included in the 

transportation plan with design concept and 

scope adequate to determine their contribution 

to the transportation plan's and/or TIP's 

regional emissions at the time of the previous 

conformity determination; 

(iii) The design concept and scope of each 

regionally significant project in the new plan 

and/or TIP are not significantly different from 

that described in the previous transportation 

plan; and 

(iv) The previous regional emissions 

analysis is consistent with the requirements of 

§§93.118 (including that conformity to all 

currently applicable budgets is demonstrated) 

and/or 93.119, as applicable. 

(2) A project which is not from a 

conforming transportation plan and a 

conforming TIP may be demonstrated to 

satisfy the requirements of §93.118 or §93.119 

without additional regional emissions analysis 

if allocating funds to the project will not delay 

the implementation of projects in the 

transportation plan or TIP which are necessary 

to achieve the highway and transit system 

envisioned by the transportation plan, the 

previous regional emissions analysis is still 

consistent with the requirements of §93.118 

(including that conformity to all currently 

applicable budgets is demonstrated) and/or 

§93.119, as applicable, and if the project is 

either: 

(i) Not regionally significant; or 

(ii) Included in the conforming 

transportation plan (even if it is not 

specifically included in the latest conforming 

TIP) with design concept and scope adequate 

to determine its contribution to the 

transportation plan's regional emissions at the 

time of the transportation plan's conformity 

determination, and the design concept and 

scope of the project is not significantly 

different from that described in the 

transportation plan. 

(3) A conformity determination that relies 

on paragraph (g) of this section does not 

satisfy the frequency requirements of 

§93.104(b) or (c). 

§ 93.123 Procedures for determining 

localized CO, PM10, and PM2.5 

concentrations (hot-spot analysis).

 (a) CO hot-spot analysis. 

(1) The demonstrations required by 

§93.116 (“Localized CO, PM10, and PM2.5 

violations”) must be based on quantitative 

analysis using the applicable air quality 

models, data bases, and other requirements 

specified in 40 CFR part 51, Appendix W 

(Guideline on Air Quality Models). These 

procedures shall be used in the following 

cases, unless different procedures developed 

through the interagency consultation process 

42 
 

§93.123(a) – (b) 

required in §93.105 and approved by the EPA 

Regional Administrator are used: 

(i) For projects in or affecting locations, 

areas, or categories of sites which are 

identified in the applicable implementation 

plan as sites of violation or possible violation; 

(ii) For projects affecting intersections that 

are at Level-of-Service D, E, or F, or those 

that will change to Level-of-Service D, E, or F 

because of increased traffic volumes related to 

the project; 

(iii) For any project affecting one or more 

of the top three intersections in the 

nonattainment or maintenance area with 

highest traffic volumes, as identified in the 

applicable implementation plan; and 

(iv) For any project affecting one or more 

of the top three intersections in the 

nonattainment or maintenance area with the 

worst level of service, as identified in the 

applicable implementation plan. 

(2) In cases other than those described in 

paragraph (a)(1) of this section, the 

demonstrations required by §93.116 may be 

based on either: 

(i) Quantitative methods that represent 

reasonable and common professional practice; 

or 

(ii) A qualitative consideration of local 

factors, if this can provide a clear 

demonstration that the requirements of 

§93.116 are met. 

(3) DOT, in consultation with EPA, may 

also choose to make a categorical hot-spot 

finding that §93.116(a) is met without further 

hot-spot analysis for any project described in 

paragraphs (a)(1) and (a)(2) of this section 

based on appropriate modeling. DOT, in 

consultation with EPA, may also consider the 

current air quality circumstances of a given 

CO nonattainment or maintenance area in 

categorical hot-spot findings for applicable 

FHWA or FTA projects. 

(b) PM10 and PM2.5 hot-spot analyses. 

(1) The hot-spot demonstration required by 

§93.116 must be based on quantitative 

analysis methods for the following types of 

projects: 

(i) New highway projects that have a 

significant number of diesel vehicles, and 

expanded highway projects that have a 

significant increase in the number of diesel 

vehicles; 

(ii) Projects affecting intersections that are 

at Level-of-Service D, E, or F with a 

significant number of diesel vehicles, or those 

that will change to Level-of-Service D, E, or F 

because of increased traffic volumes from a 

significant number of diesel vehicles related to 

the project; 

(iii) New bus and rail terminals and transfer 

points that have a significant number of diesel 

vehicles congregating at a single location; 

(iv) Expanded bus and rail terminals and 

transfer points that significantly increase the 

number of diesel vehicles congregating at a 

single location; and 

(v) Projects in or affecting locations, areas, 

or categories of sites which are identified in 

the PM10 or PM2.5 applicable implementation 

plan or implementation plan submission, as 

appropriate, as sites of violation or possible 

violation. 

(2) Where quantitative analysis methods 

are not available, the demonstration required 

by §93.116 for projects described in paragraph 

(b)(1) of this section must be based on a 

qualitative consideration of local factors. 

(3) DOT, in consultation with EPA, may 

also choose to make a categorical hot-spot 

finding that §93.116 is met without further 

hot-spot analysis for any project described in 

paragraph (b)(1) of this section based on 

appropriate modeling. DOT, in consultation 

with EPA, may also consider the current air 

quality circumstances of a given PM2.5 or 

PM10 nonattainment or maintenance area in 

categorical hot-spot findings for applicable 

FHWA or FTA projects. 

43 
§93.123(b) ● §93.124(b) 

(4) The requirements for quantitative 

analysis contained in this paragraph (b) will 

not take effect until EPA releases modeling 

guidance on this subject and announces in the 

Federal Register that these requirements are 

in effect. 

(c) General requirements. 

(1) Estimated pollutant concentrations must 

be based on the total emissions burden which 

may result from the implementation of the 

project, summed together with future 

background concentrations. The total 

concentration must be estimated and analyzed 

at appropriate receptor locations in the area 

substantially affected by the project. 

(2) Hot-spot analyses must include the 

entire project, and may be performed only 

after the major design features which will 

significantly impact concentrations have been 

identified. The future background 

concentration should be estimated by 

multiplying current background by the ratio of 

future to current traffic and the ratio of future 

to current emission factors. 

(3) Hot-spot analysis assumptions must be 

consistent with those in the regional emissions 

analysis for those inputs which are required 

for both analyses. 

(4) CO, PM10, or PM2.5 mitigation or 

control measures shall be assumed in the hotspot analysis only where there are written 

commitments from the project sponsor and/or 

operator to implement such measures, as 

required by §93.125(a). 

(5) CO, PM10, and PM2.5 hot-spot analyses 

are not required to consider constructionrelated activities which cause temporary 

increases in emissions. Each site which is 

affected by construction-related activities shall 

be considered separately, using established 

“Guideline” methods. Temporary increases 

are defined as those which occur only during 

the construction phase and last five years or 

less at any individual site. 

§ 93.124 Using the motor vehicle emissions 

budget in the applicable implementation 

plan (or implementation plan submission). 

(a) In interpreting an applicable 

implementation plan (or implementation plan 

submission) with respect to its motor vehicle 

emissions budget(s), the MPO and DOT may 

not infer additions to the budget(s) that are not 

explicitly intended by the implementation plan 

(or submission). Unless the implementation 

plan explicitly quantifies the amount by which 

motor vehicle emissions could be higher while 

still allowing a demonstration of compliance 

with the milestone, attainment, or maintenance 

requirement and explicitly states an intent that 

some or all of this additional amount should 

be available to the MPO and DOT in the 

emissions budget for conformity purposes, the 

MPO may not interpret the budget to be 

higher than the implementation plan's estimate 

of future emissions. This applies in particular 

to applicable implementation plans (or 

submissions) which demonstrate that after 

implementation of control measures in the 

implementation plan: 

(1) Emissions from all sources will be less 

than the total emissions that would be 

consistent with a required demonstration of an 

emissions reduction milestone; 

(2) Emissions from all sources will result in 

achieving attainment prior to the attainment 

deadline and/or ambient concentrations in the 

attainment deadline year will be lower than 

needed to demonstrate attainment; or 

(3) Emissions will be lower than needed to 

provide for continued maintenance. 

(b) A conformity demonstration shall not 

trade emissions among budgets which the 

applicable implementation plan (or 

implementation plan submission) allocates for 

different pollutants or precursors, or among 

budgets allocated to motor vehicles and other 

sources, unless the implementation plan 

establishes appropriate mechanisms for such 

trades. 

44 
 

§93.124(c) ● §93.126 

(c) If the applicable implementation plan 

(or implementation plan submission) estimates 

future emissions by geographic subarea of the 

nonattainment area, the MPO and DOT are 

not required to consider this to establish 

subarea budgets, unless the applicable 

implementation plan (or implementation plan 

submission) explicitly indicates an intent to 

create such subarea budgets for the purposes 

of conformity. 

(d) If a nonattainment area includes more 

than one MPO, the implementation plan may 

establish motor vehicle emissions budgets for 

each MPO, or else the MPOs must 

collectively make a conformity determination 

for the entire nonattainment area. 

§ 93.125 Enforceability of design concept 

and scope and project-level mitigation and 

control measures. 

(a) Prior to determining that a 

transportation project is in conformity, the 

MPO, other recipient of funds designated 

under title 23 U.S.C. or the Federal Transit 

Laws, FHWA, or FTA must obtain from the 

project sponsor and/or operator written 

commitments to implement in the construction 

of the project and operation of the resulting 

facility or service any project-level mitigation 

or control measures which are identified as 

conditions for NEPA process completion with 

respect to local CO, PM10, or PM2.5 impacts. 

Before a conformity determination is made, 

written commitments must also be obtained 

for project-level mitigation or control 

measures which are conditions for making 

conformity determinations for a transportation 

plan or TIP and are included in the project 

design concept and scope which is used in the 

regional emissions analysis required by 

§§93.118 (“Motor vehicle emissions budget”) 

and 93.119 (“Interim emissions in areas 

without motor vehicle emissions budgets”) or 

used in the project-level hot-spot analysis 

required by §93.116. 

(b) Project sponsors voluntarily committing 

to mitigation measures to facilitate positive 

conformity determinations must comply with 

the obligations of such commitments. 

(c) The implementation plan revision 

required in §51.390 of this chapter shall 

provide that written commitments to 

mitigation measures must be obtained prior to 

a positive conformity determination, and that 

project sponsors must comply with such 

commitments. 

(d) If the MPO or project sponsor believes 

the mitigation or control measure is no longer 

necessary for conformity, the project sponsor 

or operator may be relieved of its obligation to 

implement the mitigation or control measure if 

it can demonstrate that the applicable hot-spot 

requirements of §93.116, emission budget 

requirements of §93.118, and interim 

emissions requirements of §93.119 are 

satisfied without the mitigation or control 

measure, and so notifies the agencies involved 

in the interagency consultation process 

required under §93.105. The MPO and DOT 

must find that the transportation plan and TIP 

still satisfy the applicable requirements of 

§§93.118 and/or 93.119 and that the project 

still satisfies the requirements of §93.116, and 

therefore that the conformity determinations 

for the transportation plan, TIP, and project 

are still valid. This finding is subject to the 

applicable public consultation requirements in 

§93.105(e) for conformity determinations for 

projects. 

§ 93.126 Exempt projects. 

Notwithstanding the other requirements of this 

subpart, highway and transit projects of the 

types listed in Table 2 of this section are 

exempt from the requirement to determine 

conformity. Such projects may proceed 

toward implementation even in the absence of 

a conforming transportation plan and TIP. 

45 
§93.126 

A particular action of the type listed in Table 2 

of this section is not exempt if the MPO in 

consultation with other agencies (see 

§93.105(c)(1)(iii)), the EPA, and the FHWA 

(in the case of a highway project) or the FTA 

(in the case of a transit project) concur that it 

has potentially adverse emissions impacts for 

any reason. States and MPOs must ensure that 

exempt projects do not interfere with TCM 

implementation. Table 2 follows: 

46 
 

 

Table 2—Exempt Projects 

Safety 

Railroad/highway crossing. 

Projects that correct, improve, or eliminate a hazardous location or feature. 

Safer non-Federal-aid system roads. 

Shoulder improvements. 

Increasing sight distance. 

Highway Safety Improvement Program implementation. 

Traffic control devices and operating assistance other than signalization projects. 

Railroad/highway crossing warning devices. 

Guardrails, median barriers, crash cushions. 

Pavement resurfacing and/or rehabilitation.
 

Pavement marking. 

Emergency relief (23 U.S.C. 125). 

Fencing. 

Skid treatments. 

Safety roadside rest areas. 

Adding medians. 

Truck climbing lanes outside the urbanized area. 

Lighting improvements. 

Widening narrow pavements or reconstructing bridges (no additional travel lanes). 

Emergency truck pullovers. 

Mass Transit 

Operating assistance to transit agencies. 

Purchase of support vehicles. 

Rehabilitation of transit vehicles1

 . 

Purchase of office, shop, and operating equipment for existing facilities. 

Purchase of operating equipment for vehicles (e.g., radios, fareboxes, lifts, etc.). 

Construction or renovation of power, signal, and communications systems. 

Construction of small passenger shelters and information kiosks. 

Reconstruction or renovation of transit buildings and structures (e.g., rail or bus buildings, storage and maintenance 

facilities, stations, terminals, and ancillary structures). 

Rehabilitation or reconstruction of track structures, track, and trackbed in existing rights-of-way. 

Purchase of new buses and rail cars to replace existing vehicles or for minor expansions of the fleet1

 . 

Construction of new bus or rail storage/maintenance facilities categorically excluded in 23 CFR part 771. 

Air Quality 

Continuation of ride-sharing and van-pooling promotion activities at current levels. 

Bicycle and pedestrian facilities. 

Other 

Specific activities which do not involve or lead directly to construction, such as: 

Planning and technical studies. 

Grants for training and research programs. 

Planning activities conducted pursuant to titles 23 and 49 U.S.C. 

Federal-aid systems revisions. 

Engineering to assess social, economic, and environmental effects of the proposed action or alternatives to that action. 

Noise attenuation. 

Emergency or hardship advance land acquisitions (23 CFR 710.503). 

Acquisition of scenic easements. 

Plantings, landscaping, etc. 

Sign removal. 

Directional and informational signs. 

Transportation enhancement activities (except rehabilitation and operation of historic transportation buildings, structures, 

or facilities). 

Repair of damage caused by natural disasters, civil unrest, or terrorist acts, except projects involving substantial 

functional, locational or capacity changes. 

Note: 1

 In PM10 and PM2.5 nonattainment or maintenance areas, such projects are exempt only if they are in compliance 

with control measures in the applicable implementation plan. 

47 
§93.127 ● §93.129 

§ 93.127 Projects exempt from regional 

emissions analyses. 

Notwithstanding the other requirements of this 

subpart, highway and transit projects of the types 

listed in Table 3 of this section are exempt from 

regional emissions analysis requirements. The 

local effects of these projects with respect to CO 

concentrations must be considered to determine if 

a hot-spot analysis is required prior to making a 

project-level conformity determination. The local 

effects of projects with respect to PM10 and PM2.5 

concentrations must be considered and a hot-spot 

analysis performed prior to making a projectlevel conformity determination, if a project in 

Table 3 also meets the criteria in §93.123(b)(1). 

These projects may then proceed to the project 

development process even in the absence of a 

conforming transportation plan and TIP. A 

particular action of the type listed in Table 3 of 

this section is not exempt from regional 

emissions analysis if the MPO in consultation 

with other agencies (see §93.105(c)(1)(iii)), the 

EPA, and the FHWA (in the case of a highway 

project) or the FTA (in the case of a transit 

project) concur that it has potential regional 

impacts for any reason. Table 3 follows: 

Table 3—Projects Exempt From Regional Emissions 

Analyses 

Intersection channelization projects. 

Intersection signalization projects at individual 

intersections. 

Interchange reconfiguration projects. 

Changes in vertical and horizontal alignment. 

Truck size and weight inspection stations. 

Bus terminals and transfer points. 

§ 93.128 Traffic signal synchronization 

projects. 

Traffic signal synchronization projects may be 

approved, funded, and implemented without 

satisfying the requirements of this subpart. 

However, all subsequent regional emissions 

analyses required by §§93.118 and 93.119 for 

transportation plans, TIPs, or projects not from a 

conforming plan and TIP must include such 

regionally significant traffic signal 

synchronization projects. 

§ 93.129 Special exemptions from 

conformity requirements for pilot program 

areas. 

EPA and DOT may exempt no more than six 

areas for no more than three years from 

certain requirements of this subpart if these 

areas are selected to participate in a 

conformity pilot program and have developed 

alternative requirements that have been 

approved by EPA as an implementation plan 

revision in accordance with §51.390 of this 

chapter. For the duration of the pilot program, 

areas selected to participate in the pilot 

program must comply with the conformity 

requirements of the pilot area's 

implementation plan revision for §51.390 of 

this chapter and all other requirements in 40 

CFR parts 51 and 93 that are not covered by 

the pilot area's implementation plan revision 

for §51.390 of this chapter. The alternative 

conformity requirements in conjunction with 

any applicable state and/or federal conformity 

requirements must be proposed to fulfill all of 

the requirements of and achieve results 

equivalent to or better than section 176(c) of 

the Clean Air Act. After the three-year 

duration of the pilot program has expired, 

areas will again be subject to all of the 

requirements of this subpart and 40 CFR part 

51, subpart T, and/or to the requirements of 

any implementation plan revision that was 

previously approved by EPA in accordance 

with §51.390 of this chapter. 

48