Transportation Conformity Reference Guide

Section C: General Requirements
Chapter 5 Regional Emissions Analysis

Regional Emissions Analysis Requirement
What Should Be Included in the Regional Emissions Analysis?

• Regionally Significant Projects
• Non-regionally Significant Projects
• Federal Projects
• Non-Federal Projects
• Projects in the Transportation Plan/TIP
• Traffic Signal Synchronization Projects

When Can Emissions Credits Be Included in the Emissions Analysis?
What Emissions Credits May Not be Included in the Regional Emissions Analysis?
What Projects are Exempt from Regional Emissions Analysis?

• Projects Exempt from Regional Emissions Analysis
• Exempt Projects

What are the Requirements of Regional Emissions Analysis - Applicable for All Nonattainment and Maintenance Areas at All Times?

• Latest Planning Assumptions
• Latest Emissions Model
  • What if it is determined that the new model will result in significantly higher emissions projections?
  • Grace Period
• Consistency With SIP Assumptions

Conditions Under Which New Regional Emissions Analysis Is Not Required

• Reliance on Previous Regional Analysis for Conformity Determinations
• Areas with Limited Maintenance Plans
• Areas with Insignificant Motor Vehicle Emissions

Which Pollutants are Subject to Regional Emissions Analysis Requirements?
Questions and Answers

Exhibit 5-1: Determining Which Activities Are Eligible for Emissions Reduction Credits
Exhibit 5-2: Latest Planning Assumptions

This Chapter discusses the regional emissions analysis requirements, which are applicable for all nonattainment and maintenance areas in making a conformity determination. The focus will be on the general requirements for determining regional transportation-related emissions, including the type of projects to be included, projects that are exempted, and the treatment of emissions credits.

Very often, when "regional emissions analysis" is mentioned, planners equate it with the transportation and emissions modeling processes - the mechanics of running the models. Although modeling processes form the core of the regional emissions analysis, a number of general and specific requirements of regional emissions analysis are essential to the conformity process. The specific regional analysis requirements applicable to nonattainment and maintenance areas are specified in 40 CFR §§93.118 and 93.119 and are discussed in detail in Section D.

Regional Emissions Analysis Requirement

The regional emissions analysis forms the basis of the conformity determination and is performed to demonstrate the consistency of transportation plans and TIPs with the SIP motor vehicle emissions budgets.

CAA §176(c)(2)(A), 42 U.S.C. §7506(c)(2)

... emissions expected from implementation of plans and programs are consistent with estimates of emissions from motor vehicles and necessary emissions reductions contained in the applicable implementation plan.

Other regional emissions analysis requirements that apply specifically to certain nonattainment areas will be discussed in detail in Section D. These requirements include network based model requirements for serious and above ozone and CO nonattainment areas with urbanized area populations over 200,000, and the use of local VMT forecasts based on Highway Performance Monitoring System (HPMS) or local counts including all travel in a region (Chapter 6).

What Should Be Included in the Regional Emissions Analysis?

40 CFR §93.122(a)(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.

Regional emissions analysis should reflect emissions of all travel, including:

1. All federal projects;
2. All regionally-significant projects, regardless of funding source, are required to be included in the model; and
3. VMT from all other projects (including TCMs) that are not required to be explicitly modeled must be estimated based upon reasonable professional practice.

In addition, the regional emissions analysis must estimate total projected emissions for certain future years (including milestone and attainment years as identified in the SIP and discussed in Chapter 1), and may include the effects of any emissions control programs which are already adopted by the enforcing jurisdiction (such as vehicle inspection and maintenance programs and reformulated gasoline and diesel fuel).

Regionally Significant Projects

40 CFR §93.101, Definitions

Regionally significant project means 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.

It should be noted that determining which minor arterials and/or other projects should be considered "regionally significant" for the purpose of regional analysis for each nonattainment area is determined through the interagency consultation process (40 CFR §93.105(c)(1)(ii); see also Chapter 2). Under this process, it is possible that regional significance could vary from State to State or area to area. For example, one specific nonattainment area identifies a regionally significant project as a minor arterial or higher classification. In addition, once a project is identified as regionally significant, it must be included in the analysis regardless of funding source.

Non-regionally Significant Projects

For those projects which are not regionally significant, but which will affect vehicle travel, emissions may be estimated in accordance with reasonable professional practice, even if the nonattainment areas are required to perform transportation network demand modeling (see Chapter 6). For example, the regional emissions analysis may assume that VMT on local streets not represented in the network model is a certain percentage of network VMT, without explicitly considering the new local streets. (58 FR 62189, 62111, Nov. 24, 1993.)

Federal Projects

The transportation conformity rule defines FHWA/FTA projects as follows:

40 CFR §93.101, Definitions

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 Federal-Aid 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.

Non-Federal Projects

62 FR 43788, August 15, 1997

Non-Federal projects are projects which are funded or approved by a recipient of Federal funds designated under title 23 U.S.C. or the Federal Transit Laws (49 U.S.C. Chapter 53), but which do not require any FHWA/FTA funding or approvals.

A recipient of funds is defined as follows:

40 CFR §93.101, Definitions

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 the 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.

Projects In The Transportation Plan/TIP

The conformity rule requires that emissions from all Federal (FHWA/FTA) and non-Federal projects in the plan/TIP, including regionally significant traffic signal synchronization projects be included in the regional analysis. Projects that are not regionally significant must also be included. In other words, the regional analysis must account for all travel.

Traffic Signal Synchronization Projects

Specific regional emissions analysis requirements are applicable to exempt projects and traffic synchronization projects in determining conformity.

On September 24, 1996, Congress amended the CAA (H.R. 2988) to state that traffic signal synchronization projects are exempt from conformity determinations prior to their funding, approval, or implementation. However, once these projects are funded, approved, or implemented (whichever occurs first), they are to be included in the conformity determinations for future transportation plans, TIPs, and projects. The conformity rule reflects this CAA amendment in §93.128, "Traffic signal synchronization projects," and, as shown below, this section states that traffic signal synchronization projects may be approved, funded, and implemented without a conformity determination.

40 CFR §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 analysis 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.

When Can Emissions Credits Be Included in the Emissions Analysis?

40 CFR §93.122(a)(3) and (4)

1. General Requirements
   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:
      1. The regulatory action is already adopted by the enforcing jurisdiction;
      2. The project, program, or activity is included in the applicable implementation plan;
      3. The control strategy implementation plan submissions or maintenance plan submissions 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
      4. 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.
      1. Persons or entities voluntarily committing to control measures must comply with the obligations of such commitments.
      2. The conformity implementation plan revisions 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.

Exhibit 5-1 summarizes the conditions for including emissions reduction credits in the regional emissions analysis.

Exhibit 5-1
Determining Which Activities Are Eligible for Emissions Reduction Credits

	If:	Then:
TCM/other measures in the approved SIP	Their implementation has been assured or, The measure has been partially implemented and it can be demonstrated that it is providing quantifiable emissions reduction benefits for the part of the measure that has been implemented	Include in emissions analysis
	Delayed beyond the scheduled implementation date(s) in the approved SIP	Do not include in emissions analysis
Projects, programs, or activities which require a regulatory action in order to be implemented	One of the following is met: The regulatory action is already adopted by the enforcing jurisdiction The project, program, or activity is included in the applicable implementation plan 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 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	Include in emissions analysis
	None of the above conditions met	Do not include in emissions analysis
Control measures that are not included in the transportation plan/TIP, and which do not require a regulatory action in order to be implemented	The conformity determination includes written commitments[1] (obtained prior to the conformity determination) to implementation from the appropriate entities who voluntarily commit to control measures; these entities must comply with the obligations of such commitments	Include in emissions analysis
	The conformity determination does not include written commitments	Do not include in emissions analysis

What Emissions Credits may not be Included in the Regional Emissions Analysis?

40 CFR §93.122(a)(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 dates(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 emission reduction credit.

If a control measure in an approved SIP is delayed or changed in whole or in part (e.g., the legislative authority of a program has changed), then conformity determinations must reflect such a delay or change. The conformity analysis may only include the actual implementation of the control measure.

What Projects are Exempt from Regional Emissions Analysis?

Projects Exempt from Regional Emissions Analysis

As stated in the conformity rule, projects as defined in §93.127 and listed in Table 3 are exempted from regional analysis. However, they may still be subject to project level hot-spot analysis. Also, should the MPO, through the interagency consultation process, concur that these projects may have potentially adverse emissions impacts; the regional emissions analysis may then be required.

40 CFR §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 are exempt from regional emissions analysis requirements. The local effects of these projects with respect to CO or PM10 concentrations must be considered to determine if a hot-spot analysis is required prior to making a project level conformity determination. 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 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 - Projects Exempt from Regional Emissions Analysis

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

Exempt Projects

In addition, projects defined as exempt projects in §93.126 and listed in Table 2 of the transportation conformity rule are exempt from the requirement to determine conformity (not required for regional and project level analysis). Nevertheless, the emissions reductions from these projects can be included in the conformity analysis. (See also Appendix G Analyzing Exempt Projects in the Conformity Process, February 3, 1995.)

40 CFR §93.126, Exempt projects.

Notwithstanding the other requirements of this subpart, highway and transit projects of the types listed in Table 2 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. A particular action of the type listed in Table 2 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. - Exempt Projects

SAFETY
Railroad/highway crossing.
Hazard elimination program.
Safer non-Federal aid system roads.
Shoulder improvements.
Increasing sight distance.
Safety improvement program.
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 demonstration.
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 vehicles^*.
Purchase of office, shop, and operating equipment for existing facilities.
Purchase of operating equipment for vehicles (e.g., radios, fare boxes, 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 track bed in existing rights-of-way.
Purchase of new buses and rail cars to replace existing vehicles or for minor expansions of the fleet^*.
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: In PM-10 -nonattainment or maintenance areas, such projects are exempt only if they are in compliance with control measures in the applicable implementation plan.)

In general, exempt projects include all projects which have no emissions impact, and are considered to be neutral or de minimis. For projects such as travel demand management strategies for which air quality effects cannot be accurately assessed in a traditional regional modeling context, other accepted methods (reasonable professional practice) of quantifying their effects are encouraged (40 CFR §93.122(a)).

What are the Requirements of Regional Emissions Analysis - Applicable for All Nonattainment and Maintenance Areas at All Times?

In addition to the requirements mentioned above, other requirements that are applicable for all nonattainment and maintenance areas are discussed below.

Latest Planning Assumptions

All conformity determinations must be based upon the latest planning assumptions in force at the time the conformity analysis begins. According to 69 FR 40053, July 1,2004, this is the point at which the MPO or other designated agency begins to model the impact of the proposed transportation plan, TIP, or project on VMT and speeds and/or emissions for a conformity determination. The assumptions are summarized in Exhibit 5-2 and are discussed at length in joint guidance issued by FHWA/FTA/EPA on January 18, 2001 (See Appendix L). In short, areas are encouraged to review and update their planning assumptions regularly and are strongly encouraged to review and strive toward regular 5-year updates of planning assumptions, especially population, employment, and vehicle registration assumptions. Conformity determinations that are based on assumptions that are older than 5 years should include written justification for not using more recent information.

It should be expected that planning assumptions used in conformity determinations will deviate over time from the SIP's assumptions regarding VMT growth, demographics, trip generation, etc. This is because plans and TIPs must be updated on a periodic basis while no such frequency requirement exists for SIPs. Both SIPs and transportation plans and TIPs must use the latest planning assumptions at the time they are developed.

Exhibit 5-2
Latest Planning Assumptions
(40 CFR §93.110(b)-(f))

For	Assumptions
General Planning Elements	Must be derived from estimates of current and future population, employment, travel, and congestion most recently developed by the MPO or other agency authorized to make such estimates and approved by the MPO
Background Concentrations	Must be based on latest assumptions about current and future background concentrations
Transit	Must discuss in each transportation plan/TIP transit operating policies (including fares and service levels) and transit ridership assumptions that have changed since the previous conformity determination Must include reasonable assumptions about transit service and increases in transit fares and road and bridge tolls over time
TCMs and Other Measures in SIPs	Must use the latest existing information regarding effectiveness of SIP measures that have already been implemented
Interagency and Public Consultation Requirements	All key assumptions must be specified and included in draft conformity documents and supporting materials

Latest Emissions Model

All conformity determinations must be based on the latest motor vehicle emissions factor model available and approved by EPA for use:

40 CFR §93.111(a)

The conformity determination must be based on the latest emissions 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.

This criterion is satisfied if the most current version of the motor vehicle emissions factor model(s) specified by EPA is used for the regional emissions analysis.

As of the time this document was revised in 2005, EPA specified that MOBILE6.2 (see Appendix D) is the latest approved emissions factor model for use outside of California, and EMFAC2002 (see Appendix E) is the latest approved emissions factor model for use in California[2].

On May 19, 2004, EPA approved MOBILE6.2 as the official model for estimating emissions of particulate matter (PM) from highway vehicles. MOBILE6.2 updated the previous version, MOBILE6, with the capability to estimate exhaust and brake and tire wear particulate matter emission factors for PM10 and PM2.5 and exhaust emission factors for particulate matter precursors. MOBILE6.2 should also be used to estimate carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx) for official EPA purposes. MOBILE6.2 capabilities include the estimation of both direct particulate matter (PM) emissions and the emissions of certain particulate precursors. One significant difference between MOBILE6.2 and its predecessor for PM emissions, PART5, is that MOBILE6.2 does not include the capability of estimating the emissions of re-entrained road dust as the result of motor vehicle activity. On May 19, 2004, EPA also finalized new methods for the estimation of re-entrained road dust emissions from cars, trucks, buses, and motorcycles on paved and unpaved roads which are incorporated in the December 2003 edition of Chapter 13 of Compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area Sources, available at: www.epa.gov/ttn/chief/ap42/ch13/index.html.

In particular, all States other than California should use MOBILE6.2 and AP-42 for ozone, CO, and PM2.5 conformity analyses. EPA established a 2-year grace period before MOBILE6.2 and AP-42 are required for new PM10 conformity determinations in most cases. The grace period began on May 19, 2004, the effective date of EPA's Federal Register notice making MOBILE6.2 and AP-42 the official methods for calculating PM-10 emissions. During this grace period, areas should use the interagency consultation process to examine how MOBILE6.2 and AP-42 will impact their future conformity determinations.

What if it is determined that the new model will result in significantly higher emissions projections?

An area may want to consider recalculating its SIP inventories and budgets using the new model, and submitting them to EPA for approval. Additional control measures may need to be added as necessary. It is noted, however, that past experience indicates considerable time (e.g., years) can be required to obtain EPA approval of new SIP assumptions and emissions projections. Notwithstanding this possibility, areas that have projected emissions near the level of their SIP budgets should carefully consider the effect of any new emissions model on future regional emissions analysis and conformity determinations.

Grace Period

The conformity rule establishes a grace period for the transition to the latest emissions model:

40 CFR §93.111

2. 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; and
3. Transportation plan and TIP conformity analysis for which the emissions analysis was begun during the grace period or before the Federal Register notice of availability of the latest emissions 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.

Once the grace period expires, the new emissions model must be used for new conformity analyses. It is, therefore, essential that, during the grace period, areas determine whether use of the new model will result in problems demonstrating conformity with the existing SIP budgets (i.e., will the new model produce significantly higher emissions under the travel projections contained in the SIP).

Consistency With SIP Assumptions

The SIP contains procedures to monitor, control, maintain, and enforce compliance with the National Ambient Air Quality Standards (NAAQS). The conformity rule requires that ambient temperatures be consistent with those used in the SIP, and allows other factors assumed in the SIP, such as the fraction of travel in a hot stabilized-engine mode, to be modified in a conformity determination after interagency consultation and only under certain conditions (40 CFR §93.122(a)(6)). (See Section B for a discussion of the relationship between SIPs and transportation conformity.)

As defined in the transportation conformity rule, the following assumptions used in the regional emissions analysis shall be consistent with those used to established the emissions budgets in the SIP:

40 CFR §93.122(a)(6)

The ambient temperatures used for the regional emissions analysis shall be consistent 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.

The latest planning assumptions must be used in conformity determinations, even if they differ from those used in the SIP (40 CFR §93.110(b)-(f)). In many cases, the MPO may have developed more recent assumptions for the conformity process than those included in a submitted or approved SIP. For example, the MPO may have adopted new population, employment, and/or socioeconomic projections or updated transportation models since the SIP was submitted. In this case, an MPO would use the latest planning assumptions based on the newer projections and model improvements for conformity. The consultation process should be used to ensure that air quality and transportation planning processes anticipate such changes in planning assumptions.

See the questions and answers section at the back of this chapter for further information on assumptions in a submitted or approved SIP.

Conditions Under Which New Regional Emissions Analysis Is Not Required

Reliance on Previous Regional Analysis for Conformity Determinations

The conformity rule allows for the reliance on the previous regional emissions analysis for conformity determinations on TIPs that are consistent with the transportation plan. However, a formal conformity determination is still required. Section 93.122 (g) specifies the requirements for reliance on the previous analysis, but its applicability must be documented. Documentation of the timely implementation of TCMs, and an affirmative conformity determination must then be made by the MPO and FHWA/FTA per 93.104(c). Also, it should be noted that reliance on previous regional emissions analysis for a conformity determination does not satisfy the frequency requirements of 40 CFR §93.104(b) or (c).

40 CFR §93.122(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:
   1. The new plan/TIP contains 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;
   2. 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 regional emissions at the time of the transportation plan's conformity determination;
   3. The design concept and scope of each regionally significant project in the new plan and TIP are not significantly different from that described in the transportation plan; and
   4. The previous regional emissions analysis is consistent with the requirements of §§93.118 (including 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 demonstrates) and/or §93.119, as applicable, and if the project is either:
   1. not regionally significant; or
   2. 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.

In the preamble to the November 24, 1993 conformity rule, EPA discussed the issue of TIP amendments and when regional emissions analysis on the TIP is required.

58 FR 62202, November 24, 1993

...Therefore, EPA believes that conformity determinations on minor TIP amendments do not necessarily require new regional emissions analysis, although a positive conformity finding must be made and the regional emissions criteria must be satisfied by documenting the appropriateness of relying on the previous analysis.

The July 1, 2004 conformity rule revised 93.122(g) to allow minor plan revisions to rely on a previous emissions analysis. To meet §93.122(g) requirements, minor revisions to the transportation plan may include no additions or deletions of regionally significant projects, no significant changes in the design concept and scope of existing regionally significant projects, and no changes to the time frame of the transportation plan. Further, minor plan revisions under §93.122(g) would not include revisions that delay or accelerate the completion of regionally significant projects across conformity analysis years (69 FR 40058, July 1, 2004).

Areas with Limited Maintenance Plans

40 CFR §93.101, Definitions.

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.

There are some maintenance areas for which no emissions budget is required, based on guidance memoranda issued by EPA[3]. These are called limited maintenance areas and include the following categories of maintenance areas:

• Nonclassifiable CO areas whose design values are at or below 7.65 ppm (85% of the exceedance levels of the CO NAAQS); and
• Moderate PM10 areas whose design values are at or below 40 µg/m3 for the annual and 98 µg/m3 for the 24-hr PM10 NAAQS with no violations at any monitor in the nonattainment area

EPA has also begun allowing additional areas to submit second 10-year maintenance plans under the limited maintenance policy. Each of the above areas is allowed to submit a limited maintenance plan that does not establish emissions budgets for the area. According to the EPA guidance memoranda, when EPA approves a limited maintenance plan, it:

".... is concluding that an emissions budget may be treated as essentially not constraining for the length of the maintenance period because it is unreasonable to expect that such an area will experience so much growth in that period that a violation of the NAAQS would result."

The guidance memoranda conclude that the emissions budget test is satisfied in areas with approved limited maintenance plans.

There are also other areas (e.g. a CO or PM10 area dominated by stationary sources) for which it can be demonstrated that vehicle emissions are not a significant contributor to the area's air quality problem or that they only have a hot spot problem. If such a demonstration is made, the SIP and/or maintenance plan is allowed to explicitly state that no emissions budget is being established for conformity purposes, and therefore the emissions budget test is satisfied.

40 CFR §93.109(j), 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 and PM10 areas.

EPA considers it a reasonable assumption that motor vehicle emissions in an area that qualifies for a limited maintenance plan could increase to any realistic level during the maintenance period without causing or contributing to a violation of the standard. As a result, the budgets in limited maintenance plans are treated as essentially not constraining for the length of the maintenance period, and EPA believes that the Clean Air Act requirements to not worsen air quality are met presumptively without a regional emissions analysis. While this policy does not exempt an area from the need to determine conformity, it does eliminate the need for the regional emissions analysis since EPA would be concluding through our adequacy review or approval of the limited maintenance plan that limits on motor vehicle emissions during the maintenance period are unnecessary, as long as the area maintains the standard (69 FR 40063, July 1, 2004). A conformity determination that meets other applicable criteria, including the hot spot requirements in CO, PM2.5 and PM10 nonattainment and maintenance areas, interagency and public consultation, and timely implementation of TCMs in an approved SIP area still required in these areas.

Areas with Insignificant Motor Vehicle Emissions

40 CFR §93.109(k), 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 emission 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 and PM10 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.

EPA developed the insignificance policy to provide flexibility for areas where motor vehicle emissions had little to no impact on an area's air quality problem. EPA believes that requiring these areas to perform a regional emissions analysis is not necessary to meet Clean Air Act section 176(c) requirements that transportation actions not worsen air quality, since the overall contribution of motor vehicle emissions in these areas is small and thus any significant change in such emissions over time would be unlikely (69 FR 40062, July 1, 2004).

Which Pollutants are Subject to Regional Emissions Analysis Requirements?

The pollutants subject to regional emissions analysis requirement can be found at 40 CFR §93.119(f).

Pollutants for Which a Regional Emissions Analysis Is Required*

Area Designation	Pollutant Precursor
Ozone Areas	VOC, NOx
CO Areas	CO
PM10 Areas	PM10, VOC, NOx
PM2.5 Areas	PM2.5, NOx, VOC, SOx, Ammonia
NO2 Areas	NOx

* Areas may be nonattainment or maintenance areas for more than one pollutant (e.g. nonattainment for ozone, CO and PM10).

For ozone areas, NOx is required for the emission reduction tests if no adequate budgets exist, unless the EPA administrator determines that additional reductions of NOx would not contribute to attainment. See 40 CFR §93.119(f)(2). A NOx waiver from the build-no-greater-than-no-build test does not eliminate the requirement for the budget test if a NOx budget is established which EPA has deemed adequate. In addition, a NOx waiver under the 1-hour ozone standard is not applicable under the 8-hour zone standard.

Regional analysis of transportation related precursors of PM10 (VOCs and NOx) is required if the EPA regional administrator or the director of the State air quality agency has made a finding that such precursor emissions from within the area are a significant contributor to the PM10 nonattainment area and has so notified the MPO and DOT. See 40 CFR §93.119(f)(5).

In PM2.5 areas, NOx is required, 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 have so notified the MPO and DOT. See 40 CFR §93.119(f)(9). The precursors VOC, SOx, and/or ammonia (NH3) are required if the EPA regional administrator or the director of the State air quality agency has made a finding that 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. See 40 CFR §93.119(f)(10).

In PM10 nonattainment and maintenance areas, reentrained road dust from paved and unpaved roads should be included in the regional emissions analysis. For PM2.5, if the EPA regional administrator or director of the State air quality agency makes a finding that emissions from reentrained road dust within the area are a significant contributor to the PM2.5 problem and has notified the MPO and DOT, only then should regional emissions analyses include reentrained road dust see 40 CFR §93.119(f)(8). In PM10 and PM2.5 nonattainment and maintenance areas, construction-related fugitive dust associated with highway and transit project construction is only required to be included in the regional emissions analysis if the SIP identifies it as a contributor to the nonattainment problem.

Questions and Answers

Can non-exempt, regionally significant projects be added to the plan/TIP without regional analysis?

No. Every plan/TIP amendment that involves regionally significant, non-exempt projects[4] requires the same level of regional emissions analysis. The reasons for this decision can be summarized as follows:

62 FR 43795, August 15, 1997

EPA believes that the restrictions that would have to be imposed on the flexibility would outweigh its benefits. EPA has determined that the flexibility to add projects without a regional emissions analysis would have to be accompanied by safeguards or limitations such as adding minimum criteria for alternate analysis methodology in the rule; limiting the flexibility to types and numbers of projects; or requiring that the emissions from the existing plan/TIP be below a minimum threshold of the applicable emissions budget. Including such safeguards could result in additional rule complexity that would hamper use of the proposed flexibility.

The few methodologies proposed were not sufficient to form the basis of nationally applicable, minimum guidelines for alternate emissions analysis. When EPA proposed the flexibility, it was seeking a procedure that would yield similar results as a full-scale regional analysis but with less effort. However, the methodologies suggested were sketch planning techniques, which are ancillary to but not substitutes for network modeling.

EPA and DOT believe that regulatory constraints on the proposed flexibility would defeat the flexibility's purpose. Many commenters did not believe EPA could or should develop alternate analysis techniques that would apply nationally, because the value of the flexibility would be its application on a case-by-case basis. In addition, many stakeholders want the regulatory text to be streamlined and procedural modeling guidelines to be minimized. EPA and DOT also believe that the possible benefits of the proposed flexibility do not warrant the complication of a new set of modeling guidelines; and.

EPA and DOT believe the time and effort spent in developing an alternate procedure and getting agreement from all involved agencies seems greater than that involved in running the regional model. Many commenters stated that the flexibility would be used infrequently, or only in limited circumstances; thus would not have a large impact on day-to-day implementation of the conformity rule. Some commenters believe that a full-scale regional analysis is just as easy as using an alternate sketch planning method....

Who is responsible for the regional analysis for the portion of the nonattainment area that lies outside the boundary of the metropolitan area?

The regional emissions analysis that MPOs base their transportation plan and TIP conformity determinations on must include the entire nonattainment or maintenance area (unless there are adequate/approved subarea budgets) (See 40 CFR §93.122(a)(1) and (7)). This can be accomplished in different ways. The conformity rule requires that interagency consultation procedures include specific procedures for where the metropolitan planning area does not include the entire nonattainment or maintenance area, including a process involving the MPO and the State DOT for cooperative planning and analysis for purposes of determining conformity of all projects outside the metropolitan area, but within the nonattainment or maintenance area. (See 40 CFR §93.105(c)(3))

In some existing nonattainment/maintenance areas with these "donut" areas, the MPO takes the lead in conducting the regional emissions analysis for the donut area. However, in many other nonattainment and maintenance areas with donut areas, the State DOT takes the lead for regional emissions analysis for the area that falls outside of the MPO planning area but within the nonattainment or maintenance area. This question is answered in more detail in Chapter 12.

Do conformity determinations need to include an assessment for how current planning assumptions deviate from the SIP's assumptions?

EPA does not require an assessment of the degree to which key assumptions in the transportation modeling process are deviating from those used in the SIP, and if the deviations are significant or require an evaluation of the impact of the deviation on the area's ability to reach the SIP's emissions target. This process is not required because the conformity determinations themselves are intended to demonstrate that given the most recent planning assumptions and emissions models, the SIP's emissions reductions will be met. States may voluntarily require such a process in their conformity SIP revisions.

(From FHWA/FTA/EPA January 18, 2001 Memorandum on Use of Latest Planning Assumptions in Conformity Determinations, Appendix L)

What if the assumptions used in a submitted or approved SIP are not the most current and best information for conformity determinations?

The latest planning assumptions must be used in conformity determinations, even if they differ from those used in the SIP. In many cases, the MPO may have developed more recent assumptions for the conformity process than those included in a submitted or approved SIP. For example, the MPO may have adopted new population, employment, and/or socioeconomic projections or updated transportation models since the SIP was submitted. In this case, an MPO would use the latest planning assumptions based on the newer projections and model improvements for conformity. The consultation process should be used to ensure that air quality and transportation planning processes anticipate such changes in planning assumptions.

It is expected that planning assumptions in the conformity process will change over time from those used in the SIP. Conformity determinations must reflect updated planning assumptions, even if those assumptions are different from those used in the SIP's development. EPA articulated this in the preamble to the November 24, 1993, conformity rule:

58 FR 62210, November 24, 1993

It should be expected that conformity determinations will deviate from the SIP's assumptions regarding VMT growth, demographics, trip generation, etc., because the conformity determinations are required by CAA section 176(c)(1) to use the most recent planning assumptions.

How can an area take emissions credit for land use activities that improve air quality?

In January 2001 the EPA announced the availability of "Improving Air Quality Through Land Use Activities" (EPA 420-R-01-001). This guidance describes options of how areas can account for air quality benefits of their local land use strategies through the SIP and/or conformity processes. In general, states can account for air quality benefits of land use activities in one of three ways: 1) include land use activities in the initial forecast of future emissions in the SIP, 2) include land use activities as control strategies in the SIP, or, 3) include land use activities in a conformity determination, without including them in the SIP. This guidance is non-regulatory and is available on EPA's website at: www.epa.gov/otaq/stateresources/transconf/policy.htm#landuse.

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[1] Written commitment as defined in the conformity rule 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 (40 CFR §93.101, Definitions).
[2] More information regarding the use of the MOBILE6.2 and EMFAC2002 models are available at www.epa.gov/otaq/mobile.htm and www.arb.ca.gov/planning/sip/emfac2002/emfac2002.htm, respectively.
[3] Limited Maintenance Plan Option for Nonclassifiable Ozone Nonattainment Areas, Memorandum from Sally L. Shaver, Director, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Air Quality Strategies and Standards Division, Nov. 16, 1994. Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas, Memorandum from Joseph W. Paisie, Group Leader, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Integrated Policy and Strategies Group, Oct. 6, 1995. See Appendix J. Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas, Memorandum from Lydia Wegman, Director, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Air Quality Strategies and Standards Division, August 21, 2001. See Appendix I.
[4] A non-exempt project is any transportation project other than those listed in 40 CFR §93.126, "Exempt projects," and 40 CFR §93.127 "Projects exempt from regional emissions analysis."