Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

1 Onroad Mobile Sources and Vehicle Refueling (Stage 2) 

Onroad mobile source emissions are those generated by operating vehicles on public roadways. 

Emissions from fuel combustion and evaporation were estimated. Emissions from vehicle 

refueling were estimated for 2015. SWCAA had already estimated emissions from vehicle 

refueling for 2002. 

1.1 Activity Level and Spatial Allocation 

The activity measurement for onroad mobile sources is the number of miles driven. The units 

are typically given in average daily vehicle miles traveled (ADVMT). ADVMT is normally 

estimated from traffic counts collected over a sampling area, or through use of travel demand 

models, which simulate vehicle travel patterns based on demographic and economic parameters 

and are validated with traffic counts. 

For this inventory, Clark County ADVMT was obtained from the Southwest Regional 

Transportation Council (RTC).1, 2 RTC provided VMT for 1996-2000 and 2015. ADVMT was 

provided by roadway link (approx 7000), road class, speed, and Inspection and Maintenance 

program. A vehicle Inspection and Maintenance (I/M) program is operated in the greater 

Vancouver area of Clark County. 

1.2 Temporal Allocation 

ADVMT was not provided for 2002. The growth factor from 2000 to 2002 was calculated based 

on linear interpolation of ADVMT for 2000 and 2015. The calculated factor was 1.042. This 

factor was used to grow the link-level 2000 ADVMT to 2002. 

ADVMT also had to be seasonally adjusted. WSDOT provided monthly ADVMT adjustment 

factors for the 1990 carbon monoxide and ozone nonattainment area base year inventory efforts 

(Table 2).3 The factors were compared to similar data for 19944 and showed very little change. 

WSDOT calculated the factors for two road classes: Interstates, and non-Interstates. The RTC 

Interstate and Ramp road classes were assigned to the WSDOT Interstate class, and the RTC 

Arterial, Local and Intrazonal classes were assigned to the WSDOT non-Interstate class. 

ADVMT was multiplied by the adjustment factors for July to estimate average ozone season day 

VMT. The WSDOT adjustment factors were multiplied by the ADVMT estimates and the 

average number of days per month to estimate total monthly VMT, which in turn was used in the 

annual emissions calculations. ADVMT estimates are shown in Table 3. 

Table 1: Estimated 2002 ADVMT 

Year ADVMT 

2000 6,725,065 

2015 8,857,114 

 

2002 est 7,009,338 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 2: WSDOT Monthly VMT Adjustment Factors 

Month Adjustment Adjustment 

Freeway Arterial/Local 

Month 

Freeway Arterial/Local 

Jan 0.878 0.914 Jul 1.083 1.061 

Feb 0.896 0.947 Aug 1.114 1.077 

Mar 0.963 1.001 Sep 1.044 1.013 

Apr 0.997 1.020 Oct 1.020 0.987 

May 1.013 1.024 Nov 0.975 0.950 

Jun 1.057 1.065 Dec 0.959 0.942 

Table 3: Clark County ADVMT, 2002 

I/M Area Arterial Interstate Intrazonal Local Ramp TOTAL 

Ozone season day 

No 817,415 914,020 8,815 207,697 12,124 1,960,072 

Yes 3,412,544 1,460,390 10,673 387,966 257,034 5,528,606 

 Total 4,229,959 2,374,410 19,488 595,663 269,158 7,488,678 

Annual 

No 281,312,517 308,224,823 3,033,829 71,478,747 4,088,456 668,138,372 

Yes 1,174,423,302 492,470,909 3,673,019 133,517,993 86,676,647 1,890,761,869 

 Total 1,455,735,818 800,695,732 6,706,848 204,996,740 90,765,103 2,558,900,241 

Table 4: Clark County ADVMT, 2015 

I/M Area Arterial Interstate Intrazonal Local Ramp TOTAL 

Ozone season day 

No 1,204,664 1,208,828 3,533 320,164 18,369 2,755,558 

Yes 4,186,454 1,751,667 3,693 465,401 301,257 6,708,472 

 Total 5,391,118 2,960,495 7,226 785,565 319,626 9,464,030 

Annual 

No 414,583,776 407,639,539 1,215,969 110,184,193 6,194,280 939,817,756 

Yes 1,440,763,683 590,695,098 1,270,782 160,167,252 101,589,554 2,294,486,369 

 Total 1,855,347,459 998,334,636 2,486,751 270,351,445 107,783,834 3,234,304,125 

1.3 Emission Rates: MOBILE6.2 

Emission rates in grams per mile were generated using the EPA model MOBILE6.2.5 Emission 

rates were generated for unique combinations of: month, facility type, vehicle type, speed, 

pollutant, and I/M area. 

Local data was used for the following input parameters: evaluation month, registration 

distribution, temperature, humidity, inspection and maintenance (I/M) program, speed, facility 

type, and fuel parameters for Reid vapor pressure (RVP). The parameters are described below. 

1.4 Evaluation Month 

The MOBILE model can calculate emission factors that represent a January 1 or July 1 fleet. 

The evaluation month affects the age of the fleet (and how reformulated gas is modeled when 

applicable). Reformulated gas does not apply in Washington, therefore the evaluation month 

only affects fleet age. Emissions for January through March were calculated with the January 1 

setting. The remaining months were calculated with the July 1 setting. 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

1.5 Registration Distribution 

Washington has a substantially older fleet than the national average. To model the effect of the 

older fleet, local data from the Washington State Department of Licensing (DOL) was used to 

calculate the July 1 vehicle age registration distribution.6

 Because DOL does not register all 

transit and school buses, alternate sources of information were obtained. Transit bus data came 

from Federal Transit Administration Annual Report data. 7 For school buses, the Puget Sound 

Clean Air Agency provided a spreadsheet of all Washington school buses in use in 2001,8 and 

the Washington State Office of the Superintendent of Public Instruction supplied data for 2004.9 

Distributions were assigned to evaluation years as shown below. 

Table 5: Registration Distribution Assignments 

Type Evaluation Years Year of Data Source 

vehicles except buses 2002 2002 DOL 

2015 2004 (most recent) DOL 

transit buses 2002 2002 FTA 

2015 2003 (most recent) FTA 

school buses 2002 2001 data via PSCAA 

2015 2004 (most recent) OSPI 

1.6 VMT Fractions 

The VMT mix is the percentages of VMT allocated to each individual vehicle type. The 

MOBILE6.2 model contains default mixes for each evaluation year between 1972 and 2020. 

The default light duty mix shows a decreasing trend in the amount of VMT assigned to cars 

relative to trucks/SUVs (68% in 1975 decreasing to 28% in 2020). In 2004, the default and the 

Washington sales data were fairly similar in the split between cars and trucks, although the 

individual truck type allocations were more heavily weighted toward the heavier classes in the 

Washington distribution. Statistics show that nationally, light truck/SUV sales have outpaced the 

sale of cars prior to 2004; however, the most recent sales year data (2004) indicate that cars 

outsold trucks/SUVs.10

For 2002, the national default mix was used. Due to the uncertainty of the future sales mix, it 

was decided to make use of the 2004 Washington sales mix for the years 2004 and beyond, 

including the 2015 projection. The national default split between heavy and light duty vehicles 

was retained (as well as the individual heavy duty vehicle class allocations), and the individual 

light duty class allocations for Washington were slightly adjusted by normalizing them to the 

overall default allocation for light duty vehicles. Light duty allocations are shown below. 

Table 6: Comparison of 2004 Default and Washington Light Duty VMT Mixes 

 LDV LDT1 LDT2 LDT3 LDT4

Default 0.4365 0.0752 0.2503 0.0771 0.0355

Washington 0.4486 0.0781 0.1972 0.1031 0.0475

Table 7: 2004 Default Heavy Duty and Motorcycle VMT Mix 

HDV2B HDV3 HDV4 HDV5 HDV6 HDV7 HDV8A HDV8B HDBS HDBT MC 

0.0386 0.0038 0.0030 0.0023 0.0085 0.0101 0.0111 0.0394 0.0019 0.0009 0.0058
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

1.7 Temperature and Humidity 

Meteorological and fuel parameters are necessary to calculate emissions from both onroad and 

nonroad sources. 

Temperatures for 2002 were taken from the Vancouver 4NNE meteorological station for each 

month to be used in the annual inventory calculations for 2002 and 2015.11 Temperatures for the 

typical ozone season day were calculated according to EPA guidance for prior 

attainment/maintenance plan efforts.12, 13, 14 The model requires minimum, maximum and 

ambient temperature. Ambient temperature is defined as: {min + [2/3 x (max-min)]}. 

Because information required to calculate average monthly humidity values for 2002 were not 

readily available, long-term average (1961-1990) humidity and pressure from Portland 

International Airport was used to develop the MOBILE6 input humidity parameters.15 The 

humidity value required in MOBILE6 is a mixing ratio in mass of water vapor per unit mass of 

dry air. A calculation formula based on relative humidity, temperature and pressure was 

distributed with MOBILE6.16

Temperatures and humidity are shown in Table 8. 

1.8 Reid Vapor Pressure (RVP) 

Because of the proximity to Portland, Clark County gasoline was assumed to follow Portland 

RVP requirements. Portland summertime limits are 9.0 psi for May and 7.8 psi for June – 

Sept.17 When using legal limits to calculate summertime RVP, EPA guidance and Ecology staff 

recommend calculating a safety margin. 18, 19 Accordingly, a calculated safety margin of 0.3 psi 

was applied to the period 2 (1992) RVP legal limit of 9.0 psi, bringing the May RVP value to 8.7 

psi. RVPs for the remaining months were taken from the 2002 fuel survey done by the American 

Automobile Manufacturers (AAM) and made available through the Western Regional Air 

Partnership (WRAP).20, 21 Fuel parameters are shown in Table 8. 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 8: Meteorological and Fuel RVP Parameters used in the MOBILE6.2 and/or 

NONROAD models 

Month Temperature 

minimum maximum ambient 

Humidity *RVP 

Ozone day 61 98 86 86 7.8 

 

Monthly and Seasonal 

Jan 34.5 44.8 41.4 24 14.3 

Feb 33.2 51.7 45.5 26 12.4 

Dec 35.4 48.8 44.3 25 14.3 

 Winter 34.4 48.4 43.7 25 14.3 

Mar 34.3 51.0 45.4 29 12.4 

Apr 40.0 59.5 53.0 32 12.4 

May 43.5 64.5 57.5 40 8.7 

 Spring 39.3 58.3 52.0 34 12.4 

Jun 49.9 73.8 65.8 49 7.8 

Jul 54.5 80.1 71.6 55 7.8 

Aug 51.9 80.2 70.8 64 7.8 

 Summer 52.1 78.0 69.4 56 7.8 

Sep 45.5 76.4 66.1 49 7.8 

Oct 38.6 63.1 54.9 39 9.8 

Nov 35.7 55.2 48.7 31 12.4 

 Fall 39.9 64.9 56.6 40 12.4 

* maximum monthly value selected for season 

1.9 Inspection and Maintenance (I/M) Program 

A Vehicle Inspection and Maintenance (I/M) program is operated in the greater Vancouver area 

of Clark County. Input parameters have been tracked to allow modeling of the program.22, 23, 24

MOBILE6.2 allows specification of up to seven I/M record sets to define an overall I/M 

program.25 The program could be captured using six I/M record sets as shown in Table 9. 

Table 9: I/M Program Parameters 

Parameter set 1 set 2 set 3 set 4 set 5 set 6 

Prog Start Yr 1993 1998 1993 2002 1993 1998 

Prog End Yr 2050 2050 2050 2050 2050 2050 

Test Freq biennial biennial biennial biennial biennial biennial 

Program Type test only test only test only test only test only test only 

Test Type ASM 2525 

phase-in* 

gas cap OBD exhaust** OBD Evap + 

gas cap** 

2500/idle gas cap 

Model Yrs 1968-1995 1968-1995 1996-2050 1996-2050 1968-2050 1968-2050 

Vehicle Types light duty 

gasoline 

light duty 

gasoline 

light duty 

gasoline 

light duty 

gasoline 

heavy duty 

gasoline 

heavy duty 

gasoline 

Stringency 36% n/a 36% n/a 36% n/a 

Compliance 93% 93% 93% 93% 93% 93% 

Waiver pre-81 4% 4% 4% 4% 4% 4% 

Waiver 1981+ 7% 7% 7% 7% 7% 7% 

Exempt Age 25 yrs 25 yrs 25 yrs 25 yrs 25 yrs 25 yrs 

Grace Age 5 yrs 5 yrs 5 yrs 5 yrs 5 yrs 5 yrs 

Tech Training yes yes yes yes yes Yes 

* ASM = acceleration simulation mode 

** OBD = on-board diagnostics 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

1.10 Road Class (Facility Type) and Speed 

The MOBILE6.2 model generates emission rates for four road classes: Interstate (without 

ramps)26, Ramps, Arterials, and Locals. All of the RTC road links had both road class and speed 

values. In MOBILE6.2, only Interstates and Arterials allow user speed input. To make use of 

the speeds provided by RTC for Local roads, they were assigned to the MOBILE6.2 Arterial 

class. RTC Ramps were assigned to the MOBILE6.2 Ramps class even though this meant that 

the RTC speeds could not be utilized. This was done in order to take advantage of 

MOBILE6.2’s unique driving cycle for Ramps. Ramps have a high acceleration driving cycle 

which cannot be captured in any other class, and acceleration affects emission rates. All road 

class assignments are shown in Table 10. 

Table 10: MOBILE6.2 Road Class Assignments 

RTC Class MOBILE6.2 Class 

Interstate Interstate 

Ramp Ramp 

Arterial Arterial 

Local Arterial 

Intrazonal Arterial 

Speeds were not included in the 2000 ADVMT file from RTC, but they were available in the 

2015 file. Speeds for 2000 were assigned by matching individual links to the 2015 ADVMT file 

by link ID number. The lesser of the morning, evening and off-peak link speeds for 2015 were 

assigned to the 2000 links. Links for 2000 which had no match in the 2015 file were assigned 

the average 2015 speed for the link’s road class. Neither the 2000 nor the 2015 file included 

speeds for the Intrazonal class links. An average speed of 15 mph was assigned to these links. 

1.11 Vehicle Refueling (Stage 2) Parameters 

It was assumed that the current at-the-pump stage 2 vapor recovery control program would be 

discontinued by 2015; therefore, vehicle refueling emissions were assumed to have no additional 

controls beyond on-board canister vapor recovery systems. The MOBILE6.2 model accounts for 

on-board vapor recovery canisters by default. 

1.12 Example Emission Rates 

Sample fleet average seasonal (winter, spring, summer, fall) and ozone season day emission 

factors produced by MOBILE6.2 on arterials at 30 mph are shown in Table 11. Refueling 

emission rates are shown in Table 12. 

Table 11: Sample Arterial Emission Factors at 30 mph in grams per mile 

Year Pollutant Ozone Day Winter Spring Summer Fall

2002 CO 46.600 66.264 62.043 43.515 56.535

2002 VOC 4.864 4.851 5.130 4.290 4.684

2002 NOX 5.689 6.624 6.228 5.682 6.108

 

2015 CO 14.427 27.915 25.861 15.639 22.985

2015 VOC 1.680 1.559 1.810 1.536 1.612

2015 NOX 1.780 2.088 1.916 1.729 1.870
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 12: Refueling Emission Factors in grams per mile 

Year Pollutant Ozone Day Winter Spring Summer Fall

2015 VOC 0.047 0.056 0.047 0.038 0.043

1.13 Emissions Estimates 

The emission rates in grams per mile calculated with M6.2 were multiplied by the temporally 

adjusted ADVMT estimates to calculate individual pollutant emissions for each of eight vehicle 

types and five road classes. Vehicle refueling emissions were calculated for the entire fleet. 

Table 13: Vehicle Refueling Emissions, 2015 

T/yr lbs/day 

163 813 

Table 14: Onroad Mobile Emissions in Pounds per Ozone Season Day, 2002 

Pollutant Class LDGV LDGT12 LDGT34 MC HDGV LDDV LDDT HDDV total

Arterial 96,957 71,561 31,198 750 9,449 25 37 2,501 212,431

Interstate 61,862 44,651 19,533 469 5,645 14 20 1,367 133,533

Intrazonal 515 363 164 6 95 0 0 25 1,167

Local 14,597 10,517 4,672 149 2,093 4 6 552 32,580

Ramp 9,030 5,938 2,476 45 544 2 2 147 18,182

CO 

 total 182,960 133,030 58,044 1,420 17,826 45 66 4,592 397,893

Arterial 10,359 6,482 2,802 178 773 13 22 531 21,158

Interstate 5,935 3,675 1,572 101 411 7 12 263 11,974

Intrazonal 67 41 18 1 7 0 0 5 139

Local 1,754 1,088 470 28 161 2 4 106 3,614

Ramp 701 443 191 11 47 1 1 32 1,428

VOC 

 total 18,816 11,729 5,052 320 1,398 23 40 937 38,313

Arterial 7,262 4,696 2,078 60 1,888 21 30 10,809 26,860

Interstate 4,131 2,689 1,185 38 1,142 14 20 8,556 17,788

Intrazonal 40 25 11 0 7 0 0 58 144

Local 1,127 718 318 8 244 3 5 1,636 4,061

Ramp 516 349 151 4 119 1 2 533 1,676

NOx 

 total 13,077 8,477 3,743 110 3,400 39 57 21,592 50,528
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 15: Onroad Mobile Emissions in Tons per Year, 2002 

Pollutant Class LDGV LDGT12 LDGT34 MC HDGV LDDV LDDT HDDV total

Arterial 19,561 15,694 6,523 110 1,478 4 6 433 43,803

Interstate 11,886 9,384 3,930 67 864 2 3 232 26,365

Intrazonal 102 81 34 1 15 0 0 4 237

Local 2,930 2,326 980 21 327 1 1 96 6,681

Ramp 1,704 1,280 515 7 83 0 0 25 3,614

CO 

 total 36,183 28,764 11,983 206 2,766 8 11 789 80,700

Arterial 1,693 1,101 471 22 106 2 4 92 3,490

Interstate 952 610 258 12 54 1 2 45 1,934

Intrazonal 11 7 3 0 1 0 0 1 23

Local 283 184 79 4 24 0 1 18 592

Ramp 114 75 32 1 6 0 0 6 234

VOC 

 total 3,052 1,977 843 39 191 4 7 161 6,273

Arterial 1,443 902 405 13 335 4 5 1,872 4,982

Interstate 810 507 227 8 199 2 3 1,454 3,212

Intrazonal 8 5 2 0 1 0 0 10 26

Local 218 137 61 2 43 1 1 283 746

Ramp 103 66 29 1 21 0 0 90 310

NOx 

 total 2,582 1,616 724 24 600 7 10 3,709 9,275

Table 16: Onroad Mobile Emissions in Pounds per Ozone Season Day, 2015 

Pollutant Class LDGV LDGT12 LDGT34 MC HDGV LDDV LDDT HDDV total

Arterial 37,831 26,496 16,297 1,058 2,296 4 14 728 84,723

Interstate 24,614 17,007 10,458 685 1,389 2 8 388 54,550

Intrazonal 60 41 25 3 7 0 0 2 139

Local 5,941 4,132 2,534 230 551 1 3 177 13,569

Ramp 2,923 1,882 1,138 64 133 0 1 44 6,185

CO 

 total 71,368 49,559 30,452 2,039 4,377 7 26 1,339 159,166

Arterial 4,234 2,517 1,512 244 231 1 8 270 9,015

Interstate 2,258 1,371 815 136 116 0 4 122 4,823

Intrazonal 8 5 3 0 1 0 0 1 18

Local 757 437 268 41 46 0 2 60 1,612

Ramp 263 154 94 15 14 0 1 17 556

VOC 

 total 7,521 4,484 2,692 436 408 1 14 470 16,024

Arterial 2,747 2,058 1,609 96 400 1 11 3,485 10,408

Interstate 1,619 1,223 938 61 243 1 8 2,681 6,775

Intrazonal 5 3 3 0 0 0 0 5 17

Local 466 337 261 12 52 0 2 536 1,667

Ramp 172 130 104 6 23 0 1 179 614

NOx 

 total 5,009 3,751 2,915 176 719 3 22 6,887 19,482
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 17: Onroad Mobile Emissions in Tons per Year, 2015 

Pollutant Class LDGV LDGT12 LDGT34 MC HDGV LDDV LDDT HDDV total

Arterial 10,385 7,258 4,281 155 440 1 2 127 22,651

Interstate 6,332 4,398 2,610 97 261 0 1 66 13,766

Intrazonal 16 11 6 0 1 0 0 0 35

Local 1,604 1,115 659 33 106 0 0 31 3,548

Ramp 732 488 286 9 25 0 0 8 1,547

CO 

 total 19,068 13,270 7,843 294 833 1 4 232 41,547

Arterial 681 425 264 29 32 0 1 47 1,479

Interstate 360 229 141 16 16 0 1 21 783

Intrazonal 1 1 1 0 0 0 0 0 3

Local 120 74 47 5 7 0 0 10 263

Ramp 42 25 16 2 2 0 0 3 90

VOC 

 total 1,204 754 468 51 56 0 2 81 2,617

Arterial 499 394 309 21 71 0 2 611 1,907

Interstate 293 230 177 13 42 0 1 460 1,218

Intrazonal 1 1 0 0 0 0 0 1 3

Local 82 64 50 3 9 0 0 94 302

Ramp 32 24 20 1 4 0 0 31 112

NOx 

 total 906 713 556 38 126 0 4 1,197 3,541

 

1

 Email from Mark Harrington, Southwest Regional Transportation Council to Sally Otterson, 

Washington State Department of Ecology. ADVMT estimates for 2000. June 6, 2003. 

2

 ADVMT estimates for 2015 from Mark Harrington, Southwest Regional Transportation 

Council. Database date August 20, 2003. 

3

 Hertzog, Barbara and Borden, Hank. Adjustment Factors for Vehicle Miles Traveled. Washington 

State Department of Transportation. July 1992. 

4

 Annual Traffic Report. Washington State Department of Transportation. Pages XVI - XX (monthly 

traffic count data). 1994 data report. 

5

 MOBILE6.2. US Environmental Protection Agency. Model executable file dated September 24, 2003. 

6

 Department of Licensing electronic data. Database snapshot July 2002. 

7

 National Transit Database Data Tables. Tables titled Age Distribution of Active Revenue 

Vehicle Inventory: Details by Transit Agency Directly Operated Service. Federal Transit 

Administration. Data tables for 2002 and 2003. 

http://www.ntdprogram.com/NTD/ntdhome.nsf/Docs/NTDPublications?OpenDocument# 

8

 Spreadsheet schoolbuses2001.xls. Registration data provided by the Puget Sound Clean Air 

Agency. 

9

 Spreadsheet schoolbuses2004.xls (originally titled Buses for DOE 24Aug04.xls). Transmitted 

from Allan J. Jones, Director of Pupil Transportation and Traffic Safety Education, Office of 

Superintendent of Public Instruction to Michael Boyer, WA Department of Ecology on Sept. 

28, 2004. 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

 10 Hellman, Karl H. and Heavenrich, Robert M. Light-Duty Automotive Technology and Fuel 

Economy Trends: 1975 Through 2004. Advanced Technology Division, Office of 

Transportation and Air Quality, U.S. Environmental Protection Agency. EPA420-R-04-001. 

April 2004. 

11 Climatological Data, Washington. January - December 2002. Volume 106, Numbers 01 - 12. 

ISSN 0364-5320. National Oceanic and Atmospheric Administration. National 

Environmental Satellite, Data and Information Service. National Climatic Data Center, 

Asheville, NC. 

12 Temperature Determination. Guidance distributed at the MOBILE4.1 Workshop, EPA 

Region X, November 1991. 

13 Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources. EPA-450/4-81-

026d (Revised). 1992. Section 3.3.5 Correction Factors. 

14 Supplement to the State Implementation Plan for Ozone (O3) in Vancouver, WA. 

Redesignation Request for Portland/Vancouver as Attainment for Ozone. Southwest Air 

Pollution Control Authority (now Southwest Clean Air Agency). March 19, 1996. 

15 Western Climatic Data Center, Western US Climate Historical Summaries, Local Climate Data 

Summaries (June 20, 1997). 

16 Spreadsheet Rel_hum1.xls. U.S. Environmental Protection Agency. Spreadsheet dated Jan 

16, 2002. 

17 40 CFR 80.27. 

18 Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources. EPA-450/4-81-

026d (Revised). 1992. Section 3.3.3 RVP Determination. 

19 John Raymond, during 1990 base year State Implementation Plan efforts. 

20 Memo from Philip Heirigs and Joe Roeschen, Sierra Research to Alison Pollack, ENVIRON 

International Corporation. Subject: Development of Calendar Year 2002 County-Level Fuel 

Specification Data for the WRAP Modeling Domain. Dec. 14, 2004. 

21 Spreadsheet of seasonal fuel RVP, sulfur and oxygen levels titled 

WRAP_Fuel_2002_toEnviron_121404.xls. Sierra Research. 

22 IM Compliance Rate. Audit of Vehicles with July 1998 Expiration Date. Department of Ecology Air 

Quality Program. Aug. 4, 1999. 

23 1999/2000 Emission Test Data for Washington State - (Puget Sound, Spokane, Vancouver) - GVW < 

8501. Washington State Department of Ecology. March 20, 2002. 

24 personal conversations with John Raymond, Department of Ecology. 

25 User's Guide to MOBILE6.0 Mobile Source Emission Factor Model. United States Environmental 

Protection Agency. Air and Radiation. EPA420-R-02-001. January 2002. 

26 May also generate factors for Interstates and Ramps combined. 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

2 Nonroad Mobile Sources, Excluding Ships, Locomotives, and 

Aircraft 

Nonroad sources include gasoline, diesel, compressed natural gas (CNG) and liquefied 

petroleum gas (LPG) fueled equipment. EPA's NONROAD2004 model was used to estimate 

emissions.27 The model estimates emissions for 11 categories: 

Agricultural Industrial Logging 

Airport Lawn/Garden (Commercial) Pleasure Craft 

Commercial Lawn/Garden (Residential) Railroad 

Construction/Mining Recreational 

2.1 Activity Level, Emission Rates, and Temporal Allocation 

The NONROAD2004 model was used to calculate emissions for Clark County. The 

NONROAD2004 model can estimate emissions for USA counties for the years 1970 through 

2050. Baseline equipment characteristics in the NONROAD2004 model are based on 1996-2000 

data. To estimate future year projections, the model includes growth and scrappage rates for 

equipment in addition to a variety of control program options. The model can calculate 

emissions for each of the four seasons. Emissions for the period selected are estimated either for 

the total period or for a typical day (weekday or weekend) in that period. For this inventory, 

annual emissions were calculated by summing period emissions for each of the four seasons. 

Daily emissions were calculated as summer weekday emissions. 

In addition to the county and time period, NONROAD2004 requires seasonal information on 

minimum, maximum and ambient temperatures. Ambient temperature is defined as: {min + [2/3 

x (max-min)]}.13 The model also requires fuel RVP, sulfur content, and fuel control programs. 

The meteorological and RVP parameter values are shown in Table 8 (see Onroad Mobile 

Sources above). 

Diesel fuel sulfur values content came from the NONROAD2004 diesel sulfur file (sulfur.txt). 

Values were available for the years 2000 – 2040. Gasoline sulfur content for 2002 came from 

the onroad model MOBILE6.2 and was 279 ppm. Gasoline sulfur for 2015 is the legal limit of 

30 ppm. The NONROAD2004 model default template sulfur value of 30 ppm was used for 

CNG/LPG. To be conservative, no stage 2 control was assumed. Fuel sulfur values are shown 

in Table 18. 

Table 18: NONROAD2004 Fuel Sulfur Parameters 

Fuel 2002 Sulfur % 2015 Sulfur %

Gasoline 0.0279 0.0030

Diesel 0.2283 0.0011

LPG/CNG 0.003 0.003

2.2 Emissions 

Annual and ozone season day emissions are shown below. Annual emissions are in tons per year 
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

and seasonal emissions are in pounds per day. 

Table 19: Nonroad Emissions, 2002 

CLASSIFICATION Tons per year Pounds per weekday 

VOC CO NOx VOC CO NOx 

Agricultural 7 59 50 90 771 636

Airport 0 0 0 0 3 2

Commercial 171 4,398 128 1,108 29,881 760

Construction/Mining 191 1,584 1,050 2,081 17,944 11,455

Industrial 104 1,646 431 785 12,763 3,207

Lawn/Garden (Commercial) 615 9,012 101 6,196 111,049 1,058

Lawn/Garden (Residential) 306 4,941 33 2,394 43,173 219

Logging 29 186 46 183 1,232 290

Pleasure Craft 128 312 10 801 1,654 49

Railroad 1 11 4 6 81 26

Recreational 199 1,143 9 1,477 8,926 56

 TOTAL 1,751 23,292 1,862 15,122 227,476 17,760
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

Table 20: Nonroad Emissions, 2015 

CLASSIFICATION Tons per year Pounds per weekday 

VOC CO NOx VOC CO NOx 

Agricultural 4 47 35 48 622 440

Airport 0 0 0 0 2 1

Commercial 122 6263 109 821 42,618 648

Construction/Mining 97 1300 577 1,061 14,856 6,296

Industrial 16 348 117 116 2,679 852

Lawn/Garden (Commercial) 366 11136 86 3,455 137,770 909

Lawn/Garden (Residential) 187 6419 29 1,481 56,342 191

Logging 19 246 12 118 1,646 77

Pleasure Craft 73 312 14 526 1,648 68

Railroad 1 12 3 5 85 21

Recreational 192 1641 11 1,449 12,781 70

 TOTAL 1,076 27,725 994 9,080 271,049 9,571
Prepared by Washington DOE’s Sally Otterson, May 31, 2006 sw03maint_rev

 

27 NONROAD2004, version 2.3c. April 2004. 

13 Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources. EPA-450/4-81-

026d (Revised). 1992. Section 3.3.5 Correction Factors