Methodology for Calculating 

LEVII Program Benefits in Pennsylvania

Technical Support Document

March 2007

 Prepared for:

Mobile Sources Section, Bureau of Air Quality

Pennsylvania Department of Environmental Protection

PO Box 8468

Harrisburg, PA 17105-8468

 Prepared by:

Michael Baker, Jr., Inc.

1304 Concourse Drive

Linthicum, MD 21090

410-689-3400
Methodology for Calculating LEVII Program Benefits in Pennsylvania

March 2007

Table of Contents

INTRODUCTION .......................................................................................................................................................1

EMISSION CALCULATION METHODOLOGY.................................................................................................................1

METHODOLOGY FOR ESTIMATING LEVII PROGRAM CREDITS ..................................................................................3

INVENTORY SUBMISSION MATERIALS .......................................................................................................................3

EMISSION DATA SOURCES AND ANALYSIS TOOLS......................................................................................4

ANALYSIS TOOLS ......................................................................................................................................................4

TRAFFIC DATA SOURCE/FLEET DATA INPUTS ...........................................................................................................4

TRAFFIC GROWTH ASSUMPTIONS..............................................................................................................................5

I/M AND FUEL PARAMETERS .....................................................................................................................................5

WEATHER DATA........................................................................................................................................................5

OTHER INPUTS...........................................................................................................................................................6

ESTIMATING LEVII PROGRAM CREDITS ........................................................................................................6

SUMMARY OF TECHNICAL DATA FILES .....................................................................................................................7

CALCULATION OF LEVII PROGRAM BENEFITS ..........................................................................................................8

RESOURCES...............................................................................................................................................................9

List of Tables

TABLE 1: SUMMARY OF APPENDICES............................................................................................................................3

TABLE 2: SUMMARY OF INVENTORY ANALYSIS TOOLS ................................................................................................4

TABLE 3: LEVII TECHNICAL DATA INPUT FILES...........................................................................................................7

TABLE 4: IMPACT OF THE PENNSYLVANIA CLEAN VEHICLES PROGRAM VS FEDERAL TIER2 PROGRAM........................8

Summary of Appendices

Appendix 1: Mobile Source Highway Emissions Inventory – An Explanation of Methodology

Appendix 2: MOBILE6.2 Input Parameter Summary

Appendix 3: MOBILE6.2 LEVII Technical Data Input Files

Appendix 4: Sample MOBILE6.2 Input File

Appendix 5: Ozone Modeling Results and LEVII Benefits
1

INTRODUCTION

In 1998, Pennsylvania promulgated the New Motor Vehicle Emissions Control Program (25 Pa. Code 

Chapter 126, Subchapter D). This program created the Pennsylvania Clean Vehicles (PCV) Program that 

beginning in model year (MY) 2006 required new light-duty highway motor vehicles offered for sale 

within Pennsylvania to be certified by the California Air Resources Board (CARB) under that Board’s 

Low Emitting Vehicle (LEV) program. The Pennsylvania Clean Vehicles Program does not require the 

California Zero Emitting Vehicle (ZEV) requirement. In December 2006, Pennsylvania promulgated 

amendments to the PCV program that:

 Postponed the compliance date from MY 2006 to MY 2008,

 Updated program definitions in 25 Pa. Code Chapter 121, § 121.1 (relating to definitions),

 Makes program regulatory clarifications, and

 Provides a transition mechanism for compliance with the program. 

This document provides estimates of the potential LEVII program benefits within the state and 

summarizes the methodology used to calculate emissions. The document provides future year projections 

of mobile (highway) vehicle miles of travel (VMT) and emissions (ozone precursors VOC and NOx) for 

the years 2010, 2015, 2020, and 2025. 

Emission Calculation Methodology 

Technical guidance documents from EPA were used in the development of base and future year emissions 

inventories to support the analyses of potential LEVII program benefits in Pennsylvania. They include:

 Policy Guidance on the Use of MOBILE6 for SIP Development ad Transportation Conformity, 

US EPA Office of Air and Radiation, dated January 18, 2002.

 Technical Guidance on the Use of MOBILE6 for Emission Inventory Preparation, US EPA 

Office of Air and Radiation, and Office of Transportation and Air Quality, dated January 2002, 

revised February 2, 2005.

 User’s Guide to MOBILE 6.1 and MOBILE6.2, Mobile Source Emission Factor Model, EPA420-

R-02-028, dated October 2002.

Mobile source emission factors were calculated using EPA’s MOBILE6.2 emission model. The 

methodologies used to produce the emission results conform to the recommendations provided in EPA’s 

Technical Guidance. A mix of local data and national default (internal to MOBILE6.2) data has been 

used for this submission. Local data has been used for the primary data items that have a significant 

impact on emissions. These include:

 VMT and speeds

 Vehicle type mixes

 Vehicle age distributions 

 Hourly distributions 

 Temperatures/humidity 

 Inspection/Maintenance parameters 

 Fuel program characteristics. 
2

For this analysis, local data inputs reflect the latest planning assumptions at the time of the analysis 

(based on 2002 data). These include current assumptions on control strategies (e.g. InspectionMaintenance programs) and fuel characteristics. The analysis methodology is consistent with the 2002 

National Emissions Inventory (NEI) submission. A detailed methodology is provided in Appendix 1. 
3

Methodology for Estimating LEVII Program Credits 

The emission benefits of the Pennsylvania Clean Vehicles Program have been calculated using the 

assumptions and data files documented in EPA’s June 5, 2002 guidance entitled, “Modeling Alternative 

NLEV Implementation and Adoption of California Standards in MOBILE6” and the ‘Technical Guidance 

on the Use of MOBILE6 for Emissions Inventory Preparation”. Several key revisions to the EPA 

guidance assumptions were needed to reflect the program to be implemented in Pennsylvania. The 

revisions include the removal of the zero-emitting exhaust vehicle (ZEV) component of the program and 

a revised phase-in start date of 2008 (EPA guidance assumptions are based on a 2004 start date).

Inventory Submission Materials 

To complement this document, attachments have been provided with additional detail regarding the 

analysis methodology, the MOBILE6.2 input parameters, and the output emission results for the counties 

in Pennsylvania. These include:

Table 1: Summary of Appendices

Appendix Title Description

1

Mobile Source Highway 

Emissions Inventory –

An Explanation of 

Methodology

Provides summary of methodology used to calculate 

the VMT and emissions.

 2

MOBILE6.2 Input 

Parameter Summary

Provides summary of input parameters related to traffic 

data sources, fuel, weather, I/M, and other MOBILE6.2 

related parameters.

3

MOBILE6.2 LEVII 

Input Files

Provides phase-in percentages and exhaust certification 

bin standards used to reflect LEVII program

4

MOBILE6.2 Sample 

Input File Provides example of MOBILE6.2 input files.

5

Pennsylvania ozone 

(VOC, NOx) Emission 

Results (By County, Year)

Provides county emissions for a summer weekday in 

2010, 2015, 2020, 2025

(Results included for 2004, 2006, 2009 LEVII start date)

(2008 start date results interpolated)
4

EMISSION DATA SOURCES AND ANALYSIS TOOLS 

This section provides a summary of the input data and analysis tools used to evaluate the potential 

emission benefits of the Pennsylvania Clean Vehicles Program. The key elements to the modeling 

protocol are described in the sections below. A more detailed description of the analysis process and 

tools is provided in the methodology report in Appendix 1. 

Analysis Tools 

The statewide emissions analysis utilizes several key software/programs for producing the county 

emissions totals. These tools are outlined in Table 2.

Table 2: Summary of Inventory Analysis Tools

Tool Purpose

MOBILE6.2 Produces emission factors for each pollutant in 

grams/mile for VOC and NOx

PPSUITE

Processes the highway data, Calculates hourly 

congested speeds for each state roadway 

segment, Prepares MOBILE6.2 input files, 

Processes MOBILE6.2 output files

The statewide inventory reflects the highway mobile source emission estimations using EPA’s 

MOBILE6.2 emission model. PPSUITE represents an enhanced version of the Post Processor for Air 

Quality (PPAQ) software system that has been used for previous inventory and conformity submissions in 

Pennsylvania. The software has undergone significant revisions to ensure consistency with the 

MOBILE6.2 emissions model. PPSUITE plays a key role in the development of hourly roadway speed 

estimates, which are supplied as input to the MOBILE6.2 model. The software is also used to prepare the 

MOBILE6.2 input shell and to process the MOBILE6.2 outputs. 

Traffic Data Source/Fleet Data Inputs 

The 2002 PENNDOT Roadway Management System (RMS) data serves as the primary highway data 

source for the county and functional class VMT estimates. The data source provides a “snapshot” of the 

regional roadway system and volumes in 2002. The data includes the 2002 average annual daily traffic 

volumes for all state roadways in Pennsylvania. To account for additional local roadway VMT and to 

ensure consistency with reported HPMS totals, the 2002 VMT totals are adjusted to match the 2002 

HPMS VMT totals reported to FHWA. 

Based on the requirements for ozone inventories, traffic volumes on each RMS roadway segment must be 

adjusted to a summer weekday. The daily and monthly seasonal factors are developed from data 

contained in the document, 2002 Pennsylvania Traffic Data, as prepared by PennDOT’s Bureau of 

Planning and Research. The seasonal and daily factors provided in this document are based on statistical 

analyses of 2002 traffic counts taken at permanent and in-pavement ATR (automatic traffic recorder) 

locations throughout the state. Based on these seasonal traffic volumes, the PPSUITE software calculates 

unique congested speeds for each roadway segment during an ozone summer weekday scenario.
5

PPSUITE calculates congested speeds by hour of the day for each roadway segment and provides the 

information as input to the MOBILE6.2 software. To disaggregate the daily RMS volumes to hourly 

volumes, auto and truck hourly pattern data from PennDOT’s 2002 Pennsylvania Traffic Data report are 

used to determine the temporal variations in traffic volumes.

Vehicle mix patterns are calculated for each county and functional class grouping utilizing a combination 

of 2002 RMS truck percentages and MOBILE6.2 default vehicle mix distributions. The development of 

vehicle type pattern data input to the MOBILE6.2 software is described in more detail in Appendix 1. 

The distribution of vehicles to fuel type (diesel, gas) is determined from the MOBILE6.2 default diesel 

sales fractions.

Vehicle age distributions are input to MOBILE6.2 for each county based on registered vehicles that 

reflect July 1 summer conditions. These distributions reflect the percentage of vehicles in the fleet up to 

25 years old and are listed by the 16 composite MOBILE6 vehicle types. 2002 vehicle age distributions 

have been used for this inventory from the PennDOT Bureau of Motor Vehicles Registration Database. 

Due to insufficient data, only data for light-duty vehicles are used as local inputs. The heavy-duty 

vehicles use the internal MOBILE6.2 defaults.

Traffic Growth Assumptions 

Traffic growth forecasting plays a pivotal role in estimating future year emissions for the region. This 

inventory utilizes county-specific growth rates, as used for past conformity and inventory submissions, 

based on an extrapolation of historic HPMS VMT growth trends. The growth rates were originally shared 

between PennDOT, PaDEP, and other Interagency Consultation Group members, including the PA 

Conformity Work Group (which includes EPA, FHWA, and representatives from larger MPOs within the 

state).

I/M and Fuel Parameters 

The Inspection Maintenance (I/M) program inputs to the MOBILE6.2 model are based on current 

programs within the county. The Pennsylvania inspection and maintenance (I/M) program was upgraded 

and expanded throughout the state with a phase-in period starting in December 2003 and fully

implemented by June 2004. The program test requirements vary by region and include on-board 

diagnostics (OBD) technology that uses the vehicle’s computer for model years 1996 and newer to 

download potential engine problems that could effect emissions. The program, named PAOBDII, is 

implemented in the Philadelphia, Pittsburgh, and South Central / Lehigh Valley Regions. The Northern 

Region receives gas cap and visual inspections and the other 42 counties in the Commonwealth receive a 

visual inspection. Vehicles subject to the program include 1975 and newer model year gasoline cars and 

light duty trucks up to 9,000 pounds GVW. New model years are exempt for the first year. The county 

of registration determines which inspections are required. 

The summer weekday RVP values are consistent with values used for past inventory efforts. These 

assumptions, as well as the I/M program and fuel parameters, are summarized in Appendix 2 and 4.

Weather Data 

Weather information is based on information obtained from the National Climatic Data Center to 

calculate the minimum and maximum temperatures and absolute humidity data inputs to the 

MOBILE6.2 model. These assumptions are consistent with the 2002 NEI inventory submission. 
6

Other weather data required by MOBILE6.2 are assumed as the program defaults. These include 

the cloud cover, peak sun, and sunrise/sunset options. 

Other Inputs 

Federal vehicle emissions control and fuel programs are incorporated into the MOBILE6.2 software. The 

programs include:

 The Federal Motor Vehicle Control Program (FMVCP) including the National Low Emission 

Vehicle Program (NLEV) and federal Tier II / Low Sulfur Fuel Program;

 Emissions standards for medium and heavy duty vehicles in 2002, 2004 and 2007;

 Stage II and Onboard Refueling Vapor Recovery (ORVR).

Note: Pennsylvania considers emissions from refueling operations an area source category. While 

MOBILE6.2 is employed to calculate emissions factors for that source category, refueling emissions are 

not included in highway vehicle emissions estimations.

For analyses used to determine benefits related to the Pennsylvania Clean Vehicles Program, 

modifications were made to the federal vehicle control assumptions in MOBILE6.2. The input 

parameters were revised according to EPA guidance as discussed in the following sections.

ESTIMATING LEVII PROGRAM CREDITS 

The emission benefits of the Pennsylvania Clean Vehicles Program have been calculated using the 

assumptions and data files documented in EPA’s June 5, 2002 guidance entitled, “Modeling Alternative 

NLEV Implementation and Adoption of California Standards in MOBILE6”. 

EPA’s guidance provides key assumptions used to model the LEVII program impacts including:

 CARB LEVII phase-in schedules

 LEVII exhaust emission certification bin standards

 Methods for treatment of PZEV, AT-PZEV evaporative emissions

The calculations of LEVII benefits are determined by comparisons to a base-case, which is considered the 

Tier2 federal program. MOBILE6.2 assumes the default Tier2 phase-in schedule as estimated and 

prepared by EPA. This phase-in schedule is automatically applied within MOBILE6.2 applications. 

Assumptions must also be made for the sales of future vehicles under California’s LEVII program. The 

analysis uses the CARB LEVII phase-in percentages for passenger cars and light-duty trucks as presented 

in EPA’s June 2002 guidance (Tables A-1 to A-3). The phase-in percentages are based on a 2004 

program start date. Since the Pennsylvania Clean Vehicles Program will start in 2008, alternative LEVII 

phase-in percentages have been developed for these analyses. Note that Pennsylvania’s program will not 

include California’s ZEV mandate, thus those phase-in assumptions are not used for the analysis.

The LEVII program may include significant sales of PZEV and AT-PZEV type vehicles. Under the ZEV 

mandate, such vehicles must produce “near-zero” evaporative emissions. As indicated in EPA’s June 

2002 Guidance, the MOBILE6 model can only produce evaporative emissions for the following 

conditions:
7

 Zero evaporative emissions consistent with Pure ZEV vehicles

 Evaporative emissions equivalent to LEVII/Tier2 vehicles

In reality, the PZEV and AT-PZEV evaporative emissions fall somewhere between these two options. 

The EPA June 2002 Guidance recommends an approach that assumes that such vehicles produce 

evaporative emissions consistent with LEVII vehicles. 

Summary of Technical Data Files 

EPA’s June 2002 guidance provides the key input data needed to reflect the impacts of the California 

LEVII program. Table 3 summarizes the files used for Pennsylvania’s analyses, including the revisions 

and modifications made to each EPA file. Appendix 3 provides a printout of the technical data files used 

in the analyses.

Technical data files were developed and applied for alternative LEVII program start dates including 2004, 

2006, and 2009. The files provided by EPA were used directly for the 2004 program start date 

calculations; however, EPA’s LEVII94.D file was not used since the Pennsylvania Clean Vehicles 

Program does not include California’s ZEV mandate.

Table 3: LEVII Technical Data Input Files

MOBILE6 

Command

EPA Guidance 

Input Data File Description Modifications for Pennsylvania Analysis

T2 

EXH 

PHASE-IN

LEVIIPH.D

CARB LEVII Phase-in 

percentages by exhaust 

certification bin for model 

years 2004-2015

Files created for alternative 

program start dates:

2004 start date:

Use EPA file directly – No Modification

2006 start date: Create pal2exh.06*

Combination of M6 Tier2 defaults from T2EXH.D file for 

years 2004, 2005 and LEVII standards from LEVIIPH.D for 

years 2006 and above

2009 start date: Create pal2exh.09*

Combination of M6 Tier2 defaults from T2EXH.D file for 

years 2004-2008 and LEVII standards from LEVIIPH.D for 

years 2009 and above

T2

CERT LEVIIST.D CARB LEVII exhaust 

certification bins Use EPA file directly – No Modification

T2 

EVAP 

PHASE-IN

LEVIIEVP.D

CARB LEVII phase-in 

percentages for evaporative 

standards for model years 

2004 and up

Files created for alternative 

program start dates:

2004 start date:

Use EPA file directly – No Modification

2006 start date: Create pal2evp.06*

Combination of M6 Tier2 defaults from T2EVAP.D file for 

years 2004, 2005 and LEVII standards from LEVIIEVP.D for 

years 2006 and above

2009 start date: Create pal2exh.09*

Combination of M6 Tier2 defaults from T2EVAP.D file for 

years 2004-2008 and LEVII standards from LEVIIEVP.D for 

years 2009 and above

94+ 

LDG 

IMP

LEVII94.D

For model years 2004-2025 

used only to establish 

fraction of zero-emitting 

exhaust vehicles (ZEVs)

Use NLEVNE.D for all scenarios since Pennsylvania program 

does not have ZEV mandate

* Due to difference in Tier2 and LEVII bin definitions and the need to combine into one file, phase-in percentages 

were moved to different bin numbers to ensure correct vehicle standard representation
8

Calculation of LEVII Program Benefits 

Analyses were conducted to identify the potential emission impacts of adopting the California LEVII 

program in Pennsylvania. The analyses provided in this memo focus on the ozone precursors VOC and 

NOx. The analyses were conducted before Pennsylvania agreed upon the 2008 program start date and 

were completed for 2004, 2006 and 2009 alternative program start dates. For this submission, 2008 

LEVII emissions and benefits are determined by simple straight line interpolation between the 2006 and 

2009 start date alternative runs.

Appendix 5 provides the emission tables for each alternative start date as well as the emission impacts for 

2010, 2015, 2020, and 2025. Table 4 provides the benefits of the Pennsylvania Clean Vehicles Program 

(with 2008 start date and no ZEV mandate) as compared to the existing federal Tier2 program. The table 

illustrates emission benefits in tons/day. 

Table 4: Impact of the Pennsylvania Clean Vehicles Program vs Federal Tier2 Program

Statewide 

Results

2010 2015 2020 2025

VOC NOx VOC NOx VOC NOx VOC NOx 

Emission 

Benefits 

(tons/day)

-0.93 -0.97 -2.74 -3.52 -5.63 -6.79 -7.81 -9.13 

* Negative values indicate emission benefits over Tier2 Program
9

RESOURCES 

Draft Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National 

Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations, EPA, June, 2003

Consolidated Emissions Reporting, Federal Register, June 10, 2002

2002 Pennsylvania Traffic Data, PENNDOT Bureau of Planning and Research, 2002. 

User’s Guide to MOBILE6.1 and MOBILE6.2, Mobile Source Emission Factor Model, EPA420-R-02-

028, dated October 2002.

Technical Guidance on the Use of MOBILE6 for Emission Inventory Preparation, US EPA Office of 

Transportation and Air Quality, January 2002.

Policy Guidance on the Use of MOBILE6 for Emission Inventory Preparation, US EPA Office of Air and 

Radiation, January 18, 2002.

Modeling Alternative NLEV Implementation and Adoption of California Standards in MOBILE6, EPA, 

June 5, 2002, revised February 2, 2005.