# APPENDIX C-1

Berks County - An Explanation of MethodologyAn Explanation of Methodology 

### Explanation of Methodology

May 2012



# TABLE OF CONTENTS

INTRODUCTION ......................................

................................................... ................................................... ........... 1

O VERVIEW OF E MISSIONS I NVENTORIES

.................................................. ................................................... ............... 1

H IGHWAY V EHICLE E MISSION I NVENTORIES

.................................................. ................................................... ........ 1

WHERE DOES PENNSYLVANIA OBTAIN ITS DATA? ..........

................................................... ........................ 4

S UMMARY OF MOVES I NPUTS

.................................................. ................................................... ............................. 4

V EHICLE M ILES OF T RAVEL (VMT) .............................................

................................................... .......................... 5

A DJUSTMENTS TO R OADWAY D ATA

.................................................. ................................................... ..................... 8

V EHICLE T YPE P ROCESSING

.................................................. ................................................... ................................. 9

V EHICLE F LEET AND P OPULATION D ATA

.................................................. ................................................... ........... 10

E NVIRONMENTAL

, F UEL AND T ECHNOLOGY A SSUMPTIONS

.................................................. .................................. 11

SPEED/EMISSION ESTIMATION PROCEDURE ...............

................................................... ............................ 12

V OLUME /VMT D EVELOPMENT

.................................................. ................................................... .......................... 12

S PEED /D ELAY D ETERMINATION

.................................................. ................................................... ......................... 15

HPMS AND VMT A DJUSTMENTS

.................................................. ................................................... ....................... 16

MOVES E MISSIONS R UN

.................................................. ................................................... ................................... 17

RESOURCES .........................................

................................................... ................................................... .............. 18

HIGHWAY VEHICLE INVENTORY GLOSSARY ................

................................................... .......................... 19



## List of Exhibits

E XHIBIT 1: S UMMARY OF PPSUITE P ROCESS

.................................................. ................................................... ........... 3

E XHIBIT 2: MOVES L OCAL D ATA I NPUT S UMMARY

.................................................. ................................................... 4

E XHIBIT 3: P ENN DOT U RBAN /R URAL AND F UNCTIONAL C LASS C ODES

.................................................. ..................... 6

E XHIBIT 4: E MISSION F ACTOR VS

. S PEED V ARIANCES (NO X ) ................................................. ....................................... 7

E XHIBIT 5: MOVES S OURCE T YPES AND HPMS V EHICLE G ROUPS

.................................................. ............................ 9

E XHIBIT 6: PPSUITE S PEED / E MISSION E STIMATION P ROCEDURE

.................................................. ............................ 13Appendix C -1 1



## INTRODUCTION

The purpose of this document is to explain how the Pennsylvania Department of Environmental Protection (Department) estimates emissions from hi ghway vehicles for inclusion in its emission inventories and State Implementation Plans.



## Overview of Emissions Inventories

The Department’s inventories generally categorize e missions into four categories:

• Highway vehicles.

• Stationary sources (major industrial, commercial an d utility sources).

• Area sources (smaller industrial/commercial sources , consumer products).

• Nonroad mobile sources (including construction and agricultural equipment, lawn and garden equipment).

An evaluation of emissions from point, area, and mo bile sources is needed to develop a complete inventory needed for a maintenance demonstration pl an. This documentation addresses the mobile source activity and emissions for base and future years us ed to support such a demonstration.

Of all of the sources of air pollution, only the em issions of some stationary sources are measured dir ectly and continuously through instrumentation. Emission s from all other sources must be modeled based on available local data, including those from highway vehicles. In their very simplest form, estimates o f emissions follow the following pattern:

Emission rate x activity level = emissions per time period (usually day or year)

Most emission rates have been developed by the U.S. Environmental Protection Agency (EPA), in cooperation with industry and states, and are compi led and documented into key references or emission models. These include Compilation of Air Pollution Emission Factors (AP-42), the Motor Vehicle Emission Simulator (MOVES) model, and the NONROAD m odel. Adding up the products of the emission rates and activity levels for all sources of a given pollutant constitutes the emission inven tory for that pollutant.



## Highway Vehicle Emission Inventories

Highway vehicles contribute significantly to air po llution, particularly to ground-level ozone, which is the most persistent air pollutant in Pennsylvania. Gro und-level 

### ozone is not emitted directly to the atmosphere, but is formed by photochemical reaction s between volatile organic compounds (VOCs) and oxides of nitrogen (NO

x 

### ) in the presence of sunlight. The long, hot, humi d days of summer are particularly conducive to ozone formatio n, so ozone levels are of concern primarily during the months of May through September. Both VOCs and NOx are emitted from highway vehicles. Pennsylvania’s ozone-related emission in ventory efforts focus on these two types of polluta nts.

Obviously, direct measurement of emission levels fr om all vehicles in use is impossible. In compariso n to highway vehicles, estimating residential heating emissions is a fairly simple calculation because t here is a constant emission rate and a fairly simple mea sure of activity. However, for highway vehiclesAppendix C -1 2

estimating the emission rate and activity levels of all vehicles on the road during a typical summer d ay is a complicated endeavor.

If every vehicle emitted the same amount of polluti on all the time, one could simply multiply those emission standards (emission rate in grams of pollu tion per mile) times the vehicle miles traveled (VM T)

to estimate total emissions. But emission rates fr om all vehicles vary over the entire range of condi tions under which they operate. These variables include air temperature, speed, traffic conditions, operati ng mode and fuel characteristics. The inventory must also account for non-exhaust or evaporative emissio ns. In addition, the fleet is composed of several gener ations and types of vehicles with different emissio n control technologies. This requires the estimation algorithm include the composition of the fleet (veh icle ages and types).

In order to estimate both the rate at which emissio ns are being generated and to calculate vehicle mil es traveled (activity level), Pennsylvania examines it s road network and fleet to estimate vehicle activi ty. For ozone-related inventories, this is done for a t ypical summer weekday. For carbon monoxide (CO) an d particulate matter (PM) emission inventories, this may be done for a typical winter weekday, summer weekday and/or annual conditions. Not only must th is be done for a baseline year, but it must also be projected into the future. This process involves a large quantity of data and is extremely complex.

Computer models have been developed to perform thes e calculations by simulating the travel of vehicles on the Commonwealth’s roadway system. The models a lso generate emissions rates (also called emission factors) for different vehicle types for area-speci fic conditions, and then combine them in summary fo rm. The area-specific conditions include vehicle and hi ghway data, plus control measure characteristics an d future year projections of all variables. The key models used to generate this mobile source emission s inventory are:

MOVES: EPA’s MOVES model was officially released on Marc h 2, 2010 and was followed with a revised version (MOVES2010a) in August 2010. The M OVES model provides a more robust estimate of emissions as compared to its predecessor MOBILE6.2. MOVES calculates average in-use fleet emissions for each of thirteen categories of vehicles under v arious conditions affecting in-use emission levels (e.g., ambient temperatures, average traffic speeds, gasol ine volatility) as specified by the model user.

For this mobile source inventory, Pennsylvania used MOVES2010a as approved by EPA. MOVES can be used to estimate national, state, and county lev el inventories of criteria air pollutants, precurso rs, greenhouse gas emissions, and some mobile source ai r toxics from highway vehicles. Additionally, MOVES can make projections for energy consumption ( total, petroleum-based, and fossil-based).

PPSUITE: For the Department’s highway emissions inventory, a post processor named PPSUITE (formerly named PPAQ - Post Processor for Air Quali ty) is used, which consists of a set of programs th at perform the following functions:

• Analyzes highway operating conditions.

• Calculates highway speeds.

• Compiles vehicle miles of travel (VMT) and vehicle type mix data.

• Prepares MOVES runs and processes MOVES outputs.

PPSUITE is a widely used and accepted tool for esti mating speeds and processing emissions rates. The software is based upon accepted transportation engi neering methodologies. For example, PPSUITE uses speed and delay estimation procedures based on plan ning methods provided in the Highway Capacity

Manual , a report prepared by the Transportation Research Board (TRB) summarizing current knowledge and analysis techniques for capacity and level-of-s ervice analyses of the transportation system.Appendix C -1 3

The PPSUITE process is integral to producing key in put files to the MOVES emission model. Exhibit 1 summarizes the key functions of PPSUITE and the tra ffic-related input files prepared for the MOVES County Data Manager (CDM).



### Exhibit 1: Summary of PPSUITE Process

The following sections summarize the key data and m ethodologies used to produce the mobile source emissions inventory. This includes a summary of lo cal data sources and a step-by-step review of the speed calculation process. The emission data and p rocess has been developed according to recommendations provided by EPA in key policy and t echnical guidance as provided below:

• Policy Guidance on the Use of MOVES2010 for SIP Dev elopment, Transportation Conformity, and Other Purposes , US EPA Office of Air and Radiation, EPA-420-B-09- 046, December 2009.

• Technical Guidance on the Use of MOVES2010 for Emis sion Inventory Preparation in State Implementation Plans and Transportation Confo rmity , US EPA Office of Air and Radiation, and Office of Transportation and Air Qua lity, EPA-420-B-10-023, April

2010.

The process has focused on developing an emissions inventory using the available tools and data to its

fullest extent. This includes the use of available local data for items that have a significant impac t on emissions and applying a robust calculation process to estimate hourly traffic speeds.Appendix C -1 4



## WHERE DOES PENNSYLVANIA OBTAIN ITS DATA?

Summary of MOVES Inputs

A large number of inputs to MOVES are needed to ful ly account for the numerous vehicle and environmental parameters that affect emissions. Th ese include traffic flow characteristics (as determ ined from the PPSUITE software), vehicle descriptions, f uel parameters, inspection/maintenance program parameters, and environmental variables. MOVES incl udes a default national database of meteorology, vehicle fleet, vehicle activity, fuel, and emission control program data for every county; but EPA can not certify that the default data is the most current o r best available information for any specific area. As a result, local data is recommended for use for analy ses supporting state implementation plans (SIPs).

A mix of local and default data is used for this in ventory. Local data sources are used for all input s that have a significant impact on calculated emission ra tes. Exhibit 2 summarizes Pennsylvania-specific inputs assembled and used for this inventory. Thes e data items are discussed in the following section s.



### Exhibit 2: MOVES Local Data Input Summary

Traffic Vehicl e Fuel Inspection Environmental Data Descripti ons Parameters Maintenance Variables

Vehicle Type Vehicle Type RVP Start Year Hourly

VMT Mix Model Years Temperatures

Vehicle Vehicle Age Sulfur Test Standards, Population Distribution Level Source Types, Humidity Frequency

VMT Average Speeds Ethanol Stringency, Fractions (PPSUITE) Volume Waiver Rate, (PPSUITE) Compliance

Road Type Hourly Refueling

Distribution Distributions Controls (PPSUITE)

Ramp

Fraction (PPSUITE)

Emission RatesAppendix C -1 5



## Vehicle Miles of Travel (VMT)

The VMT input to emissions calculations for Pennsyl vania is based on information from the Roadway Management System (RMS) maintained by the Pennsylva nia Department of Transportation’s (PennDOT’s) Bureau of Planning and Research (BPR). PennDOT obtains this information from periodic

visual and electronic traffic counts. RMS data is dynamic, since it is continually reviewed and updat ed

from new traffic counts and field visits conducted by PennDOT. Information on roadways included in th e National Highway System is reviewed at least annual ly, while information on other roadways is reviewed at least biennially.

On a triennial basis, a current “snapshot” of the R MS database is taken and downloaded to provide an u pto-date record of the Commonwealth’s highway system for estimating emissions. This emissions inventory is based on the most current snapshot of the RMS data.

The RMS database contains all state highways, inclu ding the Pennsylvania Turnpike, divided into segments approximately 0.5 miles in length. These segments are usually divided at important intersections or locations where there is a change in the physical characteristics of the roadway (e.g . the number of lanes changes). There are approximately 99,000 state highway segments for the 67 Pennsylvania counties contained in the RMS. Each o f these segments contains an abundance of descriptive data, but only the following informatio n is extracted for emission calculations:

• Lanes.

• Distances.

• Volumes representing Average Annual Daily Traffic ( AADT).

• Truck percentages.

• PennDOT urban/rural classifications.

• PennDOT functional class codes.

• Number of signals (based on linkage to PennDOT GIS signal location data).

RMS volumes and distances are used in calculating h ighway VMT totals for each county. As discussed in the next section, adjustments are needed to conv ert the volumes to an average summer weekday, winte r weekday, and monthly day. In addition, the traffic volumes must be forecast to support future year emission inventories. Lane values and traffic sign als are an important input for determining the congestion and speeds for individual highway segmen ts. Truck percentages are used in the speed determination process and are used to split volumes to individual vehicle types used by the MOVES

software.

Road segments are classified by function, as well a s whether it is located in an urban, small urban or rural area, as indicated below in Exhibit 3. The PennDOT urban/rural (UR) and functional classes (FC) are important indicators of the type and function of ea ch roadway segment. The variables provide insights

into other characteristics not contained in the RMS data that are used for speed and emission calculat ions.Appendix C -1 6 

### Exhibit 3: PennDOT Urban/Rural and Functional Class Codes

Urban/Rural Code 1=Rural

2=Small Urban

3=Urban

Functional Class Rural Functional Classes Used Urb an Functional Classes Used

For Rural Areas For Small Urban and Urban Area s

------------------------------------- ---------- -------------------------------- 1=Rural Freeway 11=Urban Freeway 2=Rural Other Principal Arterial 12=Urban Expres sway 6=Rural Minor Arterial 14=Urban Principal Arter ial 7=Rural Major Collector 16=Urban Minor Arterial

8=Rural Minor Collector 17=Urban Collector

9=Rural Local 19=Urban Local

Additional Network Information: The PPSUITE software system allows for many additio nal variables

other than those available in the RMS database. Us ing these variables improves the ability of the Department to incorporate real roadway conditions i nto its estimates. The variables include informati on regarding free-flow speeds and capacities, signal c haracteristics and other physical roadway features that can affect a roadway’s calculated congested speed. This data can be determined from lookup tables bas ed on a roadway segment’s urban/rural code and functio nal class. Much of the lookup table data was developed from information contained in the Highway Capacity Manual , PennDOT information on speeds and signal densities, and other engineering judgment.

MOVES Traffic Inputs: The PPSUITE software uses RMS traffic data to prep are key inputs to the MOVES emission model including:

• VMT.

• Travel speeds.

• Road type distributions.

• Ramp fractions.

VMT is the primary traffic input that affects emiss ion results. The roadway segment distances and tra ffic volumes are used to prepare estimates of VMT. PPSU ITE performs these calculations and outputs the MOVES annual VMT input file to the County Data Mana ger (CDM).

Emissions for many pollutants (including both VOC a nd NOx) vary significantly with travel speed. While VOCs generally decrease as speed increases, N Ox decreases at the low speed range and increases at higher speeds, as illustrated in Exhibit 4. To obtain the best estimate of vehicle speeds, the Dep artment uses the PPSUITE set of programs, whose primary fun ction is to calculate speeds and to organize and simplify the handling of large amounts of data need ed for calculating speeds and for preparing MOVES input files. The PPSUITE software prepares the MOV ES vehicle hours of travel (VHT) by speed bin file which summarizes the distribution of speeds across all links into each of 16 MOVES speed bins for each hour of the day. This robust process ensures that MOVES emission rates are used to the fullest extent and

is consistent with the methods and recommendations provided in EPA’s Technical Guidance on the Use of MOVES2010 for Emissions Inventory Preparation in State Implementation Plans and Transportation Conformity

.Appendix C -1 7 

### Exhibit 4: Emission Factor vs. Speed Variances (NOx )

In MOVES, typical drive cycles and associated opera ting conditions vary by the type of roadway. MOVES defines five different road types as follows:

1 Off-Network.

2 Rural Restricted Access.

3 Rural Unrestricted Access.

4 Urban Restricted Access.

5 Urban Unrestricted Access.

The off-network road type includes emissions from v ehicle starts, extended idle activity, and evaporat ive emissions. Off-network activity in MOVES is primar ily determined by the Source Type Population input, as discussed in a following section. The re maining distribution among road types is determined by equating the PennDOT functional class with each MOV ES road type as follows:

• MOVES Road Type (2) = PennDOT Functional Class (1).

• MOVES Road Type (3) = PennDOT Functional Class (2,6 ,7,8,9).

• MOVES Road Type (4) = PennDOT Functional Class (11, 12).

• MOVES Road Type (5) = PennDOT Functional Class (14, 16,17,19).

For this inventory, the MOVES road type distributio n file is automatically generated by PPSUITE using the defined equivalencies.

Since ramps are not directly represented within the RMS database information, it is assumed that 8% of the Freeway VHT is Ramp VHT. This is consistent wi th the recommendations provided in EPA’s technical guidance. Source: Figure 3 from Implications of the MOVES2010 Model on Mobile Source Emission Estimates, Air & Waste Management A ssociation, July 2010.Appendix C -1 8



## Adjustments to Roadway Data

Before the RMS data can be used by PPSUITE for spee d and emission calculations, several adjustments and additions must be made to the roadway data. Th ese adjustments are summarized below.

HPMS Adjustments: According to EPA guidance, baseline inventory VMT computed from the RMS highway segment volumes must be adjusted to be cons istent with Highway Performance Monitoring System (HPMS) VMT totals. The HPMS VMT reported for Pennsylvania is a subsystem of the RMS established to meet the data reporting requirements of the Federal Highway Administration (FHWA) and to serve as PennDOT’s official source of highway in formation. Although it has some limitations, the HPMS system is currently in use in all 50 states an d is being improved under FHWA direction.

Although the HPMS VMT and the roadway data used for an inventory emissions analysis are both based on data from the RMS system, differences do exist b etween them and include the following. First, the HPMS and inventory roadway data are “snapshots” of the RMS data taken at different times. Since the RMS is dynamic, changing constantly due to new data , differences will result between the data used for calculating HPMS VMT totals and the inventory data used for an emissions analysis. Second, since the RMS does not contain many of the local roadways, lo cal road estimates of HPMS VMT are obtained through alternative procedures developed by PennDOT . To account for such differences, adjustment factors are calculated and used to adjust the inven tory roadway data to the reported HPMS VMT totals

submitted to FHWA. The VMT contained in the HPMS re ports are considered to represent average annual daily traffic (AADT).

Adjustment factors are calculated which adjust the base year RMS download VMT to the reported HPMS totals for that year. These factors are developed for each county and functional class combination an d are also applied to all future year runs. Adjustments for the “higher” functional classes (e.g. Freeway, Arterials - major routes) are close to 1.000 since HPMS VMT is derived from RMS information, and the only difference in the data is that the “snapshot” for the emission calculations is taken at a differe nt time than for the HPMS. “Lower” classes (e.g. local roa ds) require greater adjustment since a large part o f the local system is not under state jurisdiction and is not in the RMS database. There is, of course, a significant amount of local road mileage in the sta te. It is assumed that those local streets that are in RMS are representative of all local streets in their ar ea with respect to volume and speed, so that roadwa y mileage adjustment is appropriate.

Seasonal Adjustments to Volumes: The RMS contains AADT volumes that are an average of all days in the year, including weekends and holidays. An ozo ne emission analysis, however, is based on a typica l July or summer weekday. PM and CO analyses requir e volumes representing a typical summer or winter weekday and monthly average conditions (needed for producing annual totals). Therefore, the RMS volumes must be seasonally adjusted. Seasonal fact ors were developed for each functional class and urban/rural code based on yearly count information prepared by PennDOT’s BPR. These factors are applied to the existing RMS AADT volumes to produce the July volumes. The same factors are also used to develop the MOVES daily and monthly VMT fraction files.

Hourly Adjustments: Speeds and emissions vary considerably depending on the time of day. Therefore, it is important to estimate the pattern by which roadway volume varies by hour of the day. The 24-hour pattern data provides PPSUITE with informat ion used to split the daily roadway segment volumes to each of the 24 hours in a day. Pattern data is in the form of a percentage of the daily vo lumes for each hour. Distributions are provided for each county and functional class grouping. This data i s developed from 24-hour count data compiled by PennD OT’s BPR, according to the process in the agencies annual traffic data reports. The same fac tors are also used to develop the MOVES hourly

fraction file.Appendix C -1 9

Traffic Volume Forecasts: Traffic growth forecasting plays a pivotal role i n estimating future year emissions for the region. There are many uncertain ties affecting projections of traffic growth, inclu ding the current economic conditions, potential fuel pri ces, the impacts of Marcellus Shale activities in m any counties throughout the state, and the future growt h in population and employment. Growth rates for t he Department’s emissions inventories are based on an assessment of available data sources which include:

• PennDOT BPR growth rate forecasting system.

• Regional travel model, if available.

• Estimates of Marcellus Shale related activity growt h, if applicable.

All SIP mobile source highway inventories include t he review and assessment of county-specific growth rates from a PennDOT study originally completed in 2005 and documented in the report, Statistical Evaluation of Projected Traffic Growth, Traffic Gro wth Forecasting System: Final Report, March 14,

2005 . As part of that study, a statewide traffic growt h forecasting system was developed that incorporate s traffic data from PennDOT’s Traffic Information Sys tem and socioeconomic forecasts. That forecasting system is maintained by the PennDOT BPR and is upda ted on a periodic basis to develop new statistical relationships between historic VMT growth and popul ation and updated demographic forecasts from Woods and Poole, Inc. The growth rates from the Pe nnDOT BPR forecasting system are evaluated against other available data including travel model growth and other insights.



## Vehicle Type Processing

Emission rates within MOVES vary significantly by t he type of vehicle. The MOVES model produces emissions and rates by thirteen MOVES vehicle sourc e types. However, VMT is input to MOVES by six HPMS vehicle groups. Exhibit 5 summarizes the dist inction between each classification scheme.



### Exhibit 5: MOVES Source Types and HPMS Vehicle Grou ps

SOURCE TYPES HPMS Class Groups 11 Motorcycle 10 Motorcycle 21 Passenger Car 20 Passenger Car 31 Passenger Truck 30 Passenger/Light Truck 32 Light Commercial Truck 40 Buses 41 Intercity Bus 50 Single Unit Trucks

42 Transit Bus 60 Combination Trucks

43 School bus

51 Refuse Truck 52 Single Unit Short-haul Truck 53 Single Unit Long-haul Truck

54 Motor Home

61 Combination Short-haul Truck 62 Combination Long-haul Truck

The process used for this inventory includes a meth od to disaggregate the RMS traffic volumes to the thirteen source types and then to recombine the est imates to the six HPMS vehicle classes. Vehicle t ype pattern data is used by PPSUITE to divide the hourl y roadway segment volumes to the thirteen MOVES source types. Similar to the 24-hour pattern data, this data contains percentage splits to each sourc e type for every hour of the day. The vehicle type patter n data for this inventory is developed from several

sources of information:Appendix C -1 10

• PennDOT truck percentages from the RMS database.

• Hourly distributions for trucks and total traffic c ompiled by PennDOT’s BPR.

• Transit data from PennDOT and the National Transit Database.

• School bus registration data from PennDOT’s Bureau of Motor Vehicles Registration Database.

The vehicle type pattern data is developed for each county and functional class combination. First, R MS truck percentages are averaged for all roadways wit hin a county and functional class grouping. Using this percentage data, the total roadway volume for any s egment is divided to auto and truck vehicle type categories. The transit data and school bus data i s used to further disaggregate trucks, resulting in four vehicle groups (light-duty, school, transit, and ot her heavy-duty).

From these groups, MOVES default Pennsylvania count y VMT distributions by source type are used to divide the four groups into each of the MOVES sourc e types. PennDOT hourly distributions for trucks and total traffic are used to create source type pe rcentage breakdowns for each hour of the day.

Vehicle Type Capacity Analysis Factors : Vehicle type percentages are provided to the cap acity analysis section of PPSUITE to adjust the speeds in response to trucks. That is, a given number of la rger trucks take up more roadway space than a given numb er of cars, and this is accounted for in the speed estimation process by adjusting capacity using info rmation from the Highway Capacity Manual

.



## Vehicle Fleet and Population Data

The information on the vehicle fleet including the number and age of vehicles has a significant impact on forecasted start and evaporative emissions within M OVES. The MOVES Model requires the population of vehicles by the thirteen source type categories. Pennsylvania county vehicle registration data is used to estimate vehicle population for light-duty vehicles and school buses. The data is split to source typ es using MOVES2010a default Pennsylvania county popula tion data. For transit buses, data from PennDOT and the National Transit Database (NTD) is used to estimate county transit bus totals. Other heavy-du ty vehicle population values are based on VMT for each source type using the vehicle mix and pattern data discussed previously. The PPSUITE software automat ically applies default MOVES2010a ratios of VMT and source type population (e.g. the number of mile s per vehicle by source type) to the local VMT estimates to produce vehicle population.

Vehicle population is forecast based on projected h ousehold and population growth from Woods and Poole Inc. for each Pennsylvania county. The growt h rate methodology includes:

• Choosing the highest growth rate between population and households.

• Limiting growth as to not exceed the VMT growth ass umptions.

Vehicle Age: Vehicle age distributions are input to MOVES for e ach county by the thirteen source types. The distributions reflect the percentage of vehicle s in the fleet up to 31 years old. The most recent available registration download from PennDOT’s Bure au of Motor Vehicles Registration Database has been used for the inventory. Due to insufficient d ata, only information for light-duty vehicles are u sed as local inputs; and, heavy-duty vehicles use the inte rnal MOVES2010a national defaults. The registratio n data download is based on MOBILE6.2 vehicle categor ies. As a result, the data was converted to source types using the EPA convertor spreadsheets provided with the MOVES2010a emission model.Appendix C -1 11



## Environmental, Fuel and Technology Assumptions

Information on environmental, fuel, vehicle technol ogy and other control strategy assumptions were

determined based on a review of MOVES2010a default information by the PaDEP.

Fuel Parameters: The same vehicle will produce different emissions using a different type of gasoline. Fuel control strategies can be powerful emission re duction mechanisms. The MOVES2010a default fuel formulation and fuel supply data were reviewed and updated based on available local volumetric fuel property information. The gasohol market penetrati on and RVP values were updated for all the counties

. MOVES2010a default data was used for the rest of th e parameters.

Refueling Emissions : MOVES also allows users to calculate refueling em issions, the emissions created

when vehicles are refueled at service stations. Pe nnsylvania includes refueling emissions in its area source inventory and not in its highway vehicle inv entory. Refueling emissions are not included in th e highway emissions inventory.

Vehicle Emission Inspection/Maintenance (I/M) Param eters: MOVES allows users to vary inputs depending on the I/M program in place for the area. The inputs include:

• Program start year.

• Stringency level.

• First and last model years subject to the program.

• Waiver rates.

• Compliance rates.

• Program type (test-only, test-and-repair, etc.) and effectiveness.

• Frequency of inspection (annual, biennial).

• Vehicle type coverage.

• Test type (idle, loaded, etc.)

The MOVES2010a default Pennsylvania assumptions wer e reviewed and modifications were made per actual program parameters.

Environmental Variables: Evaporative emissions are influenced significantly by the temperatures of the surrounding air. Hourly temperatures have been com piled for each county based on information from WeatherBank, Inc. to specify temperatures from nine airports within the state. Ozone analysis temperature and humidity values were determined usi ng the procedures documented in EPA’s technical guidance. Minimum and maximum temperatures for eac h month were converted to hourly temperatures using EPA convertors supplied with the MOVES2010a m odel.

A summary of the MOVES related inputs used for the inventory and future year estimates are attached

with the submission.Appendix C -1 12



## SPEED/EMISSION ESTIMATION PROCEDURE

The previous sections have summarized the input dat a used for computing speeds and emissions for Pennsylvania. This section explains how PPSUITE an d MOVES uses that input data to produce emission estimates. Exhibit 6 summarizes PPSUITE’s analysis procedure used for each of the RMS highway segments in the state.

Producing an emissions inventory with PPSUITE requi res a process of disaggregation and aggregation. Data is available and used on a very small scale -- individual 1⁄2 mile roadway segments 24 hours of the day. This data needs to be processed individually to determine the distribution of vehicle hours of t ravel (VHT) by speed and then aggregated by vehicle class to determine input VMT to the MOVES emission

model.



## Volume/VMT Development

Before speeds can be calculated and MOVES run, volu mes acquired from RMS must be adjusted and disaggregated. Such adjustments include factoring to future years, seasonal adjustments, and disaggregating daily volumes to each hour of the da y and to each of the thirteen MOVES source types.

Determine Future Year Volumes : The RMS database contains up-to-date current year volumes. However, to conduct a future year analysis, these v olumes must be factored to the year being analyzed. Growth factors have been prepared for each county a nd functional class grouping. These growth factors are applied to the base year RMS volumes to obtain future year estimates that can be utilized by

PPSUITE.

Example:

A typical freeway link in the RMS database is I-80 segment 2500 in Luzerne County, Pennsylvania. This link has an urban/rural code=1 which indicates the link is in a rural area, and a functional class=1 indicating a rural freeway.

The average annual daily traffic (AADT) from the RM S database for this link in 2008 is 12,077 vehicles/day.

Growth factors have been developed to factor the 20 08 volume to future years. For example, to factor the 2008 volume to the year 2014, a growth f actor of 1.282 would yield:

2014 volume = 12,077 vehicles/day x 1.282 = 15,48 3 vehicles/dayAppendix C -1 13 

### Exhibit 6: PPSUITE Speed / Emission Estimation Proc edure

Data From PPSUITE Input Files PPSUITE Ana lysis Process Data from Roadway Source ( RMS)

The Following is Performed For Each RMS Roadway Segment

Percent Pattern Distributions Expand to 24 ho urly volumes RMS AWDT Adjusted Vol umes

Apply VMT Adjustments Adjust Volumes for Peak Spre ading (V/C thresholds for spreading)

Vehicle Type Patterns Disaggregate to Vehicle Type RMS Truck Percentages

Transit Data

School Bus Data

Calculate Link & Signal Capacities Roadway Att ributes (Lanes, FC code, UR code) Speed/Capacity Lookup Table

Calculate Link Calculate Midblock Speed Approach Delay

Apply Post Speed VMT Adjustments

Prepare MOVES CDM Files

VHT by Annual RoadType SourceType Hourly Ramp Speed Bin VMT Fracti ons Population Fractions Fractio ns Per VMT
<Optional>

Off-line File Preparation

Vehicle Age Distribution Run MOVES Importer to convert county input data Hourly into MYSQL data forma t Temps/Humidity

I/M

Parameters

Fuel Run MOVES

ParametersAppendix C -1 14

Seasonal Adjustments : PPSUITE takes the input daily volumes from RMS (w hich represents annual average daily traffic (AADT)) and seasonally adjust s the volumes to an average weekday in July. This adjustment utilizes factors developed for each func tional class and urban/rural code. VMT can then be calculated for each link using the adjusted weekday volumes.

Example:

Again, assume the rural freeway link: I-80 segment 2500 in Luzerne County, Pennsylvania. The AADT for this link in 2008 is 12,077 vehicles/day.

Seasonal factors have been developed for urban/rura l code and functional class combinations. For an urban/rural code=1 and a functional class=1, the factor to convert from AADT to an average weekday in July is = 1.15.

Average Weekday July Volume = 12,077 x 1.15 = 13,88 9 vehicles/day.

Total VMT (daily) for this link is calculated as vo lume x distance. The distance of this link as

obtained from RMS is 0.296 miles.

2008 VMT = 13,889 vehicles/day x 0.296 miles = 4,11 1 vehicle-miles / day.

Disaggregation to 24 Hours : After seasonally adjusting the link volume, the v olume is split to each hour of the day. This allows for more accurate speed ca lculations (effects of congested hours) and allows PPSUITE to prepare the hourly VMT and speeds for in put to the MOVES model.

Example:

To support speed calculations and emission estimate s by time of day, the July weekday volume is disaggregated to 24 hourly volumes. Temporal patte rns were previously developed from PennDOT count data and input to PPSUITE. For the I -80 rural freeway link with morning peak volumes similar to evening peak hours (neutral), th e following temporal pattern is applied:

0 1 2 3 4 5 6 7 8 9 101357911131517192123

Hour of DayPercent of Daily

Using the I-80 segment, typical hourly volumes whic h result include: 8-9 a.m. 6.0% x (4,111 vehicle miles/ 0.296mi.) = 833 vehicles/hour (vph) 12-1 p.m. 5.0% x (4,111 vehicle .miles/ 0.296mi. ) = 694 vph 5-6 p.m. 6.3% x (4,111 vehicle miles/ 0.296mi.) = 875 vphAppendix C -1 15

After dividing the daily volumes to each hour of th e day, PPSUITE identifies hours that are unreasonab ly congested. For those hours, PPSUITE then spreads a portion of the volume to other hours within the same peak period, thereby approximating the “peak s preading” that normally occurs in such over-capacit y conditions.

Disaggregation to Vehicle Type : EPA requires VMT estimates to be prepared by sou rce type, reflecting specific local characteristics. As a result, for P ennsylvania’s emission inventory runs, the hourly v olumes are disaggregated to the thirteen MOVES source type s based on count data assembled by PennDOT in

combination with MOVES defaults.

Example:

Disaggregation of the total I-80 VMT to the various source types would include the following:

Total Volume 8-9 am = 833 vph

Source Type Volume 8-9 am: Motorcycle 11 0.5% 4 vph Passenger Car 21 54.7% 456 vph Passenger Truck 31 27.9% 232 vph Light Commercial Truck 32 9.3% 78 vph Intercity Bus 41 0.1% 1 vph Transit Bus 42 0.1% 1 vph School bus 43 0.1% 1 vph Refuse Truck 51 0.0% 0 vph Single Unit Short-haul Truck 52 2.2% 19 vph Single Unit Long-haul Truck 53 0.3% 2 vph Motor Home 54 0.1% 1 vph Combination Short-haul Truck 61 1.9% 16 vph Combination Long-haul Truck 62 2.6% 22 vph



## Speed/Delay Determination

EPA recognizes that the estimation of vehicle speed s is a difficult and complex process. Because emissions are so sensitive to speeds, it recommends special attention be given to developing reasonabl e and consistent speed estimates; it also recommends that VMT be disaggregated into subsets that have roughly equal speed, with separate emission factors for each subset. At a minimum, speeds should be estimated separately by road type.

The computational framework used for this analysis meets and exceeds that recommendation. Speeds are individually calculated for each roadway segment an d hour and include the delays encountered at signal s. Rather than accumulating the roadway segments into a particular road type and calculating an average speed, each individual link hourly speed is represe nted in the MOVES vehicle hours of travel (VHT) by speed bin file. This MOVES input file allows the s pecification of a distribution of hourly speeds.

For example, if 5% of a county’s arterial VHT opera tes at 5 mph during the AM peak hour and the remaining 95% operates at 65 mph, this can be repre sented in the MOVES speed input file. For the model runs, distributions of speeds are input to MO VES by road type and source type by each hour of th e day; VMT and VHT is accumulated by the same groupin gs for the application of the emission factors to produce resulting emission totals.Appendix C -1 16

To calculate speeds, PPSUITE first obtains initial capacities (how much volume the roadway can serve before heavy congestion) and free-flow speeds (spee ds assuming no congestion) from the speed/capacity lookup data. As described in previous sections, th is data contains default roadway information indexe d by the urban/rural code and functional class. For areas with known characteristics, values can be dir ectly coded to the RMS database and the speed/capacity da ta can be overridden. However, for most areas where known information is not available, the speed /capacity lookups provide valuable default information regarding speeds, capacities, signal ch aracteristics, and other capacity adjustment inform ation used for calculating congested delays and speeds. An effort has been made to enhance the RMS data wit h traffic signal locations using other GIS signal dat a available from PennDOT’s Bureau of Highway Safety and Traffic Engineering.

Example:

The speed/capacity lookup table is used to obtain i mportant data used for link speed calculations. For the I-80 link with an urban/rural code = 1 (rur al) and a functional class = 1 (freeway), the lookup table provides information including the fol lowing:

freeflow speed = 65 mph capacity = 1800 vph per lane number of signals = 0 (per RMS linkage to GIS traf fic signal locations)

This information is used along with the physical ch aracteristics of the roadway to calculate the delay (including congestion) to travel this link du ring each hour of the day:

For example: The I-80 link is calculated to have a travel time, including delay of 17.76 seconds

for the 8-9am hour.

Total travel time, in vehicle hours, for the 8-9am hour is calculated as:

VHT (8-9am) = 17.76 seconds x 833vph / 3600 sec/h r = 4.12 vehicle hours.

The result of this process is an estimated average travel time for each hour of the day for each highw ay segment. The average time can be multiplied by the volume to produce vehicle hours of travel (VHT).



## HPMS and VMT Adjustments

Volumes must also be adjusted to account for differ ences with the HPMS VMT totals, as described previously. VMT adjustment factors are provided as input to PPSUITE, and are applied to each of the roadway segment volumes. These factors were develo ped from the latest HPMS download (conducted triennially); however, they are also applied to any future year runs. The VMT added or subtracted to the RMS database assumes the speeds calculated using th e original volumes for each roadway segment for each hour of the day.Appendix C -1 17 Example:

Using the Luzerne County I-80 rural freeway link ex ample, the daily assigned volume is adjusted

to account for reconciliation with the HPMS VMT. R MS VMT (in AADT) for Luzerne County rural freeways totals 962,559 vehicle miles in 2008 . HPMS VMT (in AADT) as supplied by PennDOT and reported to FHWA totals to 990,088 vehi cle miles for the rural freeways. A factor is developed by dividing the HPMS VMT by the RMS VM T:

HPMS adjustment factor for Luzerne County rural fre eways = 990,088 / 962,559 = 1.029.

This factor is held constant in all future years. As an example, this adjustment is made to the I-80 freeway link VMT for the 8-9am hour after spee d calculations are made, and produces the final July weekday VMT for this hour used for Ozone runs.

I-80 Link VMT (8-9am) = 833vph x 0.296 miles x 1 .029 = 254 vehicle miles.



## MOVES Emissions Run

After computing speeds and aggregating VMT and VHT, PPSUITE prepares traffic-related inputs needed to run EPA’s MOVES software, which is used to estim ate emission factors in grams of pollutant per vehicle mile and to produce total emissions based o n input VMT to the model. The process uses MOVES2010a, the officially released emissions model that was obtained directly from EPA.

The MOVES inputs prepared by PPSUITE include the fo llowing:

• Vehicle Type VMT.

• Vehicle Population.

• VMT fractions.

• Average speed distributions.

• Road Type Distribution.

• Ramp Fractions.

These files are text formatted files with a *.csv e xtension. The files are provided as inputs within the MOVES county data importer. In addition the remai ning MOVES input data including temperatures, I/M programs, fuel and vehicle ages are prepared ma nually outside of the PPSUITE process.

The MOVES county importer is run in batch mode. Th is program converts all data files into the MYSQL formats used by the MOVES model. At that point a M OVES run specification file (*.mrs) is created which specifies options and key data locations for the run. MOVES is then executed in batch mode.

MOVES can be executed using either the inventory or rate-based approaches. For this highway emissions inventory, MOVES is applied using the inventory-based approach. Under this method, actual VMT and population are provided as inputs to the mo del; MOVES is responsible for producing the total emissions for the region. Under the rate-based app roach, MOVES would produce emission factors, after which PPSUITE would apply the emission factors to t he link data and calculate total regional emissions

.Appendix C -1 18



## RESOURCES

MOVES model

Modeling Page within EPA’s Office of Mobile Sources Website (http://www.epa.gov/omswww/models.htm) contains a d ownloadable model, MOVES users guide and

other information.

Motor Vehicle Emission Simulator, User Guide for MO VES2010a, EPA-420-B-10-036, August 2010.

Technical Guidance on the Use of MOVES2010 for Emis sion Inventory Preparation in State Implementation Plans and Transportation Conformity , US EPA Office of Air and Radiation, and Office of Transportation and Air Quality, EPA-420-B-10-023 , April 2010.

Policy Guidance on the Use of MOVES2010 for SIP Dev elopment, Transportation Conformity

, and Other Purposes , US EPA Office of Air and Radiation, EPA-420-B-09- 046, December 2009.

Traffic Engineering

Highway Capacity Manual, Transportation Research Board, presents current knowledge and techniques for analyzing the transportation system.

Traffic Data Collection and Factor Development Repo rt, 2008 Data, Pennsylvania Department of Transportation, Bureau of Planning and Research.Appendix C -1 19



## Highway Vehicle Inventory Glossary

AADT: Average Annual Daily Traffic, average of ALL days

.

AWDT: Average Weekday Daily Traffic.

Basic emission rates: MOBILE emission rates based on the applicable Fed eral emission standards and the emission control technologies characterizing th e fleet in various model years.

Emission rate or factor: Expresses the amount of pollution emitted per uni t of activity. For highway vehicles, usually in grams of pollutant emitted per mile driven.

FC: Functional code, applied in data management to roa d segments to identify their type (freeway, local, etc.).

Fuel volatility: The ability of fuel components to evaporate, thus ente ring the atmosphere as pollution. Fuel volatility is usually measured as Reid Vapor P ressure (RVP) in pounds per square inch. The lower the RVP, the less volatile the fuel.

Growth factor: Factor used to convert volumes to future years.

HPMS: Highway Performance Monitoring System, PENNDOT’s official source of highway information

and a subset of RMS.

I/M: Vehicle emissions inspection/maintenance programs ensure that vehicle emission controls are in good working order throughout the life of the vehic le. The programs require vehicles to be tested for emissions. Most vehicles that do not pass must be repaired.

MOBILE: The model EPA has developed and which Pennsylvania uses to estimate emissions from highway vehicles.

MOVES: The latest model EPA has developed with which Penns ylvania uses to estimate emissions from highway vehicles.

Pattern data: Extrapolations of traffic patterns (such as how tra ffic volume on road segment types varies by time of day, or what kinds of vehicles tend to u se a road segment type) from segments with observed data to similar segments.

PPSUITE: Post-Processor for Air Quality, a set of programs that estimate speeds and processes MOBILE

emission rates.

RMS: Roadway Management System, a database maintained by PENNDOT from traffic counts and field

visits.

Segment (also referred to as link): Division of roadway in the PENNDOT Roadway Manageme nt System. Usually represents 0.5 mile segments of ro adway.

UR: Urban/rural code, applied in data management to id entify whether a road segment is urban, small

urban or rural.Appendix C -1 20

VHT: Vehicle hours traveled

.

VMT: Vehicle miles traveled. In modeling terms, it i s the simulated traffic volumes times link length.

Vehicle Type : One of eight types, distinguished primarily by f uel type and/or weight, used in MOBILE modeling.

Source Type : One of thirteen types, distinguished primarily b y weight, used in MOVES modeling.

Road Type: Functional code, applied in data management to roa d segments to identify their type (rural/urban highways, rural/urban arterials, etc.)

County Data Manager: User interface developed to simplify importing spec ific local data for a single county or a user-defined custom domain without requ iring direct interaction with the underlying MySQL

database.