APPENDIX E 

Philadelphia, PA portion of the Philadelphia-Wilmington, PA-NJ-DE
Nonattainment Area: 

Emissions Inventory for the PM2.5 NAAQS

Technical Support Document

Mobile Source Highway Emissions Inventory

Executive Summary

                                                       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





July 2009

 Philadelphia, PA portion of the Philadelphia-Wilmington, PA-NJ-DE
Nonattainment Area: Mobile Source Emissions Inventory

Executive Summary

July 2009

Table of Contents

  TOC \o "1-4"  INTRODUCTION	  PAGEREF _Toc126628300 \h  1 

Methodology	  PAGEREF _Toc126628301 \h  1 

Inventory Submission Materials	  PAGEREF _Toc126628302 \h  2 

DATA SOURCES AND ANALYSIS TOOLS	  PAGEREF _Toc126628303 \h  3 

Analysis Tools	  PAGEREF _Toc126628304 \h  3 

Traffic Data Source/Fleet Data Inputs	  PAGEREF _Toc126628305 \h  4 

Traffic Growth Assumptions	  PAGEREF _Toc126628306 \h  4 

I/M and Fuel Parameters	  PAGEREF _Toc126628307 \h  6 

Weather Data	  PAGEREF _Toc126628308 \h  7 

Other Inputs	8

RESOURCES	  PAGEREF _Toc126628310 \h  9 

 

List of Tables

  TOC \h \z \c "Table"    HYPERLINK \l "_Toc196009361"  Table 1:  
Summary of Appendices	  PAGEREF _Toc196009361 \h  2  

  HYPERLINK \l "_Toc196009362"  Table 2:   Summary of Inventory Analysis
Tools	  PAGEREF _Toc196009362 \h  3  

  HYPERLINK \l "_Toc196009363"  Table 3:   Philadelphia, PA portion of
Nonattainment Area VMT Growth Assumptions	  PAGEREF _Toc196009363 \h  6 


 

Summary of Appendices

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

Appendix E-2:	Philadelphia, PA Portion of Nonattainment Area PM2.5
Emissions Results 

(By Year, Functional Class and Vehicle Type)

Appendix E-3: 	MOBILE6.2 Input Parameter Summary

Appendix E-4: 	MOBILE6.2 Sample Input Files

Appendix E-5: 	Traffic Growth Forecasting System

INTRODUCTION

This technical document supports the PM2.5 State Implementation Plan
(SIP) for the Philadelphia, PA portion of the nonattainment area (Bucks
County, Chester County, Delaware County, Montgomery County and
Philadelphia County), Pennsylvania.  To meet the emission inventory
requirements of section 172(c)(3) of the Clean Air Act, a regional
mobile source highway inventory has been prepared for direct and
precursor PM2.5 emissions. 

The pollutants included in the inventory are primary emissions
(including condensibles) of PM2.5 , PM10 and the precursor emissions of
VOC, CO, NOx, SO2, and NH3. 

This document provides the 2002 base year and 2009 projections of mobile
(highway) vehicle miles of travel (VMT) and annual PM2.5 direct and
precursor emissions that are needed to satisfy the SIP requirements. 
The following sections summarize the methodology and data inputs used to
produce the mobile emissions inventory.

Methodology  

Guidance documents from EPA have been used to develop the base and
future year emissions inventories for the Philadelphia, PA portion of
nonattainment area.  They include:

Guidance for Creating Annual On-Road Mobile Source Emission Inventories
for PM2.5 Nonattainment Areas for Use in SIPs and Conformity, US EPA
Office of Transportation and Air Quality, dated August, 2005.

User’s Guide to MOBILE 6.1 and MOBILE6.2, Mobile Source Emission
Factor Model, EPA420-R-02-028, dated August 2003.

Technical Guidance on the Use of MOBILE6.2 for Emission Inventory
Preparation, US EPA Office of Air and Radiation, and Office of
Transportation and Air Quality, dated August 2004.

Mobile source emission factors have been calculated using EPA’s
MOBILE6.2 emission model.  The methodologies used to produce the
emission results conform to the recommendations provided in the above
guidance documents.  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  

For this submission, the 2002 base year emission estimates are
consistent with past analyses and submissions utilizing 2002 traffic and
environmental data.  Future year estimates for 2009 are based on the
latest available 2005 traffic data, PENNDOT growth rates, and
environmental parameters.  Current assumptions are used for control
strategies (e.g. Inspection-Maintenance, Pennsylvania Clean Vehicle
programs) and fuel characteristics.  The analysis methodology is
consistent with past statewide inventory efforts including the 2005
National Emissions Inventory (NEI) submission.  Annual VMT and emissions
are produced using a sum of 12 monthly analysis scenarios.  A detailed
methodology is provided in Appendix E-1.  Detailed information on the
Commonwealth’s Traffic Growth Forecasting System is provided in
Appendix E-5.  The following sections address the key input data sources
and analysis tools used for the preparation of the emissions inventory. 


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 VMT and emission results for the
region.  These include:

Table   SEQ Table \* ARABIC  1 :   Summary of Appendices

Appendix	Title	Description

E-1	Mobile Source Highway Emissions Inventory – 

An Explanation of Methodology	Provides summary of methodology used to
calculate the VMT and emissions.

E-2	Philadelphia, PA portion of Nonattainment Area PM2.5 Emission
Results (By Year, Functional Class and Vehicle Type)	Provides county by
functional class and county by vehicle type annual emission tables for
2002 and 2009.

E-3	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.

E-4	MOBILE6.2 Sample 

Input File	Provides examples of the MOBILE6.2 input files.

E-5	Traffic Growth Forecasting System	Provides detailed explanation of
the Commonwealth’s revised methodology for VMT forecasting based on
socioeconomic and demographic projections.



DATA SOURCES AND ANALYSIS TOOLS 

This section provides a summary of the key input data and analysis tools
used for producing the regional emissions inventory.  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 E-1 and E-5. 

Analysis Tools  

The inventory analysis utilizes several key software/programs for
producing the county emissions totals.  These tools are outlined in
Table 2.

Table   SEQ Table \* ARABIC  2 :   Summary of Inventory Analysis Tools

Tool	Purpose

MOBILE6.2	Produces emission factors for each pollutant in Grams/Mile for
direct PM2.5 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

Custom SCC Output Reformatting Program	Prepares output database files by
EPA’s Source Classification Codes (SCC)



The inventory reflects the highway mobile source emission estimations
using EPA’s MOBILE6.2 emission model, which accounts for changes in
vehicle technology and regulations.  MOBILE6.2 is a software application
program that provides estimates of current and future emissions from
highway motor vehicles.  All states other than California must use
MOBILE6.2 for the development of SIP and conformity emission analyses. 
The model can estimate both direct particulate matter emissions and the
emissions of certain particulate precursors for cars, trucks, buses, and
motorcycles.

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. 

Custom programs have also been prepared to translate the VMT and
emission results into a database file indexed by EPA’s Source
Classification Code (SCC).  This code represents combinations of vehicle
type groupings, functional classes, and time periods.  

Traffic Data Source/Fleet Data Inputs  

The PENNDOT Roadway Management System (RMS) data serves as the primary
highway data source for the county and functional class VMT estimates. 
The data source is used to provide a “snapshot” of the regional
roadway system and volumes in 2002 and 2005.  The data includes the
average annual daily traffic (AADT) volumes for all state roadways in
Pennsylvania.  To account for additional local roadway VMT and to ensure
consistency with reported HPMS totals, the 2002 and 2005 VMT totals are
adjusted to match the annual HPMS VMT totals reported to FHWA.  

Annual VMT and emission results are based on a MOBILE6.2 analysis for an
average day in each of the 12 months.  These results are then expanded
to monthly sub-totals and then to an annual total.  The daily and
monthly seasonal factors, used to adjust the AADT traffic volumes, are
developed from data contained in the document, 2005 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 2005 traffic counts taken at permanent and
in-pavement ATR (automatic traffic recorder) locations throughout the
state.  The factors are used to adjust AADT volumes to an average day in
each month, and the PPSUITE software calculates unique congested speeds
for each roadway segment.

 

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 2005 Pennsylvania Traffic Data
report are used to determine the temporal variations of future year
traffic volumes.

Vehicle mix patterns are calculated for each county / functional class
grouping utilizing a combination of 2002/2005 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 E-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 and 2005 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 forecasting plays a pivotal role in estimating future year
emissions for each Pennsylvania county and region.  The expected volume
of traffic, measured in vehicle miles of travel (VMT), needs to be
estimated for each county, or group of counties, for each relevant
future year.  This becomes the basis for further disaggregation of VMT
to the roadway types on which the miles are expected to occur, vehicle
types and vehicle age.  

This PM2.5 inventory utilizes a VMT growth rate projection methodology
developed by PENNDOT as documented in the report “Statistical
Evaluation of Projected Traffic Growth, Traffic Growth Forecasting
System: Final Report, March 14, 2005”.  As part of that study, a
statewide traffic growth forecasting system was developed that
incorporates traffic data from PENNDOT’s Traffic Information System
and available socioeconomic forecasts.  The study methodology has been
shared among PENNDOT, DEP, and other interagency consultation group
members, including the Pennsylvania Air Quality Work Group (which
includes EPA, FHWA, and representatives from larger PA Metropolitan
Planning Organizations (MPOs), and approved by PENNDOT.  The methodology
contains the following improvements over past statewide forecasting
approaches:

Strong statistical basis and consistent with state of the art.

Thorough documentation of approach vs. alternatives.

Increased data robustness through the inclusion of both county-level
historical traffic trends from the PENNDOT Roadway Management System
(RMS) databases (the basis for VMT reporting to the Federal Highway
Administration of USDOT through the Highway Performance Monitoring
System (HPMS) and county-based demographic projections from an
independent 3rd party (Woods and Poole Economics, Inc.).

Expedient and inexpensive update process.  

The data inputs to the traffic growth forecasting system are
periodically updated to produce revised forecast growth factors for each
county in the state.  The frequency of this update is at least every 5
years, consistent with EPA and FHWA “Latest Planning Assumptions”
guidance.  

The most recent available forecasts, used in the development of this
inventory, include historic HPMS VMT through 2005 and use of the 2006
State Profile, developed by Woods & Poole Economics. The 2006 State
Profile includes historical demographic data and forecasts by year from
1969 through 2030 for every county and Metropolitan Statistical Area
(MSA) in Pennsylvania.  The county VMT forecast growth rates are
developed for four functional classifications in each county: urban
interstate, urban non-interstate, rural interstate and rural
non-interstate.  The PENNDOT statistical VMT forecasting model
incorporates historical VMT trends, socio and economic data (households,
mean household income), and a relative measure of transportation
capacity (lane miles per capita).  

The forecasts used for this annual PM2.5 emissions inventory have been
developed to account for potential variability in future regional VMT
growth.  Variability from the base forecast may be caused by multiple
factors which influence vehicle travel, many or most of which may be
influenced by outside factors or events.  The county-level growth rates
from the PENNDOT VMT forecasting system have been evaluated to determine
an overall regional growth rate for the nonattainment area.  Growth
rates were examined for counties within the nonattainment area and for
nearby counties that might impact future conditions within the region.  

Table 3 summarizes the assumed projected growth of VMT for future
analysis years within the nonattainment area.

Table   SEQ Table \* ARABIC  3 :   Philadelphia, PA Portion of
Nonattainment Area VMT Growth Assumptions

Analysis

Year	Total Growth 

From 2002	Annualized Growth From Previous Analysis Year

Bucks County

2002	-----	-----

2009	15.6%	2.2%

Chester County

2002	-----	-----

2009	15.6%	2.2%

Delaware County

2002	-----	-----

2009	18.9%	2.7%

Montgomery County

2002	-----	-----

2009	16.5%	2.4%

Philadelphia County

2002	-----	-----

2009	17.7%	2.5%



I/M and Fuel Parameters  

The Inspection Maintenance (I/M) program inputs to the MOBILE6.2 model
are based on past and current programs within the Philadelphia area.  

Pennsylvania’s first inspection and maintenance (I/M) program was
implemented in 1984 which required applicable vehicles to undergo an
annual one-speed idle test. This basic I/M program applied to model-year
1975-1980 gasoline cars and light duty trucks up to 9,000 pounds GVW
registered in the 5-county Philadelphia region (Bucks, Chester,
Delaware, Montgomery and Philadelphia counties) and the 4-county
Pittsburgh metropolitan region (Allegheny, Beaver, Washington and
Westmoreland counties).   

In October 1997, Pennsylvania began an enhanced I/M Program to include
ASM 5015 tailpipe testing, two-speed idling test, gas cap and visual
anti-tempering inspection. Model-year 1981 and newer cars and light duty
trucks registered in the above nine counties in the Philadelphia and
Pittsburgh regions are subject to the enhanced I/M Program.  New model
years are exempt for the first year.

The Commonwealth’s 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 2002 I/M program inputs to the MOBILE6 model for the 5-county
Philadelphia region include a PA97 with ASM I/M program and phase-in
cutpoints.  The I/M program parameters include:

Model Years	Program Parameters

1981 & newer	ASM5015 with Phase-in

1975 & newer	Gas Cap

1975 – 1980	Idle

1975 & newer	ATP



The 2009 I/M program inputs to the MOBILE6 model for the Philadelphia
region include a PAOBDII and PA97 with ASM I/M program and final
cutpoints.  The I/M program parameters include:

Model Years	Program Parameters

1996 & newer	PAOBDII

Gas Cap

1981 – 1995	ASM 5015 Final

1975 – 1995	Gas Cap

1975 & newer	ATP



The RVP values, varying by month, 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 E-3.

Weather Data  

Updated weather information has been 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 2005 NEI inventory submission.  Average minimum
and maximum temperatures and barometric pressure values for each month
were obtained for each of the weather station locations in Pennsylvania.
 In addition, average relative humidity values were obtained for 6-hour
intervals (4 intervals during a 24 day period) for each of the 12
months.  Absolute humidity values by month were then calculated from the
relative humidity, barometric pressure, and temperature for each of the
4 daily intervals using EPA’s M6HUMID program.  The lowest of these 4
values for each month is determined to be the absolute humidity for that
month.

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 Programs

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.

State Programs   

The MOBILE6.2 software also allows for modeling of permissible state
activities control emissions from highway vehicles. 

In 1998, Pennsylvania promulgated the New Motor Vehicle Emissions
Control Program. This program created the Pennsylvania Clean Vehicles
Program that 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.  As a compliance alternative to
the Pennsylvania Clean Vehicles Program, automakers have elected to
comply with the National Low Emission Vehicle (NLEV) program. The NLEV
program began phase-in starting in model year 1999.  The Pennsylvania
rules allow the NLEV compliance option for the duration of
Pennsylvania’s participation in the NLEV program.  Pennsylvania is in
the process of amending the Pennsylvania Clean Vehicles Program to
initiate in model year 2008.  As a result, the modeling results assume a
2008 start year for the Pennsylvania Clean Vehicles Program.  Benefits
from this program are realized in 2008 and beyond. 

The methodology employed to estimate the benefits of adopting CA LEV II
emissions standards is consistent with the approach provided in the
EPA’s June 2002 Guidance (Modeling Alternative NLEV Implementation and
Adoption of California Standards in MOBILE6, June 5, 2002). The approach
assumes:

Tier2 phase-in schedule consistent with MOBILE6.2 defaults

LEVII phase-in schedule as provided in EPA’s June 2002 Guidance

Assumes PZEV and AT-PZEV vehicles share the same evaporative emissions
as LEVII/Tier2 vehicles

Appendix E-4 contains the modified MOBILE6.2 files used to model the
above assumptions. They are consistent with the June 2002 EPA guidance. 

The federal Tier 2 / Low Sulfur Fuel Program took effect in 2004 and in
practicality supplanted the NLEV program for new light-duty vehicles. 

RESOURCES 

Guidance for Creating Annual On-Road Mobile Source Emission Inventories
for PM2.5 Nonattainment Areas for Use in SIPs and Conformity, US EPA
Office of Transportation and Air Quality, dated August, 2005.

Consolidated Emissions Reporting, Federal Register, June 10, 2002

2005 Pennsylvania Traffic Data, PennDOT Bureau of Planning and Research,
2005.  

User’s Guide to MOBILE6.1 and MOBILE6.2, Mobile Source Emission Factor
Model, EPA420-R-02-028, dated August 2003.

Technical Guidance on the Use of MOBILE6 for Emission Inventory
Preparation, US EPA Office of Transportation and Air Quality, August
2004.

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.

Technical Guidance on the Use of MOBILE6.2 for Emission Inventory
Preparation, US EPA Office of Air and Radiation, and Office of
Transportation and Air Quality, August 2004.

Statistical Evaluation of Projected Traffic Growth, Traffic Growth
Forecasting System: Final Report, Michael Baker Jr., Inc., March 14,
2005.

	

 PAGE   25 

	

 PAGE   1 

