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Appendix C 

On-road Mobile Source Inventory 

Documentation 
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TABLE OF CONTENTS 

1.0 Introduction and Scope ... .........................................................................................................5 

2.0 Overall Methodology .................................................................................................................5 

3.0 Quality Assurance Measures .....................................................................................................5 

4.0 Discussion of Mobile Source Categories..................................................................................6 

5.0 Data Files Provided on DVD.....................................................................................................23 
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LIST OF TABLES 

Table 4.2-1: Population Data ..................................................................................................................... 9 

Table 4.2-2: Vehicle Average Annual Increase Percentage.....................................................................10

Table 4.2-3: Vehicle Population Growth .................................................................................................10 

Table 4.2-4: VMT and Speed Data Provided by the Charlotte Department of Transportation ...............11 

Table 4.2-5: On-road Mobile Source Average Summer Day NOx and VOC Emissions.........................15 

Table 4.4-1: On-road Mobile Source NOx and VOC Emissions..............................................................22 

Table 4.4-2: NOx and VOC MVEBs for 2013 and 2022 .........................................................................22 

Table 4.4-3: NOx and VOC Refueling Emissions for 2013 and 2022 .....................................................22 

LIST OF FIGURES 

Figure F4.3-1: Metrolina Area 2002 Daily Summertime VOC Emissions..............................................17 

Figure F4.3-2: Metrolina Area 2009 Daily Summertime VOC Emissions..............................................17 

Figure F4.3-3: 8-hour Ozone response to 30% anthropogenic VOC reductions in 2009 ........................19 

Figure F4.3-2: 8-hour Ozone Response to 50% mobile VOC decrease in 2008 .....................................20 
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1.0 INTRODUCTION AND SCOPE 

 

The on-road mobile source inventory detailed in this section has been developed for the Rock 

Hill-Fort Mill Area Transportation Study (RFATS) Metropolitan Planning Organization (MPO) 

portion of York County, South Carolina within the Charlotte-Gastonia-Rock Hill, NC-SC 

nonattainment area (the York NA area) for the 1997 8-hour ozone NAAQS Redesignation 

Demonstration and Maintenance Plan. On-road mobile sources were identified from the United 

States Environmental Protection Agency (EPA) highway mobile model, MOVES2010a. Onroad mobile sources consist of cars, trucks, and motorcycles that travel on the main roads and 

interstates. 

Although the South Carolina Department of Health and Environmental Control (SCDHEC or 

Department) Bureau of Air Quality (BAQ) inventories all the criteria pollutants and a large 

number of toxic pollutants, only the nitrogen oxides (NOx) and volatile organic compounds 

(VOC) are reported here since they are important for ozone formation. The emissions in this 

report were projected to the years 2010 (the base year), 2013, 2016, 2019, and 2022. 

2.0 EMISSION ESTIMATION APPROACH

Mobile source emissions are estimated by the methodologies suggested in the EPA document 

Technical Guidance on the Use of MOVES2010 for Emission Inventory Preparation in State 

Implementation Plans and Transportation Conformity (EPA-420-B-10-023, April 2010), 

hereafter referred to as the Technical Guidance document. 

For on-road mobile sources, the EPA mobile model MOVES2010a is used to generate emissions. 

The estimation of emissions from mobile sources involves multiplying an activity level by an 

emission factor. MOVES2010a is a computer model designed to estimate emission factors and 

emission inventories of VOCs, NOx, CO, PM10, PM2.5 and other pollutants and precursors for 

cars, trucks, buses, and motorcycles. MOVES2010a, released in August 2010, was designed to 

replace the previous emissions model, MOBILE6.2, which was released in 2004 (69 FR 28830). 

MOVES2010a replaces MOBILE6.2 as the emissions model that EPA will maintain and support. 

MOVES2010a can be used to estimate exhaust and evaporative emissions as well as brake and 

tire wear emissions from all types of on-road vehicles. 

3.0 QUALITY ASSURANCE MEASURES 

 

The quality analysis (QA) for the on-road mobile source category can be broken into three 

components: 1) inputs, 2) MOVES2010a run specification (runspec), and 3) MOVES2010a 

output. Each of these components is detailed in the paragraphs below. 

In all cases, input information being used for the MOVES2010a runs were not received in 

MOVES2010a format. Anytime data had to be manipulated to get it into the proper format, the 

final data was compared back to the original data to make sure there were no errors made and the 

values are represented correctly in the input files. 
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After the speed and vehicle miles traveled (VMT) information was acquired from the Charlotte 

Department of Transportation (CDOT), the data was checked for reasonableness against previous 

years’ data for the area, where possible. The base year (2010) VMT was compared to actual 

whole county VMT data. Also, each year’s estimated annual VMT was compared to each other 

to make sure they were all reasonable and consistent and no errors were made in generating the 

inputs. The speeds were all reviewed to make sure they were consistent with the road type and 

time of day. 

 

Once the input files were prepared, a staff member not responsible for generating the inputs spot 

checked some of the files to make sure they looked reasonable and the values added up properly. 

This was especially helpful in reviewing the average speed distribution inputs as the 

development of the files was very tedious and errors could easily occur. If any discrepancies 

were found, they were noted back to the person who generated the input files for correction. 

 

Since more than one staff member was responsible for doing the MOVES2010a runs, a template 

was created that outlined all selections and steps that needed to be included in the runspecs. This 

ensured consistency in the runspecs. 

Once MOVES2010a was run, the output results were compared to each other to make sure they 

looked consistent. A couple of the years were run by more than one person to make sure the 

same output emissions were received. 

 

A final QA step is to check the kilograms per day (kg/day) emissions developed using the input 

data and compare this to previous years to check for reasonableness. 

4.0 DISCUSSION OF MOBILE SOURCE CATEGORIES 

On-road mobile sources produce VOCs and NOx, along with a host of other pollutants. 

Emissions of NOx and VOC are estimated in the mobile source inventory required for the 

maintenance plan. The objective of the following section is to describe the source category and 

the emissions estimation procedures. This section also includes tables summarizing the 

estimated emissions for a typical July day for the York NA area. 

4.1 Introduction and Scope 

On-road mobile sources are considered those vehicles that travel on the roadways. Emissions 

from motor vehicles occur throughout the day while the vehicle is in motion, at idle, parked, and 

during refueling. All of these emissions processes need to be estimated in order to properly 

reflect the total emissions from this source category. It is important to note that emissions from 

vehicle refueling (Stage 2 refueling emissions) and spillage loss during refueling emissions are 

accounted for in the Area source portion of the inventory and are not included in the 

MOVES2010a runs. 
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The EPA developed the MOVES2010a model to estimate emissions based on more current 

information on the way vehicles are driven in a particular area. Key inputs for MOVES2010a 

include information on the age of vehicles on the roads, the average speed of those vehicles, 

what types of roads those vehicles are traveling, and any control technologies in place in an area 

to reduce emissions for motor vehicles (e.g., emissions inspection programs), temperature, and 

humidity data. 

 

A very important component of the on-road mobile emissions estimation process is interagency 

consultation. The South Carolina interagency consultation partners involved in the development 

of the redesignation request and maintenance plan include EPA Region 4, South Carolina 

Department of Transportation (SCDOT), Federal Highways (FHWA), Federal Transit Authority 

(FTA), SCDHEC and the RFATS MPO. The interagency consultation partners consult on 

MOVES2010a modeling inputs as well as issues concerning the motor vehicle emission budgets 

(MVEBs) through monthly conference calls and via email. 

 

4.2 MOVES2010a Runs 

 

Runspecs and inputs were developed using the EPA’s Technical Guidance document as 

guidance. Due to the size and the complexity of the MOVES2010a input and output files, the 

MOVES2010a input files and output files will be provided electronically. A complete listing of 

these files is referenced in Section 5.0.

4.2.1 Runspec Selections 

In order to use MOVES 2010a to develop emissions for SIP purposes, certain criteria had to be 

met in selections made in the runspec. The following are selections made for each tab of the 

runspec: 

Scale: 

Domain/Scale= County 

Calculation Type= Inventory 

Time Spans: 

 Time Aggregation Level= Hour 

Years= 2010 (Base Year); this was changed for successive runs to represent 2013, 2016, 2019, & 

2022 

 Months= July (To represent an average summer month) 

Days= Weekdays (Recommended for SIPs in the Technical Guidance document) 

 Hours= Start Hour= 00:00-00:59 End Hour= 23:00-23:59 (This represents all 24 hrs in a day) 

Geographic Bounds:
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York County, South Carolina 

Domain Input Database appears at the bottom of this tab and provides access to the County Data 

Manager, where the actual York County specific inputs were imported for each run. These 

county specific inputs will be discussed in detail later in this document. 

Vehicles/Equipment- Onroad Vehicle Equipment: 

Gasoline and Diesel combinations with all source use types were selected (26 total fuel/source 

use type selections). 

The Technical Guidance document indicates users must select the appropriate fuel and vehicle 

type combinations in the On Road Vehicle Equipment panel to reflect the full range of vehicles 

that will operate in the county. It was confirmed that there are no transit buses using CNG in the 

nonattainment portion of York County, so CNG transit buses were not selected. 

Road Type:

 All 5 road types were selected.

The Technical Guidance document indicates that all SIP and regional conformity analyses must 

include the Off-Network road type in order to account for emissions from vehicle starts, extended 

idle activity, and evaporative emissions (for hydrocarbons). 

Pollutants/processes: 

All processes for total gaseous hydrocarbons, non-methane hydrocarbons, VOC and NOx have 

been selected, except refueling and spillage emissions, since these are already captured in our 

area source inventory. 

Strategies- Alternative vehicle fuels and technologies:

Since no CNG transit buses are present in our modeled area, the MOVES2010a default 

FuelEngFraction table was amended to shift all the VMT assigned to CNG buses to diesel transit 

vehicles. This amended file was imported to replace the default file in MOVES2010a. 

Output- General Output: 

Units: Mass units= Kilograms 

 Units: Energy units= Million BTU 

 Units: Distance units= Miles 

Activity: ‘Population’ and ‘Distance Traveled’ were selected, as recommended by the Technical 

Document. 

Kilograms have been selected because kg/day has been used since the RFATS Attainment 

Demonstration was originally submitted in 2007. 
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Output- Output Emission Detail:

 Always: 24-Hour Day and County were selected. 

 For all vehicle equipment categories: No selections were made. 

 On Road: No selections were made. 

Advanced Performance Features: 

No selections were made. 

4.2.2 Input Assumptions For MOVES2010a 

Source Type Population 

To develop source type population data, SCDHEC obtained a July 31, 2010, snapshot of vehicle 

population for the whole York County from the South Carolina Department of Motor Vehicles 

(SCDMV). This population data was not broken out by the MOVES2010a source type 

categories. Passenger vehicles and motorcycles were the only MOVES2010a source types that 

could be distinguished from all other vehicles. As the Technical Guidance document indicates, 

the 2010 default York County source type population data was exported from MOVES2010a and 

used to help apportion the actual vehicle type population. Using the ratio of MOVES2010a 

passenger cars and passenger trucks to each other, the actual York County passenger vehicle 

population was separated into passenger cars and passenger trucks. For the remaining nonpassenger and non-motorcycle sources, the MOVES2010a ratio of each was calculated against 

all non passenger and non-motorcycle population. This ratio was then multiplied by the 

remaining actual York population (after the passenger cars, passenger trucks, and motorcycle 

populations had been subtracted). This methodology created MOVES2010a-ready source type 

population values for all of York County, but this effort is only dealing with the York NA area. 

 

The ratio of the York NA area population to the county population was used to estimate emissions 

for the York NA area. Table 4.2-1 contains the 2005 population for York County. The York NA 

area population was determined from the RFATS MPO 2005 Baseline Socio-Economic Data 

(submitted to Charlotte in 2006). Using this data, the estimated York NA area population is 153,900, 

and 75.8 percent of York County’s population is in the York NA area. This percentage was used to 

allocate the county-level emissions to the York NA area. 

Table 4.2-1: Population Data

Population of York County 203,054 

Population of York NA area 153,900 

Percentage of Population in York NA area 75.8 
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Once the base year source type population was generated, the future year files for 2013, 2016, 

2019, and 2022 needed to be estimated. The SCDMV was not able to provide future year 

vehicle population data, nor did they have any suggestions on expected annual growth in vehicle 

population values. In order to get an estimate of average annual vehicle population growth, 

SCDHEC collected two years of historical York County vehicle population data, 2004 and 2010. 

Using these two years the average annual increase percentage was calculated (Table 4.2-2). This 

data was used to grow the population for 2013, 2016, 2019, and 2022. 

Table 4.2-2: Vehicle Average Annual Increase Percentage 

2004 2010 

# vehicles 

increased 

over 6 years 

% increase 

from 2004 

Avg annual 

increase over 6 

years 

Increase for a 3 

yr period 

167,235 197,331 30,096 17.99% 2.99% 8.97% or 0.0897

Note that the 2004 population data was obtained from the SC Statistical Abstract, found online at 

http://abstract.sc.gov/. This value includes all population data, even some categories that 

represent non-motorized vehicles. In order to compare the 2004 data to the 2010 data, the nonmotorized vehicles were added back into the 2010 total population for this comparison only. The 

non-motorized vehicles are excluded in the source type population inputs for MOVES2010a. 

This growth analysis indicates an average 3 year growth rate of 8.97 percent or 0.0897. The base 

year 2010 source type population as multiplied by 1.0897 to generate the 2013 estimates. This 

was continued until all future years were calculated, as outlined in the following table: 

Table 4.2-3: Vehicle Population Growth

Year 

Id 

Source 

Type 

Source Type 

Population 

3yr 

adjustment 

ratio 

2013 

Source 

Type 

Population

2016 

Source 

Type 

Population 

2019 

Source 

Type 

Population 

2022 

Source 

Type 

Population 

2010 11 4,758 1.0897 51,85 5,650 6,157 6,709

2010 21 59,890 1.0897 65,263 71,117 77,496 84,447

2010 31 45,181 1.0897 49,233 53,650 58,462 63,706

2010 32 23,752 1.0897 25,883 28,205 30,735 33492

2010 41 121 1.0897 132 144 157 171

2010 42 63 1.0897 69 75 82 89

2010 43 822 1.0897 896 976 1,064 1,159

2010 51 70 1.0897 76 83 90 98

2010 52 4,760 1.0897 5,187 5,652 6,159 6,711

2010 53 612 1.0897 667 726 792 863

2010 54 1,101 1.0897 1,199 1,307 1,424 1,552

2010 61 1,015 1.0897 1,106 1,205 1,313 1,431

2010 62 1,214 1.0897 1,323 1,442 1,571 1,712
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Vehicle Type VMT

Daily weekday VMT and speed data was obtained from CDOT (see Table 4.2-4). The CDOT 

data was used to compile the average daily VMT by MOVES2010a road type. VMT was 

distributed to the MOVES2010a source types according to the distribution in SCDOT’s 2009 

Functional Class Annual Report. To convert the daily VMT data to an annual value, which is 

required by MOVES2010a, the EPA’s aadvmtcalculator_hpms.xls VMT converter tool was 

used. This tool used default monthly, daily, and hourly ratios to create an annual VMT profile 

from an average daily profile. The resulting files (filenames hpmsvtypeyear, monthvmtfraction, 

and dayvmtfraction) were exported from the converter tool and used in the MOVES2010a 

modeling. The MOVES2010a default table with filename hourvmtfraction was exported from 

MOVES2010a and used for each applicable year. 2016 is a leap year and it was confirmed that 

the converter tool did use leap year fractions tables to estimate the annual VMT for this year. 

Table 4.2-4: York County Nonattainment Area VMT and Speed Data Provided by the 

 Charlotte Department of Transportation

AM Peak Midday PM Peak Night DAILY 

2010 VMT Spd VMT Spd VMT Spd VMT Spd VMTassn Spd 

Rural Interstate 241,701 57 281,780 66 267,887 58 156,450 65 947,818 61

Rural Principal 

Art. 24,294 38 26,126 54 26,639 40 11,906 58 88,965 44

Rural Minor Art. 69,492 36 91,390 38 78,222 33 57,184 46 296,287 37

Rural Major 

Collect. 64,730 40 84,868 45 74,449 39 48,555 49 272,602 43

Rural Minor 

Collect. 8,071 20 10,251 22 9,026 14 5,439 31 32,787 19

Rural Local 86,802 27 126,624 27 105,812 28 64,874 27 384,112 27

Urban Interstate 224,233 56 266,933 63 249,241 59 147,122 63 887,529 60

Urban 

Frwy/Exprwy 22,100 41 34,213 43 25,670 40 16,112 45 98,095 42

Urban Principal 

Art. 198,097 30 292,454 34 225,320 29 167,218 40 883,089 32

Urban Minor Art. 178,520 30 268,069 33 207,788 29 153,477 40 807,853 32

Urban Collector 62,067 24 91,957 24 73,342 18 41,627 33 268,993 23

Urban Local 157,506 24 264,677 24 186,802 24 133,773 25 742,758 24

Rural 495,089 621,039 562,036 344,408 2,022,572 

Urban 842,523 1,218,304 968,162 659,330 3,688,318 

County 1,337,612 1,839,342 1,530,198 1,003,738 5,710,890 

 

 

AM Peak Midday PM Peak Night DAILY 

2013 VMT Spd VMT Spd VMT Spd VMT Spd VMTassn Spd 

Rural Interstate 249,203 56 292,919 66 275,743 56 162,092 66 979,956 60

Rural Principal 

Art. 25,604 36 27,496 53 28,117 38 12,952 58 94,169 43

Rural Minor Art. 74,079 35 97,224 37 82,489 33 60,708 45 314,500 37
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Rural Major 

Collect. 68,746 40 89,600 45 78,067 40 51,077 49 287,491 43

Rural Minor 

Collect. 8,745 19 11,227 23 9,490 16 5,835 32 35,297 20

Rural Local 87,156 27 125,865 27 106,525 28 65,015 27 384,561 27

Urban Interstate 226,182 55 270,736 63 249,087 59 149,450 63 895,455 60

Urban 

Frwy/Exprwy 22,362 41 34,893 43 26,040 40 16,355 45 99,650 42

Urban Principal 

Art. 217,649 30 316,907 34 248,785 29 183,665 40 967,006 32

Urban Minor Art. 181,022 30 268,247 34 211,107 29 152,177 40 812,554 32

Urban Collector 63,214 25 90,797 25 74,981 19 41,714 33 270,706 23

Urban Local 159,900 24 265,963 24 189,537 24 135,297 25 750,697 24

Rural 513,533 644,331 580,431 357,678 2,095,974 

Urban 870,330 1,247,543 999,537 678,658 3,796,068 

County 1,383,863 1,891,874 1,579,968 1,036,336 5,892,041 

 

 

AM Peak Midday PM Peak Night DAILY 

2016 VMT Spd VMT Spd VMT Spd VMT Spd VMTassn Spd 

Rural Interstate 257,736 56 310,089 66 285,474 55 169,159 66 1,022,457 60

Rural Principal 

Art. 26,997 35 31,546 51 30,147 35 14,185 58 102,875 41

Rural Minor Art. 74,974 36 97,675 38 83,568 33 60,842 45 317,059 37

Rural Major 

Collect. 72,255 39 94,812 44 81,571 38 54,719 49 303,356 42

Rural Minor 

Collect. 9,094 18 11,747 22 9,839 16 6,089 32 36,768 20

Rural Local 89,483 27 128,595 27 109,770 28 66,935 27 394,782 27

Urban Interstate 232,891 56 284,716 63 256,266 58 156,166 63 930,039 60

Urban 

Frwy/Exprwy 23,269 41 36,981 43 27,250 40 17,078 45 104,578 42

Urban Principal 

Art. 218,268 30 320,130 34 250,038 28 187,695 40 976,132 32

Urban Minor Art. 179,631 30 266,258 34 208,632 29 152,350 40 806,871 32

Urban Collector 65,480 26 94,180 27 78,780 20 41,407 33 279,848 25

Urban Local 167,886 23 277,055 24 199,378 24 140,395 25 784,713 24

Rural 530,538 674,463 600,368 371,928 2,177,297 

Urban 887,425 1,279,321 1,020,344 695,091 3,882,181 

County 1,417,963 1,953,784 1,620,712 1,067,019 6,059,478 

 

 

AM Peak Midday PM Peak Night DAILY 

2019 VMT Spd VMT Spd VMT Spd VMT Spd VMTassn Spd 

Rural Interstate 269,281 54 328,319 66 297,646 53 178,311 66 1,073,557 58

Rural Principal 

Art. 27,776 35 33,408 50 30,874 35 14,947 58 107,005 41

Rural Minor Art. 78,675 36 102,522 37 87,434 32 63,594 45 332,226 36
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Rural Major 

Collect. 76,613 38 101,276 43 86,615 37 58,569 49 323,074 41

Rural Minor 

Collect. 9,488 17 12,475 21 10,505 16 6,376 33 38,843 19

Rural Local 94,801 27 136,960 27 116,785 28 71,479 27 420,025 27

Urban Interstate 241,799 54 299,429 63 266,577 57 163,579 63 971,385 59

Urban 

Frwy/Exprwy 24,346 40 38,622 42 28,348 39 17,840 45 109,156 41

Urban Principal 

Art. 227,988 29 334,876 33 260,698 27 197,307 40 1,020,869 31

Urban Minor Art. 190,412 30 279,969 33 220,218 28 160,360 40 850,959 32

Urban Collector 69,833 25 100,339 27 83,841 20 44,717 33 298,729 25

Urban Local 177,870 23 293,013 24 210,727 24 148,467 25 830,078 24

Rural 556,635 714,960 629,860 393,275 2,294,729 

Urban 932,248 1,346,247 1,070,410 732,270 4,081,175 

County 1,488,882 2,061,207 1,700,270 1,125,545 6,375,905 

 

 

AM Peak Midday PM Peak Night DAILY 

2022 VMT Spd VMT Spd VMT Spd VMT Spd VMTassn Spd 

Rural Interstate 279,264 51 345,159 66 308,270 50 187,484 66 1,120,177 57

Rural Principal 

Art. 28,145 32 33,530 47 31,260 32 15,147 55 108,083 38

Rural Minor Art. 82,315 35 107,084 37 90,921 31 66,434 45 346,754 36

Rural Major 

Collect. 80,522 37 106,955 42 91,114 36 61,905 48 340,496 40

Rural Minor 

Collect. 9,952 17 13,108 20 11,038 15 6,898 25 40,996 18

Rural Local 101,266 27 145,909 27 124,398 27 76,013 27 447,586 27

Urban Interstate 251,027 53 314,121 63 276,377 55 171,873 63 1,013,398 58

Urban 

Frwy/Exprwy 25,604 39 40,218 42 29,494 38 18,417 44 113,733 41

Urban Principal 

Art. 236,594 28 346,840 32 271,332 27 204,410 39 1,059,176 31

Urban Minor Art. 201,312 29 294,954 32 231,712 27 169,331 39 897,308 31

Urban Collector 74,295 25 106,250 26 88,993 19 47,219 32 316,757 24

Urban Local 187,652 23 308,212 24 222,427 23 156,641 25 874,932 24

Rural 581,463 751,746 657,001 413,882 2,404,092 

Urban 976,483 1,410,595 1,120,334 767,891 4,275,303 

County 1,557,946 2,162,340 1,777,335 1,181,773 6,679,395 

Fuel Formulation and Supply

The Technical Guidance document states that changes should be made only where local 

volumetric fuel property information is available, except in the case of RVP where a user should 

change the value to reflect the regulatory requirements and differences between ethanol- and 

non-ethanol blended gasolines. South Carolina does not have local fuel parameter data so the 
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MOVES2010a default fuel supply data was used, except the applicable fuel parameters were 

changed to reflect the summer RVP regulatory requirement of 9.0. 

Meteorology

For average summer day ozone for SIP or conformity purposes, the Technical Guidance 

recommends using average daily temperature profiles for July, or for the three month period that 

best represents the area’s ozone season. For this effort, the surface hourly data for the Charlotte 

International Airport was acquired from the Integrated Surface Hourly (ISH) database 

maintained by the National Climatic Data Center. Hourly temperature and dew point data for the 

month of July for the years 2004-2010 was extracted from the database. Average hourly 

temperatures and relative humidity for each hour of the dataset were calculated. 

Road Type Distribution

SCDOT’s 2009 Functional Class Annual Report was used to allocate an appropriate fraction of 

each source type’s VMT to each road type. This was used for all years. 

Age Distribution

Actual age distribution data was not available in time for this analysis, therefore MOVES2010a 

defaults were used. The Technical Guidance document states that “If users are unable to acquire 

data to develop a local age distribution or have reason to believe that data about locally 

registered vehicles is not necessarily representative of that entire portion of the fleet then 

MOVES2010a national default age distributions can be used.” 

Average Speed Distribution

Speed data for a.m. peak hours (6:00 a.m. to 9:00 a.m.), midday (9:00 a.m. to 3:00 p.m.), p.m. 

peak hours (6:00 p.m. to 9:00 p.m.) and nighttime hours (9:00 p.m. to 6:00 a.m.) was obtained 

for all modeled years from the CDOT. Vehicle hours traveled (VHT) was calculated for each 

urban and rural road type by dividing VMT by speed. VHT for each road type was then assigned 

to a MOVES2010a speed bin. There are 16 speed bins, whose speed ranges are detailed in the 

Technical Guidance document. VHT for each of the four MOVES2010a on-road road types was 

totaled for each time period of the day and a fraction developed for each speed bin. Each road 

type (4 road types), source type (13 source types), and hour (24 hourdayIDs for weekdays) 

combination has a fraction totaling 1.0. These fractions were calculated and saved in the proper 

MOVES2010a format and used in the modeling. 

 

FuelEngFraction (Engine Type and Fuel Used) Table

This MOVES2010a default table needed to be adjusted to account for the fact that there are no 

CNG transit buses operating in the RFATS area. The VMT assigned to CNG buses in the 

MOVES2010a default fuelEngFraction file was re-assigned to diesel buses. This file was saved 

and imported back into MOVES2010a for the model runs. This amended file was imported into 
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the Strategies-Alternative Vehicle Fuels & Technologies tab of the runspec for all the 

MOVES2010a runs. 

4.2.3 Estimated Emissions From On-Road Mobile Sources 

Using the outlined inventory approach, the MOVES2010a model gave a summary of emissions 

in kg per average summer day. A conversion factor was used to calculate the tons per day 

emissions from the kg per day value. Table 4.2-5 summarizes the NOx and VOC emissions. 

Table 4.2-5: On-road Mobile Source Average Summer Day NOx and VOC Emissions 

York County Nonattainment Area

2010 2013 2016 2019 2022 

kg/day Tons/day kg/day Tons/day kg/day Tons/day kg/day Tons/day kg/day Tons/day 

NOx 10,930 12.05 7,924 8.73 5,919 6.52 4,682 5.16 4,011 4.42 

VOC 3,554 3.92 2,846 3.14 2,367 2.61 2,074 2.29 1,939 2.14 

4.2.4 Motor Vehicle Emissions Budget for Conformity 

Transportation Conformity

The purpose of transportation conformity is to ensure that federal transportation actions 

occurring in a nonattainment area do not hinder the area from maintaining the 8-hour ozone 

standard. This means that the level of emissions estimated for the MPO’s Transportation 

Implementation Plan (TIP) and Long Range Transportation Plan (LRTP) must not exceed the 

Motor Vehicle Emissions Budget (MVEB) as defined in this maintenance plan. 

4.3 On-road Mobile Source VOC Insignificance 

The Transportation Conformity Rule Amendments for the 1997 8-hour ozone and fine particulate 

matter NAAQS addresses areas with insignificant motor vehicle emissions in Section 93.109(k) 

which states: 

Notwithstanding the other paragraphs in this section, an area is not required to satisfy a 

regional emissions analysis for §93.118 and/or §93.119 for a given pollutant/precursor and 

NAAQS, if EPA finds through the adequacy or approval process that a SIP demonstrates that 

regional motor vehicle emissions are an insignificant contributor to the air quality problem for 

that pollutant/precursor and NAAQS. The SIP would have to demonstrate that it would be 

unreasonable to expect that such an area would experience enough motor vehicle emissions 

growth in that pollutant/precursor for a NAAQS violation to occur. 

The rule explains that such a finding would be based on a number of factors, including the 

percentage of motor vehicle emissions in the context of the total SIP inventory, the current state 

of air quality as determined by monitoring data for that NAAQS, the absence of SIP motor 

vehicle control measures, and historical trends and future projections of the growth of motor 
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vehicle emissions. Also, in the EPA’s approval of VOC insignificance for the Triangle area of 

North Carolina (http://www.epa.gov/fedrgstr/EPA-AIR/2007/October/Day-03/a19513.htm), it 

states that the policy provides flexibility for areas where motor vehicle emissions have little or 

no impact on an area’s air quality problem. Further, EPA states that the policy provides for state 

and local resources to be directed towards reducing emissions from those sources that contribute 

the most to an area’s air quality problem. 

 

SCDHEC has examined a NCDAQ study designed to determine the sources of VOC emissions 

and their contribution to ozone formation in North Carolina, since the results of the study would 

apply to the part of York County included in the Metrolina nonattainment area. Due to the 

generally warm and moist climate of the Carolinas, vegetation abounds in many forms, and 

forested lands naturally cover much of each state. The biogenic sector is the most abundant 

source of VOC emissions in both Carolinas and accounts for approximately 90 percent of the 

total VOC emissions (89 percent for Region IV states and 88 percent for North Carolina, as 

stated in the VOC Insensitivity To Ozone Production In North Carolina submitted to EPA on 

August 3, 2010). Due to the overwhelming abundance of biogenic VOC emissions, NCDAQ 

determined the vast majority of North Carolina a NOx limited environment for the formation of 

ozone. This holds true for the Metrolina nonattainment area counties. Summaries from the 

VISTAS/ASIP 2002 and 2009 regional modeling effort were used to illustrate the abundance of 

the biogenic VOC emissions. Figures F4.3-1 and F4.3-2 provide the percent contributions from 

point, on-road mobile, off-road mobile, area, and biogenic sources to the total VOC emissions in 

the Metrolina nonattainment area in 2002 and 2009, respectively. For the two partial counties in 

the Metrolina nonattainment area, Iredell and York Counties, the whole county emissions were 

used since the modeling inventories are for whole counties. 
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3%

15%

4%

7%

71%

Point

On-Road Mobile

Off-Road Mobile

Area

Biogenic

2002 VOC Emissions

1132 tons/day

Figure F4.3-1: Metrolina Area 2002 Daily Summertime VOC Emissions 

2%

9%

3%

7%

79%

Point

On-Road Mobile

Off-Road Mobile

Area

Biogenic

2009 VOC Emissions

1038 tons/day

Figure F4.3-2: Metrolina Area 2009 Daily Summertime VOC Emissions 

In the Metrolina nonattainment area, on-road mobile sources contribute only 15 and 9 percent of 

the 2002 and 2009 total VOC emissions, respectively. Also, on-road mobile sources are 

expected to contribute only 5 percent of total VOC emissions in 2011. 

 

Also noteworthy are the projected decreases in on-road mobile VOC emissions. These 

reductions are due mainly to the retirement of older vehicles and the growing fleet of Tier 2 
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vehicles on the roads in future years. Some additional reductions are attributable to North 

Carolina's Inspection and Maintenance program in the Metrolina area. 

A modeling sensitivity test was performed by ASIP that allows an analysis of VOC contributions 

to ozone concentrations in the Southeastern United States. One of the analyses conducted by 

ASIP is a series of emissions sensitivity modeling runs to quantify the contributions of various 

emission sources to ozone and fine particles. The modeling system used in this analysis 

consisted of 3 components: 1) the Penn State University/National Center for Atmospheric 

Research Mesoscale Model (MM5 version 3.6.1+), 2) the Sparse Matrix Operator Kernel 

Emissions Modeling System (SMOKE version 2.1), and 3) the Community Multiscale Air 

Quality (CMAQ version 4.4) model. Model configurations, input data, and modeling methods 

are consistent with those suggested by the EPA in Guidance on the Use of Models and Other 

Analyses in Attainment Demonstrations for the 8-hour Ozone NAAQS. 

 

The emissions sensitivities are calculated by taking the difference between two air quality model 

simulations: one with base case emissions and another with reduced emissions inputs. The 

emissions sensitivity discussed here reduces all anthropogenic VOCs in the modeling domain by 

30 percent from projected 2009 emission levels. Translating this to the Metrolina nonattainment 

area emissions, this 30 percent anthropogenic VOC reduction is equivalent to about a 70 percent 

reduction of all on-road mobile VOC emissions in the Metrolina nonattainment area for 2009. 

This emissions sensitivity was run for a 39 day period (June 1-July 9). In all 39 days of the 

modeling simulation, the 8-hour ozone maximum concentrations were unchanged in the 

Metrolina nonattainment area - a clear indicator that on-road mobile VOC is an insignificant 

contributor to ozone formation in that area. In fact, there was not an 8-hour ozone response as 

high as 1 part per billion (ppb) anywhere in either North or South Carolina during the sensitivity 

simulation. Figure F4.3-3 provides an example from the 30 percent anthropogenic VOC 

reduction modeling illustrating the lack of ozone response for North and South Carolina. 
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Figure F4.3-3: 8-hour Ozone response to 30% anthropogenic VOC reductions in 2009 

Additional mobile source sensitivity simulations have been conducted by the NCDAQ. 

Although York County was not included in these model runs, it was determined by NCDAQ and 

SCDHEC that the sensitivity simulations would have the same impact in York County. These 

modeling runs focused specifically on the impact of mobile source VOC emissions on ozone. 

The sensitivity reduced mobile source VOC by 50 percent in the North Carolina counties in the 

Metrolina ozone nonattainment area (Cabarrus, Gaston, Iredell, Lincoln, Mecklenburg, Rowan 

and Union Counties) in the year 2008. This emissions sensitivity was run for a 7 day period 

(July 13-19). In all 7 days of the modeling simulation, the 8-hour ozone maximum 

concentrations were unchanged in the Metrolina nonattainment area, a clear indicator that onroad mobile VOC is an insignificant contributor to ozone formation in that area. Figure F4.3-4 

provides an example of the lack of an 8-hour ozone response from the 50 percent mobile VOC 

reduction sensitivity modeling. 
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Figure F4.3-4: 8-hour Ozone Response to 50% mobile VOC decrease in 2008 

Based on the information discussed above, the NCDAQ and SCDHEC steadfastly believe onroad mobile VOCs are insignificant contributors to ozone formation in the Metrolina 

nonattainment area. Emission estimates indicate on-road mobile VOC is a small percentage of 

the total VOC emissions inventory. On-road mobile VOC emissions are projected to decrease 

into the future notwithstanding VMT increases. The area is currently below the 1997 8-hour 

ozone NAAQS, and emission sensitivity modeling performed by ASIP and the NCDAQ 

indicates no change in future ozone concentrations when VOC emissions are significantly 

changed. 

Since the NCDAQ considered it unreasonable to expect that the Metrolina nonattainment area 

would experience enough motor vehicle VOC emissions growth for a future ozone violation to 

occur, neither the NCDAQ, nor SCDHEC set a MVEB for VOC for the Metrolina nonattainment 

area in their first SIP submittal in 2007. The SCDHEC consulted with its interagency 

transportation partners prior to reaching this conclusion. 

The EPA indicated by email on October 6, 2009, by phone on October 21, 2009 and again by 

phone on December 9, 2009, that it would not accept the justification presented for VOC 

insignificance for the Metrolina nonattainment area for the attainment demonstration. A VOC 
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budget for on-road mobile sources was then prepared and submitted with the 2010 attainment 

SIP. Therefore, the SCDHEC is again including a VOC MVEB with this submittal while 

preserving our position of VOC insignificance. 

Although a VOC MVEB has been developed and is being submitted, SCDHEC believes that a 

finding of VOC Insignificance for this area is supported. For purposes of transparency and 

providing information to the public, the following information summarizes our assessment of the 

appropriateness of a finding of VOC insignificance for this area. Pursuant to 93.109(k), the York 

County nonattainment area meets the listed criteria as follows:

 The percentage of motor vehicle emissions in the context of the total SIP inventory. Onroad mobile emissions were projected to account for 9 percent of VOC emissions for 

2009 in the attainment demonstration submitted in 2007. For 2011, on-road mobile 

emission sources were projected to account for 5 percent of VOC emissions. This is 

well within EPA’s guideline of 10 percent, and continues to show a decreasing trend in 

the percentage of VOC emissions attributed to on-road mobile emissions. Further 

decreases beyond 2011 are expected due to fleet turnover and cleaner engine 

standards. 

 

 The current state of air quality as determined by monitoring data for the NAAQS. As 

discussed above, the design value for the York monitor has remained below the 1997 8-

hour ozone NAAQS since 2002. In fact the design value has decreased 20 percent over 

that period. Annual values have decreased 13 percent since 2000. The annual value 

for the 2010 ozone season was 0.066 ppm. The 2010 design value is 0.067 ppm, well 

below the1997 standard of 0.08 (effectively 0.084) ppm. 

 The absence of SIP motor vehicle control measures. No SIP vehicle control measures 

have been needed and none proposed for the York County nonattainment area. 

 Historical trends and future projections of the growth of motor vehicle emissions. As 

table 4.2-5 above indicates, the State projects decreases in motor vehicle emissions. 

This assertion is supported by EPA’s discussion of its approval of VOC insignificance 

for the Triangle Area of North Carolina (http://www.epa.gov/fedrgstr/EPAAIR/2007/October/Day-03/a19513.htm.) In this Federal Register notice, EPA 

comments on North Carolina’s documentation showing an anticipated increase of 25-

30 percent in VMT for the Triangle Area, during which time on-road VOC emissions 

are expected to decline by 50 percent. Although the York County nonattainment area 

may show an increase in VMTs in the future, the vehicle emissions are expected to 

decline similarly to the declines in the Triangle area. 

4.4 Motor Vehicle Emissions Budgets 

 

According to Section 93.118 of the transportation conformity rule, a maintenance plan must 

establish MVEBs for the last year of the maintenance plan, in this case, 2022. Through the 

interagency consultation process, it was decided that interim MVEBs would also be set for the 

year 2013 in the RFATS area. 
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The MVEBs will be set in terms of kg/day. During the preparation of the York County 

nonattainment area attainment demonstration in 2007 it was determined through interagency 

consultation that kg per day would be the most appropriate unit to use for MVEBs and 

transportation conformity. 

Table 4.4-1 shows the York County nonattainment area on-road mobile NOx and VOC emissions 

expressed in tons per day and the corresponding kilograms per day values for 2013 and 2022. 

Table 4.4-1: On-road Mobile Source NOx and VOC Emissions 

 York County Nonattainment Area

 2013 2022 

Pollutant Tons/day Kg/day Tons/day Kg/day 

NOx 8.73 7,924 4.42 4,011

VOC 3.14 2,846 2.14 1,939

Upon the EPA’s affirmative adequacy finding for the partial county MVEBs, as shown in Table 

4.4-2, they will become the applicable MVEBs for the York County nonattainment area. Should 

EPA agree with SCDHEC that the contribution from on-road mobile VOC emissions is 

insignificant for the future attainment of the 1997 8-hour ozone NAAQS, no VOC budget will be 

required. 

Table 4.4-2: York County Nonattainment Area 

NOx and VOC MVEBs for 2013 and 2022

MVEB (Kilograms/day) Pollutant 

2013 2022 

NOx 7,924 4,011

VOC 2,846 1,939

The MOVES Technical Guidance document directs that all processes, including refueling 

emissions, be included in MOVES work for SIPS or regional conformity analysis. In South 

Carolina, however, these processes are accounted for in the area source inventory and have not 

been included in previous budgets or conformity analysis. For this reason, these processes have 

not been included in the inventories or the MVEB for this redesignation demonstration and 

maintenance plan. Refueling emissions are included separately in Table 4.4-3 for the budget 

years of 2013 and 2022 for informational purposes only. 

 

Table 4.4-3: York County Nonattainment Area 

NOx and VOC Refueling Emissions for 2013 and 2022

Kilograms/day Refueling Emissions

 2013 2022 

NOx 00

VOC 240.03 143.85
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5.0 DATA FILES PROVIDED ON DVD 

This section contains a list of all data files which were used in the MOVES2010a runs and are 

saved on the attached DVD. All of these files are in EXCEL (.xls) format, except the runspecs 

which come out of MOVES2010a and are saved as an .mrs file. 

 

2010 DATA: 

York_2011redesignation_2010_runspec.mrs 

York_2011redesignation_2010_output.xls 

York_2011redesignation_2010_hpmsvtypeyear.xls 

York_2011redesignation_2010_monthvmtfraction.xls 

York_2011redesignation_2010_dayvmtfraction.xls 

York_2011redesignation_2010_hourvmtfraction.xls 

York_2011redesignation_2010_sourcetypepopulation.xls 

York_2011redesignation_2010thru2022_met.xls 

York_2011redesignation_2010_avgspeeddistribution.xls 

York_2011redesignation_2010_agedistribution.xls 

York_2011redesignation_2010_fuel.xls 

York_2011redesignation_2010thru2022_roadtypedistribution.xls 

York_2011redesignation_2010thru2022_fuelengfraction.xls 

2013 DATA: 

York_2011redesignation_2013_runspec.mrs 

York_2011redesignation_2013_output.xls 

York_2011redesignation_2013_hpmsvtypeyear.xls 

York_2011redesignation_2013_monthvmtfraction.xls 

York_2011redesignation_2013_dayvmtfraction.xls 

York_2011redesignation_2013_hourvmtfraction.xls 

York_2011redesignation_2013_sourcetypepopulation.xls 

York_2011redesignation_2010thru2022_met.xls 

York_2011redesignation_2013_avgspeeddistribution.xls 

York_2011redesignation_2013_agedistribution.xls 

York_2011redesignation_2013thru2022_fuel.xls 

York_2011redesignation_2010thru2022_roadtypedistribution.xls 

York_2011redesignation_2010thru2022_fuelengfraction.xls 

2016 DATA: 

York_2011redesignation_2016_runspec.mrs 

York_2011redesignation_2016_output.xls 

York_2011redesignation_2016_hpmsvtypeyear.xls 

York_2011redesignation_2016_monthvmtfraction.xls 

York_2011redesignation_2016_dayvmtfraction.xls 

York_2011redesignation_2016_hourvmtfraction.xls 

York_2011redesignation_2016_sourcetypepopulation.xls 

York_2011redesignation_2010thru2022_met.xls 

York_2011redesignation_2016_avgspeeddistribution.xls 
Revision to the South Carolina Air Quality Implementation Plan    Appendix C – Page 24

RFATS Redesignation Demonstration and Maintenance Plan

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York_2011redesignation_2016_agedistribution.xls 

York_2011redesignation_2013thru2022_fuel.xls 

York_2011redesignation_2010thru2022_roadtypedistribution.xls 

York_2011redesignation_2010thru2022_fuelengfraction.xls 

2019 DATA: 

York_2011redesignation_2019_runspec.mrs 

York_2011redesignation_2019_output.xls 

York_2011redesignation_2019_hpmsvtypeyear.xls 

York_2011redesignation_2019_monthvmtfraction.xls 

York_2011redesignation_2019_dayvmtfraction.xls 

York_2011redesignation_2019_hourvmtfraction.xls 

York_2011redesignation_2019_sourcetypepopulation.xls 

York_2011redesignation_2010thru2022_met.xls 

York_2011redesignation_2019_avgspeeddistribution.xls 

York_2011redesignation_2019_agedistribution.xls 

York_2011redesignation_2013thru2022_fuel.xls 

York_2011redesignation_2010thru2022_roadtypedistribution.xls 

York_2011redesignation_2010thru2022_fuelengfraction.xls 

2022 DATA: 

York_2011redesignation_2022_runspec.mrs 

York_2011redesignation_2022_output.xls 

York_2011redesignation_2022_hpmsvtypeyear.xls 

York_2011redesignation_2022_monthvmtfraction.xls 

York_2011redesignation_2022_dayvmtfraction.xls 

York_2011redesignation_2022_hourvmtfraction.xls 

York_2011redesignation_2022_sourcetypepopulation.xls 

York_2011redesignation_2010thru2022_met.xls 

York_2011redesignation_2022_avgspeeddistribution.xls 

York_2011redesignation_2022_agedistribution.xls 

York_2011redesignation_2013thru2022_fuel.xls 

York_2011redesignation_2010thru2022_roadtypedistribution.xls 

York_2011redesignation_2010thru2022_fuelengfraction.xls