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Appendix X

Transportation Conformity Background

1.0 Introduction

The Clean Air Act1 requires that Federal actions conform to a State’s State Implementation Plan 

(SIP). Specifically the Clean Air Act requires the action/activity will not:

• Cause or contribute to any new violation of any National Ambient Air Quality Standard 

(NAAQS) in any area;

• Increase the frequency or severity of any existing violation of any NAAQS in any area; or,

• Delay timely attainment of any NAAQS or any required interim emission reductions or any 

other milestones in any area.

To implement this requirement, the Clean Air Act directed2 the United States Environmental 

Protection Agency (USEPA) to issue rules that governed how conformity determinations would 

be conducted for two categories of actions/activities: 1) those dealing with transportation plans, 

programs and projects (Transportation Conformity), and 2) all other actions, e.g., projects 

requiring Federal permits. This latter category is referred to as General Conformity.

The Federal Transportation Conformity Rule (40 C.F.R. § 93.100-129) provides the process by 

which the air quality impact of transportation plans, transportation improvement programs, and 

projects are analyzed. The agency preparing transportation plans (projections of twenty or 

more years), transportation improvement programs (projections of at least four years), or 

approving a transportation project must analyze the emissions expected from such a proposal in 

accordance with the Transportation Conformity Rule.3

For the purposes of transportation conformity, the emission budget is essentially a cap on the 

total emissions allocated to onroad vehicles. The projected regional emissions calculated 

based on a transportation plan, transportation improvement program, or project, may not 

exceed the motor vehicle emissions budget or cap contained in the appropriate SIP. Emissions 

in years for which no motor vehicle emissions budgets are specifically established must be less 

than or equal to the motor vehicle emissions budget established for the most recent prior year.

Emission budgets in New Jersey are established by nonattainment area and Metropolitan 

Planning Organization (MPO) boundary. New Jersey is part of two PM2.5 nonattainment areas 

as shown in Figure 1: ten counties in northern New Jersey associated with New York City and 

three counties in southern New Jersey associated with Philadelphia. 

 1 42 U.S.C. § 7506.

2 42 U.S.C. § 7506.

3 For New Jersey, such plans are prepared by three Metropolitan Planning Organizations (North Jersey 

Transportation Planning Authority, South Jersey Transportation Planning Organization, and Delaware 

Valley Regional Planning Commission).
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BERKS

PIKE

ORANGE

SUFFOLK

LUZERNE

KENT

BUCKS

OCEAN

CHESTER

LANCASTER

MONROE

SUSSEX

FAIRFIELD

BURLINGTON

MORRIS

SCHUYLKILL

CECIL

WAYNE

ATLANTIC

NEW HAVEN

SALEM

KENT

COLUMBIA

CARBON

HARFORD

LEHIGH

WARREN

SULLIVAN

WYOMING

MONMOUTH

LEBANON

CUMBERLAND

HUNTERDON

WESTCHESTER

NASSAU

MIDDLESEX

BERGEN

PUTNAM

MERCER

PASSAIC

ESSEX

LITCHFIELD

UNION

NEW CASTLE

MONTGOMERY

LACKAWANNA

SOMERSET

MIDDLESEX

CAMDEN

GLOUCESTER

NORTHAM PTON

QUEEN ANNES

CAPE MAY

ROCKLAND

DELAWARE

ULSTER

QUEENS

CAROLINE

PHILADELPHIA

HARTFORD

KINGS

HUDSON

BRONX

RICHMOND

NEW YORK

In Attainment 

NY_NJ_LI_CT_nonattainment_area

PA_NJ_DE_nonattainment_area

Geographic Areas

DE

NJ

CT

NY

PA

MD

In Attainment

NNJ/NY/CT Nonattainment Area

SNJ/Phila. Nonattainment Area

Figure 1

USEPA Designations of Nonattainment Areas for the PM2.5

National Ambient Air Quality Standard

There are three MPOs in New Jersey that cover the geographic areas shown in Figure 2. 

These are the North Jersey Transportation Planning Authority (NJTPA), the Delaware Valley 

Regional Planning Commission (DVRPC), and the South Jersey Transportation Planning 

Organization (SJTPO). Each MPO is responsible for the transportation plans and transportation 

improvement programs for its designated area. The MPOs each work in consultation with the 

Federal Highway Administration, the New Jersey Department of Transportation (NJDOT), the 

USEPA, and the New Jersey Department of Environmental Protection (NJDEP) to remain at or 

under established transportation emission budgets for their area. Transportation conformity 

budgets for PM2.5 are developed for each MPO by adding the onroad emissions from individual 

counties within each MPO planning area located within the New Jersey portions of the PM2.5

nonattainment areas. This results in the formation of the following three areas for budget 

development:

• Nine counties located in the NJTPA MPO planning area and the New Jersey portion of the 

NNJ-NY-CT PM2.5 nonattainment area (Bergen, Essex, Hudson, Middlesex, Monmouth, 

Morris, Passaic, Somerset, and Union counties), 

• Mercer county located in the DVRPC MPO geographic area and the NNJ-NY-CT 

nonattainment area, and 

• Three counties included in the DVRPC MPO geographic area and the New Jersey portion of 

the SNJ/Phila. PM2.5 nonattainment area (Burlington, Camden, and Gloucester counties).
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Figure 2

Metropolitan Planning Organizations in New Jersey

Delaware Valley Regional

Planning Commission

North Jersey Transportation

Planning Authority

South Jersey Transportation

Planning Organization
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The South Jersey Transportation Planning Organization does not have to perform transportation 

conformity for PM2.5 because all counties within their planning area have been, and continue to 

be, designated attainment of the PM2.5 15 μg/m3 annual and 35 μg/m3 daily NAAQSs.

2.0 Transportation Conformity for PM2.5 Annual and Daily Standards

2.1 Interim Tests Were Used Prior to the Establishment of Budgets

The Transportation Conformity Rules that established the criteria and procedures relating to 

Transportation Conformity for PM2.5 were promulgated by the USEPA on July 1, 2004.4

 

Transportation Conformity for PM2.5 became effective on April 5, 2006; the effective date is 

based on a one-year grace period from the effective date of designations, April 5, 2005. In 

addition, the USEPA issued a Final Rule on March 24, 20105 that established the 

Transportation Conformity requirements for the 24-hour 2006 PM2.5 NAAQS. Areas subject to 

transportation conformity for both the 15 μg/m3 annual and 35 μg/m3 daily PM standards shall 

continue to use their annual PM2.5 budgets to satisfy the transportation conformity requirements

for both the annual and daily PM2.5 standards. 

Before a SIP budget is available, either through an adequacy finding or approval by the USEPA, 

conformity of the transportation plan, transportation improvement program, or project not from a 

conforming plan is demonstrated with the interim emissions tests.6

 The interim emissions tests 

for PM2.5 require that emissions from the proposed transportation system are less than or equal 

to the emissions from either the baseline year or the existing (“no-build”) transportation system. 

The MPOs performing planning in PM2.5 nonattainment areas were required to utilize an interim 

emissions test until emission budgets were approved or found adequate by the USEPA. Once 

the budgets were in place, MPOs needed to demonstrate that emissions from the proposed 

transportation system were less than or equal to the budgets. Currently, the NJTPA and the 

DVRPC are using 2009 attainment PM2.5 budgets that have been found adequate by the 

USEPA for the New Jersey counties in the NY-NJ-CT and SNJ.-Phila. nonattainment areas.7

 

2.2 PM2.5 Precursors

The final rule to add PM precursors to the transportation conformity rule balanced the need to 

protect air quality with the need to conserve the limited resources of state and local 

transportation and air quality agencies. For transportation conformity, one PM2.5 precursor –

oxides of nitrogen (NOx), was considered in the conformity process in PM2.5 nonattainment 

areas,8 pursuant to the following USEPA requirements:

 

• Regional emissions analysis must include NOx as a PM2.5 precursor in all PM2.5

nonattainment areas, unless the head of the state air agency and the USEPA Regional 

Administrator make a finding that NOx is not a significant contributor to the PM2.5 air 

quality problem in a given area. NOx is the only PM2.5 precursor that must be examined 

in conformity analyses (unless a finding is made) because data indicates that NOx

contributes to the air quality problem in most PM2.5 nonattainment areas. 

• VOC, SO2, and NH3 precursor emissions need only be examined if they are determined 

 4 69 Fed. Reg. 40004-81 (July 1, 2004). 5 75 Fed. Reg. 14260- 85 (March 24, 2010) 6 40 C.F.R. § 93.119. 7 75 Fed. Reg. 33614-5 (June 14, 2010). 8 70 Fed. Reg. 24280-92 (May 6, 2005).
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to be of concern for a particular area; i.e., if the head of the state air agency or the 

USEPA Regional Administrator makes a finding that the onroad emissions of any of 

these precursors is a significant contributor to the area’s PM2.5 air quality issue, or if 

through interagency consultation it is determined that inclusion of additional precursors 

is warranted and desirable.

The following criteria are considered in making significance or insignificance findings for PM2.5

precursors:

• The contribution of onroad emissions of the precursor to the total baseline SIP inventory; 

• The current state of air quality for the area; 

• The results of speciation monitoring for the area; 

• The likelihood that future motor vehicle control measures will be implemented for a given 

precursor; and,

• Projections of future onroad emissions of the precursor. 

There has been no new information or findings since the PM2.5 attainment demonstration 

conformity budgets9 were submitted to indicate that additional precursors have become or will 

become of concern. As such the New Jersey transportation conformity budgets for PM2.5

precursors only include the establishment of an annual NOx budget for the two PM2.5 

nonattainment areas addressed by this redesignation and maintenance plan SIP revision. 

2.3 Road Dust and Construction Related Fugitive Dust

The Federal Transportation Conformity Rule specifies that re-entrained road dust is to be 

included as a component of direct PM2.5 for transportation conformity regional emissions 

analysis only if the USEPA Regional Administrator or the director of the State air agency has 

made a finding that emissions from re-entrained road dust within the area are a significant 

contributor to the PM2.5 nonattainment problem and has so notified the MPO and NJDOT.10 

Findings of significance have not been made for either re-entrained road dust or constructionrelated fugitive dust for the New Jersey portions of the NNJ-NY-CT and the SNJ-Phila. 

nonattainment areas. As described in the PM2.5 attainment demonstration11, a number of 

source apportionment studies have concluded that the primary components of the PM2.5 mass in 

New Jersey are: secondary sulfate from large coal-fired power plants, automotive emissions 

and biomass burning. Re-entrained road dust and fugitive dust from road construction projects 

would be monitored as a component of soil material. Soil material makes up a relatively small 

percentage of the PM2.5 mass measured in New Jersey monitors.12 Therefore, neither reentrained road dust emissions nor fugitive dust emissions from highway and transit project 

construction have been included in the PM2.5 transportation conformity budgets. 

 9

 NJDEP. Final State Implementation Plan Revision for Attainment and Maintenance of the Fine 

Particulate Matter National Ambient Air Quality Standard. New Jersey Department of Environmental 

Protection, March 26, 2009.

10 40 C.F.R. § 93.119(f)(8). 11 NJDEP. Final State Implementation Plan Revision for Attainment and Maintenance of the Fine 

Particulate Matter National Ambient Air Quality Standard. New Jersey Department of Environmental 

Protection, March 26, 2009.

12 Hopke, P. K. and Kim, E. Application of Advanced Factor Analysis Modeling to Apportion PM2.5 in New 

Jersey. Center for Air Resources Engineering and Science, Clarkson University, March 2005.
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2.4 Early Budgets for PM2.5

In a 2006 SIP revision13 (referred to hereafter as the “2006 SIP Revision”), New Jersey 

established “early progress” PM2.5 transportation conformity emission budgets including 

documentation of the justification for the early budgets. Early progress 2009 budgets were 

established for direct PM2.5 and annual NOx for the New Jersey portion of the NNJ-NY-CT 

nonattainment area. This nonattainment area includes one county in the DVRPC MPO planning 

area (Mercer County), with the other nine counties in the NJTPA MPO planning area. These

early progress budgets for New Jersey were approved by the USEPA on July 10, 2006.14 

Following the USEPA approval, these budgets have been used for subsequent transportation 

conformity determinations made by the NJTPA and the DVRPC for this nonattainment area. 

In the State’s 8-hour ozone attainment demonstration SIP15, the NJDEP updated the planning 

assumptions used in the transportation conformity analyses. The distribution of vehicle miles 

traveled (VMT) between vehicle types was updated to reflect a greater fraction of the total VMT 

attributed to the heaviest class of diesel trucks (trucks greater than 60,000 lbs. Gross Vehicle 

Weight Rating). When the updated VMT/vehicle type mix was used, the predicted emissions of 

direct PM2.5 and annual NOx increased. The higher predictions resulted in values that were 

significantly higher than the existing budgets. The amount of the budget exceedance for Mercer 

County was much greater than the emission reductions that could be achieved by changes to 

transportation projects by 2009. Therefore, an update to the original early progress budget for 

Mercer County was proposed on December 17, 2007 as a SIP revision.16 This SIP revision was 

approved by the USEPA, effective June 5, 2008.17 This enabled the DVRPC MPO to meet its 

subsequent transportation conformity requirements.

The existing budgets for 2009 are considered attainment year budgets for PM2.5 and NOx and 

they are being used to address transportation conformity for both the PM2.5 annual and daily 

NAAQS.

2.6 Release of the MOVES Model

On March 2, 2010 the USEPA officially released the MOVES2010 Motor Vehicle Emissions 

Model for emissions inventories in SIPs and transportation conformity18. MOVES replaced the 

MOBILE6 model for estimating emissions from onroad vehicles. The approval of the MOVES 

model started a two-year transportation conformity grace period which ended on March 2, 2012, 

 13 NJDEP. State Implementation Plan (SIP) Revisions for the Attainment and Maintenance of the 8-Hour 

Carbon Monoxide National Ambient Air Quality Standard, 1-Hour Ozone National Ambient Air Quality 

Standard, and Fine Particulate Matter National Ambient Air Quality Standard; and the 2002 Periodic 

Emission Inventory. New Jersey Department of Environmental Protection, May 2006. 14 71 Fed. Reg. 38770-72 (July 10, 2006).

15 NJDEP. Final State Implementation Plan (SIP) Revisions for the Attainment and Maintenance of the Ozone 

National Ambient Air Quality Standard - 8-Hour Ozone Attainment Demonstration. New Jersey Department of 

Environmental Protection, October 29, 2007. 

16 NJDEP. Proposed State Implementation Plan Revision For Attainment of the Fine Particulate Matter 

National Ambient Air Quality Standard, Update of Early Transportation Conformity Budgets for Mercer 

County. New Jersey Department of Environmental Protection, December 17, 2007. 

17 73 Fed. Reg. 24868 (May 6, 2008). 18 75 Fed. Reg. 9411-9414 (March 2, 2010)
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after which MOVES2010 was originally required to be used for new regional emissions analyses 

for transportation conformity. 

Prior to March 2, 2012, the USEPA issued a final rule to extend the grace period before the 

MOVES model is required for regional emissions analyses for transportation conformity 

determinations. The rule provided an additional year to the previously established two-year 

conformity grace period so the MOVES2010a will not be required for regional conformity 

analyses until March 2, 201319. 

The most significant impact of the change in emissions models from MOBILE6 to MOVES 

involves the prediction of direct PM2.5 emissions. Direct PM2.5 emissions are significantly 

greater when MOVES is used instead of MOBILE6. The existing PM2.5 annual budgets for 2009 

are attainment year budgets for the PM2.5 standards and the monitoring data has indicated 

levels below the PM2.5 standards for both nonattainment areas. Therefore, the attainment SIPs 

(that generated the budgets) continue to meet their purpose when new MOVES-based budgets 

are generated using the same control strategies and the latest planning data. This 

redesignation and maintenance plan SIP revision contains MOVES-based 2009 PM2.5 budgets 

in addition to the 2025 budgets for the last year of the maintenance period. 

 19 77 Fed. Reg. 11394-11401 (February 27, 2012)