Population and Activity of On-road Vehicles in MOVES2014

                                   June 2015

                 United States Environmental Protection Agency
                   Office of Transportation and Air Quality
                       Assessment and Standards Division

Table of Contents

1.	Introduction	4
2.	MOVES Vehicle and Activity Classifications	6
2.1.	HPMS Class	6
2.2.	Source Use Types	6
2.3.	Regulatory Classes	7
2.4.	Fuel Types	8
2.5.	Road Types	9
2.6.	Source Classification Codes (SCC)	10
2.7.	Source Bins	11
2.8.	Allowable Vehicle Modeling Combinations	12
2.9.	Default Inputs and Fleet and Activity Generators	14
3.	Data Sources	19
3.1.	VIUS	19
3.2.	Polk NVPP(R) and TIP(R)	19
3.3.	EPA Sample Vehicle Counts	19
3.4.	FHWA Highway Statistics	19
3.5.	FTA National Transit Database	20
3.6.	School Bus Fleet Fact Book	20
3.7.	MOBILE6	20
3.8.	Annual Energy Outlook & National Energy Modeling System	21
3.9.	Transportation Energy Data Book	21
3.10.	FHWA Weigh-in-Motion	21
3.11.	Motorcycle Industry Council Statistical Annual	21
4.	VMT by Calendar Year and Vehicle Type	22
4.1.	Historic Vehicle Miles Traveled (1990 and 1999-2011)	22
4.2.	Projected Vehicle Miles Traveled (2012-2050)	23
5.	Vehicle Populations by Calendar Year	26
5.1.	Historic Source Type Populations (1990 and 1999-2011)	26
5.2.	Projected Vehicle Populations (2012-2050)	32
6.	Fleet Characteristics	34
6.1.	Source Type Definitions	34
6.2.	Sample Vehicle Population	37
7.	Vehicle Characteristics that Vary by Age	51
7.1.	Age Distributions	51
7.2.	Relative Mileage Accumulation Rate	62
8.	VMT Distribution of Source Type by Road Type 	67
9.	Average Speed Distributions	69
9.1.	Light-Duty Average Speed Distributions	69
9.2.	Heavy-Duty Average Speed Distributions	73
10.	Driving Schedules and Ramps	78
10.1.	Driving Schedules	78
10.2.	Ramp Activity	83
11.	Hotelling Activity	84
11.1.	National Default Hotelling Rate	84
11.2.	Hotelling Activity Distribution	86
12.	Temporal Distributions	88
12.1.	VMT Distribution by Month of the Year	89
12.2.	VMT Distribution by Type of Day	90
12.3.	VMT Distribution by Hour of the Day	91
12.4.	Engine Starts and Parking	92
12.5.	Hourly Hotelling Activity	95
12.6.	Single and Multiday Diurnals	98
13.	Geographical Allocation of Activity	99
13.1.	Source Hours Operating Allocation to Zones	99
13.2.	Engine Start Allocations to Zones	100
13.3.	Parking Hours Allocation to Zones	101
14.	Vehicle Mass and Road Load Coefficients	102
14.1.	Source Mass and Fixed Mass Factor	103
14.2.	Road Load Coefficients	104
15.	Air Conditioning Activity Inputs	107
15.1.	ACPenetrationFraction	107
15.2.	FunctioningACFraction	108
15.3.	ACActivityTerms	109
16.	Conclusion and Areas for Future Research	111
17.	Appendix A: Projected Source Type Populations by Year	113
18.	Appendix B: Fuel Type and Regulatory Class Fractions for 1960-1981	115
19.	Appendix C: 1990 Age Distributions	118
19.1.	Motorcycles	118
19.2.	Passenger Cars	118
19.3.	Trucks	118
19.4.	Intercity Buses	119
19.5.	School Buses and Motor Homes	119
19.6.	Transit Buses	119
20.	Appendix D: Driving Schedules and SCC Mappings	121
20.1.	SCC Mappings	121
20.2.	Driving Schedules	122
21.	Appendix E: MOVES2010b Source Masses	126
21.1.	Motorcycles	127
21.2.	Passenger Cars	128
21.3.	General Trucks	128
21.4.	Buses	130
21.5.	Refuse Trucks	132
21.6.	Motor Homes	133
References	135

Introduction
The United States Environmental Protection Agency's Motor Vehicle Emission Simulator, commonly referred to as MOVES, is a set of modeling tools for estimating emissions produced by on-road (cars, trucks, motorcycles, etc.) and nonroad (backhoes, lawnmowers, etc.) mobile sources. MOVES estimates the emissions of greenhouse gases (GHG), criteria pollutants and selected air toxics. The MOVES model is currently the official model for use for state implementation plan (SIP) submissions to EPA and for transportation conformity analyses outside of California.  The model is also the primary modeling tool to estimate the impact of many mobile source regulations on emission inventories.

The MOVES model calculates emission inventories by multiplying emission rates by the appropriate emission-related activity, applying correction (adjustment) factors as needed to simulate specific situations, and then adding up the emissions from all sources (populations) and regions. A useful analogy is that an inventory can be pictured as a stool; the three legs of the stool are the emission rates, activity, and populations.  The emission rates are inputs to the model specified for various "processes" including running exhaust, start exhaust, and a number of evaporative processes, among others. The processes are largely chosen to be causal such that the physical or engineering principles involved in generating those emissions are isolated, which in turn allows research test programs to measure them scientifically.  These processes also define the activity, populations, and technology inputs required.

This report describes the sources and derivation for on-road vehicle population and activity information and associated adjustments as stored in the MOVES2014 default databases. This data has been extensively updated from previous versions of MOVES. Emission rates, correction factor values, and information for nonroad equipment in the default database are described in other MOVES technical reports.

The MOVES2014 default database has a domain that encompasses all on-road (highway) vehicle and nonroad equipment activity and emissions for the entire United States, Puerto Rico, and the Virgin Islands. Properly characterizing emissions from the on-road vehicle subset requires a detailed understanding of the cars and trucks that make up the vehicle fleet and their patterns of operation. The national default activity information in MOVES2014 provides a reasonable basis for estimating national emissions. The most important of these inputs, such as VMT and population estimates, come from long-term systematic national measurements.

However, the uncertainties and variability in the default data contribute to the uncertainty in the resulting emission estimates. In particular, when modellers estimate emissions for specific geographic locations, EPA guidance recommends replacing many of the MOVES fleet and activity defaults with local data. This is especially true for inputs that vary geographically and for inputs where local data is more detailed or up-to-date than that provided in the MOVES defaults. MOVES has been specifically designed to accommodate the input of alternate, user supplied activity data for the most important parameters. EPA's Technical Guidance provides more information on customizing MOVES with local inputs.

Population and activity data is ever changing. As part of EPA's MOVES development process, the model undergoes major updates and review every few years.  As we progress with MOVES, development of fleet and activity inputs (including projections) will continue to be an important area of focus and improvement.

MOVES Vehicle and Activity Classifications
EPA has developed some terminology that is specific to MOVES, particularly related to vehicle classification, such as source use types and regulatory classes. The MOVES terms introduced in this section will be used throughout the report and will be discussed in later sections.
HPMS Class
In this report, MOVES HPMS class refers to one of five categories derived from the categories used in the US Department of Transportation (DOT) Highway Performance Monitoring System (HPMS) vehicle classes used by the Federal Highway Administration (FHWA) in the VM-1 Table of their annual Highway Statistics report.  The five HPMS classes used in MOVES are:  motorcycles (HPMSVTypeID 10), light-duty vehicles (25), buses (40), single unit trucks (50), and combination trucks (60).

Note that in MOVES2014, what we call the HPMS class for light-duty vehicles (25) denotes the sum of the VM-1 values for long wheelbase and short wheelbase light-duty vehicles. HPMSVTypeID 25 is new for MOVES2014 and replaces HPMSVTypeID 20 (passenger cars) and 30 (other two-axle four-tire vehicles) in MOVES2010. As such, in MOVES2014 any VMT input by HPMS class for passenger cars and light-duty trucks must be entered as a combined value in the new HPMSVTypeID 25. This change in HPMS classes has come about as passenger vehicles have evolved over time with the physical characteristics of "cars" and "trucks" becoming less distinct.  In response, DOT has changed the HPMS classification system and MOVES has evolved to reflect this change.

Source Use Types
The primary vehicle classification in MOVES is source use type, or, more simply, source type. Source types are intended to be groups of vehicles with similar activity and usage patterns. On-road source types were categorized from the HPMS classes, but the HPMS vehicle classes were further differentiated into MOVES source types using vehicle characteristics from the US Census Bureau's Vehicle Inventory and Use Survey (VIUS). The MOVES2014 source types are listed in Table 2-1 along with the associated HPMS classes. More detailed source type definitions are provided in Section 5.2.

                   Table 2-1 MOVES2014 On-road Source Types
                                 sourceTypeID
                               Source Type Name
                                  HPMSVTypeID
                                  Description
                                      11
Motorcycles
                                      10
Motorcycles
                                      21
Passenger Cars
                                      25
Light-Duty Vehicles
                                      31
Passenger Trucks (primarily personal use)
                                      25
Light-Duty Vehicles
                                      32
Light Commercial Trucks (primarily non-personal use)
                                      25
Light-Duty Vehicles
                                      41
Intercity Buses (non-school, non-transit)
                                      40
Buses
                                      42
Transit Buses
                                      40
Buses
                                      43
School Buses
                                      40
Buses
                                      51
Refuse Trucks
                                      50
Single Unit Trucks
                                      52
Single Unit Short-haul Trucks
                                      50
Single Unit Trucks
                                      53
Single Unit Long-haul Trucks
                                      50
Single Unit Trucks
                                      54
Motor Homes
                                      50
Single Unit Trucks
                                      61
Combination Short-haul Trucks
                                      60
Combination Trucks
                                      62
Combination Long-haul Trucks
                                      60
Combination Trucks

In MOVES, the distinction between light-duty (LD) and heavy-duty (HD) source types is essential because light- and heavy-duty operating modes were developed differently based on vehicle power and speed. Light-duty vehicles (sourceTypeID 11, 21, 31, and 32) use vehicle specific power (VSP), which is dependent on the measured mass of the test vehicle. Heavy-duty vehicles (sourceTypeID 41, 42, 43, 51, 52, 53, 54, 61, and 62) use scaled tractive power (STP) which is scaled by a fixed mass factor since their emission rates correlates better with absolute vehicle power than vehicle specific power. For more discussion on VSP and STP definitions, please refer to Section 14 of this report and the MOVES2014 reports on light-duty and heavy-duty vehicle emission rate development, respectively.[,]

Regulatory Classes
In contrast to source types, regulatory classes are used to group vehicles subject to similar emission standards. The EPA regulates vehicle emissions based on groupings of technologies and classifications that do not necessarily correspond to DOT activity and usage patterns. To properly estimate emissions, it is critical for MOVES to account for these emission standards, despite the fact that the activity data often uses a different classification scheme. Thus, we must map the two schemas.

The regulatory classes used in MOVES are summarized in Table 2-2 below. The "doesn't matter" regulatory class is used internally in the model if the emission rates for a given pollutant and process are independent of regulatory class. The motorcycle (MC) and light-duty vehicle (LDV) regulatory classes have a one-to-one correspondence with source type. Other source types are allocated between regulatory classes based on gross vehicle weight rating (GVWR), which is a set of eight classes developed by FHWA according to the combined weight of the vehicle and its load. Urban buses have their own regulatory definition, and therefore have an independent regulatory class.

                   Table 2-2 Regulatory Classes in MOVES2014
                                  regClassID
                             Regulatory Class Name
                                  Description
                                       0
Doesn't Matter
Doesn't Matter
                                      10
MC
Motorcycles
                                      20
LDV
Light-Duty Vehicles
                                      30
LDT
Light-Duty Trucks
                                      40
LHD<=10k
Class 2b Trucks with 2 Axles and 4 Tires (8,500 lbs < GVWR <= 10,000 lbs)
                                      41
LHD<=14k
Class 2b Trucks with 2 Axles and at least 6 Tires or Class 3 Trucks (8,500 lbs < GVWR <= 14,000 lbs)
                                      42
LHD45
Class 4 and 5 Trucks (14,00 lbs < GVWR <= 19,500 lbs)
                                      46
MHD
Class 6 and 7 Trucks (19,500 lbs < GVWR < =33,000 lbs)
                                      47
HHD
Class 8a and 8b Trucks (GVWR > 33,000 lbs)
                                      48
Urban Bus
Urban Bus (see CFR Sec. 86.091_2)

The GVWR distinction between LD and HD trucks falls in the midst of FHWA GVWR Class 2.  Trucks of 6,001-8,500 lbs GVWR are sorted into Class 2a, which are considered light-duty vehicles, while vehicles of 8,500-10,000 lbs GVWR are sorted into Class 2b, which are considered heavy-duty vehicles.

In MOVES2014, we have introduced a new regulatory class 40 for vehicles that are in Class 2b, but are classified as passenger truck or light-commercial trucks. These vehicles are regulated as heavy-duty vehicles by the US EPA, but the VMT from Class 2b vehicles with two axles and four tires are included in the light-duty vehicles categories by the FHWA Highway Statistics Report. MOVES assigns operating modes for source types 31 and 32 according to VSP. As such, we created regulatory class 40, so that regulatory class 40 models the emission rates of Class 2b trucks according to VSP-based operating modes, and regulatory class 41 models the emission rates of Class 2b trucks according to STP-based operating modes. Class 2b trucks with two axles and at least six tires (colloquially known as dualies) and Class 3 trucks fall into regulatory class 41 and are only modeled in the   heavy-duty vehicles source types

In summary, the light-duty truck source types (31 and 32) map only to regulatory classes 30 and 40 in MOVES2014, while the heavy-duty vehicle source types (41 and above) map to regulatory classes 41 and above.

Fuel Types
MOVES2014 models vehicles and equipment powered by following fuel types: gasoline, diesel, E-85 (a blend of 85 percent ethanol and 15 percent gasoline), compressed natural gas (CNG), electricity, and liquefied petroleum gas (LPG, only available for nonroad equipment). Note that in some cases, a single vehicle can use more than one fuel; for example, flexible fuel vehicles are capable of running on either gasoline or E-85. Thus, fuel type refers to the capability of the vehicle capability rather than the fuel in the tank.   In MOVES, the fuel actually used depends on a number of factors including the location, year, and month in which the fuel was purchased, as explained in the MOVES2014 technical report on the fuel supply.  The table below summarizes the fuel types available in MOVES.

Table 2-3 A list of allowable fuel types to power vehicles/equipment in MOVES2014
                                  fuelTypeID
                             defaultFormulationID
                                  Description
                                       1
                                      10
Gasoline
                                       2
                                      20
Diesel Fuel
                                       3
                                      30
Compressed Natural Gas (CNG)
                                       4
                                      40
Liquefied Petroleum Gas (LPG)*
                                       5
                                      50
Ethanol (E-85) Capable
                                       9
                                      90
Electricity
               * MOVES2014 only models LPG use in nonroad equipment.

It is important to note that not all fuel type/source type combinations can be modeled in MOVES. That is, MOVES2014 will not model gasoline fueled long-haul combination trucks, gasoline intercity buses, or diesel motorcycles. Transit buses are the only on-road source type that may be modeled using CNG. Similarly, flexible fuel (E85-compatible) and electric vehicles are only modeled for passenger cars, passenger trucks, and light commercial trucks. None of the on-road (highway) source types can be modeled as fueled by LPG. For more information on how MOVES models the impact of fuels on emissions, please see the MOVES documentation on fuel effects.

Road Types
MOVES calculates emissions separately for each of four road types and for "off-network" activity when the vehicle is not moving. It also allows separate output for ramp and non-ramp, as described in Section 10.2 below. The road type codes used in MOVES are listed in Table 2-4. The four MOVES road types (2-5) are aggregations of FHWA functional facility types.

                    Table 2-4 Road Type Codes in MOVES2014
                                  roadTypeID
                                  Description
                             FHWA Functional Types
                                       1
Off Network
Off Network
                                       2
Rural Restricted Access
Rural Interstate
                                       3
Rural Unrestricted Access
Rural Principal Arterial, Minor Arterial, Major Collector, Minor Collector & Local
                                       4
Urban Restricted Access
Urban Interstate & Urban Freeway/Expressway
                                       5
Urban Unrestricted Access
Urban Principal Arterial, Minor Arterial, Collector & Local
                                       6
Rural Restricted without Ramps

                                       7
Urban Restricted without Ramps

                                       8
Rural Restricted only Ramps

                                       9
Urban Restricted only Ramps

                                      100
Nonroad

The MOVES roadtypes are based on two important distinctions in how FWHA classifies roads: 1) urban versus rural roadways are distinguished based on land use and human population density, and 2) unrestricted versus restricted are distinguished based on roadway access--restricted roads require the use of ramps. The urban/rural distinction is used primarily for national level calculations. It allows different default speed distributions in urban and rural settings. Of course, finer distinctions are possible. Users with more detailed information on speeds and acceleration patterns may choose to create their own additional road types, or may run MOVES at project level where emissions can be calculated for individual links.

Source Classification Codes (SCC)
Source Classification Codes (SCC) are used in air quality models, such as the UNC SMOKE model, to unambiguously identify the source of the emissions when generating emission inventories. In MOVES, SCCs are single numerical codes that identify the vehicle type, fuel type, road type, and emission process. The SCCs were redesigned for MOVES2014 to directly relate to the source use types and road types used by MOVES.

The new SCCs retain the previous 10-digit design, but use different numerical combinations to avoid conflicts with existing codes. The new codes use MOVES numerical identification (ID) codes in the following form:

	AAAFVVRRPP, where

   * AAA indicates mobile source (this has a value of 220 for both on-road and nonroad),
   * F indicates the MOVES fuelTypeID value,
   * VV indicates the MOVES sourceTypeID value,
   * RR indicates the MOVES roadTypeID value, and
   * PP indicates the MOVES emission processID value.

Building the new SCC values in this way will allow additional source types, fuel types, road types, and emission processes to be easily added to the list of SCC values as changes are made to future versions of MOVES. Using the mapping described above, modelers can also easily identify the sourceTypeID, fuelTypeID, roadTypeID, and processID of emissions reported by SCC without needing a decoding table. Refer to tables in the MOVES User Guide for the descriptions of the sourceTypeID, fuelTypeID, roadTypeID, and processID values currently used by MOVES.

The explicit coding of fuel type, source type, road type, and emission process also allows the MOVES SCCs to indicate aggregations. For example, a zero code (00) for any of the sourceTypeID, fuelTypeID, roadTypeID, and processID strings that make up the SCC indicates that the reported emissions are an aggregation of all categories of that type.

The SCC values used in previous versions of MOVES do not have a one-to-one correspondence with the new SCC values. However, MOVES2014 has the capability to report results by regulatory class as well as by SCC, which will aid in comparing SCC results from earlier versions of MOVES. All feasible SCC values are listed in the SCC table within the default database.

Source Bins
To estimate emissions, MOVES must know the emission-related characteristics of the vehicle such as the type of fuel that it is designed to use and the emission standards it is subject to. Therefore, we group vehicles into source bins that classify a vehicle by discriminators relevant for emissions and energy calculations, including fuel type, regulatory class, and model year group. Each sourceBinID is a unique 19-digit identifier in the following form:

 1FFEERRMM0000000000, where

         *       1 is a placeholder,
         *       FF is a MOVES fuelTypeID,
         *       EE is a MOVES engTechID,
         *       RR is a MOVES regClassID,
         *       MM is a MOVES shortModYrGroupID, and
         *       10 trailing zeros for future characteristics.

A mapping of model year to model year groups is stored in the PollutantProcessModelYear table.  Distributions of fuel and engine technologies and regulatory class are stored by model year in the SampleVehiclePopulation table. The MOVES Source Bin Distribution Generator combines information from these two tables to create a detailed SourceBinDistribution. These bins may vary by pollutant and process as indicated in the SourceTypePolProcess table. In general, fuel type and model year group are relevant for all emission calculations, but the relevance of regulatory class and model year group depend on the pollutant and process being modeled.  Since MOVES2014 can produce results by various vehicle classifications -- source type, SCC, or regulatory class -- the mapping between SourceBinDistribution and SampleVehiclePopulation differs depending on the output selected.

       Table 2-5 Data Tables Used to Allocate Source Type to Source Bin
Generator Table Name
Key Fields*
Additional Fields
Notes
SourceTypePolProcess

sourceTypeID
polProcessID
isRegClassReqd
isMYGroupReqd
Indicates which pollutant-processes the source bin distributions may be applied to and indicates which discriminators are relevant for each sourceTypeID and polProcessID (pollutant/process combination)
PollutantProcessModelYear
polProcessID
modelYearID
modelYearGroupID
Assigns model years to appropriate model year groups for each polProcessID.
SampleVehiclePopulation
sourceTypeID
modelYearID
fuelTypeID
engTechID
regClassID

stmyFuelEngFraction
stmyFraction
Includes fuel type and regulatory class fractions for each source type and model year, even for some source type/fuel type combinations that do not currently have any appreciable market share (i.e. electric cars). This table provides defaults for the Alternative Vehicle Fuel & Technology (AFVT) importer, and is used to determine reg class fractions when users modify alternative fuel vehicle fleet fractions.
* In these tables, the sourceTypeID and modelYearID are combined into a single sourceTypeModelYearID.

While details of the SourceTypePolProcess and PollutantProcessModelYear tables are discussed in the reports on the development of the light- and heavy-duty emission rates, the SampleVehiclePopulation (SVP) table is a topic for this report and is discussed in Section 5.2.

Allowable Vehicle Modeling Combinations
MOVES2014 allows users to model most combinations of source type, regulatory class, and fuel type. However, each combination must have accompanying emission rates; combinations that lack emissions testing or have negligible market share cannot be directly modeled in MOVES2014.   Table 2-6 is a matrix summarizing the allowable source type-fuel type combinations. Most of the gasoline and diesel combinations exist with a few notable exceptions, but options for alternative fuels are limited as discussed earlier in Section 2.4.

MOVES also stores regulatory class distributions by source type in the SampleVehiclePopulation table. Table 2-7 summarizes the allowable source type-regulatory class combinations in MOVES2014. Any vehicles in regulatory class 40 and less are considered light-duty while any vehicles in regulatory class 41 and greater are considered heavy-duty. Similarly, source types 32 and less are considered light-duty and source types 41 and above are considered heavy-duty.

 Table 2-8 joins together the information in the two matrices about source type, fuel type, and regulatory class combinations in MOVES2014. Each source type-fuel type combination contains all regulatory classes listed, except for gasoline transit buses, which have been called out separately.
Table 2-6 Matrix of the allowable source type-fuel type combinations in MOVES2014 (allowable combinations are marked with an X)

                               Source Use Types

                                  Motorcycles
                                 Passenger Cars
                                Passenger Trucks
                            Light Commercial Trucks
                                Intercity Buses
                                 Transit Buses
                                  School Buses
                                 Refuse Trucks
                         Short-Haul Single Unit Trucks
                          Long-Haul Single Unit Trucks
                                  Motor Homes
                         Short-Haul Combination Trucks
                          Long-Haul Combination Trucks
                                  Fuel Types
                                      11
                                      21
                                      31
                                      32
                                      41
                                      42
                                      43
                                      51
                                      52
                                      53
                                      54
                                      61
                                      62
Gasoline
                                       1
                                       X
                                       X
                                       X
                                       X

                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X

Diesel
                                       2

                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
CNG
                                       3

                                       X

E85
                                       5

                                       X
                                       X
                                       X

Electricity
                                       9

                                       X
                                       X
                                       X

Table 2-7 Matrix of the allowable source type-regulatory class combinations in MOVES2014 (allowable combinations are marked with an X)

                               Source Use Types

                                  Motorcycles
                                 Passenger Cars
                                Passenger Trucks
                            Light Commercial Trucks
                                Intercity Buses
                                 Transit Buses
                                  School Buses
                                 Refuse Trucks
                         Short-Haul Single Unit Trucks
                          Long-Haul Single Unit Trucks
                                  Motor Homes
                         Short-Haul Combination Trucks
                          Long-Haul Combination Trucks
                              Regulatory Classes
                                      11
                                      21
                                      31
                                      32
                                      41
                                      42
                                      43
                                      51
                                      52
                                      53
                                      54
                                      61
                                      62
MC
                                      10
                                       X

LDV
                                      20

                                       X

LDT
                                      30

                                       X
                                       X

LHD<=10k
                                      40

                                       X
                                       X

LHD<=14k
                                      41

                                       X

                                       X
                                       X
                                       X
                                       X
                                       X

LHD45
                                      42

                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X

MHD67
                                      46

                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
HHD8
                                      47

                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
                                       X
Urban Bus
                                      48

                                       X

Table 2-8 A summary of source type, fuel type, and regulatory class combinations in MOVES2014
                                 sourceTypeID
                                  fuelTypeID
                                  regClassID
                                      11
                                                                              1
                                                                             10
                                      21
                                                                     1, 2, 5, 9
                                                                             20
                                      31
                                                                     1, 2, 5, 9
                                                                         30, 40
                                      32
                                                                     1, 2, 5, 9
                                                                         30, 40
                                      41
                                                                              2
                                                                 41, 42, 46, 47
                                      42
                                                                              1
                                                                     42, 46, 47

                                                                           2, 3
                                                                             48
                                      43
                                                                           1, 2
                                                                 41, 42, 46, 47
                                      51
                                                                           1, 2
                                                                 41, 42, 46, 47
                                      52
                                                                           1, 2
                                                                 41, 42, 46, 47
                                      53
                                                                           1, 2
                                                                 41, 42, 46, 47
                                      54
                                                                           1, 2
                                                                 41, 42, 46, 47
                                      61
                                                                           1, 2
                                                                         46, 47
                                      62
                                                                              2
                                                                         46, 47

Default Inputs and Fleet and Activity Generators
Population and activity data are critical inputs for calculating emission inventories from emissions processes such as running exhaust, start exhaust, and evaporative emissions. In MOVES, most running emissions are distinguished by operating modes, depending on road type and vehicle speed. Start emissions are determined based on the time a vehicle has been parked prior to the engine starting ("soak"). Evaporative emissions modes are affected by vehicle operation and the time that vehicles are parked.  Emission rates are further categorized by source bins with similar fuel type, regulatory classification, and other vehicle and activity characteristics.

Because of these distinctions, MOVES calculators require information on vehicle population and activity at a very fine scale.  In project-level modeling, this detailed information may be available and manageable.  However, in other cases the fleet and activity data used in the MOVES calculators must be generated from inputs in a condensed or more readily available format. MOVES uses "generators" to create fine-scale information from user inputs and MOVES defaults.

The MOVES Total Activity Generator (TAG) estimates hours of vehicle activity using vehicle miles travelled (VMT) and speed information to transform VMT into source hours operating (SHO). Other types of vehicle activity are generated by applying appropriate factors to vehicle populations. Vehicle starts, extended idle hours, and source hours (including hours operating and not-operating) are also generated. The default database for MOVES2014 contains national estimates for VMT, vehicle population, and vehicle age distributions for every possible analysis year (1990 and 1999-2050). For national inventory runs, annual national activity is distributed temporally and spatially using allocation factors. A separate version of the TAG creates inputs for the runs that only generate emission rates.

The Source Bin Distribution Generator (SBDG) uses information on fuel type fractions, regulatory class distributions, and similar information to estimate the number of vehicles belonging to each source bin as a function of source type and model year. The SBDG maps the activity data (by source types) to sourcebins which map directly to the MOVES emission rates.

There are a number of MOVES modules that generate operating mode distributions based on vehicle activity inputs.  The Rates Operating Mode Distribution Generator and the Link Operating Mode Distribution Generator use information on speed distributions and driving patterns (driving schedules) to develop operating mode fractions for each source type, road type, and time of day.  Similarly, the Evaporative Emissions Operating Mode Generator and the Start Operating Mode Distribution Generator use MOVES inputs to develop operating mode distributions for starts and vapor venting.  The details of each these generators and other MOVES2014 algorithms are described in the MOVES2014 Module Reference.

This report documents the sources and calculations used to produce the default population and activity data in the MOVES2014 database used to compute national level emissions based on defaults for individual counties, months, day types, and hours of the day. In particular, this report will describe the data used to fill the tables listed in Table 2-9.

Table 2-9 MOVES Database Elements Covered in this Report
Database Table Name
Content Summary
Report Sections
AvgSpeedDistribution
Distribution of time among average speed bins
Section 9
DayVMTFraction
Distribution of VMT between weekdays and weekend days
Section 12
DriveSchedule
Average speed of each drive schedule
Section 10
DriveScheduleAssoc
Mapping of which drive schedules are used for each combination of source type and road type
Section 10
DriveScheduleSecond
Speed for each second of each drive schedule
Section 10
FuelType
Broad fuel categories that indicate the fuel vehicles are capable of using.
Section 2
HotellingActivityDistribution
Distribution of hotelling activity to the various operating modes
Section 11
HotellingCalendarYear
Rate of hotelling hours per rural restricted access VMT
Section 11
HourVMTFraction
Distribution of VMT among hours of the day
Section 12
HPMSVtypeYear
Annual VMT by HPMS vehicle types
Section 4
MonthGroupHour
Coefficients to calculate air conditioning demand as a function of heat index
Section 15
MonthVMTFraction
Distribution of annual VMT among months
Section 12
PollutantProcessModelYear
Assigns model years to appropriate groupings, which vary by pollutant and process
Section 4
RegulatoryClass
Sorts vehicles into weight-rating based groups in which emission regulations are applied
Section 2
RoadOpModeDistribution
Operating mode distributions by source type, road type, and speed bin
Section 10
RoadType
Distinguishes roadways by population density of geographic area and by type of access, particularly the use of ramps for entrance and exit.
Section 2
RoadTypeDistribution
Distribution of VMT among road types
Section 8
SampleVehicleDay
Identifies vehicles in the SampleVehicleTrip table
Section 12
SampleVehiclePopulation
Fuel type and regulatory class distributions by source type and model year.
Section 4
SampleVehicleTrip
Trip start and end times used to determine vehicle start and soak times
Section 12
SCC
Source Classification Codes that identify the vehicle type, fuel type, road type and emission process in MOVES output.
Section 2
SourceBinDistribution
Distribution of population among different vehicle sub-types (source bins)
Section 4
SourceTypeAge
Rate of survival to subsequent age, relative mileage accumulation rates, and fraction of functional air conditioning equipment
Section 7
Section 15
SourceTypeAgeDistribution
Distribution of vehicle population among ages
Section 7
SourceTypeHour
The distribution of total daily hotelling among hours of the day
Section 12
SourceTypeModelYear
Prevalence of air conditioning equipment
Section 15
SourceTypePolProcess

Indicates which sourcebin discriminators are relevant for each source type and pollutant/process
Section 4
SourceTypeYear
Vehicle counts by year
Section 5
SourceUseType
Mapping from HPMS class to source type, including source type names
Section 2
SourceUseTypePhysics
Road load coefficients and vehicle masses for each source type used to calculate Vehicle Specific Power and Scaled Tractive Power
Section 14
Zone
Allocation of activity to zone (county)
Section 13
ZoneRoadType
Allocation of driving time to zone (county) and road type
Section 13

Data Sources
A number of organizations collect data relevant to this report. The most important sources used to populate the vehicle population and activity portions of the MOVES database are described here. These sources are referred to throughout this document by the abbreviated name given in this description, but the reference citation is only given here.
VIUS
Until 2002, the US Census Bureau conducted the Vehicle Inventory and Use Survey (VIUS) to collect data on the physical characteristics and activity of US trucks every five years. The survey is a sample of private and commercial trucks that were registered in the United States as of July of the survey year. The survey excludes automobiles, motorcycles, government-owned vehicles, ambulances, buses, motor homes, and nonroad equipment.

For MOVES, VIUS provides information to characterize trucks by source type and to estimate age, fuel type, and regulatory class distributions as well as relative mileage accumulation rates. MOVES2014 uses data from both the 1997 and 2002 surveys. While the survey includes a large number of vehicles and was designed to be representative of the US fleet, information on model year is not available for many of the older trucks. Thus, the distribution data for many older model years is sparse and sometimes erratic. Note that the Census Bureau discontinued VIUS in 2002, although there has been discussion recently about reinitiating the survey.
Polk NVPP(R) and TIP(R)
Acquired by IHS in July 2013, R.L. Polk & Co. was a private company providing automotive information services. The company maintained two databases relevant for MOVES: the National Vehicle Population Profile (NVPP(R)) and the Trucking Industry Profile (TIP(R)Net) Vehicles in Operation database. The first focused on light-duty cars and trucks, the second focused on medium and heavy-duty trucks. Both compiled data from state vehicle registration lists. For MOVES2014, EPA used NVPP(R) and TIP(R) datasets purchased for 1999 and 2011. Polk/IHS data was used in determining vehicles populations by age, fuel type, and regulatory class. At the time of these EPA data purchases Polk was independently operated, so we will continue to refer to these datasets under the Polk name in this report.
EPA Sample Vehicle Counts
 Neither VIUS nor the Polk dataset contained enough information separately to develop distributions by regulatory class, fuel type, and age for each vehicle source type in MOVES, so EPA combined these datasets, and incorporated additional data sources to cover vehicles types, such as motorcycles, buses, and motor homes that were excluded from either the VIUS or Polk datasets. The resulting sample vehicle counts dataset is the basis for the MOVES2014 SampleVehiclePopulation table and the 2011 age distributions. More details on how we constructed the Sample Vehicle Counts dataset can be found in Section 5.2.
FHWA Highway Statistics
Each year the US DOT Federal Highway Administration's (FHWA) Office of Highway Policy Information publishes Highway Statistics. This volume summarizes a vast amount of roadway and vehicle data from the Highway Performance Monitoring System, a national information system that collects data from states and other sources on many facets of the US roadway system.

In MOVES2014, vehicle miles traveled (VMT) and vehicle population data for the historic years 1990 and 1999-2011 come from four tables in Highway Statistics: MV-1, MV-10, VM-1, and VM-2, which we will reference by table name. For some years, the VMT values were revised by FHWA in subsequent publications. Table 3-1 summarizes the data source and revision date we used for each historical year.

  Table 3-1 Corresponding Highway Statistics Data Source for Historical Years
                                     Year
              FHWA Publication Source (Publication/Revision Date)
                                     1990
Highway Statistics 1991 (October 1992)
                                     1999
Highway Statistics 1999 (October 2000)
                                     2000
Highway Statistics 2000 (April 2011)
                                     2001
Highway Statistics 2001 (April 2011)
                                     2002
Highway Statistics 2002 (April 2011)
                                     2003
Highway Statistics 2003 (April 2011)
                                     2004
Highway Statistics 2004 (April 2011)
                                     2005
Highway Statistics 2005 (April 2011)
                                     2006
Highway Statistics 2006 (April 2011)
                                     2007
Highway Statistics 2007 (April 2011)
                                     2008
Highway Statistics 2008 (April 2011)
                                     2009
Highway Statistics 2010 (December 2012)
                                     2010
Highway Statistics 2010 (December 2012)
                                     2011
Highway Statistics 2011 (March 2013)

FTA National Transit Database
The US DOT, Federal Transit Administration (FTA) summarizes financial and operating data from mass transit agencies across the country in the National Transit Database (NTD). For MOVES2014, we used 1999-2011 vehicle counts from the NTD Revenue Vehicle Inventory for motor buses (MB) to determine fuel type distributions and populations.
School Bus Fleet Fact Book
The School Bus Fleet Fact Book includes estimates, by state, of the number of school buses and total miles traveled. The Fact Book is published by Bobit Publications. School bus mileage accumulation rates came from the 1997 Fact Book, originally used in MOBILE6. We have used 1999-2011 sales data from the 2009 and 2012 Fact Book to calculate age distributions.
MOBILE6
MOBILE6 was a precursor to MOVES used to estimate highway vehicle emissions. In some cases, we have used estimates from MOBILE6 model with only minor adaptation. In particular, we used MOBILE6 data for some relative mileage accumulation rates, air conditioning usage rates, and driving schedules.
The MOBILE6 data is documented in technical reports, particularly M6.FLT.002, Update of Fleet Characterization Data for Use in MOBILE6 - Final Report. Additional MOBILE6 documentation is available online.
Annual Energy Outlook & National Energy Modeling System
The Annual Energy Outlook (AEO) describes Department of Energy forecasts for future energy consumption. The National Energy Modeling System (NEMS) is used to generate these projections based on economic and demographic forecasts. Vehicle sales and miles travelled are included in the projections because they strongly influence fuel consumption. Therefore, the AEO is an important source of future projections in MOVES. For MOVES2014, we used AEO2014 to forecast VMT and vehicle populations in years 2012-2050.
Transportation Energy Data Book
Each year, Oak Ridge National Laboratory produces the annual Transportation Energy Data Book (TEDB) for the Department of Energy. This book summarizes transportation and energy data from a variety of sources, including EPA, FHWA, Polk, and Ward's Automotive, Inc. For MOVES we used information for estimating vehicle sales and survival fractions for historic years 1990 and 1999-2011 from TEDB Edition 32, published in 2013.
FHWA Weigh-in-Motion
FHWA compiles truck weight data by axle configuration and roadway type from individual states' Weigh-in-Motion (WIM) programs. The average weight for single unit trucks and combination trucks was determined from FHWA's Vehicle Travel Information System (VTRIS) W-3 Tables using data collected in 2011.
Motorcycle Industry Council Statistical Annual
The Motorcycle Industry Council (MIC) collects data on sales, ownership, and activity trends each year. MIC's Statistical Annual summarizes this data, which we used in MOVES2014, particularly the 1999-2011 sales of highway motorcycles.

VMT by Calendar Year and Vehicle Type
For national level calculations, MOVES calculates source operating hours from national VMT by vehicle type. The default database contains national VMT estimates for all analysis years, which include 1990 and 1999-2050. Years 1991-1998 are excluded because there is no regulatory requirement to analyze them and including them would increase model complexity. Calendar year 1990 continues to be a base year because of the Clean Air Act Amendments of 1990.

The national VMT estimates are stored in the HPMSVTypeYear table, which includes three data fields:  HPMSBaseYearVMT (discussed below), baseYearOffNetVMT, and VMTGrowthFactor. Off Network VMT refers to the portion of activity that is not included in travel demand model networks or any VMT that is not otherwise reflected in the other four road types. The field baseYearOffNetVMT is provided in case it is useful for modeling local areas. However, the reported HPMS VMT values, used to calculate the national averages discussed here, are intended to include all VMT. Thus, for MOVES2014 national defaults, the baseYearOffNetVMT is zero for all vehicle types. Additionally, the VMTGrowthFactor field is not used in MOVES2014 and is set to zero for all vehicle types.

   Historic Vehicle Miles Traveled (1990 and 1999-2011)
The HPMSBaseYearVMT field stores the total national VMT for each HPMS vehicle type for all analysis years. For historical years 1990 and 1999-2011, the VMT is derived from the FHWA VM-1 tables. In reporting years 2007 and later, the VM-1 data use an updated methodology with different HPMS vehicle type categories. The current HPMS categories are Light-Duty (Short Wheelbase), Light-Duty (Long Wheelbase), Motorcycles, Buses, Single Unit Trucks, and Combination Trucks. Because MOVES categorizes light-duty source types based on vehicle type and not wheelbase length, the short and long wheelbase categories are combined into a single category of Light-Duty Vehicles (HPMSVTypeID 25). Internally, the MOVES Total Activity Generator allocates this VMT to MOVES source types and ages using vehicle populations, age distributions and relative mileage accumulation rates.

For years prior to 2007, the VM-1 data with historical vehicle type groupings needed to be adjusted for consistency. In early 2011, the FHWA released such adjusted VMT data for years 2000-2006 to match the new category definitions. Shortly afterward, the agency replaced these adjusted numbers with the unadjusted VMT data stating, "[FHWA] determined that it is more reliable to retain the original 2000-2006 estimates because the information available for those years does not fully meet the requirements of the new methodology." However, lacking a better adjustment methodology, we used the retracted FHWA-adjusted values as the VMT for 2000-2006.

This left two years, 1990 and 1999, that needed to be adjusted to be consistent with the new HPMS vehicle categories. These adjustments were made using the average ratio of the methodology change for each vehicle category. This was found by dividing the FHWA-adjusted VMT for each vehicle category by the original VMT for each year 2000-2006 and then calculating the average ratio for each category. This ratio was then applied to the corresponding VMT values reported in VM-1 for 1990 and 1999. Since FHWA's adjustments conserved the original total VMT estimates, we normalized our adjusted values such that the original total VMT for the years were unchanged.

The resulting values for historic years by HPMS Vehicle Class are listed in Table 4-1. The VMT for 1990 and 1999 were EPA-adjusted from VM-1, 2000-2006 were FHWA-adjusted, and 2007-2011 were unadjusted, other than the simple combination of the short and long wheelbase classes into light-duty vehicles.

    Table 4-1 Historic Year VMT by HPMS Vehicle Class in Millions of Miles
                                     Year
                                  Motorcycles
                              Light-Duty Vehicles
                                     Buses
                              Single Unit Trucks
                              Combination Trucks
                                     1990
                                    11,404
                                   1,943,197
                                    10,279
                                    70,848
                                    108,624
                                      ...

                                     1999
                                    13,619
                                   2,401,408
                                    14,853
                                    100,534
                                    160,921
                                     2000
                                    12,175
                                   2,458,221
                                    14,805
                                    100,486
                                    161,238
                                     2001
                                    11,120
                                   2,499,069
                                    12,982
                                    103,470
                                    168,969
                                     2002
                                    11,171
                                   2,555,467
                                    13,336
                                    107,317
                                    168,217
                                     2003
                                    11,384
                                   2,579,194
                                    13,381
                                    112,723
                                    173,539
                                     2004
                                    14,975
                                   2,652,092
                                    13,523
                                    111,238
                                    172,960
                                     2005
                                    13,773
                                   2,677,641
                                    13,153
                                    109,735
                                    175,128
                                     2006
                                    19,157
                                   2,680,535
                                    14,038
                                    123,318
                                    177,321
                                     2007
                                    21,396
                                   2,691,034
                                    14,516
                                    119,979
                                    184,199
                                     2008
                                    20,811
                                   2,630,213
                                    14,823
                                    126,855
                                    183,826
                                     2009
                                    20,822
                                   2,633,248
                                    14,387
                                    120,207
                                    168,100
                                     2010
                                    18,513
                                   2,648,457
                                    13,770
                                    110,738
                                    175,789
                                     2011
                                    18,500
                                   2,646,641
                                    13,783
                                    103,515
                                    163,692

Projected Vehicle Miles Traveled (2012-2050)
The previous section describes historic fleet VMT. This section presents how EPA projected those values into the future. The VMT growth in years beyond 2011 is based on the VMT projections as described in AEO2014. Due to differences in methodology, the absolute VMT values presented in AEO differ slightly from the HPMS values in VM-1 where the analysis years overlap. Therefore, the projections in AEO were not used directly. Instead, percent changes from year to year in the projected values were calculated and applied to the HPMS data. Since AEO2014 only projects out to 2040, VMT for years 2041-2050 were assumed to continue to grow at the average growth rate over 2031-2040.

A mapping between the two data sources was necessary because the vehicle categories differed between AEO and HPMS. AEO's light-duty category was mapped to both the combined HPMS light-duty and the motorcycle categories. Motorcycles were included here because they were not explicitly accounted for elsewhere in AEO. Since buses span a large range of heavy-duty vehicles and activity, the combination of AEO's light medium, medium, and heavy heavy-duty categories was mapped to the HPMS bus category. AEO's light medium and medium heavy-duty categories were combined for mapping to the HPMS single unit truck category, and AEO's heavy heavy-duty category was mapped to the HPMS combination truck category.

The percent growth changes over time from the groupings described above were calculated and applied by HPMS category to the 2011 base year VMT from VM-1. The resulting values are presented in Table 4-2 below.

Table 4-2 VMT projections for 2012-2050 by HPMS Vehicle Class in Millions of Miles
                                     Year
                                  Motorcycles
                              Light-Duty Vehicles
                                     Buses
                              Single Unit Trucks
                              Combination Trucks
                                     2012
                                    18,776
                                   2,686,152
                                    13,384
                                    103,284
                                    157,396
                                     2013
                                    19,030
                                   2,722,469
                                    13,954
                                    108,811
                                    163,467
                                     2014
                                    19,073
                                   2,728,546
                                    14,374
                                    113,054
                                    167,837
                                     2015
                                    19,162
                                   2,741,392
                                    14,991
                                    118,343
                                    174,804
                                     2016
                                    19,375
                                   2,771,828
                                    15,612
                                    123,348
                                    181,988
                                     2017
                                    19,590
                                   2,802,578
                                    16,036
                                    126,693
                                    186,928
                                     2018
                                    19,756
                                   2,826,337
                                    16,325
                                    128,737
                                    190,433
                                     2019
                                    19,931
                                   2,851,349
                                    16,609
                                    130,692
                                    193,905
                                     2020
                                    20,107
                                   2,876,481
                                    16,906
                                    132,833
                                    197,484
                                     2021
                                    20,284
                                   2,901,914
                                    17,222
                                    135,237
                                    201,214
                                     2022
                                    20,454
                                   2,926,116
                                    17,550
                                    137,759
                                    205,076
                                     2023
                                    20,627
                                   2,950,908
                                    17,877
                                    140,171
                                    208,983
                                     2024
                                    20,807
                                   2,976,667
                                    18,173
                                    142,243
                                    212,579
                                     2025
                                    20,997
                                   3,003,914
                                    18,495
                                    144,418
                                    216,551
                                     2026
                                    21,205
                                   3,033,572
                                    18,799
                                    146,389
                                    220,329
                                     2027
                                    21,426
                                   3,065,195
                                    19,052
                                    147,999
                                    223,510
                                     2028
                                    21,662
                                   3,099,033
                                    19,277
                                    149,382
                                    226,348
                                     2029
                                    21,897
                                   3,132,690
                                    19,509
                                    150,824
                                    229,268
                                     2030
                                    22,133
                                   3,166,361
                                    19,765
                                    152,391
                                    232,509
                                     2031
                                    22,378
                                   3,201,376
                                    20,005
                                    153,916
                                    235,518
                                     2032
                                    22,625
                                   3,236,805
                                    20,198
                                    155,034
                                    237,990
                                     2033
                                    22,867
                                   3,271,436
                                    20,429
                                    156,435
                                    240,929
                                     2034
                                    23,086
                                   3,302,691
                                    20,725
                                    158,246
                                    244,678
                                     2035
                                    23,293
                                   3,332,329
                                    21,017
                                    159,910
                                    248,437
                                     2036
                                    23,493
                                   3,360,885
                                    21,308
                                    161,452
                                    252,265
                                     2037
                                    23,687
                                   3,388,760
                                    21,600
                                    162,945
                                    256,123
                                     2038
                                    23,880
                                   3,416,287
                                    21,887
                                    164,353
                                    259,948
                                     2039
                                    24,060
                                   3,442,035
                                    22,146
                                    165,603
                                    263,426
                                     2040
                                    24,217
                                   3,464,551
                                    22,417
                                    166,905
                                    267,050
                                     2041
                                    24,436
                                   3,495,877
                                    22,701
                                    168,431
                                    270,775
                                     2042
                                    24,657
                                   3,527,485
                                    22,989
                                    169,970
                                    274,552
                                     2043
                                    24,880
                                   3,559,380
                                    23,280
                                    171,524
                                    278,381
                                     2044
                                    25,105
                                   3,591,563
                                    23,575
                                    173,091
                                    282,264
                                     2045
                                    25,332
                                   3,624,036
                                    23,874
                                    174,673
                                    286,201
                                     2046
                                    25,561
                                   3,656,804
                                    24,176
                                    176,270
                                    290,193
                                     2047
                                    25,792
                                   3,689,868
                                    24,483
                                    177,881
                                    294,241
                                     2048
                                    26,025
                                   3,723,230
                                    24,793
                                    179,507
                                    298,345
                                     2049
                                    26,261
                                   3,756,894
                                    25,107
                                    181,147
                                    302,507
                                     2050
                                    26,498
                                   3,790,863
                                    25,425
                                    182,803
                                    306,726

Vehicle Populations by Calendar Year
MOVES uses vehicle populations to characterize emissions activity that is not directly dependent on VMT. These data are also used to allocate VMT from HPMS class to source type and age (for more details, see Section 7). The default database stores historic estimates and future projections of total US vehicle populations in 1990 and 1999-2050 by source type. All of these values have been updated in MOVES2014 with improved data sources. The MOVES database stores this information in the SourceTypeYear table, which has three data fields: sourceTypePopulation, salesGrowthFactor, and migrationRate. However, the salesGrowthFactor and migrationRate fields are not used in MOVES2014.

Historic Source Type Populations (1990 and 1999-2011)
MOVES populations for calendar years 1990 and 1999-2011 are derived top-down from registration data in Table MV-1 of the Federal Highway Administration's annual Highway Statistics report. In this table, vehicles are separated into four general vehicle categories: motorcycles, passenger cars, trucks, and buses. These categories include government vehicles and vehicles in Puerto Rico but do not account for vehicles in the Virgin Islands due to their relatively small effects on national population estimates. Motorcycle and car data were used without adjustment, but since MOVES populations are input by source type, allocations within the general categories of trucks and buses were necessary, as shown in Figure 5-1.

Figure 5-1 Conceptual map of allocating FHWA MV-1 vehicle registration estimates to MOVES source types

Trucks were separated into single unit and combination trucks using registration data in the Highway Statistics VM-1 Table. The remaining MV-1 truck registrations were allocated to the light-duty trucks. Single unit and combination trucks were further allocated among their respective source types using the EPA sample vehicle counts data. Since we only had sample vehicle counts for calendar years 1999 and 2011, the 2000-2010 distributions among source types within the general truck categories were linearly interpolated between 1999 and 2011 rather than using the predictions for these years as in MOVES2010b. This ensured that every source type population would more or less track its general MV-1 population, as shown for example in for allocating between short-haul and long-haul combination trucks below (see Figure 5-2). This linear interpolation method was also used for single unit (see Figure 5-3) and light-duty truck source types (see Figure 5-4). Car and motorcycle populations are reported directly in MV-1 and thus were not subject to linear interpolation adjustments.

  Figure 5-2 Combination truck source type populations interpolated 1999-2011

  Figure 5-3 Single unit truck source type populations interpolated 1999-2011

Figure 5-4 Light-duty vehicle source type populations; light trucks interpolated 1999--2011

              Figure 5-5 Bus source type populations in MOVES2014

Buses were allocated in a similar fashion as trucks, but using different data sources. School bus estimates for all years 1999-2011 were taken from the Highway Statistics Table MV-10 and transit bus estimates for these years were taken from the National Transit Database (NTD) compiled by the Federal Transit Administration. The remainder of MV-1 bus registrations were allocated to the intercity bus source type. Since school and transit bus registrations in Puerto Rico were not readily available, we estimated them by multiplying the US transit or school bus registrations by the ratio of bus registrations in Puerto Rico to the total MV-1 bus registrations. MOVES2014 bus populations are shown in Figure 5-5. Note that the precipitous drop in bus populations from 2010 to 2011 is reflected in the MV-1 bus registration data published by FHWA, which has been used in MOVES2014 without adjustment.
Table 5-1 Historic Source Type Populations for Calendar Years 1990 and 1999-2011 (in thousands)
                                     Year
                                  Motorcycle
                                 Passenger Car
                                Passenger Truck
                            Light Commercial Truck
                                 Intercity Bus
                                  Transit Bus
                                  School Bus
                                 Refuse Truck
                         Single Unit Short-haul Truck
                          Single Unit Long-haul Truck
                                  Motor Home
                         Combination Short-haul Truck
                          Combination Long-haul Truck
                                     1990
                                     4,281
                                    145,112
                                    27,700
                                     9,903
                                      60
                                      59
                                      511
                                      67
                                     3,870
                                      145
                                      927
                                     1,177
                                      705
                                      ...

                                     1999
                                     4,174
                                    134,480
                                    55,472
                                    18,532
                                      81
                                      56
                                      595
                                      105
                                     5,312
                                      314
                                     1,073
                                     1,361
                                     1,008
                                     2000
                                     4,368
                                    135,670
                                    58,930
                                    19,217
                                      81
                                      60
                                      609
                                      106
                                     5,123
                                      296
                                     1,055
                                     1,368
                                     1,043
                                     2001
                                     4,925
                                    139,709
                                    62,685
                                    19,947
                                      81
                                      61
                                      611
                                      116
                                     5,416
                                      305
                                     1,137
                                     1,384
                                     1,087
                                     2002
                                     5,026
                                    137,996
                                    63,789
                                    19,801
                                      79
                                      65
                                      620
                                      120
                                     5,396
                                      297
                                     1,155
                                     1,335
                                     1,080
                                     2003
                                     5,392
                                    137,745
                                    65,651
                                    19,873
                                      81
                                      65
                                      634
                                      126
                                     5,452
                                      292
                                     1,189
                                     1,307
                                     1,088
                                     2004
                                     5,813
                                    138,642
                                    69,860
                                    20,616
                                      83
                                      65
                                      650
                                      132
                                     5,528
                                      288
                                     1,228
                                     1,293
                                     1,108
                                     2005
                                     6,259
                                    138,779
                                    72,980
                                    20,987
                                      85
                                      65
                                      660
                                      141
                                     5,703
                                      289
                                     1,290
                                     1,309
                                     1,155
                                     2006
                                     6,770
                                    137,742
                                    76,321
                                    21,380
                                      88
                                      66
                                      672
                                      152
                                     5,948
                                      293
                                     1,370
                                     1,353
                                     1,228
                                     2007
                                     7,254
                                    138,354
                                    78,443
                                    21,398
                                      91
                                      67
                                      680
                                      164
                                     6,208
                                      297
                                     1,456
                                     1,364
                                     1,274
                                     2008
                                     7,869
                                    139,501
                                    78,596
                                    20,868
                                      96
                                      65
                                      687
                                      172
                                     6,322
                                      293
                                     1,509
                                     1,319
                                     1,268
                                     2009
                                     8,046
                                    138,743
                                    79,219
                                    20,464
                                      94
                                      67
                                      684
                                      178
                                     6,356
                                      286
                                     1,544
                                     1,317
                                     1,303
                                     2010
                                     8,125
                                    133,313
                                    79,641
                                    20,007
                                      89
                                      68
                                      694
                                      180
                                     6,234
                                      271
                                     1,540
                                     1,266
                                     1,289
                                     2011
                                     8,553
                                    128,078
                                    87,030
                                    21,252
                                      18
                                      66
                                      587
                                      176
                                     5,915
                                      248
                                     1,487
                                     1,198
                                     1,255

Note that the decline in sales seen in the 2008 recession results in a flattening of total population growth rates, and eventually a decline for  Passenger Cars and Combination Long-haul trucks as shown in Table 5-1.  This suggests that the decline in sales was accompanied by a delay in the scrappage of older vehicles.  The dynamic vehicle survival rates in MOVES and their impact on age distributions are discussed in Section 7.1.2.
 Projected Vehicle Populations (2012-2050)
The previous section described the historic fleet as it appeared in the data. This section presents how EPA projected those vehicle populations into the future. This work is inherently dependent on projections of both vehicle sales and scrappage. While future vehicle sales are commonly included in economic forecasts, there are no reliable sources for projected national vehicle scrappage. Therefore, we decided to use projected VMT growth as a surrogate for vehicle population growth. In examining VMT per vehicle by HPMS class over the historic years presented above, this surrogate appears reasonable. Table 5-2 shows the VMT values of Table 4-1 divided by the vehicle populations of Table 5-1 grouped by HPMS classification. At this level of aggregation, VMT per vehicle is relatively constant with no clear trends over time.

               Table 5-2 VMT per Vehicle by HPMS Classification
                                     Year
                                  Motorcycles
                              Light-Duty Vehicles
                                     Buses
                              Single Unit Trucks
                              Combination Trucks
                                     1999
                                     3,263
                                    11,518
                                    20,291
                                    14,776
                                    67,928
                                     2000
                                     2,787
                                    11,497
                                    19,740
                                    15,271
                                    66,876
                                     2001
                                     2,258
                                    11,240
                                    17,240
                                    14,837
                                    68,381
                                     2002
                                     2,223
                                    11,533
                                    17,455
                                    15,401
                                    69,655
                                     2003
                                     2,111
                                    11,552
                                    17,155
                                    15,969
                                    72,459
                                     2004
                                     2,576
                                    11,575
                                    16,946
                                    15,501
                                    72,037
                                     2005
                                     2,201
                                    11,505
                                    16,238
                                    14,783
                                    71,075
                                     2006
                                     2,830
                                    11,385
                                    16,995
                                    15,885
                                    68,702
                                     2007
                                     2,950
                                    11,298
                                    17,322
                                    14,767
                                    69,825
                                     2008
                                     2,645
                                    11,007
                                    17,480
                                    15,291
                                    71,058
                                     2009
                                     2,588
                                    11,044
                                    17,026
                                    14,372
                                    64,160
                                     2010
                                     2,279
                                    11,369
                                    16,181
                                    13,464
                                    68,802
                                     2011
                                     2,163
                                    11,197
                                    20,541
                                    13,227
                                    66,731

Therefore, the AEO growth factors used to project future VMT as described in Section 4.2 were used to project populations. (Motorcycle growth was calculated using factors from light-duty vehicles.) Since these growth factors are by HPMS class, the 2011 source type populations were aggregated by HPMS class before the growth factors were applied to the base populations. The resulting HPMS class population projections are presented in Table 5-3. However, MOVES cannot use populations in this format as it requires them to be disaggregated by source type. The distribution projected HPMS class populations to source type was calculated with the same algorithm used to produce age distributions. Please see Section <IP_ADDRESS> for a detailed discussion on this topic. The resulting projected source type populations are tabulated in Section 17 (Appendix A).

  Table 5-3 Projected HPMS Category Populations for 2012-2050 (in thousands)
                                     Year
                                  Motorcycles
                              Light-Duty Vehicles
                                     Buses
                              Single Unit Trucks
                              Combination Trucks
                                     2012
                                     8,571
                                    236,285
                                      704
                                     8,198
                                     2,471
                                     2013
                                     8,687
                                    239,479
                                      734
                                     8,637
                                     2,566
                                     2014
                                     8,706
                                    240,028
                                      757
                                     8,973
                                     2,635
                                     2015
                                     8,747
                                    241,178
                                      789
                                     9,393
                                     2,745
                                     2016
                                     8,844
                                    243,868
                                      822
                                     9,790
                                     2,857
                                     2017
                                     8,943
                                    246,584
                                      844
                                    10,056
                                     2,935
                                     2018
                                     9,018
                                    248,692
                                      860
                                    10,218
                                     2,990
                                     2019
                                     9,098
                                    250,904
                                      875
                                    10,373
                                     3,045
                                     2020
                                     9,178
                                    253,126
                                      890
                                    10,543
                                     3,100
                                     2021
                                     9,260
                                    255,371
                                      906
                                    10,733
                                     3,159
                                     2022
                                     9,337
                                    257,508
                                      923
                                    10,934
                                     3,220
                                     2023
                                     9,416
                                    259,695
                                      941
                                    11,126
                                     3,281
                                     2024
                                     9,498
                                    261,966
                                      956
                                    11,290
                                     3,338
                                     2025
                                     9,585
                                    264,368
                                      974
                                    11,463
                                     3,400
                                     2026
                                     9,680
                                    266,983
                                      990
                                    11,620
                                     3,459
                                     2027
                                     9,781
                                    269,767
                                     1,004
                                    11,747
                                     3,510
                                     2028
                                     9,888
                                    272,745
                                     1,015
                                    11,858
                                     3,554
                                     2029
                                     9,996
                                    275,707
                                     1,027
                                    11,978
                                     3,600
                                     2030
                                    10,103
                                    278,670
                                     1,041
                                    12,107
                                     3,650
                                     2031
                                    10,215
                                    281,752
                                     1,053
                                    12,234
                                     3,698
                                     2032
                                    10,328
                                    284,871
                                     1,063
                                    12,335
                                     3,737
                                     2033
                                    10,439
                                    287,918
                                     1,075
                                    12,454
                                     3,783
                                     2034
                                    10,538
                                    290,669
                                     1,091
                                    12,606
                                     3,842
                                     2035
                                    10,633
                                    293,277
                                     1,106
                                    12,745
                                     3,901
                                     2036
                                    10,724
                                    295,790
                                     1,122
                                    12,877
                                     3,961
                                     2037
                                    10,813
                                    298,244
                                     1,137
                                    13,007
                                     4,021
                                     2038
                                    10,901
                                    300,667
                                     1,152
                                    13,129
                                     4,081
                                     2039
                                    10,983
                                    302,932
                                     1,166
                                    13,238
                                     4,136
                                     2040
                                    11,055
                                    304,914
                                     1,180
                                    13,346
                                     4,193
                                     2041
                                    11,155
                                    307,671
                                     1,196
                                    13,472
                                     4,251
                                     2042
                                    11,256
                                    310,453
                                     1,210
                                    13,599
                                     4,311
                                     2043
                                    11,357
                                    313,260
                                     1,226
                                    13,731
                                     4,371
                                     2044
                                    11,460
                                    316,092
                                     1,241
                                    13,864
                                     4,432
                                     2045
                                    11,564
                                    318,951
                                     1,257
                                    13,998
                                     4,494
                                     2046
                                    11,668
                                    321,835
                                     1,273
                                    14,135
                                     4,556
                                     2047
                                    11,774
                                    324,745
                                     1,289
                                    14,273
                                     4,620
                                     2048
                                    11,880
                                    327,681
                                     1,304
                                    14,411
                                     4,684
                                     2049
                                    11,988
                                    330,642
                                     1,322
                                    14,550
                                     4,750
                                     2050
                                    12,096
                                    333,632
                                     1,338
                                    14,691
                                     4,816

Fleet Characteristics
MOVES categorizes vehicles into thirteen source use types as described  in Section 2.1, which are defined using physical characteristics, such as number of axles and tires, and travel behavior characteristics, such as typical trip lengths. This section describes the defining characteristics of the source types in greater detail and explains how source type is related to fuel type and regulatory class, primarily through the SampleVehiclePopulation table.
Source Type Definitions
MOVES Source types are intended to further divide HPMS vehicle classifications into groups of vehicles with similar activity patterns For example, passenger trucks and light commercial trucks are expected to have different daily trip patterns. VIUS was our main source of information for distinguishing these vehicles. Table 4-6 summarizes how the VIUS2002 parameters were used to delineate the light-duty, single unit, and combination truck source types for MOVES2014.

Axle arrangement (AXLE_CONFIG) was used to define three categories: straight trucks with two axles and six tires (codes 2, 9, 10, 11), all straight trucks (codes 1-21), and all tractor-trailer combinations (codes 21+). Primary distance of operation (PRIMARY_TRIP) was used to define short-haul (codes 1-4) for vehicles with primary operation distances less than 200 miles and long-haul (codes 5-6) for 200 miles and greater. The VIN-decoded gross vehicle weight (ADM_GVW) and survey weight (VIUS_GVW) were used to distinguish vehicles less than 10,000 lbs. as light-duty and vehicles greater than or equal to 10,000 lbs. as heavy-duty. Any vehicle with two axles and at least six tires was considered a single unit truck regardless of weight. We also note that refuse trucks have their own VIUS vocational category (BODYTYPE 21) and that MOVES distinguishes between personal (OPCLASS 5) and non-personal use.

Table 6-1 VIUS2002 Parameters Used to Distinguish Truck Source Types in MOVES2014
                                  Source Type
                               Axle Arrangement
                         Primary Distance of Operation
                                    Weight
                                   Body Type
                            Operator Classification
Passenger Trucks
AXLE_CONFIG in (1,6,7,8)[†]
Any
ADM_GVW in (1,2) &
VIUS_GVW in (1,2,3)
Any
OPCLASS=5
Light Commercial Trucks
AXLE_CONFIG in (1,6,7,8)[†]
Any
ADM_GVW in (1,2) &
VIUS_GVW in (1,2,3)
Any
OPCLASS!=5
Refuse Trucks*
AXLE_CONFIG in (2,9,10,11)
TRIP_PRIMARY in (1,2,3,4)
Any
BODYTYPE
=21
Any

AXLE_CONFIG <=21
TRIP_PRIMARY in (1,2,3,4)
ADM_GVW > 2 &
VIUS_GVW > 3
BODYTYPE
=21
Any
Single Unit Short-Haul Trucks*
AXLE_CONFIG in (2,9,10,11)
TRIP_PRIMARY in (1,2,3,4)
Any
BODYTYPE
!=21
Any

AXLE_CONFIG <=21
TRIP_PRIMARY in (1,2,3,4)
ADM_GVW > 2 &
VIUS_GVW > 3
BODYTYPE
!=21
Any
Single Unit Long-Haul Trucks*
AXLE_CONFIG in (2,9,10,11)
TRIP_PRIMARY in (5,6)
Any
Any
Any

AXLE_CONFIG <=21
TRIP_PRIMARY in (5,6)
ADM_GVW > 2 &
VIUS_GVW > 3
Any
Any
Combination Short-Haul Trucks
AXLE_CONFIG >=21
TRIP_PRIMARY in (1,2,3,4)
Any
Any
Any
Combination Long-Haul Trucks
AXLE_CONFIG >=21
TRIP_PRIMARY in (5,6)
Any
Any
Any
†   In the MOVES2014 analysis, we did not constrain axle configuration of light-duty trucks, so there are some, albeit very few, trucks that have three axles or more and/or six tires or more. These vehicles are classified as light-duty trucks based primarily on their weight. Only 0.27% of light-duty trucks have such tire and/or axle parameters and they have a negligible impact on vehicle populations and emissions.
* For a source type with multiple rows, the source type is applied to any vehicle with either set of parameters.

Motorcycles and passenger cars in MOVES borrow vehicle definitions from the FHWA Highway Performance Monitoring System (HPMS) classifications from the Highway Statistics MV-1 Table. Source type definitions for intercity, transit, and school buses are taken from various US Department of Transportation sources. While refuse trucks were identified and separated from other single unit trucks in VIUS, motor homes were not.

Motorcycles
According to the HPMS vehicle description, motorcycles (sourceTypeID 11) are, "all two- or three-wheeled motorized vehicles, typically with saddle seats and steered by handlebars rather than a wheel." This category usually includes any registered motorcycles, motor scooters, mopeds, and motor-powered bicycles. Neither the 2011 Polk dataset nor VIUS contain any information on motorcycles. As noted in Section 5, information on motorcycle populations comes from HPMS MV-1 registrations.

Passenger Cars
Passenger cars are defined as any coupes, compacts, sedans, or station wagons with the primary purpose of carrying passengers.[24] All passenger cars (sourceTypeID 21) are categorized in the light-duty vehicle regulatory class (regClassID 20). Cars were not surveyed in VIUS, but Polk has a robust yet proprietary dataset of car registrations from all fifty states.

Light-Duty Trucks
Light-duty trucks include pickups, sport utility vehicles (SUVs), and vans.  Depending on use and GVWR, we categorize them into two different MOVES source types: 1) passenger trucks (sourceTypeID 31), and 2) light commercial trucks (sourceTypeID 32). According to 2011 VM-1 vehicle classifications from FHWA, light-duty vehicles are those weighing less than 10,000 pounds (i.e. they are in weight class 1 and 2), except Class 2b trucks with two axles and six tires are assigned to the single unit truck category.

VIUS contains many survey questions on weight; we chose to use both a VIN-decoded gross vehicle weight rating (ADM_GVW) and a respondent self-reported GVWR (VIUS_GVW) to differentiate between light-duty and single unit trucks. For the passenger trucks, there is a final VIUS constraint that the most frequent operator classification (OPCLASS) must be personal transportation. Inversely, light commercial trucks (sourceTypeID 32) have a VIUS constraint that their most frequent operator classification must not be personal transportation.

Buses
MOVES has three bus source types: intercity (sourceTypeID 41), transit (sourceTypeID 42), and school buses (sourceTypeID 43). Buses were not included in either VIUS or the Polk dataset, so supplementary data sources were necessary. MOVES uses various US Department of Transportation definitions for buses.

Transit buses are defined in the Federal Transit Administration's National Transit Database (NTD), which states that they are buses owned by a public transit organization for the primary purpose of transporting passengers on fixed routes and schedules. According to FHWA, school buses are defined as vehicles designed to carry more than 10 passengers, used to transport K-12 students between their home and school. Intercity buses are, as defined by the Bureau of Transportation Statistics, "interstate motor carrier of passengers with an average annual gross revenue of at least one million dollars," but MOVES also considers any bus that cannot be categorized as either a transit or school bus to be an intercity bus.

Single Unit Trucks
The single unit HPMS class in MOVES consists of refuse trucks (sourceTypeID 51), short-haul single unit trucks (sourceTypeID 52), long-haul single unit trucks (sourceTypeID 53), and motor homes (sourceTypeID 54). With 2013 VM-1 updates to vehicle classifications, FHWA now defines a single unit truck as a single-frame truck with a gross vehicle weight rating of greater than 10,000 pounds or with two axles and at least six tires -- colloquially known as a `dualie.' As with light-duty truck source types, single unit trucks are sorted using VIUS parameters, in this case that includes axle configuration (AXLE_CONFIG) for straight trucks (codes 1-21), vehicle weight (both ADM_GVW and VIUS_GVW), most common trip distance (TRIP_PRIMARY), and body type (BODYTYPE). All short-haul single unit trucks must have a primary trip distance of 200 miles or less and must not be refuse trucks and all long-haul trucks must have a primary trip distance of greater than 200 miles. Refuse trucks are short-haul single unit trucks with a body type (code 21) for trash, garbage, or recyclable material hauling. Motor homes are not included in VIUS.

Combination Trucks
A combination truck is any truck-tractor towing at least one trailer according to VIUS. MOVES divides these tractor-trailers into two MOVES source types: short-haul (sourceTypeID 61) and long-haul combination trucks (sourceTypeID 62). Like single unit trucks, short-haul and long-haul combination trucks are distinguished by their primary trip length (TRIP_PRIMARY) in VIUS. If the tractor-trailer's primary trip length is equal to or less than 200 miles, then it is considered short-haul. If the tractor-trailer's primary trip length is greater than 200 miles, then it is considered long-haul. Short-haul combination trucks are older than long-haul combination trucks and these short-haul trucks often purchased in secondary markets, such as for drayage applications, after being used primarily for long-haul trips.

Sample Vehicle Population
To match source types to emission rates, MOVES must associate each source type with specific fueltypes and regulatory classes.  Much of default the information on fleet characteristics is stored in the SampleVehiclePopulation table, which contains two fractions: 1) stmyFraction, and 2) stmyFuelEngFraction. The former fraction defines the default fuel type distribution, which can be modified by the user through the Alternative Fuel Vehicle and Technology (AVFT) table, and the latter fraction forms the default regulatory class distribution. Both SVP fractions are computed through the EPA sample vehicle counts dataset that joins 2011 national R.L. Polk vehicle registration data with Vehicle Inventory and Use Survey (VIUS) classifications.

Fuel Type and Regulatory Class Distributions

The stmyFraction is the default national fuel type and regulatory class allocation for each source type and model year. Written out mathematically, we define the stmyFraction as,

                   f(stmy)i,j,k,l=Ni,j,k,ljϵJ,kϵKNi,j,k,l,
                                                                     Equation 1

where the number of vehicles N in a given model year i, regulatory class j, fuel type k, and source type l is divided by the sum of vehicles across the set of all regulatory classes J and all fuel types K. That is, the denominator only differs by source type and model year. For example, model year 2010 passenger trucks have stmyFractions that indicate the distribution of these vehicles between gasoline, diesel, E85, and electricity and regulatory classes 30 and 40.  These values must sums to one for each source type and model year. A value of zero indicates that the MOVES default population of vehicles of that source type, model year, fuel type and regulatory class is negligible or does not exist.

While stmyFraction indicates MOVES default values, the stmyFuelEngFraction allows the modeling of non-default fuel type distributions.  For each allowable combination of source type, model year and fuel type, the stmyFuelEngFraction indicates the expected regulatory class distribution, whether or not these vehicles exist in the default. Similar to the stmyFraction above, we define stmyFuelEngFraction as,

                  f(stmyfueleng)i,j,k,l=Ni,j,k,ljϵJNi,j,k,l,
                                                                     Equation 2

for number of vehicles N, model year i, regulatory class j, fuel type k, source type l, and the set of all regulatory classes J. The denominator differs by source type, model year, and fuel type in this case. For example, for model year 2010 gasoline passenger trucks, the table will list a stmyFuelEngFraction for regulatory class 30 and another for regulatory class 40. These fractions sum to one for each combination of source type, model year and fuel type.

For example, while the stmyFraction indicates that the MOVES defaults assign zero fraction of model year 2010 passenger trucks to the electricity fuel type, the  stmyFuelEngFraction indicates a default (hypothetical) regulatory class distribution if these vehicles existed. In this case, MOVES would model them all as belonging to regulatory class 30.  The stmyFraction is particularly important because users can edit fuel type distributions using the Alternative Vehicle Fuel and Technology (AVFT) importer. For instance, a user can create a future scenario in which there is a high penetration of electric passenger trucks. The stmyFuelEngFraction allows MOVES to assign vehicles to regulatory class without requiring this input from the user. This means an allowed stmyFuelEngFraction must never be zero.

As an example, Figure 6-1 shows the national default fuel type fractions for all light-duty vehicles among the different MOVES fuel types. As noted in Section 2.4 these fuel type fractions indicate the fuel capability of the vehicle and not the fuel being used by the vehicle. In this report's nomenclature, E85-capable and flexible fuel vehicles are synomous -- meaning they can accept either gasoline or E85 fuel. Although these vehicle are capable of running on E85, the fuel type distributions do not have any information on how often they actually use E85. Discussion on fuel usage can be found in the MOVES2014 Fuel Supply Report.[7]

Figure 6-1 Default fuel type fractions for light-duty source types in MOVES2014, where being E85-capable indicates flexible fuel vehicle populations and all default electric vehicle populations are zero

Sample Vehicle Counts

The SampleVehiclePopulation table fractions have been developed by EPA using the sample vehicle counts dataset referenced in Section 3, which primarily joins calendar year 2011 registration data from R.L. Polk and the Vehicle Inventory and Use Survey (VIUS) results. The sample vehicle counts dataset was generated by multiplying the 2011 Polk vehicle populations by the source type allocations from VIUS.

While VIUS provide source type classifications, we relied primarily on the 2011 Polk vehicle registration dataset to form the basis of the fuel type and regulatory class distributions in the SampleVehiclePopulation table. We purchased the Polk dataset in April 2012, so it did not have complete registration records for model year 2012 vehicles and therefore model year 2012 vehicles were omitted from the SVP analysis. The Polk data was provided with the following fields: vehicle type (cars or trucks), fuel type, gross vehicle weight rating (GVWR) for trucks, household vehicle counts, and work vehicle counts. We combined the household and work vehicle counts.  The MOVES distinction between personal and commercial travel for light-duty trucks comes from VIUS.

The Polk records by FHWA truck weight class were grouped into MOVES GVWR-based regulatory classes, as shown in Table 6-1 below. As stated above, all passenger cars were assigned to regClassID 20. The mapping of weight class to regulatory class is straightforward with one notable exception for delineating trucks weighing more or less than 8,500 lbs.

Table 6-2 Initial mapping from FHWA truck classes to MOVES regulatory classes.
                               Vehicle Category
                            FHWA Truck Weight Class
                              Weight Range (lbs)
                                  regClassID
                                    Trucks
                                       1
                                  < 6,000
                                      30
                                    Trucks
                                      2a
                                6,001  -  8,500
                                      30*
                                    Trucks
                                      2b
                               8,501  -  10,000
                                      41*
                                    Trucks
                                       3
                               10,001  -  14,000
                                      41
                                    Trucks
                                       4
                               14,001  -  16,000
                                      42
                                    Trucks
                                       5
                               16,001  -  19,500
                                      42*
                                    Trucks
                                       6
                               19,501  -  26,000
                                      46
                                    Trucks
                                       7
                               26,001  -  33,000
                                      46
                                    Trucks
                                      8a
                               33,001  -  60,000
                                      47
                                    Trucks
                                      8b
                                  > 60,001
                                      47
                                     Cars

                                      20
      *After the Polk data has been sorted into source types (described later in this section), some regulatory classes were merged or divided. Any regulatory class 41 vehicles in light-duty truck source types have been reclassified into the new regulatory class 40 (see explanation in Section 2.3), any regulatory class 30 vehicles in single unit truck source types have been reclassified into regulatory class 41, and any regulatory class 42 vehicles in combination truck source types have been reclassified into regulatory class 46.

Since the Polk dataset did not distinguish between Class 2a (6,001-8,500 lbs) and Class 2b (8,501-10,000 lbs) trucks, but MOVES regulatory classes 30, 40, and 41 all fall somewhere in Class 2, we needed to use a secondary data source to allocate the Polk gasoline and diesel trucks between Class 2a and 2b. According an Oak Ridge National Laboratory (ORNL) paper, just over 25 percent of diesel Class 2 trucks are Class 2a and about 81 percent of gasoline Class 2 trucks are in Class 2b. These fractions are summarized in Table 6-2. We used these fractions to allocate the Polk Class 2 gasoline and diesel trucks into the appropriate regulatory classes (Class 2a are in regulatory class 30, and Class 2b are in regulatory class 40/41).

  Table 6-3 Fractions of Class 2a and 2b trucks fueled by gasoline and diesel
                                   Fuel Type
                                  Truck Class

                                      2a
                                      2b
Gasoline
0.975
0.760
Diesel
0.025
0.240

1.000
1.000

Additionally, the Polk dataset includes a variety of fuels, some that are included in MOVES and others that are not. Only the Polk gasoline and diesel vehicles were included in our analysis; all other alternative fuel vehicles were omitted. While MOVES2014 does model light-duty E-85 and electric vehicles, and compressed natural gas (CNG) transit buses, these relative penetrations of alternative fuel vehicles have been developed from secondary data sources rather than Polk. Polk excludes some government fleets and retrofit vehicles that could potentially be large contributors to these alternative fuel vehicle populations. Instead we used flexible fuel vehicle sales data reported for EPA certification, and dedicated CNG bus populations from the National Transit Database. The Table 6-4 illustrates how Polk fuels were mapped to MOVES fuel types, and which Polk fuels were not used in MOVES.

This mapping in Table 6-4 led us to discard 0.22 percent, roughly 530,000 vehicles (mostly dedicated or aftermarket alternative fuel vehicles), of Polk's 2011 national fleet in developing the default fuel type fractions. However, because the MOVES national population is derived top-down from FHWA registration data, as outlined in Section 5.1, the total population is not affected. We considered the Polk vehicle estimates to be a sufficient sample for the fuel type and regulatory class distributions in the SampleVehiclePopulation table.

Table 6-4 A list of fuels from the Polk dataset used to develop MOVES fuel type distributions.
                                Polk Fuel Type
                               MOVES fuelTypeID
                                MOVES fuelType
                                    Unknown
                                      N/A

                                   Undefined
                                      N/A

                             Both Gas and Electric
                                       1
                                   Gasoline
                                      Gas
                                       1
                                   Gasoline
                                   Gas/Elec
                                       1
                                   Gasoline
                                   Gasoline
                                       1
                                   Gasoline
                                    Diesel
                                       2
                                    Diesel
                                  Natural Gas
                                      N/A

                            Compressed Natural Gas
                                      N/A

                                   Natr.Gas