Office of Planning, Environment, & Realty (HEP)
Planning • Environment • Real Estate
Regional Emissions Analysis and Conformity Tests
Motor Vehicle Emissions Budget Test
Questions and Answers - Maintenance Plan Budgets
Questions and Answers - Once SIP Budgets Are Adequate/Approved
What Conformity Test Should Be Used before EPA has found the Submitted Budget Adequate?
Questions and Answers - Before SIP Budgets Are Adequate or Approved
Agency Roles
TCM Analysis
Off-model Analysis
Exhibit D-1: Conformity Elements
Exhibit D-2: Applicability of Conformity Tests By Type of Action
Exhibit D-3: Conformity Requirements By Action, Pollutant, & Classification
Exhibit D-4: Relationship Between SIP Budget Status & Conformity Tests
Exhibit D-5: Nonattainment Areas & Conformity Tests
Exhibit D-6: What Regional Emissions Tests Apply?
Exhibit D-7: Regional Emissions Tests for Maintenance Areas
Exhibit D-8: Example of Projects & Activities Included in the Regional Emissions Analysis
Exhibit D-9: Typical Agency Roles in Integrating Transportation & Air Quality Modeling
The specific criteria and requirements are discussed in the following Chapters:
The conformity rule requires transportation plans/TIPs to demonstrate consistency with the SIP's motor vehicle emissions budget by performing a regional emissions analysis. A regional analysis must estimate the emissions that would result from the implementation of the transportation plan/TIP, and compare these emissions to the motor vehicle emissions budget identified in the SIP (see Section B). If the emissions associated with the transportation plan/TIP are greater than the motor vehicle emissions budget, the transportation plan/TIP do not conform. This may occur even though all TCMs in the SIP are being properly implemented; for example, motor vehicle emissions may exceed the SIP budget if population and VMT growth are higher than predicted when the SIP was developed (58 FR 62195, November 24, 1993).
Perhaps the best summary for the conformity criteria applicable to transportation plans, TIPs and projects is Table 1 of the Conformity Rule:
40 CFR §93.109 (b)
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 §93.119 Emissions budget and/or Interim Emissions
TIP
§93.113(c) TCMs
§93.118 and/or §93.119 Emissions budget and/or Interim 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 and PM10 hot spots
§93.117 PM-10 and PM-2.5 control measures
PROJECT (NOT FROM A CONFORMING Plan and TIP)
§93.113(d) TCMs
§93.114 Currently conforming plan and TIP
§93.116 CO and PM-10 hot spots
§93.117 PM-10 and PM-2.5 control measures
§93.118 and/or §93.119 Emissions budget and/or Interim emissions
Specific conformity tests are required per nonattainment classification, and specific requirements are also applied to plans, TIPs and projects as well. Exhibit D-1 summarizes the conformity elements for plans, TIPs, and projects. The types of conformity tests that are used and the actions that apply to different nonattainment areas are shown in Exhibit D-2 and Exhibit D-3. In general, the conformity requirements for maintenance areas are identical to those for nonattainment areas.
| Conformity Elements | |
|---|---|
| Regional Emissions Analysis Requirements for Plans/TIPs |
|
| Project-level Requirements |
|
| Other Requirements (Applies to Plans, TIPs and Projects) |
|
| Projects not from a Plan/TIP |
|
*EPA issued PM2.5 and revised PM10 hot spot analyses requirements in March 2006. This Guide has not been updated to reflect those changes.
Note: The specific tests depend upon the pollutant, nonattainment classification, and the status of the control strategy SIP or maintenance plan.
* Meets the requirements of 40 CFR 93.115.
** Does not meet the requirements of 40 CFR 93.115.
| Ozone [2] | Carbon Monoxide | PM2.5 [3] | PM10 | NO2 | |||
|---|---|---|---|---|---|---|---|
| Moderate and Above | Marginal and Below | Moderate >12.7 ppm | Moderate <12.7 ppm | All | All | All | |
| Plan and TIP | 8-Hr: Build-less-than-no-build Test AND Less-than-2002 Test or Budget Test TCM Test* |
8-Hr: Build-no-greater-than-no-build or No-greater-than-2002 Test or Budget Test TCM Test |
Build-less-than-no-build AND Less-than-1990 Test or Budget Test TCM Test |
Build-no-greater-than-no-build Test or No-greater-than-1990 Test or Budget Test TCM Test |
Build-no-greater-than-no-build or No-greater-than-2002 TCM Test |
Build-no-greater-than-no-build Test or No-greater than-1990 Test or Budget Test TCM Test |
Build-no-greater-than-no-build or No-greater-than-1990 Test or Budget Test TCM Test |
| Project** (From Plan and TIP as Defined in 40 CFR 93.115) | No Additional Requirements | No Additional Requirements | Hot-Spot Analysis | Hot-Spot Analysis | Hot-spot Analysis (for certain projects) Consistency with SIP PM2.5 Control Measures |
Hot-spot Analysis (for certain projects) Consistency with SIP PM10 Control Measures |
No Additional Requirements |
| Project** (Not From Conforming Plan and TIP as Defined in 40 CFR 93.115) | 8-Hr: Build-less-than-no-build Test AND Less-than-2002 Test or Budget Test TCM Test |
8-Hr: Build-no-greater-than-no-Build or No-greater- than-2002 Test or Budget Test TCM Test |
Hot-Spot Analysis Build-less-than-no-build AND Less-than-1990 Test or Budget Test TCM Test |
Hot-Spot Analysis Build-no-greater-than-no-build Test or No-greater-than-1990 Test or Budget Test TCM Test |
Hot-spot Analysis (for certain projects) Consistency with SIP PM2.5 Control Measures Build-no-greater-than-no Build or No-greater-than- 2002 Test or Budget Test TCM Test |
Hot-spot Analysis (for certain projects)Consistency with SIP PM10 Control Measures Hot-Spot Test Build-no-greater-than-no-build or No-greater-than-1990 Test or Budget Test TCM Test |
Build-no-greater-than-no-build or No-greater-than-1990 Test or Budget Test TCM Test |
Flexibilities for isolated rural nonattainment areas and clean data areas are not reflected.
* TCM Test is for timely implementation of TCMs included in SIPs (see Chapter 3).
** All pollutants and classifications: there must be a conforming plan and TIP at the time of project approval. Please see Chapter 4 for discussion of conformity lapse.
In the conformity rule, the budget test is described as the following:
40 CFR §93.118, Criteria and procedures: Motor vehicle emissions budget.
In summary, the budget test must demonstrate consistency with the motor vehicle emissions budget from the applicable SIP and show that emissions within the time frame of the transportation plan/TIP are less-than or equal-to the SIP motor vehicle emissions budget(s). This consistency must be demonstrated for each year for which the applicable SIP establishes a budget (if in the time frame of the plan/TIP), the attainment year (if it is within the timeframe of the plan/TIP), the last year of the transportation plan's forecast period (unless the MPO, after consultation with the air pollution control agency and solicitation of public comment and consideration of such comments elects to shorten the horizon for conformity, per SAFETEA-LU section 6011(c)) and for any intermediate years as necessary so that the years for which consistency is demonstrated are no more than ten years apart. The following are major provisions of the motor vehicle emissions budget test.
The emissions budget test criteria is satisfied when emissions of the pollutants or pollutant precursors are less-than or equal-to the motor vehicle emissions budgets established in the SIP. Transportation plans, TIPs, and projects not from a conforming transportation plan and TIP must be consistent with the motor vehicle emissions budget(s) in the applicable SIP. For additional information on motor vehicle emissions budgets see Section B.
EPA believes that, at a minimum, rounding conventions used in conformity should be consistent with the level of precision used for the motor vehicle emissions budget in the local SIP. Rounding conventions should be discussed through the interagency consultation process and consider past conformity practices for the area (69 FR 40017, July 1, 2004).
On or after:
The budget test is required once a SIP with a motor vehicle emissions budget is submitted and EPA finds the budget adequate. According to 69 FR 40038 July 1, 2004, EPA must affirmatively find submitted budgets adequate using criteria in §93.118(e)(4) before they can be used in a conformity determination.
Exhibit D-4 summarizes the relationship between SIP and conformity tests.
*Nonattainment and maintenance areas may have different SIPs for a given pollutant with each SIP in a different stage of approval.
SAFETEA-LU section 6011(c) Time Horizon for Conformity Determinations in Nonattainment Areas
This provision provides an option for reducing the time period covered by conformity determinations. It amends section 176(c) of the Clean Air Act (42 U.S.C. 7506(c)) by adding at the end the following:
The conformity rule requires conformity be determined over the time frame of the transportation plan, usually a 20-year time frame, but as provided by SAFETEA-LU conformity may be determined over a shorter timeframe at the election of the MPO. If the MPO elects to demonstrate conformity for less than the full length of the transportation plan per SAFETEA-LU, the conformity determination must be accompanied by a regional emissions analysis, for information purposes only, for the last year of the transportation plan and for any year beyond the term of the conformity determination shown to exceed emission budgets by an information emissions analysis that accompanied a previous conformity determination. Also under SAFETEA-LU, if an area has an approved second 10-year maintenance plan, or has submitted a second 10-year maintenance plan and EPA has found its budgets adequate, the MPO may elect to demonstrate conformity through the last year of the second maintenance plan. The regional emissions analysis must be performed for analysis years that are no more than 10 years apart. Analysis years applicable to the budget tests include:
Any years in the time frame of the transportation plan can be used, provided:
The adequacy process consists of three basic steps: public notification of SIP submission, a public comment period, and EPA's adequacy finding, including response to submitted comments.
EPA intends to review the adequacy of a newly submitted budget through the adequacy process within 90 days of EPA's receipt of a full SIP submission. However, adequacy reviews could take longer particularly when EPA receives significant public comments. (69 FR 40040, July 1, 2004) See Section B of this reference guide for more information.
Exhibits D-5 and D-6 summarize the requirements of conformity tests applicable to different nonattainment areas.
NOx budgets may not be established in ozone SIPs when attainment/maintenance SIPs demonstrate NOx increases are not a problem (e.g., use modeling to demonstrate that NOx growth would not increase ozone).
Source: Section 93.109, Transportation Conformity Rule, 2004 Amendments
Note:
Emissions budgets must be submitted to EPA for approval for all maintenance areas for the last year of the maintenance plan. Budgets are required for all areas, except for areas with a limited maintenance plan or where on-road emissions are insignificant. As with nonattainment areas, all maintenance areas that submit emissions budgets would be allowed to use the budgets for conformity purposes after EPA finds the budget adequate.
The conformity rule requires conformity be determined over the time frame of the transportation plan, usually a 20-year time frame, but as provided by SAFETEA-LU conformity may be determined over a shorter timeframe at the election of the MPO. If the MPO elects to demonstrate conformity for less than the full length of the transportation plan per SAFETEA-LU, the conformity determination must be accompanied by a regional emissions analysis, for information purposes only, for the last year of the transportation plan and for any year beyond the term of the conformity determination shown to exceed emission budgets by an information emissions analysis that accompanied a previous conformity determination. Also under SAFETEA-LU, if an area has an approved second 10-year maintenance plan, or has submitted a second 10-year maintenance plan and EPA has found its budgets adequate, the MPO may elect to demonstrate conformity through the last year of the second maintenance plan.
There are different ways to establish one or more maintenance plan emissions budgets for each applicable pollutant or pollutant precursor. These options and the resulting regional emissions analysis test requirements after a maintenance plan has been submitted and budgets have been found adequate or approved are as follows:
Example #1: A single emissions budget(s) can be established for the last year of the maintenance plan.
In this case, projected regional emissions for the last year of the maintenance plan must be less than or equal to the emissions budget and a qualitative determination of conformity for the years before the last year of the maintenance plan is also required. This qualitative finding must show that there are no factors that 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 must also be used to determine what considerations will be used in order to make such a finding. Alternatively, in certain cases the area could perform a regional emissions analysis to an intermediate year using an adequate or approved budget for the most recent prior year (69 FR 40067).
Projected regional emissions for years beyond the last year of the maintenance plan must also be less than or equal to the emissions budget for the last year of the maintenance plan under this example. For example, such a budget test would be required in cases where the 20-year transportation plan extends beyond the end of the 10-year maintenance plan (unless the MPO, after consultation with the air pollution control agency and solicitation of public comment and consideration of such comments elects to shorten the horizon for conformity, per SAFETEA-LU section 6011(c)).
If a submitted adequate or approved control strategy SIP has established emissions budgets for years in the time frame of the transportation plan, emissions in these years must also be less than or equal to the applicable control strategy SIP budgets for the years addressed by those budgets.
Sample Situation: Using a single emissions budget(s) for the last year of the maintenance plan without the MPO electing to shorten the horizon year for conformity, per SAFETEA-LU section 6011(c).
A qualitative finding is required to be submitted with the conformity determination that states 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 (e.g., 2000-2009). Emissions in the year 2010 and beyond (including the last year of the transportation plan) must not exceed the budget for 2010. In addition, emissions in 2005 must not exceed the budget for 2005, since the 2005 budgets are not superseded by the new budgets contained in the maintenance plan.
Example #2: Additional emissions budgets can be established for years after the last year of the maintenance plan.
For example, some areas are including emissions budgets for conformity purposes for the last year of the transportation plan (e.g. 2020) in their maintenance plan, even though the initial demonstration of attainment is only required to address 10 years. (In such cases, EPA approval of these budgets does not represent approval of a full 20-year maintenance demonstration. The approved budgets are for conformity purposes only and will be superseded when the second 10-year maintenance plan is submitted and the new budgets are found adequate and the approval of these out year budgets is resolved).
Under this example, projected emissions must also be less than or equal to the out-year emissions budget for the years for which they are applicable. The only difference between example 1 and example 2 is that under example 2, the budget that applies after the last year of the maintenance plan is the budget established for that year (or the most recent prior year.)
Sample Situation: Establishing additional emissions budgets for years after the last year of the maintenance plan.
A qualitative finding is required to be submitted with the conformity determination that states 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 (e.g., 2000-2009). Emissions in the years 2010-2019 cannot exceed the budget for 2010. Emissions in 2020 and beyond cannot exceed the budget for 2020. In addition, emissions in 2005 must not exceed the budget for 2005, since the 2005 budgets are not superseded by the new budgets contained in the maintenance plan.
Some maintenance plans may include vehicle emissions projections for some years other than the last year of the maintenance plan without intending that such projections serve as formal emissions budgets. Unless specifically established as a budget, emissions projections should not be interpreted as budgets, and therefore the budget test is not required for these years. This issue should be addressed through the interagency consultation process during SIP development.
* (Note: This table does not apply to limited maintenance plan areas or areas with insignificant on-road emissions)
**Emissions budgets for the years beyond the last year of the maintenance plan may be established. These budgets can be larger than the budget for the last year of the maintenance plan provided offsetting emissions reductions are adopted or committed to in the SIP. Special provisions also apply to isolated rural maintenance areas.
Must a maintenance plan contain emissions budgets for years other than the last year of the plan?
No. However, if no budgets are established for the years before the last year of the maintenance plan, a qualitative finding is required to show that there are no factors that would "cause or contribute to a new violation or exacerbate an existing violation" during these years. Alternatively, in certain cases the area could perform a regional emissions analysis to an intermediate year using an adequate or approved budget for the most recent prior year (69 FR 40067).
If a maintenance plan includes projections of vehicle emissions for one or more years before the last year of the maintenance plan, must those projections be used for emissions budgets and a conformity determination made for each of these years?
No, unless the maintenance plan explicitly states that the projections are considered emissions budgets for the purpose of conformity determinations. This issue should be addressed during the interagency consultation process prior to developing the maintenance plan.
If EPA finds a maintenance plan's emissions budget is inadequate, how can an area determine conformity?
Any conformity determination must be based on the prior submitted or approved SIP budget. If no budget exists, then appropriate interim emissions test(s) must be applied.
The following questions are taken from Part 3 of EPA's Companion Guidance for the July 1, 2004, Final Transportation Conformity Rule: Conformity Implementation in Multi-jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards, July 21, 2004.
How do nonattainment and maintenance areas determine conformity for a given standard once adequate or approved SIP budgets are available for that standard?
Clean Air Act section 176(c)(1) states that federal activities must conform to the SIP. Once a SIP with budgets has been submitted and EPA finds the budgets adequate or approves the SIP, the "budget test" using the new budgets must be used for conformity determinations according to §§93.109 and 93.118 of the conformity rule. EPA's adequacy finding or approval means that the SIP's budgets are an appropriate measure for whether transportation activities conform due to many factors, including:
What geographic areas might budgets from a SIP address, and how is conformity generally determined in multi-jurisdictional areas with SIP budgets?
In a nonattainment or maintenance area located entirely within one state, the state air agency may develop a SIP that establishes either:
In a multi-state nonattainment or maintenance area, the state air agencies may decide to establish SIPs in each state that contain either:
State and local agencies can develop SIPs in many different ways. Section 93.124(d) of the conformity rule acknowledges this fact and covers SIPs developed in areas where there is more than one MPO:
"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 area."
Once budgets have been found adequate or approved, the conformity determination(s) and regional emissions analysis is done for the geographic area that is addressed by the budgets in the SIP. This general principle applies in all situations, although there is flexibility in how the regional emissions analysis is developed, and in coordinating conformity determinations, when several MPOs are involved.
How is conformity done when budgets are established for an entire nonattainment or maintenance area that is within one state?
One MPO. In the simplest case, an area is located entirely within one state and the MPO boundary is the same as the nonattainment/maintenance area boundary. The nonattainment or maintenance area boundary, the MPO, and the SIP budgets all address the same geographic area. In this case, because the SIP establishes budgets for the entire area, the MPO will use those budgets in the regional emissions analysis done for the MPO's plan/TIP conformity determination for the entire nonattainment or maintenance area.
More than One MPO. When budgets are established for the nonattainment or maintenance area as a whole, and there is more than one MPO, the MPOs would complete their respective plan/TIP conformity determinations and submit them to DOT. Once all determinations for a given area are received, DOT would make its conformity determinations at the same time. The MPOs must collectively develop a regional emissions analysis for the entire area that meets the requirements of §93.118 of the rule that would accompany all plan/TIP conformity determinations. For example, all MPOs would have to use the same analysis years for the regional emissions analysis. Each MPO would show conformity of its plan and TIP using the regional emissions analysis done for the entire area.
The MPOs can develop the regional analysis for the area in either one of two ways:
MPOs in one nonattainment or maintenance area may want to coordinate their plan and TIP update cycles as well as the length of their plans.
One or More MPOs and a Donut Area: If there is only one MPO in the nonattainment or maintenance area conducting conformity determinations, the regulations require the MPO to include the emissions estimated from the donut area's existing and proposed transportation system in the regional emissions analysis for the metropolitan transportation plan and TIP conformity determinations. However, either the MPO or the state transportation agency ("state DOT") could estimate emissions from the donut area as decided through interagency consultation.
If there is more than one MPO as well as a donut area in a nonattainment or maintenance area, the MPOs must work together and with the state DOT or other donut area agency as appropriate to create one regional emissions analysis for the entire area that would accompany all plan/TIP conformity determinations. The emissions estimated from the entire area must be less than or equal to the budget(s) established for the entire area, according to the requirements of §93.118. The consultation process would be used to coordinate the analysis years when several agencies are completing emissions analyses, because the same analysis years must be used.
How do nonattainment or maintenance areas with more than one MPO in a single state determine conformity once SIP budgets are adequate or approved, and the SIP establishes subarea budgets for each MPO?
When subarea budgets are created for each MPO, the sum of the subarea budgets equals the total amount of emissions the area can have from the transportation sector and still make progress toward, attain, or maintain the standard. Therefore, if each MPO meets its subarea budgets for a pollutant and standard in accordance with the requirements of §93.118, then the entire area meets the total SIP's purpose for that pollutant and standard. As EPA noted in the January 11, 1993, conformity proposal (58 FR 3780),
"subarea budgets provide additional assurance that through future conformity determinations transportation plans and TIPs will produce emission patterns that will achieve attainment."
When the SIP for an area establishes subarea budgets for conformity purposes, these subarea budgets must be met for plans and TIPs in the area to conform, as required in §93.124(c) and (d) of the conformity rule. Section 93.124(c) states:
"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."
The MPOs can make independent conformity determinations for their plans and TIPs as long as all of the other subareas in the nonattainment or maintenance area have conforming transportation plans and TIPs in place at the time of each MPO's and DOT's plan/TIP determination. In other words, under the conformity rule in order for an MPO or DOT to determine conformity for its subarea, the rest of the area must also be in conformity. The preamble to the November 24, 1993, conformity rule (58 FR 62196) explains this as follows:
"The SIP may specify emissions budgets for subareas of the region, provided that the SIP includes a demonstration that the subregional emissions budget, when combined with all other portions of the emissions inventory, will result in attainment and/or maintenance of the standard. The conformity determination must demonstrate consistency with each subregional emissions budget in the SIP."
Thus, when any subarea demonstrates conformity, it must be demonstrated that all subareas have conforming plans and TIPs. For example, suppose the subarea budgets in a SIP have just been found adequate, and one of the MPOs in the area needs to update its TIP. That MPO can make a conformity determination using its subarea budgets for the first time without waiting for the other MPOs in the area, as long as the other MPOs have conforming plans and TIPs in place, even if these plans and TIPs were previously found to conform using the interim emissions test(s).
Once an area has adequate or approved subarea budgets, if conformity lapses for one subarea, the other subarea(s) can continue to implement projects in their currently conforming plans and TIPs, but they cannot make new plan and TIP conformity determinations until the lapse is resolved and conformity is determined in the lapsed subarea. In other words, if the conformity status of one subarea lapses, the existing plans and TIPs in other subareas continue to be valid and consequences would not apply to any other subareas unless the lapse is not resolved by the time other subareas need to make new conformity determinations.
Why can't an MPO that has its own subarea budgets determine conformity of its transportation plan and TIP when another MPO in the same area is in a lapse?
Section 176(c) of the Clean Air Act clearly states that conformity applies in nonattainment and maintenance areas, rather than individual metropolitan planning areas. Section 176(c) also states that the federal government and MPOs cannot approve transportation activities unless they conform to the SIP and its budgets. Therefore, in a nonattainment or maintenance area with more than one MPO, all MPOs must conform even if the SIP has established subarea budgets.
If an individual MPO lapses, it has not demonstrated that it can conform to its subarea budgets. Therefore, there is no way for the other MPOs in the same area to know whether their transportation plans and TIPs are consistent with the SIP as a whole. When one subarea lapses, there is no way for the other MPO to show that their planned transportation activities would conform to the SIP for the whole area until the lapse is resolved.
How do I know whether the SIP establishes subarea budgets? Are county-by-county emissions projections subarea budgets?
The SIP must specifically state that it creates subarea budgets. County-by-county emissions projections in a SIP inventory are not subarea budgets unless they are specifically labeled as such. Section 93.124(c) of the conformity rule states,
"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."
If county level emissions projections are included in a SIP but not explicitly defined as subarea budgets for the purposes of conformity, the SIP is considered to have budgets for the entire area and MPOs must work together to have plan/TIP conformity determinations for the entire nonattainment or maintenance area approved by DOT at the same time. According to §93.124(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."
If MPOs within one nonattainment or maintenance area would prefer to have subarea budgets, they should communicate their preference to the state and local air agencies within the interagency consultation process during the development of the SIP. Section 93.105(c) of the conformity rule requires interagency consultation on the development of SIPs, as well as transportation plans, TIPs, and conformity determinations.
How do multi-state nonattainment and maintenance areas determine conformity if each state submits a SIP that contains the same budgets for the entire multi-state area?
If these multi-state areas have SIPs that contain budgets for the multi-state area as a whole, one regional emissions analysis would be completed for the entire area using the budget test, according to the requirements in §93.118 of the conformity rule. This regional analysis would accompany all plan/TIP conformity determinations in the area that would be submitted to DOT. Once all determinations for a given area are received, DOT would make its conformity determinations at the same time. The MPOs must collectively develop a regional emissions analysis for the entire area that meets the requirements of §93.118 that would accompany all plan/TIP conformity determinations. For example, all MPOs would have to use the same analysis years for the regional emissions analysis. Each MPO would show conformity of its plan and TIP using the regional emissions analysis done for the entire area.
When would it be likely for state air agencies in a multi-state nonattainment or maintenance area to submit SIPs with budgets that apply to the entire area?
This option would most likely be chosen in areas where there is one MPO responsible for the transportation planning of the entire multi-state nonattainment or maintenance area. However, the option is available to any multi-state nonattainment or maintenance area. In areas with more than one MPO, additional coordination would be necessary for plan/TIP conformity determinations and the regional emissions analysis because they would need to cover the entire nonattainment or maintenance area pursuant to§§93.124(d) and 93.118.
How is conformity determined for multi-state nonattainment or maintenance areas when each state submits a SIP that contains budgets only for its state's portion of the area?
States in a multi-state area have the option of submitting SIPs with budgets for just their own portion of the area that, when taken together, meet the applicable Clean Air Act requirement. Where states have done so and EPA has found such budgets adequate, the MPO or MPOs in each state with such budgets can determine conformity completely independently of the other states. EPA concluded that these states can operate independently for conformity because the Clean Air Act refers to conformity to a SIP. Each state's SIP in these cases includes inventories, control measures and programs, and budgets that apply to only that state's portion of the nonattainment or maintenance area.
States that have SIPs with adequate or approved budgets for only their own portions of a multi-state area are distinct from MPOs in a nonattainment or maintenance area that have subarea budgets within the same SIP, and also distinct from states that have SIP budgets that apply to an entire multi-state nonattainment or maintenance area. Where states have their own SIP budgets, if a conformity lapse is occurring in one state's portion of an area, the MPO(s) in the other state(s) in the nonattainment or maintenance area can continue to make conformity determinations for new or revised transportation plans and TIPs because they continue to show conformity to their SIP's budgets.
In contrast:
Conformity applies for an air quality standard one year after the effective date of EPA's nonattainment designation for that standard. EPA generally believes that conformity will apply for a standard before an area is able to submit a SIP for that standard containing budgets and those budgets are found adequate. section 93.119 of the conformity rule provides direction for how the regional emissions analysis must be done before budgets are available. During this time period, these areas must use the interim emissions test or tests: the build/no-build test, and/or the baseline year test. (See Exhibit D-3 for interim emissions test by pollutant).
If you had a previously approved budget(s) for a given pollutant or a previously submitted budget(s) that EPA had found adequate, you would need to meet the approved or adequate budget(s) for all analysis years. All 8-hour ozone areas with adequate or approved 1-hour ozone budgets must use these budgets for 8-hour ozone conformity before 8-hour ozone budgets are available, unless it is determined through interagency consultation process that using the interim emissions tests is more appropriate for meeting Clean Air Act requirements (69 FR 20022, July 1, 2004). See Chapter 8 for information regarding 8-hour ozone conformity determinations using 1-hour ozone budgets. EPA must affirmatively find submitted budgets adequate before than can be used in a conformity determination.
In the conformity rule, the emissions reduction test is described as the following:
40 CFR §93.119, Criteria and procedures: Interim emissions in areas without motor vehicle emissions budgets.
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 (l). 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.
In summary, before an adequate or approved SIP budget is available, conformity of the transportation plan/TIP or project not from a conforming plan/TIP is generally demonstrated with the interim emissions test(s). The build/no-build tests require an assessment of the emissions impacts of the proposed transportation plan, TIP, or projects not from a conforming plan/TIP (build or "Action" scenario) compared to the emissions impacts of the current transportation system plus projects that are under construction (the no-build or "Baseline" scenario).
In order to pass the build-no-greater-than-no-build test, it must be demonstrated that emissions in the build ("Action") scenario are less than or equal to the no-build ("Baseline") scenario. For the build-less-than-no-build, the emissions in the build ("Action") scenario must be less than the no-build ("Baseline") scenario. For the no-greater-than-1990 test or the no-greater-than-2002 test, the emissions in the "Action" scenario must be lower or equal to 1990 or 2002 emissions. For the less-than-1990 test or the less-than-2002 test, the emissions in the "Action" scenario must be less than 1990 or 2002 emissions by any nonzero amount. This analysis must be performed for the following pollutants and precursors (depending on nonattainment status): VOC, NOx, CO, PM2.5, and PM10.
Exhibit D-8 illustrates how the projects and activities are to be included in the "Baseline" and "Action" scenarios. This process is very important as the outcome of interim emissions tests hinges upon the definition of the "Baseline" and "Action" scenarios and the results of the subsequent regional emissions analysis.
The "Baseline" scenario is defined for each analysis year for the future transportation system that will result from current programs, including the following (except that exempt projects listed in 40 CFR §93.126 and projects exempt from regional emissions analysis as listed in 40 CFR §93.127
need not be explicitly considered):
40 CFR §93.119 (h)(1)-(3),
The "Action" scenario is defined for each analysis year for the transportation system that would result from the implementation of the proposed action (transportation plan, TIP, or project not from a conforming transportation plan/TIP) and all other regionally significant projects in the nonattainment area: (excluding exempt projects listed in 40 CFR §93.126 and projects exempt from regional emissions analysis as listed in 40 CFR §93.127,).
40 CFR §93.119 (i)(1)-(6) and (j)
| Year | "Baseline" (No-build) Scenario | "Action" (Build) Scenario | Notes |
|---|---|---|---|
| Base Year (2002) |
1 All in-place regionally significant highway and transit facilities, services and activities |
||
| Year no more than five years from year conformity is being determined (e.g., 2007) |
1 + |
1 + 2 + |
Areas may wish to do an analysis for the attainment year since it will be required to be an analysis year once there are adequate or approved SIP budgets |
| Intermediate Year (e.g., 2010) |
1 + 2 + |
1 + 2 + 3 + 4 + |
Intermediate year so the analysis years are no more than 10 years apart. |
| Intermediate Year (e.g., 2020) |
1 + 2 + |
1 + 2 + 3 + 4 + |
Intermediate year so the analysis years are no more than 10 years apart. |
| Last Year of Transportation Plan (e.g., 2030) |
1 + 2 + |
1 + 2 + 3 + 4 + |
Source: 40 CFR 93.119
The first analysis year must be no more than five years beyond the year in which the conformity determination is made. The last year of transportation plan's forecast period (40 CFR §93.119(g)(1)), or horizon year as determined by election of MPO under SAFETEA-LU, must also be an analysis year. Analysis years must be no more than ten years apart, so an intermediate year(s) may also be required.
Rounding conventions should be discussed through the interagency consultation process and consider past conformity practices for the area. EPA believes that, at a minimum, rounding conventions should be consistent with the level of precision used for the motor vehicle emissions budget in the local SIP. If questions remain or if the area has never developed a local SIP, the interagency consultation process is the correct place to deal with questions of precision and rounding. (69 FR 40017, July 1, 2004)
The following questions are taken from Part 2 of EPA's Companion Guidance for the July 1, 2004, Final Transportation Conformity Rule: Conformity Implementation in Multi-jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards, July 21, 2004.
What geographic area must be examined in regional emissions analyses and conformity determinations before a nonattainment area has adequate or approved budgets?
In this case, a conformity determination for a transportation plan, TIP, or project not from a plan or TIP must be based on a regional emissions analysis that covers the entire nonattainment area, to satisfy the statute and regulations. Section 93.122(a)(1) of the conformity rule states:
"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."
There must be a regional emissions analysis for the entire nonattainment area, whether the nonattainment area includes one MPO or more than one MPO, a donut area, portions of more than one state, or any combination of these jurisdictions.
MPO(s) must coordinate their plan/TIP conformity determinations together, pursuant to §93.124(d) of the final conformity rule. In the November 24, 1993, final rule, EPA stated:
"Where a nonattainment area includes multiple MPOs, the control strategy SIP may either allocate emissions budgets to each metropolitan planning area, or the MPOs must act together to make a conformity determination for the nonattainment area."
Once DOT receives all plan/TIP conformity determinations for a given nonattainment area, DOT will make its conformity determinations at the same time. In order for one MPO to update or revise its plan and TIP, a DOT conformity determination for each plan and TIP in that nonattainment area must be made at the same time, according to §93.124(d) of the rule.
EPA believes that it is necessary for the conformity determinations and regional emissions analysis to include the entire nonattainment area when there are no SIP budgets to ensure that the requirements of Clean Air Act section 176(c)(1) are met. That is, before SIP budgets are available, in order to determine that transportation activities will not cause a new air quality violation, increase the frequency or severity of a violation, or delay timely attainment or any other milestone in the nonattainment area, it is necessary to consider emissions from the entire area in one regional emissions analysis, and for DOT to make all plan/TIP conformity determinations at the same time.
In a nonattainment area that does not have SIP budgets for conformity, if one MPO in the area can meet the requirements of §93.119 of the rule, but another MPO or a donut area cannot, can the MPO that meets the requirements show that its plan and TIP conform and proceed?
No. EPA believes that before budgets are adequate or approved, the whole nonattainment area must conform to meet the Clean Air Act 176(c)(1) requirements. These requirements are that transportation activities will not:
It is necessary to estimate emissions from the entire nonattainment area in all plan/TIP conformity determinations and the supporting regional analysis because separate SIP budgets are not yet available.
What decisions related to regional emissions analysis must be made in the interagency consultation process?
The agencies responsible for the conformity determination and regional emissions analysis in a nonattainment area, which are the MPOs and possibly the state DOT(s) for donut area in a nonattainment area, should use the interagency consultation process to make certain decisions. Under the conformity rule, there are some aspects of conformity that must be consistent across the nonattainment area, even when there are more than one MPO and they each model their own portion separately, as described above. These include:
In addition, the MPO jurisdictions involved in the conformity determination(s) for the nonattainment area should discuss the planning assumptions they will use in the regional emissions analysis and the sources of that information. Section 93.105(c)(1)(i) of the rule specifically requires that planning assumptions be discussed in the interagency consultation process. Where feasible and appropriate, MPOs and where applicable, state DOTs should use consistent planning assumptions for the regional emissions analysis in their jurisdictions.
How can multiple jurisdictions create a regional emissions analysis for the entire nonattainment area?
The agencies involved in the conformity process in a nonattainment area where there is more than one MPO or a donut area must use the consultation process required by §93.105 of the conformity rule to decide how best to meet this requirement, regardless of whether the area is within one state or is a multi-state area. The consultation process would be used to decide which interim emissions tests apply and what analysis years are used. MPOs must use the same tests and analysis years for the entire nonattainment area.
In nonattainment areas where there is more than one MPO, the MPOs can develop the regional emissions analysis for the area in either one of two ways:
If MPOs in the nonattainment area want to model their emissions separately, each MPO would do a regional emissions analysis that includes the existing transportation system in its part of the nonattainment area as well as all new projects in its plan and TIP. Each MPO would show that the applicable interim emissions test(s) are met for each analysis year under the regulations. These results would then be compiled in one regional emissions analysis for the entire nonattainment area that would accompany each plan/TIP conformity determination. The MPOs in the nonattainment area can work independently to complete the regional emissions analysis for their own parts of the area, but a single analysis would be compiled for the entire nonattainment area to satisfy conformity requirements for an MPO's plan/TIP.
Alternatively, the regional emissions analysis could be completed by showing that the emissions in each analysis year for the entire nonattainment area meet the applicable interim emissions test(s). The MPOs in the area would work together to carry out a regional emissions analysis for the entire nonattainment area that includes all of their plans and TIPs. Again, these modeling results would be presented in one regional emissions analysis for the entire nonattainment area that would accompany the conformity determinations for new or revised plans/TIPs in the nonattainment area.
As an example, suppose there are multiple MPOs within a nonattainment area and they are demonstrating conformity using the build/no-build test. If each MPO has its own travel demand model and prefers to run its own analysis, the analysis must show either that each MPO passes its own build/no-build test; or the "build" scenarios and the "no-build" scenarios from each MPO must be aggregated, and the total "build" emissions from all MPOs must be less than the total "no-build" emissions from all MPOs.
Alternatively, the MPOs could initially create one regional emissions analysis for the entire nonattainment area that meets the build/no-build test.
In either case, to make the demonstration required by the conformity rule, all MPOs must use the same test and the same analysis years for the regional emissions analysis. MPOs in one nonattainment area may want to coordinate their plan and TIP update cycles as well as the length of their plans, as described in the following bullets.
If there is only one MPO in the nonattainment area conducting conformity determinations, the conformity rule requires the MPO to include the emissions estimated from the donut area's existing and proposed transportation system in the regional emissions analysis for metropolitan transportation plan and TIP conformity determinations. However, either the MPO or the state transportation agency ("state DOT") could estimate emissions from the donut area as decided through interagency consultation.
If there is more than one MPO as well as a donut area in a nonattainment area, the MPOs must work together and with the state DOT as appropriate to create one regional emissions analysis for the entire nonattainment area that would accompany each plan/TIP conformity determination. The emissions estimated from the entire area must meet the interim emissions test or tests, according to the requirements of §93.119. Again, the consultation process would be used to coordinate the choice of tests and analysis years when several agencies are completing emissions analyses, because the same tests and analysis years must be used as noted above.
Who is responsible for estimating emissions in a donut area of a nonattainment or maintenance area?
In a nonattainment or maintenance area with a donut area, the lead agency for developing the regional emissions analysis that applies to the donut area can be:
Section 93.105(c)(3) of the conformity rule relies on the interagency consultation process(including the MPO and state DOT) to determine how best to consider projects that are planned for donut areas located outside the metropolitan area and within the nonattainment or maintenance area in the conformity process. Section 93.105 also requires that such procedures for demonstrating conformity of donut area projects be included in an area's conformity SIP that is approved by EPA according to §51.390 of the rule.
Agency roles in integrating travel demand and emissions factor modeling into regional emissions analysis efforts are defined in the interagency consultation process, as discussed in Chapter 2. Typical agency roles in integrating transportation and emissions models are shown in Exhibit D-9.
As stated in the preamble to the 1993 conformity rule preamble (58 FR 62198, Nov. 24, 1993), determination of timely implementation of TCMs in approved SIPs is not based on retrospective analysis of TCM effectiveness or other analysis by the MPOs or DOT to affirmatively determine whether each TCM had its predicted effectiveness (unless the SIP explicitly includes such a requirement).
EPA requires any analysis supporting a conformity determination to reflect the latest available information regarding the effectiveness and actual implementation of the area's TCMs, in order to satisfy the criteria regarding the use of the latest planning assumptions (40 CFR §93.110). Because of this requirement, it is critical that all TCMs included in the SIP be integrated into the transportation modeling process.
In addition, all other regionally significant transportation strategies (whether they are included in the SIP or not) should also be integrated into the plan and TIP conformity analyses. The effects of these measures on travel demand should be properly accounted for, in order to assess the impact on overall regional travel and emissions, either as part of the four-step modeling process or through off-model analysis, as discussed below. Non-regionally significant TCMs can be analyzed with best professional practice such as performing an off-model analysis determined through the interagency consultation process.
Off-model analysis can be regarded as "reasonable professional practice" and should be determined through the interagency consultation process. Off-model analysis can be used in situations such that emissions estimates from projects cannot be obtained through the regional modeling process. One such situation is to estimate emissions from projects that are not regionally significant, but which have or affect vehicle travel. 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 street. In addition, the benefits of TCMs that cannot be analyzed through the regional modeling process may be estimated in accordance with reasonable professional practice (i.e., off-model analysis) (58 FR 62211, Nov. 24, 1993).
A variety of sketch planning tools are available to estimate the impact of various TCMs on local travel. These can be used to develop estimates of the change in travel characteristics (in terms of VMT, vehicle trips and average speed) on affected roadways. Adjustments can then be made to the travel data output by the regional travel demand model. Another situation under which off-model analysis can be applied is when a number of planning agencies may have limited ability to perform mode choice analysis because they do not have mode choice models or the models they have are insufficient to look at a particular issue. Examples of off-model analysis techniques include:
One of the earliest reports on these methods was commissioned by EPA in the late 1970s [6] . The manual leads an analyst through the steps necessary to estimate the size of the target market and properly estimate the changes in travel indicators (mode share, emissions, etc.) likely to result from the application of various demand management measures. Methods for analyzing various traffic operations improvements also are discussed, including green band and computerized traffic-signal timing methods. Worksheets and simple computer applications are explained step-by-step, and examples are provided.
The FHWA is distributing a special software product which can serve as a substitute or enhancement to a conventional mode-choice model capability. The TDM model incorporates a pivot-point procedure to estimate mode-choice changes, meaning that it forecasts the change in a starting mode share based on information as to the changes in decision variables associated with the policy action. A wide group of TCM, TDM, and other strategies can be considered, individually, or grouped into programs, with great flexibility at varying the effectiveness levels of the strategies and targeting their application. The starting base may be either trip tables from an existing planning process, special trip tables formed from survey data, or simply aggregate estimates of person, vehicle and/or transit trips. The coefficients in this model have been synthesized from national experience, and can be altered by the user to use local or other coefficient estimates. Results are both aggregate and in trip table format. The trip table results can be returned to the four-step process (if applicable) for traffic assignment [8] .
More recently, microcomputer-based spreadsheet models have been developed to carry out similar analysis. One spreadsheet model, originally developed for the San Diego Association of Governments (SANDAG) and later developed for the FHWA, evaluates the effect of TCMs on travel, emissions, and cost. Specifically, it calculates baseline travel characteristics, estimates TCM impacts on trips, VMT and speed, prepares emissions inventory estimates and estimates costs of control measures to the public and private sectors and to vehicle owners. The travel module is a spreadsheet that contains equations for quantifying TCM impacts on travel based on user inputs and elasticities (either default values based on literature reviews or locally derived values that are input). The emissions module is designed to accept inputs from either MOBILE (the Federal version) or EMFAC (the California version) emissions factor models that represent fleet emissions rates for the area of interest.
The COMMUTER Model is a spreadsheet-based tool featuring a user-friendly interface to calculate air quality and travel benefits. The COMMUTER model uses a pivot-point methodology to estimate changes in trips and VMT from baseline conditions and a look-up table of emission factors from EPA's MOBILE model to estimate the resulting emissions changes. COMMUTER employs key shortcuts in the amount of data used and the number of micro-level calculations that are performed. The result is a conscious but judicious tradeoff of some accuracy for a significant increase in ease and flexibility for the user compared to previous methods. COMMUTER offers two levels of analysis. Regional analyses can be done on programs covering an urban area, a central business district or a highly traveled corridor. Site-specific analyses enable benefits to be projected for programs at individual worksites. A revised version of the COMMUTER Model was released by EPA in October 2005 and can be found at: www.epa.gov.
This report [10] provides a step-by-step approach for quantitatively estimating the travel and emissions changes that are possible from implementing a number of transportation control measures. The report includes equations for calculating changes in the number of trips, vehicle miles traveled, and speed, as well as methods for estimating emission effects of these travel activity changes.
This report [11] illustrates the use of EPA's Methodologies for Estimating Emission and Travel Activity Effects of TCMs by applying the methodologies to the estimation of benefits for six operating TCM programs.
This procedure, known as QRS, consists of a collection of short-cut, parametric methods which may be used to perform a transportation analysis in the absence of a local model system. Procedures exist to cover the steps of trip generation through traffic assignment, including mode choice. It exists in either microcomputer or manual form, and allows users with minimum data and computer capability to form reasonable estimates of travel response.
Few sketch models, if any, attempt to estimate secondary effects on neighboring roadways (e.g. due to shifts in trip routing). This simplistic approach is normally acceptable when the impact of the TCM is not expected to be regionally significant. This would not be the case, however, for a TCM that is projected to have significant regional impacts. In such a case, the travel impacts of the TCM should be modeled using the regional travel demand model, so that any secondary effects are properly evaluated. Additional guidance on this issue can be found in the Manual of Regional Transportation Modeling Practice developed for NARC (Section 3.5, Supplemental Methods, pp. 3-73).
Another area of off-model analysis relates to the estimation of travel for heavy-duty vehicles [12] . Typically, the four-step process models are designed to allocate household and employment activity to specific geographic locations across the region. Freight activity is not typically addressed in this process. As a result, a variety of techniques have been developed to forecast the VMT associated with heavy-duty vehicles. These techniques span the gamut from assigning freight a constant share of non-freight VMT estimates to the development of independent econometric forecasting models to estimate heavy-duty truck travel. Heavy-duty vehicles can be a significant part of the nitrogen oxide (NOx) motor vehicle emissions inventory in a typical urban area. Thus, in ozone and PM nonattainment areas where NOx is an identified emission precursor, there is growing interest in how heavy-duty truck travel is estimated and whether the trucks' activity levels (both VMT and speeds) are being properly represented in emissions inventories in the SIP and those used to demonstrate conformity with the SIP.
[1] See SAFETEA-LU section 6011(c) for Clean Air Act provisions related to horizon years for conformity.
[2] The three 1-hour ozone maintenance areas that are still required to do conformity, are using the budget test and have to meet timely implementation for any TCMs.
[3] EPA issued PM2.5 and revised PM10 hot spot analyses requirements in March 2006. This Guide has not been updated to reflect those changes.
[4] The submitted implementation plans do not supersede the motor vehicle emissions budgets in approved implementation plans that address the same time frame and CAA purpose.
[5] 40 CFR §93.119(i)(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.
[6] Cambridge Systematics, Inc., Transportation Air Quality Analysis - Sketch Planning Methods (two volumes), report prepared for U.S. EPA, Washington, DC, December 1979.
[7] User's Guide: Travel Demand Evaluation Model, COMSIS Corporation for the Federal Highway Administration, 1993.
[8] User Manual for Software Developed to Quantify the Emissions Reductions and Cost Effectiveness of Selected Transportation Control Measures, prepared for the Federal Highway Administration, July 1994.
[9] Sierra Research and JHK & Associates, Methodologies for Quantifying the Emissions Reductions of Transportation Control Measures, prepared for the San Diego Association of Governments, 1990.
[10] EPA420-R-94-002, July 1994.
[11] EPA420-R-98-002, March 1999.
[12] NCHRP Report 388, A Guidebook for Forecasting Freight Transportation Demand, Cambridge Systematics with Leeper, Cambridge & Cambell, Sydec and Thomas Corsi and Curtis Grimm, 1997.
