Document ID: EPA-HQ-OAR-2014-0827-0367
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2015-07-13T04:00Z

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 7.1.2.2 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
                                      N/A
                                       
                                    Propane
                                      N/A
                                       
                          Flexible (Gasoline/Ethanol)
                                      N/A
                                       
                                   Flexible
                                      N/A
                                       
                                   Electric
                                      N/A
                                       
                                   Cnvrtble
                                      N/A
                                       
                                  Conversion
                                      N/A
                                       
                                   Methanol
                                      N/A
                                       
                                    Ethanol
                                      N/A
                                       
                                  Convertible
                                      N/A
                                       
      
      
Next we transformed the VIUS dataset into MOVES format. The VIUS vehicle data was first assigned to MOVES source types using the constraints in Table 6-1 and then to MOVES regulatory classes using the mapping described in Table 6-2, including the allocation between Class 2a and 2b trucks from the ORNL study in Table 6-3. Similar to our fuel type mapping of the Polk dataset, we chose to omit alternative fuel vehicles, as summarized below in Table 6-4.

       Table 6-5 Mapping of VIUS2002 fuel types to MOVES2014 fuel types
                                VIUS Fuel Type
                                VIUS Fuel Code
                               MOVES fuelTypeID
                                MOVES fuelType
                                   Gasoline
                                       1
                                       1
                                   Gasoline
                                    Diesel
                                       2
                                       2
                                    Diesel
                                  Natural gas
                                       3
                                      N/A
                                       
                                    Propane
                                       4
                                      N/A
                                       
                                 Alcohol fuels
                                       5
                                      N/A
                                       
                                  Electricity
                                       6
                                      N/A
                                       
                           Gasoline and natural gas
                                       7
                                       1
                                   Gasoline
                             Gasoline and propane
                                       8
                                       1
                                   Gasoline
                          Gasoline and alcohol fuels
                                       9
                                       1
                                   Gasoline
                           Gasoline and electricity
                                      10
                                       1
                                   Gasoline
                            Diesel and natural gas
                                      11
                                       2
                                    Diesel
                              Diesel and propane
                                      12
                                       2
                                    Diesel
                            Diesel and alchol fuels
                                      13
                                       2
                                    Diesel
                            Diesel and electricity
                                      14
                                       2
                                    Diesel
                                 Not reported
                                      15
                                      N/A
                                       
                                Not applicable
                                      16
                                      N/A
                                       

This process yielded VIUS data by MOVES source type, model year, regulatory class, and fuel type. The VIUS source type distributions were calculated in a similar fashion to the SampleVehiclePopulation fractions discussed above for each regulatory class-fuel type-model year combination. Stated formally, for any given model year i, regulatory class j,  and fuel type k, the source type population fraction f for a specified source type l will be the number of VIUS trucks N in that source type divided by the sum of VIUS trucks across the set of all source types L. The source type population fraction is summarized in the following formula:

                      f(VIUS)i,j,k,l=Ni,j,k,llϵLNi,j,k,l
                                                                     Equation 3
The VIUS data in our analysis spanned model year 1986 to 2002. The 2002 source type distribution has been used for all distributions after MY 2002 and the 1986 distribution for all prior to MY 1986. 

From there the source type distributions from VIUS were multiplied by the Polk vehicle populations to generate the sample vehicle counts by source type, as shown schematically in Figure 6-26-16-1. Expressed in equation form, the sample vehicle counts are,
      

                 NSVPi,j,k,l=P(Polk)i,j,k,l∙f(VIUS)i,j,k,l,
                                                                     Equation 4

where N is the number of vehicles used to generated the SampleVehiclePopulation table, P is the 2011 Polk vehicle populations, and f is the source type distributions from VIUS. 
      
Figure 6-2 A schematic overview of how the 2011 Polk dataset and VIUS 2002 were joined to create EPA's sample vehicle counts for MOVES2014. Note that data on buses, motorcycles, and motor homes was pulled from other sources.
                                       
      
These sample vehicle counts by source type were then utilized to calculate the SVP fractions, stmyFraction and stmyFuelEngFraction, as defined above. Due to a small sample size of vehicles 30 years old and older in both the Polk and VIUS datasets, MOVES2010b SVP fractions were used for MY 1981 and earlier, which roughly follows the same procedure outlined above but instead uses a 1999 Polk vehicle registration dataset joined with VIUS. These MOVES2010b SVP fractions for MY 1960-1981 are described in Section 18 (Appendix B). MOVES2014 assumes no changes to fuel type distributions after model year 2011 except for flexible-fuel (E85-capable) vehicles, which are assumed to displace gasoline vehicles based on sales estimates as described below. MOVES2014 estimates any other population growth by source type, as described earlier in Section 5.2 rather than growth for specific fuel types within a source type. 
      
All Class 2b and 3 trucks were initially assigned to regulatory class 41 until vehicles were sorted into source types. Once the sample vehicle counts were available by source type, any light-duty trucks (sourceTypeID 31 or 32) in the original LHD regulatory class less than 14,000 lbs (regClassID 41) were reclassified in the new LHD regulatory class less than 10,000 lbs (regClassID 40), whereas any heavy-duty vehicles (sourceTypeID 41 and above) remained in regClassID 41. Similarly, any single unit trucks (sourceTypeID 52 and 53) in the LDT regulatory class (regClassID 30) were reclassified in regClassID 41 as heavy-duty vehicles. We also moved any regClassID 42 vehicles in combination truck source types to regClassID 46 because tractor-trailers must be either Class 7 or 8 trucks. This ensures a clean break between light- and heavy-duty emission results and that the emission calculations use the appropriate fixedMassFactor when calculating vehicle-specific power (VSP) for light-duty vehicles and scaled tractive power (STP) for heavy-duty vehicles.

As noted above, the initial sample vehicle counts dataset did not contain motorcycles, buses, or motor homes, so information on these source types was appended.  Motor homes -- even though they are considered single unit vocational vehicles -- cannot be identified in VIUS. In the subsections below, we have provided more detailed descriptions by source type.
   
Motorcycles
The representation of motorcycles in the SampleVehiclePopulation table is straightforward. All motorcycles fall into the motorcycle regulatory class (regClassID 10) and must be fueled by gasoline. We acknowledge that some alternative fuel motorcycles have been prototyped and may even be in small production, but they account for a negligible fraction of total US motorcycle sales and cannot be modeled in MOVES2014.

Passenger Cars
Any passenger car is considered to be in the light-duty vehicle regulatory class (regClassID 20). Cars were included in the Polk dataset purchased in 2012, and EPA's subsequent sample vehicle counts dataset, which provided the split between gasoline and diesel cars in the SampleVehiclePopulation table. Flexible fuel (E85-capable) cars were also included in the SVP fuel type distributions but added after the sample vehicle counts analysis. We assume that a flexible fuel vehicle would directly displace its gasoline counterpart. For model years 2011 and earlier, we used  manufacturer reported sales to EPA in order to calculate the fraction of sales of flexible fuel cars among sales of all gasoline and flexible fuel cars and added those penetrations as the fraction of E85 (fuelTypeID 5) vehicles and deducted them from the gasoline cars in the Polk dataset.
 
Similarly, for model years 2012 and later, we used Annual Energy Outlook (AEO) car sales projections from AEO2014's table labeled "Light-Duty Vehicle Sales by Technology Type" to derive flexible fuel vehicle penetrations and applied them to the Sample Vehicle Population, exclusively for regulatory class 20. All other alternative fueled cars were determined to have insignificant market shares now and into the future.

While MOVES can model electric vehicles (fuelTypeID 9), the current market share of electric cars is sufficiently small that we have set the default electric car population to zero. Users can model an electric vehicle population by using the AVFT tool to redistribute market share.  Electric vehicles do not have any tailpipe emissions, but MOVES2014 has electric vehicle rates for energy consumption, brakewear, and tirewear (electric vehicle brake and tirewear rates are copied from gasoline vehicles). Please consult the MOVES2014 documentation on greenhouse gases and brake and tirewear, respectively, for more information on the development of the energy and emission rates themselves.

Light-Duty Trucks
Since passenger and light commercial trucks are defined as light-duty vehicles, they are constrained to regulatory class 30 and 40. Within the sample vehicle counts, GVWR Class 1 and 2a trucks were classified as regulatory class 30 and Class 2b trucks with two axles and four tires were classified as regulatory class 40. Both light-duty truck source types are divided between gasoline and diesel using the underlying splits in the sample vehicle counts data. Passenger trucks and light commercial trucks have similar but distinct distributions. Similar to cars, a penetration of flexible fuel (E-85-capable) light-duty trucks was calculated using EPA certification sales for historic years (MY 2011 and earlier) and AEO light truck projections for future years (MY 2012 and later) from AEO2014's Table 64. The flexible fuel vehicle penetration was applied to regClassID 30 for both E-85 (fuelTypeID 5) passenger and light commercial trucks and then deducted from their gasoline counterparts in the same regulatory class. 

Buses
In line with the US Energy Information Administration (EIA) assumptions, all intercity buses in MOVES are powered by diesel fuel. The following non-school bus regulatory class distribution for intercity buses was applied to all model years based on 2011 FHWA data, as shown in Table 6-5. 

Table 6-6 Regulatory class fractions of school and non-school buses using 2011 FHWA data
                                 Vehicle Type
                               MOVES regClassID
                                       
                                      41
                                      42
                                      46
                                      47
                                     Total
                               Non-School Buses
                                    0.1856
                                    0.0200
                                    0.1214
                                    0.6730
                                       1
                                 School Buses
                                    0.0106
                                    0.0070
                                    0.9371
                                    0.0453
                                       1

The National Transit Database (NTD) Revenue Vehicle Inventory (Form 408) closely tracks the number of motor buses (MB) by fuel type each year and those statistics are used to develop the MOVES fuel type distributions for transit buses. The mapping from NTD fuel types to MOVES fuel types is summarized in Table 6-6. 

  Table 6-7 Mapping National Transit Database Fuel Types to MOVES Fuel Types
                                   NTD code
                                NTD description
                                  fuelTypeID
                            MOVES Fuel Description
                                      BD
Bio-diesel
                                       2
                                    diesel
                                      BF
Bunker fuel
                                      N/A
                                       
                                      CN
Compressed natural gas
                                       3
                                      CNG
                                      DF
Diesel fuel
                                       2
                                    diesel
                                      DU
Dual fuel
                                       2
                                    diesel
                                      EB
Electric battery
                                      N/A
                                       
                                      EP
Electric propulsion
                                      N/A
                                       
                                      ET
Ethanol
                                      N/A
                                       
                                      GA
Gasoline
                                       1
                                   gasoline
                                      GR
Grain additive
                                      N/A
                                       
                                      HD
Hybrid diesel
                                       2
                                    diesel
                                      HG
Hybrid gasoline
                                       1
                                   gasoline
                                      KE
Kerosene
                                      N/A
                                       
                                      LN
Liquefied natural gas
                                       3
                                      CNG
                                      LP
Liquefied petroleum gas
                                      N/A
                                       
                                      MT
Methanol
                                      N/A
                                       
                                      OR
Other
                                      N/A
                                       

While some other MOVES fuel types are included in the NTD, the transit bus fuel type distributions were allocated between diesel, CNG, and gasoline only. Together these three fuel types account for more than 99 percent of all transit buses in 2011, so no other alternative fuels are allowed within the transit bus source type due to negligible market shares. 

Biodiesel does not appear in the SampleVehiclePopulation table -- in MOVES it is considered a fuel subtype rather than a fuel type -- so biodiesel buses were added to the diesel buses from the NTD. Liquefied natural gas (LNG) comprises less than ten percent of all natural gas transit buses and only about 1.5 percent of the whole transit bus fleet in 2011. Without any readily available emission rate data on LNG buses, we grouped all natural gas fueled transit buses together. This means we effectively model LNG buses as if they were powered by CNG. Due to limited data, we assume that gasoline has a one-percent market share prior to model year 2000 and that diesel has a 99 percent market share prior to MY 1990. All other market shares of transit bus fuel types are derived using the NTD, as shown in Table 6-7.  MOVES modelers can adjust these distributions between the fuel types using the AVFT tool.

Table 6-8 Fuel type market shares by model year for transit buses in MOVES2014
                                  Model Year
                                MOVES Fuel Type
                                       
                                   Gasoline
                                    Diesel
                                      CNG
                                   1982-1989
                                     1.00%
                                    99.00%
                                     0.00%
                                     1990
                                     1.00%
                                    98.30%
                                     0.70%
                                     1991
                                     1.00%
                                    97.20%
                                     1.80%
                                     1992
                                     1.00%
                                    94.40%
                                     4.60%
                                     1993
                                     1.00%
                                    91.40%
                                     7.60%
                                     1994
                                     1.00%
                                    90.50%
                                     8.50%
                                     1995
                                     1.00%
                                    83.70%
                                    15.30%
                                     1996
                                     1.00%
                                    89.20%
                                     9.80%
                                     1997
                                     1.00%
                                    81.60%
                                    17.40%
                                     1998
                                     1.00%
                                    84.10%
                                    14.90%
                                     1999
                                     1.00%
                                    87.70%
                                    11.30%
                                     2000
                                     0.85%
                                    91.57%
                                     7.58%
                                     2001
                                     0.88%
                                    90.51%
                                     8.60%
                                     2002
                                     0.91%
                                    89.09%
                                    10.00%
                                     2003
                                     0.94%
                                    88.06%
                                    10.99%
                                     2004
                                     0.89%
                                    86.85%
                                    12.27%
                                     2005
                                     1.05%
                                    85.61%
                                    13.34%
                                     2006
                                     1.18%
                                    84.73%
                                    14.09%
                                     2007
                                     1.29%
                                    83.99%
                                    14.72%
                                     2008
                                     1.61%
                                    82.91%
                                    15.49%
                                     2009
                                     1.89%
                                    82.55%
                                    15.56%
                                     2010
                                     2.14%
                                    81.96%
                                    15.90%
                                     2011+
                                     2.46%
                                    81.75%
                                    15.79%

Urban transit buses are regulated separately from other heavy-duty vehicles, under 40 CFR 86.091-2. For this reason, CNG and diesel transit buses are each categorized in regulatory class 48. Lacking better data, we used a single regulatory class distribution from a study of diesel and CNG transit buses, highlighted in the MOVES2014 HD Emissions Rates Report[4], for gasoline transit buses as shown in Table 6-8 below. 

  Table 6-9 Regulatory class fractions of gasoline transit buses in MOVES2014
                       MOVES Source Type & Fuel Type
                               MOVES regClassID

                                      42
                                      46
                                      47
                                     Total
                            Gasoline Transit Buses
                                    0.2683
                                    0.0976
                                    0.6341
                                       1

The MOVES2014 school bus fuel type distribution is based on MOBILE6 estimates, originally calculated from 1996 and 1997 Polk bus registration data, for model years 1982-1996 are summarized in Table 6-9. The Union of Concerned Scientists estimates that roughly one percent of school buses run on non-diesel fuels, so we have assumed that one percent of school buses are gasoline fueled in MY 1997 and later. The school bus regulatory class distribution was also derived from the 2011 FHWA data in Table 6-5.

Table 6-10 Fuel type market shares by model year for school buses in MOVES2014
                                  Model Year
                                MOVES Fuel Type

                                                                      Gasoline 
                                                                         Diesel
                                     1982
                                    67.40%
                                    32.60%
                                     1983
                                    67.62%
                                    32.38%
                                     1984
                                    61.55%
                                    38.45%
                                     1985
                                    48.45%
                                    51.55%
                                     1986
                                    32.67%
                                    67.33%
                                     1987
                                    26.55%
                                    73.45%
                                     1988
                                    24.98%
                                    75.02%
                                     1989
                                    22.90%
                                    77.10%
                                     1990
                                    12.40%
                                    87.60%
                                     1991
                                     8.95%
                                    91.05%
                                     1992
                                     1.00%
                                    99.00%
                                     1993
                                    12.05%
                                    87.95%
                                     1994
                                    14.75%
                                    85.25%
                                     1995
                                    11.43%
                                    88.57%
                                     1996
                                     4.15%
                                    95.85%
                                     1997+
                                     1.00%
                                    99.00%

Single Unit Trucks
The fuel type and regulatory class distributions for the single unit trucks are calculated directly from the EPA's sample vehicle counts datasets, except motor homes. The single unit source types are split between gasoline and diesel only. Single unit vehicle are distributed among the heavy-duty regulatory classes (regClassIDs 41, 42, 46, and 47) based on the underlying sample vehicle data. Motor home was not included as a VIUS body type response, so their fuel type and regulatory class distributions have been developed through supplementary data sources. The fuel type distribution for motor homes is unchanged from MOVES2010b, originally based on interpolating information from the Recreation Vehicle Industry Association (RVIA) on fuel type market shares.  

        Table 6-11 Fuel type market shares for motor homes in MOVES2014
                                  Model Year
                               Percent of Diesel
                              Percent of Gasoline
                                   1982-1993
                                      15%
                                      85%
                                     1994
                                      18%
                                      82%
                                     1995
                                      21%
                                      79%
                                     1996
                                      23%
                                      77%
                                     1997
                                      26%
                                      74%
                                     1998
                                      29%
                                      71%
                                     1999
                                      32%
                                      68%
                                     2000
                                      34%
                                      66%
                                     2001
                                      37%
                                      63%
                                     2002
                                      40%
                                      60%
                                     2003
                                      41%
                                      59%
                                     2004
                                      43%
                                      57%
                                     2005
                                      44%
                                      56%
                                     2006
                                      46%
                                      54%
                                     2007
                                      47%
                                      53%
                                     2008
                                      49%
                                      51%
                                     2009
                                      50%
                                      50%
                                     2010+
                                      50%
                                      50%

The motor home regulatory class distribution, shown below in Table 6-12, is used across all model years based on the same 2011 FHWA dataset referenced above for school and non-school buses.

   Table 6-12 Regulatory class fractions of motor homes using 2011 FHWA data
                               MOVES Source Type
                               MOVES regClassID

                                      41
                                      42
                                      46
                                      47
                                     Total
                                  Motor Homes
                                    0.2697
                                    0.3940
                                    0.2976
                                    0.0387
                                       1

Combination Trucks
Combination trucks consist mostly of Class 8 trucks in the MOVES HHD regulatory class (regClassID 47) but also contain some Class 7 trucks in the MHD regulatory class (regClassID 46), predominantly in short-haul. Similarly, almost all combination trucks are diesel fueled. MOVES does not model gasoline long-haul combination trucks. Even for the short-haul source type, gasoline combination trucks are being phased out rapidly. After model year 2005, MOVES2014 assumes no gasoline combination trucks sales. These fuel type and regulatory class trends come out of the sample vehicle counts dataset. There has been growing interest in natural gas for freight transportation but currently this remains largely in the planning stages. There has not been sufficient testing of these trucks to develop MOVES emission rates. We will consider adding natural gas combination trucks as they become more prevalent and their emissions are more thoroughly tested.

Vehicle Characteristics that Vary by Age
Age is an important factor in calculating vehicle emission inventories, identifying high emitters, and characterizing travel behavior. MOVES employs a number of different age dependent factors, including deterioration of engine and emission after-treatment technology due to tampering and malmaintenance, vehicle scrappage and fleet turnover, and mileage accumulation over the lifetime of the vehicle. Deterioration effects are detailed in the MOVES2014 reports on the development of light-duty and heavy-duty emission rates.[3][,][4] In this section, there is discussion of vehicle age distributions, survival rates, and relative mileage accumulation rates by source type. 
Age Distributions
A vehicle's age is simply the difference between its model year and the year of analysis. Age distributions in MOVES vary by source type and range from zero to 30+ years, so that all vehicles 30 years and older are modeled together. As such, an age distribution is comprised of 31 fractions, where each fraction represents the number of vehicles present at a certain age divided by the vehicle population for all ages, as summarized later in this section in Equation 9. Since sales and scrappage rates are not constant, these distributions vary by calendar year. The age distribution for each source type is stored in the SourceTypeAgeDistribution table, and fractions from each source type's age distribution sum to one across a calendar year. MOVES age distributions were compiled from a variety of data sources, which are discussed below. Age distributions for the 2011 base year are summarized in Table 7-1; all other years are available in the MOVES2014 default database SourceTypeAgeDistribution table.

Age Distributions from Registration Data
Ideally all historic age distributions could be derived from registration data sources for each analysis year available in MOVES. However, acquiring such data is prohibitively costly, so MOVES2014 only contains registration-based age distributions for two analysis years: 1990 and 2011. The following sections detail how these data were analyzed and used in MOVES2014.
      
1990 Age Distributions
MOVES2014 age distributions for calendar year 1990 have not been updated since the last model release. Please refer to Section 19 (Appendix C) for more information on the 1990 distributions.
    
2011 Age Distributions
The 2011 age distributions for cars and trucks were derived from the sample vehicle counts dataset, as discussed earlier in Section 1.1.1. This sample vehicle data includes eight of the thirteen source types: passenger cars (21), passenger trucks (31), light commercial trucks (32), refuse trucks (51), short-haul single unit trucks (52), long-haul single unit trucks (53), short-haul combination trucks (61), and long-haul combination trucks (62). We were able to develop zero to 30+ year age distributions in 2011 for the eight source types mentioned. 
      
For the source types that were not included in the sample vehicle data -- specifically motorcycles, motorhomes, and buses -- we calculated the 2011 age distributions by running MOVES2010b with the latest sales data available. That is, MOVES2010b used 1999 populations, sales, and scrappage forecasts to project future populations by model year, which we then used to compute age distributions. This approach kept the MOVES2010b base populations and scrappage rates but substituted in MY 1999-2011 sales.  We pulled sales for motorcycles (11) from the Motorcycle Industry Council's Statistical Annual report[24], transit buses (42) from internal EPA estimates based on manufacturer reporting, and school buses (43) from the School Bus Fleet Fact Book[18]. Since 2011 age distributions were calculated independently, intercity bus (41) and motor home (54) sales data were based on slightly different assumptions. Both of these source types used an average of Ward's Class 3-8 truck sales in Oak Ridge's Transportation Energy Data Book[22], transformed into MOVES source types using the allocation of sample vehicle counts described in Section 6. For more information on these data sources, revisit Section 3. 
      
Table 7-1 shows the fraction of vehicles by age (0-30+ years) and source type for calendar year 2011. These 2011 age distributions became the basis for all the forecast age distributions in Section 7.1.2.2 and all backcast age distributions in Section 7.1.2.3.  

           Figure 7-1 2011 Age Distributions for MOVES Source Types
                                       
              Table 7-1 2011 Age Fractions for MOVES Source Types
                                      Age
                                      11
                                      21
                                      31
                                      32
                                      41
                                      42
                                      43
                                      51
                                      52
                                      53
                                      54
                                      61
                                      62
                                       0
                                    0.0585
                                     0.042
                                    0.0496
                                    0.0557
                                    0.0477
                                    0.0628
                                    0.0368
                                    0.0334
                                     0.035
                                    0.0237
                                     0.046
                                    0.0219
                                    0.0478
                                       1
                                    0.0565
                                    0.0472
                                     0.044
                                    0.0482
                                    0.0421
                                    0.0385
                                    0.0403
                                    0.0265
                                    0.0216
                                     0.015
                                    0.0406
                                    0.0164
                                    0.0378
                                       2
                                    0.0614
                                     0.043
                                    0.0335
                                    0.0372
                                    0.0353
                                    0.0393
                                     0.048
                                    0.0351
                                    0.0231
                                    0.0176
                                     0.034
                                    0.0213
                                    0.0501
                                       3
                                    0.1088
                                    0.0545
                                    0.0587
                                    0.0668
                                    0.0458
                                    0.0555
                                    0.0529
                                    0.0273
                                    0.0479
                                     0.031
                                    0.0442
                                    0.0192
                                    0.0392
                                       4
                                    0.0968
                                    0.0597
                                    0.0626
                                    0.0703
                                    0.0601
                                    0.0539
                                    0.0548
                                    0.0956
                                    0.0629
                                    0.0544
                                    0.0579
                                    0.0629
                                    0.1371
                                       5
                                    0.0917
                                    0.0562
                                    0.0644
                                    0.0743
                                    0.0617
                                    0.0389
                                    0.0644
                                    0.0718
                                    0.0666
                                    0.0486
                                    0.0594
                                    0.0468
                                    0.1028
                                       6
                                    0.0803
                                    0.0562
                                    0.0677
                                     0.077
                                    0.0638
                                    0.0607
                                    0.0574
                                    0.0677
                                    0.0577
                                     0.045
                                    0.0615
                                    0.0455
                                    0.0971
                                       7
                                    0.0682
                                    0.0526
                                    0.0686
                                    0.0781
                                     0.062
                                    0.0498
                                    0.0565
                                    0.0407
                                    0.0506
                                    0.0333
                                    0.0597
                                    0.0288
                                    0.0584
                                       8
                                    0.0583
                                    0.0551
                                    0.0638
                                    0.0724
                                    0.0574
                                    0.0488
                                    0.0487
                                     0.04
                                    0.0438
                                    0.0284
                                    0.0553
                                    0.0256
                                     0.057
                                       9
                                    0.0514
                                     0.055
                                    0.0624
                                    0.0702
                                    0.0538
                                    0.0495
                                    0.0511
                                     0.029
                                    0.0393
                                    0.0238
                                    0.0518
                                    0.0199
                                    0.0415
                                      10
                                    0.0436
                                    0.0534
                                    0.0562
                                    0.0647
                                    0.0517
                                     0.057
                                    0.0467
                                    0.0357
                                    0.0427
                                     0.059
                                    0.0498
                                    0.0391
                                    0.0482
                                      11
                                    0.0348
                                    0.0575
                                    0.0545
                                     0.055
                                    0.0492
                                    0.0385
                                    0.0508
                                    0.0488
                                    0.0697
                                    0.1457
                                    0.0474
                                    0.0535
                                    0.0766
                                      12
                                    0.0263
                                     0.05
                                    0.0504
                                    0.0433
                                    0.0478
                                    0.0374
                                     0.047
                                    0.0702
                                    0.0591
                                    0.1267
                                    0.0461
                                    0.0482
                                    0.0572
                                      13
                                    0.0224
                                    0.0441
                                    0.0424
                                    0.0273
                                    0.0362
                                    0.0439
                                    0.0371
                                    0.0645
                                    0.0334
                                    0.0213
                                    0.0271
                                     0.049
                                    0.0381
                                      14
                                    0.0215
                                     0.042
                                    0.0372
                                    0.0305
                                    0.0295
                                    0.0401
                                    0.0345
                                    0.0312
                                    0.0459
                                    0.0175
                                    0.0417
                                    0.0398
                                    0.0215
                                      15
                                    0.0188
                                    0.0354
                                    0.0284
                                    0.0203
                                    0.0244
                                    0.0369
                                    0.0298
                                    0.0406
                                    0.0308
                                    0.0198
                                    0.0258
                                    0.0556
                                    0.0234
                                      16
                                    0.0142
                                    0.0367
                                    0.0274
                                    0.0219
                                    0.0317
                                    0.0303
                                     0.038
                                    0.0521
                                    0.0423
                                    0.0338
                                    0.0305
                                    0.0628
                                    0.0209
                                      17
                                    0.0163
                                     0.029
                                     0.025
                                    0.0137
                                    0.0244
                                    0.0264
                                    0.0184
                                    0.0367
                                    0.0323
                                    0.0279
                                    0.0291
                                    0.0524
                                    0.0127
                                      18
                                    0.0133
                                    0.0249
                                    0.0175
                                    0.0136
                                    0.0201
                                    0.0219
                                    0.0219
                                    0.0167
                                    0.0225
                                    0.0777
                                     0.02
                                     0.038
                                    0.0086
                                      19
                                    0.0111
                                    0.0209
                                    0.0142
                                    0.0073
                                    0.0148
                                     0.019
                                    0.0177
                                    0.0149
                                    0.0179
                                    0.0137
                                    0.0175
                                    0.0292
                                    0.0052
                                      20
                                    0.0088
                                    0.0178
                                     0.012
                                     0.007
                                    0.0168
                                    0.0192
                                    0.0226
                                    0.0233
                                    0.0162
                                    0.0213
                                     0.013
                                    0.0272
                                     0.004
                                      21
                                    0.0071
                                     0.015
                                    0.0106
                                    0.0075
                                    0.0188
                                    0.0281
                                    0.0255
                                    0.0166
                                     0.022
                                    0.0132
                                    0.0171
                                    0.0337
                                    0.0031
                                      22
                                    0.0053
                                    0.0124
                                    0.0108
                                     0.008
                                    0.0187
                                    0.0214
                                    0.0145
                                    0.0256
                                    0.0211
                                    0.0535
                                    0.0221
                                    0.0343
                                    0.0031
                                      23
                                    0.0045
                                    0.0097
                                    0.0092
                                    0.0073
                                    0.0174
                                    0.0168
                                    0.0173
                                    0.0147
                                    0.0188
                                     0.017
                                    0.0196
                                    0.0317
                                    0.0019
                                      24
                                    0.0044
                                     0.008
                                     0.007
                                    0.0057
                                     0.018
                                    0.0156
                                    0.0175
                                    0.0132
                                    0.0171
                                    0.0061
                                    0.0191
                                     0.025
                                    0.0032
                                      25
                                    0.0037
                                    0.0065
                                    0.0071
                                    0.0053
                                    0.0151
                                    0.0131
                                    0.0153
                                    0.0068
                                    0.0154
                                    0.0064
                                    0.0141
                                    0.0174
                                    0.0009
                                      26
                                    0.0031
                                    0.0053
                                    0.0049
                                    0.0037
                                    0.0132
                                    0.0113
                                    0.0131
                                    0.0068
                                    0.0132
                                    0.0055
                                     0.015
                                    0.0177
                                    0.0009
                                      27
                                    0.0028
                                    0.0042
                                     0.004
                                    0.0031
                                    0.0104
                                    0.0088
                                    0.0101
                                    0.0056
                                    0.0113
                                    0.0048
                                    0.0152
                                    0.0145
                                    0.0007
                                      28
                                     0.002
                                    0.0025
                                    0.0024
                                    0.0019
                                    0.0041
                                    0.0083
                                    0.0037
                                    0.0025
                                    0.0067
                                    0.0028
                                    0.0098
                                    0.0062
                                    0.0003
                                      29
                                    0.0016
                                    0.0017
                                    0.0019
                                    0.0015
                                    0.0035
                                    0.0045
                                    0.0027
                                    0.0029
                                    0.0067
                                    0.0028
                                    0.0057
                                    0.0073
                                    0.0004
                                      30+
                                    0.0025
                                    0.0016
                                    0.0016
                                    0.0012
                                    0.0047
                                    0.0039
                                    0.0047
                                    0.0035
                                    0.0066
                                    0.0027
                                    0.0039
                                    0.0089
                                    0.0004

Forecasting and Backcasting Age Distributions
Since purchasing registration data for all historic years is prohibitively costly and impossible for future years, an algorithm was developed to forecast and backcast age distributions from the 2011 age distribution described above for all other calendar years in the model. In prior versions of MOVES, these age distributions were calculated during the model run using sales estimates and assuming a constant survival rate. In MOVES2014, age distributions for national level runs were pre-calculated using updated sales estimates and assuming a dynamic survival rate. However, while sales data for historic years are well known and projections for future years are common in economic modeling, historic and projected vehicle survival are not well studied. For MOVES2014, a generic survival rate was scaled up or down for each calendar year based on our assumptions of sales and changes in total populations. The following three sections detail the derivation of the generic survival rate and the algorithms used to forecast and backcast age distributions using an adjusted survival rate in each year.
      
Generic Survival Rates
The survival rate describes the fraction of vehicles of a given source type and age that remain on the road from one year to the next. Although this rate changes from year to year, a single generic rate was calculated from available data. While the use of this generic rate is described in the next couple of sections, its derivation is specified here.

Survival rates for motorcycles were calculated based on a smoothed curve of retail sales and 2008 registration data as described in a study conducted for the EPA. Survival rates for passenger cars, passenger trucks and light commercial trucks came from NHTSA's survivability Table 3 and Table 4. These survival rates are based on a detailed analysis of Polk vehicle registration data from 1977 to 2002. We modified these rates to consistent with the MOVES format using the following guidelines:

          *       NHTSA rates for light trucks were used for both the MOVES passenger truck and light commercial truck source types.
          *       MOVES calculates emissions for vehicles up to age 30 (with all older vehicles lumped into the age 30 category), but NHSTA car survival rates were available only to age 25. Therefore, we extrapolated car rates to age 30 using the estimated survival rate equation in Section 3.1 of the NHTSA report. When converted to MOVES format, this caused a striking discontinuity at age 26 which we removed by interpolating between ages 25 and 27.
          *       According to the NHTSA methodology, NHTSA age 1 corresponds to MOVES ageID 2, so the survival fractions were shifted accordingly. 
          *       Because MOVES requires survival rates for ageIDs < 2, these values were linearly interpolated with the assumption that the survival rate prior to ageID 0 is 1. Effectively, this results in a near constant survival rate until ageID 3 for light-duty vehicles and until ageID 4 for heavy-duty vehicles.
          *       NHTSA defines survival rate as the ratio of the number of vehicles remaining in the fleet at a given year as compared to a base year. However, MOVES defines the survival rate as the ratio of vehicles remaining from one year to the next, so we transformed the NHTSA rates accordingly.
          
Because MOVES ageID 30 is intended to represent all vehicles 30 years old and greater, this age category can grow quite large as our age distribution algorithm eventually transfers all vehicles to this age group. To assure that the population of very old vehicles does not grow excessively, the generic survival rate for ageID 30 was set to 0.3. The actual survival rate of these age 30+ vehicles is unknown. 
          
Quantitatively, the following piecewise formulas were used to derive the MOVES survival rates. In them, sa represents the MOVES survival rate at age a, and σa represents the NHTSA survival rate at age a. When this generic survival rate is discussed below, the shorthand notation S0 will represent a one-dimensional array of sa values at each permissible age a as described below.
Age 0:
                                  s0=1-1-σ23
                                                                     Equation 5
Age 1:
                                s1=1-2(1-σ2)3
                                                                     Equation 6
Age 2-29:
                             sa=s2...29=σa-1σa-2
                                                                     Equation 7
Age 30:
                                    s30=0.3
                                                                     Equation 8

With limited data available on heavy-duty vehicle scrappage, survivability for all other source types came from the Transportation Energy Data Book. We used the heavy-duty vehicle survival rates for model year 1980 (TEDB32, Table 3.14). The 1990 model year rates were not used because they were significantly higher than rates for the other model years in the analysis (i.e. 45 percent survival rate for 30 year-old trucks), and seemed unrealistically high. While limited data exists to confirm this judgment, a snapshot of 5-year survival rates can be derived from VIUS 1992 and 1997 results for comparison. According to VIUS, the average survival rate for model years 1988-1991 between the 1992 and 1997 surveys was 88 percent. The comparable survival rate for 1990 model year heavy-duty vehicles from TEDB was 96 percent, while the rate for 1980 model year trucks was 91 percent. This comparison lends credence to the decision that the 1980 model year survival rates are more in line with available data. TEDB does not have separate survival rates for medium-duty vehicles, so it was necessary to apply the heavy-duty rates uniformly across the bus, single unit truck, and combination truck categories. The TEDB survival rates were transformed into MOVES format in the same way as the NHTSA rates, including setting age 30+ survival rates to 0.3 for all source types.

The resulting survival rates are listed in the default database's SourceTypeAge table. Please note that since MOVES2014 does not calculate age distributions during a run, these values are not actively used by MOVES. However, they were used in the development of the national age distributions stored in the SourceTypeAgeDistribution table, and remain in the default database for reference.

                 Table 7-2 Survival Rate by Age and HPMS Class
                                      Age
                                  Motorcycles
                              Light-Duty Vehicles
                                     Buses
                              Single Unit Trucks
                              Combination Trucks
                                       
                                       
                                Passenger Cars
                               Passenger Trucks
                              Light Comm. Trucks
                                       
                                       
                                       
                                       0
                                     1.000
                                     0.997
                                     0.991
                                     1.000
                                     1.000
                                     1.000
                                       1
                                     0.979
                                     0.997
                                     0.991
                                     1.000
                                     1.000
                                     1.000
                                       2
                                     0.940
                                     0.997
                                     0.991
                                     1.000
                                     1.000
                                     1.000
                                       3
                                     0.940
                                     0.993
                                     0.986
                                     1.000
                                     1.000
                                     1.000
                                       4
                                     0.940
                                     0.990
                                     0.981
                                     0.990
                                     0.990
                                     0.990
                                       5
                                     0.940
                                     0.986
                                     0.976
                                     0.980
                                     0.980
                                     0.980
                                       6
                                     0.940
                                     0.981
                                     0.970
                                     0.980
                                     0.980
                                     0.980
                                       7
                                     0.940
                                     0.976
                                     0.964
                                     0.970
                                     0.970
                                     0.970
                                       8
                                     0.940
                                     0.971
                                     0.958
                                     0.970
                                     0.970
                                     0.970
                                       9
                                     0.940
                                     0.965
                                     0.952
                                     0.970
                                     0.970
                                     0.970
                                      10
                                     0.940
                                     0.959
                                     0.946
                                     0.960
                                     0.960
                                     0.960
                                      11
                                     0.940
                                     0.953
                                     0.940
                                     0.960
                                     0.960
                                     0.960
                                      12
                                     0.940
                                     0.912
                                     0.935
                                     0.950
                                     0.950
                                     0.950
                                      13
                                     0.940
                                     0.854
                                     0.929
                                     0.950
                                     0.950
                                     0.950
                                      14
                                     0.940
                                     0.832
                                     0.913
                                     0.950
                                     0.950
                                     0.950
                                      15
                                     0.940
                                     0.813
                                     0.908
                                     0.940
                                     0.940
                                     0.940
                                      16
                                     0.940
                                     0.799
                                     0.903
                                     0.940
                                     0.940
                                     0.940
                                      17
                                     0.940
                                     0.787
                                     0.898
                                     0.930
                                     0.930
                                     0.930
                                      18
                                     0.940
                                     0.779
                                     0.894
                                     0.930
                                     0.930
                                     0.930
                                      19
                                     0.940
                                     0.772
                                     0.891
                                     0.920
                                     0.920
                                     0.920
                                      20
                                     0.940
                                     0.767
                                     0.888
                                     0.920
                                     0.920
                                     0.920
                                      21
                                     0.940
                                     0.763
                                     0.885
                                     0.920
                                     0.920
                                     0.920
                                      22
                                     0.940
                                     0.760
                                     0.883
                                     0.910
                                     0.910
                                     0.910
                                      23
                                     0.940
                                     0.757
                                     0.880
                                     0.910
                                     0.910
                                     0.910
                                      24
                                     0.940
                                     0.757
                                     0.879
                                     0.910
                                     0.910
                                     0.910
                                      25
                                     0.940
                                     0.754
                                     0.877
                                     0.900
                                     0.900
                                     0.900
                                      26
                                     0.940
                                     0.754
                                     0.875
                                     0.900
                                     0.900
                                     0.900
                                      27
                                     0.940
                                     0.567
                                     0.875
                                     0.900
                                     0.900
                                     0.900
                                      28
                                     0.940
                                     0.752
                                     0.873
                                     0.890
                                     0.890
                                     0.890
                                      29
                                     0.940
                                     0.752
                                     0.872
                                     0.890
                                     0.890
                                     0.890
                                      30
                                     0.300
                                     0.300
                                     0.300
                                     0.300
                                     0.300
                                     0.300

2012-2050 Age Distributions
The 2012-2050 age distributions were derived from the 2011 age distribution described above using population, survival, and sales projections. Age distributions are easily calculated from population counts, if the populations are known by age:
                                       
                                   fa,y=paPy
                                                                    Equation 9 
Here, fa,y is the age fraction to be calculated, pa is the population of vehicles at age a, and Py is the total population in calendar year y. In this section, arrow notation will be used if the operations are to be performed at the individual age level. For example, fy would be used to represent all age fractions in calendar year y. Another example is Py; it represents an array of pa values at each permissible age in calendar year y. In contrast, Py represents the total population in year y.

Intuitively, projecting an age distribution forward one year involves removing the vehicles scrapped in the base year and adding the new vehicles sold in the next year, as shown in Equation 10:
                                       
                                Py+1=Py-Ry+Ny+1
                                                                   Equation 10 
where Py+1 is the population (known at each age) of the next year, Py is the population in the base year, Ry is the population of vehicles removed in the in the base year, and Ny+1 is new vehicles sold in the next year. Please note that the final term only includes new vehicles at age 0; if the equation is evaluated for any a>0, the sales term is zero. Equation 10 can be used algorithmically to forecast a known population distribution as follows:

   1. Starting with the base population distribution (Py), remove the number of vehicles that did not survive (Ry) at each age level.
   2. Increase the population age index by one (for example, 3 year old vehicles are reclassified as 4 year old vehicles).
   3. Add new vehicle sales (Ny+1) as the age 0 cohort.
   4. Combine the new age 30 and 31 vehicles into a single age 30 group.
   5. This results in the next year population distribution (Py+1). If this algorithm is to be repeated, Py+1 becomes Py for the next iteration.

Unfortunately, as described in the section above, the only survival information we have is a single snapshot. Because vehicle populations and new sales change differentially (for example, the historic populations shown in Section 5.1 level off during the recent recession; at the same time, sales of most vehicle types plummeted), it is important to adjust the survival curve in response to changes in population and sales. We did so by defining a scalar adjustment factor ky that can be algebraically calculated from population and sales estimates. Its use in determining the population of vehicles removed and its relationship to the generic survival rate S0 is given by Equation 11. Note that the open circle operator (∘) represents entrywise product; that is, each element in an array is multiplied by the corresponding element in the other one, and it results in an array with the same number of elements.
                                       
                               Ry=ky∙1-S0∘Py
                                                                    Equation 11
      
Substituting Equation 11 into Equation 10 yields:
                                       
                         Py+1=Py-ky∙(1-S0)∘Py+Ny+1
                                                                    Equation 12
Since both the value of the scalar adjustment factor and the actual distribution of the next year's population are unknown, Equation 12 can't be used yet. However, by using an estimate of next year's total population, it can be transformed into:
      
                                       
                          Py+1=Py-kya1-S0∘Py +Ny+1
                                                                   Equation 13 
This was algebraically solved for ky and evaluated for each HPMS category using the following information:

   * Total populations Py and Py+1 by HPMS category. For analysis year 2011, this information is described source type in Section 5.1 and simply needs to be summed by HPMS category for use here. For years 2012+, this information is described in Section 5.2. 
   * Survival S0 by HPMS category, which is described in Section 7.1.2.1. 
   * Population distribution Py by HPMS category. For analysis year 2011, this information came from combining the total populations described in Section 5.1 with the age distributions described in Section 7.1.1.2 and summing by HPMS category. For years 2012+, this comes from Py+1 of the previous year.
   * New vehicle sales Ny+1 by HPMS category, which are derived from AEO2014. The projection of sales was calculated as a percentage of the total population using the vehicle category mapping discussed in Section 4.2; this is converted to the number of new vehicles by multiplying by the HPMS category population.

After determining ky by HPMS category, Equation 12 was used with the following information to compute the next year's population and then age distribution by source type:
      
         *       Population distribution Py by source type. For analysis year 2011, this information came from combining the total populations described in Section 5.1 with the age distributions described in Section 7.1.1.2. For years 2012+, this comes from Py+1 of the previous year.
         *       The scalar adjustment factor ky and generic survival rate S0 applied by source type using the HPMS to source type mapping described by Table 2-12-12-12-1. Please note that limits were placed on the ky(1-S0) term of Equation 12: the value of this term for each age was restricted to being between 0 and 1.
         *       New vehicle sales Ny+1, determined as a percentage of the total population in AEO2014 as discussed above; this is converted to the number of new vehicles by multiplying by the total source type population.

With all of this information, the population distributions were algorithmically determined for years 2012-2050. The resulting total source type populations (Py) are stored in the SourceTypeYear table of the default database. The resulting age distributions are stored in the SourceTypeAgeDistribution table.

1999-2010 Age Distributions

The method used to backcast the 1999-2010 age distributions from the 2011 distribution is very similar to the forecasting method described above. For backcasting an age distribution one year, Equation 10 of the previous section can be rewritten as:
                                       
                               Py-1=Py-Ny+Ry-1 
                                                                   Equation 14 
Essentially, this can be thought of as taking the base year's population distribution, removing the vehicles sold (or added to the population) in that year, and then adding the vehicles that were removed in the year before. This can be represented algorithmically as follows:

   1. Starting with the base population distribution (Py), remove the age 0 vehicles (Ny).
   2. Decrease the population age index by one (for example, 3 year old vehicles are reclassified as 2 year old vehicles).
   3. Add the vehicles that were removed in the previous year (Ry-1).
   4. This results in the previous year population distribution (Py-1). If this algorithm is to be repeated, Py-1 becomes Py for the next iteration.

The equation governing vehicle removal discussed the previous section is also applicable here. Taking careful note of the subscripts, Equation 11 and Equation 14 can be combined:
                                       
                         Py-1=Py-Ny+ky-1∙1-S0∘Py-1
                                                                   Equation 15 
As in the forecasting situation, the value of the scalar adjustment factor and the actual distribution of the previous year's population are unknown. With a similar strategy of using the previous year's known total population, Equation 15 can be transformed into:
                                       
                         Py-1=Py-Ny+ky-1a1-S0∘Py-1 
                                                                   Equation 16 
However, this still leaves a Py-1 term, which is unavoidable because the total number of vehicles removed is dependent on the age distribution of those vehicles. To properly solve Equation 16 for ky-1 and Py-1, a numerical method of approximation could be employed. However, due to lack of resources, Py was used as a simple approximation of Py-1 on the left hand side of Equation 16. The following sources were used to determine ky-1 by HPMS category:

   * Total populations Py and Py-1 by HPMS category. For all historic analysis years, this information is described source type in Section 5.1 and simply needs to be summed by HPMS category across all ages for use here.
   * Survival S0 by HPMS category, which is described in Section 7.1.2.1. 
   * Population distribution Py by HPMS category. For analysis year 2011, this information came from combining the total populations described in Section 5.1 with the age distributions described in Section 7.1.1.2 and summing by HPMS category. For other years, this comes from Py-1 of the previous iteration.
   * New vehicle sales Ny+1 data, which was collected by source type from a variety of sources. Each of these was summed by HPMS category. Motorcycles sales comes from the Motorcycle Industry Council; sales data for passenger cars, passenger trucks, light commercial trucks, refuse trucks, short-haul and long-haul single unit trucks, and short-haul and long-haul combination trucks comes from TEDB and VIUS; transit buses production estimates are based on EPA certification data; and school bus sales came from the School Bus Fleet Fact Book. No sales data were available for intercity buses, so the other bus categories were used as a surrogate. That is, the total transit bus production and school bus sales as a percentage of the transit and school bus populations in each year were applied to the intercity bus populations to estimate their sales. Similarly, no sales data were available for motor homes, so a sales fraction was estimated by averaging the sales of refuse, short-haul, and long-haul single unit trucks as a fraction of their total population.

After determining ky-1 by HPMS category, Equation 15 was used with the following information to compute the previous year's age distribution by source type:
      
         *       Population distribution Py by source type. For analysis year 2011, this information came from combining the total populations described in Section 5.1 with the age distributions described in Section 7.1.1.2. For other years, this comes from Py-1 of the previous iteration.
         *       The scalar adjustment factor ky-1 and generic survival rate S0 applied by source type using the HPMS to source type mapping described by Table 2-12-12-12-1. As with before, limits were placed on the ky(1-S0) term, such that the value of this term for each age was restricted to being between 0 and 1. Also, the Py-1 term used when calculating the number of vehicles removed was approximated by  Py.
         *       New vehicle sales Ny+1, from the sources listed above and applied by source type.

With all of this information, the population distributions were algorithmically determined for years 1999-2010. The resulting age distributions are stored in the SourceTypeAgeDistribution table.

      
Relative Mileage Accumulation Rate 

MOVES uses a relative mileage accumulation rate (RMAR) in combination with source type populations (see Section 5) and age distributions described earlier in this section to distribute the total annual miles driven by each HPMS vehicle type (see Section 4) to each source type and age group. Using this approach, the vehicle population and the total annual vehicle miles traveled (VMT) can vary from calendar year to calendar year, but the proportional travel by an individual vehicle of each age will not vary.

VMT is provided, either by default values or by user input, by the five Highway Performance Monitoring System (HPMS) vehicle classifications.  These classifications are further broken down into the groupings of the MOVES source use types, as described in Section 2.1. 

The RMAR is determined within each HPMS vehicle classification such that the annual mileage accumulation for a single vehicle of each age of a source type is relative to the mileage accumulation of all of the source types and ages within the HPMS vehicle classification.  For example, passenger cars, passenger trucks and light commercial trucks are all within the same HPMS vehicle classification.  By definition, new (age 0) passenger trucks and light commercial trucks have a RMAR of one (1.0).  Based on the data, new passenger cars have a RMAR of 0.885.  This means that when the VMT assigned to the HPMS vehicle classification (25) is allocated to passenger cars, passenger trucks and light commercial trucks, a passenger car of age 0 will be assigned only 88.5% of the VMT assigned to a passenger truck or light commercial truck of age 0.

The RMAR values for MOVES2014 for the source types 11 (motorcycles), 41 (intercity buses), 42 (transit buses), 43 (school buses) and 54 (motorhomes) were not changed from the values used in MOVES2010b.    Passenger car and light-duty truck RMAR values were recalculated to reflect the change in the HPMS vehicle classifications used for VMT input and the remaining heavy-duty vehicle classifications were updated with data from the 2002 Vehicle Inventory and Use Survey (VIUS) and recalculated.

Motorcycles 
The RMAR values for motorcycles in MOVES2014 were not changed from MOVES2010b estimates. The MOVES2010b RMAR values were calculated from MARs for motorcycles (category 11) based on the model years and odometer readings listed in motorcycle advertisements. A stratified sample of about 1,500 ads were examined. A modified Weibull curve was fit to the data to develop the relative mileage accumulation rates used in MOVES.[37]

Passenger Cars, Passenger Trucks and Light Commercial Trucks
In MOVES2010b, passenger cars were not included in the same HPMS vehicle classification as for passenger trucks and light commercial trucks.  For MOVES2014, the MOVES2010b passenger car RMAR values were adjusted to reflect the relative difference in annual mile accumulation between passenger cars and the light trucks.  Analysis of the data determined that new passenger cars (age 0) accumulate only 88.5% of the annual miles accumulated by new light trucks.  All of the RMAR values for passenger cars were adjusted to be 88.5% of their previous values.

The MOVES2010b RMAR values for passenger cars, passenger trucks and light commercial trucks (categories 21, 31 & 32) were taken from the NHTSA report on survivability and mileage schedules.[38] In the NHTSA analysis, annual mileage by age was determined for cars and for trucks using data from the 2001 National Household Travel Survey. In this NHTSA analysis, vehicles that were less than one year old at the time of the survey were classified as "age 1", etc. NHTSA used cubic regression to smooth the VMT by age estimates. 

We used NHTSA's regression coefficients to extrapolate mileage to ages 26 through 30 not covered by the report. Since passenger trucks had the highest MAR in what was then the Light-Duty Truck HPMS category, each source type's mileage by age was divided by passenger truck mileage at "age 1" to determine a relative MAR. For consistency with MOVES age categories, we then shifted the relative MARs such that the NHTSA "age 1" ratio was used for MOVES age 0, etc. We used NHTSA's light truck VMT to determine relative MARs for both passenger trucks and light commercial trucks.

Since a newer version of the National Household Travel Survey was available, we conducted a preliminary analysis of the impact of updating the MARs based on the 2009 National Household Travel Survey. This resulted in changes in MOVES' allocation of VMT by one percent or less for each of the vehicle categories covered by the survey. As such, we feel that the MARs developed from the 2001 survey are still reasonable for use in MOVES2014.

Buses
The RMAR values for all bus categories in MOVES2014 were not changed from MOVES2010b estimates. The Intercity Bus (category 41) annual mileage accumulation rate is taken from Motorcoach Census 2000. The data did not distinguish vehicle age, so the same MAR (59,873 miles per year) was used for each age. The School Bus (category 43) annual mileage accumulation rate (9,939 miles per year) is taken from the 1997 School Bus Fleet Fact Book.  The MOVES model assumes the same annual mileage accumulation rate for each age. The Transit Bus (category 42) annual mileage accumulation rate are taken from the MOBILE6 values for diesel transit buses (HDDBT). This mileage data was obtained from the 1994 Federal Transportation Administration survey of transit agencies. The MOBILE6 equation was extended to calculate values for ages 26 through 30.
      
Other Heavy-Duty Vehicles 
The RMAR values for source types 51 (refuse trucks), 52 (short haul single unit trucks), 53 (long haul single unit trucks), 61 (short haul combination trucks) and 62 (long haul combination trucks) were updated using the data from the 2002 Vehicle Inventory and Use Survey (VIUS).  The total reported annual miles traveled by trucks in each source type was divided by the vehicle population to determine the average annual miles traveled per truck by source type.   

             Table 7-3 2002 VIUS Annual Mileage Accumulation Rates
                                      Age
                                  Model Year
                              Single Unit Trucks
                              Combination Trucks
                                       
                                       
                                  Refuse (51)
                                Short-haul (52)
                                Long-haul (53)
                                Short-haul (61)
                                Long-haul (62)
                                       0
                                     2002
                                    26,703
                                    21,926
                                    40,538
                                    119,867
                                    109,418
                                       1
                                     2001
                                    32,391
                                    22,755
                                    28,168
                                    114,983
                                    128,287
                                       2
                                     2000
                                    31,210
                                    24,446
                                    30,139
                                    110,099
                                    117,945
                                       3
                                     1999
                                    31,444
                                    23,874
                                    49,428
                                    105,215
                                    110,713
                                       4
                                     1998
                                    31,815
                                    21,074
                                    33,266
                                    100,331
                                    99,925
                                       5
                                     1997
                                    28,450
                                    21,444
                                    23,784
                                    95,447
                                    94,326
                                       6
                                     1996
                                    25,462
                                    16,901
                                    21,238
                                    90,563
                                    85,225
                                       7
                                     1995
                                    30,182
                                    15,453
                                    27,562
                                    85,679
                                    85,406
                                       8
                                     1994
                                    20,722
                                    13,930
                                    21,052
                                    80,795
                                    71,834
                                       9
                                     1993
                                    25,199
                                    13,303
                                    11,273
                                    75,911
                                    71,160
                                      10
                                     1992
                                    23,366
                                    11,749
                                    18,599
                                    71,026
                                    67,760
                                      11
                                     1991
                                    18,818
                                    13,675
                                    15,140
                                    66,142
                                    80,207
                                      12
                                     1990
                                    12,533
                                    11,332
                                    13,311
                                    61,258
                                    48,562
                                      13
                                     1989
                                    15,891
                                     9,795
                                     9,796
                                    56,374
                                    64,473
                                      14
                                     1988
                                    19,618
                                     9,309
                                    12,067
                                    51,490
                                    48,242
                                      15
                                     1987
                                    12,480
                                     9,379
                                    16,606
                                    46,606
                                    58,951
                                      16
                                     1986
                                    12,577
                                     4,830
                                     8,941
                                    41,722
                                    35,897
                                      0-3
                               1999-2002 Average
                                    30,437
                                    23,250
                                    37,069
                                    61,240
                                    116,591

For each source type, in the first few years, the data showed only small differences in the annual miles per vehicle and no trend.  After that, the average annual miles per vehicle declined in a fairly linear manner, at least until the vehicles are at age 16 (the limit of the data).  MOVES, however, requires mileage accumulation rates for all ages to age 30.  For MOVES2014, we assumed that the mileage accumulation rate at age 30 would be the same as used for MOVES2010b.

Mileage accumulation rates for these vehicles were determined for each age from 0 to 30 using the following method:

      1) Ages 0 through 3 use the same average annual mileage accumulation rate for age 0-3 vehicles of that source type.
      2) Ages 4 through 16 use mileage accumulation rates calculated using a linear regression of the VIUS data for ages three through 16,
      3) Ages 17 through 29 use values from interpolation between the values in age 16 and age 30.
      4) Age 30 uses the MOVES2010b mileage accumulation rate for age 30.  These rates were allocated to MOVES source types from MOBILE6 mileage accumulation rates, which were derived from the 1992 TIUS as documented in the Arcadis report.

Table 7-4 Regression Statistics for Heavy-Duty Truck Annual Mileage Accumulation Rates Ages 4-16
                                  Measurement
                               Refuse Truck (51)
                          Single Unit Short-haul (52)
                          Single Unit Long-haul (53)
                          Combination Short-haul (61)
                          Combination Long-haul (62)
Average*
                                    30,437
                                    23,250
                                    37,069
                                    61,240
                                    116,591

Intercept
                                    36,315
                                    25,442
                                    36,305
                                    65,773
                                    119,867
Slope
                                    -1,510
                                    -1,209
                                    -1,794
                                    -3,447
                                    -4,884

Age 30
                                    0.0320
                                    0.0518
                                    0.1025
                                    0.0320
                                    0.0571
* Average sample annual miles traveled for ages 0 through 3.

The resulting relative mileage accumulation rates are shown in Table 7-57-57-57-5 below.  Note that the first four values are identical and then decline linearly to age 16 and then linearly to age 30 with a different slope.

Motor Homes 
Motor home relative mileage accumulation rates for MOVES2014 are unchanged from MOVES2010b.  For motor homes (sourceTypeID 54), the initial MARs were taken from an independent research study conducted in October 2000 among members of the Good Sam Club. The members are active recreation vehicle (RV) enthusiasts who own motor homes, trailers and trucks. The average annual mileage was estimated to be 4,566 miles. The data did not distinguish vehicle age, so the same MAR was used for each age.

      Table 7-5 Relative Mileage Accumulation Rates for Heavy-Duty Trucks
                                     ageID
                                  Refuse (51)
                          Short Haul Single Unit (52)
                          Long Haul Single Unit (53)
                                Motor Home (54)
                          Short Haul Combination (61)
                          Long Haul Combination (62)
                                       0
                                    1.0000
                                    0.6864
                                    0.9729
                                    0.0590
                                    0.5269
                                    1.0000
                                       1
                                    1.0000
                                    0.6864
                                    0.9729
                                    0.0590
                                    0.5269
                                    1.0000
                                       2
                                    1.0000
                                    0.6864
                                    0.9729
                                    0.0590
                                    0.5269
                                    1.0000
                                       3
                                    1.0000
                                    0.6864
                                    0.9729
                                    0.0590
                                    0.5269
                                    1.0000
                                       4
                                    0.9525
                                    0.6484
                                    0.9165
                                    0.0590
                                    0.4941
                                    0.9536
                                       5
                                    0.9050
                                    0.6103
                                    0.8601
                                    0.0590
                                    0.4613
                                    0.9072
                                       6
                                    0.8575
                                    0.5723
                                    0.8036
                                    0.0590
                                    0.4286
                                    0.8607
                                       7
                                    0.8099
                                    0.5343
                                    0.7472
                                    0.0590
                                    0.3958
                                    0.8143
                                       8
                                    0.7624
                                    0.4962
                                    0.6908
                                    0.0590
                                    0.3631
                                    0.7679
                                       9
                                    0.7149
                                    0.4582
                                    0.6343
                                    0.0590
                                    0.3303
                                    0.7215
                                      10
                                    0.6674
                                    0.4202
                                    0.5779
                                    0.0590
                                    0.2975
                                    0.6751
                                      11
                                    0.6199
                                    0.3821
                                    0.5215
                                    0.0590
                                    0.2648
                                    0.6286
                                      12
                                    0.5724
                                    0.3441
                                    0.4650
                                    0.0590
                                    0.2320
                                    0.5822
                                      13
                                    0.5249
                                    0.3061
                                    0.4086
                                    0.0590
                                    0.1993
                                    0.5358
                                      14
                                    0.4773
                                    0.2680
                                    0.3522
                                    0.0590
                                    0.1665
                                    0.4894
                                      15
                                    0.4298
                                    0.2300
                                    0.2957
                                    0.0590
                                    0.1338
                                    0.4430
                                      16
                                    0.3823
                                    0.1920
                                    0.2393
                                    0.0590
                                    0.1010
                                    0.3965
                                      17
                                    0.3573
                                    0.1808
                                    0.2293
                                    0.0590
                                    0.0950
                                    0.3723
                                      18
                                    0.3323
                                    0.1696
                                    0.2194
                                    0.0590
                                    0.0890
                                    0.3481
                                      19
                                    0.3073
                                    0.1585
                                    0.2094
                                    0.0590
                                    0.0830
                                    0.3238
                                      20
                                    0.2822
                                    0.1473
                                    0.1994
                                    0.0590
                                    0.0770
                                    0.2996
                                      21
                                    0.2572
                                    0.1361
                                    0.1894
                                    0.0590
                                    0.0710
                                    0.2753
                                      22
                                    0.2322
                                    0.1249
                                    0.1795
                                    0.0590
                                    0.0649
                                    0.2511
                                      23
                                    0.2072
                                    0.1138
                                    0.1695
                                    0.0590
                                    0.0589
                                    0.2268
                                      24
                                    0.1821
                                    0.1026
                                    0.1595
                                    0.0590
                                    0.0529
                                    0.2026
                                      25
                                    0.1571
                                    0.0914
                                    0.1496
                                    0.0590
                                    0.0469
                                    0.1783
                                      26
                                    0.1321
                                    0.0802
                                    0.1396
                                    0.0590
                                    0.0409
                                    0.1541
                                      27
                                    0.1071
                                    0.0691
                                    0.1296
                                    0.0590
                                    0.0349
                                    0.1298
                                      28
                                    0.0820
                                    0.0579
                                    0.1197
                                    0.0590
                                    0.0289
                                    0.1056
                                      29
                                    0.0570
                                    0.0467
                                    0.1097
                                    0.0590
                                    0.0229
                                    0.0814
                                      30
                                    0.0320
                                    0.0355
                                    0.0997
                                    0.0590
                                    0.0169
                                    0.0571

VMT Distribution of Source Type by Road Type 
For each source type, the RoadTypeVMTFraction field in the RoadTypeDistribution table stores the fraction of total VMT for each vehicle class that is traveled on each of the five roadway types. Users may supply the distribution VMT to vehicle classes for each road type for individual counties when using County Scale, however, for National Scale, the default distribution is applied to all locations.

The national default distribution of VMT to vehicle classes for each road type in MOVES2014 were derived to reflect the VMT data included in the 2011 National Emission Inventory (NEI) Version 1 (July 31, 2013).  This data is provided by states every three years as part of the NEI project and is supplemented by EPA estimates, based on Federal Highway Administration (FHWA) reports, when state supplied estimates are not available. 

The 2011 NEI v1 data is grouped by the Source Classification Code (SCC) used at that time and these older classifications do not cleanly map to the source types used by MOVES.  The VMT was mapped to the source types used by MOVES by calculating the fraction VMT for each source type found in each SCC classification result in a national MOVES2010b run for calendar year 2011.  The factors calculated from the MOVES201b run are shown in Section 20. (Appendix D: Driving Schedules and SCC Mappings).  The first seven digits of the 10 digit SCC (SCC7) indicate the vehicle classification.

The SCC road types map cleanly to the MOVES road types.  The eighth and ninth digits of the 10-digit SCC (SCC89) indicate the road type, as shown below in Table 8-1.

            Table 8-1 Mapping of SCC Road Types to MOVES Road Types
                          SCC Road Type Code (SCC89)
SCC Road Type
                              MOVES Road Type ID
MOVES Road Type
                                      11
Rural Interstate
                                       2
Rural Restricted Access
                                      13
Rural Other Principal Arterial
                                       3
Rural Unrestricted Access
                                      15
Rural Minor Arterial
                                       3
Rural Unrestricted Access
                                      17
Rural Major Collector
                                       3
Rural Unrestricted Access
                                      19
Rural Minor Collector
                                       3
Rural Unrestricted Access
                                      21
Rural  Local
                                       3
Rural Unrestricted Access
                                      23
Urban Interstate
                                       4
Urban Restricted Access
                                      25
Urban Other Freeways & Expressways
                                       4
Urban Restricted Access
                                      27
Urban Other Principal Arterial
                                       5
Urban Unrestricted Access
                                      29
Urban Minor Arterial
                                       5
Urban Unrestricted Access
                                      31
Urban Collector
                                       5
Urban Unrestricted Access
                                      33
Urban Local
                                       5
Urban Unrestricted Access

Once the SCC VMT values have been mapped to MOVES source types and road types, the national distribution of road type VMT by source type can be calculated from the NEI VMT estimates, summarized in Table 8-2. The off network road type (roadTypeID=1) is not used and is allocated none of the VMT.

           Table 8-2 MOVES2014 Road Type Distribution by Source Type
                                  Source Type
                                  Description
                                  Road Types
                                       
                                       
                                  Off Network
                               Rural Restricted
                              Rural Unrestricted
                               Urban Restricted
                              Urban Unrestricted
                                       
                                       
                                       
                                       1
                                       2
                                       3
                                       4
                                       5
                                      All
                                      11
 Motorcycle
                                       0
                                   0.0804768
                                   0.3019230
                                   0.1913280
                                   0.4262730
                                     1.000
                                      21
 Passenger Car
                                       0
                                   0.0847394
                                   0.2344520
                                   0.2374280
                                   0.4433810
                                     1.000
                                      31
 Passenger Truck
                                       0
                                   0.0859437
                                   0.2753580
                                   0.2178360
                                   0.4208630
                                     1.000
                                      32
 Light Commercial Truck
                                       0
                                   0.0866643
                                   0.2755600
                                   0.2180390
                                   0.4197360
                                     1.000
                                      41
 Intercity Bus
                                       0
                                   0.1409270
                                   0.2811960
                                   0.2195920
                                   0.3582850
                                     1.000
                                      42
 Transit Bus
                                       0
                                   0.1384440
                                   0.2813130
                                   0.2196020
                                   0.3606420
                                     1.000
                                      43
 School Bus
                                       0
                                   0.1383910
                                   0.2813150
                                   0.2196020
                                   0.3606920
                                     1.000
                                      51
 Refuse Truck
                                       0
                                   0.2396390
                                   0.2717580
                                   0.2524620
                                   0.2361420
                                     1.000
                                      52
 Single Unit Short-haul Truck
                                       0
                                   0.1635030
                                   0.2869150
                                   0.2345890
                                   0.3149930
                                     1.000
                                      53
 Single Unit Long-haul Truck
                                       0
                                   0.1638220
                                   0.2869700
                                   0.2346570
                                   0.3145510
                                     1.000
                                      54
 Motor Home
                                       0
                                   0.1233290
                                   0.2876100
                                   0.2255300
                                   0.3635310
                                     1.000
                                      61
 Combination Short-haul Truck
                                       0
                                   0.2366730
                                   0.2744240
                                   0.2516600
                                   0.2372430
                                     1.000
                                      62
 Combination Long-haul Truck
                                       0
                                   0.2476010
                                   0.2705480
                                   0.2543110
                                   0.2275400
                                     1.000

Average Speed Distributions
Average speed is used in MOVES to convert VMT inputs into the Source Hours Operating (SHO) units that MOVES uses for internal calculations. It is also used to select appropriate driving cycles, which are then used to calculate exhaust running operating mode distributions at the national, county (and sometimes project) level. Instead of using a single average speed in these tasks, MOVES2014 uses a distribution of average speeds by bin. The AvgSpeedDistribution table lists the default fraction of driving time for each source type, road type, day, and hour in each average speed bin. The fractions sum to one for each combination of source type, road type, day, and hour. The MOVES average speed bins are defined in Table 9-19-19-19-1. 
                                       
                     Table 9-1 MOVES Speed Bin Categories
                                      Bin
                              Average Speed (mph)
                           Average Speed Range (mph)
                                       1
                                      2.5
                              speed < 2.5 mph
                                       2
                                       5
                       2.5 mph <= speed < 7.5 mph
                                       3
                                      10
                       7.5 mph <= speed < 12.5 mph
                                       4
                                      15
                      12.5 mph <= speed < 17.5 mph
                                       5
                                      20
                      17.5 mph <= speed < 22.5 mph
                                       6
                                      25
                      22.5 mph <= speed < 27.5 mph
                                       7
                                      30
                      27.5 mph <= speed < 32.5 mph
                                       8
                                      35
                      32.5 mph <= speed < 37.5 mph
                                       9
                                      40
                      37.5 mph <= speed < 42.5 mph
                                      10
                                      45
                      42.5 mph <= speed < 47.5 mph
                                      11
                                      50
                      47.5 mph <= speed < 52.5 mph
                                      12
                                      55
                      52.5 mph <= speed < 57.5 mph
                                      13
                                      60
                      57.5 mph <= speed < 62.5 mph
                                      14
                                      65
                      62.5 mph <= speed < 67.5 mph
                                      15
                                      70
                      67.5 mph <= speed < 72.5 mph
                                      16
                                      75
                             72.5 mph <= speed

Light-Duty Average Speed Distributions
For MOVES2014, the light-duty average speed distributions are based on in-vehicle global position system (GPS) data. The data was obtained through a contract with Eastern Research Group (ERG), who subcontracted with TomTom to provide summarized vehicle GPS data. TomTom makes in-vehicle GPS navigation devices as well as supports cell-phone navigation applications. ERG provided the US EPA with updated values for the AvgSpeedDistribution calculated from the TomTom delivered data based on their consumers, which "virtually all" use them in light-duty cars, trucks and vans. 

Some of the characteristics of the TomTom GPS data to consider are as follows:
      
          *     Data is self-selective. Data is only recorded from users of TomTom GPS units and an iPhone application. Additionally, TomTom data is only collected when the units are on. This creates bias not only for users, but also for types of driving. Anecdotally, drivers that own GPS units are less likely to use them when they drive in familiar areas in comparison with unfamiliar areas. Compared to the default VMT by road type information in MOVES, TomTom over represents behavior on rural restricted access roads, which suggests the higher usage of GPS on vacations and business trips.
          *     No information on vehicle type is available. TomTom suggests that "virtually all" the vehicles are light-duty cars, trucks, and vans. MOVES allows for separate average speed distributions for each source type. However, due to a lack of information on other source types, the average speed distribution derived from the TomTom light-duty GPS data is applied to all source types, although the combination long-haul trucks distribution was adjusted as described at the end of this section. Other heavy-duty source types such as single unit long-haul trucks were not adjusted. We recognize this as a shortcoming of MOVES, and look to incorporate source-type specific average speed information in the future.
          *     The MOVES average speed distributions are based on the average speed in each roadway segment, not second-by-second speed measurements.
          *     Only data that is associated with the vehicle network is included in the average speed delivery. As part of the quality control methods, TomTom excludes data that does not "snap to the roadway grid" to remove points caused by loss of satellite signal and errors while the TomTom unit is trying to acquire the satellite signal. TomTom uses data quality control techniques to minimize data arising from non-light-duty-vehicle use, such as from pedestrians, bicycles, and airplanes

Under direction of ERG, TomTom queried its database of historic traffic probes to produce a table of total distance and total time as a function of road type, weekday/weekend, hour of the day, and average speed bin for the calendar year 2011 for the 50 US states and the District of Columbia. TomTom delivered a table identifying the total distance and total time of vehicles travelling at an average speed interval for all combinations of:

    Identifier for Average Speed Bin (20 levels): Average speeds were binned in 5 mph increments, starting at 2.5mph: 0-2.5mph; 2.5mph-7.5mph; 7.5mph-12.5mph; ... 92.5mph-97.5mph.
    Identifier for Month of the Year (12 levels).
    Identifier for Day of the Week (2 levels): The period for weekday is Monday, 00:00:00 to Friday, 23:59:59, and the period for weekend is Saturday, 00:00:00 to Sunday, 23:59:59. 
    Identifier for Time of Day (24 levels): Times are binned in one hour increments, starting at midnight: 00:00:00 to 00:59:59; 01:00:00 to 01:59:59, ..., 23:00:00 to 23:59:59.
    Identifier for Road Type (4 levels): TomTom used the information in Table 9-29-29-29-2 to classify between the TomTom Functional Classes and the MOVES road type description. TomTom also categorized the road types as rural or urban, according to the census definitions used in MOVES. 
Table 9-2 Correspondence between TomTom Functional Class, Census Information, and MOVES Road Types.
                          MOVES Road Type Description
               Census Information for the TomTom Roadway Segment
                         TomTom Functional Road Class
Rural Restricted Access
Rural
0 and 1
Rural Unrestricted Access
Rural
2 through 7
Urban Restricted Access
Urban
0 and 1
Urban Unrestricted Access
Urban
2 through 7
                                       
TomTom first "snapped" their data points onto road segments. Off-network driving data was not obtained from the TomTom data. Much of the TomTom data that does not "snap to the roadway grid" is caused by loss of satellite signal and errors while the TomTom unit is trying to acquire the satellite signal. Therefore, a difficult analysis would be required to separate real off-network data from GPS error data, and even if the analysis could be done, the reliability of the results would probably be unknown. As such, only data that was associated with the roadway grid was used in the analysis. 

Table 9-39-39-39-3 shows the method for using the internal TomTom data (Columns E through I) to produce the desired output, which ERG used to produce the MOVES2014 tables. The example in the table uses 16 observations that might have been recorded on two urban unrestricted roadway segments (Column E) during TomTom personal navigation device use between 14:00:00 and 14:59:59 on a weekday in April, 2011. Column F is an internal ID (1-5 occur on Segment A, and 11-21 occur on Segment B). Column G gives the length of the segment. Column H gives the time that the device spent on the segment. Column I gives the average speed of the device on the segment. The 16 observations are sorted by the average speed bin, which is given in Column J. The total distance traveled and the total time spent in each combination of road type, month, weekday/weekend, hour of the day, and average speed bin are given in Columns K and L. TomTom provided Columns A, B, C, D, J, K, and L to ERG. The data in those columns was purchased by ERG from TomTom and is provided under license terms that permit free distribution to EPA and the public. The raw data in Columns E, F, G, H, and I were not provided to ERG and the US EPA. 

Table 9-3 Example of Accumulating Total Distance and Total Time for the TomTom Deliverable Table
                                       A
                                       B
                                       C
                                       D
                                       E
                                       F
                                       G
                                       H
                                       I
                                       J
                                       K
                                       L
                             Road Type 
(4 levels)
                              Month 
(12 levels)
                          Weekday/
Weekend
(2 levels)
                         Hour 
of the 
Day
(24 levels)
                                    Segment
                                  Data Point
                            Segment 
Length (feet)
                            Time 
in 
Segment 
(s)
                       Average 
Speed 
in
Segment
(mph)
                              Average 
Speed Bin
                               (mph)
(20 levels)
              Total of Segment Lengths for this Speed Bin (feet)
                Total of Segment Times 
for this Speed Bin (s)
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                              Urban 
Unrestricted
                                     April
                                    Weekday
                             14:00:00 
to
14:59:59
                                       A
                                       5
                                      300
                                      15
                                     13.64
                                      15
                                      550
                                      27
                                       
                                       
                                       
                                       
                                       B
                                      16
                                      250
                                      12
                                     14.20
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       A
                                       1
                                      300
                                      10
                                     20.45
                                      20
                                     1800
                                      60
                                       
                                       
                                       
                                       
                                       B
                                      11
                                      250
                                       8
                                     21.31
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      12
                                      250
                                       9
                                     18.94
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      15
                                      250
                                       8
                                     21.31
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      18
                                      250
                                       8
                                     21.31
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      20
                                      250
                                       9
                                     18.94
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      21
                                      250
                                       8
                                     21.31
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       A
                                       2
                                      300
                                       9
                                     22.73
                                      25
                                     1650
                                      47
                                       
                                       
                                       
                                       
                                       A
                                       3
                                      300
                                       8
                                     25.57
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       A
                                       4
                                      300
                                       9
                                     22.73
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      13
                                      250
                                       7
                                     24.35
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      14
                                      250
                                       7
                                     24.35
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      19
                                      250
                                       7
                                     24.35
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       B
                                      17
                                      250
                                       6
                                     28.41
                                      30
                                      250
                                       6

Using the table delivered by TomTom, ERG calculated the time-based average speed distribution for each road type, day, and hour of the day using the average speed bin (Column J) and the total of segment times (Column L). ERG calculated the average speed distribution according to the 16 speed bins used in MOVES. Figure 9-19-1 plots the average speed distribution for one hour (5 pm) stored in the averageSpeedDistribution table in MOVES, which contains average speed distributions for each hour of the day (24 hours). We are using the TomTom data to represent national default average speed distribution in MOVES. 

          Figure 9-1 Average speed distribution for hour = 17 (5 pm) 
for source types (11 through 54) stored in the AvgSpeedDistribution table in MOVES
                                       
Heavy-Duty Average Speed Distributions
It has been shown that combination trucks travel at approximately 92% of the speed of light-duty vehicles on restricted access roads. Since the TomTom data was developed from light-duty vehicles, the average speed distribution for both short-haul and long-haul combination trucks was adjusted on rural and urban restricted road types.

The average speed for each roadway type, day type, and hour can be calculated by multiplying the average speed of each bin by the corresponding distribution of time as shown in Equation 2917. Here, v is the average speed of the distribution, vi is the average speed of bin i, and ρi is the proportion of time spent in bin i.

                                       
                                  v= vi∙ρi

    =2.5∙ρ1+5∙ρ2+...+ 70∙ρ15+ 75∙ρ16  
                                                                    Equation 17

To adjust the average speed for heavy-duty combination trucks, we redistributed the proportion of time spent in each speed bin such that its contribution to the average speed was 92% of the light-duty speed, as shown in Equation 18. This redistributed proportion of time in each speed bin is given by ρi'.

                                       
                                       
                                       
                         vcombination=.92 vlight-duty
                                        =vi∙ρi'
                                                                    Equation 18

To perform this redistribution, we defined two new variables, α and β, where αi is the fraction of ρi that is shifted down one speed bin, and βi is the fraction of ρi shifted down two speed bins. The new distribution at speed bin i (given by ρi') starts with the original distribution (ρi), gains the proportions moved down from the higher speed bins (αi+1∙ρi+1 and βi+2∙ρi+2), and loses the proportion that is moved to a lower speed bin (αi∙ρi and βi∙ρi). This is shown in Equation 3119:
                                       
           ρi'=ρi+αi+1∙ρi+1+βi+2∙ρi+2-αi∙ρi-βi∙ρi
                                                                    Equation 19
For speed bins with an average speed of less than or equal to 60 mph, we only needed to shift distributions using a fraction of one speed bin (or 5 mph). Thus we only calculated αi and set βi=0. Mathematically, reducing a bin's average speed by a certain fraction (η) can be expressed with Equation 20: 
                                       
                        1-η∙vi=αi∙vi-5+1-αi∙vi
                                                                    Equation 20
Essentially, the fraction that is moved to the next slower bin (αi) is multiplied by the slower speed (note that each of the speed bins are 5 mph apart, so this is vi-5), and the fraction that remains (1-αi) is multiplied by the original speed vi. Since the average speed of the combination trucks is 92% slower, 1-η=92% and η=0.08.

By rearranging terms from equation 20, and solving for αi we obtain:
                                       
                                 αi=vi∙η5
                                                                    Equation 21
However, for speed bins >=65 mph, Equation 21 yields αi greater than 1. Since that logically can't happen, some of the distribution needed to be moved to the second next slower speed bin to fully account for the 8% speed reduction. This is mathematically shown in Equation 22, which is the logical extension of Equation 20: 

                1-η∙vi=βi∙vi-10+αi∙vi-5+1-αi-βi∙vi
                                                                    Equation 22
The difference between Equation 20 and Equation 22 is that an additional fraction (βi) is removed from the original speed bin and is given the speed of two speed bins slower (or 10 mph slower). With this additional factor, there is an infinite combination of solutions that could satisfy Equation 22. We solved this problem with a linear equation solver by setting  Equation 22 to a constraint (see Equation 23), adding the constraint that αi+βi are less than or equal to 1 (Equation 24), and choosing the solution that minimized βi.
                                       
                   αi∙vi-5+βi∙vi-10+vi∙η-αi-βi=0
                                  Equation 23
                                       
                                  αi+βi<=1
                                  Equation 24
This linear program was used to solve for αi and βi for each speed bin between 65 and 75 mph. With αi and βi known for each bin, the new distributions ρi' were calculated.

Figure 9-2 An illustration of adjustments made to the average speed bin 55 mph. Here, the original speed distribution is shown in light gray. The darker gray is the proportion of speed bin 55 that is moved out to the slower speed bin 50 mph, and the black areas are the distributions from speed bin 60 and 65 that are moved in to speed bin 55 mph.
                                       
An additional adjustment was made for the highest speed bins because we assumed that the maximum speed bin had a triangular distribution with an average speed of 75 mph (see Figure 9-29-2). In the new distribution, all of the maximum speed bin fraction was redistributed to the 65 and 70 mph bins. Therefore, the new maximum speed bin (70 mph) was also assumed to have a triangular distribution. Geometrically, 1/9[th] of a triangular distribution averaging 70 mph is faster than 72.5 mph. Since the 75 mph speed bin is defined as any speed >=72.5 mph, 1/9[th] of the new 70 mph fraction (ρ15') was reclassified as the new fraction for the 75 mph bin.

This process was repeated for both short- and long-haul combination trucks on restricted-access road types for every hour and day type combination. See Figure 9-3 for an example illustration of the results of this analysis.

      Figure 9-3 Average weekday speed distribution for hour = 17 (5 pm) 
       by source type stored in the avgSpeedDistribution table in MOVES.
                                       

Driving Schedules and Ramps
Drive schedule refers to a second-by-second vehicle speed trajectory. A drive schedule typically includes all vehicle operation from the time the engine starts until the engine is keyed off, both driving (travel) and idling time. Drive schedules are used in MOVES to determine the operating mode distribution for most MOVES running processes for calculation of emissions and energy consumption. 

In brief, there is an emission rate (in grams per hour of vehicle operation) for each operating mode of vehicle operation.  Each second of vehicle operation is assigned to an operating mode as a function of vehicle velocity in each second and the specific power (VSP), or scaled tractive power (STP) for heavy-duty vehicles, is calculated from the driving schedules. The average speed distribution is used to weight the operating mode distributions determined from driving schedules with different average speeds into a composite operating mode distribution that represents overall travel by vehicles. The distribution of operating modes is used by MOVES to weight the emission rates to account for the vehicle operation.

Driving Schedules
A key feature of MOVES is the capability to accommodate a number of drive schedules to represent driving patterns across source type, roadway type and average speed. For the national default case, MOVES2014 employs 49 drive schedules with various average speeds, mapped to specific source types and roadway types. 

MOVES stores all of the drive schedule information in four database tables. DriveSchedule provides the drive schedule name, identification number, and the average speed of the drive schedule. DriveScheduleSecond contains the second-by-second vehicle trajectories for each schedule. In some cases the vehicle trajectories are not contiguous; as detailed below, they may be formed from several unconnected microtrips that overall represent driving behavior.  DriveScheduleAssoc defines the set of schedules which are available for each combination of source use type and road type. Ramps use operating mode distributions directly and do not use drive schedules to calculate operating modes.  The RoadOpModeDistribution table lists operating mode distributions used for ramps for each source use type, road type and speed bin.

The tables below list the driving schedules used in MOVES2014.   Some driving schedules are used for both restricted access (freeway) and unrestricted access (non-freeway) driving.  In most cases, these represent atypical conditions, such as extreme congestion or unrealistic free flow speeds.  In these conditions, we assume that the road type itself has little impact on the expected driving behavior (driving schedule).  Normally, these conditions represent only a small portion of overall driving.  Similarly, some driving schedules are used for multiple source types where vehicle specific information was not available.

In the past, if there was no appropriate driving schedule to use for modeling an average speed bin, MOVES would use the nearest schedule.  MOVES2014 now requires driving schedules that can be used as the upper bound and the lower bound for all average speed bins.  New default driving schedules have been added to assure that all average speed bins have appropriate driving schedules for all the MOVES average speed bins. 

Table 10-1 Driving Cycles for Motorcycles, Cars, Passenger Cars and Light Commercial Trucks (11,21,31,32)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted Access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      101
LD Low Speed 1
                                      2.5
                                       X
                                       X
                                       X
                                       X
                                     1033
Final FC14LOSF
                                      8.7
                                       
                                       
                                       X
                                       X
                                     1043
Final FC19LOSAC
                                     15.7
                                       
                                       
                                       X
                                       X
                                     1041
Final FC17LOSD
                                     18.6
                                       X
                                       X
                                       
                                       
                                     1021
Final FC11LOSF
                                     20.6
                                       
                                       
                                       X
                                       X
                                     1030
Final FC14LOSC
                                     25.4
                                       X
                                       X
                                       
                                       
                                      153
LD LOS E Freeway
                                     30.5
                                       
                                       
                                       X
                                       X
                                     1029
Final FC14LOSB
                                     31.0
                                       X
                                       X
                                       
                                       
                                     1026
Final FC12LOSE
                                     43.3
                                       
                                       X
                                       
                                       
                                     1020
Final FC11LOSE
                                     46.1
                                       
                                       
                                       X
                                       X
                                     1011
Final FC02LOSDF
                                     49.1
                                       X
                                       
                                       
                                       
                                     1025
Final FC12LOSD
                                     52.8
                                       
                                       X
                                       
                                       
                                     1019
Final FC11LOSD
                                     58.8
                                       
                                       
                                       X
                                       X
                                     1024
Final FC12LOSC
                                     63.7
                                       X
                                       X
                                       
                                       
                                     1018
Final FC11LOSC
                                     64.4
                                       
                                       
                                       X
                                       X
                                     1017
Final FC11LOSB
                                     66.4
                                       
                                       
                                       X
                                       X
                                     1009
Final FC01LOSAF
                                     73.8
                                       X
                                       X
                                       X
                                       X
                                      158
LD High Speed Freeway 3
                                     76.0
                                       X
                                       X
                                       X
                                       X

              Table 10-2 Driving Cycles for Intercity Buses (41)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      398
CRC E55 HHDDT Creep
                                      1.8
                                       X
                                       X
                                       X
                                       X
                                      404
New York City Bus
                                      3.7
                                       X
                                       X
                                       
                                       
                                      201
MD 5mph Non-Freeway
                                      4.6
                                       X
                                       X
                                       X
                                       X
                                      405
WMATA Transit Bus
                                      8.3
                                       X
                                       X
                                       
                                       
                                      202
MD 10mph Non-Freeway
                                     10.7
                                       X
                                       X
                                       X
                                       X
                                      203
MD 15mph Non-Freeway
                                     15.6
                                       X
                                       X
                                       X
                                       X
                                      204
MD 20mph Non-Freeway
                                     20.8
                                       X
                                       X
                                       X
                                       X
                                      205
MD 25mph Non-Freeway
                                     24.5
                                       X
                                       X
                                       X
                                       X
                                      206
MD 30mph Non-Freeway
                                     31.5
                                       X
                                       X
                                       X
                                       X
                                      251
MD 30mph Freeway
                                     34.4
                                       X
                                       X
                                       X
                                       X
                                      252
MD 40mph Freeway
                                     44.5
                                       X
                                       X
                                       X
                                       X
                                      253
MD 50mph Freeway
                                     55.4
                                       X
                                       X
                                       X
                                       X
                                      254
MD 60mph Freeway
                                     60.4
                                       X
                                       X
                                       X
                                       X
                                      255
MD High Speed Freeway
                                     72.8
                                       X
                                       X
                                       X
                                       X
                                      397
MD High Speed Freeway Plus 5 mph
                                     77.8
                                       X
                                       X
                                       X
                                       X

        Table 10-3 Driving Cycles for Transit and School Buses (42,43)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      398
CRC E55 HHDDT Creep
                                      1.8
                                       X
                                       X
                                       X
                                       X
                                      201
MD 5mph Non-Freeway
                                      4.6
                                       
                                       
                                       X
                                       X
                                      404
New York City Bus
                                      3.7
                                       X
                                       X
                                       
                                       
                                      202
MD 10mph Non-Freeway
                                     10.7
                                       
                                       
                                       X
                                       X
                                      405
WMATA Transit Bus
                                      8.3
                                       X
                                       X
                                       
                                       
                                      401
Bus Low Speed Urban*
                                      15
                                       X
                                       X
                                       
                                       
                                      203
MD 15mph Non-Freeway
                                     15.6
                                       
                                       
                                       X
                                       X
                                      204
MD 20mph Non-Freeway
                                     20.8
                                       
                                       
                                       X
                                       X
                                      205
MD 25mph Non-Freeway
                                     24.5
                                       
                                       
                                       X
                                       X
                                      402
Bus 30 mph Flow*
                                      30
                                       X
                                       X
                                       
                                       
                                      206
MD 30mph Non-Freeway
                                     31.5
                                       
                                       
                                       X
                                       X
                                      251
MD 30mph Freeway
                                     34.4
                                       
                                       
                                       X
                                       X
                                      252
MD 40mph Freeway
                                     44.5
                                       
                                       
                                       X
                                       X
                                      403
Bus 45 mph Flow*
                                      45
                                       X
                                       X
                                       
                                       
                                      253
MD 50mph Freeway
                                     55.4
                                       X
                                       X
                                       X
                                       X
                                      254
MD 60mph Freeway
                                     60.4
                                       X
                                       X
                                       X
                                       X
                                      255
MD High Speed Freeway
                                     72.8
                                       X
                                       X
                                       X
                                       X
                                      397
MD High Speed Freeway Plus 5 mph
                                     77.8
                                       X
                                       X
                                       X
                                       X
	* To be consistent with the speed distributions described in Section 9, this speed represents the average for the traffic the bus is traveling in, not the average speed of the bus, which is lower due to stops.

               Table 10-4 Driving Cycles for Refuse Trucks (51)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      398
CRC E55 HHDDT Creep
                                      1.8
                                       
                                       
                                       X
                                       X
                                      501
Refuse Truck Urban
                                      2.2
                                       X
                                       X
                                       
                                       
                                      301
HD 5mph Non-Freeway
                                      5.8
                                       
                                       
                                       X
                                       X
                                      302
HD 10mph Non-Freeway
                                     11.2
                                       X
                                       X
                                       X
                                       X
                                      303
HD 15mph Non-Freeway
                                     15.6
                                       X
                                       X
                                       X
                                       X
                                      304
HD 20mph Non-Freeway
                                     19.4
                                       X
                                       X
                                       X
                                       X
                                      305
HD 25mph Non-Freeway
                                     25.6
                                       X
                                       X
                                       X
                                       X
                                      306
HD 30mph Non-Freeway
                                     32.5
                                       X
                                       X
                                       X
                                       X
                                      351
HD 30mph Freeway
                                     34.3
                                       X
                                       X
                                       X
                                       X
                                      352
HD 40mph Freeway
                                     47.1
                                       X
                                       X
                                       X
                                       X
                                      353
HD 50mph Freeway
                                     54.2
                                       X
                                       X
                                       X
                                       X
                                      354
HD 60mph Freeway
                                     59.4
                                       X
                                       X
                                       X
                                       X
                                      355
HD High Speed Freeway
                                     71.7
                                       X
                                       X
                                       X
                                       X
                                      396
HD High Speed Freeway Plus 5 mph
                                     77.8
                                       X
                                       X
                                       X
                                       X

  Table 10-5 Driving Cycles for Single Unit Trucks and Motor Homes (52,53,54)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      398
CRC E55 HHDDT Creep
                                      1.8
                                       X
                                       X
                                       X
                                       X
                                      201
MD 5mph Non-Freeway
                                      4.6
                                       X
                                       X
                                       X
                                       X
                                      202
MD 10mph Non-Freeway
                                     10.7
                                       X
                                       X
                                       X
                                       X
                                      203
MD 15mph Non-Freeway
                                     15.6
                                       X
                                       X
                                       X
                                       X
                                      204
MD 20mph Non-Freeway
                                     20.8
                                       X
                                       X
                                       X
                                       X
                                      205
MD 25mph Non-Freeway
                                     24.5
                                       X
                                       X
                                       X
                                       X
                                      206
MD 30mph Non-Freeway
                                     31.5
                                       X
                                       X
                                       X
                                       X
                                      251
MD 30mph Freeway
                                     34.4
                                       X
                                       X
                                       X
                                       X
                                      252
MD 40mph Freeway
                                     44.5
                                       X
                                       X
                                       X
                                       X
                                      253
MD 50mph Freeway
                                     55.4
                                       X
                                       X
                                       X
                                       X
                                      254
MD 60mph Freeway
                                     60.4
                                       X
                                       X
                                       X
                                       X
                                      255
MD High Speed Freeway
                                     72.8
                                       X
                                       X
                                       X
                                       X
                                      397
MD High Speed Freeway Plus 5 mph
                                     77.8
                                       X
                                       X
                                       X
                                       X

           Table 10-6 Driving Cycles for Combination Trucks (61,62)
                                      ID
                                  Cycle Name
                                 Average Speed
                              Unrestricted access
                               Restricted access
                                       
                                       
                                       
                                     Rural
                                     Urban
                                     Rural
                                     Urban
                                      398
CRC E55 HHDDT Creep
                                      1.8
                                       X
                                       X
                                       X
                                       X
                                      301
HD 5mph Non-Freeway
                                      5.8
                                       X
                                       X
                                       X
                                       X
                                      302
HD 10mph Non-Freeway
                                     11.2
                                       X
                                       X
                                       X
                                       X
                                      303
HD 15mph Non-Freeway
                                     15.6
                                       X
                                       X
                                       X
                                       X
                                      304
HD 20mph Non-Freeway
                                     19.4
                                       X
                                       X
                                       X
                                       X
                                      305
HD 25mph Non-Freeway
                                     25.6
                                       X
                                       X
                                       X
                                       X
                                      306
HD 30mph Non-Freeway
                                     32.5
                                       X
                                       X
                                       X
                                       X
                                      351
HD 30mph Freeway
                                     34.3
                                       X
                                       X
                                       X
                                       X
                                      352
HD 40mph Freeway
                                     47.1
                                       X
                                       X
                                       X
                                       X
                                      353
HD 50mph Freeway
                                     54.2
                                       X
                                       X
                                       X
                                       X
                                      354
HD 60mph Freeway
                                     59.4
                                       X
                                       X
                                       X
                                       X
                                      355
HD High Speed Freeway
                                     71.7
                                       X
                                       X
                                       X
                                       X
                                      396
HD High Speed Freeway Plus 5 mph
                                     77.8
                                       X
                                       X
                                       X
                                       X

The default drive schedules for light-duty vehicles listed in the tables above were developed from several sources. "LD LOS E Freeway" and "HD High Speed Freeway" were retained from MOBILE6 and are documented in report M6.SPD.001.   "LD Low Speed 1" is a historic cycle used in the development of speed corrections for MOBILE5 and is meant to represent extreme stop-and-go "creep" driving. "LD High Speed Freeway 3" was developed for MOVES to represent very high speed restricted access driving.  It is a 580-second segment of restricted access driving from an in-use vehicle instrumented as part of EPA's On-Board Emission Measurement "Shootout" program, with an average speed of 76 mph and a maximum speed of 90 mph.  Fifteen new light-duty "Final" cycles were developed by a contractor for MOVES based on urban and rural data collected in California in 2000 and 2004.[37] The new cycles were selected to best cover the range of road types and average speeds modeled in MOVES.

Most of the driving schedules used for buses are borrowed directly from driving schedules used for single unit trucks (described below).  The "New York City Bus" and "WMATA Transit Bus" drive schedules are included for urban driving that includes transit type bus driving behavior.  The "CRC E55 HHDDT Creep"  cycle was included to cover extremely low speeds.  The "Bus 30 mph Flow" and "Bus 45 mph Flow" cycles used for transit and school buses were developed by EPA based on Ann Arbor Transit Authority buses instrumented in Ann Arbor, Michigan.  The bus "flow" cycles were developed using selected non-contiguous snippets of driving from one stop to the next stop, including idle, to create cycles with the desired average driving speeds.  The bus "flow" cycles have a nominal speed used for selecting the driving cycles that does not include the idle time and only considers the free-flow speed between stops. The actual average speed of the cycle (including stops) are shown in Section 20 (Appendix D). Note that the "Bus Low Speed Urban" bus cycle is the last 450 seconds of the standard New York City Bus cycle. 

The "Refuse Truck Urban" cycle represents refuse truck driving with many stops and a maximum speed of 20 mph, but an average speed of 2.2 mph.  This cycle was developed by West Virginia University for the State of New York.  The CRC EFF HHDDT Creep cycle was used instead for restricted access driving of refuse trucks at extremely low speeds.  All of the other driving cycles used for refuse trucks were borrowed from driving cycles developed for heavy-duty combination trucks, described below.

Single unit and combination trucks use driving cycles developed specifically for MOVES, based on work performed for EPA by Eastern Research Group (ERG), Inc. and documented in the report "Roadway-Specific Driving Schedules for Heavy-Duty Vehicles." ERG analyzed data from 150 medium and heavy-duty vehicles instrumented to gather instantaneous speed and GPS measurements. ERG segregated the driving into restricted access and unrestricted access driving for medium and heavy-duty vehicles, and then further stratified vehicles trips according the pre-defined ranges of average speed covering the range of vehicle operation.  The medium duty cycles are used with single unit trucks and heavy-duty cycles are used with combination trucks.

The schedules developed by ERG are not contiguous schedules which could be run on a chassis dynamometer, but are made up of non-contiguous "snippets" of driving (microtrips) meant to represent target distributions.  For use with MOVES, we modified the schedules' time field in order to signify when one microtrip ended and one began. The time field of the driving schedule table increments two seconds (instead of one) when each new microtrip begins. This two-second increment signifies that MOVES should not regard the microtrips as contiguous operation when calculating accelerations. 

Both single unit and combination trucks use the CRC EFF HHDDT Creep cycle for all driving at extremely low speeds.  At the other end of the distribution, none of the existing driving cycles for heavy-duty trucks included average speeds sufficiently high to cover the highest speed bin used by MOVES.  To construct such cycles, EPA started with the highest speed driving cycle available from the ERG analysis and added 5 mph to each point, effectively increasing the average speed of the driving cycle without increasing the acceleration rate at any point.  We have checked the feasibility of these new driving cycles (396 and 397) using simulations with the EPA's Greenhouse Gas Emissions Model (GEM) for medium- and heavy-duty vehicle compliance. GEM is a forward-looking full vehicle simulation tool that calculates fuel economy and GHG emissions from an input drive trace and series of vehicle parameters.  One of the aspects of forward-looking models is that the driver model is designed to demand torque until the vehicle drive trace is met.  Our results indicate that the simulated vehicles were able to follow the speed demands of the proposed driving cycles without exceeding maximum torque or power.

None of the driving schedules used to represent restricted access (freeway) driving contain vehicle operation on entrance or exit ramps.  The effect of ramp operation is added separately in MOVES.

Ramp Activity
Ramp activity is the driving behavior of vehicles that occurs on entrance and exit ramps as vehicles enter or leave restricted access roads.  It includes all of the activity between operation on the unrestricted road and operation on the restricted road.

None of the driving schedules used to represent restricted access (freeway) driving contain vehicle operation on entrance or exit ramps.  The effect of ramp operation is calculated separately.  Instead of using driving schedules to generate operating mode distributions for ramps, each average speed bin has an associated operating mode distribution that reflects the power demand expected from ramp operation associated with each nominal average speed for each of the source types.  The operating mode distributions used for ramps in MOVES2014 were estimated to represent the driving connecting to and from a freeway with the given average speed. These operating mode distributions (i.e. the fractions of time spent in each of the operating modes for each source type on each road type at each average speed) can be found in the in the default MOVES2014 database (RoadOpModeDistribution table).

Each set of ramp operating modes is associated with a corresponding average speed that does not include ramp operation.  Since  operating modes for ramp emissions are  affected by the distribution of the average speed bins on the surrounding roads, the determination of average speeds for restricted access roads (both urban and rural) should not include the time or distance of vehicles on ramps. However, the VMT on ramps should be included with restricted access VMT.

The emission impact of ramp activity is combined with the other driving activity found in the restricted access (freeway) driving cycles using a ramp fraction.  This fraction defines the fraction of all time spent on a road that occurs on entrance and exit ramps. The fraction used (8%) in MOVES2014 is derived from the ramp fraction value developed originally for the MOBILE6 model. 

Hotelling Activity
MOVES2014 defines "hotelling" as any long period of time that drivers spend at their vehicles during mandated down times during long distance deliveries by tractor/trailer combination heavy-duty trucks.  During the mandatory down time, drivers can stay in motels or other accommodations, but most of these trucks have sleeping spaces built into the cab of the truck and drivers stay with their vehicles. Hotelling hours are included in MOVES2014 in order to account for use of the truck engine (referred to as "extended idling") to power air conditioning, heat and other accessories and account for the use of auxiliary power units (APU), which are small on-board power generators.

In MOVES2014, only the long haul combination truck source use type (sourceTypeID=62) is assumed to have any hotelling activity.  All of the long haul combination trucks are diesel fueled.  All source use types other than long haul combination trucks have hotelling activity fractions set to zero.

National Default Hotelling Rate
Federal law limits long haul truck drivers to 10 hours driving followed by a mandatory 8 hour rest period. These regulations are described in the Federal Register.   In long-haul operation, drivers will stop periodically along their routes.  For MOVES, the total hours of hotelling are estimated by using the national estimate of VMT by long haul combination trucks divided an estimated average speed to calculate total hours of driving.  The total hours of driving divided by 10 gives the number of 8-hour rest periods needed and thus the national total hotelling hours.  

A method is needed to allocate these total hotelling hours to locations.  For MOVES2014, we decided to determine a "hotelling rate" (hours of hotelling per mile of travel) that could be used, in combination with VMT information to allocate the hotelling hours. We calculate a hotelling rate as the national total hours of hotelling divided by the national total miles driven by long haul trucks on rural restricted access (freeways) roads.  Driving time on all roads contributes to the total hotelling hours calculation.  However, most locations used for hotelling are located near the roadways (restricted access) most travelled by long haul trucks. In order to prevent large amounts of hotelling to be allocated to congested urban areas, we decided to only use the VMT on rural restricted roads as the surrogate for allocating the total hotelling hours.

The hotelling rate (hotelling hours per mile of rural restricted access travel by long haul combination trucks) is applied to the estimate of rural restricted access VMT by long haul combination trucks to estimate the default hotelling hours for any location, month or day.  The allocation of Hotelling to specific hours of the day is described below in Section 12.5.  

The MOVES2014 default hotelling rate was calculated using default national total VMT estimates for calendar year 2011 shown in Table 11-1.

                                       
             Total Hours=Total Vehicle Miles TraveledAverage Speed
                                  Equation 25

                                       
                   Total Trips=Total Hours10 hours per trip
                                  Equation 26

                                       
                 Hotelling Hours=Total Trips*8 hours per trip
                                  Equation 27

                                       
      Hotelling Rate=Hotelling HoursTotal Rural Restricted Miles Traveled
                                  Equation 28

Where:		
         * Total Hours is the calculated time long haul combination trucks spend driving.
         * Total Vehicle Miles Traveled is the total miles traveled by diesel long haul combination trucks in the nation in calendar year 2011 on all road types taken from MOVES defaults.
         * Average Speed is an estimate of the average speed (distance divided by time) for diesel long haul combination trucks on all road types while operating.
         * Total Trips is the calculated number of trips by long haul combination trucks.
         * Hotelling Hours is the calculated amount of rest time for long haul combination trucks.
         * Rural Restricted Miles is the total miles traveled by diesel long haul combination trucks on only rural restricted access roads (freeways) in calendar year 2011 using MOVES defaults.

Table 11-1 Calculation of Hotelling Hours from Long Haul Combination Truck VMT
                                  Description
                                 Annual Value
                                     units
Rural Restricted
                                                                    31392300000
miles
Rural Unrestricted
                                                                    34301700000
miles
Urban Restricted
                                                                    32243100000
miles
Urban Unrestricted
                                                                    28848900000
miles
Total annual VMT
                                                                   126786000000
miles
Hours (58.3 mph)
                                                                     2174716981
hours
Trips (10 hrs per trip)
                                                                      217471698
trips
Hotelling hours (8 hrs per trip)
                                                                     1739773585
hours
Hotelling hours per mile for rural restricted roads
                                                                       0.055414
rate

For the MOVES default, all hotelling activity is assumed to occur in counties with travel on rural restricted access roads), and thus will occur primarily in rural areas of states.

The national rate of hotelling hours per mile of rural restricted access roadway VMT is stored in the HotellingCalendarYear table for each calendar year.  The same value calculated for 2011 is used as the default for all calendar years.  The County Data Manager includes the HotellingActivityDistribution table which provides the opportunity for states to provide their own estimates of hotelling hours specific to their location and time. Whenever possible states and local areas should obtain and use more accurate local estimates of hotelling hours when modeling local areas.
Hotelling Activity Distribution
Hotelling differs from simple parking. In MOVES, hotelling hours are divided into operating modes which define the emissions associated with the type of hotelling activity. Long haul trucks are often equipped with sleeping berths and other amenities to make the drive rest periods more comfortable.  These amenities require power for operation.  This power can be obtained by running the main truck engine (extended idle) or by use of smaller on-board power generators (auxiliary power units, APU).  Some truck stop locations include power hookups (truck stop electrification) to allow use of amenities without running either the truck engines or APUs.  Some of rest time may occur without use of amenities at all.  Table 11-211-211-211-2 shows the hotelling operating modes used in MOVES.
                                       
                 Table 11-2 Hotelling Activity Operating Modes
                                   OpModeID
                                  Description
                                      200
                        Extended Idling of Main Engine
                                      201
                  Hotelling Diesel Auxiliary Power Unit (APU)
                                      203
                       Hotelling Battery or AC (plug in)
                                      204
                   Hotelling All Engines and Accessories Off
 
The HotellingActivityDistribution table contains the MOVES default values for the distribution of hotelling activity to the operating modes.

              Table 11-3 Default Hotelling Activity Distributions
                               beginModelYearID
                                endModelYearID
                                   opModeID
                                opModeFraction
                                     1960
                                     2009
                                      200
                                       1
                                     1960
                                     2009
                                      201
                                       0
                                     1960
                                     2009
                                      203
                                       0
                                     1960
                                     2009
                                      204
                                       0
                                     2010
                                     2050
                                      200
                                      0.7
                                     2010
                                     2050
                                      201
                                      0.3
                                     2010
                                     2050
                                      203
                                       0
                                     2010
                                     2050
                                      204
                                       0

All of the hotelling hours for long haul trucks of model years before 2010 are assumed to use extended idle to power accessories.  Starting with the 2010 model year, the trucks are assumed to use extended idle 70 percent of the time and use APUs 30% of the time based on EPA's assessment of technologies used by tractor manufacturers to comply with the Heavy-Duty Greenhouse Gas standards.

Temporal Distributions
MOVES is designed to estimate emissions for every hour of every day type in every month of the year. The vehicle miles traveled (VMT) are provided for MOVES2014 in terms of annual miles.  These miles are allocated to months, days and hours using allocation factors (distributions), either default values or values provided by users.

Default values for most temporal VMT allocations are derived from a 1996 report from the Office of Highway Information Management (OHIM).   The report describes analysis of a sample of 5,000 continuous traffic counters distributed through the United States. EPA obtained the data used in the report and used it to generate the VMT temporal distribution inputs in the form needed for MOVES2014.

The OHIM report does not specify VMT by vehicle type, so MOVES uses the same values for all source types, except motorcycles, as described below. In MOVES, daily truck hotelling hours are calculated as proportional to source hours operating (SHO) calculated by MOVES from the VMT and speed distributions for long haul combination trucks. However, the hours of hotelling activity in each hour of the day are not proportional to VMT, as described in Section 12.5. 

The temporal distribution for engine start and corresponding engine soak (parked) distributions are calculated from vehicle activity data stored in the SampleVehicle and SampleVehicleTrip tables of the MOVES database.  These tables contain a set of vehicle trip activity information from over 37,000 trips, taken from a sample of vehicles intended to be representative of activity for each source type.  Evaporative emissions are also affected by the time of day and the duration of parking. Some of the vehicles in the samples take no trips.

               Table 12-1 Sample Vehicle Day Table Sample Sizes
                                  Source Type
                                Vehicle Sample
                                                                   sourceTypeID
Description
Weekday (dayID=5)
Weekend (dayID=2)
                                                                             11
 Motorcycle
                                                                           2214
                                                                            983
                                                                             21
 Passenger Car
                                                                            821
                                                                            347
                                                                             31
 Passenger Truck
                                                                            834
                                                                            371
                                                                             32
 Light Commercial Truck
                                                                            773
                                                                            345
                                                                             41
 Intercity Bus
                                                                            190
                                                                             73
                                                                             42
 Transit Bus
                                                                            110
                                                                             14
                                                                             43
 School Bus
                                                                            136
                                                                             59
                                                                             51
 Refuse Truck
                                                                            205
                                                                             65
                                                                             52
 Single Unit Short-haul Truck
                                                                            112
                                                                             58
                                                                             53
 Single Unit Long-haul Truck
                                                                            123
                                                                             50
                                                                             54
 Motor Home
                                                                           5431
                                                                           2170
                                                                             61
 Combination Short-haul Truck
                                                                            130
                                                                             52
                                                                             62
 Combination Long-haul Truck
                                                                            122
                                                                             49

 VMT Distribution by Month of the Year
In MOVES, VMT is entered as an annual value and allocated to month using the MonthVMTFraction table. For MOVES, we use the data from the OHIM report, Figure 2.2.1 "Travel by Month, 1970-1995," but modified to fit MOVES specifications.  The table shows VMT/day taken from the OHIM report, normalized to one for January. For MOVES, we need the fraction of total annual VMT in each month. The report values of VMT per day were used to calculate the VMT in a month using the number of days in each month.  The calculations assume a non-leap year (365 days).

                          Table 12-2 MonthVMTFraction
                                     Month
                              Normalized VMT/day
                                     MOVES
                                 Distribution
January
                                    1.0000
                                    0.0731
February
                                    1.0560
                                    0.0697
March
                                    1.1183
                                    0.0817
April
                                    1.1636
                                    0.0823
May
                                    1.1973
                                    0.0875
June
                                    1.2480
                                    0.0883
July
                                    1.2632
                                    0.0923
August
                                    1.2784
                                    0.0934
September
                                    1.1973
                                    0.0847
October
                                    1.1838
                                    0.0865
November
                                    1.1343
                                    0.0802
December
                                    1.0975
                                    0.0802
                                      Sum
                                       
                                    1.0000

FHWA does not report monthly VMT information by vehicle classification.  But it is clear that in many regions of the United States, motorcycles are driven much less frequently in the winter months. For MOVES2014 an allocation for motorcycles was derived using monthly national counts of fatal motorcycle crashes from the National Highway Traffic Safety Administration Fatality Analysis System for 2010. This allocation increases motorcycle activity (and emissions) in the summer months and decreases them in the winter compared to the other source types.  These default values for motorcycles are only a national average and do not reflect the strong regional differences that would be expected due to climate.

                  Table 12-3 MonthVMTFraction for Motorcycles
                                     Month
                                   Month ID
                                 Distribution
January
                                       1
                                    0.0262
February
                                       2
                                    0.0237
March
                                       3
                                    0.0583
April
                                       4
                                    0.1007
May
                                       5
                                    0.1194
June
                                       6
                                    0.1269
July
                                       7
                                    0.1333
August
                                       8
                                    0.1349
September
                                       9
                                    0.1132
October
                                      10
                                    0.0950
November
                                      11
                                    0.0442
December
                                      12
                                    0.0242
                                      Sum
                                       
                                    1.0000

 VMT Distribution by Type of Day
The DayVMTFraction distribution divides the weekly VMT into two day types.  The OHIM report provides VMT percentage values for each day and hour of a typical week for urban and rural roadway types for various regions of the United States. Since the day  - of-the-week data obtained from the OHIM report is not disaggregated by month or source type, the same values were used for every month and source type. MOVES uses the 1995 data displayed in Figure 2.3.2 of the OHIM report.

The DayVMTFraction needed for MOVES has only two categories; week days (Monday, Tuesday, Wednesday, Thursday and Friday) and weekend (Saturday and Sunday) days.  The OHIM reported percentages for each day of the week were summed in their respective categories and converted to fractions. The OHIM report explains that data for "3am" refers to data collected from 3am to 4am. Thus data labeled "midnight" belongs to and was summed with the upcoming day. 

                          Table 12-4 DayVMTFractions
                                   Fraction
                                     Rural
                                     Urban
                                    Weekday
                                    0.72118
                                    0762365
                                    Weekend
                                    0.27882
                                   0.237635
                                      Sum
                                    1.00000
                                   1.000000

We assigned the "Rural" fractions to the rural road types and the "Urban" fractions to the urban road types. The fraction of weekly VMT reported for a single weekday in MOVES will be one-fifth of the weekday fraction and the fraction of weekly VMT for a single weekend day will be one-half the weekend fraction.
 
 VMT Distribution by Hour of the Day
HourVMTFraction uses the same data as for DayVMTFraction. We converted the OHIM report's VMT data by hour of the day in each day type to percent of day by dividing by the total VMT for each day type, as described for the DayVMTFraction.  The OHIM report explains that data for "3am" refers to data collected from 3am to 4am. Thus data labeled "midnight" belongs to and was included with the upcoming day.

There are separate sets of HourVMTFractions for "urban" and "rural" road types, but unrestricted and unrestricted roads use the same HourVMTFraction distributions. All source types use the same HourVMTFraction distributions. 

               Table 12-5 Distribution of VMT by Hour of the Day
                                    hourID
                                  Description
                                     Urban
                                     Rural
                                       
                                       
                                    Weekday
                                    Weekend
                                    Weekday
                                    Weekend
                                       1
Hour beginning at 12:00 midnight
                                   0.0098621
                                   0.0214739
                                   0.0107741
                                   0.0164213
                                       2
Hour beginning at 1:00 AM
                                  0.00627248
                                   0.0144428
                                   0.0076437
                                   0.0111921
                                       3
Hour beginning at 2:00 AM
                                  0.00505767
                                   0.0109684
                                   0.0065464
                                   0.0085415
                                       4
Hour beginning at 3:00 AM
                                  0.00466686
                                   0.0074945
                                   0.0066348
                                  0.00679328
                                       5
Hour beginning at 4:00 AM
                                  0.00699469
                                   0.0068385
                                   0.0095399
                                  0.00721894
                                       6
Hour beginning at 5:00 AM
                                   0.018494
                                   0.0103588
                                   0.0200551
                                   0.0107619
                                       7
Hour beginning at 6:00 AM
                                   0.0459565
                                   0.0184303
                                   0.0410295
                                  0.01768008
                                       8
Hour beginning at 7:00 AM
                                   0.0696444
                                   0.0268117
                                   0.0579722
                                   0.0268751
                                       9
Hour beginning at 8:00 AM
                                   0.0608279
                                   0.0363852
                                   0.0534711
                                   0.0386587
                                      10
Hour beginning at 9:00 AM
                                   0.0502862
                                   0.0475407
                                   0.0525478
                                   0.0522389
                                      11
Hour beginning at 10:00 AM
                                   0.0499351
                                   0.0574664
                                   0.0550607
                                   0.0631739
                                      12
Hour beginning at 11:00 AM
                                   0.0543654
                                   0.0650786
                                   0.0576741
                                   0.0699435
                                      13
Hour beginning at 12:00 Noon
                                   0.0576462
                                   0.0713228
                                   0.0591429
                                   0.0729332
                                      14
Hour beginning at 1:00 PM
                                   0.0580319
                                   0.0714917
                                   0.0608019
                                   0.0731218
                                      15
Hour beginning at 2:00 PM
                                   0.0622554
                                   0.0717226
                                   0.0652985
                                   0.0736159
                                      16
Hour beginning at 3:00 PM
                                   0.0710049
                                   0.0720061
                                   0.0726082
                                   0.0744608
                                      17
Hour beginning at 4:00 PM
                                   0.0769725
                                   0.0711487
                                   0.0773817
                                   0.0742165
                                      18
Hour beginning at 5:00 PM
                                   0.077432
                                   0.0678874
                                   0.0754816
                                   0.0700091
                                      19
Hour beginning at 6:00 PM
                                   0.059783
                                   0.0617718
                                   0.0587059
                                   0.0614038
                                      20
Hour beginning at 7:00 PM
                                   0.0443923
                                   0.0516882
                                   0.0439864
                                   0.0505043
                                      21
Hour beginning at 8:00 PM
                                   0.0354458
                                   0.0428658
                                   0.0357309
                                   0.0412072
                                      22
Hour beginning at 9:00 PM
                                   0.031824
                                   0.0380302
                                   0.0307428
                                   0.0336373
                                      23
Hour beginning at 10:00 PM
                                   0.0249419
                                   0.0322072
                                   0.0238521
                                   0.0262243
                                      24
Hour beginning at 11:00 PM
                                   0.0179068
                                   0.0245677
                                   0.0173177
                                   0.0191666
                                       
                             Sum of All Fractions
                                     1.000
                                     1.000
                                     1.000
                                     1.000

          Figure 12-1 Hourly VMT Fractions by Day Type and Road Type

 Engine Starts and Parking
To properly estimate engine start emissions and evaporative fuel vapor losses, it is important to estimate the number of starts by time of day, and the duration of time between vehicle trips. The time between trips with the engine off is referred to as "soak time". To determine typical patterns of trip starts and ends, MOVES uses information from instrumented vehicles. This data is stored in two tables in the MOVES default database.  We have made only minor changes for MOVE2014.

The first table, SampleVehicleDay, lists a sample population of vehicles, each with an identifier (vehID), an indication of vehicle type (sourceTypeID), and an indication (dayID) of whether the vehicle is part of the weekend or weekday vehicle population.  Some vehicles were added to this table to increase the number of vehicles in each day which do not take any trips to better match a recent study of vehicle activity in Georgia. This change is described in greater detail in the report describing evaporative emissions in MOVES2014.

The second table, SampleVehicleTrip, lists the trips in a day made by each of the vehicles in the SampleVehicleDay table. It records the vehID, dayID, a trip number (tripID), the hour of the trip (hourID), the trip number of the prior trip (priorTripID), and the times at which the engine was turned on and off for the trip.  The keyOnTime and keyOffTime are recorded in minutes since midnight of the day of the trip. 439 trips (about 1.1%) were added to this table to assure that at least on trip is done by a vehicle from each source type in each hour of the day to assure that emission rates will be calculated in each hour.  Light-duty vehicle trip and soak data was copied to all the other source types (11, 41, 42, 43, 51, 52, 53, 54, 61, and 62) for both weekdays (dayID 5) and weekends (dayID 2) for hours with no trips. 

To account for overnight soaks, many first trips reference a prior trip with a null value for keyOnTime and a negative value for keyOffTime. The SampleVehicleDay table also includes some vehicles that have no trips in the SampleVehicleTrip table to account for vehicles that sit for one or more days without driving at all.

The data and processing algorithms used to populate these tables are detailed in two contractor reports., The data comes from a variety of instrumented vehicle studies, summarized in Table 12-6. This data was cleaned, adjusted, sampled and weighted to develop a distribution intended to represent average urban vehicle activity.  

          Table 12-6 Source Data for Sample Vehicle Trip Information
                                     Study
                                  Study Area
                                  Study Years
                                 Vehicle Types
                                 Vehicle Count
3-City FTP Study
Atlanta, GA; Baltimore, MD; Spokane, WA
                                     1992
Passenger cars & trucks
                                                                            321
Minneapolis
Minneapolis/St. Paul, MN
                                   2004-2005
Passenger cars & trucks
                                                                            133
Knoxville
Knoxville, TN
                                   2000-2001
Passenger cars & trucks
                                                                            377
Las Vegas
Las Vegas, NV
                                   2004-2005
Passenger cars & trucks
                                                                            350
Battelle
California, statewide
                                   1997-1998
Heavy-duty trucks
                                                                            120
TxDOT
Houston, TX
                                     2002
Diesel dump trucks
                                                                              4
                                                                               

For vehicle classes that were not represented in the available data, the contractor synthesized trips using trip-per-operating hour information from the EPA MOBILE6 model and soak time and time-of-day information from source types that did have data. The application of synthetic trips is summarized in Table 12-7. 

                                       
     Table 12-7 Synthesis of Sample Vehicles for Source Types Lacking Data
                                  Source Type
                             Based on Direct Data?
                               Synthesized From
Motorcycles
                                      No
Passenger Cars
Passenger Cars
                                      Yes
n/a
Passenger Trucks
                                      Yes
n/a
Light Commercial Trucks
                                      No
Passenger Trucks
Intercity Buses
                                      No
Combination long-haul trucks
Transit Buses
                                      No
Single unit short-haul trucks
School Buses
                                      No
Single unit short-haul trucks
Refuse Trucks
                                      No
Combination short-haul trucks
Single unit short-haul trucks
                                      Yes
n/a
Single unit long-haul trucks
                                      No
Combination long-haul trucks
Motor homes
                                      No
Passenger Cars
Combination short-haul trucks
                                      Yes
n/a
Combination long-haul trucks
                                      Yes
n/a

The resulting trip-per-day estimates are summarized in Table 12-8.  The same estimate for trips per day is used for all ages of vehicles in any calendar year.

                   Table 12-8 Starts per Day by Source Type
                                  Source Type
                                   MOVES2014
                                    Weekday
                                   MOVES2014
                                    Weekend
Motorcycles
                                     0.78
                                     0.79
Passenger Cars
                                     5.89
                                     5.30
Passenger Trucks
                                     5.80
                                     5.06
Light Commercial Trucks
                                     6.05
                                     5.47
Intercity Buses
                                     2.77
                                     0.88
Transit Buses
                                     4.58
                                     3.46
School Buses
                                     5.75
                                     1.26
Refuse Trucks
                                     3.75
                                     0.92
Single unit short-haul trucks
                                     6.99
                                     1.28
Single unit long-haul trucks
                                     4.29
                                     1.29
Motor homes
                                     0.57
                                     0.57
Combination short-haul trucks
                                     5.93
                                     1.16
Combination long-haul trucks
                                     4.29
                                     1.29
 
MOVES2014 now has inputs in the County Data Manager that allows users to specify the number of engine starts in each month, day type and hour of the day, as well as by source type and vehicle age.  These user inputs override the default values provided by MOVES.

The same trip information that is used to determine the number of engine starts is also used to determine the vehicle soak time. "Soak time" is the time between trips when the engine is off.  The soak times are used to estimate the activity in each of the operating modes for engine start emissions.  The base emission rate for engine starts is based on a 12 hour soak period.  All engine soaks greater than 12 hours assume the same engine start emission rate as for 12 hours.  However, for all engine soaks less than 12 hours, the base engine start emission rate is adjusted based on soak time bins (operating modes).3,4 The distribution of operating modes in each hour of the day is part of the calculation used to determine the engine start emissions for that hour of the day. 
A more complete discussion of the relationship between engine soak time and emissions will be found in the MOVES report covering engine start emission rates used in MOVES.3

 Hourly Hotelling Activity
The hotelling hours in each day should not track the miles traveled in each hour, since hotelling occurs only when drivers are not driving.  Instead, the fraction of hours spent hotelling by time of day can be derived from other sources. In particular, the report, Roadway-Specific Driving Schedules for Heavy-Duty Vehicles,[53] combines data from several instrumented truck studies and contains detailed information about truck driver behavior.  While none of the trucks were involved in long haul interstate activity, for lack of better data, we have assumed that long haul truck trips have the same hourly truck trip distribution as the heavy heavy-duty trucks that were studied.

For each hour of the day, we estimated the number of trips that would end in that hour, based on the number of trips that started 10 hours earlier. The hours of hotelling in that hour is the number that begin in that hour, plus the number that began in the previous hour, plus the number that began in the hour before that, and so on, up to the required eight hours of rest time.  Table 12-9 shows the number of trip starts and inferred trip ends over the hours of the day in the sample of trucks assuming all trips are 10 hours long. For example, the number of trip ends in hour 1 is the same as the number of trip starts 10 hours earlier in hour 15 of the previous day.

Table 12-9 Hourly Distribution of Truck Trips used to calculate hotelling hours
                                    hourID
                                Hour of the Day
                                  Trip Starts
                                   Trip Ends
                                       1
Hour beginning at 12:00 midnight
                                      78
                                      171
                                       2
Hour beginning at 1:00 AM
                                      76
                                      167
                                       3
Hour beginning at 2:00 AM
                                      65
                                      144
                                       4
Hour beginning at 3:00 AM
                                      94
                                      98
                                       5
Hour beginning at 4:00 AM
                                      107
                                      71
                                       6
Hour beginning at 5:00 AM
                                      131
                                      73
                                       7
Hour beginning at 6:00 AM
                                      194
                                      71
                                       8
Hour beginning at 7:00 AM
                                      230
                                      52
                                       9
Hour beginning at 8:00 AM
                                      279
                                      85
                                      10
Hour beginning at 9:00 AM
                                      267
                                      48
                                      11
Hour beginning at 10:00 AM
                                      275
                                      78
                                      12
Hour beginning at 11:00 AM
                                      240
                                      76
                                      13
Hour beginning at 12:00 Noon
                                      201
                                      65
                                      14
Hour beginning at 1:00 PM
                                      211
                                      94
                                      15
Hour beginning at 2:00 PM
                                      171
                                      107
                                      16
Hour beginning at 3:00 PM
                                      167
                                      131
                                      17
Hour beginning at 4:00 PM
                                      144
                                      194
                                      18
Hour beginning at 5:00 PM
                                      98
                                      230
                                      19
Hour beginning at 6:00 PM
                                      71
                                      279
                                      20
Hour beginning at 7:00 PM
                                      73
                                      267
                                      21
Hour beginning at 8:00 PM
                                      71
                                      275
                                      22
Hour beginning at 9:00 PM
                                      52
                                      240
                                      23
Hour beginning at 10:00 PM
                                      85
                                      201
                                      24
Hour beginning at 11:00 PM
                                      48
                                      211

An estimate of the distribution of truck hotelling duration times is derived from a 2004 CRC paper based on a survey of 365 truck drivers at 6 different locations.  Table 12-10 lists the fraction of trucks in each duration bin.  Some trucks are hotelling for more than the required eight hours, but some are hotelling for less than eight hours.

         Table 12-10 Distribution of Truck Hotelling Activity Duration
                               Duration (hours)
                              Fraction of Trucks
                                       2
                                     0.227
                                       4
                                     0.135
                                       6
                                     0.199
                                       8
                                     0.191
                                      10
                                     0.156
                                      12
                                     0.057
                                      14
                                     0.014
                                      16
                                     0.021
                                     Total
                                     1.000

We assume that all hotelling activity begins at the trip ends shown in Table 12-9. The distribution of hotelling durations from Table 12-10 is applied to these trip ends.  These calculations are shown in Table 12-11.  The column "2 hours" adds the number of trip ends in the previous 2 hours, assuming all trips will have 2 hours of hotelling after their trip ends, the column "4 hours" adds the trips ends in the previous 4 hours, etc.  The first hour of hotelling in each category is reduced by 60% to account for the fact that not all of the trips actually ended at the beginning of the hour.  The total hotelling hours is the product of the total hours in each column multiplied by the fraction of trucks with each duration from Table 12-10.

     Table 12-11 Calculation of Hourly Distributions of Hotelling Activity

                                    hourID
                                  Trip Starts
                                  Trip Ends*
                                    2 hours
                                    4 hours
                                    6 hours
                                    8 hours
                                   10 hours
                                   12 hours
                                   14 hours
                                   16 hours
                                  Total Hours
                                 Distribution
                                       1
                                                                             78
                                                                            171
                                                                          255.4
                                                                            679
                                                                         1204.8
                                                                           1736
                                                                         2120.4
                                                                         2343.6
                                                                         2495.4
                                                                         2638.2
                                                                           1276
                                    0.0628
                                       2
                                                                             76
                                                                            167
                                                                          235.4
                                                                          629.4
                                                                           1100
                                                                         1643.6
                                                                         2118.6
                                                                         2408.8
                                                                           2593
                                                                         2739.2
                                                                           1234
                                    0.0611
                                       3
                                                                             65
                                                                            144
                                                                          210.8
                                                                          566.4
                                                                            990
                                                                         1515.8
                                                                           2047
                                                                         2431.4
                                                                         2654.6
                                                                         2806.4
                                                                           1166
                                    0.0577
                                       4
                                                                             94
                                                                             98
                                                                          155.6
                                                                          477.4
                                                                          871.4
                                                                           1342
                                                                         1885.6
                                                                         2360.6
                                                                         2650.8
                                                                           2835
                                                                           1056
                                    0.0526
                                       5
                                                                            107
                                                                             71
                                                                          110.2
                                                                          379.8
                                                                          735.4
                                                                           1159
                                                                         1684.8
                                                                           2216
                                                                         2600.4
                                                                         2823.6
                                                                            930
                                    0.0458
                                       6
                                                                            131
                                                                             73
                                                                          101.4
                                                                          299.6
                                                                          621.4
                                                                         1015.4
                                                                           1486
                                                                         2029.6
                                                                         2504.6
                                                                         2794.8
                                                                            823
                                    0.0407
                                       7
                                                                            194
                                                                             71
                                                                          100.2
                                                                          254.2
                                                                          523.8
                                                                          879.4
                                                                           1303
                                                                         1828.8
                                                                           2360
                                                                         2744.4
                                                                            728
                                    0.0357
                                       8
                                                                            230
                                                                             52
                                                                           80.4
                                                                          224.4
                                                                          422.6
                                                                          744.4
                                                                         1138.4
                                                                           1609
                                                                         2152.6
                                                                         2627.6
                                                                            630
                                    0.0306
                                       9
                                                                            279
                                                                             85
                                                                          105.8
                                                                          237.2
                                                                          391.2
                                                                          660.8
                                                                         1016.4
                                                                           1440
                                                                         1965.8
                                                                           2497
                                                                            581
                                    0.0289
                                      10
                                                                            267
                                                                             48
                                                                             82
                                                                          213.4
                                                                          357.4
                                                                          555.6
                                                                          877.4
                                                                         1271.4
                                                                           1742
                                                                         2285.6
                                                                            507
                                    0.0255
                                      11
                                                                            275
                                                                             78
                                                                           97.2
                                                                          231.8
                                                                          363.2
                                                                          517.2
                                                                          786.8
                                                                         1142.4
                                                                           1566
                                                                         2091.8
                                                                            479
                                    0.0238
                                      12
                                                                            240
                                                                             76
                                                                          107.2
                                                                            236
                                                                          367.4
                                                                          511.4
                                                                          709.6
                                                                         1031.4
                                                                         1425.4
                                                                           1896
                                                                            457
                                    0.0221
                                      13
                                                                            201
                                                                             65
                                                                           95.4
                                                                          238.2
                                                                          372.8
                                                                          504.2
                                                                          658.2
                                                                          927.8
                                                                         1283.4
                                                                           1707
                                                                            434
                                    0.0221
                                      14
                                                                            211
                                                                             94
                                                                            120
                                                                          266.2
                                                                            395
                                                                          526.4
                                                                          670.4
                                                                          868.6
                                                                         1190.4
                                                                         1584.4
                                                                            447
                                    0.0221
                                      15
                                                                            171
                                                                            107
                                                                          144.6
                                                                          296.4
                                                                          439.2
                                                                          573.8
                                                                          705.2
                                                                          859.2
                                                                         1128.8
                                                                         1484.4
                                                                            476
                                    0.0238
                                      16
                                                                            167
                                                                            131
                                                                          173.8
                                                                            358
                                                                          504.2
                                                                            633
                                                                          764.4
                                                                          908.4
                                                                         1106.6
                                                                         1428.4
                                                                            526
                                    0.0255
                                      17
                                                                            144
                                                                            194
                                                                          246.4
                                                                          469.6
                                                                          621.4
                                                                          764.2
                                                                          898.8
                                                                         1030.2
                                                                         1184.2
                                                                         1453.8
                                                                            635
                                    0.0323
                                      18
                                                                             98
                                                                            230
                                                                          307.6
                                                                          597.8
                                                                            782
                                                                          928.2
                                                                           1057
                                                                         1188.4
                                                                         1332.4
                                                                         1530.6
                                                                            767
                                    0.0374
                                      19
                                                                             71
                                                                            279
                                                                            371
                                                                          755.4
                                                                          978.6
                                                                         1130.4
                                                                         1273.2
                                                                         1407.8
                                                                         1539.2
                                                                         1693.2
                                                                            933
                                    0.0458
                                      20
                                                                             73
                                                                            267
                                                                          378.6
                                                                          853.6
                                                                         1143.8
                                                                           1328
                                                                         1474.2
                                                                           1603
                                                                         1734.4
                                                                         1878.4
                                                                           1068
                                    0.0526
                                      21
                                                                             71
                                                                            275
                                                                          381.8
                                                                            913
                                                                         1297.4
                                                                         1520.6
                                                                         1672.4
                                                                         1815.2
                                                                         1949.8
                                                                         2081.2
                                                                           1194
                                    0.0594
                                      22
                                                                             52
                                                                            240
                                                                            350
                                                                          893.6
                                                                         1368.6
                                                                         1658.8
                                                                           1843
                                                                         1989.2
                                                                           2118
                                                                         2249.4
                                                                           1268
                                    0.0628
                                      23
                                                                             85
                                                                            201
                                                                            297
                                                                          822.8
                                                                           1354
                                                                         1738.4
                                                                         1961.6
                                                                         2113.4
                                                                         2256.2
                                                                         2390.8
                                                                           1289
                                    0.0645
                                      24
                                                                             48
                                                                            211
                                                                          291.4
                                                                            762
                                                                         1305.6
                                                                         1780.6
                                                                         2070.8
                                                                           2255
                                                                         2401.2
                                                                           2530
                                                                           1308
                                    0.0645
                                    Totals
                                                                           3428
                                                                           3428
                                                                           4799
                                                                          11655
                                                                          18511
                                                                          25367
                                                                          32223
                                                                          39079
                                                                          45935
                                                                          52791
                                                                          20213
                                    1.0000
* Assumes all trip ends occur 10 hours after trips start and all trips are 10 hours long.

The first hour of hotelling in each hour bin column sum is reduced by 60% to account for trip ends in a column that are not a full hour.

The distribution calculated using this method is similar to the behavior observed in a dissertation at the University of Tennessee, Knoxville.  This study observed the trucks parking at the Petro truck travel center located at the I40/I75 and Watt Road interchange between mid-December 2003 and August 2004.  Rather than use a study at a specific location, MOVES2014 uses the more generic simulated values to determine the diurnal distribution of hotelling behavior. The distribution of total hotelling hours to hours of the day is calculated from the total hotelling hours and stored in the SourceTypeHour table of the default MOVES2014 database.  

MOVES2014 uses this same default hourly distribution from Table 12-11 for all days and locations, as shown below in Figure 12-2.  Note, this distribution of hotelling by hour of the day is similar to the inverse of the VMT distribution used for these trucks by hour of the day.  

   Figure 12-2 Truck hotelling distribution by hour of the day in MOVES2014

 Single and Multiday Diurnals
The evaporative vapor losses from gasoline vehicle fuel tanks are affected by many factors, including the number of hours a vehicle is parked without an engine start, referred to as engine soak time.  Most modern gasoline vehicles are equipped with emission control systems designed to capture most evaporative vapor losses and store them.  These stored vapors are then burned in the engine once the vehicle is operated.  However, the vehicle storage capacity for evaporative vapors is limited and multiple days of parking (diurnals) will overload the storage capacity of these systems, resulting in larger losses of evaporative vapors in subsequent days.

The soak time calculations are discussed in Section 12.4.  The detailed description of the calculation for the number of vehicles that have been soaking for more than a day and the amount of time that the vehicles have been soaking can be found in the MOVES technical report on evaporative emissions.[63]

 Geographical Allocation of Activity
MOVES is designed to model activity at a "domain" level and then to allocate that activity to "zones." The MOVES2014 default database is populated for a domain of the entire United States (including Puerto Rico and the Virgin Islands), and the default zones correspond to individual counties. The MOVES design only allows for one set of geographic allocations to be stored in the default database.  While geographic allocations clearly change over time, the MOVES defaults were developed using the data from calendar year 2011, and are used for all calendar years. For this reason, the MOVES default allocation of activity is rarely used for any official purpose by either EPA or local areas.  National-level emissions can be generated with calendar year specific geographical information by running each year separately, with different user-input allocations for each run. County- and Project-level calculations do not use the default geographical allocation factors at all. Instead, County and Project scales require that the user input local total activity for each individual year being modeled.  The MOVES geographic allocation factors are stored in two tables, Zone and ZoneRoadType. 

 Source Hours Operating Allocation to Zones

Most of the emission rate calculations in MOVES2014 are based on emission rates by time units (hour). Using time units for emissions is the most flexible approach, since the activity for some processes (like leaks) and some source types (like nonroad generators) are more naturally in units of time.  As a result, MOVES converts activity data to hours in many cases in order to produce the hours needed for emissions calculations.

The national total source hours of operation (SHO) are calculated from the estimates of VMT and speed as described in sections above. This total VMT for each roadtype is allocated to county using the SHOAllocFactor field in the ZoneRoadType table. The allocation factors are derived using 2011 VMT and MOVES default VMT. 
 
In particular, the MOVES2014 default estimates for the VMT by county come from Version 1 of the 2011 National Emission Inventory (NEI) analysis.[43] These estimates are based on the Highway Performance Monitoring System (HPMS) state level data collected by the Federal Highway Administration annually for use in transportation planning.  The HPMS state level VMT is distributed to the individual counties in each state as part of the NEI analysis.  This data is reviewed and updated by the states as necessary prior to use in the NEI. The default inputs for SHOAllocFactor in MOVES2014 were calculated using the VMT estimates obtained from Version 1 of the 2011 NEI for each county by road type. 

Vehicle miles traveled can be converted to hours of travel using average speeds.  The average speed estimates were taken directly from the AvgSpeedDistribution table of the MOVES default database. The default average speed distributions do not vary by county or source type, but do vary by road type, day type (weekday and weekend day) and hour of the day.  The 2011 NEI VMT was aggregated into the four MOVES road types in each county.  The VMT by road type in each county was then allocated to day type and hour of the day using the day type and hour distributions from the MOVES default database tables, DayMVTFraction and HourVMTFraction.

Using the nominal speeds for each average speed bin in the AvgSpeedDistribution table for each hour of each day type and the corresponding VMT, the hours of vehicle operation (SHO) can be calculated for each hour of the day on each road type for each day type in each county.  The average speed distribution is in units of time, so the distribution must be converted to units of distance to be applied to the VMT values.  For this step, we  multiplied each value of each distribution (in terms of time) by the corresponding nominal average speed value for that average speed bin to calculate distance (hours * miles/hour).  Then we divided each distance value in the distribution by the sum of all distance values in that distribution to calculate the average speed distribution in terms of distance.

Finally, we multiplied the total VMT corresponding to each average speed distance distribution (by road type, by day type, by hour of the day) by each of the values in the distribution to calculate the VMT corresponding to each average speed bin.  We then then calculated operating hours by dividing the VMT in each average speed bin by the corresponding nominal average speed value.

                                       
                  SHO = VMT (miles) / Speed (miles per hour)
Equation 29

Once the hours of operation have been calculated, the hours in each county were summed by road type.  The allocation factor for each county was calculated by dividing the county hours for each road type by the national total hours of operation for each road type.

SHOAllocFactor = County SHO / National SHO
Equation 30

The county allocation values for each roadway type sum to one (1.0) for the nation.  The same SHOAllocFactor set is the default for all calendar years at the National scale.  County- and Project-level calculations do not use the default SHOAllocFactor allocations at all. Instead, County and Project scales require that the user input all local activity.

 Engine Start Allocations to Zones
The allocation of the domain-wide count of engine starts to zones is stored in the StartAllocFactor in the Zone table. In the default database for MOVES2014, the domain is the nation and the zones are counties. There is no national source for data on the number of trip starts by county, so for MOVES2014, we have used VMT to determine this allocation.  VMT for each county was taken from the most recent National Emission Inventory analysis for calendar year 2011.[66]

VMT estimates for each county in each state and the allocation is calculated using the following formula, where i represents each individual county and I is the set of all US counties.

CountyAllocationi= CountyVMTiiϵICountyVMTi
Equation 31

The county allocation values sum to one (1.0) for the nation.  The same StartAllocFactor set is the default for all calendar years at the National scale.  County- and Project-level calculations do not use the default StartAllocFactor allocations at all. Instead, County and Project scales require that the user input all local activity.

 Parking Hours Allocation to Zones
The allocation of the domain-wide hours of parking (engine off) to zones is stored in the SHPAllocFactor in the Zone table. In the default database for MOVES2014, the domain is the nation and the zones are the counties. There is no national source for hours of parking by county, so for MOVES2014, we have used the same VMT-based allocation as used for the allocation of starts in the StartAllocFactor (see above).

The county allocation values for parking hours sum to one (1.0) for the nation.  The same SHPAllocFactor set is the default for all calendar years at the National scale.  County- and Project-level calculations do not use the default SHPAllocFactor allocations at all. Instead, County and Project scales require that the user input all local activity.

In MOVES2014, hotelling hours (including extended idling and auxiliary power unit usage) are calculated from long haul combination truck VMT in each location and does have its own allocation factors.

Vehicle Mass and Road Load Coefficients
The MOVES model calculates emissions using a weighted average of emisson rates by operating mode. This level of detail is required for microscale modeling, which in MOVES is called project level analysis. For running exhaust emissions, the operating modes are defined by either Vehicle Specific Power (VSP) or Scaled Tractive Power (STP). Both VSP and STP are calculated based on a vehicle's speed and acceleration but differ in how they are scaled (or normalized). VSP is used for light-duty vehicles (source types 11-32) and STP is used for heavy-duty vehicles (source types 41-62).

The SourceUseTypePhysics table describes the vehicle characteristics needed for the VSP and STP calculations, including average vehicle mass, a fixed mass factor, and three road load coefficients for each source type averaged over all ages. MOVES uses these to calculate VSP and STP for each source type according the equations:
                                       
                  VSP=AM∙v+BM∙v2+CM∙v3+a+g∙sinθ∙v
                                                                    Equation 32
                                       
                   STP=Av+Bv2+Cv3+M∙v∙at+g∙sinθfscale
                                                                    Equation 33
where A, B, and C are the road load coefficients in units of kW-sm, kW-s2m2, and kW-s3m3  respectively.  A is associated with tire rolling resistence, B with mechanical rotating friction as well as higher order rolling resistance losses, and C with aerodynamic drag. M is the source mass for the source type in metric tons, g is the acceleration due to gravity 9.8 ms2, v is the instantaneous vehicle speed in ms, a is the instantaneous vehicle acceleration in ms2, sinθ is the (fractional) road grade, and fscale is a scaling factor. 

When mapping actual emissions data to VSP bins with Equation 20, the vehicle's measured weight is used as the source mass factor. In contrast, when calculating average VSP distributions for an entire source type with MOVES, the average source type mass is used instead. STP is calculated with Equation 21, which is very similar to the VSP equation except the denominators are different. In the case of VSP, the power is normalized by the mass of the vehicle (fscale=M). For heavy-duty vehicles using STP, fscale depends on their regulatory class and is used to bring the numerical range of tractive power into the same numerical range as the VSP values when assigning operating modes. Class 40 trucks use fscale= 2.06, which is equal to the mass of source type 32 in metric tons. This is because operating modes for passenger trucks and light-commercial trucks are assigned operating modes using VSP, and using a fixed mass factor of 2.06 essentially calculates VSP-based emission rates. Running operating modes for all the heavy-duty source types (buses, single unit, and combination trucks) are assigned using STP with fscale=17.1, which is roughly equivalent to the average running weight in metric tons of all heavy-duty vehicles. Additional discussion regarding VSP and STP are provided in the MOVES light-duty[3] and heavy-duty[4] emission rate reports, respectively.
	
In both cases, operating mode distributions are derived from combining second-by-second speed and acceleration data from a specific drive schedule with the proper coefficients for a specific source type. More information about drive schedules can be found in Section 10.1.  The following sections detail the derivation of values used in Equation 20 and Equation 21.
 Source Mass and Fixed Mass Factor
The two mass factors stored in the SourceUseTypePhysics table are the source mass and fixed mass factor. The source mass represents the average weight of a given source type, which includes the weight of the vehicle, occupants, fuel, and payload (Min the equations above), and the fixed mass factor represents the STP scaling factor (fscale in the equations above).
 
While the source masses for light-duty were unchanged from MOVES2010b, all of the heavy-duty source masses were updated with newer data. Please see Section 21. (Appendix E: MOVES2010b Source Masses) for a discussion of the MOVES2010b source masses. The heavy-duty source masses for 2014+ model year vehicles heavy-duty vehicles were first updated to account for the 2014 Medium and Heavy-Duty Greenhouse Gase Rule as discussed in Section 14.2. Then the heavy-duty source masses were updated with 2011 Weigh-in-Motion (WIM) data made available through FHWA's Vehicle Travel Information System (VTRIS). These data are available from FHWA by state, road type, and HPMS truck type (single unit or combination). The average national mass by truck type was calculated by weighting the masses with VMT by state and road type using FHWA's Highway Statistics VM-2 table. These average values then needed to be allocated from the HPMS truck classification to source types. This allocation was performed using the percent difference between the average WIM HPMS mass and the average MOVES2010b HPMS mass. The MOVES2010b average masses were calculated by weighting the source type masses with the updated 2011 VMT. The percentage difference between the average single unit truck mass in MOVES2010b and the WIM data was then applied to the source masses of Single Unit Short-haul Trucks, Single Unit Long-haul Trucks, Refuse Trucks, and Motor Homes. Likewise, the percentage difference between the average combination truck mass in MOVES2010b and the WIM data was applied to the source masses of Combination Short-haul Trucks and Combination Long-haul Trucks, including the 2014+ model year groups. These differences are shown in Table 14-1, and the resulting source type masses are presented in Table 14-4.

            Table 14-1 Weigh-in-Motion (WIM) Masses Weighted by VMT
                                 HPMS Category
                             Average Weight (lbs)
                           % Change from MOVES2010b
                              Single Unit Trucks
                                    20,107
                                     11.7%
                              Combination Trucks
                                    52,907
                                    -21.7%

 Road Load Coefficients
The information available on road load coefficients varied by regulatory class. Motorcycle road load coefficients were parameterized, in accordance with standard practice, using the following emperical equations[,]:
                                       
                                  A=0.088∙M
                                  Equation 34
                                       
                                      B=0
                                  Equation 35
                                       
                            C=0.00026+0.000194∙M
                                  Equation 36
For light-duty vehicles, the road load coefficients were calculated according to the following empirical equations:
                                       
                    A=0.745750∙0.447∙0.35∙TRLHP@50mph
                                  Equation 37
                                       
                   B=0.745750∙0.4472∙0.10∙TRLHP@50mph
                                  Equation 38
                                       
                   C=0.745750∙0.4473∙0.55∙TRLHP@50mph
                                  Equation 39
In each of the above equations, the first factor is the appropriate unit conversion to allow A, B, and C to be used in Equation 20 and Equation 21, the second factor is the power distribution into each of the three load categories, and the third is the tractive road load horsepower rating (TRLHP). Average values for A, B, and C for source types 21, 31, and 32 were derived from applying TRLHP values recorded in the Mobile Source Observation Database (MSOD) to Equation 25-Equation 27. While we expect light-duty road load coefficients to improve over time due to the Light-Duty Greenhouse Gas Rule, the impact of these changes have been directly incorporated into the emission and energy rates. Therefore, these coefficients remain constant over time.

For the heavier vehicles, no road load parameters were available in the MSOD. For these source types, relationships of road load coefficent to vehicle mass came from a study done by V.A. Petrushov, as shown in Table 14-2. These relationships are grouped by regulatory class; source type values were determined by weighting the combination of MOVES2010b weight categories that comprise the individual source types. The final SourceMass, FixedMassFactor and road load coefficients for all source types are listed in Table 14-4. 

Table 14-2 Road Load Coefficients for Heavy-Duty Trucks, Buses, and Motor Homes for 1960-2013 Model Year Vehicles
                                  Coefficient
                               8500 to 14000 lbs
                          (3.855 to 6.350 metric ton)
                              14000 to 33000 lbs
                         (6.350 to 14.968 metric ton)
                                 >33000 lbs
                            (>14.968 metric ton)
                             Buses and Motor Homes
                                    AkW-sm
                                  0.0996∙M
                                  0.0875∙M
                                  0.0661∙M
                                  0.0643∙M
                                   BkW-s2m2
                                       0
                                       0
                                       0
                                       0
                                   CkW-s3m3
                                   0.00289+
                                5.22x10-5∙M
                                   0.00193+
                                5.90x10-5∙M
0.00289+
4.21x10-5∙M
                                    0.0032+
                                5.06x10-5∙M

In MOVES2014, the vehicle mass and road load coefficient were updated for 2014 and later model year heavy-duty vehicles to account for the 2014 Medium and Heavy-Duty Greenhouse Gase Rule. Table 14-3 contains the combination long-haul tractor and vocational vehicle tire rolling resistance, coefficient of drag, and weight reductions expected from the technologies which could be used to meet the standards.  The value in the table reflects a 400 pound mass reduction.  As discussed in the rulemaking, EPA used a sales mix of 10 percent Class 7 low roof, 10 percent Class 7 high roof, 45 percent Class 8 low roof, and 35 percent Class 8 high roof based on feedback from the manufacturers. 

The values in the table reflect a modeling assumption that 8 percent of all tractors (19.7 percent of short-haul tractors) would be considered vocational tractors and therefore will only be required to meet the vocational vehicle standards and not show any aerodynamic or weight improvement. The weight reduction applied to short-haul tractors is 321 pounds which is calculated from the 400 pound weight reduction assumed for non-vocational tractors, reduced by 19.7 percent.  The tire rolling resistance reduction is assumed to be 5 percent based on the data derived in the tire testing program conducted by EPA. Comparatively tire rolling resistance is reduced by 9.6 percent for long-haul tractors and 7 percent for short-haul tractors while aerodynamic drag is reduced 12.1 percent for long-haul tractors and 5.9 percent for short-haul tractors in model year 2014 and later. For further details on these assumptions about reductions in source mass and road load coefficients, please see the rulemaking documents. Discussion of incorporating the rule's energy reductions from engine technology improvements into MOVES can be found in the MOVES2014 Heavy-Duty Emission Rate Report.[4]
      
Table 14-3 Estimated Reductions in Rolling Resistance and Aerodynamic Drag Coefficients from Reference Case for Alternative 3 (Model Years 2014 and Later)
                                  TRUCK TYPE
        REDUCTION IN TIRE ROLLING RESISTANCE COEFFICIENT FROM BASELINE
            REDUCTION IN AERODYNAMIC DRAG COEFFICIENT FROM BASELINE
                            WEIGHT REDUCTION (LBS)
Combination long-haul
                                     9.6%
                                     12.1%
                                      400
Combination short-haul
                                     7.0%
                                     5.9%
                                      321
Vocational vehicles (Single-unit trucks, refuse trucks, motor homes, buses, and light commercial trucks) 
                                     5.0%
                                      0%
                                       0

      These changes are represented in MOVES2014 through new aerodynamic coefficients and weights, and they primarily affect short- and long-haul combination truck source types beginning in MY 2014. The average vehicle mass and road load coefficients are updated by source type through the beginModelYearID and endModelYearID fields in the SourceUseTypePhysics table. 

                     Table 14-4 SourceUseTypePhysics Table
                                 sourceTypeID
                               Begin Model Year 
                                      End
                                  Model Year
                                    Rolling
                                    Term A
                                   (kW-s/m)
                                   Rotating
                                    Term B
                                (kW-s[2]/m[2])
                                     Drag
                                    Term C
                                  (kW-s3/m3)
                                  Source Mass
                                 (metric tons)
                        Fixed Mass Factor (metric tons)
                                      11
                                     1960
                                     2050
                                    0.0251
                                       0
                                    0.0003
                                    0.2850
                                    0.2850
                                      21
                                     1960
                                     2050
                                    0.1565
                                    0.0020
                                    0.0005
                                    1.4788
                                    1.4788
                                      31
                                     1960
                                     2050
                                    0.2211
                                    0.0028
                                    0.0007
                                    1.8669
                                    1.8669
                                      32
                                     1960
                                     2050
                                    0.2350
                                    0.0030
                                    0.0007
                                    2.0598
                                    2.0598
                                      41
                                     1960
                                     2013
                                    1.2952
                                       0
                                    0.0037
                                    19.5937
                                     17.1
                                      41
                                     2014
                                     2050
                                    1.2304
                                       0
                                    0.0037
                                    19.5937
                                     17.1
                                      42
                                     1960
                                     2013
                                    1.0944
                                       0
                                    0.0036
                                    16.5560
                                     17.1
                                      42
                                     2014
                                     2050
                                    1.0397
                                       0
                                    0.0036
                                    16.5560
                                     17.1
                                      43
                                     1960
                                     2013
                                    0.7467
                                       0
                                    0.0022
                                    9.0699
                                     17.1
                                      43
                                     2014
                                     2050
                                    0.7094
                                       0
                                    0.0022
                                    9.0699
                                     17.1
                                      51
                                     1960
                                     2013
                                    1.5835
                                       0
                                    0.0036
                                    23.1135
                                     17.1
                                      51
                                     2014
                                     2050
                                    1.5043
                                       0
                                    0.0036
                                    23.1135
                                     17.1
                                      52
                                     1960
                                     2013
                                    0.6279
                                       0
                                    0.0016
                                    8.5390
                                     17.1
                                      52
                                     2014
                                     2050
                                    0.5965
                                       0
                                    0.0016
                                    8.5390
                                     17.1
                                      53
                                     1960
                                     2013
                                    0.5573
                                       0
                                    0.0015
                                    6.9845
                                     17.1
                                      53
                                     2014
                                     2050
                                    0.5294
                                       0
                                    0.0015
                                    6.9845
                                     17.1
                                      54
                                     1960
                                     2013
                                    0.6899
                                       0
                                    0.0021
                                    7.5257
                                     17.1
                                      54
                                     2014
                                     2050
                                    0.6554
                                       0
                                    0.0021
                                    7.5257
                                     17.1
                                      61
                                     1960
                                     2013
                                    1.5382
                                       0
                                    0.0040
                                    22.9745
                                     17.1
                                      61
                                     2014
                                     2050
                                    1.4305
                                       0
                                    0.0038
                                    22.8289
                                     17.1
                                      62
                                     1960
                                     2013
                                    1.6304
                                       0
                                    0.0042
                                    24.6010
                                     17.1
                                      62
                                     2014
                                     2050
                                    1.4739
                                       0
                                    0.0037
                                    24.4196
                                     17.1

Air Conditioning Activity Inputs
This report describes three inputs used in determining the impact of air conditioning on emissions. The ACPenetrationFraction is the fraction of vehicles equipped with air conditioning. FunctioningACFraction describes the fraction of these vehicles in which the air conditioning system is working correctly. The ACActivityTerms relate air conditioning use to local heat and humidity. More information on air conditioning effects is provided in the MOVES technical report on adjustment factors.

ACPenetrationFraction
The ACPenetrationFraction is a field in the SourceTypeModelYear table. Default values, by source type and model year were taken from MOBILE6. Market penetration data by model year were gathered from Ward's Automotive Handbook for light-duty vehicles and light-duty trucks for model years 1972 through the 1995 for cars and 1975-1995 for light trucks. Rates in the first few years of available data are quite variable, so values for early model years were estimated by applying the 1972 and 1975 rates for cars and trucks, respectively. Projections beyond 1995 were developed by calculating the average yearly rate of increase in the last five years of data and applying this rate until a predetermined cap was reached. A cap of 98 percent was placed on cars and 95 percent on trucks under the assumption that there will always be vehicles sold without air conditioning, more likely trucks than cars. No data was available on heavy-duty trucks. While VIUS asks if trucks are equipped with A/C, "no response" was coded the same as "no," making the data unusable for this purpose. For MOVES, the light-duty vehicle rates were applied to passenger cars, and the light-duty truck rates were applied to all other source types (except motorcycles, for which A/C penetration is assumed to be zero). 

               Table 15-1 AC Penetration Fractions in MOVES2014
                                       
                                  Motorcycles
                                Passenger Cars
                             All Trucks and Buses
                               1972-and-earlier
                                       0
                                     0.592
                                     0.287
                                     1973
                                       0
                                     0.726
                                     0.287
                                     1974
                                       0
                                     0.616
                                     0.287
                                     1975
                                       0
                                     0.631
                                     0.287
                                     1976
                                       0
                                     0.671
                                     0.311
                                     1977
                                       0
                                     0.720
                                     0.351
                                     1978
                                       0
                                     0.719
                                     0.385
                                     1979
                                       0
                                     0.694
                                     0.366
                                     1980
                                       0
                                     0.624
                                     0.348
                                     1981
                                       0
                                     0.667
                                     0.390
                                     1982
                                       0
                                     0.699
                                     0.449
                                     1983
                                       0
                                     0.737
                                     0.464
                                     1984
                                       0
                                     0.776
                                     0.521
                                     1985
                                       0
                                     0.796
                                     0.532
                                     1986
                                       0
                                     0.800
                                     0.544
                                     1987
                                       0
                                     0.755
                                     0.588
                                     1988
                                       0
                                     0.793
                                     0.640
                                     1989
                                       0
                                     0.762
                                     0.719
                                     1990
                                       0
                                     0.862
                                     0.764
                                     1991
                                       0
                                     0.869
                                     0.771
                                     1992
                                       0
                                     0.882
                                     0.811
                                     1993
                                       0
                                     0.897
                                     0.837
                                     1994
                                       0
                                     0.922
                                     0.848
                                     1995
                                       0
                                     0.934
                                     0.882
                                     1996
                                       0
                                     0.948
                                     0.906
                                     1997
                                       0
                                     0.963
                                     0.929
                                     1998
                                       0
                                     0.977
                                     0.950
                                     1999+
                                       0
                                     0.980
                                     0.950

FunctioningACFraction 
The FunctioningACFraction field in the SourceTypeAge table indicates the fraction of the air-conditioning equipped fleet with fully functional A/C systems, by source type and vehicle age. A value of 1 means all systems are functional. This is used in the calculation of total energy to account for vehicles without functioning A/C systems. Default estimates were developed for all source types using the "unrepaired malfunction" rates used for 1992-and-later model years in MOBILE6. The MOBILE6 rates were based on the average rate of A/C system failure by age reported in a consumer study and assumptions about repair frequency during and after the warranty period. The MOBILE6 rates were applied to all source types except motorcycles, which were assigned a value of zero for all years. 

 Table 15-2 FunctioningACFraction by Age (All Source Types except Motorcycles)
                                     ageID
                             functioningACFraction
                                       0
                                       1
                                       1
                                       1
                                       2
                                       1
                                       3
                                       1
                                       4
                                     0.99
                                       5
                                     0.99
                                       6
                                     0.99
                                       7
                                     0.99
                                       8
                                     0.98
                                       9
                                     0.98
                                      10
                                     0.98
                                      11
                                     0.98
                                      12
                                     0.98
                                      13
                                     0.96
                                      14
                                     0.96
                                      15
                                     0.96
                                      16
                                     0.96
                                      17
                                     0.96
                                      18
                                     0.95
                                      19
                                     0.95
                                      20
                                     0.95
                                      21
                                     0.95
                                      22
                                     0.95
                                      23
                                     0.95
                                      24
                                     0.95
                                      25
                                     0.95
                                      26
                                     0.95
                                      27
                                     0.95
                                      28
                                     0.95
                                      29
                                     0.95
                                      30
                                     0.95

ACActivityTerms
In the MonthGroupHour table, ACActivityTerms A, B, and C are coefficients for a quadratic equation that calculates air conditioning activity demand as a function of the heat index. These terms are applied in the calculation of the A/C adjustment in the energy consumption calculator. The methodology and the terms themselves were originally derived for MOBILE6 and are documented in the report, Air Conditioning Activity Effects in MOBILE6.74 They are based on analysis of air conditioning usage data collected in Phoenix, Arizona, in 1994. 

In MOVES, ACActivityTerms are allowed to vary by monthGroup and Hour, in order to provide the possibility of different A/C activity demand functions at a given heat index by season and time of day (this accounts for differences in solar loading observed in the original data). However, for MOVES2014, the default data uses one set of coefficients for all MonthGroups and Hours. These default coefficients represent an average A/C activity demand function over the course of a full day. The coefficients are listed in Table 15-3.

               Table 15-3 Air Conditioning Activity Coefficients
                                       A
                                       B
                                       C
                                   -3.63154
                                   0.072465
                                   -0.000276
 
The A/C activity demand function that results from these coefficients is shown in Figure 15-1. A value of 1 means the A/C compressor is engaged 100 percent of the time; a value of 0 means no A/C compressor engagement. 

   Figure 15-1 Air Conditioning Activity Demand as a Function of Heat Index
0
0
.
1
0
.
2
0
.
3
0
.
4
0
.
5
0
.
6
0
.
7
0
.
8
0
.
9
1
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
1
0
5
1
1
0
H
e
a
t
 
I
n
d
e
x
 
(
F
)
0
0
.
1
0
.
2
0
.
3
0
.
4
0
.
5
0
.
6
0
.
7
0
.
8
0
.
9
1
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
1
0
5
1
1
0
H
e
a
t
 
I
n
d
e
x
 
(
F
)
Conclusion and Areas for Future Research
Properly characterizing emissions from vehicles requires a detailed understanding of the cars and trucks that make up the vehicle fleet, and their patterns of operation. The national default information in MOVES2014 provide a reliable basis for estimating national emissions. The most important of these inputs are well-established: base year VMT and population estimates come from long-term, systematic national measurements by US Department of Transportation. The emission characteristics for the most prevalent vehicle classes are well-known; base year age distributions are well-measured, and driving activity has been the subject of much study in recent years. 

Still, the fleet and activity inputs do have significant limitations, and the uncertainties and variability in this data can contribute significant uncertainty in resulting emission estimates. Thus it is often appropriate to replace many of the MOVES fleet and activity defaults with local data as explained in EPA's Technical Guidance. 

The fleet and activity defaults also are limited by the necessity of forecasting future emissions. EPA utilizes annual US Department of Energy forecasts of vehicle sales and activity, but the inputs for MOVES2014 were developed for a 2011 base year, and much of the source data is from 2011-and-earlier. This information needs to be updated periodically to assure that the model defaults reflect the latest available data and projections on the US fleet.

Updating the vehicle fleet data will be complicated by the fact that one of the primary data sources for this document, the Census Bureau's Vehicle Inventory and Use Survey, has been discontinued. EPA is currently working with DOT and other federal agencies to revive this survey.  Doing so becomes more and more important as the data gathered from the last survey (2002) ages.

A related complication is the cost of data. Collecting data on vehicle fleet and activity is expensive, especially when the data is intended to accurately represent the entire United States. Even when EPA does not generate data directly (for example, compilations of state vehicle registration data) obtaining the information needed for MOVES can be costly and, thus, dependent on large-scale budget choices.

In addition to these general limitations, there are also specific MOVES data elements that could be improved with additional research, including,

      * Real-world highway driving cycles and operating mode distributions,
      * Off-network behavior including vehicle starts and soaks,
      * Truck hotelling, particularly extended engine idling and APU use,
      * VSP/STP adjustments for speed, road grade, and loading,
      * Age effects such as mileage accumulation and scrappage,
      * Summaries of real-time GPS and on-board diagnostic device data streams, 
      * Vehicle identification and sorting by size, sector, and vocation.
      * Activity weighting of source mass averages.
      * Air Conditioning system penetration and failure rates.
      * Vehicle type distinctions in temporal activity, 
      * Heavy truck and bus daily trip activity patterns (particularly at night). 

Future updates to vehicle population and activity defaults will need to continue focus on the most critical elements required for national fleet-wide estimates, namely gasoline light-duty cars and trucks, and diesel heavy-duty trucks. Information collection on motorcycles, refuse trucks, motor homes, diesel light-duty vehicles and gasoline heavy-duty vehicles will be a lower priority. In addition to updating the model defaults, we will need to consider whether the current MOVES design continues to meet our modeling needs. Simplifications to the model to remove categories, such as source types or road types, might make noticeable improvements in run time without affecting the validity of fleet-wide emission estimates. 

At the same time, the fundamental MOVES assumption that vehicle activity varies by source type and not by fuel type or other source bin characteristic may be challenged by the growing market share of electric vehicles and other vehicles that may have distinct activity patterns. As we progress with MOVES, the development of vehicle population and activity inputs will continue to be an essential area of research.
      
      

Appendix A: Projected Source Type Populations by Year
Table 17-1: Source type populations (in thousands), as derived from HPMS populations in §5.2 and the age distribution algorithm in §7.1.2.2. 
                                     Year
                                  Motorcycle
                                 Passenger Car
                                Passenger Truck
                               Light Comm. Truck
                                 Intercity Bus
                                  Transit Bus
                                  School Bus
                                 Refuse Truck
                            Single Unit Short-haul
                             Single Unit Long-haul
                                  Motor Home
                            Combination Short-haul
                             Combination Long-haul
                                                                           2012
                                                                           8571
                                                                         128033
                                                                          86859
                                                                          21393
                                                                             18
                                                                             69
                                                                            617
                                                                            185
                                                                           6194
                                                                            260
                                                                           1559
                                                                           1191
                                                                           1280
                                                                           2013
                                                                           8687
                                                                         129764
                                                                          87924
                                                                          21791
                                                                             19
                                                                             72
                                                                            643
                                                                            195
                                                                           6525
                                                                            274
                                                                           1643
                                                                           1234
                                                                           1332
                                                                           2014
                                                                           8706
                                                                         130054
                                                                          88014
                                                                          21960
                                                                             20
                                                                             74
                                                                            663
                                                                            203
                                                                           6777
                                                                            285
                                                                           1708
                                                                           1258
                                                                           1377
                                                                           2015
                                                                           8747
                                                                         130666
                                                                          88345
                                                                          22167
                                                                             21
                                                                             77
                                                                            691
                                                                            213
                                                                           7093
                                                                            299
                                                                           1788
                                                                           1306
                                                                           1439
                                                                           2016
                                                                           8844
                                                                         132117
                                                                          89259
                                                                          22492
                                                                             22
                                                                             80
                                                                            720
                                                                            223
                                                                           7392
                                                                            312
                                                                           1863
                                                                           1354
                                                                           1503
                                                                           2017
                                                                           8943
                                                                         133583
                                                                          90198
                                                                          22803
                                                                             22
                                                                             82
                                                                            740
                                                                            230
                                                                           7589
                                                                            322
                                                                           1915
                                                                           1380
                                                                           1555
                                                                           2018
                                                                           9018
                                                                         134715
                                                                          90934
                                                                          23043
                                                                             23
                                                                             84
                                                                            753
                                                                            235
                                                                           7709
                                                                            328
                                                                           1946
                                                                           1390
                                                                           1600
                                                                           2019
                                                                           9098
                                                                         135907
                                                                          91718
                                                                          23279
                                                                             23
                                                                             86
                                                                            766
                                                                            239
                                                                           7824
                                                                            333
                                                                           1977
                                                                           1400
                                                                           1645
                                                                           2020
                                                                           9178
                                                                         137105
                                                                          92513
                                                                          23508
                                                                             23
                                                                             87
                                                                            780
                                                                            243
                                                                           7953
                                                                            335
                                                                           2012
                                                                           1410
                                                                           1690
                                                                           2021
                                                                           9260
                                                                         138317
                                                                          93324
                                                                          23730
                                                                             24
                                                                             88
                                                                            794
                                                                            247
                                                                           8093
                                                                            340
                                                                           2053
                                                                           1422
                                                                           1737
                                                                           2022
                                                                           9337
                                                                         139471
                                                                          94098
                                                                          23939
                                                                             24
                                                                             90
                                                                            809
                                                                            252
                                                                           8242
                                                                            345
                                                                           2095
                                                                           1437
                                                                           1783
                                                                           2023
                                                                           9416
                                                                         140653
                                                                          94892
                                                                          24150
                                                                             25
                                                                             92
                                                                            824
                                                                            256
                                                                           8385
                                                                            351
                                                                           2134
                                                                           1453
                                                                           1828
                                                                           2024
                                                                           9498
                                                                         141880
                                                                          95725
                                                                          24361
                                                                             25
                                                                             93
                                                                            838
                                                                            260
                                                                           8510
                                                                            352
                                                                           2168
                                                                           1466
                                                                           1872
                                                                           2025
                                                                           9585
                                                                         143179
                                                                          96598
                                                                          24591
                                                                             26
                                                                             95
                                                                            853
                                                                            264
                                                                           8638
                                                                            357
                                                                           2204
                                                                           1482
                                                                           1918
                                                                           2026
                                                                           9680
                                                                         144593
                                                                          97557
                                                                          24833
                                                                             26
                                                                             97
                                                                            867
                                                                            267
                                                                           8752
                                                                            362
                                                                           2239
                                                                           1495
                                                                           1964
                                                                           2027
                                                                           9781
                                                                         146100
                                                                          98575
                                                                          25092
                                                                             27
                                                                             98
                                                                            879
                                                                            269
                                                                           8846
                                                                            366
                                                                           2266
                                                                           1505
                                                                           2005
                                                                           2028
                                                                           9888
                                                                         147713
                                                                          99664
                                                                          25368
                                                                             27
                                                                             99
                                                                            889
                                                                            272
                                                                           8927
                                                                            371
                                                                           2288
                                                                           1514
                                                                           2040
                                                                           2029
                                                                           9996
                                                                         149317
                                                                         100741
                                                                          25649
                                                                             27
                                                                            100
                                                                            900
                                                                            274
                                                                           9017
                                                                            375
                                                                           2312
                                                                           1527
                                                                           2073
                                                                           2030
                                                                          10103
                                                                         150922
                                                                         101823
                                                                          25925
                                                                             28
                                                                            101
                                                                            912
                                                                            277
                                                                           9114
                                                                            376
                                                                           2340
                                                                           1546
                                                                           2104
                                                                           2031
                                                                          10215
                                                                         152591
                                                                         102952
                                                                          26209
                                                                             28
                                                                            103
                                                                            922
                                                                            280
                                                                           9209
                                                                            377
                                                                           2368
                                                                           1567
                                                                           2131
                                                                           2032
                                                                          10328
                                                                         154280
                                                                         104098
                                                                          26493
                                                                             28
                                                                            104
                                                                            931
                                                                            283
                                                                           9286
                                                                            381
                                                                           2385
                                                                           1585
                                                                           2152
                                                                           2033
                                                                          10439
                                                                         155930
                                                                         105216
                                                                          26772
                                                                             28
                                                                            105
                                                                            942
                                                                            286
                                                                           9378
                                                                            385
                                                                           2405
                                                                           1609
                                                                           2174
                                                                           2034
                                                                          10538
                                                                         157420
                                                                         106225
                                                                          27024
                                                                             29
                                                                            106
                                                                            956
                                                                            290
                                                                           9493
                                                                            391
                                                                           2432
                                                                           1639
                                                                           2203
                                                                           2035
                                                                          10633
                                                                         158833
                                                                         107181
                                                                          27263
                                                                             29
                                                                            108
                                                                            969
                                                                            293
                                                                           9599
                                                                            396
                                                                           2457
                                                                           1669
                                                                           2232
                                                                           2036
                                                                          10724
                                                                         160194
                                                                         108102
                                                                          27494
                                                                             30
                                                                            109
                                                                            983
                                                                            296
                                                                           9698
                                                                            401
                                                                           2482
                                                                           1701
                                                                           2260
                                                                           2037
                                                                          10813
                                                                         161523
                                                                         109001
                                                                          27720
                                                                             30
                                                                            111
                                                                            996
                                                                            299
                                                                           9795
                                                                            405
                                                                           2508
                                                                           1733
                                                                           2288
                                                                           2038
                                                                          10901
                                                                         162835
                                                                         109888
                                                                          27944
                                                                             30
                                                                            113
                                                                           1009
                                                                            301
                                                                           9887
                                                                            409
                                                                           2532
                                                                           1766
                                                                           2315
                                                                           2039
                                                                          10983
                                                                         164062
                                                                         110717
                                                                          28153
                                                                             31
                                                                            114
                                                                           1021
                                                                            304
                                                                           9968
                                                                            413
                                                                           2553
                                                                           1794
                                                                           2342
                                                                           2040
                                                                          11055
                                                                         165135
                                                                         111441
                                                                          28338
                                                                             31
                                                                            115
                                                                           1034
                                                                            306
                                                                          10051
                                                                            416
                                                                           2573
                                                                           1822
                                                                           2371
                                                                           2041
                                                                          11155
                                                                         166628
                                                                         112449
                                                                          28594
                                                                             32
                                                                            117
                                                                           1047
                                                                            309
                                                                          10147
                                                                            420
                                                                           2596
                                                                           1849
                                                                           2402
                                                                           2042
                                                                          11256
                                                                         168135
                                                                         113466
                                                                          28852
                                                                             32
                                                                            118
                                                                           1060
                                                                            312
                                                                          10243
                                                                            424
                                                                           2620
                                                                           1876
                                                                           2435
                                                                           2043
                                                                          11357
                                                                         169655
                                                                         114490
                                                                          29115
                                                                             32
                                                                            120
                                                                           1074
                                                                            315
                                                                          10342
                                                                            428
                                                                           2646
                                                                           1901
                                                                           2470
                                                                           2044
                                                                          11460
                                                                         171189
                                                                         115523
                                                                          29380
                                                                             33
                                                                            121
                                                                           1087
                                                                            318
                                                                          10442
                                                                            432
                                                                           2672
                                                                           1925
                                                                           2507
                                                                           2045
                                                                          11564
                                                                         172737
                                                                         116567
                                                                          29647
                                                                             33
                                                                            123
                                                                           1101
                                                                            321
                                                                          10543
                                                                            436
                                                                           2698
                                                                           1950
                                                                           2544
                                                                           2046
                                                                          11668
                                                                         174299
                                                                         117620
                                                                          29916
                                                                             34
                                                                            124
                                                                           1115
                                                                            324
                                                                          10646
                                                                            440
                                                                           2725
                                                                           1975
                                                                           2581
                                                                           2047
                                                                          11774
                                                                         175875
                                                                         118683
                                                                          30187
                                                                             34
                                                                            126
                                                                           1129
                                                                            328
                                                                          10749
                                                                            445
                                                                           2751
                                                                           2001
                                                                           2619
                                                                           2048
                                                                          11880
                                                                         177465
                                                                         119756
                                                                          30460
                                                                             34
                                                                            127
                                                                           1143
                                                                            331
                                                                          10853
                                                                            449
                                                                           2778
                                                                           2028
                                                                           2656
                                                                           2049
                                                                          11988
                                                                         179069
                                                                         120838
                                                                          30735
                                                                             35
                                                                            129
                                                                           1158
                                                                            334
                                                                          10958
                                                                            453
                                                                           2805
                                                                           2055
                                                                           2695
                                                                           2050
                                                                          12096
                                                                         180688
                                                                         121931
                                                                          31013
                                                                             35
                                                                            131
                                                                           1172
                                                                            337
                                                                          11064
                                                                            458
                                                                           2832
                                                                           2083
                                                                           2733

Appendix B: Fuel Type and Regulatory Class Fractions for 1960-1981
As noted in the text, all the fuel type and regulatory class distributions in the SampleVehiclePopulation table for model year 1981 and earlier have not changed from MOVES2010b. Those fuel type distributions between 1960 and 1981 for each source type have been summarized in Table 18-1 and Table 18-2. Many of the data sources for the fuel type fractions are the same in MOVES2010b and MOVES2014. Truck diesel fractions in Table 18-1 are derived using a MOVES2010b sample vehicle counts dataset -- similar to the MOVES2014 one -- but with 1999 Polk vehicle registrations and the 1997 VIUS, except for refuse trucks and motor homes. We assumed 96 percent of refuse trucks were manufactured to run on diesel fuel in 1980 and earlier according to the average diesel fraction from VIUS across all model years. We also assumed that 15 percent of motor homes are diesel powered based on information from the Recreation Vehicle Industry Association (RVIA), as noted above in Section 6.2.2.5. 

                    Table 18-1 Diesel Fractions for Trucks*
                                       
                                       
                                  Source Type
                                  Model Year
                                       
                               Passenger Trucks
                                     (31)
                            Light Commercial Trucks
                                     (32)
                                 Refuse Trucks
                                     (51)
                              Single Unit Trucks
                                 (52 & 53)
                               Motor Homes (54)
                         Short-haul Combination Trucks
                                     (61)
                         Long-haul Combination Trucks
                                     (62)
                                  1960-1979 
                                    0.0139
                                    0.0419
                                     0.96
                                    0.2655
                                     0.15
                                    0.9146
                                    1.0000
                                     1980
                                    0.0124
                                    0.1069
                                     0.96
                                    0.2950
                                     0.15
                                    0.9146
                                    1.0000
                                     1981
                                    0.0178
                                    0.0706
                                     0.96
                                    0.3245
                                     0.15
                                    0.9146
                                    1.0000
* All other trucks are assumed to be gasoline powered

Like in MOVES2010b, lacking both emission rate and population data we assume in MOVES2014 that all motorcycles will be gasoline powered, all intercity buses will be diesel powered over all model years, and all transit buses will be run on diesel from 1960 to 1981. School bus fuel type fractions are reused from MOBILE6, originally based on 1996 and 1997 Polk data. Passenger cars are split between gasoline and diesel for 1960-1981 using the MOVES2010b sample vehicle counts dataset.

            Table 18-2 Diesel Fractions for Non-truck Source Types*

                                  Source Type
                                  Model Year
Motorcycles
                                     (11)
                                Passenger Cars
                                     (21)
                                Intercity Buses
                                     (41)
                                 Transit Buses
                                     (42)
                               School Buses (43)
                                  1960-1974 
                                       0
                                    0.0069
                                     1.000
                                     1.000
                                    0.0087
                                     1975
                                       0
                                    0.0180
                                     1.000
                                     1.000
                                    0.0087
                                     1976
                                       0
                                    0.0165
                                     1.000
                                     1.000
                                    0.0086
                                     1977
                                       0
                                    0.0129
                                     1.000
                                     1.000
                                    0.0240
                                     1978
                                       0
                                    0.0151
                                     1.000
                                     1.000
                                    0.0291
                                     1979
                                       0
                                    0.0312
                                     1.000
                                     1.000
                                    0.0460
                                     1980
                                       0
                                    0.0467
                                     1.000
                                     1.000
                                    0.0594
                                     1981
                                       0
                                    0.0764
                                     1.000
                                     1.000
                                    0.2639
            * All other vehicles are assumed to be gasoline powered

The 1960-1981 regulatory class distributions are difficult to represent succinctly, but they have been derived from the MOVES2010b sample vehicle counts dataset as well, with a few exceptions. Motorcycles (sourceTypeID 11 and regClassID 10) and passenger cars (sourceTypeID 21 and regClassID 20) have one-to-one relationships between source types and regulatory classes for all model years for both MOVES2010b and MOVES2014. Passenger trucks (sourceTypeID 31) and light commercial trucks (sourceTypeID 32) are split between fuel type and regulatory class (regClassID 30 and 40) as shown in Table 18-3.

Table 18-3 Percentage by regulatory class and fuel type for passenger trucks (sourceTypeID 31) and light commercial truck (sourceTypeID 32)

                             Passenger Trucks (31)
                         Light Commercial Trucks (32)

                                   Gasoline
                                    Diesel
                                   Gasoline
                                    Diesel
                                  Model Year
                                   LDT (30)
                                      LHD
                                     (40)
                                   LDT (30)
                                      LHD
                                     (40)
                                   LDT (30)
                                      LHD
                                     (40)
                                   LDT (30)
                                      LHD
                                     (40)
                                   1960-1966
                                      81%
                                      19%
                                      38%
                                      62%
                                      24%
                                      76%
                                      7%
                                      93%
                                     1967
                                      90%
                                      10%
                                      38%
                                      62%
                                      72%
                                      28%
                                      7%
                                      93%
                                     1968
                                      88%
                                      12%
                                      38%
                                      62%
                                      67%
                                      33%
                                      7%
                                      93%
                                     1969
                                     100%
                                      0%
                                      38%
                                      62%
                                      91%
                                      9%
                                      7%
                                      93%
                                     1970
                                      99%
                                      1%
                                      38%
                                      62%
                                      80%
                                      20%
                                      7%
                                      93%
                                     1971
                                      96%
                                      3%
                                      38%
                                      62%
                                      94%
                                      6%
                                      7%
                                      93%
                                     1972
                                      96%
                                      4%
                                      38%
                                      62%
                                      75%
                                      25%
                                      7%
                                      93%
                                     1973
                                      95%
                                      5%
                                      38%
                                      62%
                                      59%
                                      41%
                                      7%
                                      93%
                                     1974
                                      95%
                                      5%
                                      38%
                                      62%
                                      65%
                                      35%
                                      7%
                                      93%
                                     1975
                                      97%
                                      3%
                                      38%
                                      62%
                                      72%
                                      28%
                                      7%
                                      93%
                                     1976
                                      95%
                                      5%
                                      38%
                                      62%
                                      88%
                                      12%
                                      7%
                                      93%
                                     1977
                                      89%
                                      11%
                                      38%
                                      62%
                                      79%
                                      21%
                                      7%
                                      93%
                                     1978
                                      85%
                                      15%
                                      38%
                                      62%
                                      81%
                                      19%
                                      7%
                                      93%
                                     1979
                                      87%
                                      13%
                                      38%
                                      62%
                                      78%
                                      22%
                                      7%
                                      93%
                                     1980
                                      90%
                                      10%
                                      38%
                                      62%
                                      74%
                                      26%
                                      40%
                                      60%
                                     1981
                                      96%
                                      4%
                                      38%
                                      62%
                                      89%
                                      11%
                                      12%
                                      88%

The bus and motor home source types each have a single regulatory class distribution for all model years, as described in Section 1.1.1. The 1960-1981 regulatory class distributions for diesel-fueled single unit and combination trucks have been summarized in Table 18-4 below. All 1960-1981 gasoline-fueled single unit and combination trucks fall into the medium heavy-duty (MHD) regulatory class (regClassID 46).

Table 18-4 Percentage of MHD Trucks (regClassID 46) among Diesel-fueled Single Unit and Combination Trucks*
                                       
                                  Source Type
                                  Model Year
                                 Refuse Trucks
                                     (51)
                              Single Unit Trucks
                                  (52&53)
                            Short-haul Comb. Trucks
                                     (61)
                            Long-haul Comb. Trucks
                                     (62)
                                   1960-1972
                                     100%
                                      0%
                                      0%
                                      0%
                                     1973
                                     100%
                                      3%
                                      8%
                                      0%
                                     1974
                                      0%
                                      6%
                                      30%
                                      0%
                                     1975
                                      0%
                                      14%
                                      3%
                                      0%
                                     1976
                                      0%
                                      44%
                                      13%
                                      0%
                                     1977
                                      0%
                                      43%
                                      31%
                                      0%
                                     1978
                                      0%
                                      36%
                                      18%
                                      0%
                                     1979
                                      0%
                                      34%
                                      16%
                                      0%
                                     1980
                                      0%
                                      58%
                                      29%
                                      5%
                                     1981
                                      0%
                                      47%
                                      31%
                                      6%
    *For these source types, all remaining trucks are in the HHD regulatory class (regClassID 47).

Appendix C: 1990 Age Distributions
Motorcycles
The motorcycle age distributions are based on Motorcycle Industry Council estimates of the number of motorcycles in use, by model year, in 1990. However, data for individual model years starting from 1978 and earlier were not available. A logarithmic regression curve (R[2] value = 0.82) was fitted to available data, which was then used to extrapolate age fractions for earlier years beginning in 1978.
Passenger Cars
To determine the 1990 age fractions for passenger cars, we began with Polk NVPP(R) 1990 data on car registration by model year. However, this data presents a snapshot of registrations on July 1, 1990, and we needed age fractions as of December 31, 1990. To adjust the values, we used monthly data from the Polk new car database to estimate the number of new cars registered in the months July through December 1990. Model Year 1989 cars were added to the previous estimate of "Age 1" cars and Model Year 1990 and 1991 cars were added to the "Age 0" cars. Also the 1990 data did not detail model year for ages 15+. Hence, regression estimates were used to extrapolate the age fractions for individual ages 15+ based on an exponential curve (R[2] value =0.67) fitted to available data.
Trucks
For the 1990 age fractions for passenger trucks, light commercial trucks, refuse trucks, short-haul and long-haul single unit trucks and short-haul and long-haul combination trucks, we used data from the TIUS92 (1992 Truck Inventory and Use Survey) database. Vehicles in the TIUS92 database were assigned to MOVES source types as summarized in Table 19-118-118-117-1. Like VIUS97, TIUS92 does not include a model year field and records ages as 0 through 10 and 11-and-greater. Because we needed greater detail on the older vehicles, we followed the practice used for the 1999 fractions and determined the model year for some of the older vehicles by using the responses to the questions "How was the vehicle obtained?" (TIUS field "OBTAIN") and "When did you obtain this vehicle?" (TIUS field "ACQYR") and we adjusted the age-11-and-older vehicle counts by dividing the original count by model year by the fraction of the older vehicles that were coded as "obtained new."

     Table 19-1 VIUS 1997 Codes Used for Distinguishing Truck Source Types
Source Type	
Axle Arrangement
Primary Area of Operation
Body Type
Major Use
Passenger Trucks
2 axle/4 tire (AXLRE= 1,5,6,7)
Any
Any
personal transportation (MAJUSE=20)
Light Commercial Trucks
2 axle/4 tire (AXLRE= 1,5,6,7)
Any
Any
any but personal transportation
Refuse Trucks
Single Unit (AXLRE=2-4,
8-16)
Off-road, local or short-range (AREAOP <=4)
Garbage hauler (BODTYPE=30)
Any
Single Unit Short-haul Trucks
Single Unit (AXLRE=2-4,
8-16)
Off-road, local or short-range (AREAOP<=4)
Any except garbage hauler
Any
Single Unit Long-haul Trucks
Single Unit (AXLRE=2-4,
8-16)
Long-range (AREAOP>=5)
Any
Any
Combination Short-haul Trucks
Combination (AXLRE>=17)
Off-road, local or medium (AREAOP<=4)
Any
Any
Combination Long-haul Trucks
Combination (AXLRE>=17)
Long-range (AREAOP>=5)
Any
Any

Intercity Buses
For 1990, we were not able to identify a data source for estimating age distributions of intercity buses. Because the purchase and retirement of these buses is likely to be driven by general economic forces rather than trends in government spending, we will use the1990 age distributions that were derived for short-haul combination trucks, as described above.
School Buses and Motor Homes
To determine the age fractions of School Buses and Motor Homes, we used information from the Polk TIP(R) 1999 database. School Bus and Motor Home counts were available by model year. Unlike the Polk data for passenger cars, these counts reflect registration at the end of the calendar year and, thus, did not require adjustment. We converted model year to age and calculated age fractions. Because we did not have access to 1990 data, these fractions were used for 1990.
Transit Buses
For 1990 Transit Bus age distributions, we used the MOBILE 6 age fractions since 1990 data on transit buses was not available from the Federal Transit Administration database. MOBILE 6 age fractions were based on fitting curves through a snapshot of vehicle registration data as of July 1, 1996, which was purchased from R.L. Polk Company. To develop a general curve, the 1996 model year vehicle populations were removed from the sample because it did not represent a full year, and a best fit analysis was performed on the remaining population data. The best fit analyses resulted in age distribution estimates for vehicles ages 1 through 25+. However, since the vehicle sales year begins in October, the estimated age 1 population was multiplied by 0.75 to account for the fact that approximately 75% of the year's sales will have occurred by July 1[st] of a given calendar year.
Both Weibull curve fitting and exponential curve fitting were used to create the age distributions. The nature of the Weibull curve fitting formula is to produce an "S" shaped curve, which is relatively flat for the first third of the data, decreases rapidly for the next third, and flattens again for the final third. While using this formula resulted in a better overall fit for transit buses, the flatness of the final third for each curve resulted in unrealistically low vehicle populations for the older vehicle ages. For this reason, the original Weibull curve was used where it fit best, and exponential curves were fit through the data at the age where the Weibull curves began to flatten. Table 19-2 presents the equations used to create the age distribution and the years in which the equations were used.

      Table 19-2 Curve Fit Equations for Registration Distribution by Age
                                  Vehicle Age
                                   Equation
                                     1-17
                      y=3462*e-age17.1690947512.53214119
                                    18-25+
                            24987.0776*e-0.2000*age

Appendix D: Driving Schedules and SCC Mappings
SCC Mappings
The Source Classification Code (SCC) used before MOVES2014 do not cleanly map to the source types used by MOVES.  In the 10-digit SCC, the first seven digits (SCC7) indicate the vehicle classification. The SCC vehicle classifications were mapped to the source types used by MOVES by calculating the fraction VMT for each source type found in each SCC classification result in a national MOVES2010b run for calendar year 2011.  The factors calculated from the MOVES201b run are shown in .  
                                       
Table 20-1 Mapping of Previous SCC Vehicle Classifications to MOVES Source Types for Calculation of Road Type Distributions
                                      SCC
                                  (7 digits)
Description
                                  Source Type
Description
                                2011 Fractions
                                    2201001
Gasoline Light-Duty Vehicles (Passenger Cars)
                                      21
 Passenger Car
                                                                       1.000000
                                    2201020
Gasoline Light-Duty Trucks (0-6,000 lbs. GVWR)
                                      31
 Passenger Truck
                                                                       0.779270
                                    2201020
Gasoline Light-Duty Trucks (0-6,000 lbs. GVWR)
                                      32
 Light Commercial Truck
                                                                       0.220730
                                    2201040
Gasoline Light-Duty Trucks (6,001-8,500 lbs. GVWR)
                                      31
 Passenger Truck
                                                                       0.779269
                                    2201040
Gasoline Light-Duty Trucks (6,001-8,500 lbs. GVWR)
                                      32
 Light Commercial Truck
                                                                       0.220731
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      31
 Passenger Truck
                                                                       0.450274
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      32
 Light Commercial Truck
                                                                       0.267803
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      42
 Transit Bus
                                                                       0.000664
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      43
 School Bus
                                                                       0.002476
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      51
 Refuse Truck
                                                                       0.000509
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      52
 Single Unit Short-haul Truck
                                                                       0.221958
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      53
 Single Unit Long-haul Truck
                                                                       0.030154
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      54
 Motor Home
                                                                       0.025802
                                    2201070
Gasoline Heavy-Duty Gasoline Vehicles (8501 lbs. and greater GVWR)
                                      61
 Combination Short-haul Truck
                                                                       0.000359
                                    2201080
Gasoline Motorcycles
                                      11
 Motorcycle
                                                                       1.000000
                                    2230001
Diesel Light-Duty Vehicles (Passenger Cars)
                                      21
 Passenger Car
                                                                       1.000000
                                    2230060
Diesel Light-Duty Trucks (0-8,500 lbs. GVWR)
                                      31
 Passenger Truck
                                                                       0.343599
                                    2230060
Diesel Light-Duty Trucks (0-8,500 lbs. GVWR)
                                      32
 Light Commercial Truck
                                                                       0.656401
                                    2230071
Diesel Class 2b Heavy-Duty Vehicles (8501-10,000 lbs. GVWR)
                                      31
 Passenger Truck
                                                                       0.364691
                                    2230071
Diesel Class 2b Heavy-Duty Vehicles (8501-10,000 lbs. GVWR)
                                      32
 Light Commercial Truck
                                                                       0.635309
                                    2230072
Diesel Class 3, 4 & 5 Heavy-Duty Vehicles (10,001-19,500 lbs. GVWR)
                                      31
 Passenger Truck
                                                                       0.305092
                                    2230072
Diesel Class 3, 4 & 5 Heavy-Duty Vehicles (10,001-19,500 lbs. GVWR)
                                      32
 Light Commercial Truck
                                                                       0.694908
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      51
 Refuse Truck
                                                                       0.001726
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      52
 Single Unit Short-haul Truck
                                                                       0.623978
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      53
 Single Unit Long-haul Truck
                                                                       0.086570
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      54
 Motor Home
                                                                       0.025294
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      61
 Combination Short-haul Truck
                                                                       0.194650
                                    2230073
Diesel Class 6 & 7 Heavy-Duty Vehicles (19,501-33,000 lbs. GVWR)
                                      62
 Combination Long-haul Truck
                                                                       0.067783
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      51
 Refuse Truck
                                                                       0.008531
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      52
 Single Unit Short-haul Truck
                                                                       0.100296
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      53
 Single Unit Long-haul Truck
                                                                       0.013800
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      54
 Motor Home
                                                                       0.000328
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      61
 Combination Short-haul Truck
                                                                       0.323425
                                    2230074
Diesel Class 8a & 8b Heavy-Duty Vehicles (33,001 lbs. and greater GVWR)
                                      62
 Combination Long-haul Truck
                                                                       0.553619
                                    2230075
Diesel Buses
                                      41
 Intercity Bus
                                                                       0.430859
                                    2230075
Diesel Buses
                                      42
 Transit Bus
                                                                       0.122565
                                    2230075
Diesel Buses
                                      43
 School Bus
                                                                       0.446576

Driving Schedules
A key feature of MOVES is the capability to accommodate a number of drive schedules to represent driving patterns across source type, roadway type and average speed. For the national default case, MOVES2014 employs 49 drive schedules with various average speeds, mapped to specific source types and roadway types. 

T19-3 below lists the driving schedules used in MOVES2014.   Some driving schedules are used for both restricted access (freeway) and unrestricted access (non-freeway) driving.  Some driving schedules are used for multiple source types or multiple road types where vehicle specific information was not available.

           Table 20-2 MOVES2014 Default Driving Schedule Statistics
                               drive schedule id
                              drive schedule name
                                   avg speed
                                   max speed
                                idle time (sec)
                            percent of time idling
                                     miles
                                  time (sec)
                                    minutes
                                     hours
                                                                            101
 LD Low Speed 1
                                                                            2.5
                                                                          10.00
                                                                            280
                                                                          46.5%
                                                                          0.419
                                                                         602.00
                                                                          10.03
                                                                          0.167
                                                                            153
 LD LOS E Freeway
                                                                           30.5
                                                                          63.00
                                                                              5
                                                                           1.1%
                                                                          3.863
                                                                         456.00
                                                                           7.60
                                                                          0.127
                                                                            158
 LD High Speed Freeway 3
                                                                           76.0
                                                                          90.00
                                                                              0
                                                                           0.0%
                                                                         12.264
                                                                         581.00
                                                                           9.68
                                                                          0.161
                                                                            201
 MD 5mph Non-Freeway
                                                                            4.6
                                                                          24.10
                                                                             85
                                                                          29.0%
                                                                          0.373
                                                                         293.00
                                                                           4.88
                                                                          0.081
                                                                            202
 MD 10mph Non-Freeway
                                                                           10.7
                                                                          34.10
                                                                             61
                                                                          19.6%
                                                                          0.928
                                                                         311.00
                                                                           5.18
                                                                          0.086
                                                                            203
 MD 15mph Non-Freeway
                                                                           15.6
                                                                          36.60
                                                                             57
                                                                          12.6%
                                                                          1.973
                                                                         454.00
                                                                           7.57
                                                                          0.126
                                                                            204
 MD 20mph Non-Freeway
                                                                           20.8
                                                                          44.50
                                                                             95
                                                                           9.1%
                                                                          6.054
                                                                        1046.00
                                                                          17.43
                                                                          0.291
                                                                            205
 MD 25mph Non-Freeway
                                                                           24.5
                                                                          47.50
                                                                             63
                                                                          11.1%
                                                                          3.846
                                                                         566.00
                                                                           9.43
                                                                          0.157
                                                                            206
 MD 30mph Non-Freeway
                                                                           31.5
                                                                          55.90
                                                                             54
                                                                           5.5%
                                                                          8.644
                                                                         988.00
                                                                          16.47
                                                                          0.274
                                                                            251
 MD 30mph Freeway
                                                                           34.4
                                                                          62.60
                                                                              0
                                                                           0.0%
                                                                         15.633
                                                                        1637.00
                                                                          27.28
                                                                          0.455
                                                                            252
 MD 40mph Freeway
                                                                           44.5
                                                                          70.40
                                                                              0
                                                                           0.0%
                                                                         43.329
                                                                        3504.00
                                                                          58.40
                                                                          0.973
                                                                            253
 MD 50mph Freeway
                                                                           55.4
                                                                          72.20
                                                                              0
                                                                           0.0%
                                                                         41.848
                                                                        2718.00
                                                                          45.30
                                                                          0.755
                                                                            254
 MD 60mph Freeway
                                                                           60.1
                                                                          68.40
                                                                              0
                                                                           0.0%
                                                                         81.299
                                                                        4866.00
                                                                          81.10
                                                                          1.352
                                                                            255
 MD High Speed Freeway
                                                                           72.8
                                                                          80.40
                                                                              0
                                                                           0.0%
                                                                         96.721
                                                                        4782.00
                                                                          79.70
                                                                          1.328
                                                                            301
 HD 5mph Non-Freeway
                                                                            5.8
                                                                          19.90
                                                                             37
                                                                          14.2%
                                                                          0.419
                                                                         260.00
                                                                           4.33
                                                                          0.072
                                                                            302
 HD 10mph Non-Freeway
                                                                           11.2
                                                                          29.20
                                                                             70
                                                                          11.5%
                                                                          1.892
                                                                         608.00
                                                                          10.13
                                                                          0.169
                                                                            303
 HD 15mph Non-Freeway
                                                                           15.6
                                                                          38.30
                                                                             73
                                                                          12.9%
                                                                          2.463
                                                                         567.00
                                                                           9.45
                                                                          0.158
                                                                            304
 HD 20mph Non-Freeway
                                                                           19.4
                                                                          44.20
                                                                             84
                                                                          15.1%
                                                                          3.012
                                                                         558.00
                                                                           9.30
                                                                          0.155
                                                                            305
 HD 25mph Non-Freeway
                                                                           25.6
                                                                          50.70
                                                                             57
                                                                           5.8%
                                                                          6.996
                                                                         983.00
                                                                          16.38
                                                                          0.273
                                                                            306
 HD 30mph Non-Freeway
                                                                           32.5
                                                                          58.00
                                                                             43
                                                                           5.3%
                                                                          7.296
                                                                         809.00
                                                                          13.48
                                                                          0.225
                                                                            351
 HD 30mph Freeway
                                                                           34.3
                                                                          62.70
                                                                              0
                                                                           0.0%
                                                                         21.659
                                                                        2276.00
                                                                          37.93
                                                                          0.632
                                                                            352
 HD 40mph Freeway
                                                                           47.1
                                                                          65.00
                                                                              0
                                                                           0.0%
                                                                         41.845
                                                                        3197.00
                                                                          53.28
                                                                          0.888
                                                                            353
 HD 50mph Freeway
                                                                           54.2
                                                                          68.00
                                                                              0
                                                                           0.0%
                                                                         80.268
                                                                        5333.00
                                                                          88.88
                                                                          1.481
                                                                            354
 HD 60mph Freeway
                                                                           59.7
                                                                          69.00
                                                                              0
                                                                           0.0%
                                                                         29.708
                                                                        1792.00
                                                                          29.87
                                                                          0.498
                                                                            355
 HD High Speed Freeway
                                                                           71.7
                                                                          81.00
                                                                              0
                                                                           0.0%
                                                                         35.681
                                                                        1792.00
                                                                          29.87
                                                                          0.498
                                                                            396
 HD High Speed Freeway Plus 5 mph
                                                                           76.7
                                                                          86.00
                                                                              0
                                                                           0.0%
                                                                         38.170
                                                                        1792.00
                                                                          29.87
                                                                          0.498
                                                                            397
 MD High Speed Freeway Plus 5 mph
                                                                           77.8
                                                                          85.40
                                                                              0
                                                                           0.0%
                                                                        103.363
                                                                        4782.00
                                                                          79.70
                                                                          1.328
                                                                            398
 CRC E55 HHDDT Creep
                                                                            1.8
                                                                           8.24
                                                                            107
                                                                          42.3%
                                                                          0.124
                                                                         253.00
                                                                           4.22
                                                                          0.070
                                                                            401
 Bus Low Speed Urban (nominal 15 mph)
                                                                            3.1
                                                                          19.80
                                                                            288
                                                                          63.9%
                                                                          0.393
                                                                         451.00
                                                                           7.52
                                                                          0.125
                                                                            402
 Bus 30 mph Flow (nominal 30 mph)
                                                                           11.5
                                                                          33.80
                                                                            109
                                                                          37.5%
                                                                          0.932
                                                                         291.00
                                                                           4.85
                                                                          0.081
                                                                            403
 Bus 45 mph Flow (nominal 45 mph)
                                                                           21.9
                                                                          47.00
                                                                            116
                                                                          28.3%
                                                                          2.492
                                                                         410.00
                                                                           6.83
                                                                          0.114
                                                                            404
 New York City Bus
                                                                            3.7
                                                                          30.80
                                                                            403
                                                                          67.2%
                                                                          0.615
                                                                         600.00
                                                                          10.00
                                                                          0.167
                                                                            405
 WMATA Transit Bus
                                                                            8.3
                                                                          47.50
                                                                            706
                                                                          38.4%
                                                                          4.261
                                                                        1840.00
                                                                          30.67
                                                                          0.511
                                                                            501
 Refuse Truck Urban
                                                                            2.2
                                                                          20.00
                                                                            416
                                                                          66.9%
                                                                          0.374
                                                                         622.00
                                                                          10.37
                                                                          0.173
                                                                           1009
 Final FC01LOSAF Cycle (C10R04-00854)
                                                                           73.8
                                                                          84.43
                                                                              0
                                                                           0.0%
                                                                         11.664
                                                                         569.00
                                                                           9.48
                                                                          0.158
                                                                           1011
 Final FC02LOSDF Cycle (C10R05-00513)
                                                                           49.1
                                                                          73.06
                                                                             34
                                                                           5.0%
                                                                          9.283
                                                                         681.00
                                                                          11.35
                                                                          0.189
                                                                           1017
 Final FC11LOSB Cycle (C10R02-00546)
                                                                           66.4
                                                                          81.84
                                                                              0
                                                                           0.0%
                                                                          9.567
                                                                         519.00
                                                                           8.65
                                                                          0.144
                                                                           1018
 Final FC11LOSC Cycle (C15R09-00849)
                                                                           64.4
                                                                          78.19
                                                                              0
                                                                           0.0%
                                                                         16.189
                                                                         905.00
                                                                          15.08
                                                                          0.251
                                                                           1019
 Final FC11LOSD Cycle (C15R10-00068)
                                                                           58.8
                                                                          76.78
                                                                              0
                                                                           0.0%
                                                                         11.922
                                                                         730.00
                                                                          12.17
                                                                          0.203
                                                                           1020
 Final FC11LOSE Cycle (C15R11-00851)
                                                                           46.1
                                                                          71.50
                                                                              1
                                                                           0.1%
                                                                         12.468
                                                                         973.00
                                                                          16.22
                                                                          0.270
                                                                           1021
 Final FC11LOSF Cycle (C15R01-00876)
                                                                           20.6
                                                                          55.48
                                                                             23
                                                                           2.5%
                                                                          5.179
                                                                         905.00
                                                                          15.08
                                                                          0.251
                                                                           1024
 Final FC12LOSC Cycle (C15R04-00582)
                                                                           63.7
                                                                          79.39
                                                                              0
                                                                           0.0%
                                                                         15.685
                                                                         887.00
                                                                          14.78
                                                                          0.246
                                                                           1025
 Final FC12LOSD Cycle (C15R09-00037)
                                                                           52.8
                                                                          73.15
                                                                             12
                                                                           1.5%
                                                                         11.754
                                                                         801.00
                                                                          13.35
                                                                          0.223
                                                                           1026
 Final FC12LOSE Cycle (C15R10-00782)
                                                                           43.3
                                                                          70.87
                                                                              0
                                                                           0.0%
                                                                         10.973
                                                                         913.00
                                                                          15.22
                                                                          0.254
                                                                           1029
 Final FC14LOSB Cycle (C15R07-00177)
                                                                           31.0
                                                                          63.81
                                                                             27
                                                                           3.6%
                                                                          6.498
                                                                         754.00
                                                                          12.57
                                                                          0.209
                                                                           1030
 Final FC14LOSC Cycle (C10R04-00104)
                                                                           25.4
                                                                          53.09
                                                                             41
                                                                           8.0%
                                                                          3.617
                                                                         513.00
                                                                           8.55
                                                                          0.143
                                                                           1033
 Final FC14LOSF Cycle (C15R05-00424)
                                                                            8.7
                                                                          44.16
                                                                            326
                                                                          38.2%
                                                                          2.066
                                                                         853.00
                                                                          14.22
                                                                          0.237
                                                                           1041
 Final FC17LOSD Cycle (C15R05-00480)
                                                                           18.6
                                                                          50.33
                                                                            114
                                                                          16.1%
                                                                          3.659
                                                                         709.00
                                                                          11.82
                                                                          0.197
                                                                           1043
 Final FC19LOSAC Cycle (C15R08-00267)
                                                                           15.7
                                                                          37.95
                                                                             67
                                                                           7.7%
                                                                          3.802
                                                                         870.00
                                                                          14.50
                                                                          0.242

Appendix E: MOVES2010b Source Masses
Light-duty source masses were unchanged from MOVES2010b. In addition, the heavy-duty source masses originally come from MOVES2010b, although they have been updated as described in Section 14.1. 

In MOVES2010b, weight data (among other kinds of information) were used to allocate source types to source bins using a field called weightClassID. Each source type's source mass was calculated using an activity-weighted average of their associated source bins' midpoint weights:
                                       
                           M= afa∙bαb∙mbαbafa
                                                                    Equation 40
where M is the source mass factor for the source type, fa is the age fraction at age a, αb is the source bin activity fraction for source bin b, and m is the vehicle midpoint mass. Table 19-1 lists the vehicle midpoint mass for each weightClassID. The source bin activity fraction in MOVES2010b is a calculated value of activity based on fuel type, engine technology, regulatory class, model year, engine size, and weight class. This calculation is outside the scope of this document, but more information can be found in the MOVES2010b SDRM. 

                        Table 21-1 MOVES Weight Classes
                                 WeightClassID
                               Weight Class Name
                                Midpoint Weight
                                                                              0
                                Doesn't Matter
     [NULL] 
                                                                             20
                            weight < 2000 pounds
                                                                           1000
                                                                             25
                   2000 pounds <= weight < 2500 pounds
                                                                           2250
                                                                             30
                   2500 pounds <= weight < 3000 pounds
                                                                           2750
                                                                             35
                   3000 pounds <= weight < 3500 pounds
                                                                           3250
                                                                             40
                   3500 pounds <= weight < 4000 pounds
                                                                           3750
                                                                             45
                   4000 pounds <= weight < 4500 pounds
                                                                           4250
                                                                             50
                   4500 pounds <= weight < 5000 pounds
                                                                           4750
                                                                             60
                   5000 pounds <= weight < 6000 pounds
                                                                           5500
                                                                             70
                   6000 pounds <= weight < 7000 pounds
                                                                           6500
                                                                             80
                   7000 pounds <= weight < 8000 pounds
                                                                           7500
                                                                             90
                   8000 pounds <= weight < 9000 pounds
                                                                           8500
                                                                            100
                  9000 pounds <= weight < 10000 pounds
                                                                           9500
                                                                            140
                  10000 pounds <= weight < 14000 pounds
                                                                          12000
                                                                            160
                  14000 pounds <= weight < 16000 pounds
                                                                          15000
                                                                            195
                  16000 pounds <= weight < 19500 pounds
                                                                          17750
                                                                            260
                  19500 pounds <= weight < 26000 pounds
                                                                          22750
                                                                            330
                  26000 pounds <= weight < 33000 pounds
                                                                          29500
                                                                            400
                  33000 pounds <= weight < 40000 pounds
                                                                          36500
                                                                            500
                  40000 pounds <= weight < 50000 pounds
                                                                          45000
                                                                            600
                  50000 pounds <= weight < 60000 pounds
                                                                          55000
                                                                            800
                  60000 pounds <= weight < 80000 pounds
                                                                          70000
                                                                           1000
                 80000 pounds <= weight < 100000 pounds
                                                                          90000
                                                                           1300
                 100000 pounds <= weight < 130000 pounds
                                                                         115000
                                                                           9999
                          130000 pounds <= weight
                                                                         130000
                                                                              5
                       weight < 500 pounds (for MCs)
                                                                            350
                                                                              7
               500 pounds <= weight < 700 pounds (for MCs)
                                                                            600
                                                                              9
                       700 pounds <= weight (for MCs)
                                                                            700

The following sections detail how weight classes were assigned to the various source types in MOVES.
Motorcycles
The Motorcycle Industry Council "Statistical Annual" provides information on displacement distributions for highway motorcycles for model years 1990 and 1998. These were mapped to MOVES engine displacement categories.  Additional EPA certification data was used to establish displacement distributions for model year 2000.  We assumed that displacement distributions were the same in 1969 as in 1990, and interpolated between the established values to determine displacement distributions for all model years from 1990 to 1997 and for 1999. Values for 2000-and-later model years are based on model year 2000 certification data.

We then applied weight distributions for each displacement category as suggested by EPA motorcycle experts. The average weight estimate includes fuel and rider. The weight distributions depended on engine displacement but were otherwise independent of model year. This information is summarized in Table 19-2.

Table 21-2 Motorcycle Engine Size and Average Weight Distributions for Selected Model Years
                             Displacement Category
                        1969 MY distribution (assumed)
                          1990 MY distribution (MIC)
                          1998 MY distribution (MIC)
                                    2000 MY
                                 distribution
                             (certification data)
                        Weight distribution (EPA staff)
0-169 cc (1)
                                                                          0.118
                                                                          0.118
                                                                          0.042
                                                                          0.029
100%:  <= 500 lbs
170-279 cc (2)
                                                                           0.09
                                                                           0.09
                                                                           0.05
                                                                          0.043
50%:   <= 500 lbs
50%:  500lbs -700lbs  
280+ cc (9)
                                                                          0.792
                                                                          0.792
                                                                          0.908
                                                                          0.928
30%:  500 lbs-700 lbs
70%:   > 700lbs

Passenger Cars
Passenger car weights come from Polk. The weightClassID was assigned by adding 300 lbs to the Polk curb weight and grouping into MOVES weight bins.  For each fuel type, model year, engine size, and weight bin, the number of cars was summed and fractions were computed. In general, entries for which data was missing were omitted from the calculations. Also, analysis indicated a likely error in the Polk data (an entry for 1997 gasoline-powered Bentleys with engine size 5099 and weight class 20). This fraction was removed and the 1997 values were renormalized. 1999 model year values were used for all 2000-and-later model years.

General Trucks
Light-Duty Trucks
Determining weight categories for light trucks was fairly complicated.  The VIUS 1997 data combines information from two different survey forms.  The first form was administered for VIUS "Strata" 1 and 2 trucks: pickup trucks, panel trucks, vans (including mini-vans), utility type vehicles (including jeeps) and station wagons on truck chassis. The second form was administered for all other trucks.  While both surveys requested information on engine size, only the second form requested detailed information on vehicle weight.  Thus for Strata 1 and 2 trucks, VIUS classifies the trucks only by broad average weight category (AVGCK): 6,000 lbs or less, 6,001-10,000 lbs, 10,001-14,000lbs, etc. To determine a more detailed average engine size and weight distribution for these vehicles, we used an Oak Ridge National Laboratory (ORNL) light-duty vehicle database, compiled from EPA test vehicle data and Ward's Automotive Inc. data, to correlate engine size with vehicle weight distributions by model year.

In particular, for source types 31 and 32 (Passenger Trucks and Light Commercial Trucks):
   VIUS 1997 trucks of the source type in Strata 3, 4, and 5 were assigned to the appropriate MOVES weight class based on VIUS detailed average weight information.
   VIUS 1997 trucks of the source type in Strata 1 and 2 were identified by engine size and broad average weight category.
   Strata 1 and 2 trucks in the heavier (10,001-14,000 lbs, etc) VIUS 1997 broad categories were matched one-to-one with the MOVES weight classes.
   For trucks in the lower broad categories (6,000 lbs or less and 6001-10,000 lbs), we used VIUS 1997 to determine the fraction of trucks by model year and fuel type that fell into each engine size/broad weight class combination (the "VIUS fraction")
   We assigned trucks in the ORNL light-duty vehicle database to a weightClassID by adding 300lbs to the recorded curb weight and determining the appropriate MOVES weight class.
   For the trucks with a VIUS 1997 average weight of 6,000 lbs or less, we multiplied the VIUS 1997 fraction by the fraction of trucks with a given weightClassID among the trucks in the ORNL database that had the given engine size and an average weight of 6,000 lbs or less.  Note, the ORNL database did not provide information on fuel type, so the same distributions were used for all fuels.
   Because the ORNL database included only vehicles with a GVW up to 8500 lbs, we did not use it to distribute the trucks with a VIUS 1997 average weight of 6,001-10,000 lbs. Instead these were distributed equally among the MOVES weightClassID 70, 80, 90 and 100. 
          
Single Unit Trucks
Source types 52 and 53 (Long- and Short-haul Single Unit Trucks) also included some trucks in VIUS 1997 Strata 1 and 2, thus a similar algorithm was applied.

   VIUS 1997 trucks of the source type in Strata 3, 4, and 5 were assigned to the appropriate MOVES weight class based on VIUS 1997 detailed average weight information.
   VIUS 1997 trucks of the source type in Strata 1 and 2 were identified by engine size and broad average weight category.
   Strata 1 and 2 trucks in the heavier (10,001-14,000 lbs, etc) VIUS 1997 broad categories were matched one-to-one with the MOVES weight classes.
   For trucks in the lower broad categories (6,000 lbs-or-less and 6001-10,000 lbs), we used VIUS 1997 to determine the fraction of trucks by model year and fuel type that fell into each engine size/broad weight class combination (the "VIUS fraction")
   We did not believe the ORNL light-duty vehicle database adequately represented single unit trucks. Thus, the trucks with a VIUS 1997 average weight of 6,000 lbs or less and an engine size less than 5 liters were distributed equally among the MOVES weight classes 20, 25, 30, 35, 40, 45, 50, and 60. Because no evidence existed of very light trucks among the vehicles with larger engines (5 liter or larger), these were equally distributed among MOVES weight classes 40, 45, 50 and 60.
   The trucks with a VIUS 1997 average weight of 6,001-10,000 lbs were distributed equally among the MOVES weight classes 70, 80, 90 and 100. 

Combination Trucks
Long- and short-haul combination trucks (source types 61 and 62) did not include any vehicles of VIUS 1997 Strata 1 or 2. Thus we used the detailed VIUS 1997 average weight information and engine size information to assign engine size and weight classes for all of these trucks.

When VIUS2002 became available, we updated values that had been based on VIUS1997. The VIUS 2002 contains an estimate of the average weight (vehicle weight plus cargo weight) of 1998-2002 model year vehicle or vehicle/trailer combination as it was most often operated when carrying a typical payload during 2002. These estimates were used to determine the MOVES weightClassID categories for these trucks. Table 4-5 shows the weight ranges used for each weightClassID. Any vehicles with a zero or missing value for the average weight and without a weight classification in the WeightAvgCK field were excluded from the analysis for determining the average weight distributions.

Since there is a smaller number of gasoline trucks among the single unit and refuse trucks, all model years (1998-2002) were combined to determine a single weight distribution to use for these model years.

The VIUS1997 based estimates were retained for light-duty trucks (source types 31 and 32) and for all model years prior to 1998.

In cases where distributions were missing (no survey information), distributions from a nearby model year with the same source type was used. Weight distributions for all 2003 and newer model years were set to be the same as for the 2002 model year for each source type.
Buses
For intercity buses, we used information from Table II-7 of the FTA 2003 Report to Congress[40] that specified the number of buses in various weight categories. This information is summarized in below in Table 19-3.  Note the FTA uses the term "over-the-road bus" to refer to the class of buses roughly equivalent to the MOVES intercity bus category.  The FTA weight categories were mapped to the equivalent MOVES weight classes.

                    Table 21-3 FTA Estimate of Bus Weights
                                       
                                 Weight (lbs)
                                       
                                 MOVES Weight
                                    ClassID
                           MOVES Weight Range (lbs)
                            Number of buses (2000)
                                   Bus type
                                   0-20,000
                                       
                                       
                                    173,536
                             school & transit
                                 20,000-30,000
                                       
                                       
                                    392,345
                             school & transit
                                 30,000-40,000
                                      400
                                 33,000-40,000
                                    120,721
                     school & transit & intercity
                                 40,000-50,000
                                      500
                                 40,000-50,000
                                    67,905
                                   intercity
                                     total
                                       
                                       
                                    754,509
                                       

                  Table 21-4 1999 Bus Population Comparisons
Data Source
Total Buses
Intercity Buses
Transit Buses
School Buses
FHWA MV-1

732,189

FHWA MV-10
(excludes PR)
728,777

592,029*
FHWA adjusted for PR

594,800
FTA NTD

55,706

APTA ***

75,087

Polk TIP(R)

460,178
School Bus Fleet Fact Book

429,086
Motorcoach Census[39]** 

44,200

* Includes some church & industrial buses.
** Includes Canada.
*** Includes trolleybuses.

Using the 1999 bus population estimates in Table 19-4, we were able to estimate the fraction of all buses that were intercity buses and then to estimate the fraction of intercity buses in each weight bin.  In particular:

    Estimated number of intercity buses in 2000: 
 
 	754,509 * (84,454/(84,454+55,706+592,029)) = 87,028
 
    Estimated number of intercity buses 30,000-40,000 lbs:  
 
 	87,028 - 67,905 = 19,123
    Estimated intercity bus weight distribution: 
 	
 	Class 400 = 19,123/87,028 = 22%
       	Class 500 = 67,905/87,028 = 78%

This distribution was used for all model years.

For transit buses, we took average curb weights from Figure II-6 of the FTA Report to Congress[40] and added additional weight to account for passengers and alternative fuels.  The resulting in-use weights were all in the range from 33,850 to 40,850. Thus all transit buses were assigned to the weight class "400" (33,000 - 40,000 lbs) for all model years. This estimate could be improved if more detailed weight information for transit buses becomes available.

For school buses, we used information from a survey of California school buses. While this data is older and may not be representative of the national average distribution, it was the best data source available.  The California data provided information on number of vehicles by gross vehicle weight class and fuel as detailed in Table 19-5.

                      Table 21-5 California School Buses
                                       
                                      Gas
                                    Diesel
                                     Other
                                     Total
LHDV
                                                                           2740
                                                                           4567
                                                                              8
                                                                           7315
MHDV
                                                                            467
                                                                           2065
                                                                              2
                                                                           2534
HHDV
                                                                            892
                                                                          11639
                                                                            147
                                                                          12678
Total
                                                                           4099
                                                                          18271
                                                                            157
                                                                               

To estimate the distribution of average weights among the MOVES weight classes, we assumed that the Light Heavy-Duty (LHDV) school buses were evenly distributed among weightClassIDs 70, 80, 90, 100, and 140. Similarly, we assumed the Medium Heavy-Duty (MHDV) school buses were evenly distributed among weightClassIDs 140, 160, 195, 260, and 330 and the Heavy Heavy-Duty (HHDV) school buses were evenly distributed among weightClassIDs 195, 260, 330, and 440.  

The final default weight distributions for buses are summarized in Table 19-6. 

            Table 21-6 Weight Distributions for Buses by Fuel Type
                                       
                             Intercity Buses (41)
                              Transit Buses (42)
                               School Buses (43)
                                 Weight Class
                                    Diesel
                               Diesel & Gas
                                    Diesel
                                      Gas
                                      70
                                       
                                       
                                    0.0500
                                    0.1337
                                      80
                                       
                                       
                                    0.0500
                                    0.1337
                                      90
                                       
                                       
                                    0.0500
                                    0.1337
                                      100
                                       
                                       
                                    0.0500
                                    0.1337
                                      140
                                       
                                       
                                    0.0726
                                    0.1565
                                      160
                                       
                                       
                                    0.0226
                                    0.0228
                                      195
                                       
                                       
                                    0.1819
                                    0.0772
                                      260
                                       
                                       
                                    0.1819
                                    0.0772
                                      330
                                       
                                       
                                    0.1819
                                    0.0772
                                      400
                                    0.2197
                                    1.0000
                                    0.1593
                                    0.0544
                                      500
                                    0.7800
                                       
                                       
                                       

Refuse Trucks
Because the sample of Refuse Trucks in VIUS was small, the weight distributions were calculated for model year groups rather than individual model years.  As for other trucks, the WeightClass was determined from the VIUS reported average weight. 
           Table 21-7 Refuse Truck SizeWeight Fractions by Fuel Type
Gasoline
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Engine Size
Weight (lbs.)
Pre-1997
1997 and Newer
                                                                               
                                                                               
                                                                               
                                                                               
3-3.5L
5000-6000
                                                                       0.009074
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
7000-8000
                                                                       0.148826
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
9000-10000
                                                                       0.070720
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
10000-14000
                                                                       0.135759
                                                                       0.324438
                                                                               
                                                                               
                                                                               
                                                                               
>5L
14000-16000
                                                                       0.199961
                                                                       0.593328
                                                                               
                                                                               
                                                                               
                                                                               
>5L
16000-19500
                                                                       0.055085
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
19500-26000
                                                                       0.205341
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
26000-33000
                                                                       0.022105
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
33000-40000
                                                                       0.153129
                                                                              0
                                                                               
                                                                               
                                                                               
                                                                               
>5L
50000-60000
                                                                              0
                                                                       0.082234
                                                                               
                                                                               
                                                                               
                                                                               
Sum
                                                                               
                                                                       1.000000
                                                                       1.000000
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Diesel
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Engine Size
Weight (lbs.)
Pre-1998
                                                                           1998
                                                                           1999
                                                                           2000
                                                                           2001
2002 and Newer
3.5-4L
10000-14000
                                                                       0.007758
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
4-5L
10000-14000
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                       0.006614
4-5L
14000-16000
                                                                              0
                                                                              0
                                                                              0
                                                                       0.015505
                                                                              0
                                                                              0
4-5L
16000-19500
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                       0.011670
                                                                              0
>5L
9000-10000
                                                                       0.006867
                                                                       0.009593
                                                                              0
                                                                              0
                                                                              0
                                                                              0
>5L
10000-14000
                                                                       0.011727
                                                                              0
                                                                              0
                                                                              0
                                                                       0.019438
                                                                              0
>5L
14000-16000
                                                                       0.022960
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
>5L
16000-19500
                                                                       0.063128
                                                                              0
                                                                       0.011367
                                                                       0.047200
                                                                              0
                                                                              0
>5L
19500-26000
                                                                       0.099782
                                                                       0.035378
                                                                       0.026212
                                                                       0.052132
                                                                       0.018329
                                                                       0.026079
>5L
26000-33000
                                                                       0.102077
                                                                       0.019625
                                                                       0.067419
                                                                       0.072106
                                                                       0.043877
                                                                              0
>5L
33000-40000
                                                                       0.237485
                                                                       0.103922
                                                                       0.088975
                                                                       0.085991
                                                                       0.042678
                                                                       0.046966
>5L
40000-50000
                                                                              0
                                                                       0.283642
                                                                       0.275467
                                                                       0.165624
                                                                       0.266357
                                                                       0.194716
>5L
50000-60000
                                                                       0.336484
                                                                       0.338511
                                                                       0.326902
                                                                       0.384612
                                                                       0.315133
                                                                       0.474469
>5L
60000-80000
                                                                       0.111730
                                                                       0.196424
                                                                       0.193238
                                                                       0.176831
                                                                       0.282517
                                                                       0.224995
>5L
80000-100000
                                                                              0
                                                                              0
                                                                       0.010420
                                                                              0
                                                                              0
                                                                       0.013081
>5L
100000-130000
                                                                              0
                                                                       0.012904
                                                                              0
                                                                              0
                                                                              0
                                                                       0.013081
Sum
                                                                               
                                                                       1.000000
                                                                       1.000000
                                                                       1.000000
                                                                       1.000000
                                                                       1.000000
                                                                       1.000000

Motor Homes
No detailed information was available on average engine size and weight distributions for motor homes. We assumed all motor home engines were 5 L or larger. As a surrogate for average weight, we used information on gross vehicle weight provided in the Polk TIP(R) 1999 database by model year and mapped the Polk GVW Class to the MOVES weight bins.  These values are likely to overestimate average weight. The Polk TIP(R) information did not specify fuel type, so we assumed that the heaviest vehicles in the Polk database were diesel-powered and the remainder were powered by gasoline. This led to the weight distributions in Table 19-8 and Table 19-9.
       Table 21-8 Weight Fractions for Diesel Motor Homes by Model Year
                                 Polk GVW bin
                                       3
                                       4
                                       5
                                       6
                                       7
                                       8
                              MOVES weight class
                                      140
                                      160
                                      195
                                      260
                                      330
                                      400
                                  Model Year
                                    Diesel
                               1975-and-earlier
                                                                       0.171431
                                                                       0.792112
                                                                       0.029828
                                                                              0
                                                                       0.006629
                                                                              0
                                     1976
                                                                       0.637989
                                                                       0.340639
                                                                       0.018755
                                                                       0.000436
                                                                       0.002181
                                                                              0
                                     1977
                                                                        0.68944
                                                                       0.292308
                                                                       0.012168
                                                                       0.000277
                                                                       0.005531
                                                                       0.000277
                                     1978
                                                                       0.423524
                                                                       0.574539
                                                                              0
                                                                       0.000387
                                                                        0.00155
                                                                              0
                                     1979
                                                                       0.096922
                                                                       0.899344
                                                                              0
                                                                       0.001067
                                                                       0.002667
                                                                              0
                                     1980
                                                                       0.462916
                                                                       0.537084
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1981
                                                                              0
                                                                       0.941973
                                                                              0
                                                                       0.030174
                                                                              0
                                                                       0.027853
                                     1982
                                                                              0
                                                                       0.868333
                                                                              0
                                                                          0.049
                                                                           0.03
                                                                       0.052667
                                     1983
                                                                              0
                                                                       0.912762
                                                                       0.000203
                                                                       0.014845
                                                                       0.030096
                                                                       0.042094
                                     1984
                                                                              0
                                                                       0.932659
                                                                       0.000835
                                                                       0.009183
                                                                       0.036732
                                                                       0.020592
                                     1985
                                                                              0
                                                                       0.881042
                                                                       0.001474
                                                                       0.010761
                                                                       0.083285
                                                                       0.023438
                                     1986
                                                                              0
                                                                       0.855457
                                                                       0.013381
                                                                       0.022962
                                                                       0.089534
                                                                       0.018667
                                     1987
                                                                              0
                                                                       0.791731
                                                                       0.085493
                                                                       0.022498
                                                                       0.087164
                                                                       0.013113
                                     1988
                                                                              0
                                                                        0.72799
                                                                       0.148917
                                                                       0.015469
                                                                       0.093335
                                                                       0.014289
                                     1989
                                                                              0
                                                                        0.73298
                                                                       0.128665
                                                                       0.043052
                                                                       0.082792
                                                                       0.012511
                                     1990
                                                                              0
                                                                       0.173248
                                                                       0.614798
                                                                       0.043628
                                                                       0.149939
                                                                       0.018387
                                     1991
                                                                              0
                                                                              0
                                                                       0.619344
                                                                       0.063712
                                                                       0.296399
                                                                       0.020545
                                     1992
                                                                              0
                                                                              0
                                                                       0.551548
                                                                        0.01901
                                                                       0.385085
                                                                       0.044356
                                     1993
                                                                              0
                                                                              0
                                                                       0.345775
                                                                       0.471873
                                                                       0.144844
                                                                       0.037509
                                     1994
                                                                              0
                                                                              0
                                                                        0.45546
                                                                       0.354386
                                                                       0.159622
                                                                       0.030531
                                     1995
                                                                              0
                                                                              0
                                                                       0.635861
                                                                       0.163195
                                                                        0.17468
                                                                       0.026264
                                     1996
                                                                              0
                                                                              0
                                                                       0.553807
                                                                       0.229529
                                                                       0.184208
                                                                       0.032456
                                     1997
                                                                              0
                                                                              0
                                                                       0.666905
                                                                       0.193167
                                                                       0.111299
                                                                       0.028628
                                     1998
                                                                              0
                                                                              0
                                                                          0.267
                                                                       0.335069
                                                                       0.357508
                                                                       0.040423
                                     1999+
                                                                              0
                                                                              0
                                                                              0
                                                                       0.736656
                                                                       0.233886
                                                                       0.029458

      Table 21-9 Weight Fractions for Gasoline Motor Homes by Model Year
                                 Polk GVW bin
                                       3
                                       4
                                       5
                                       6
                                       7
                                       8
                              MOVES weight class
                                      140
                                      160
                                      195
                                      260
                                      330
                                      400
                                  Model Year
                                   Gasoline
                               1975-and-earlier
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1976
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1977
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1978
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1979
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1980
                                                                              1
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1981
                                                                       0.747723
                                                                       0.252277
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1982
                                                                       0.732235
                                                                       0.267765
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1983
                                                                       0.714552
                                                                       0.285448
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1984
                                                                       0.641577
                                                                       0.358423
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1985
                                                                       0.692314
                                                                       0.307686
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1986
                                                                       0.720248
                                                                       0.279752
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1987
                                                                       0.606635
                                                                       0.393365
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1988
                                                                       0.459429
                                                                       0.540571
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1989
                                                                       0.551601
                                                                       0.448399
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1990
                                                                       0.543354
                                                                       0.456646
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                     1991
                                                                       0.612025
                                                                       0.322022
                                                                       0.065952
                                                                              0
                                                                              0
                                                                              0
                                     1992
                                                                        0.54464
                                                                       0.373999
                                                                       0.081361
                                                                              0
                                                                              0
                                                                              0
                                     1993
                                                                       0.583788
                                                                       0.361277
                                                                       0.054935
                                                                              0
                                                                              0
                                                                              0
                                     1994
                                                                       0.481099
                                                                       0.361146
                                                                       0.157755
                                                                              0
                                                                              0
                                                                              0
                                     1995
                                                                        0.52997
                                                                       0.198479
                                                                       0.271551
                                                                              0
                                                                              0
                                                                              0
                                     1996
                                                                       0.435959
                                                                       0.289453
                                                                       0.274588
                                                                              0
                                                                              0
                                                                              0
                                     1997
                                                                       0.221675
                                                                       0.433334
                                                                       0.344991
                                                                              0
                                                                              0
                                                                              0
                                     1998
                                                                       0.288222
                                                                       0.581599
                                                                        0.13018
                                                                              0
                                                                              0
                                                                              0
                                     1999+
                                                                       0.170133
                                                                       0.392451
                                                                       0.288411
                                                                       0.149004
                                                                              0
                                                                              0

 References