The State of New Jersey

Department of Environmental Protection

Proposed Revisions to the Enhanced Inspection and 

Maintenance (I/M) Program for the State of New Jersey

Proposed I/M Program Modeling and Revised 

Performance Standard Modeling 

SIP Revision

December, 2009

i

Preface

This document is a revision to the State of New Jersey’s Inspection and Maintenance 

(I/M) program State Implementation Plan (SIP). Specifically, this document provides 

the United States Environmental Protection Agency (USEPA) with documentation on 

the emission impacts that will result from proposed changes to New Jersey’s enhanced 

I/M program including a comparison to the USEPA I/M performance standard. The 

proposed changes to New Jersey’s I/M program include: the establishment of a new 

exhaust emission test for gasoline fueled vehicles called the Two Speed Idle (TSI) test 

that will replace both the ASM5015 and 2500 RPM tests, the elimination of repair cost 

waivers, the increase in the inspection frequency (to annual) for certain classes of 

commercial vehicles such as limousines, taxis and jitneys, and the subjecting of light 

duty diesel vehicles to emissions testing. The primary reason for this SIP revision is to 

satisfy the USEPA's requirements for the State to implement the changes to the I/M 

program. The State of New Jersey entered into a contract, effective May 6, 2008, with 

Parsons Commercial Technology Group Inc. that includes the transition to the proposed 

I/M program. 

Acknowledgments

The New Jersey Department of Environmental Protection (NJDEP) acknowledges the 

efforts and assistance of the many agencies and individuals whose contributions were 

instrumental in the preparation of this SIP revision. In particular, the NJDEP wishes to 

acknowledge the many individuals within the New Jersey Department of Transportation 

(NJDOT), the New Jersey Motor Vehicle Commission (NJMVC), the USEPA Region II, 

and the staff within the NJDEP for their assistance and guidance.
ii

Table of Contents:

PREFACE ........................................................................................................................ I

ACKNOWLEDGMENTS................................................................................................... I

TABLE OF CONTENTS.................................................................................................. II

LIST OF TABLES........................................................................................................... III

LIST OF APPENDICES .................................................................................................IV

ACRONYMS AND ABBREVIATIONS.............................................................................V

EXECUTIVE SUMMARY................................................................................................VI

I. INTRODUCTION...................................................................................................... 1

A. BACKGROUND......................................................................................................... 1

B. PURPOSE ............................................................................................................... 1

II. PROPOSED I/M PROGRAM MODELING AND REVISED PERFORMANCE 

STANDARD MODELING ................................................................................................ 2

A. BACKGROUND ........................................................................................................ 2

B. MODELING PARAMETERS AND ASSUMPTIONS ............................................................ 3

C. MODELING RESULTS ............................................................................................. 13

III. CONCLUSION ..................................................................................................... ..25
iii

LIST OF TABLES:

TABLE 1: PERFORMANCE STANDARD AND NJ ENHANCED I/M PROGRAM DESIGNS ................. 4

TABLE 2: VARIOUS VEHICLE CATEGORIES AND APPLICABLE EMISSION TESTS......................... 9

TABLE 3: OTHER MODELING ASSUMPTIONS ....................................................................... 13

TABLE 4: MODELING RESULTS .......................................................................................... 25
iv

List of Appendices:

Appendix I: History of New Jersey’s I/M SIP

Appendix II: Documentation of the Emission Benefit Estimates for the Performance of 

I/M on Light Duty Diesel Vehicles

Appendix III: MOBILE Input and Output files for 2013 Modeling of the NJ Existing I/M 

Program, NJ Proposed I/M Program and USEPA I/M Performance Standard (available 

in electronic format)

Appendix IV: Calculation Spreadsheet for 2013 Modeling of the NJ Existing I/M 

Program, NJ Proposed I/M Program and USEPA I/M Performance Standard

Appendix V: Public Participation
v

Acronyms and Abbreviations:

ASM Acceleration Simulation Mode

CAA Clean Air Act

CIF Central Inspection Facility

CO Carbon Monoxide

EGR Exhaust Gas Recirculation

Fed. Reg. Federal Register

gpm Grams Per Mile

HC Hydrocarbons

HDGV Heavy Duty Gasoline Vehicle

I/M Inspection and Maintenance

LDGT Light Duty Gasoline Truck

LDGV Light Duty Gasoline Vehicle

LEV Low Emission Vehicle

MY Model Year

NAAQS National Ambient Air Quality Standards

NHSDA National Highway System Designation Act

NJDEP New Jersey Department of Environmental Protection

NJMVC New Jersey Motor Vehicle Commission

NJDOT New Jersey Department of Transportation

NOx Oxides of Nitrogen

OBD On-Board Diagnostics

OTR Ozone Transport Region

PCTG Parsons Commercial Technology Group Inc.

PCV Positive Crankcase Ventilation

PIF Private Inspection Facility

ppm Parts Per Million

psi Pounds Per Square Inch

ROP Rate of Progress

RPM Revolutions Per Minute

SIP State Implementation Plan

TSI Two-Speed Idle

USEPA United States Environmental Protection Agency

VMT Vehicle Miles Traveled

VOC Volatile Organic Compounds

ZEV Zero Emission Vehicle
vi

Executive Summary

This document is a revision to the State of New Jersey’s enhanced Inspection and 

Maintenance (I/M) State Implementation Plan (SIP) due to proposed changes to the I/M 

program. This SIP revision includes emission modeling that quantifies the impacts of 

the proposed program changes including a comparison to the USEPA performance 

standard. The primary reason for this SIP revision is to satisfy the USEPA's 

requirements for the State to implement the changes to the I/M program. It 

demonstrates that the proposed changes to the I/M program do not compromise the 

State’s efforts to meet and/or maintain National Ambient Air Quality Standards 

(NAAQSs) for ozone or carbon monoxide. It also demonstrates that New Jersey’s I/M

program continues to meet the USEPA I/M performance standard after the proposed 

changes to the I/M program are implemented. The State of New Jersey entered into a 

contract, effective May 6, 2008, with Parsons Commercial Technology Group Inc. that 

includes the transition to the proposed enhanced I/M program. In addition, the 

Department of Environmental Protection (Department) is finalizing new rules and rule 

amendments, and the Motor Vehicle Commission is finalizing changes to both 

regulation and law, that implement these changes to the I/M program. 

New Jersey has proposed numerous changes to its enhanced I/M program to be fully 

implemented by 2012. These changes include the following:

o Emission tests will no longer require the use of a dynamometer. Emission tests 

will include On-Board Diagnostics (OBD), gas cap, visible smoke and two-speed 

idle (TSI) tailpipe tests. The TSI test replaces both the ASM5015 and 2500 RPM 

tests.

o Repair cost waiver provisions have been removed.

o Gas cap testing is excluded for vehicles of model year 2001 and newer.

o Certain classes of commercial vehicles, limousines, taxis and jitneys will require 

annual (more frequent) inspection.

o Central Inspection Facilities (CIFs) will not conduct any inspections for vehicles 

less than four years old, or for any cars at change of title. If a motorist wants a 

courtesy inspection, he/she will be directed to Private Inspection Facilities (PIFs). 

o Light duty diesel vehicles will now be subject to emission testing. 

This SIP revision evaluates the emission impacts of the proposed enhanced I/M 

program changes by comparing emission factors calculated using the USEPA 

MOBILE6 model for the existing and proposed programs. The emission factors were 

estimated for 2013 which follows the expected implementation of the proposed 

enhanced I/M program. The model results indicate that there is no significant difference 

between emission factors for the existing and proposed enhanced I/M programs for 

ozone precursors (VOCs and NOx). The proposed enhanced I/M program provides a 

small reduction in the predicted carbon monoxide emission factor relative to the existing 

program.
vii

This SIP revision also revises the State's enhanced I/M performance standard modeling 

to account for the proposed I/M program changes. This revision shows that the State's 

proposed enhanced I/M program meets the low enhanced performance standard.
1

I. Introduction:

A. Background

In accordance with the requirements of the Clean Air Act (CAA), the State of New 

Jersey implemented an enhanced Inspection and Maintenance (I/M) program on 

December 13, 1999. The implementation of this program continues to be an integral 

part of New Jersey’s plan to attain and maintain compliance with the health-based 

National Ambient Air Quality Standards (NAAQS) for ozone and for carbon monoxide. 

Reducing the emissions of carbon monoxide, as well as emissions of volatile organic 

compounds (VOCs) and oxides of nitrogen (NOx) (precursors to ozone formation), will 

help the State in its efforts to improve its air quality and protect the health and welfare 

of its citizens. 

New Jersey’s enhanced I/M program design is a hybrid network system that consists of 

both centralized (test-only) and decentralized (test-and-repair) facilities. A private 

contractor to the State operates the centralized portion of the inspection network. The 

decentralized network is comprised of over 1,300 Private Inspection Facilities (PIFs) 

that are privately owned and operated, and licensed by the NJMVC to perform vehicle 

inspections on behalf of the State. This hybrid network design gives motorists a choice 

as to where to have their vehicles inspected. 

B. Purpose

This document revises the State of New Jersey’s enhanced Inspection and 

Maintenance (I/M) State Implementation Plan (SIP) due to proposed changes to the I/M 

program. A complete history of New Jersey’s I/M SIP is provided in Appendix I. This 

SIP revision includes emission modeling that quantifies the impacts of the proposed 

program changes including a comparison to the USEPA performance standard. The 

primary reason for this SIP revision is to satisfy the USEPA's requirements for the State 

to implement the changes to the I/M program. It demonstrates that the proposed 

changes to the enhanced I/M program do not compromise the State’s efforts to meet 

and/or maintain National Ambient Air Quality Standards (NAAQSs) for ozone or carbon 

monoxide. It also demonstrates that New Jersey’s I/M program continues to meet the 

USEPA I/M performance standard after the proposed changes to the I/M program are 

implemented. The State of New Jersey entered into a contract, effective May 6, 2008, 

with Parsons Commercial Technology Group Inc. that includes the transition to the 

proposed enhanced I/M program. The Department of Environmental Protection 

(Department) is finalizing new rules and rule amendments to N.J.A.C. 7:27-14, 7:27-15, 

7:27B-4 and 7:27B-5 that implement these changes to the I/M program. In addition, the 

Motor Vehicle Commission is finalizing changes to both regulation and law to implement 

these changes.
2

II. Proposed I/M Program Modeling and Revised Performance Standard Modeling

A. Background 

As part of its final rule for Inspection and Maintenance (I/M) requirements, the USEPA 

established a “model” program for areas that were required to implement enhanced I/M 

programs. This model program is termed by the USEPA as the “I/M performance 

standard” and is defined by a specific set of program elements.1 The purpose of the 

performance standard is to provide a gauge by which the USEPA can evaluate the 

adequacy and effectiveness of each state’s enhanced I/M program. As such, states are 

required to demonstrate that their enhanced I/M programs achieve applicable area-wide 

emission levels for the pollutants of interest that are equal to, or lower than, those which 

would be realized by the implementation of the model program. The USEPA allows for 

a margin of error of +/- 0.02 gpm in determining compliance with the performance 

standard.2

Originally, the USEPA only designed one enhanced performance standard, as specified 

at 40 C.F.R. §51.351, and required all enhanced I/M program areas to meet or exceed 

that standard. However, on September 18, 1995, the USEPA promulgated the “low” 

enhanced performance standard.3, 4 The low enhanced performance standard is a less 

stringent enhanced I/M performance standard established for those areas that have an 

approved SIP for Rate of Progress (ROP) for 1996, and do not have a disapproved plan 

for ROP for the period after 1996 or a disapproved plan for attainment of the air quality 

standards for ozone or carbon monoxide.5

 

1

 40 C.F.R. §51.351.

2

 40 C.F.R. §51.351(g)(13).

3 60 Fed. Reg. 48029 (September 18, 1995).

4 On July 19, 1996, the USEPA also establishing an additional enhanced I/M performance 

standard for qualified areas in the Northeast Ozone Transport Region (OTR), often referred to 

as the OTR low enhanced performance standard. The emission reduction targets for the OTR 

low enhanced performance standard are less than both the low enhanced performance standard 

and the basic performance standard. The USEPA established two criteria that areas have to 

meet in order to be eligible for the OTR low enhanced performance standard: 1) the standard 

applies only in attainment areas, marginal ozone non-attainment areas and certain moderate 

ozone non-attainment areas with populations under 200,000 in an OTR and 2) the standard 

program must be supplemented by other measures in order to achieve emission reductions 

equal to or greater than that which would have occurred had a regular low enhanced I/M 

program been implemented. New Jersey did not meet the criteria to qualify for use of the OTR 

low enhanced performance standard.

5

40 C.F.R. §51.351(g).
3

New Jersey is currently demonstrating compliance with the Clean Air Act requirements 

for ROP and attainment and is therefore now only required to meet the “low” enhanced 

performance standard. The revised performance standard modeling included as part of 

this submittal is designed to show attainment of the low enhanced performance 

standard.

In accordance with the USEPA’s final rule for I/M requirements, a state must design 

and implement its enhanced I/M program such that it meets or exceeds, within +/- 0.02 

grams per mile (gpm)6, a minimum performance standard. The performance standard 

is expressed as average gpm emission levels from area-wide highway mobile sources 

as a result of the enhanced I/M program.7 Areas must meet the performance standard 

for the pollutants that cause them to be subject to the enhanced I/M requirements.8 

New Jersey was required to implement its enhanced I/M program because of its nonattainment status for two criteria air pollutants; ozone (of which volatile organic 

compounds (VOCs) and oxides of nitrogen (NOx) are precursors) and carbon 

monoxide. 

The USEPA’s final rule on I/M requirements also requires that the equivalency of the 

emission levels achieved by the State’s enhanced I/M program design compared to 

those of the performance standard must be demonstrated using the most current 

version of USEPA’s mobile source emission model.9 Currently, the latest version is 

MOBILE 6.2.03 (dated September 24, 2003), which was used for this analysis.

B. Modeling Parameters and Assumptions

Table 1 outlines the main program parameters of the low enhanced performance 

standard model program. In addition, this table presents New Jersey’s enhanced I/M 

program design for both the existing and proposed programs for evaluation year 2013. 

The emission factors were estimated for 2013 because it follows the expected 

implementation of the proposed enhanced I/M program. Although each state must 

model the performance standard using the parameters specified in Table 1, the 

performance standard emission factor results will vary for each state. This variation is 

the result of the use of state-specific inputs such as registration distribution and vehicle 

miles traveled (VMT) mix. Other local parameters, such as fuel type, add to state 

variations in determining the emission factors for the USEPA’s performance standard 

program.

 

6

40 C.F.R. §51.351(g)(13) allows for a margin of error of +/-0.02 gpm for each pollutant result. 

7

40 C.F.R. §51.351(a), 57 Fed. Reg. 52988 (November 5, 1992).

8

Ibid.

9

40 C.F.R.§51.351(d), 57 Fed. Reg. 52988, (November 5, 1992).
4

Table 1: Performance Standard and NJ Enhanced I/M Program Designs 

Program Element Low Enhanced

Performance Standard

New Jersey’s Existing 

Enhanced

I/M Program 

New Jersey’s 

Proposed Enhanced

I/M Program 

Network Type 100% centralized hybrid – 70% 

centralized/30%

decentralized

hybrid - 70% 

centralized/30%

decentralized

Credit Assumed for 

Decentralized 

Program

NA 80% 80%

Program Start Date 198311974 1974

Test Frequency annual biennial2biennial2

Emission Standards Those specified at 40 

C.F.R. Part 85, Subpart W

Initial ASM5015 exhaust 

emission standards

Two-Speed Idle 

Standards of 1.2% for 

carbon monoxide and 

220ppm for HC

Model Year (MY) 

Coverage

1968 and later MY all vehicles not specifically

exempt

all vehicles not 

specifically exempt

Vehicle Type 

Coverage

All light-duty gasolinefueled vehicles and trucks 

(up to 8,500 lbs. GVWR)

All gasoline-fueled vehicles 

and trucks (both light and 

heavy duty vehicles)

All gasoline-fueled 

vehicles and trucks 

(both light and heavy

duty vehicles)

Exhaust Emission 

Test

Idle - 1968-2050 MY OBD - 1996 and later MY 

beginning 6/1/03

ASM5015 – 1981-1995 MY 

amenable to dyno. testing

2500 RPM test – certain 

exempt vehicles and those 

1981 and newer MY not 

amenable to dyno. testing

Idle - pre-1981 and HDGVs

OBD - 1996 and later 

MY beginning 6/1/03

Two-Speed Idle – 1981-

1995 MY 

Idle - pre-1981 and 

HDGVs
5

Program Element Low Enhanced

Performance Standard

New Jersey’s Existing 

Enhanced

I/M Program 

New Jersey’s 

Proposed Enhanced

I/M Program 

Visual Inspections

Positive Crankcase 

Ventilation (PCV) valve --

1968 – 1971 MY inclusive

Exhaust Gas Recirculation 

(EGR) valve – 1972 and 

newer

Visual inspection of the 

catalytic converter, presence 

of a gas cap, and fuel inlet 

restrictor -- 1975 and newer 

(beginning calendar 1985)

Visual inspection of the 

catalytic converter, 

presence of a gas cap, 

and fuel inlet restrictor --

1975 and newer 

(beginning calendar 

1985)

Evaporative System 

Function Checks

N/A

Gas Cap Testing – 1971 and 

later vehicles3 (beginning 

calendar year 1998)

Gas Cap Testing – 1971

– 2000 MY inclusive3 

(beginning calendar year 

1998)

Pre- 1981 MY 

Stringency

20% 30% 30%

Waiver Rate 3% 3%40%

Compliance Rate 96% 98% 98%

Evaluation Date5January 1, 2002 January 1, 2013 January 1, 2013

On-Road Testing 0.5% of the subject vehicle 

population or 20,000 

vehicles (whichever is less)

0.5% of the subject vehicle 

population or 20,000 

vehicles (whichever is less)

0.5% of the subject 

vehicle population or 

20,000 vehicles 

(whichever is less)

1 For programs with existing I/M programs, like New Jersey’s basic I/M program.

2 Except for new vehicles of model year 2000 or later purchased after January 1, 2003. These vehicles are exempt from their 

first emission inspection for two inspection cycles (i.e., four years) and thereafter must be inspected biennially (or once every 

other year).

3 Only those pre-1981 vehicles that were equipped with sealed gas caps will be subject to the gas cap check. The State 

estimates that model year vehicles prior to 1970 were not equipped with a sealed gas cap.

4 The State assumed a zero percent waiver rate for pre-1981 vehicles as these vehicles are not eligible for a waiver based on 

the NJMVC inspection rules.

5 For all scenarios, summer season and temperatures were used for VOC/NOx evaluations, while winter season and 

temperatures were used for carbon monoxide evaluations.

The remainder of this section discusses in detail the various New Jersey program 

parameters used to model the existing and proposed enhanced I/M programs. The 

State has also included, in Appendices II and III of this document, the MOBILE6 input 

and output files and the spreadsheet that compiles the results. 
6

1. Network Type:

New Jersey’s enhanced I/M program is comprised of a hybrid network of both 

centralized test-only facilities and decentralized test-and-repair facilities. The State has 

assumed a 70/30 CIF/PIF split for its enhanced I/M network (that is, 70 percent of the 

vehicle owners are expected to pass inspection at a centralized inspection facility and 

the remaining 30 percent are expected to pass inspection at a decentralized private 

inspection facility). 

New Jersey claimed, in accordance with the flexibility afforded states by the NHSDA, 

that the decentralized portion of its enhanced I/M program would be 80 percent as 

effective as the centralized portion of its program.10 As part of its August 31, 2001 

enhanced I/M SIP revision submittal, New Jersey demonstrated that its private 

inspection network is achieving this 80 percent assessment. In fact, this analysis 

showed that the State was conservative in its initial 80 percent estimation. In addition, 

the effectiveness of the private inspection network may have increased further after the 

introduction of OBD testing. Therefore, New Jersey has assumed 80 percent credit for 

the decentralized portion of its program.

To address the State's inspection facility type split and the 80 percent credit for the 

decentralized portion of the program, the NJDEP calculated an overall I/M effectiveness 

rate. The I/M effectiveness rate was 94 percent (that is, 0.70 * 100 percent + 0.30 * 80 

percent). This rate was used as an input to the MOBILE6 model to account for New 

Jersey’s specific network type.

2. Start Date:

The I/M program start date is defined as the date on which vehicles were first inspected 

using an evaporative or tailpipe exhaust emission inspection in the State. As such, for 

New Jersey this date is 1974 (all modeling dates are assumed to be January 1 of the 

given year), the date when the State implemented its basic I/M program. Although this 

is New Jersey's start date as outlined in the low enhanced performance standard 

requirements, the NJDEP considers other programmatic start dates in determining the 

final emission factors associated with New Jersey's program. The State implemented 

its enhanced I/M program on December 13, 1999, which, for modeling purposes, is 

assumed to be January 1, 2000. As such, the January 1, 2000 date is assumed in 

modeling the enhanced portion of the State's program, while January 1, 1974 continues 

to be assumed for the basic (idle) portion of the State's program. Finally, the State 

assumed a January 1, 2004 start date for OBD implementation. 

 

10

 Revision to the State Implementation Plan (SIP) for the Control of Mobile Source Ozone Air 

Pollution--Enhanced Inspection and Maintenance (I/M) Program, March 27, 1996, Section 3, 

Network Type and Program Evaluation, pages 14-15.
7

3. Test Frequency:

The current test frequency of New Jersey’s enhanced I/M program is biennial (that is, 

vehicle inspections are required once every two years). In addition, starting on January 

1, 2003, New Jersey implemented a 4-year new vehicle exemption. The 4-year new 

vehicle exemption was modeling as a grace period with the age of vehicles first subject 

to mandatory I/M program requirements set to 4.

4. Model Year and Vehicle Type Coverage:

Vehicles currently receive different types of emission tests, depending on the type and 

model year of the vehicle. Pre-1981 vehicles are given an idle exhaust emission test. 

Currently, model year 1981-1995 vehicles which are: 1) classified as light-duty gasolinefueled motor vehicles (LDGVs), or light-duty gasoline-fueled trucks 1 and 2 (LDGT1s 

and LDGT2s)11, 2) amenable to dynamometer-based testing, and 2) not specifically 

exempted12 from enhanced testing, are subjected to the ASM5015 exhaust emission 

test. Those model year 1981-1995 vehicles that are not amenable to dynamometer 

testing currently receive a 2500 RPM test. All 1996 and newer vehicles receive an OBD 

inspection unless they are exempt from that test in which case they receive the 

applicable exhaust emission test. 

New Jersey has proposed numerous changes to its enhanced I/M program to be fully 

implemented by 2012. These changes include the replacement of the ASM5015 and 

2500 RPM tailpipe tests with the two-speed idle (TSI) tailpipe test. Also repair cost 

waiver provisions have been removed and gas cap testing is excluded for vehicles of 

model year 2001 and newer. Another proposed program change requires certain 

classes of commercial vehicles, limousines, taxis and jitneys to receive annual (more 

frequent) inspection. In addition, although it is not modeled by MOBILE6, it is proposed 

that light duty diesel vehicles will be subject to emission testing. As part of the 

documentation of the rule changes, the Department estimated emission reduction 

benefits of 49 tons per year of VOC + NOX for the extension of the I/M program to light 

duty diesel vehicles. Details regarding these estimated emission reduction benefits are 

provided in Appendix II. 

 

11

 To determine whether a vehicles is classified as a LDGV, LDGT1, LDGT2, or HDGV, please 

refer to the definition section of either of the NJDEP’s rules for the implementation of the 

enhanced I/M program at N.J.A.C. 7:27-15.1 and N.J.A.C. 7:27B-4.1.

12 Specifically exempted vehicles are those vehicles which have been exempted from enhanced 

emission testing, or alternatively, from emission testing all together, through NJMVC regulations 

and statute. These vehicles include collector motor vehicles, low mileage vehicles, and historic 

motor vehicles.
8

Table 2 (in Section B.5) shows each vehicle category and the applicable OBD, exhaust 

and/or evaporative emission tests to which that vehicle category is subjected for both 

the existing and proposed enhanced I/M programs. 

 

5. Exhaust Emission Test Type:

The majority of gasoline-fueled motor vehicles inspected as part of the enhanced I/M 

program currently receive either an OBD inspection or an ASM5015 exhaust emission 

test. Table 2 outlines the different vehicle categories and the applicable tests for those 

categories.
9

Table 2: Various Vehicle Categories and Applicable Emission Tests

Vehicle Category Exhaust Emission Test Evaporative Emission Test(s)

NJ Existing 

Enhanced 

Program

NJ Proposed 

Enhanced 

Program

NJ Existing 

Enhanced 

Program

NJ Proposed 

Enhanced 

Program

pre-1981 vehicles idle idle gas cap test only1gas cap test only1

1981-1995 

ASM50152TSI gas cap test only gas cap test only

1981-1995 vehicles 

not amenable to 

dynamometer-based 

testing

2500 RPM TSI gas cap test only gas cap test only

1981-1995 low 

mileage vehicles32500 RPM TSI gas cap test only gas cap test only

1996 -2000 low 

mileage vehicles3 OBD OBD OBD and gas cap 

test4

OBD and gas cap 

test4

2001 and newer low 

mileage vehicles3 OBD OBD OBD and gas cap 

test4

OBD 

1996-2000 vehicles

OBD OBD OBD and gas cap 

test4

OBD and gas cap 

test4

2001 and later 

vehicles OBD OBD OBD and gas cap 

test4

OBD 

collector motor 

vehicles5exempt exempt exempt exempt

historic motor 

vehicles exempt exempt exempt exempt

1981 and newer 

vehicles registered 

as school buses6

OBD OBD OBD and gas cap 

test4

OBD and gas cap 

test4

1

 Only those pre-1981 vehicles that were equipped with sealed gas caps will be subject to the gas cap 

check. The State estimates that model year vehicles prior to 1970 were not equipped with a sealed gas 

cap.

2 Unless the vehicle is not amenable to dynamometer-based testing or is specifically exempt.

3

The “low mileage vehicle” category, as required by the enhanced I/M legislation, is defined and 

discussed at P.L. 1995, Chapter 112, Section39:8-2b.(1), approved June 2, 1995. The “low mileage 

vehicle” category is being removed in the proposed enhanced I/M program because there will no longer be

a difference in the test requirements between low mileage and non-low mileage vehicles for each model 

year. 
10

4

The OBD test includes checks for monitored failures of both the exhaust and evaporative systems,

thereby substituting for traditional tailpipe and evaporative pressure and purge tests. In addition to these 

checks, the State will also perform a traditional gas cap pressurization inspection on these vehicles.

5

The “collector motor vehicle” category, as required by the enhanced I/M legislation, is defined and 

discussed at P.L. 1995, Chapter 112, Section39:8-1a., approved June 2, 1995.

6 All gasoline-fueled vehicles registered as school buses in the State are inspected by the NJMVC's 

School Bus Inspection Unit. If applicable, these vehicles receive an OBD test. School buses not 

amenable to an OBD test will receive the 2500 RPM tailpipe test instead of the ASM5015 tailpipe test 

under the proposed program. 

As part of its last performance standard modeling submittal, the State estimated the 

number of vehicles that would be exempt from the ASM5015 exhaust emission test 

because they were not amenable to dynamometer testing (i.e., either vehicles which 

employ full-time, four-wheel drive or which are installed with non-switchable traction 

control). This estimation (10%) was then used to determine the loss in credit attributed 

to these vehicles receiving a 2500 RPM test in lieu of the ASM5015 exhaust emission 

test. In 2013 the number of vehicles that would be exempt from the ASM5015 exhaust 

emission test will be extremely small because the vast majority of the vehicles will be 

receiving OBD testing. Therefore for the 2013 model runs that represent the existing 

program it is no longer necessary to perform a separate set of runs to model the loss in 

credit for these vehicles. This will no longer be an issue for the model runs that 

represent the proposed enhanced I/M program because the ASM5015 test is being 

eliminated. 

The NJMVC’s regulations and State statute specifically exempt several types of 

vehicles that would otherwise be subjected to enhanced I/M testing from the enhanced 

tests or from emission testing as a whole. These vehicles include: 1) low mileage 

vehicles, and 2) collector motor vehicles. To determine whether or not a vehicle 

qualifies for either of these categories, see the NJMVC’s definitions at N.J.A.C. 13:20-

43.1. Note that the low mileage vehicle category is being removed in the proposed 

program because there will no longer be a difference in the test requirements between 

low mileage and non-low mileage vehicles for each model year. 

In addition, the NJMVC’s regulations maintain a vehicle category that exempts 

applicable vehicles from basic I/M emission testing. These vehicles are classified by 

the NJMVC as historic motor vehicles. To determine whether or not a vehicle qualifies 

as a historic motor vehicle, see the NJMVC’s definitions at N.J.A.C. 13:20-43.1 and 

N.J.S.A. 39:3-27.3. The NJDEP did not include these vehicles as part of this revised 

performance standard modeling for two reasons: (1) the number of vehicles in these 

categories was so small that their emissions were not significant enough to impact the 

modeling, and (2) the vehicles in the category, by definition, fell well outside the 25 

model year analysis window examined by the MOBILE model. 
11

6. Emission Control Device Inspections:

A visual inspection to determine the presence of a catalytic converter is performed on 

all 1975 and newer motor vehicles. This was assumed in the State’s revised 

performance standard modeling. In addition, the State assumed that all vehicles 

subject to the gas cap inspection also receive a visual gas cap inspection for the 

presence of a cap and to examine the cap for any cracks, outside damage, etc. Finally, 

the State included in its revised performance standard modeling fuel inlet restrictor 

testing for all applicable model years. The purpose of the fuel inlet restrictor test is to 

determine whether or not a leaded gasoline pump nozzle could fit into the vehicle’s 

gasoline inlet, allowing for the possibility of leaded gasoline usage. Use of leaded 

gasoline interferes with effectiveness of the vehicle’s catalytic converter. Although the 

State began fuel inlet restrictor testing as part of its annual inspections in June 1990, 

New Jersey stopped performing inlet restrictor tests in 1994 because it was no longer 

possible for New Jersey motorists to obtain leaded gasoline. However, according to a 

USEPA guidance memorandum on highway source modeling13, states that have, in the 

past, performed fuel inlet tests for at least one full cycle (and have required catalyst 

replacement upon failure) may claim the SIP credit associated with this testing without 

future testing. Since New Jersey meets these requirements, the State took emission 

credit for the fuel inlet restrictor test in this revised performance standard modeling. 

7. Evaporative System Function Checks: 

In addition to outlining the exhaust emission tests applicable to each vehicle category, 

Table 2 also shows which vehicle categories are currently subject to the State’s 

evaporative emission tests. Although OBD monitors a vehicle's evaporative system, and 

as such has a "self-contained" evaporative functional check, the USEPA has 

recommended that states needing significant hydrocarbon reductions to meet their 

attainment goals should supplement OBD-I/M testing with a separate gas cap 

inspection.14 This recommendation is based on the fact that when the USEPA 

compared failure rates for the evaporative portion of the OBD-I/M test to the failure rate 

for the stand-alone gas cap test, they found that the separate gas cap test was able to 

identify a substantial number of leaking gas caps that were not identified by the OBD 

monitors due to the different failure thresholds. For the proposed I/M program the gas 

cap applicability is amended to exclude vehicles of model year 2001 and newer. This is 

because by model year 2001 the vehicle manufacturers had refined their OBD systems 

to more reliably detect evaporative system malfunctions and tighter evaporative 

emission tests were imposed by the USEPA. 

 

13

 Memorandum dated September 16, 1994 from Phil Lorang, then Director of the Emission 

Planning and Strategies Division, USEPA to All Regional Air Directors entitled “Discontinuation

of Tail Pipe Lead and Fuel Inlet Tests.”

14 "Performing Onboard Diagnostic System Checks as Part of a Vehicle Inspection and 

Maintenance Program", EPA420-R-01015, June 2001.
12

The pressurized gas cap inspection is designed to insure that the gas cap seals 

properly and has no leaks. In the existing I/M program all gasoline-fueled motor vehicle 

manufactured with a sealed gas cap are subject to this pressured gas cap inspection, 

which the NJDEP determined is all 1971 and later vehicles. 

8. Stringency:

For modeling purposes, a 30 percent emission test failure rate was assumed for pre1981 vehicles. 

9. Waiver Rate:

In accordance with 40 C.F. R. 51.360(d)(1), each state’s SIP must include “a maximum 

waiver rate expressed as a percentage of initially failed vehicles.” The purpose of this 

waiver rate is to estimate emission reduction benefits in a modeling analysis. In the 

USEPA enhanced low I/M performance standard, a 3 percent waiver rate was used. 

Using this 3 percent assumption as guidance for its own enhanced I/M program, New 

Jersey assumed a 3 percent waiver rate for 1981 and newer vehicles in its enhanced 

I/M SIP. 

It should be noted here that under New Jersey’s existing enhanced I/M program, any 

vehicle that applies for a waiver must show compliance with the idle test, in addition to 

meeting the minimum cost expenditure. Since all pre-1981 vehicles receive the idle test 

as their official inspection test under the enhanced I/M program, these vehicles are not 

eligible for a waiver. Thus, the pre-1981 waiver rate is assumed to be zero. In addition, 

the State extended the waiver option to those vehicles failing an OBD inspection, in 

addition to those failing an ASM5015 exhaust emission test, so long as they meet the 

minimum cost expenditure and pass an idle exhaust emission test. 

The proposed enhanced I/M program has removed the option for vehicles to comply 

with emission standards by receiving a waiver. Waiver rates are zero for all vehicles in 

the proposed I/M program.

10. Compliance Rate:

For modeling purposes, a 98 percent compliance rate was assumed for the overall 

enhanced I/M program.
13

11. Evaluation Date:

An evaluation date of January 1, 2002 is used for the performance standard runs.

15 An 

evaluation date of January 1, 2013 is used for the program evaluation runs because the 

proposed I/M program should be fully implemented by this date.

 

15 40 C.F.R. §51.351(g)(13).

In addition to the parameters and assumptions discussed previously in Subsection B, 

the NJDEP had to make other assumptions in order to complete its performance 

standard and program evaluation modeling. The following table shows what those 

assumptions were and what values where used to complete the modeling:

Table 3: Other Modeling Assumptions

Modeling Parameters Value Used for 

Average Summer 

Runs 

(VOC and NOx)

Value Used for 

Average 

Winter Runs 

(Carbon 

Monoxide)

Maximum Temperature (F) 82.9 41.2

Minimum Temperature (F) 66.3 26.7

Absolute Humidity (grains/pound) 85.59 20.00

Speed MOBILE6 Defaults MOBILE6 Defaults

Mechanic Training and Certification yes - 100% yes - 100%

NJ Low Emission Vehicle Program 

w/o ZEV Mandate 

yes yes

Gasoline RVP (psi) 6.8 15

Oxygenated Gasoline 10% Ethanol 10% Ethanol

C. Modeling Results:

The following table shows the emission factors (in grams per mile) obtained for the 

USEPA performance standard program, New Jersey’s existing enhanced I/M program,

and New Jersey’s proposed enhanced I/M program for VOC, NOx and carbon 

monoxide, respectively. Modeling files are provided in Appendix III and the modeling 

results are summarized in Appendix IV.
14

Table 4: Modeling Results

Program Type VOC (gpm) NOx (gpm) Carbon 

Monoxide (gpm)

USEPA Low Enhanced 

Performance Standard

(2002)

0.903 - 0.943* 2.376 - 2.416* 21.834 - 21.874*

New Jersey Existing 

Enhanced I/M Program

(2013)

0.349 0.687 10.045

New Jersey Proposed 

Enhanced I/M Program

(2013)

0.348 0.688 10.025

* The performance standard values are expressed as a range to account for the +/- 0.02 

gpm margin for error allowed for by the USEPA. Therefore, the standards are met so long as they fall 

below the upper limit of the range.

IV. Conclusion

As shown in Table 4, the model results indicate that there is no significant difference 

between emission factors for New Jersey’s existing and proposed enhanced I/M 

programs for ozone precursors (VOCs and NOx). 

A slight increase in the emission factor for NOx is offset by a slight decrease in the 

emission factor for VOCs although the magnitude of the increases and decreases are 

well below the USEPA margin of error of +/- 0.02 gpm. In addition, the emission factors 

calculated for New Jersey’s proposed enhanced I/M program do not reflect the 

emission reductions associated with the addition of light duty diesel vehicles to New 

Jersey’s I/M program. As part of the documentation of the rule changes, the 

Department estimated emission reduction benefits of 49 tons per year of VOC + NOX

for the extension of the I/M program to light duty diesel vehicles. 

 

The proposed enhanced I/M program provides a small reduction in the predicted 

carbon monoxide emission factor relative to the existing enhanced I/M program.

This demonstrates that the proposed changes to the enhanced I/M program do not 

compromise the State’s efforts to meet and/or maintain National Ambient Air Quality 

Standards (NAAQSs) for ozone or carbon monoxide. Also, as shown in Table 4, the 

State's proposed enhanced I/M program meets the USEPA low enhanced performance 

standard.