APPENDIX 2 

MOBILE Modeling Assumptions 
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North Carolina I/M SIP May 21, 2010 Appendix 2 - 1
North Carolina I/M SIP May 21, 2010 Appendix 2 - 2
North Carolina I/M SIP May 21, 2010 Appendix 2 - 3
MOBILE6.2 Modeling Results 

MOBILE6.2 model runs to demonstrate compliance for the 1997 8-hour ozone standards. Since 

Mecklenburg and Gaston Counties were 1-hour ozone maintenance areas, the performance 

standards for these two counties were slightly different from the remaining counties in the 1997 

8-hour ozone nonattainment area (Cabarrus, Lincoln, Rowan, Union Counties and Coddle Creek 

and Davidson Townships in Iredell County). Below are the emission factors for the two 

performance standards that are required to be met and the program target based upon how North 

Carolina’s Inspection and Maintenance (I/M) program is actual run. The North Carolina I/M 

program meets the emission reduction targets in the attainment year. The State of North 

Carolina commits to meeting the performance standard. 

Emission Factors for Mecklenburg and Gaston Counties (grams/mile) 

 VOC NOx 

Performance Standard 0.784 0.750 

Program Target 0.726 0.688 

Emission Factors for Remaining Counties (grams/mile) 

 VOC NOx 

Performance Standard 1.363 1.027 

Program Target 1.280 0.936 

 

North Carolina I/M SIP May 21, 2010 Appendix 2 - 4
MOBILE6.2 Modeling Assumptions 

Modeled Calendar Year:

• As required by the Code of Federal Regulations (CFR) 40 CFR 51.352(e) the evaluation 

date is to be set at six years after the effective date of designation. The CharlotteGastonia-Rock Hill, North Carolina-South Carolina Moderate Nonattainment area 

(referred to as the Metrolina area) has an effective designated date of June 15, 2004, 

therefore, the evaluation date is 2010. 

I/M Program Start Year:

• Performance Standards for Mecklenburg and Gaston Counties: According to 51.352(c), 

the required start date was 2002, with the idle test for 1968 to 1995 vehicles and On 

Board Diagnostic II (OBD) for 1996 and newer vehicles. 

• Program Target for Mecklenburg and Gaston Counties: Although these two counties had 

the idle test implemented in prior to 2002, the OBD I/M program was implemented in 

these two counties starting July 2002 for all 1996 and newer vehicles. By the evaluation 

year (2010), the idle test had been phased-out and only the OBD test was required. 

Therefore, the I/M program start year for Mecklenburg and Gaston Counties was set at 

2003. 

• Performance Standards for Remaining Counties: According to 51.352(e), the required 

start date was 2008, with the idle test for 1968 to 2000 vehicles and On Board Diagnostic 

II (OBD) for 2001 and newer vehicles. 

• Program Target for Cabarrus and Union Counties: Although these two counties had the 

idle test implemented in prior to 2002, the OBD I/M program was implemented in these 

two counties starting July 2002 for all 1996 and newer vehicles. By the evaluation year 

(2010), the idle test had been phased-out and only the OBD test was required. Therefore, 

the I/M program start year for Cabarrus and Union Counties was set at 2003. 

• Program Target for Iredell, Lincoln and Rowan Counties: The OBD I/M program, for all 

1996 and newer vehicles, was implemented in Iredell and Rowan Counties starting July 

2003 and in Lincoln County starting January 2004. Therefore, the I/M program start year 

for Cabarrus and Union Counties was set at 2003. 

Anti-Tampering Program:

• North Carolina began a statewide safety inspection program in 1975. This program 

includes checking the vehicle for tampering of emission control equipment. Vehicles 35 

years old and newer are inspected. 

Vehicle Registration and VMT mix:

• North Carolina Division of Air Quality (NCDAQ) receives vehicle registration data for 

Mecklenburg and Gaston Counties combined and for the remaining counties in that 

nonattainment area uses the statewide vehicle registration data. The 2008 vehicle 

registration data, the most recent data available, was used for these runs. The vehicle 

registration data is attached at the end of this summary. 

North Carolina I/M SIP May 21, 2010 Appendix 2 - 5
• The VMT mix was based on the latest data available from the transportation partners and 

is presented below. 

0.3751 0.0939 0.3127 0.0963 0.0443 0.0388 0.0037 0.0031 

0.0024 0.0086 0.0021 0.0023 0.0082 0.0019 0.0010 0.0056 

Vehicle Speeds:

• To minimize the number of runs as recommended by the United States Environmental 

Protection Agency (USEPA), one vehicle speed of 24 miles per hour was used for all 

runs. 

Reid Vapor Pressure:

• For Mecklenburg and Gaston Counties, the Reid Vapor Pressure (RVP) is 7.8 pounds per 

square inch (psi) during the summer months as required by 40 CFR 80.27. 

• For the remaining nonattainment counties, the RVP is 9.0 psi during the summer months. 

Temperature, Relative Humidity and Barometric Pressure:

• The temperature, relative humidity and barometric pressure used in these modeling runs 

were the same data used in the latest attainment demonstration plan. This data was based 

on average July 2002 data for the Metrolina region. 

• The hourly temperature data as formatted in the input files: 

71.0 73.8 77.0 80.3 82.5 85.4 87.3 88.5 89.1 88.5 89.6 89.2

86.3 82.6 77.8 77.5 76.2 75.9 75.0 74.0 73.2 82.3 71.6 71.0

• The hourly relative humidity data as formatted in the input files: 

91. 86. 78. 71. 65. 59. 53. 50. 48. 51. 47. 47.

53. 61. 70. 71. 76. 77. 79. 83. 85. 87. 88. 91.

• The barometric pressure is set to 30 inches of mercury, which is consistent with the 

average summertime barometric pressure in North Carolina. 

Altitude:

• North Carolina is considered a low altitude region for modeling purposes. 

North Carolina I/M SIP May 21, 2010 Appendix 2 - 6
*Convert MOBILE5 Registration Fractions to MOBILE6-Based Registration Fractions

*

*Calendar Year: 2008.000User-Input

*

*MOBILE5b Reg Fractions

* 0.081 0.081 0.076 0.077 0.076 0.073 0.070 0.065 0.067 0.059

* 0.049 0.043 0.034 0.034 0.025 0.020 0.015 0.011 0.009 0.007

* 0.005 0.004 0.003 0.002 0.015

* 0.042 0.058 0.063 0.055 0.063 0.059 0.060 0.064 0.065 0.061

* 0.054 0.050 0.039 0.040 0.038 0.026 0.019 0.016 0.015 0.017

* 0.015 0.013 0.012 0.008 0.049

* 0.122 0.153 0.111 0.094 0.079 0.059 0.042 0.050 0.053 0.051

* 0.035 0.035 0.018 0.024 0.012 0.011 0.005 0.005 0.005 0.006

* 0.005 0.004 0.002 0.003 0.018

* 0.101 0.109 0.136 0.094 0.077 0.074 0.044 0.053 0.062 0.052

* 0.025 0.036 0.017 0.020 0.012 0.007 0.007 0.005 0.006 0.007

* 0.006 0.006 0.005 0.004 0.034

* 0.061 0.051 0.097 0.068 0.045 0.057 0.053 0.050 0.050 0.045

* 0.031 0.026 0.034 0.034 0.019 0.024 0.023 0.013 0.012 0.010

* 0.013 0.022 0.026 0.034 0.101

* 0.040 0.046 0.100 0.078 0.078 0.076 0.065 0.070 0.061 0.085

* 0.023 0.052 0.039 0.035 0.028 0.021 0.013 0.011 0.014 0.006

* 0.007 0.007 0.008 0.006 0.031

* 0.062 0.114 0.108 0.105 0.076 0.058 0.051 0.066 0.073 0.068

* 0.035 0.042 0.024 0.030 0.015 0.011 0.007 0.010 0.011 0.008

* 0.006 0.005 0.003 0.003 0.005

* 0.088 0.123 0.107 0.094 0.069 0.077 0.059 0.053 0.047 0.040

* 0.032 0.024 0.021 0.020 0.014 0.014 0.010 0.007 0.005 0.006

* 0.005 0.006 0.009 0.008 0.060

*

*

* MOBILE6 Vehicle Classes:

* 1 LDV Light-Duty Vehicles (Passenger Cars)

* 2 LDT1 Light-Duty Trucks 1 (0-6,000 lbs. GVWR, 0-3750 lbs. LVW)

* 3 LDT2 Light Duty Trucks 2 (0-6,000 lbs. GVWR, 3751-5750 lbs. LVW)

* 4 LDT3 Light Duty Trucks 3 (6,001-8500 lbs. GVWR, 0-3750 lbs. LVW)

* 5 LDT4 Light Duty Trucks 4 (6,001-8500 lbs. GVWR, 3751-5750 lbs. LVW)

* 6 HDV2B Class 2b Heavy Duty Vehicles (8501-10,000 lbs. GVWR)

* 7 HDV3 Class 3 Heavy Duty Vehicles (10,001-14,000 lbs. GVWR)

* 8 HDV4 Class 4 Heavy Duty Vehicles (14,001-16,000 lbs. GVWR)

* 9 HDV5 Class 5 Heavy Duty Vehicles (16,001-19,500 lbs. GVWR)

* 10 HDV6 Class 6 Heavy Duty Vehicles (19,501-26,000 lbs. GVWR)

North Carolina I/M SIP May 21, 2010 Appendix 2 - 7
* 11 HDV7 Class 7 Heavy Duty Vehicles (26,001-33,000 lbs. GVWR)

* 12 HDV8A Class 8a Heavy Duty Vehicles (33,001-60,000 lbs. GVWR)

* 13 HDV8B Class 8b Heavy Duty Vehicles (>60,000 lbs. GVWR)

* 14 HDBS School Busses

* 15 HDBT Transit and Urban Busses

* 16 MC Motorcycles (All)

*

REG DIST

* RESULTING MOBILE6-BASED REGISTRATION FRACTIONS

*

*MOBILE6 REGISTRATION FRACTIONS BY VEHICLE CLASS AND AGE

* LDV M5 LDGV

 1 0.081 0.081 0.076 0.077 0.076 0.073 0.070 0.065 0.067 0.059

 0.049 0.043 0.034 0.034 0.025 0.020 0.015 0.011 0.009 0.007

 0.005 0.004 0.003 0.002 0.015

* LDT1 M5 LDGT1

 2 0.042 0.058 0.063 0.055 0.063 0.059 0.060 0.064 0.065 0.061

 0.054 0.050 0.039 0.040 0.038 0.026 0.019 0.016 0.015 0.017

 0.015 0.013 0.012 0.008 0.049

* LDT2 M5 LDGT1

 3 0.042 0.058 0.063 0.055 0.063 0.059 0.060 0.064 0.065 0.061

 0.054 0.050 0.039 0.040 0.038 0.026 0.019 0.016 0.015 0.017

 0.015 0.013 0.012 0.008 0.049

* LDT3 M5 LDGT2

 4 0.122 0.153 0.111 0.094 0.079 0.059 0.042 0.050 0.053 0.051

 0.035 0.035 0.018 0.024 0.012 0.011 0.005 0.005 0.005 0.006

 0.005 0.004 0.002 0.003 0.018

* LDT4 M5 LDGT2

 5 0.122 0.153 0.111 0.094 0.079 0.059 0.042 0.050 0.053 0.051

 0.035 0.035 0.018 0.024 0.012 0.011 0.005 0.005 0.005 0.006

 0.005 0.004 0.002 0.003 0.018

* HDV2B M5 HDVs (Combined HDGV and HDDV)

 6 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV3 M5 HDVs (Combined HDGV and HDDV)

 7 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV4 M5 HDVs (Combined HDGV and HDDV)

 8 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

North Carolina I/M SIP May 21, 2010 Appendix 2 - 8
 0.006 0.006 0.004 0.004 0.019

* HDV5 M5 HDVs (Combined HDGV and HDDV)

 9 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV6 M5 HDVs (Combined HDGV and HDDV)

 10 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV7 M5 HDVs (Combined HDGV and HDDV)

 11 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV8a M5 HDVs (Combined HDGV and HDDV)

 12 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDV8b M5 HDVs (Combined HDGV and HDDV)

 13 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDBS M5 HDVs (Combined HDGV and HDDV)

 14 0.082 0.112 0.122 0.099 0.077 0.066 0.048 0.060 0.067 0.060

 0.030 0.039 0.021 0.025 0.013 0.009 0.007 0.008 0.009 0.008

 0.006 0.006 0.004 0.004 0.019

* HDBT M5 HDDVs

 15 0.062 0.114 0.108 0.105 0.076 0.058 0.051 0.066 0.073 0.068

 0.035 0.042 0.024 0.030 0.015 0.011 0.007 0.010 0.011 0.008

 0.006 0.005 0.003 0.003 0.005

* Motorcycles M5 MC

 16 0.088 0.123 0.107 0.094 0.069 0.077 0.059 0.053 0.047 0.040

 0.032 0.024 0.021 0.020 0.014 0.014 0.010 0.007 0.005 0.006

 0.005 0.006 0.009 0.008 0.060

North Carolina I/M SIP May 21, 2010 Appendix 2 - 9
*Convert MOBILE5 Registration Fractions to MOBILE6-Based Registration Fractions

*

*Calendar Year: 2008.000User-Input

*

*MOBILE5b Reg Fractions

* 0.046 0.062 0.061 0.067 0.065 0.063 0.063 0.061 0.067 0.062

* 0.054 0.050 0.042 0.045 0.035 0.029 0.023 0.018 0.015 0.013

* 0.010 0.008 0.006 0.005 0.031

* 0.025 0.037 0.040 0.042 0.052 0.048 0.048 0.052 0.057 0.054

* 0.052 0.052 0.041 0.046 0.048 0.034 0.027 0.024 0.023 0.028

* 0.026 0.022 0.021 0.015 0.083

* 0.051 0.075 0.074 0.067 0.071 0.056 0.045 0.050 0.056 0.051

* 0.040 0.044 0.032 0.041 0.030 0.022 0.016 0.014 0.017 0.021

* 0.018 0.012 0.014 0.010 0.072

* 0.042 0.049 0.057 0.050 0.052 0.047 0.039 0.048 0.052 0.046

* 0.032 0.038 0.031 0.039 0.028 0.020 0.018 0.016 0.019 0.024

* 0.023 0.018 0.020 0.016 0.177

* 0.031 0.038 0.101 0.079 0.058 0.060 0.063 0.056 0.058 0.043

* 0.030 0.024 0.028 0.025 0.016 0.016 0.013 0.019 0.014 0.012

* 0.010 0.023 0.033 0.037 0.111

* 0.032 0.046 0.083 0.069 0.080 0.078 0.066 0.075 0.060 0.078

* 0.020 0.058 0.040 0.031 0.025 0.020 0.014 0.012 0.014 0.013

* 0.009 0.009 0.013 0.011 0.044

* 0.046 0.080 0.087 0.077 0.064 0.056 0.046 0.063 0.071 0.072

* 0.039 0.049 0.034 0.036 0.026 0.019 0.013 0.015 0.020 0.018

* 0.018 0.014 0.009 0.008 0.019

* 0.077 0.107 0.097 0.085 0.067 0.077 0.064 0.055 0.048 0.041

* 0.031 0.027 0.026 0.020 0.017 0.014 0.009 0.007 0.007 0.007

* 0.007 0.008 0.013 0.011 0.078

*

*

* MOBILE6 Vehicle Classes:

* 1 LDV Light-Duty Vehicles (Passenger Cars)

* 2 LDT1 Light-Duty Trucks 1 (0-6,000 lbs. GVWR, 0-3750 lbs. LVW)

* 3 LDT2 Light Duty Trucks 2 (0-6,000 lbs. GVWR, 3751-5750 lbs. LVW)

* 4 LDT3 Light Duty Trucks 3 (6,001-8500 lbs. GVWR, 0-3750 lbs. LVW)

* 5 LDT4 Light Duty Trucks 4 (6,001-8500 lbs. GVWR, 3751-5750 lbs. LVW)

* 6 HDV2B Class 2b Heavy Duty Vehicles (8501-10,000 lbs. GVWR)

* 7 HDV3 Class 3 Heavy Duty Vehicles (10,001-14,000 lbs. GVWR)

* 8 HDV4 Class 4 Heavy Duty Vehicles (14,001-16,000 lbs. GVWR)

* 9 HDV5 Class 5 Heavy Duty Vehicles (16,001-19,500 lbs. GVWR)

* 10 HDV6 Class 6 Heavy Duty Vehicles (19,501-26,000 lbs. GVWR)

North Carolina I/M SIP May 21, 2010 Appendix 2 - 10
* 11 HDV7 Class 7 Heavy Duty Vehicles (26,001-33,000 lbs. GVWR)

* 12 HDV8A Class 8a Heavy Duty Vehicles (33,001-60,000 lbs. GVWR)

* 13 HDV8B Class 8b Heavy Duty Vehicles (>60,000 lbs. GVWR)

* 14 HDBS School Busses

* 15 HDBT Transit and Urban Busses

* 16 MC Motorcycles (All)

*

REG DIST

* RESULTING MOBILE6-BASED REGISTRATION FRACTIONS

*

*MOBILE6 REGISTRATION FRACTIONS BY VEHICLE CLASS AND AGE

* LDV M5 LDGV

 1 0.046 0.062 0.061 0.067 0.065 0.063 0.063 0.061 0.067 0.062

 0.054 0.050 0.042 0.045 0.035 0.029 0.023 0.018 0.015 0.013

 0.010 0.008 0.006 0.005 0.031

* LDT1 M5 LDGT1

 2 0.025 0.037 0.040 0.042 0.052 0.048 0.048 0.052 0.057 0.054

 0.052 0.052 0.041 0.046 0.048 0.034 0.027 0.024 0.023 0.028

 0.026 0.022 0.021 0.015 0.083

* LDT2 M5 LDGT1

 3 0.025 0.037 0.040 0.042 0.052 0.048 0.048 0.052 0.057 0.054

 0.052 0.052 0.041 0.046 0.048 0.034 0.027 0.024 0.023 0.028

 0.026 0.022 0.021 0.015 0.083

* LDT3 M5 LDGT2

 4 0.051 0.075 0.074 0.067 0.071 0.056 0.045 0.050 0.056 0.051

 0.040 0.044 0.032 0.041 0.030 0.022 0.016 0.014 0.017 0.021

 0.018 0.012 0.014 0.010 0.072

* LDT4 M5 LDGT2

 5 0.051 0.075 0.074 0.067 0.071 0.056 0.045 0.050 0.056 0.051

 0.040 0.044 0.032 0.041 0.030 0.022 0.016 0.014 0.017 0.021

 0.018 0.012 0.014 0.010 0.072

* HDV2B M5 HDVs (Combined HDGV and HDDV)

 6 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV3 M5 HDVs (Combined HDGV and HDDV)

 7 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV4 M5 HDVs (Combined HDGV and HDDV)

 8 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

North Carolina I/M SIP May 21, 2010 Appendix 2 - 11
 0.020 0.016 0.015 0.012 0.097

* HDV5 M5 HDVs (Combined HDGV and HDDV)

 9 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV6 M5 HDVs (Combined HDGV and HDDV)

 10 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV7 M5 HDVs (Combined HDGV and HDDV)

 11 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV8a M5 HDVs (Combined HDGV and HDDV)

 12 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDV8b M5 HDVs (Combined HDGV and HDDV)

 13 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDBS M5 HDVs (Combined HDGV and HDDV)

 14 0.044 0.065 0.072 0.064 0.058 0.052 0.043 0.056 0.062 0.059

 0.036 0.044 0.033 0.037 0.027 0.020 0.015 0.015 0.019 0.021

 0.020 0.016 0.015 0.012 0.097

* HDBT M5 HDDVs

 15 0.046 0.080 0.087 0.077 0.064 0.056 0.046 0.063 0.071 0.072

 0.039 0.049 0.034 0.036 0.026 0.019 0.013 0.015 0.020 0.018

 0.018 0.014 0.009 0.008 0.019

* Motorcycles M5 MC

 16 0.077 0.107 0.097 0.085 0.067 0.077 0.064 0.055 0.048 0.041

 0.031 0.027 0.026 0.020 0.017 0.014 0.009 0.007 0.007 0.007

 0.007 0.008 0.013 0.011 0.078

North Carolina I/M SIP May 21, 2010 Appendix 2 - 12