Portneuf Valley PM10 Maintenance Plan 

Amendment

Transition from MOBILE6 Model to MOVES Model

and to Revise Road Dust Methodology

State of Idaho 

Department of Environmental Quality

April 2014
Printed on recycled paper, DEQ, April 2014, PID

PVAB, CA 61068. Costs associated with this 

publication are available from the State of Idaho 

Department of Environmental Quality in accordance 

with Section 60-202, Idaho Code.
Portneuf Valley PM10 Maintenance Plan 

Amendment

Transition from MOBILE6 Model to MOVES Model

and to Revise Road Dust Methodology

April 2014

Prepared by

Idaho Department of Environmental Quality

Pocatello Regional Office

444 Hospital Way, #300

Pocatello, Idaho 83201
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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

iii

Table of Contents

Acronyms, Abbreviations, and Symbols ........................................................................................ v

Introduction..................................................................................................................................... 1

Background..................................................................................................................................... 1

Emission Calculations..................................................................................................................... 2

Description of Modeling Used........................................................................................................ 2

Planning Assumptions .................................................................................................................... 3

Existing MVEB............................................................................................................................... 3

Input Data........................................................................................................................................ 4

Budgets and Safety Margins........................................................................................................... 4

Revised MVEB for the Period 2011–2020 ..................................................................................... 5

Emission Inventory Growth and Control Assumptions Unchanged............................................... 6

Conclusion ...................................................................................................................................... 6

References....................................................................................................................................... 7

Appendix A. Development of the Year 2011 and Year 2020 Mobile Source Emissions 

Inventories and Conformity Test for the Portneuf Valley Nonattainment Area, Idaho 

Appendix B. Procedure for Revising MVEBs for PVNAA to Reflect MOVES and Paved 

Road Dust Model Changes

Appendix C. 2004 SIP Emission Inventory with Updated On-road Mobile Emissions 

Appendix D. Public Involvement

List of Tables

Table 1. Existing MVEB established in 2004 PVNAA SIP. .......................................................... 3

Table 2. Comparison of 2013 on-road emissions with existing 2004 MVEBs in terms of net 

PM10, including primary and secondary particulate, assuming 100% NOx conversion... 5

Table 3. Revised motor vehicle emission budgets for the PVNAA. .............................................. 6
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

v

Acronyms, Abbreviations, and Symbols

ATR automatic traffic recorder

AP-42 Compilation of Air Pollutant Emission Factors

BTPO Bannock Transportation Planning Organization

EPA United States Environmental Protection Agency

FR Federal Register

DEQ Idaho Department of Environmental Quality

ITD Idaho Transportation Department

MOBILE6 Vehicle Emissions Modeling Software

MOVES Motor Vehicle Emission Simulator

MVEB motor vehicle emissions budget

NAAQS National Ambient Air Quality Standards

NEI National Emission Inventory

NH4NO3 ammonium nitrate

NOx nitrogen oxides

PM2.5 particulate matter under 2.5 microns in size

PM10 particulate matter under 10 microns in size

PVNAA Portneuf Valley Nonattainment Area

SIP State Implementation Plan

TDM Travel Demand Model

TIP Transportation Improvement Program

TPY tons per year

VOC volatile organic compounds
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

vi

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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

1

Introduction

The purpose of this amendment is to revise the Portneuf Valley PM10 Nonattainment Area State 

Implementation Plan, Maintenance Plan, and Redesignation Request (DEQ 2004) motor vehicle 

emissions budget (MVEB) by incorporating emission estimates made with the Motor Vehicle 

Emission Simulator (MOVES), the latest United States Environmental Protection Agency 

(EPA)-required motor vehicle emissions factor model (EPA 2009, 2011a) and with an updated 

road dust estimation method (EPA 2011b). The revisions in this amendment only change 

emission related to the MVEB and no changes are made to the point or area source emissions.

Currently, the area’s existing MVEB is based on the MOBILE5 model, the predecessor to the 

MOVES model and an old (1995) road dust estimation method (EPA 1995). This amendment 

updates the MVEB submitted with the original State Implementation Plan (SIP), approved by 

EPA in July 2006, using these latest EPA-approved methods, which are now required for 

conformity demonstrations. No change in activity or control measures is included; this is simply 

a change to the latest EPA-mandated road dust and on-road mobile emissions methods/model, 

and the most current planning assumptions. The updated MVEB is demonstrated to be equivalent 

to the MVEB in the 2004 SIP in terms of particulate matter under 10 microns in size (PM10)

contribution to the airshed.

Background

In areas that are not meeting the National Ambient Air Quality Standards (NAAQS), the Clean 

Air Act requires the state to develop a SIP containing emission control measures to reduce 

emissions enough to return the area to compliance with NAAQS. As part of developing control 

measures, a MVEB is developed that sets emission limits for all current and future transportation 

projects. Once the MVEB is established in the SIP, Metropolitan Planning Organizations 

estimate the regional vehicle emissions from all the local proposed road projects in the 

Transportation Improvement Program (TIP) and compare those emissions with the SIP’s MVEB. 

This process is known as transportation conformity. 

In March 2013, MOVES replaced MOBILE6 as EPA’s official motor vehicle emissions factor 

model required for all regional emission analysis in support of transportation conformity. The 

Bannock Transportation Planning Organization (BTPO) addresses the MVEB for the Portneuf 

Valley attainment area. 

In general, the MOVES model calculates higher nitrogen oxides (NOx) and particulate matter

under 2.5 microns in size (PM2.5) emissions than the previous MOBILE6 model when the 

activity levels are held constant. Because of the higher emissions estimates resulting from 

MOVES, it is difficult to show conformity with SIPs that contain MVEB developed using 

MOBILE6, even when there has been no increase in actual emissions.
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

2

Emission Calculations

EPA approved the Portneuf Valley PM10 maintenance plan and designated the area in attainment

on July 13, 2006 (71 FR 39574). This approved plan established MVEBs for on-road sources. 

DEQ has updated the existing MVEBs in the PM10 maintenance plan for the Portneuf Valley

using the newer EPA-approved emissions model (MOVES2010b) and the latest paved road dust 

emission method as detailed in AP-42. This amendment to the SIP will revise the MVEBs to 

reflect both new methods now required by EPA. 

In addition to the on-road mobile emissions estimated by the MOBILE6/MOVES models, paved 

road dust PM10 emissions are included in the MVEB. The 2004 SIP attainment demonstration 

used to establish the existing MVEB included paved road dust estimates made using EPA’s 1996

AP-42 emission estimation guidance and incorporated locally determined road silt loading 

information developed in a 1996/1997 study by Light (1998).

In January 2011, EPA revised its AP-42 paved road dust estimation method (EPA 2011b), and 

DEQ used the new estimation guidance to update estimates of paved road dust emissions. A 

survey of the Pocatello and Chubbuck city road departments indicated that major changes in the 

use of wintertime antiskid treatments occurred between 1997 and 2012, including higher salt-tosand ratios in the antiskid treatments, pre storm brine application to reduce the amount of 

antiskid materials required, and a greater number of sweepers to clean up the antiskid materials 

that are used (Appendix A). Based on this survey, silt loadings based on traffic volume were 

used as recommended by EPA (EPA 2011b) to account for wintertime antiskid treatment rather 

than the silt loading measured in the area 15 years earlier. As a result of the reduced sand usage 

and the updated emission estimation methods, a significant reduction in paved road dust is 

estimated for years 2011 and 2020. The paved road dust reductions are greater than the increase 

in direct exhaust PM10 and secondary PM10 due to precursor NOx that occurred when MOVES 

replaced MOBILE6. The net effect is a reduced on-road mobile emissions inventory.

Description of Modeling Used 

On March 2, 2010, EPA released a new mobile source emissions model called the Motor 

Vehicles Emissions Simulator 2010 (MOVES2010). The EPA provided a 2-year grace period to 

transportation planning organizations, ending March 2, 2012, during which the older MOBILE6

emissions could still be used to model emissions for transportation projects to meet the 

requirements of transportation conformity (75 FR 9411). 

On October 13, 2011, EPA proposed a 1-year extension to the 2-year grace period because states 

and localities needed more time to transition to using MOVES2010a and to develop the technical 

capacity to use MOVES2010a (76 FR 63575). EPA finalized the extension on February 27, 2012 

(77 FR 11394). The 1-year extension provides additional time that may be critical for 

nonattainment and maintenance areas to learn and apply MOVES2010a for regional conformity 

analyses. Any new transportation conformity analysis started after March 2, 2013, must use the 

MOVES model.
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

3

The EPA issued the MOVES2010b version of the model and its associated guidance in 

April 2012, and it is the version in effect throughout the period of this SIP revision analysis and 

is the version used by DEQ.

Planning Assumptions

To operate the MOVES model at the county-level as required by EPA for SIP-level emission 

inventories, DEQ developed an input database for each specific combination of inputs. This 

section discusses the assumptions, sources of input information, and calculation methodologies 

involved in developing SIP-level MOVES input databases.

In November 2012, DEQ completed statewide on-road emission estimates in support of the 2011 

National Emission Inventory (NEI). This comprehensive project (DEQ 2012) gathered detailed 

information from the statewide motor vehicle registration database to describe the motor vehicle 

source population (ITD 2012a) and traffic counts by vehicle length from every permanent 

automatic traffic recorder (ATR) in the state (ITD 2012b). In addition, telephone and e-mail 

surveys filled in the bus and refuse truck source population data that may be unreliable in the 

registration database and in the national defaults. In view of this SIP-level detail in the NEI 

MOVES inputs, the Bannock County source population and temporal profiles developed for the 

NEI were used along with BTPO’s Travel Demand Model (TDM) for the Portneuf Valley 

Nonattainment Area (PVNAA) (Parsons 2012) to develop local inputs for the Portneuf Valley. 

The use of the Bannock County inputs from the NEI statewide database, which was extensively 

quality assured and found to be consistent with other counties in Idaho of similar population 

ensures that the Portneuf Valley results are robust and internally consistent with the rest of Idaho.

Existing MVEB

The 2004 PVNAA SIP established MVEB for 2005, 2010, and 2020 (DEQ 2004). The existing 

MVEBs were developed consistent with the emissions inventory and attainment demonstration 

that showed future compliance with NAAQS for PM10. The existing MVEBs established in the 

2003 SIP are shown in Table 1.

Table 1. Existing MVEB established in 2004 PVNAA SIP.

Year PM10 (TPY) NOx (TPY) VOC (TPY)

2005 897 1,575 983

2010 1,120 1,085 716

2020 1,364 514 585

Notes: motor vehicle emission budget (MVEB); Portneuf Valley Nonattainment Area 

(PVNAA); State Implementation Plan (SIP); particulate matter with a diameter less 

than 10 microns (PM10); tons per year (TPY); nitrogen oxides (NOx); volatile organic 

compound (VOC)

The existing budgets include on-road mobile emissions computed using MOBILE6, paved road 

dust emissions computed using the 1995 version of the AP-42 paved road dust emission factor 

methodology that incorporated locally determined silt loading factors, and a small amount of 
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

4

unpaved road dust emissions from the few remaining unpaved roads in the area. No significant 

unpaved roads remain in the PVNAA in 2013.

Input Data

The on-road mobile emission inventory for the PVNAA was updated for 2011 and 2020 as 

described in Appendix A (DEQ 2013). Emissions estimates for 2010 were not made because (a) 

2010 had passed and conformity for 2010 and prior years was already completed using 

MOBILE6, and (b) newer information was available for 2011 as a result of the 2011 NEI project. 

DEQ used SIP-quality, county-level MOVES inputs for the 2011 NEI so that it would be 

adequate for SIP documentation purposes. Early in 2013, DEQ updated the 2011 NEI inputs to 

reflect activity data from the Portneuf Valley TDM developed by BTPO. As a result, the more 

recent 2011 emissions will be used to replace the existing 2010 MVEBs since 2010 is no longer 

of interest and the recent model year is more relevant and timely. The SIP-level MOVES inputs 

developed for the 2011 NEI include source population data from the Idaho Department of Motor 

Vehicles, traffic temporal information from permanent ATRs, and bus and refuse truck local 

survey information (DEQ 2013).

Budgets and Safety Margins

The following demonstrates that the revised MVEB resulting from EPA-mandated changes in the 

on-road and paved road dust emission models results in lower net PM10 in the airshed. 

It should be noted that actual on-road activity levels are not changing significantly beyond 

normal growth, and this demonstration reflects only changes in the estimated AP-42 road dust 

emissions and in the on-road mobile modeling emission estimates. This section and Appendix B 

describe how DEQ calculated the overall net effect of these emission calculation changes for 

total PM10. 

The net effective PM10 contribution is the combination of direct PM10 emissions plus the NOx

that has been converted to the secondary aerosol composed of ammonium nitrate (NH4NO3). 

Since the actual conversion rate of NOx to NH4NO3 cannot be estimated without difficult and 

time-consuming photochemical modeling, DEQ followed the most conservative possible 

approach and estimated 100% conversion. Since VOCs only act similar to a catalyst in

facilitating the NH4NO3 formation chemistry and do not directly form new PM10 separate from 

the nitrate formation, they are not included in calculating the net effective PM10 contribution to 

the airshed (Appendix B). Table 2 shows the comparison of total PM10 (direct PM10 + 100% 

conversion of NOx to NH4NO3) using the existing MVEB in the 2004 SIP and a MVEB 

developed in 2013 with MOVES and the new AP-42 road dust calculations. The 2013 estimates 

show an increase in secondary particulate formation and a decrease in direct PM10, but the total 

PM10 still remains below that in the existing 2010 and 2020 MVEBs from the SIP, which 

demonstrated compliance with the PM10 NAAQS.
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

5

Table 2. Comparison of 2013 on-road emissions with existing 2004 MVEBs in terms of net PM10, 

including primary and secondary particulate, assuming 100% NOx conversion.

Existing SIP MVEB 

with 100% NOx

Conversion Rate

2013 Estimates with 

100% NOx

Conversion Rate

Difference, Existing 

SIP MVEB—2013 

Estimates

Year 2010 2011 2010/2011

Secondary PM10 produced 

from NOx and VOC 2,745 3,347 -602

Primary PM10 1,120 382 738

Total PM10 3,865 3,729 136

Year 2020 2020 2020

Secondary PM10 produced 

from NOx and VOC 1,300 1,647 -347

Primary PM10 1,364 379 986

Total PM10 2,664 2,026 639

Notes: motor vehicle emission budget (MVEB); particulate matter with a diameter less than 10 microns (PM10); 

nitrogen oxides (NOx); State Implementation Plan (SIP); volatile organic compound (VOC)

If the updated emissions estimates are used directly as MVEBs, then minor model input 

differences in future conformity tests could potentially cause the TIP emissions estimates to 

exceed the updated budgets. To avoid this potential problem, safety factors are typically built 

into the MVEBs to the extent that can be tolerated while still demonstrating future year NAAQS 

compliance in the attainment demonstration, or in this case, while still showing equivalence with

the existing MVEB. 

It was determined a safety margin of 3.1% could be added to revised 2011 MVEBs and 31.5% 

could be added to the revised 2020 MVEBs without exceeding the total PM10 in the existing 

MVEBs. Since the existing SIP MVEB is consistent with an overall emission inventory and the 

approved attainment demonstration model showing future year compliance with the NAAQS 

(DEQ 2004), the revised model change MVEBs will remain consistent with the attainment 

demonstration as long as long as they are equivalent to the existing MVEBs in terms of the net 

PM10 quantity added to the airshed.

Revised MVEB for the Period 2011–2020

The analysis above demonstrates that model changes resulting from the use of the MOVEs2010b 

model and the 2011 AP-42 paved road dust method results in new MVEBs that are equivalent to 

the existing (2004 SIP) MVEBs in terms of PM10 contributions to the PVNAA airshed.

The resulting revised MVEB for this period is shown in Table 3. Conformity tests for any TIPs 

conducted from the approval of the MVEBs in this EIP revision through 2019 will be required to 

meet the budget shown for 2011. This is a conservative budget because, as noted in Appendix B,

the 2011 MVEB includes the maximum (2011) MOVES direct PM10 emissions plus the 

maximum (2020) paved road dust emissions for the period. Any TIP conducted in 2020 and 

beyond will be required to meet the budget shown for 2020. 
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

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Table 3. Revised motor vehicle emission budgets for the PVNAA.

Year PM10 (TPY) NOx (TPY) VOC (TPY)

2005 N/A N/A N/A

2011 415 1,364 903

2020 498 856 651

Notes: Portneuf Valley Nonattainment Area (PVNAA); particulate 

matter with a diameter less than 10 microns (PM10); tons per year 

(TPY); nitrogen oxides (NOx); volatile organic compound (VOC); 

not applicable (N/A)

Emission Inventory Growth and Control Assumptions 

Unchanged

This report demonstrates that MVEBs updated using MOVES and the 2011 road dust 

methodology are equivalent to the existing MVEBs in the 2004 SIP. The other portions of the 

emissions inventory are unchanged by this modification, and the growth and control strategy 

assumptions used in the 2004 SIP are still valid. The emissions inventory developed for the 2004 

SIP is reproduced in Appendix C, with the new MVEBs provided for comparison. 

Control strategy assumptions for source categories other than on-road vehicle are not changed as 

part of this revision and are unchanged since the SIP was published in 2004. In addition, the 

growth assumptions used in the 2004 SIP to project emissions for the future years are still valid. 

The 2004 SIP analysis used the population growth from 1990 to 2000 (1.4% per year) to forecast 

population and household growth to the future year attainment dates, including 2010 and 2020, 

for generally all the anthropogenic area source categories. (Agriculture and stationary sources 

were assumed to remain level.) Subsequent census data indicate that combined population 

growth for Chubbuck and Pocatello, the population centers of the PVNAA, actually averaged 

1.2% per year between 2000 and 2010, and is estimated to average only 0.6% for each city in

2011 and 2012 (US Census 2013). This is lower than the growth rates assumed in the SIP to 

occur for every year after 2000. The cities of Chubbuck and Pocatello represent nearly the entire 

populated portion of the PVNAA, so it is clear that growth assumptions used in the 2004 SIP are 

still valid.

Conclusion

The revised MVEB included in Table 3 will apply to future transportation conformity 

determinations. With these proposed changes to the MVEB, the SIP will continue to show 

maintenance of the 24-hour PM10 standard because it is equivalent to the MVEB used in the 

2004 attainment demonstration. This SIP amendment will lead to an equitable and more relevant 

result when evaluating transportation impacts on the area’s air quality.
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

7

References

DEQ (Idaho Department of Environmental Quality). 2004. Portneuf Valley PM10 Nonattainment 

Area State Implementation Plan, Maintenance Plan and Redesignation Request.

Pocatello, ID: DEQ.

DEQ (Idaho Department of Environmental Quality). 2012. Development of the 2011 Paved Road 

Dust Inventory for the National Emission Inventory. Boise, ID: DEQ.

DEQ (Idaho Department of Environmental Quality). 2013. Development of the Year 2011 and 

Year 2020 Mobile Source Emissions Inventories for the Portneuf Valley Non-Attainment 

Area, Idaho. Boise, ID: DEQ.

EPA (United States Environmental Protection Agency). 1995. “Paved Road Dust.” Section 

13.2.1. Compilation of Air Pollutant Emission Factors. Washington, DC: Office of Air 

Quality Planning and Standards.

EPA (United States Environmental Protection Agency). 2009. Motor Vehicle Emission 

Simulator (MOVES) 2010: User Guide. Assessment and Standards Division, Office of 

Transportation and Air Quality, EPA-420-B-09-041. December 2009. 

EPA (United States Environmental Protection Agency). 2011a. MOVES (Motor Vehicle 

Emission Simulator). http://www.epa.gov/otaq/models/moves/index.htm.

EPA (United States Environmental Protection Agency). 2011b. “Paved Road Dust.” Section 

13.2.1. Compilation of Air Pollutant Emission Factors. Washington, DC: Office of Air 

Quality Planning and Standards.

ITD (Idaho Transportation Department). 2012a. Motor Vehicle Registration Database. Boise, 

ID: ITD Department of Motor Vehicles.

ITD (Idaho Transportation Department). 2012b. Automatic Traffic Recorder Database 

(Statewide, Raw Data). Boise, ID: ITD Department of Motor Vehicles.

Light, J. 1998. Pocatello Road Dust Study Final Report. Prepared for Bannock Transportation 

Planning Organization. Pocatello, ID.

Parsons (Parsons Brinkerhoff, PB Americas, Inc.). 2012. BTPO Travel Model User’s Guide.

Prepared for Bannock Transportation Planning Organization (Pocatello, ID). Portland, 

OR: Parsons.

US Census (United States Census Bureau). 2013. Annual Estimates of the Resident Population: 

April 1, 2010 to July 1, 2012. Washington, DC: United States Department of Commerce. 

Accessed December 2013. 

http://factfinder2.census.gov/bkmk/table/1.0/en/PEP/2012/PEPANNRES/0400000US16.1

6200
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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

Appendix A. Development of the Year 2011 and Year 2020 

Mobile Source Emissions Inventories and 

Conformity Test for the Portneuf Valley 

Nonattainment Area, Idaho
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

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Development of the Year 2011 and Year 2020 

Mobile Source Emissions Inventories and 

Conformity Test for the Portneuf Valley 

Nonattainment Area, Idaho

December 2013

Prepared by

Idaho Department of Environmental Quality

Technical Services Division

1410 N. Hilton

Boise, ID 83706
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iii

Table of Contents

Abbreviations, Acronyms, and Symbols ........................................................................................ v

1 Introduction.............................................................................................................................. 1

2 Methodology: MOVES Input Database Development............................................................ 1

2.1 VMT-Related Inputs......................................................................................................... 4

2.1.1 Annual VMT............................................................................................................. 4

2.1.2 Road Type................................................................................................................. 5

2.1.3 Monthly, Daily, and Hourly VMT............................................................................ 5

2.2 Source-Related Inputs ...................................................................................................... 6

2.2.1 Source Type Population............................................................................................ 6

2.2.2 Age Distribution........................................................................................................ 7

2.3 VHT-Related Inputs ......................................................................................................... 7

2.3.1 Ramp Fractions......................................................................................................... 8

2.3.2 Average Speed Distribution...................................................................................... 8

2.4 Fuel-Related Inputs .......................................................................................................... 9

2.4.1 Fuel Supply ............................................................................................................... 9

2.4.2 Fuel Formulation..................................................................................................... 10

2.4.3 Alternative Vehicle Fuels and Technology............................................................. 10

2.5 Meteorology ................................................................................................................... 10

2.6 Inspection and Maintenance Programs........................................................................... 10

2.7 On-Road Retrofits .......................................................................................................... 11

3 Methodology: Paved Road Dust............................................................................................ 11

3.1 Vehicle Miles Traveled .................................................................................................. 12

3.2 Road Dust Emission Factor............................................................................................ 12

3.2.1 Particle Size Multipliers.......................................................................................... 13

3.2.2 Silt Loading............................................................................................................. 13

3.2.3 Average Vehicle Weight by Roadway Type .......................................................... 14

3.2.4 Precipitation Data.................................................................................................... 15

4 Results.................................................................................................................................... 15

4.1 On-Road Mobile Source Emission Estimates ................................................................ 15

4.2 Paved Road Dust Emission Estimates............................................................................ 16

5 Quality Control and Quality Assurance................................................................................. 16

References..................................................................................................................................... 17

Appendix A. Crosswalk between BTPO TDM Road Types, FHWA Roadway Types, and 

MOVES Roadway Types.............................................................................................................. 19

Appendix B. Crosswalk between ATR Length Bins, FHWA Vehicle Classes, and MOVES 

Source Types................................................................................................................................. 20

Appendix C. ITD Statewide Vehicle Classification Data............................................................. 21
iv

List of Figures

Figure 1. Motor Vehicle Emission Simulator input files and groups. ............................................ 3

List of Tables

Table 1. Idaho county groups for MOVES modeling purposes...................................................... 2

Table 2. MOVES road type descriptions. ....................................................................................... 4

Table 3. MOVES source type descriptions..................................................................................... 4

Table 4. Travel Demand Model-based annual vehicle miles traveled............................................ 5

Table 5. Crosswalk between MOVES source types and data sources for source-related 

MOVES input parameters................................................................................................... 6

Table 6. MOVES speed bins........................................................................................................... 8

Table 7. Roadway type definitions in road dust calculation......................................................... 12

Table 8. Silt loadings used for paved road emission factor calculation........................................ 14

Table 9. Antiskid improvements to lower silt loadings in Pocatello and Chubbuck.................... 14

Table 10. Average vehicle weight by vehicle type. ...................................................................... 15

Table 11. Number of days with greater than 0.01 inches of precipitation for each month in 

2011................................................................................................................................... 15

Table 12. Annual on-road emissions in PVNAA.......................................................................... 16

Table 13. Annual paved road dust emissions in PVNAA............................................................. 16

List of Equations

Equation 1. Equation used to estimate vehicle population for source types without local data. .... 7

Equation 2. Equation used to estimate vehicle population for 2020............................................... 7

Equation 3. Akcelik volume delay function. .................................................................................. 9

Equation 4. Paved road dust emission factor. ............................................................................... 12

Equation 5. VMT-weighted silt loading. ...................................................................................... 13
v

Abbreviations, Acronyms, and Symbols

ADT average daily traffic

ATR automatic traffic recorder

AVFT alternative vehicle fuels and technology

BTPO Bannock Transportation Planning Organization

CO carbon monoxide

DEQ Idaho Department of Environmental Quality

DMV Idaho Department of Motor Vehicles

E10 fuel blend of 10% ethanol and 90% gasoline

EPA United States Environmental Protection Agency

FHWA Federal Highway Administration

HPMS Highway Performance Monitoring System

I/M inspection and maintenance

ITD Idaho Transportation Department

MOVES Motor Vehicle Emissions Simulator

mph miles per hour

MVEB motor vehicle emission budget

NEI National Emission Inventory

NH3 ammonia

NOx nitrogen oxides

PM10 particulate matter with a diameter less than 10 microns

PM2.5 particulate matter with a diameter less than 2.5 microns

PVNAA Portneuf Valley Nonattainment Area

SIP State Implementation Plan

SO2 sulfur dioxide

TDM Travel Demand Model

TVRDS Treasure Valley Road Dust Study

VHT vehicle hours traveled

VIN vehicle identification number

VMT vehicle miles traveled

VOC volatile organic compound
vi

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1

1 Introduction

On-road mobile emission inventories for the Portneuf Valley Nonattainment Area (PVNAA) are 

required for the State Implementation Plan (SIP) ten-year update documentation and for future 

conformity determinations to be made by the Bannock Transportation Planning Organization 

(BTPO), the metropolitan planning organization for Bannock County, Idaho. While current 

motor vehicle budgets established by the current SIP for particulate matter with a diameter less 

than 10 microns (PM10) (DEQ 2004) were developed using the MOBILE motor vehicle 

emissions model, all future SIP documentation and conformity determinations after March 2, 

2013, must be developed using the United States Environmental Protection Agency’s (EPA’s)

new Motor Vehicle Emission Simulator (MOVES) model. The purpose of the PVNAA on-road 

emission inventory described in this report is to support the SIP maintenance plan ten-year 

update and conformity determinations to be made after March 2, 2013. Conformity 

determinations made prior to March 2, 2013, must be made using the same methodologies used 

to develop the motor vehicle emission budgets (MVEB) currently in effect as established in the 

2004 Portneuf Valley PM10 State Implementation Plan, Maintenance Plan, and Redesignation 

Request (DEQ 2004).

The Motor Vehicle Emissions Simulator (MOVES2010b) (EPA 2011a) is the current EPAdesignated model for on-road mobile emission inventory development for SIP maintenance plans 

and for Federal Highway Administration (FHWA) transportation conformity determinations. The 

on-road mobile source emissions inventory was developed using MOVES2010b according to

EPA guidance Using MOVES to Prepare Emission Inventories in State Implementation Plans 

and Transportation Conformity: Technical Guidance for MOVES2010, 2010a and 2010b (EPA 

2012).

The paved road dust emissions were developed using the latest EPA-recommended AP-42,

Compilation of Air Pollutant Emission Factors method (EPA 2011b). There are no significant 

unpaved roads in the PVNAA, thus unpaved road emissions were not estimated.

This report details the methodologies and results for the MOVES on-road emissions modeling and 

paved road dust computations used to develop the 2011 and 2020 on-road emission inventories. 

2 Methodology: MOVES Input Database Development

To operate the MOVES model at the county-level as required by EPA for SIP-level emission 

inventories, the Idaho Department of Environmental Quality (DEQ) developed an input database 

for each specific combination of inputs. This section discusses the assumptions, sources of input 

information, and calculation methodologies involved in developing SIP-level MOVES input 

databases.

In November 2012, DEQ completed statewide on-road emission estimates in support of the 2011 

National Emission Inventory (NEI). This comprehensive project (DEQ 2012) gathered detailed 

information from the statewide motor vehicle registration database to describe the motor vehicle 

source population and traffic counts by length from every permanent automatic traffic recorder 

(ATR) in the state. In addition telephone and e-mail surveys filled in the bus and refuse truck 

source population data that may be unreliable in the registration database and in the national 
2

defaults. In view of this SIP-level detail in the NEI MOVES inputs, the Bannock County source 

population and temporal profiles developed for the NEI were used along with BTPO’s Travel 

Demand Model (TDM) (Parsons 2012) to develop local inputs for the PVNAA. The use of the 

Bannock County inputs from the NEI statewide database, which was extensively quality assured 

and found to be consistent with other counties in Idaho of similar population ensures that the 

PVNAA results are robust and internally consistent with the rest of Idaho.

Based on similarity of geographic features, vehicle travel patterns, and data sources, DEQ 

grouped all 44 Idaho counties into three groups: Northern Idaho, Southern Idaho, and Treasure 

Valley to use the ATR data in developing the statewide 2011 NEI inputs (Table 1). A majority of 

PVNAA resides in Bannock County and belongs to the southern Idaho group. Because all of the

urban southern Idaho group ATR sites except one reside in PVNAA and nearly all roads in 

PVNAA are urban roads, the southern Idaho group ATR data represent PVNAA very well.

Table 1. Idaho county groups for MOVES modeling purposes.

County

Group

County

ID

County

Name

County

Group County ID County Name

Northern

Idaho

16009 Benewah

Southern

Idaho 

(continued)

16031 Cassia

16017 Bonner 16033 Clark

16021 Boundary 16037 Custer

16035 Clearwater 16039 Elmore

16049 Idaho 16041 Franklin

16055 Kootenai 16043 Fremont

16057 Latah 16045 Gem

16061 Lewis 16047 Gooding

16069 Nez Perce 16051 Jefferson

16079 Shoshone 16053 Jerome

Treasure 

Valley

16001 Ada 16059 Lemhi

16027 Canyon 16063 Lincoln

Southern

Idaho

16003 Adams 16065 Madison

16005 Bannock 16067 Minidoka

16007 Bear Lake 16071 Oneida

16011 Bingham 16073 Owyhee

16013 Blaine 16075 Payette

16015 Boise 16077 Power

16019 Bonneville 16081 Teton

16023 Butte 16083 Twin Falls

16025 Camas 16085 Valley

16029 Caribou 16087 Washington

Note: Motor Vehicle Emission Simulator (MOVES)

The required MOVES inputs, grouped by common data source, are shown in Figure 1. For 

example, VMT Related inputs such as road type distribution and monthly, daily, and hourly 

traffic profiles (top box) require detailed information from the Idaho Transportation Department 

(ITD) traffic counts and vehicle miles traveled (VMT) statistics to characterize the VMT within 

the modeling domain, while the Source Related inputs are derived primarily from the statewide 

vehicle registration database. 
3

Figure 1. Motor Vehicle Emission Simulator input files and groups.

County-level input files were prepared for each category, using a combination of (primarily) 

local data and selected MOVES national defaults in those cases where local data are not 

available or are suspected to be less reliable. This section discusses the creation of each input in 

turn. The input files under discussion are listed after each section heading for clarification. For 

reference, MOVES road types and source types (vehicles) are defined in Table 2 and Table 3, 

respectively.
4

Table 2. MOVES road type descriptions.

Road Type Description

1 Off-network

2 Rural restricted access

3 Rural unrestricted access

4 Urban restricted access

5 Urban unrestricted access

Note: Motor Vehicle Emission Simulator (MOVES)

Table 3. MOVES source type descriptions.

MOVES 

Source Type Description

11 Motorcycle

21 Passenger car

31 Passenger truck

32 Light commercial truck

41 Intercity bus

42 Transit bus

43 School bus

51 Refuse truck

52 Single unit short-haul truck

53 Single unit long-haul truck

54 Motor home

61 Combination short-haul truck

62 Combination long-haul truck

Note: Motor Vehicle Emission Simulator (MOVES)

2.1 VMT-Related Inputs

VMT inputs describe the distance traveled on different roadways by the various source types 

(vehicles). VMT-related inputs include road type distribution and VMT (annual, monthly, daily, 

and hourly estimates). The road type VMT distribution data set was developed from the BTPO 

TDM, and the monthly, weekday/weekend, and hourly VMT profiles were developed from 

permanent ATRs.

2.1.1 Annual VMT

HPMSVTypeYear(HPMSVtypeID, yearID, HPMSBaseYearVMT, baseYearOffNetVMT)

Annual VMT describes the total vehicle miles traveled for each Highway Performance 

Monitoring System (HPMS) vehicle type, for each county in the domain. To generate the annual 

VMT inputs, ITD ATR data were used to generate a weekday/weekend ratio and fleet mix for 

each road type, which were then applied to BTPO TDM annual average weekday VMT outputs

to estimate annual VMT.

Comparing annual VMT attributed to local roads from the TDM output to ITD’s annual local 

road VMT from fuels sales data indicated that the TDM does not underestimate VMT from local 
5

roads (as TDMs often do). Thus, a local road scale-up factor of 1.00 was used (i.e., no VMT 

adjustment for the local roads). The final TDM-based VMT are summarized in Table 4. 

Table 4. Travel Demand Model-based annual vehicle miles traveled.

Year Vehicle Miles Traveled

2011 409,399,732

2020 454,338,514

2.1.2 Road Type

RoadtypeDistribution(sourceTypeID, roadTypeID, roadTypeVMTFraction)

The road type distribution describes the fraction of fleet miles driven on each of the four 

applicable MOVES road types (rural restricted, rural unrestricted, urban restricted, and urban 

unrestricted) within the modeling domain for each source (vehicle) type. Road type distribution 

inputs were derived from TDM outputs provided by BTPO and ITD ATR data. A crosswalk 

table in Appendix A shows the relationships between BTPO TDM road types, the HPMS/FHWA 

road types, and the MOVES roadway types. The ATR-based traffic data and TDM outputs were

used to allocate the annual VMT for each source type to road types. When the annual road 

distributions were complete for the FHWA road types, the distributions were aggregated into the 

four MOVES road types.

Year 2020 road type distribution was developed from the same ITD ATR data set along with 

year 2020 VMT from the TDM.

2.1.3 Monthly, Daily, and Hourly VMT

MonthVMTFraction(sourcetypeID, isLeapYear, monthID, monthVMTFraction)

DayVMTFraction(sourceTypeID, monthID, roadTypeID, dayID, dayVMTFraction)

HourVMTFraction(sourceTypeID, roadTypeID, dayID, hourID, hourVMTFraction)

Temporal distribution profiles further divided the source type annual VMT into finer time 

increments. Temporal profiles were derived from ATR data and annual VMT by FHWA road 

type based on BTPO’s TDM.

ATR data contain hourly vehicle counts for each of five length categories or bins. Hourly counts 

for each length bin were converted to temporal distributions for each MOVES vehicle type and 

roadway type using a crosswalk scheme developed based on discussions with ITD and 2009–

2011 Idaho statewide vehicle classification data (Scott Fugit, ITD, pers.comm. 2012). The final 

crosswalk table, which maps ATR length bins to MOVES vehicle types, is provided in Appendix 

B, and the 2009–2011 classification data are provided in Appendix C. Neither ATR data nor 

FHWA vehicle classification data distinguish between personal or commercial light-duty truck

trips, and long- or short-haul heavy duty truck trips, so it was necessary to use national default 

fractions available in the MOVES model to make the final splits from FHWA classes to MOVES 

vehicle types in these categories. For each ATR site, a full year of ATR data were processed. 

Hourly, weekday/weekend, and monthly statistics were calculated for each vehicle type. Finally, 

ATR sites were grouped based on MOVES road types, and each site was weighted equally in 

constructing the final temporal profiles.
6

Year 2020 temporal profiles for each road type were developed from the same ITD ATR data set

along with year 2020 VMT.

2.2 Source-Related Inputs

This group of inputs includes source type population and age distribution. Source-related inputs

describe and group the vehicles in the modeling domain and are compiled using a variety of data 

sources (Table 5). The fleet mix distribution is a key component of on-road mobile source 

emissions. The majority of vehicles are well characterized by the Idaho Department of Motor 

Vehicle (DMV) registration database (Bob Thompson, ITD, pers.comm. 2012). The database is 

screened to ensure that only vehicles with current registrations are included, and vehicle types 

and ages are obtained from the vehicle identification number (VIN) to avoid data entry errors 

that may occur in manually entered fields.

Table 5. Crosswalk between MOVES source types and data sources for source-related MOVES 

input parameters.

MOVES Source Type Source-Related Input Data Source

Motorcycle ITD—DMV registration database

Passenger car ITD—DMV registration database

Passenger truck ITD—DMV registration database

Light commercial truck ITD—DMV registration database

Intercity bus Telephone and e-mail survey

Transit bus Telephone and e-mail survey

School bus Idaho Department of Education

Refuse truck Telephone and e-mail survey, MOVES default database

Single unit short-haul truck MOVES default database, annual local VMT

Single unit long-haul truck MOVES default database, annual local VMT

Motor home ITD—DMV registration database

Combination short-haul truck MOVES default database, annual local VMT

Combination long-haul truck MOVES default database, annual local VMT

Notes: Idaho Motor Vehicle Emissions Stimulator (MOVES); Idaho Transportation 

Department (ITD); Idaho Department of Motor Vehicles (DMV); vehicle miles traveled 

(VMT)

2.2.1 Source Type Population

SourceTypeYear(yearID, sourceTypeID, sourceTypePopulation)

The source type population input describes the types and numbers of vehicles that make up the 

fleet. Six sources of data were used to develop the source type population inputs as shown in 

Table 5.

Direct population and age data were obtained from service providers via telephone and e-mail 

surveys for transit and intercity buses and refuse trucks. School bus data were obtained from the 

Idaho Department of Education. For motorcycle, passenger car, passenger truck, light 

commercial truck, and motor home source types, VIN-decoded registration data were used to 

determine vehicle populations.
7

For all other heavy duty truck source types many of the vehicles are registered in other states so 

local registration data are not complete, and therefore, the heavy duty truck populations are 

derived from MOVES national defaults. Thus, for single and combination haul trucks, a factor 

was used to estimate the county level source type populations using local activity data, MOVES 

national default activity data, and MOVES national default source type populations as shown in

Equation 1.

 

  (

 

 

 

 )

Equation 1. Equation used to estimate vehicle population for source types without local data.

The 2010 census indicates that 89.3% of the PVNAA human population resides in Bannock 

County. Thus, the Bannock County source type population from the 2011 NEI was adjusted 

using this human population ratio as surrogate to produce the PVNAA source type population. A 

very small, sparsely populated sliver of the PVNAA is located in Power County; however, this is 

a negligible portion of the total PVNAA population and that portion of the source population is 

also assumed to have similar characteristics to Bannock County.

DEQ assumed the “VMT per vehicle population” is approximately constant from year to year,

allowing 2020 source type populations to be estimated using Equation 2 shown below:

 

  (

 

 

 

 )

Equation 2. Equation used to estimate vehicle population for 2020.

2.2.2 Age Distribution

AgeDistribution(SourceTypeID, YearID, AgeID, AgeFraction)

Age distributions characterize the age profile of each vehicle source type. Age distributions were 

developed for Bannock County using VIN-decoded vehicle registration data, refuse truck, transit 

and intercity bus fleet data from service providers, school bus fleet data from the Idaho 

Department of Education, and MOVES defaults for heavy duty haul truck source types. Because 

the majority of PVNAA is in Bannock County, age distributions developed for Bannock County 

were used for PVNAA directly.

The same age distribution developed for 2011 was used for 2020, based on the approximation 

that age distribution do not change significantly from year to year.

2.3 VHT-Related Inputs

Vehicle hours traveled (VHT) inputs characterize the time spent and average speeds of vehicles 

travelling on specific road types. This group of inputs includes ramp fractions and average speed

distribution. 
8

2.3.1 Ramp Fractions

RampFraction(roadTypeID, rampFraction)

Ramp fraction defines the portion of VHT on roadways that contain entrance and exit ramps for 

restricted access roadways. Ramps are treated separately from the remainder of the freeway VHT 

because the sudden acceleration and deceleration that occurs on ramps results in significantly 

higher emissions.

Both 2011 and 2020 ramp fractions for urban freeways were calculated by aggregating VHT on 

ramps and restricted access roadways from the TDM outputs then dividing ramp VHT by total 

restricted access roadway VHT to get the fraction of restricted access VHT attributed to ramps.

2.3.2 Average Speed Distribution

AverageSpeedDistribution(sourceTypeID, roadTypeID, hourDayID, avgSpeedBinID, 

avgSpeedFraction)

The average speed distribution allocates the different source types (vehicles) for each roadway 

type to 16 speed bins ranging from 0 to >72.5 miles per hour (mph) (Table 6). This input reflects 

levels of congestion on roadways. Average speed distributions were developed from TDM 

average daily traffic counts for each roadway segment and hourly traffic count statistics 

developed from detailed ATR traffic count data provided by ITD. 

Table 6. MOVES speed bins.

avgSpeedBinID avgBinSpeed avgSpeedBinDesc

1 2.5 Speed <2.5 miles per hour (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

The hourly ATR-based traffic count profiles for each roadway type were used to estimate hourly 

volume on each segment. The Akcelik volume delay function (Equation 3) was then used to 

develop the average speed distribution database for each hour. This is the same volume delay 

function used in the BTPO’s TDM (Parsons 2012) so the emissions model is internally consistent 

with the TDM.
9

Equation 3. Akcelik volume delay function.

Both 2011 and 2020 average speed distributions were developed for all four MOVES road types 

using TDM outputs developed by BTPO and hourly temporal profiles based on the detailed ATR 

data provided by ITD.

2.4 Fuel-Related Inputs

This group of inputs includes data regarding fuel supply, fuel formulation, and alternative 

vehicle fuels and technology (AVFT). 

2.4.1 Fuel Supply

FuelSupply(countyID, fuelYearID, monthgroupid, fuelformulationid, marketshare, 

marketsharecv)

Fuel supply inputs designate the fuel formulations used by the model for each model year for

each source type.

National default fuel supply inputs were used for all source types except the E10 market share.

By the end of 2011, the E10 market share in Idaho is known to have been virtually 100%, but to 

account for a small number of suppliers who were still selling gasoline with no ethanol in 2011, a

nominal market share of 99% was used for E10 with 1% assigned for ethanol-free gasoline for 

2011.

For 2020, national default fuel supply was used (i.e., 100% E10 market share).
10

2.4.2 Fuel Formulation

FuelFormulation(fuelFormulationID,fuelSubtypeID,RVP,sulfurLevel,ETOHVolume,MTBEVolu

me,ETBEVolume,TAMEVolume,aromaticContent,olefinContent,benzeneContent,e200,e300,BioD

ieselEsterVolume,CetaneIndex,PAHContent,T50,T90)

MOVES national default fuel formulations were judged to be reasonable and alternative local 

data are not readily available. Therefore, national default fuel formulations were used for all 

source types for both 2011 and 2020.

2.4.3 Alternative Vehicle Fuels and Technology

AVFT(sourceTypeID, modelYearID, fuelTypeID, engTechID, fuelEngFraction)

AVFT input files in MOVES allow the user to assign source type activity by model year to 

vehicles with different fuel and/or engine technologies. PVNAA vehicles were modeled using a 

custom AVFT input file derived from VIN-decoded registration data for Bannock County. For 

vehicle types not included in the registration data, AVFT files were developed from local data

available from the telephone and e-mail surveys shown in Table 5. National default AVFT was 

used as a supplement when no local data was available.

In 2020, the same vehicle age distribution was assumed to occur as that found in 2011 so vehicle 

age zero was changed from model year 2011 to model year 2020. To match the shift in the age 

distribution, AVFT for 2020 was similarly shifted.

2.5 Meteorology

ZoneMonthHour(monthID, zoneID, HourID, temperature, relHumidity)

The meteorology inputs include the average hourly temperature and relative humidity data for 

PVNAA. The meteorological observation data for 2011 at the Pocatello Regional Airport

National Weather Service station, KPIH, obtained from MESOWEST (2012) an on-line data 

source described by Horel et. al (2002) were used to generate the meteorology input. For any

time periods in which KPIH data are missing, data sets from nearby ITD stations, ITD25, and 

ITD46 (MESOWEST 2012), were used to gap-fill the original data set.

For the future year 2020 projections, the same meteorology input from 2011 was used.

2.6 Inspection and Maintenance Programs

IMCoverage(polProcessID, stateID, countyID, yearID, sourceTypeID, fuelTypeID, 

IMProgramID, inspectFreq, testStandardsID, begModelYearID, endModelYearID, useIMyn, 

complianceFactor)

There are no inspection and maintenance (I/M) programs in place in PVNAA during 2011, and 

no need for an I/M program is anticipated in the foreseeable future. Thus, no I/M program is

designated in the model for both 2011 and 2020.
11

2.7 On-Road Retrofits

On-roadRetrofits(Pollutant, Process, Fuel, Source, InitialCalendarYear, FinalCalendarYear, 

InitialModelYear, FinalModelYear, Fraction/Year, FractionEffective)

Because adequate local data were not available to prepare local on-road retrofit inputs, the 

PVNAA was modeled without local on-road retrofits.

3 Methodology: Paved Road Dust

Fugitive dust from paved and unpaved roads can be a significant source of PM10 emissions.

Because there are no unpaved roads in PVNAA, unpaved road dust is assumed to be negligible. 

This section will focus on paved road dust.

In general, the factors that affect paved road dust emissions include the weight of the vehicles 

that drive on the roadway surface, vehicle speed, fine particle (silt) loading on the roadway 

surface available for entrainment, and precipitation on the roadway that decreases road dust 

emissions. A new emission factor equation for paved roads was published in January 2011 by 

EPA as the agency’s recommended method in AP-42 Compilation of Air Pollutant Emission 

Factors (EPA 2011b, section 13.2.1). This section of the report discusses data collection and 

calculation using the new AP-42 method.

Paved road dust emissions were computed on a daily basis following the most recent AP-42 

guidance (EPA 2011b) for emission factor calculation. The emissions for each day type

(weekend/weekday), each month and each roadway type are the product of the emission factor 

and the VMT in each day type, each month, and on each roadway type. Therefore, for each day 

type, each month, and each roadway type in PVNAA, VMT, road surface silt loading, average 

weight of the vehicles traveling the road, and the number of hours with at least (0.01 inches) of 

precipitation must be determined. The following sections discuss these inputs in detail. For the 

purposes of paved road dust calculations, winter season is defined as November 1–February 29, 

and the summer or nonwinter season is defined as April 1–October 31. The annual emission 

estimates include all 12 months. Note, road dust categories are computed only for local roads, 

arterials and freeways; however, VMT are available for the HPMS roadway types. Table 7 shows 

the roadway type definitions and the crosswalk relationship between the road dust roadways and 

HPMS roadway types.
12

Table 7. Roadway type definitions in road dust calculation.

Road Type for 

Road Dust

Road Type for Road 

Dust HPMS Road Type ID HPMS Road Type

11 Rural interstate 11 Rural interstate

13 Rural arterial

13 Rural principal 

arterial

15 Rural minor arterial

17 Rural major collector

19 Rural minor collector

21 Rural local 21 Rural local

23 Urban interstate

23 Urban interstate

25 Urban freeway/

expressway

27 Urban arterial

27 Urban principal 

arterial

29 Urban minor arterial

31 Urban collector

33 Urban local 33 Urban local

Note: Highway Performance Monitoring System (HPMS)

3.1 Vehicle Miles Traveled

The VMT was generated using TDM outputs in conjunction with ITD ATR data to produce 

VMT for each day type, each month, and each roadway type. The annual VMT totals used in the 

road dust calculations are the same as those used in the MOVES modeling, summarized in Table 

4, section 2.1.1.

3.2 Road Dust Emission Factor 

Paved road dust emissions were computed on a daily basis using the January 2011 AP-42 

Compilation of Air Pollutant Emission Factors (EPA 2011b, section 13.2.1, Equation 2), as 

shown in Equation 4 below. This new version of EPA’s road dust methodology is now required 

for use in SIP and conformity demonstrations. The form of the emission factor equation

(Equation 4) accounts for the dust suppression effect of precipitation that occurs during each 

averaging period.

 [ ( )

 ( ) ] ( 

 

 )

Equation 4. Paved road dust emission 

factor.

where

Eext = PM10 or PM2.5 emission factor in the same units as k

k = particle size multiplier (1.0 for PM10) (grams/VMT)

sL = road surface silt loading (grams per square meter)

W = average weight of the vehicles traveling the road (tons)
13

P = number of wet days with at least 0.01 inches of precipitation during the averaging period 

(daily)

N = number of days in the averaging period (e.g., 28, 29, 30, or 31 for monthly)

3.2.1 Particle Size Multipliers

The particle size multiplier variable, “k” in Equation 4 is used to define the fraction of total PM10

emissions that will be classified as PM2.5 emissions; however, it does not influence the total PM10

emission quantities. The Treasure Valley Road Dust Study (TVRDS) conducted in 2002

(Etemezian et al. 2002) concluded that 5.7% of the total PM10 emissions were in the PM2.5 size 

category. The TVRDS was conducted in Ada and Canyon counties but since the data were

collected in Idaho, it is assumed to better reflect reality for Idaho-specific soils and urban areas 

than the default value (25%) recommended in the guidance (EPA 2011b) and is therefore applied 

to PVNAA. This is a minor issue for a PM10 motor vehicle budget because the PM2.5 is less 

important than the total PM10 emission rate upon which the budget is based.

3.2.2 Silt Loading

General default silt loadings are available by the average daily traffic (ADT) category in the 

January 2011 emission factor methodology for paved roads (EPA 2011b). The VMT-weighted 

silt loading factors are necessary for each roadway type using Equation 5.

 ∑ 

 

 

 Equation 5. VMT-weighted silt loading.

where

sL = VMT-weighted silt loading factor

i = index from 1 to 4, which represent average daily traffic volume (ADT) categories <500, 

500–5,000, 5,000–10,000, and >10,000, respectively

a = Fraction of VMT on roadway in ADT category “i”

U = Ubiquitous baseline silt loading for the summer season or ubiquitous winter baseline silt 

loading for the winter season, for ADT category “i”

The resulting VMT-weighted silt loadings for both summer and winter season by roadway type 

are shown in Table 8. These silt loadings were used for both 2011 and 2020 road dust 

computations.

It should be noted that silt loadings were measured in the Pocatello and Chubbuck area in 

1996/1997 (Light 1998) and were used in the 2004 SIP and subsequent conformity 

determinations since then. However, significant changes in the antiskid treatment have occurred 

in the PVNAA since 1996 resulting from reduced sand usage and improved road dust sweeping 

capacity. The differences are generally summarized in Table 9, based on information obtained 

from the Pocatello and Chubbuck road departments (Randy Ghezzi pers. comm. 2013 and Bryan 

Hall pers. comm. 2013, respectively). The changes reduced the amount of silt on roadways by 

using brine pretreatment, estimated to reduce the amount of sand consumption by 50% when 

used, by replacing some of the sand with road salt, which does not produce silt, and by doubling 
14

the street sweeping capacity in both cities. Significant changes resulted in the 15 years between 

1996 and 2011 from the SIP-related road sanding agreements and additional ongoing efforts.

DEQ believes the local road silt levels in the PVNAA are lower than they were in 1996/1997 and 

are better represented by the more explicit new EPA method (EPA 2011b), which used

ubiquitous winter silt loadings with initial peak antiskid silt loading contributions following

storms. Thus, DEQ now uses the new EPA method, which scales up to the number of winter 

storms and to the traffic level on each roadway to make the current paved road dust emission 

estimates. 

Table 8. Silt loadings used for paved road emission factor calculation.

Road Type Season Silt Loading Factor

Rural interstate Winter 0.0740

Rural interstate Summer 0.0359

Rural arterial Winter 0.6550

Rural arterial Summer 0.2030

Rural local Winter 2.4

Rural local Summer 0.6

Urban interstate Winter 0.0554

Urban interstate Summer 0.0282

Urban arterial Winter 0.1669

Urban arterial Summer 0.0713

Urban local Winter 2.4

Urban local Summer 0.6

Table 9. Antiskid improvements to lower silt loadings in Pocatello and Chubbuck.

1996 2013

Pocatello (Ghezzi pers.comm. 2013)

Sand:salt ratio 15:1 4:1

Number of street sweepers 2 4

Salt brine pretreatment 0 33,000 gallons

Chubbuck (Hall pers. comm. 2013)

Sand:salt ratio 5:1 3:1

Number of street sweepers 1 2

Salt brine pretreatment 0 30 gallons/lane mile

3.2.3 Average Vehicle Weight by Roadway Type

Average vehicle weight for each roadway type is derived from the vehicle type fraction on each 

roadway type and average vehicle weight by vehicle type. ITD ATR data were used to determine 

the vehicle type fractions traveling on each roadway type. The ATR data identify motorcycles, 

passenger vehicles, and three classes of heavy-duty vehicles by length measurement; however,

the FHWA vehicle classification statistics for Idaho by roadway type (Appendix C) are needed to 

provide greater detail in vehicle classification. The average vehicle weight for each vehicle type 

was obtained from the MOVES default database (EPA 2011a) as shown in Table 10. Source type 

descriptions are provided in Table 3.
15

Table 10. Average vehicle weight by vehicle type.

SourceType 

ID HPMS Vtype ID SourceType Name Source Mass (Metric Tons)

11 10 Motorcycle 0.285

21 20 Passenger car 1.479

31 30 Passenger truck 1.867

32 30 Light commercial truck 2.060

41 40 Intercity bus 19.594

42 40 Transit bus 16.556

43 40 School bus 9.070

51 50 Refuse truck 20.684

52 50 Single unit short-haul truck 7.642

53 50 Single unit long-haul truck 6.250

54 50 Motor home 6.735

61 60 Combination short-haul truck 29.328

62 60 Combination long-haul truck 31.404

Note: Highway Performance Monitoring System (HPMS)

3.2.4 Precipitation Data

The number of days with more than a trace of precipitation (≥0.01 inches) is required in the road 

dust calculation. The precipitation data were gathered from two sources, MESOWEST 

(MESOWEST 2012) described by Horel et al. (2002) and the Western Regional Climate Center 

(WRCC 2012). The detailed process used to derived the precipitation data were documented in 

the 2012 DEQ report, Development of the 2011 Paved Road Dust Inventory for the National 

Emission Inventory (DEQ 2012). Because the majority of the PVNAA resides in Bannock 

County, the data for Bannock County, based primarily on the Pocatello Airport National Weather 

Service station were used to represent the PVNAA. The days per month with more than a trace 

amount of precipitation during 2011 are shown in Table 11. For the future year 2020, the same 

meteorology inputs were used.

Table 11. Number of days with greater than 0.01 inches of precipitation for each month in 2011.

County Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Bannock 8 6 16 18 14 9 3 3 2 8 7 4

4 Results

On-road mobile source and paved road dust emissions estimate results are presented in this 

section.

4.1 On-Road Mobile Source Emission Estimates

On-road mobile source annual emission totals are shown in Table 12. The emission results 

include estimates for nitrogen oxides (NOx), sulfur dioxide (SO2), volatile organic compounds 

(VOC), carbon monoxide (CO), particular matter and ammonia (NH3). The PM10 and PM2.5
16

emission estimates in Table 11 include particulate matter from direct exhaust, brake wear, and 

tire wear and does not include paved road dust. 

Table 12. Annual on-road emissions in PVNAA.

Year

NOx SO2 VOC CO PM10 PM2.5 NH3

(tons per year)

2011 1,323 4.4 876 9,529 64.8 51.4 17.9

2020 651 4.0 495 6,643 41.0 27.6 12.7

Notes: Portneuf Valley Nonattainment Area (PVNAA); nitrogen oxides (NOx); 

sulfur dioxide (SO2); volatile organic compound (VOC); carbon monoxide 

(CO); particulate matter with a diameter less than 10 microns (PM10); 

particulate matter with a diameter less than 2.5 microns (PM2.5); ammonia 

(NH3) 

4.2 Paved Road Dust Emission Estimates

Paved road dust annual emissions for the PVNAA are shown in Table 13.

Table 13. Annual paved road dust emissions in PVNAA.

Year

PM10 PM2.5

(tons per year)

2011 316.9 18.1

2020 337.5 19.2

Notes: particulate matter with a diameter less than 10 

microns (PM10); particulate matter with a diameter less 

than 2.5 microns (PM2.5)

5 Quality Control and Quality Assurance

Quality control was achieved by a quality assurance check of each set of inputs and the final 

result for both on-road MOVES modeling and paved road dust calculation. In general, each input 

was checked for internal consistency, compared with Bannock County, where majority of 

PVNAA resides, and assessed for reasonableness. Input and output data were graphed and 

analyzed to ensure that the expected vehicle population, roadway activity, and seasonal patterns 

were obtained and that differences between PVNAA and Bannock County for 2011 and 2020 on 

inputs and output data sets were understood and justified.
17

References

DEQ (Idaho Department of Environmental Quality). 2004. Portneuf Valley PM10 Nonattainment 

Area State Implementation Plan, Maintenance Plan, and Redesignation Request.

Pocatello, ID: DEQ.

DEQ (Idaho Department of Environmental Quality). 2012. Development of the 2011 Paved Road 

Dust Inventory for the National Emission Inventory. Boise, ID: DEQ.

EPA (United States Environmental Protection Agency). 2011a. MOVES (Motor Vehicle 

Emission Simulator). http://www.epa.gov/otaq/models/moves/index.htm.

EPA (United States Environmental Protection Agency). 2011b. AP-42 Compilation of Air 

Pollutant Emission Factors. Accessed October 2011.

http://www.epa.gov/ttn/chief/ap42/index.html.

EPA (United States Environmental Protection Agency). 2012. Using MOVES to Prepare 

Emission Inventories in State Implementation Plans and Transportation Conformity: 

Technical Guidance for MOVES2010, 2010a and 2010b, Washington, DC: EPA, Office 

of Transportation and Air Quality, Transportation and Regional Programs Division. EPA420-B-12-028.

Etyemezian V., H. Kuhns, J. Gillies, M. Green, J. Chow, S. Kohl, and J. Watson. 2002. The 

Treasure Valley Road Dust Study. Las Vegas, NV: Desert Research Institute. 

Horel, J. et al. 2002. “Mesowest: Cooperative Mesonets in the Western United States.” Bull. 

Amer. Meteor. Soc. 83: 211–225. 

Light, J. 1998. Pocatello Road Dust Study Final Report. Prepared for Bannock Transportation

Planning Organization. Pocatello, ID.

MESOWEST. 2012. MESOWEST Online Meteorology Tool. Data retrieved November 2012.

http://mesowest.utah.edu/.

Parsons (Parsons Brinkerhoff, PB Americas, Inc.). 2012. BTPO Travel Model User’s Guide.

Prepared for Bannock Transportation Planning Organization in Pocatello, ID. Portland, 

OR: Parsons.

WRCC (Western Regional Climate Center). 2012. 2011 Precipitation Data for all Idaho 

Measurement Sites. Reno, NV: WRCC. http://www.wrcc.dri.edu.
18

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19

Appendix A. Crosswalk between BTPO TDM Road Types, 

FHWA Roadway Types, and MOVES Roadway Types

BTPO 

Road Type 

ID

BTPO Road Type Descriptions Area 

Type

FHWA 

Road 

Type 

Code

FHWA Road 

Type 

Description

MOVES 

Road 

Type

MOVES 

Road Type 

Description

Parked vehicles and extended idle are not included in BTPO or FHWA road types 1 Off Network

6

Interstate Rural

01

Rural Principal 

Arterial—

Interstate

2

Rural 

Restricted 

5 Ramp Rural Access

4

Principal arterial Rural 02 Rural Principal 

Arterial—Other

3

Rural 

Unrestricted 

Access

3

Minor arterial Rural 06 Rural Minor 

Arterial

2

Collector Rural 07 Rural Major 

Collector

Rural 08 Rural Minor 

Collector

1 Local Rural

09 Rural Local

0 Centroid connector Rural

6 Interstate Urban

11

Urban Principal 

Arterial—

Interstate

4

Urban 

Restricted 

Access

5 Ramp Urban

Urban 12

Urban Principal 

Arterial—Other 

Freeways or 

Expressways

4

Principal arterial Urban 14 Urban Principal 

Arterial—Other

5

Urban 

Unrestricted 

Access

3

Minor arterial Urban 16 Urban Minor 

Arterial

2 Collector Urban 17 Urban Collector

1 Local Urban

19 Urban Local

0 Centroid connector Urban
20

Appendix B. Crosswalk between ATR Length Bins, FHWA 

Vehicle Classes, and MOVES Source Types 

ATR 

Length 

Bin

ATR Length Bin 

Range

FHWA 

Vehicle 

Class

FHWA Vehicle Class 

Description

MOVES 

Source 

Type ID

MOVES Source Types

1 0–5.9 ft 1 Motorcycles 11 Motorcycle 

2 6–22.9 ft

2 Passenger Cars 21 Passenger Car 

3

Other Two-Axle, FourTire, Single-Unit 

Vehicles

31 Passenger Truck 

32 Light Commercial Truck 

3 23–39.9 ft

4 Buses

41 Intercity Bus 

42 Transit Bus 

43 School Bus 

5

Two-Axle, Six-Tire, 

Single-Unit Trucks

51 Refuse Truck 

52 Single Unit Short-haul Truck 

53 Single Unit Long-haul Truck 

54 Motor Home 

6

Three-Axle, SingleUnit Trucks

51 Refuse Truck 

52 Single Unit Short-haul Truck 

53 Single Unit Long-haul Truck 

54 Motor Home 

7

Four-or-More Axle, 

Single-Unit Trucks

51 Refuse Truck 

52 Single Unit Short-haul Truck 

53 Single Unit Long-haul Truck 

54 Motor Home 

4 40–69.9 ft

8

Four-or-Less Axle, 

Single-Trailer Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 

9

Five-Axle, SingleTrailer Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 

10 Six-or-More Axle, 

Single-Trailer Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 

5 >70 ft

11 Five-or-Less Axle, 

Multi-Trailer Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 

12 Six-Axle, Multi-Trailer 

Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 

13 Seven-or-More Axle, 

Multi-Trailer Trucks

61 Combination Short-haul Truck 

62 Combination Long-haul Truck 
21

Appendix C. ITD Statewide Vehicle Classification Data
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

Appendix B. Procedure for Revising MVEBs for PVNAA to 

Reflect MOVES and Paved Road Dust Model 

Changes
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

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1

Procedure for Revising MVEBs for PVNAA to 

Reflect MOVES and Paved Road Dust Model 

Changes

Introduction

The 2004 State Implementation Plan (SIP) for the Portneuf Valley Nonattainment Area 

(PVNAA) established motor vehicle emission budgets (MVEB) for 2005, 2010, and 2020

(DEQ 2004). The existing MVEBs were developed consistent with the emission inventory 

and attainment demonstration that showed future compliance with the National Ambient Air 

Quality Standards (NAAQS) for particulate matter with a diameter less than 10 microns

(PM10). The existing MVEBs established in the 2003 PVNAA SIP are shown in Table 1.

Table 1. Existing MVEB established in 2004 PVNAA SIP.

Year PM10 (TPY) NOx (TPY) VOC (TPY)

2005 897 1,575 983

2010 1,120 1,085 716

2020 1,364 514 585

Notes: motor vehicle emission budget (MVEB); Portneuf Valley Nonattainment 

Area (PVNAA); State Implementation Plan (SIP); particulate matter with a 

diameter less than 10 microns (PM10); tons per year (TPY); nitrogen oxides 

(NOx); volatile organic compound (VOC)

The existing budgets include on-road mobile emissions computed using MOBILE5, paved 

road dust emissions computed using the 1995 version of the AP-42 paved road dust 

emission factor methodology (EPA 1995), and a small amount of unpaved road dust 

emissions from the few remaining unpaved roads in the area. The United States 

Environmental Protection Agency (EPA) required the use of Motor Vehicle Emission 

Simulator (MOVES) (EPA 2009, 2011a) by March 2013 and a revised AP-42 paved road 

dust methodology (EPA 2011b) by February 2013 for all SIP documents and conformity 

tests. As a result, the Bannock Transportation Planning Organization (BTPO) is required to 

conduct their conformity tests using the new methods. To ensure that a model-only change 

does not cause BTPO to fail the conformity test, the Idaho Department of Environmental 

Quality (DEQ) is revising the existing SIP MVEBs (DEQ 2004) to reflect changes in the 

future year emission estimates that result strictly from the changes caused by the

model/method used. The revised on-road motor vehicle emissions were developed by DEQ 

in 2013 using BTPO’s latest Travel Demand Model (TDM) and planning assumptions for 

2011 and 2020 (DEQ 2013). The purpose of this analysis is to compute revised MVEBs for 

the period from 2010 to 2020, and for 2020 and beyond to replace the 2004 MVEBs shown 

in Table 1 and to demonstrate that the revised MVEBs are equivalent to the existing MVEBs 

in terms of the net PM10 projected to be contributed to the airshed, including PM10 formed 

by the reaction of precursor gases, which produce secondary inorganic aerosol and

contribute to the total PM10 in the airshed. As long as the new MVEBs do not result in 

greater total PM10 contribution to the PVNAA airshed than the existing MVEBs, and the 

growth factors and control strategy assumptions used in the original SIP future year 
2

projections remain valid, such that the overall conclusions of the SIP attainment 

demonstration still hold, the other (nonmobile) categories of the emission inventory and 

demonstration do not need to be revisited (EPA 2012a).

Development of Revised MOVES and Paved Road Dust 

Emission Inventory

The on-road mobile emission inventory for the PVNAA was updated for 2011 and 2020 as 

described by DEQ (2013). Emissions estimates for 2010 were not made, however, because

newer information was available for 2011 as a result of the 2011 National Emission 

Inventory (NEI) project. DEQ used SIP-quality, county-level MOVES inputs (EPA 2012b) 

for the 2011 NEI so that it would be adequate for SIP documentation purposes. Then in 

early 2013, DEQ updated the 2011 NEI inputs to reflect activity data from the PVNAA 

TDM developed by BTPO. As a result, the more recent 2011 emissions will be used to 

replace the existing 2010 MVEBs because 2010 is no longer of interest, and the more recent 

model year is more relevant and timely. Nevertheless, the combined growth rate for the two 

cities in the PVNAA, Chubbuck and Pocatello, from 2010 to 2011 is estimated to be 0.6% 

(US Census 2013) so the 2010 and 2011 estimates are virtually equivalent in time and 

population and may be considered interchangeable. The SIP-level MOVES inputs developed 

for the 2011 NEI include source population data from the Idaho Department of Motor 

Vehicles, traffic temporal information from permanent automatic traffic recorders and bus 

and refuse truck local survey information (DEQ 2013). The MOVES modeling results are 

shown in Table 2 for the milestone years 2011 and 2020. In addition, road dust emissions are 

shown in Table 3 for the same two years, estimated using the 2011 AP-42 paved road dust 

emission factor method (EPA 2011b). The 2011 AP-42 method replaced the 1995 AP-42

paved road dust method in January 2011, and EPA required its use for any work after 

February 2013, so DEQ revised the paved road dust emissions to be consistent with any 

future conformity test that BTPO conducts. The few remaining unpaved roads that were 

modeled in the 2004 emission inventory have been paved since 2004 and no unpaved road 

emissions remain in the PVNAA, so unpaved road emissions are set to zero. MOVES and 

AP-42 paved road dust PM10 emissions are shown in Table 3 along with the total direct PM10

emissions from both sources.

Table 2. On-road mobile source (MOVES) emissions for 2011 and 2020 (DEQ 2013).

Year NOx SO2 VOC CO PM10 PM2.5 NH3

(tons per year)

2011 1,323 4.4 876 9,529 64.8 51.4 17.9

2020 651 4 495 6,643 41 27.6 12.7

Notes: Motor Vehicle Emission Simulator (MOVES); nitrogen oxides (NOx); sulfur dioxide (SO2); volatile organic 

compound (VOC); carbon monoxide (CO); particulate matter with a diameter less than 10 microns (PM10); particulate 

matter with a diameter less than 2.5 microns (PM2.5); ammonia (NH3)
3

Table 3. Paved road dust PM10 emissions, MOVES emissions, and total direct PM10 emissions for 

model years 2011 and 2020 (DEQ 2013).

Year Paved Road 

Dust PM10 (TPY)

MOVES PM10

(TPY)

Total Direct PM10

Emissions

(tons per year) (tons per year) (tons per year)

2011 316.9 64.8 382

2020 337.5 41 378

A direct comparison of the updated MOVES and paved road emissions (DEQ, 2013) with 

the existing MVEB established in the 2004 SIP is shown in Table 4. The 2011 PM10 

emission estimates in Table 4 include the direct PM10 emissions from MOVES (consisting of 

exhaust particulate, brake wear and tire wear) combined with PM10 from revised paved road 

dust computations (DEQ, 2013). Only those pollutants that can significantly contribute 

directly to particulate matter levels in the atmosphere, or indirectly, through photochemical 

reactions are included in the motor vehicle budgets: Direct PM10, nitrogen oxides (NOx) and 

Volatile Organic Carbon compounds (VOCs). The NOx and VOCs form ammonium nitrate 

(NH4NO3) “secondary aerosol” by photochemical reaction in the atmosphere. Ammonia 

(NH3), another precursor to ammonium nitrate is not included in the motor vehicle emission 

budget because vehicles exhaust extremely small amounts, and it is so plentiful in the 

western U.S. atmosphere that it is generally considered always available for reaction and 

relatively invariant in the atmosphere. In addition, sulfur dioxide (SO2) may contribute to 

formation of the secondary aerosol ammonium sulfate (NH4)2SO4), however motor vehicles 

produced very little SO2 in 2004 (<1% of the total sulfur dioxide inventory) so it was not

included in the 2004 MVEBs. Lower fuel sulfur standards have resulted in even less motor 

vehicle SO2 since 2004. Carbon monoxide is a gas and plays no significant role in the 

photochemical production of secondary PM10 so it too is not considered further.

In the Table 4 summary, the second column shows the emission estimates revised in 2013 in 

comparison to the existing MVEB in the third column. The final column shows the 

difference for each pollutant. Both NOx and VOC emissions are higher in the 2011 results 

than the existing MVEBs due to the change in model, while in 2020, only the NOx

emissions are higher; the VOC emissions are slightly lower. In both cases, the total PM10

emissions are well below the existing SIP MVEB levels. This large difference results 

primarily from using the more recent paved road dust estimation method and the newer silt 

loadings recommended by EPA in the new AP-42 method (EPA, 2011), rather than the 1995

AP-42 method and locally measured silt loadings (Light, 1998) based on measurements 

made in 1996/1997. Significant changes in road sanding operations occurred beginning in 

1995 when road sanding agreements with the local city and county road departments 

established a much higher level of road dust controls including salt addition to replace 

portions of the sand, and street sweeping trucks to remove residual road dust after winter 

storms. DEQ believes those changes in road sanding practices from 1996 to 2011 made the 

Pocatello area silt loadings comparable to other cities across the nation, a significant benefit 

of the SIP process. As a result, DEQ believes the recommended nationwide silt loadings in 

the 2011 AP-42 paved road dust methodology are more representative of the PVNAA 

roadways than the 1996/1997 silt loading measured by Light (1998) prior to any significant 

road sanding control measures. These revised silt loadings are more realistic because they 
4

account for the typically higher nationwide road silt associated with normal wintertime road 

sanding conditions but with silt levels that vary with the amount of traffic (e.g., restricted 

access interstates have much less silt and local roads have more).

The 2013 revised emissions show some reductions in direct PM10 emissions and secondary 

aerosol precursors (including VOC in 2020) and some increases in secondary aerosol precursors 

(VOC in 2010 and NOx in 2010 and 2020). As a result, it was not immediately obvious what the 

net effect will be on the final airshed concentrations of PM10. The following section discusses a 

conservative approach for reconciling the new emission estimates with the net effect the 

emissions will have on the airshed, thereby putting the new estimates on a common basis with the 

existing MVEBs from the 2004 SIP.

Table 4. Direct comparison of 2013 on-road emission totals with existing SIP MVEB in tons per 

year (DEQ 2004).

Existing SIP MVEB

2013 Estimates 

Based on BTPOs 

2011 TDM

Difference, Existing SIP 

MVEB—2013 Estimates

Year 2010 2011a2010/2011

NOx 1,085 1,323 -238

VOC 716 876 -160

PM10 1,120 382 738

Total 2,921 2,581 —

Year 2020 2020 2020

NOx 514 651 -137

VOC 585 495 90

PM10 1364 379 986

Total 2,463 1,525 —

a. The 2011 year estimates are more up-to-date and therefore are used to replace 2010.

Notes: State Implementation Plan (SIP); motor vehicle emission budget (MVEB); Bannock Transportation 

Planning Organization (BTPO); Travel Demand Model (TDM); nitrogen oxides (NOx); volatile organic 

compound (VOC); particulate matter with a diameter less than 10 microns (PM10); 

Calculation of Net PM10

To determine the effect of emission reductions on the PM10 concentrations in the PVNAA 

airshed, the method used to demonstrate attainment in the 2004 SIP must be considered. 

CALPUFF dispersion modeling with chemical reaction and Speciated Linear Rollback 

Modeling were used to demonstrate attainment in the 2004 SIP, both based on the 

assumption that any change in emissions for any single species, either a primary or 

secondary pollutant, has a directly linear effect on the concentrations of PM10 in the airshed. 

For direct PM10 emissions, the effect on PM10 concentrations above the regional background 

level is directly proportional to the relative change in emissions. For the NOx emissions, the 

actual effect is uncertain because it depends on the rate of photochemical transformation of 

NOx into NH4NO3, a solid particle less than 10 micrometers in size at wintertime 

temperatures. However, we can say unequivocally that the maximum amount of PM10 that 

can be formed in the atmosphere from each ton of NOx emissions can be determined based 
5

on stoichiometric calculations reflecting the overall transformation process. A simplified 

representation of the photochemical process is shown in Equation 1. In this process, it should 

be noted that (a) only one NH4NO3 molecule can be formed for each NOx molecule, (b) 

ammonia plays a role in forming NH4NO3 but is not considered further since the atmosphere 

is rich in NH3 and thus has little effect on the extent or rate of NH4NO3 formation; and (c)

VOCs participate in the chemistry and are essential in determining the overall rate and 

extent of this transformation; however, carbon does not appear on the right-hand side of the 

reaction as a part of the NH4NO3 particulate formed in the atmosphere, and motor vehicle 

VOCs produce no significant PM10 in the atmosphere on their own accord. 

NOx + VOCs + NH3 + solar UV light  NH4NO3

Equation 1. Ammonium nitrate 

formation.

Since one molecule of NOx (NO or NO2) forms one molecule of NH4NO3, the maximum 

amount of PM10 as NH4NO3 that can be formed from 1 ton of NOx, under any circumstances 

is therefore determined stoichiometrically by Equation 2:

Tons of PM10 as NH4NO3 = tons NOx x (80/31.6)

= tons NOx x 2.53

Equation 2. 100% NOx to PM10 formula.

Where the ratio (80/31.6) reflects the ratio of molecular weights of NH4NO3 (80) and NOx

(31.6), assuming the NOx consists of 90% nitric oxide (NO) and 10% nitrogen dioxide 

(NO2), the composition of NOx emissions in the MOVES model, reflecting tail-pipe 

measurements used by EPA in the formulation of the MOVES model (EPA 2010). Thus, 

although 100% NOx conversion to NH4NO3 does not occur in practice, we can say with 

absolute certainty that it is not possible for greater than 100% conversion and therefore, 

adopting it is a conservative assumption. It should be noted that there is also a night-time 

mechanism for forming nitrate aerosol from NOx emissions; however, the same rule applies: 

one NOx molecule can only produce one NH4NO3 molecule, and the conversion described in 

Equation 2 describes the maximum amount of PM10 formed as NH4NO3 regardless of the 

chemical mechanism involved.

EPA (2008) and others (Boylan and Kim 2012) have estimated the likely atmospheric 

conversion rates of NOx to NH4NO3, since it is of regulatory interest when considering

interpollutant trading in nonattainment areas. EPA’s initial PM2.5 implementation guidance 

early in the program (EPA 2008) suggested that a 100:1 interpollutant trading ratio (IPTR)

(100 tons NOx to 1 ton PM2.5) was appropriate for the western United States; however, EPA 

withdrew their 2008 suggested IPTRs in 2011 and required that IPTRs must be locally 

determined using photochemical models (McCarthy 2011). A recent Federal Register notice 

(FR 41349, July 13, 2011) indicates that EPA proposes to approve a western United States

location-specific NOx to PM2.5 IPTR of 9:1 for the San Joaquin Valley of California. This is 

less than one-third of the PM10 formation rate that corresponds to DEQ’s 100% conversion 

assumption (which is effectively equivalent to a 2.53:1 IPTR, in tons NOx:ton PM2.5, PM10

being equivalent to PM2.5 for the purposes of this discussion.) In view of the more realistic 

conversion rate such as 9:1, DEQ’s 100% conversion bounding assumption is very 

conservative. Should it become necessary, DEQ would pursue development of a local IPTR 

for the PVNAA; however, since MVEB equivalency is confirmed assuming 100% 

conversion, such a significant effort does not currently appear necessary.
6

The quantity of VOC emissions can affect the actual conversion rate of NOx to NH4NO3, as 

discussed above, however, once we assume that 100% of the NOx converts instantaneously 

in the atmosphere to NH4NO3, then no amount of VOC can have any additional effect in 

increasing the conversion rate or extent of conversion of NOx into NH4NO3 or PM10. As a 

result, the quantity of VOC emissions drops out of the computation for determining the net 

PM10 production. Thus the VOC emission budget will be the MOVES VOC estimate for the 

appropriate year with the same safety factors applied to the NOx and PM10 budgets.

Based on the above discussion of net PM10, the Table 4 comparison of the 2013 emission 

estimates with the existing MVEB from the 2004 SIP can be rearranged to show the net 

effects on PM10. The rearranged table reflecting net PM10 emissions due to both direct PM10

emissions and NOx precursor emissions is shown in Table 5. In Table 5, VOC is not shown 

and the NOx emissions have been translated (using Equation 2) into secondary PM10. Now it 

is clear, from the total PM10 values, that for both 2011 and 2020 model years, the 2013 PM10

estimates are lower than the total PM10 associated with the MVEB established by the 2004 

PVNAA SIP. Therefore, the model changes implemented in 2013 resulted in lower net PM10

in the airshed and are thus approvable as a SIP revision without consideration of the overall 

emission inventory and without revisiting the attainment demonstration. 

Table 5. Comparison of 2013 on-road emissions with 2004 MVEBs in terms of net PM10, including 

primary and secondary particulate, assuming 100% NOx conversion.

2013 Estimates 

with 100% NOx

Conversion Rate

Existing SIP 

MVEB with 100% 

NOx Conversion 

Rate

Difference, Existing SIP 

MVEB—2013 Estimates

Year 2011 2010 2010/2011

Secondary PM10 produced 

from NOx and VOC 3,347 2,745 -602

Primary PM10 382 1,120 738

Total PM10 3,729 3,865 136

Year 2020 2020 2020

Secondary PM10 produced 

from NOx and VOC 1,647 1,300 -347

Primary PM10 379 1,364 986

Total PM10 2,026 2,664 639

Notes: motor vehicle emission budget (MVEB); particulate matter with a diameter less than 10 microns (PM10); 

nitrogen oxides (NOx); volatile organic compound (VOC)

Safety Factor

The preceding section demonstrates that the revised MVEBs resulting from EPA-mandated 

changes in the on-road and paved road dust emission models results in lower net PM10 in the 

airshed. However, if the updated emissions estimates were used directly as MVEBs, then

any minor model input differences in future conformity tests could potentially cause the 

Transportation Improvement Program (TIP) emissions estimates to exceed the updated 

budgets without any actual increase in activity or emissions. To avoid this potential 
7

problem, safety factors are typically built into the MVEBs to the extent that can be tolerated

while still demonstrating future year NAAQS compliance in the attainment demonstration, 

or in this case, without exceeding the existing MVEB. Since the existing SIP MVEB is 

consistent with an overall emission inventory and approved attainment demonstration model 

showing future year compliance with the NAAQS (DEQ 2004), the revised model change

MVEBs will remain consistent with the attainment demonstration as long as it does not 

exceed the effective PM10 contributed to the airshed attributed to the existing MVEB. Thus, 

the small differences shown in Table 5 between the Existing SIP MVEB total PM10 and the 

2013 Estimates total PM10 (136 TPY in 2010 and 639 TPY in 2020) represent extra PM10

reductions and, therefore, may be used to provide some minimal safety factor in the new 

MVEBs. The procedure for determining an allowable safety factor that does not cause the 

new MVEB to exceed the existing MVEB in terms of its net contribution to PM10 in the 

airshed is represented in Table 6 through Table 8. Again it is important to note that the extra

reductions converted to safety factor come only from the lower motor vehicle emission 

estimates, not from other emission categories, so a reassessment of the nonmotor vehicle 

emission inventory and the attainment demonstration is not required.

To ensure that the MVEB is protective for any TIP that must be evaluated during the period 

from 2010 to 2019, it is critical to conservatively select the highest component for each 

pollutant that occurs in the period (i.e., from either 2010 or 2020). For VOC and NOx, that 

means that the emissions for 2011 must be used because these two pollutants are highest in 

2011 and lowest in 2020. For PM10, the selection is not as clear because the MOVES PM10

emissions are higher in 2011 (65 TPY) than they are in 2020 (41 TPY), while the road dust 

emissions are higher in 2020 (338 TPY) than they are in 2011 (317 TPY), as shown in Table 

2 and Table 3, respectively. Thus to ensure that the highest projected direct PM10 emissions

are used in the MVEBs to conservatively represent any year in between the two milestone 

years, the 2011 MOVES PM10 (65 TPY) is added to the 2020 paved road dust PM10

(338 TPY) resulting in a hypothetical maximum total direct PM10 emission estimate of 

403 TPY as shown highlighted in Table 6.

To reexamine the net effect on airshed PM10 contributions after identifying the maximum 

emission levels for the period 2011–2020 (shaded grey in Table 6), we must again assume 

that 100% of the NOx may convert to PM10 in the form of NH4NO3 as shown in Table 7. The 

2011 Maximum 2013 Estimates shown in Table 7, representing the total net PM10 emission 

estimates are again lower than the existing MVEBs, now by 115 tpy, or 3.1% in 2011 and

by 639 tpy or 31.5% in 2020. These differences in net PM10 emissions may then be 

translated into “safety factor” additions to the estimated emissions without causing the 2013 

total PM10 estimates to exceed the existing (2004 SIP) MVEB total PM10. Thus, the motor 

vehicle emission projections may be increased by 3.1% in 2011 and 31.5% in 2020. The 

2011 safety factor of 3.1% is not normally adequate, but since the first TIP submittal that 

must demonstrate conformity will be the 2015 TIP, the effective safety factor for that 

modeling year, by interpolation between 3% and 31.5%, would be approximately 13%, a

somewhat more reasonable, yet still narrow margin of safety. Nevertheless, due to other 

conservative features of this analysis, DEQ is confident that these safety factors will be 

adequate.
8

Table 6. Maximum emissions for the 2011–2020 period.

Maximum 2013 

Estimates

Existing SIP 

MVEB Difference

Year 2011 2010 2010/2011

NOx 1,323 1,085 -238

VOC 876 716 -160

PM10 403 1,120 717

Year 2020 2020 2020

NOx 651 514 -137

VOC 495 585 90

PM10 379 1364 986

Table 7. Maximum Net PM10 emissions for the 2011–2020 period assuming 100% NOx conversion.

Maximum 2013

Estimates with 100% 

Conversion Rate

(TPY)

Existing SIP MVEB with 100% 

Conversion Rate (TPY)

Difference

(TPY)

Year 2011 2010 2010

Secondary PM10 produced from 

NOx and VOC

3,347 2,745 -602

Primary PM10 403 1,120 717

Total PM10 3,750 3,865 115

% Available as Safety Factor = 115 TPY/3,750 TPY = 3.1%

Year 2020 2020 2020

Secondary PM10 produced from 

NOx and VOC

1,647 1,300 -347

Primary PM10 379 1,364 986

Total PM10 2,026 2,664 639

% Available as Safety Factor = 639 TPY/2,026 TPY = 31.5%

Notes: particulate matter with a diameter less than 10 microns (PM10); nitrogen oxides (NOx); tons per year (TPY); 

State Implementation Plan (SIP); motor vehicle emission budget (MVEB); volatile organic compound (VOC)

Finally, the explicit safety factors of 3.1% in 2011 and 31.5% in 2020 are applied to the 

2013 emission estimates of Table 6 to provide a New SIP MVEB highlighted in Table 8. In 

this table, the Maximum 2013 Estimates in Table 6 were increased, by 3% for 2011 and by 

31.5% in 2020, then entered in Table 8 as the New SIP MVEB.
9

Table 8. New SIP MVEBs including safety factor compared to existing MVEBs.

Existing SIP 

MVEB New SIP MVEB Difference,

New MVEB—Existing MVEB

Year 2010 2011 2010/2011

NOx 1,085 1,364 279

VOC 716 903 187

PM10 1,120 415 -705

Year 2020 2020 2020

NOx 514 856 342

VOC 585 651 66

PM10 1,364 498 -866

Notes: State Implementation Plan (SIP); motor vehicle emission budget (MVEB); nitrogen 

oxides (NOx); volatile organic compound (VOC); particulate matter with a diameter less than 

10 microns (PM10)

As a final step in the process of setting new MVEBs, the new values are tested to 

demonstrate that the net effect on the PVNAA airshed PM10 levels, after applying the safety 

factors, will be equivalent to the existing MVEB established in the 2004 SIP. The net PM10

is once more computed, assuming 100% conversion of NOx to PM10 as shown in Table 9. 

Table 9 demonstrates that the total PM10 in the New SIP MVEB budget for PVNAA is 

equivalent to the Existing SIP MVEB established in the 2004 SIP, as the difference between 

the two is zero in both 2010/2011 and 2020.

Table 9. New versus existing SIP MVEBs equivalence check in terms of net PM10 contribution to 

PVNAA.

Existing SIP MVEB New SIP MVEB Difference, New MVEB—

Existing MVEB

Year 2010 2011 2010/2011

Secondary PM10 produced 

from NOx

2,745 3,450 705

Primary PM10 1,120 415 -705

Total PM10 3,865 3,865 0

Year 2020 2020 2020

Secondary PM10 produced 

from NOx

1,300 2,167 866

Primary PM10 1,364 498 -866

Total PM10 2,664 2,664 0

Notes: State Implementation Plan (SIP); motor vehicle emission budget (MVEB); particulate matter with a diameter 

less than 10 microns (PM10); Portneuf Valley Nonattainment Area (PVNAA); nitrogen oxides (NOx)
10

New Motor Vehicle Emission Budget for the Period 2011–

2020 and Beyond 2020

The analysis above demonstrates that model changes resulting from the use of the 

MOVES2010b model and the 2011 paved road dust method results in new MVEBs that are 

equivalent to the existing MVEBs in terms of PM10 contributions to the PVNAA airshed. 

The resulting MVEB for this period is shown in Table 10. Conformity tests for any TIPs 

conducted from 2015 through 2019 will be required to meet the budget shown for 2011 

(Recall that the 2011 PM10 includes the maximum [2011] MOVES emissions plus the 

maximum (2020) paved road dust emissions). Any TIP conducted in 2020 and beyond will 

be required to meet the budget shown for 2020. 

Table 10. New motor vehicle emission budgets for the PVNAA.

Year PM10 (TPY) NOx (TPY) VOC (TPY)

2005 N/A N/A N/A

2011 415 1,364 903

2020 498 856 651

Notes: Portneuf Valley Nonattainment Area (PVNAA); particulate matter 

with a diameter less than 10 microns (PM10); tons per year (TPY); 

nitrogen oxides (NOx); volatile organic compound (VOC); not applicable 

(N/A)
11

References

Boylan, J. and B. Kim. 2012. Development of PM2.5 Interpollutant Trading Ratios. Presented at 

2012 EPA Regional/State/Local Modeler’s Workshop. Chicago, IL: Georgia 

Environmental Protection Division, Air Protection Branch.

DEQ (Idaho Department of Environmental Quality). 2004. Portneuf Valley PM10 NonAttainment Area State Implementation Plan, Maintenance Plan and Redesignation 

Request. Pocatello, ID: DEQ.

DEQ (Idaho Department of Environmental Quality). 2013. Development of the Year 2011 and 

Year 2020 Mobile Source Emissions Inventories for the Portneuf Valley Non-Attainment 

Area, Idaho. Boise, ID: DEQ. 

EPA (United States Environmental Protection Agency). 1995. “Paved Road Dust.” Section 

13.2.1. Compilation of Air Pollutant Emission Factors. 5th ed. Washington, DC: Office 

of Air Quality Planning and Standards.

EPA (United States Environmental Protection Agency). 2008. PM2.5 New Source Review 

Implementation Rule. 73 FR 28339.

EPA (United States Environmental Protection Agency). 2009. Motor Vehicle Emission Simulator 

(MOVES) 2010: User Guide. Assessment and Standards Division, Office of 

Transportation and Air Quality. EPA-420-B-09-041. 

EPA (United States Environmental Protection Agency). 2011a. MOVES (Motor Vehicle 

Emission Simulator). http://www.epa.gov/otaq/models/moves/index.htm.

EPA (United States Environmental Protection Agency). 2011b. “Paved Road Dust.” Section 

13.2.1. Compilation of Air Pollutant Emission Factors. Washington, DC: Office of Air 

Quality Planning and Standards.

EPA (United States Environmental Protection Agency). 2011c. Revised Policy to Address 

Reconsideration of Interpollutant Trading Provisions. Memorandum from Gina 

McCarthy. July 21.

EPA (United States Environmental Protection Agency). 2012a. Policy Guidance on the Use of 

MOVES2010 and Subsequent Minor Revisions for State Implementation Plan 

Development, Transportation Conformity, and Other Purposes. Washington, DC: EPA.

EPA-420-B-12-010.

EPA (United States Environmental Protection Agency). 2012b. Using MOVES to Prepare 

Emission Inventories in State Implementation Plans and Transportation Conformity: 

Technical Guidance for MOVES2010, 2010a and 2010b. Washington, DC: EPA. EPA420-B-12-028.

Light, J. 1998. Pocatello Road Dust Study Final Report. Prepared for Bannock Transportation 

Planning Organization. Pocatello, ID.
12

US Census (United States Census Bureau). 2013. Annual Estimates of the Resident Population: 

April 1, 2010 to July 1, 2012. Washington, DC: United States Department of Commerce. 

Accessed December 2013. 

http://factfinder2.census.gov/bkmk/table/1.0/en/PEP/2012/PEPANNRES/0400000US16.1

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Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

Appendix C. 2004 SIP Emission Inventory with Updated

On-road Mobile Emissions

Table 1. SIP 2004 emission Inventory with updated on-road mobile emissions (shaded).

Source Category

Original Emissions (DEQ 2004)a Updated Emissions (DEQ 2013)b

MOBILE5 & 1995 Paved Road Dust MOVES & 2011 Paved Road Dust

2000 EI PM10 VOC NOx PM10 VOC NOx

Point 640.8 230.3 924.9

Not updated

Area 980.3 1,610.1 181.9

Non-road 41.4 255.4 823.0

On-Road Mobile 768.6 1,186.7 1,677.8

Total 2,431.0 3,282.4 3,607.4

2005 EI MOBILE5 & 1995 Paved Road Dust

Point 622.2 106.4 538.3

Not updated

Area 1,006.2 1,683.2 191.8

Non-road 41.1 217.5 680.7

On-Road Mobile 904.4 890.0 1,380.2

Total 2,573.8 2,897.0 2,791.0

2010 EI MOBILE5 & 1995 Paved Road Dust MOVES & 2011 Paved Road Dust

Point 622.3 106.4 538.3 622.3 106.4 538.3

Area 1032.0 1756.3 201.7 1,032.0 1,756.3 201.7

Non-road 40.4 183.0 596.4 40.4 183.0 596.4

On-Road Mobile 1019.0 629.9 964.5 381.7 876.0 1,323.0

Total 2713.7 2675.5 2300.8 2,076.4 2,921.6 2,659.4

2015 EI MOBILE5 & 1995 Paved Road Dust

Point 622.2 106.4 538.3

Not updated

Area 1,057.9 1,829.4 211.6

Non-road 42.2 184.5 578.5

On-Road Mobile 1,138.5 480.8 618.6

Total 2,860.8 2,601.1 1,947.0

2020 EI MOBILE5 & 1995 Paved Road Dust MOVES & 2011 Paved Road Dust

Point 622.2 106.4 538.3 622.2 106.4 538.3

Area 1,089.8 1,902.5 221.5 1,089.8 1,902.5 221.5

Non-road 44.5 195.7 579.4 44.5 195.7 579.4

On-Road Mobile 1,258.8 415.3 452.7 378.5 495.0 651.0

Total 3,015.4 2,619.9 1,792.0 2,135.0 2,699.6 1,990.2

Notes:

State Implementation Plan (SIP); Motor Vehicle Emission Simulator (MOVES); emission inventory (EI); particulate 

matter with a diameter less than 10 microns (PM10); volatile organic compound (VOC); nitrogen oxides (NOx)

a. DEQ (Idaho Department of Environmental Quality). 2004. Portneuf Valley PM10 Nonattainment Area State 

Implementation Plan, Maintenance Plan and Redesignation Request. Pocatello, ID: DEQ.

b. DEQ (Idaho Department of Environmental Quality). 2013. Development of the Year 2011 and Year 2020 Mobile 

Source Emissions Inventories for the Portneuf Valley Non-Attainment Area, Idaho. Boise, ID: DEQ.
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Appendix D. Public Involvement

Public Notice
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

Public Hearing
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES

Public Comment and DEQ Response

DEQ received two comments during the public comment period held from February 14, 2014,

through March 17, 2014. No public comments were submitted during the public hearing that was 

held on March 11, 2014. None of the comments received raised substantive issues requiring 

modification to the proposed SIP.

Comment 1: Mike (submitted via email) I'm not against clean air, Or controling pollution but 

lets not raise taxes or give penalties for family's or individual's that have a older car that may not 

meet the governments standards! A lot of people won't be able to afford more tax or a penaltie. I 

have never figured that equation out, your car pollutes so much so we are going to tax you or fine 

you!! Not sure how that fixes the problem!! It's always the same thing with government and 

enviromental agency's!! A new tax will fix the issue! I guess what I'm trying to say is stay out of 

the publics pocket!! We are all sick of the government taking our money to suppoy there little 

programs!! It was your Idea to add more restriction so figure out a way to do it without raising 

taxes!! Just stay out of my pocket!!!

Response to Comment 1: The amendment as proposed does nothing to raise taxes nor does it

give penalties or require additional restrictions. The purpose of this amendment is to revise the 

Portneuf Valley PM10 Nonattainment Area State Implementation Plan, Maintenance Plan, and 

Redesignation Request (DEQ 2004) motor vehicle emissions budget (MVEB) by incorporating 

emission estimates made with the Motor Vehicle Emission Simulator (MOVES), the latest 

United States Environmental Protection Agency (EPA)-required motor vehicle emissions factor 

model (EPA 2009, 2011a) and with an updated road dust estimation method (EPA 2011b). The 

revisions in this amendment only change emission related to the MVEB and no changes are 

made to the point or area source emissions.

Comment 2: This comment was received from the Bannock Transportation Planning 

Organization. This letter is in support of the proposed revision and requests DEQ to submit to 

EPA as soon as possible.
Portneuf Valley PM10 Maintenance Plan Amendment: MOBILE6 to MOVES