APPENDIX A

EVALUATION OF ON-ROAD MOBILE SOURCE EMISSIONS DEVELOPED WITH 

THE MOVES2010A MODEL REPLACING EMISSIONS DEVELOPED WITH THE 

MOBILE6.2 MODEL FOR THE HGB ATTAINMENT DEMONSTRATION SIP 

REVISION FOR THE 1997 EIGHT-HOUR OZONE STANDARD, 

ADOPTED MARCH 10, 2010

Project Number 2012-002-SIP-NR

Adoption

April 23, 2013
EVALUATION OF ON-ROAD MOBILE SOURCE EMISSIONS 

DEVELOPED WITH THE MOVES2010a MODEL REPLACING 

EMISSIONS DEVELOPED WITH THE MOBILE6.2 MODEL 

FOR THE HGB ATTAINMENT DEMONSTRATION SIP

REVISION FOR THE 1997 EIGHT-HOUR OZONE 

STANDARD, ADOPTED MARCH 10, 2010

TABLE OF CONTENTS

1 Overview ...................................................................................................................................1

2 On-Road Emissions Inventory Development with MOVES2010a.......................................... 2

3 Photochemical Model Input Processing of On-Road Emissions..............................................5

4 Attainment Demonstration Motor Vehicle Emissions Budget...............................................10

5 Non-HGB Area On-Road Mobile Source Emission Inventories ............................................16
A-1

1 OVERVIEW

This appendix supplements Appendix B: Emissions Modeling for the HGB Attainment 

Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard of the 2010 HoustonGalveston-Brazoria (HGB) Attainment Demonstration (AD) State Implementation Plan (SIP) 

Revision for the 1997 Eight-Hour Ozone Standard (2010 HGB AD SIP Revision). Appendix B 

for the 2010 HGB AD SIP Revision contains over 200 pages covering the area, biogenic, onroad, non-road, off-road, and point source emission categories that were modeled for the base, 

baseline, and future cases. This document only addresses the on-road emission source category 

because the only substantive change between the 2010 HGB AD SIP Revision and this one is use 

of the 2010a version of the Motor Vehicle Emission Simulator (MOVES2010a) model instead of 

the older MOBILE6.2 model.

On-road emission models and inventories are typically based on the latest available technical 

information at the time they are developed. The 2010 HGB AD SIP Revision relied on the use of 

the MOBILE6.2 model from the United States (U.S.) Environmental Protection Agency (EPA). 

In March 2010, the EPA officially released the MOVES2010 model for SIP use. The subsequent 

MOVES2010a version was released in September 2010, and it was the latest available model at 

the time that on-road inventory development efforts needed to commence for this SIP revision. 

The most current version of the on-road model is MOVES2010b, but it was not released until 

April 2012, which is well after on-road inventory development efforts began.

Table 1: Comparison of MOBILE6.2 and MOVES2010a HGB On-Road Inventories is a 

comparison of 2006 and 2018 summer weekday emission estimates for the MOBILE6.2-based 

on-road inventories previously developed for HGB and the most current ones that rely on 

MOVES2010a. Estimates are provided for the primary pollutants of nitrogen oxides (NOX), 

volatile organic compounds (VOC), and carbon monoxide (CO).

Table 1: Comparison of MOBILE6.2 and MOVES2010a HGB On-Road Inventories

Calendar Year and

Day Type

Development

Date

EPA On-Road

Model

Vehicle Miles

Traveled

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

2006 Summer Weekday Summer 2007 MOBILE6.2 133,868,661 206.74 90.71 1,115.28

2006 Summer Weekday Summer 2011 MOVES2010a 143,408,584 270.00 104.74 1,024.03

2006 Difference 9,539,923 63.26 14.03 -91.25

2006 Change 7.13% 30.60% 15.47% -8.18%

2018 Summer Weekday Spring 2009 MOBILE6.2 180,993,087 52.55 45.97 733.18

2018 Summer Weekday Winter 2012 MOVES2010a 180,955,402 103.34 50.13 656.24

2018 Difference -37,685 50.79 4.16 -76.94

2018 Change -0.02% 96.65% 9.05% -10.49%

An extensive comparison of the differences between MOBILE6.2 and MOVES2010a is beyond 

the scope of this text. Such information is available for interested parties on the EPA MOBILE6

(http://www.epa.gov/otaq/m6.htm) and the EPA MOVES

(http://www.epa.gov/otaq/models/moves/) Web pages. A more in-depth discussion of the 

MOBILE6.2 on-road inventories previously developed is available on pages 120-141 of Appendix 

B of the 2010 HGB AD SIP Revision

(http://www.tceq.texas.gov/airquality/sip/HGB_eight_hour.html) and on the Texas 

Commission on Environmental Quality (TCEQ) FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/HGB/m62/). The remainder of this appendix

will focus exclusively on the most recent MOVES2010a on-road emission inventories. Unlike the 
A-2

MOBILE6.2 model, MOVES2010a estimates nitrogen oxide (NO) and nitrogen dioxide (NO2) 

emissions separately, with total NOX then being the combination of NO and NO2. Where 

appropriate, NO, NO2, and NOX emission estimates are reported separately.

2 ON-ROAD EMISSIONS INVENTORY DEVELOPMENT WITH MOVES2010a

The purpose of this section is to provide a brief overview of the eight-county (Brazoria, 

Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller Counties) HGB area 

on-road mobile source emissions inventory files that were input into the photochemical model 

for the 2006 base cases, the 2006 baseline, and the 2018 future case. These inventory data sets 

were developed under contract by the Texas Transportation Institute (TTI) based on travel 

demand model (TDM) output from the Houston-Galveston Area Council (H-GAC). For each of 

the eight HGB counties, TTI combined vehicle miles traveled (VMT) estimates from the local 

TDM with emission factors from the MOVES2010a model. The net result is referred to as a linkbased inventory because both hourly VMT and emission factor estimates are developed for each 

roadway segment (or “link”) in the network. For each year, summer and school season on-road 

emission inventories were developed for the four day types of weekday (i.e., Monday through

Thursday average), Friday, Saturday, and Sunday. Since these day types are based on seasonal 

average activity inputs, development of separate baseline ozone season day emissions was not 

needed. For the on-road source category, 2006 base case and baseline emissions are the same.

Table 2: VMT and Emissions Day Type Summary for 2006 HGB On-Road Inventory and Table 

3: VMT and Emissions Day Type Summary for 2018 HGB On-Road Inventory provide

summaries of the total VMT, NO, NO2, NOX, VOC, and CO emissions for the entire eight-county 

HGB area for each day type for the 2006 base case and 2018 future case, respectively. As shown, 

Fridays have the highest total VMT of the week, while Saturdays and Sundays have the lowest 

total daily VMT. While overall VMT increases with future growth, total emissions decrease from 

2006 through 2018 as a result of more stringent emissions standards for newer vehicles 

entering the fleet, combined with the simultaneous attrition of older, higher-emitting vehicles. 

Consistent with current federal and state rules, the on-road inventories from TTI include the 

benefits of:

• reformulated gasoline (RFG) in all eight HGB counties;

• the inspection and maintenance (I/M) vehicle testing program in Brazoria, Fort Bend, 

Galveston, Harris, and Montgomery Counties; and

• Texas low emission diesel (TxLED) fuel for all eight HGB counties.

Table 2: VMT and Emissions Day Type Summary for 2006 HGB On-Road Inventory

Season and

Day Type

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Summer Weekday 143,408,584 248.97 21.02 270.00 104.74 1,024.03

Summer Friday 155,151,259 262.31 22.38 284.69 108.78 1,088.33

Summer Saturday 124,752,878 188.13 16.43 204.56 88.27 856.57

Summer Sunday 104,841,414 155.39 13.54 168.93 81.76 757.25

School Weekday 148,105,334 255.88 21.67 277.55 106.50 1,049.60

School Friday 161,135,764 271.03 23.20 294.24 111.11 1,121.65

School Saturday 127,409,483 191.21 16.74 207.95 89.10 870.39

School Sunday 105,902,763 156.41 13.65 170.06 82.07 762.78
A-3

Table 3: VMT and Emissions Day Type Summary for 2018 HGB On-Road Inventory

Season and

Day Type

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Summer Weekday 180,955,402 87.01 16.33 103.34 50.13 656.24

Summer Friday 195,069,658 91.33 17.20 108.54 51.46 693.97

Summer Saturday 157,008,112 66.37 11.96 78.33 43.11 540.43

Summer Sunday 131,735,508 55.73 9.59 65.33 40.83 480.17

School Weekday 184,578,133 88.34 16.62 104.96 50.51 665.79

School Friday 201,855,603 93.91 17.77 111.67 52.19 712.23

School Saturday 159,778,394 67.19 12.13 79.31 43.33 547.52

School Sunday 132,426,639 55.84 9.62 65.46 40.88 482.02

Even though all of the day type on-road inventory data sets were used for photochemical model 

input, only the summer weekday emissions will be detailed here. For the 2006 base case and 

2018 future case, Table 4: Summary of 2006 HGB Summer Weekday On-Road Inventory by 

County and Table 5: Summary of 2018 HGB Summer Weekday On-Road Inventory by County

present respective summaries of the VMT, NO, NO2, NOX, VOC, and CO emissions for each of 

the eight counties in the HGB area.

Table 4: Summary of 2006 HGB Summer Weekday On-Road Inventory by County

HGB Area

County

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 5,891,489 11.11 0.90 12.01 5.02 46.11

Chambers 2,760,121 10.20 0.79 11.00 1.46 18.82

Fort Bend 8,498,717 15.16 1.27 16.42 6.96 60.91

Galveston 6,023,802 9.90 0.82 10.73 5.05 47.36

Harris 105,560,026 171.13 14.67 185.80 75.22 741.49

Liberty 2,549,213 7.05 0.56 7.61 2.22 22.66

Montgomery 10,218,902 19.69 1.63 21.32 7.42 70.62

Waller 1,906,314 4.74 0.38 5.12 1.40 16.06

Eight-County Total 143,408,584 248.97 21.02 270.00 104.74 1,024.03

Table 5: Summary of 2018 HGB Summer Weekday On-Road Inventory by County

HGB Area

County

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 8,477,177 4.34 0.72 5.07 2.93 34.53

Chambers 3,831,327 3.33 0.71 4.04 0.71 11.94

Fort Bend 13,818,366 6.96 1.34 8.30 4.89 54.26

Galveston 6,898,244 3.16 0.54 3.69 2.24 27.35

Harris 126,846,143 56.93 10.59 67.51 32.89 448.17

Liberty 3,570,614 2.67 0.49 3.16 1.20 14.94

Montgomery 14,873,870 7.76 1.53 9.30 4.56 54.45
A-4

HGB Area

County

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Waller 2,639,660 1.86 0.40 2.26 0.71 10.60

Eight-County Total 180,955,402 87.01 16.33 103.34 50.13 656.24

Table 6: Summary of 2006 HGB Summer Weekday On-Road Inventory by Vehicle Type and 

Table 7: Summary of 2018 HGB Summer Weekday On-Road Inventory by Vehicle Type

present respective summaries for 2006 and 2018 of the VMT, NO, NO2, NOX, VOC, and CO 

emissions for each of the gasoline and diesel fuel source use type combinations from the 

MOVES2010a model.

Table 6: Summary of 2006 HGB Summer Weekday On-Road Inventory by Vehicle 

Type

Fuel and Source Use

Type Combination

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Gasoline - Motorcycle 103,546 0.07 0.00 0.08 1.15 1.88

Gasoline - Passenger Car 103,344,259 76.62 7.90 84.52 57.66 549.62

Gasoline - Passenger Truck 20,872,356 32.58 3.13 35.70 24.68 263.14

Gasoline - Light Commercial Truck 6,607,937 11.31 1.11 12.42 8.47 94.06

Gasoline - School Bus 2,194 0.01 0.00 0.01 0.01 0.10

Gasoline - Refuse Truck 40,086 0.22 0.01 0.24 0.09 2.80

Gasoline - Single Unit Short-Haul Truck 1,532,070 4.67 0.30 4.97 1.75 39.56

Gasoline - Single Unit Long-Haul Truck 177,981 0.52 0.03 0.55 0.20 4.00

Gasoline - Motor Home 86,121 0.36 0.02 0.38 0.16 3.02

Gasoline - Combination Short-Haul Truck 214,057 1.41 0.09 1.51 0.53 19.60

Diesel - Passenger Car 103,546 0.17 0.01 0.18 0.01 0.06

Diesel - Passenger Truck 534,122 2.65 0.18 2.83 0.40 2.49

Diesel - Light Commercial Truck 527,932 2.68 0.19 2.87 0.40 2.47

Diesel - Intercity Bus 188,751 3.41 0.24 3.65 0.16 1.09

Diesel - Transit Bus 62,750 0.88 0.06 0.94 0.06 0.35

Diesel - School Bus 212,478 1.73 0.12 1.85 0.17 0.74

Diesel - Refuse Truck 83,173 1.23 0.09 1.32 0.07 0.41

Diesel - Single Unit Short-Haul Truck 3,152,021 17.99 1.25 19.25 2.35 8.83

Diesel - Single Unit Long-Haul Truck 360,470 1.98 0.14 2.12 0.27 0.97

Diesel - Motor Home 177,350 1.43 0.10 1.53 0.19 0.54

Diesel - Combination Short-Haul Truck 2,515,600 38.15 2.65 40.80 1.94 11.90

Diesel - Combination Long-Haul Truck 2,509,787 48.88 3.40 52.27 4.02 16.37

Total 143,408,584 248.97 21.02 270.00 104.74 1,024.03
A-5

Table 7: Summary of 2018 HGB Summer Weekday On-Road Inventory by Vehicle 

Type

Fuel and Source Use

Type Combination

Vehicle Miles

Traveled

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Gasoline - Motorcycle 129,712 0.08 0.00 0.08 1.64 1.45

Gasoline - Passenger Car 128,968,039 24.46 3.19 27.65 26.88 351.64

Gasoline - Passenger Truck 26,329,962 14.60 1.89 16.49 11.68 159.08

Gasoline - Light Commercial Truck 8,683,276 5.88 0.81 6.70 4.26 64.80

Gasoline - School Bus 1,884 0.00 0.00 0.01 0.00 0.06

Gasoline - Refuse Truck 20,833 0.08 0.01 0.10 0.03 0.72

Gasoline - Single Unit Short-Haul Truck 1,945,147 4.42 0.78 5.20 1.46 39.96

Gasoline - Single Unit Long-Haul Truck 208,684 0.45 0.08 0.53 0.15 3.68

Gasoline - Motor Home 104,969 0.29 0.04 0.33 0.12 2.51

Gasoline - Combination Short-Haul Truck 262,652 1.18 0.18 1.36 0.37 8.71

Diesel - Passenger Car 387,701 0.13 0.02 0.16 0.01 0.77

Diesel - Passenger Truck 1,589,804 2.21 0.63 2.83 0.23 2.79

Diesel - Light Commercial Truck 623,310 1.09 0.25 1.34 0.13 1.27

Diesel - Intercity Bus 236,512 1.35 0.17 1.52 0.08 0.59

Diesel - Transit Bus 68,526 0.28 0.04 0.32 0.03 0.17

Diesel - School Bus 260,108 0.74 0.10 0.84 0.08 0.50

Diesel - Refuse Truck 41,404 0.16 0.03 0.19 0.01 0.08

Diesel - Single Unit Short-Haul Truck 3,954,656 3.08 1.27 4.35 0.37 4.04

Diesel - Single Unit Long-Haul Truck 416,123 0.34 0.13 0.47 0.04 0.39

Diesel - Motor Home 212,803 0.50 0.09 0.58 0.08 0.31

Diesel - Combination Short-Haul Truck 3,240,791 8.93 2.14 11.07 0.53 3.98

Diesel - Combination Long-Haul Truck 3,268,503 16.74 4.49 21.23 1.94 8.76

Total 180,955,402 87.01 16.33 103.34 50.13 656.24

The MOVES2010a run specification and county database files used to develop these inventories, 

along with detailed reports and tab-delimited summary output tables, can be found on the 2006

HGB MOVES FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/HGB/mvs/2006/) and 

the 2018 HGB MOVES FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/HGB/mvs/2018/), respectively.

3 PHOTOCHEMICAL MODEL INPUT PROCESSING OF ON-ROAD EMISSIONS

The on-road emissions inventory data provided by TTI were prepared for input into the 

photochemical model using version 3 of the Emissions Processor System (EPS3). When input 

into EPS3, the inventory data are in a readable text-based format. However, once within EPS3, 

the emissions data are maintained in a binary format. Table 8: EPS3 Modules Used to Process 

Eight-County HGB On-Road Emissions Data summarizes the EPS3 modules that were used to 

process the eight-county HGB on-road emission inventories.
A-6

Table 8: EPS3 Modules Used to Process Eight-County HGB On-Road Emissions 

Data

EPS3 Module Description

LBASE Spatially allocate link-based emissions among grid cells.

PREAM Prepare non-link “roadway type” emissions for further processing.

PREPNT Prepare stationary extended idling emissions for further processing.

CNTLEM Apply controls to model strategies, apply adjustments, etc.

TMPRL Apply temporal profiles to extended idling emissions.

CHMSPL Chemically speciate emissions into olefins, paraffins, etc.

GRDEM Sum emissions by grid cell for photochemical model input.

MRGUAM Merge and adjust multiple gridded files for photochemical model input.

The MOVES2010a model also estimates extended idling emissions but only for the diesel fuel 

combination long-haul truck category. Using a combination of SAS and LINUX code, these 

extended idling emissions were aggregated into an eight-county HGB total and spatially 

assigned to known truck stop locations. The extended idling emissions were then processed 

through EPS3 as if they were stationary low-level point sources. The summer weekday extended 

idling emissions by county are presented below in Table 9: 2006 Diesel Fuel Combination LongHaul Truck Extended Idling Emissions for Eight-County HGB and Table 10: 2018 Diesel Fuel 

Combination Long-Haul Truck Extended Idling Emissions for Eight-County HGB. Greater 

detail on heavy-duty vehicle idling activity specific to Texas metropolitan areas can be found on 

the TCEQ On-Road Air Quality Research and Contract Reports Web page

(http://www.tceq.texas.gov/airquality/airmod/project/pj_report_mob.html).

Table 9: 2006 Diesel Fuel Combination Long-Haul Truck Extended Idling 

Emissions for Eight-County HGB

HGB Area

County

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 0.02 0.002 0.03 0.01 0.01

Chambers 0.31 0.02 0.33 0.12 0.18

Fort Bend 0.49 0.03 0.53 0.20 0.29

Galveston 0.08 0.01 0.09 0.03 0.05

Harris 3.05 0.21 3.26 1.22 1.78

Liberty 0.08 0.01 0.08 0.03 0.05

Montgomery 0.66 0.05 0.70 0.26 0.38

Waller 0.38 0.03 0.41 0.15 0.22

Eight-County Total 5.08 0.35 5.43 2.03 2.96

Table 10: 2018 Diesel Fuel Combination Long-Haul Truck Extended Idling 

Emissions for Eight-County HGB

HGB Area

County

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 0.02 0.01 0.03 0.01 0.02

Chambers 0.29 0.13 0.42 0.08 0.24
A-7

HGB Area

County

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Fort Bend 0.46 0.21 0.66 0.13 0.38

Galveston 0.08 0.04 0.11 0.02 0.07

Harris 2.81 1.28 4.10 0.78 2.37

Liberty 0.07 0.03 0.10 0.02 0.06

Montgomery 0.61 0.28 0.88 0.17 0.51

Waller 0.35 0.16 0.51 0.10 0.30

Eight-County Total 4.68 2.14 6.82 1.30 3.95

Based on an EPA memorandum entitled Texas Low Emission Diesel (TxLED) Fuel Benefits, 

September 27, 2001, a 4.8% NOX TxLED reduction should be claimed for 2002-and-newer 

diesel vehicles and a 6.2% NOX TxLED reduction should be claimed for 2001-and-older diesel 

vehicles. In order to determine the specific TxLED adjustment factors that should apply to each 

of the twelve diesel fuel source use types, MOVES2010a runs were performed to determine NOX

emission factors by model year. By using these data, the 4.8% and 6.2% TxLED reductions were 

weighted according to NOX emission model year contributions for each diesel fuel source use 

type. More detail can be obtained on the TxLED Adjustment Factor Analysis FTP site 

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/Statewide/mvs/txled/). The resulting TxLED 

adjustment factors and benefits for both 2006 and 2018 are summarized in Table 11: Summary 

of 2006 Summer Weekday TxLED Benefits by Vehicle Type and Table 12: Summary of 2018 

Summer Weekday TxLED Benefits by Vehicle Type, respectively. The TxLED adjustment factors 

were incorporated by TTI into the on-road inventories by post-processing the MOVES2010a 

diesel fuel source use type NO, NO2, and NOX emission rates.

Table 11: Summary of 2006 Summer Weekday TxLED Benefits by Vehicle Type

Diesel Fuel

Source Use Type

NOX

Reduction

Adjustment

Factor

NOX Benefit

(tpd)

Passenger Car 5.06% 0.9494 0.01

Passenger Truck 5.68% 0.9432 0.17

Light Commercial Truck 5.56% 0.9444 0.17

Intercity Bus 5.97% 0.9403 0.23

Transit Bus 5.94% 0.9406 0.06

School Bus 5.92% 0.9408 0.12

Refuse Truck 5.85% 0.9415 0.08

Single Unit Short-Haul Truck 5.31% 0.9469 1.08

Single Unit Long-Haul Truck 5.35% 0.9465 0.12

Motor Home 5.77% 0.9423 0.09

Combination Short-Haul Truck 5.82% 0.9418 2.52

Combination Long-Haul Truck 5.83% 0.9417 3.24

Total 7.89
A-8

Table 12: Summary of 2018 Summer Weekday TxLED Benefits by Vehicle Type

Diesel Fuel

Source Use Type

NOX

Reduction

Adjustment

Factor

NOX Benefit

(tpd)

Passenger Car 5.02% 0.9498 0.01

Passenger Truck 5.32% 0.9468 0.15

Light Commercial Truck 5.29% 0.9471 0.07

Intercity Bus 5.80% 0.9420 0.09

Transit Bus 5.77% 0.9423 0.02

School Bus 5.76% 0.9424 0.05

Refuse Truck 5.69% 0.9431 0.01

Single Unit Short-Haul Truck 5.04% 0.9496 0.22

Single Unit Long-Haul Truck 5.08% 0.9492 0.02

Motor Home 5.53% 0.9447 0.03

Combination Short-Haul Truck 5.47% 0.9453 0.60

Combination Long-Haul Truck 5.45% 0.9455 1.15

Total 2.43

The summer weekday on-road emissions by county that were input into the photochemical 

model are summarized below in Table 13: 2006 Summer Weekday On-Road Mobile Source 

Inventory by County and Table 14: 2018 Summer Weekday On-Road Mobile Source Inventory 

by County. These on-road inventory summaries are a combination of running exhaust, start 

exhaust, evaporative, and extended idling emissions. Differences by individual counties between 

these figures and those referenced above in Table 4 and Table 5 are due to the spatial 

reallocation of extended idling emissions presented above in Table 9 and Table 10. However, the 

eight-county total on-road emission estimates do not differ.

Table 13: 2006 Summer Weekday On-Road Mobile Source Inventory by County

HGB Area

County

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 11.11 0.90 12.01 5.02 46.11

Chambers 10.33 0.80 11.13 1.50 18.88

Fort Bend 15.11 1.26 16.37 6.95 60.89

Galveston 9.90 0.82 10.72 5.05 47.36

Harris 171.00 14.66 185.66 75.17 741.41

Liberty 7.04 0.56 7.60 2.22 22.66

Montgomery 19.65 1.62 21.28 7.41 70.61

Waller 4.83 0.39 5.23 1.43 16.12

Eight-County Total 248.97 21.02 270.00 104.74 1,024.03
A-9

Table 14: 2018 Summer Weekday On-Road Mobile Source Inventory by County

HGB Area

County

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Brazoria 4.34 0.72 5.06 2.93 34.52

Chambers 3.34 0.72 4.06 0.71 11.94

Fort Bend 6.81 1.27 8.08 4.85 54.14

Galveston 3.17 0.54 3.71 2.24 27.36

Harris 57.08 10.66 67.74 32.93 448.29

Liberty 2.65 0.49 3.14 1.20 14.93

Montgomery 7.67 1.49 9.16 4.54 54.39

Waller 1.95 0.44 2.39 0.73 10.67

Eight-County Total 87.01 16.33 103.34 50.13 656.24

The total eight-county HGB on-road emissions input to the photochemical model by day type 

are summarized below in Table 15: 2006 On-Road Mobile Source Inventory by Day Type and 

Table 16: 2018 On-Road Mobile Source Inventory by Day Type. Slight differences by day type 

between these figures and those presented above in Table 2 and Table 3 are due to how these 

on-road emission inventories are developed in Central Daylight Time (CDT) but must be 

processed for photochemical model input in Central Standard Time (CST). For example, the 11 

p.m. to 12 a.m. CST emissions on a Friday evening are based on 12 p.m. to 1 a.m. CDT emissions 

from a Saturday.

Table 15: 2006 On-Road Mobile Source Inventory by Day Type

Season and

Day Type

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Summer Weekday 248.97 21.02 270.00 104.74 1,024.03

Summer Friday 263.65 22.51 286.16 109.26 1,096.07

Summer Saturday 188.11 16.44 204.55 88.28 857.40

Summer Sunday 154.03 13.40 167.43 81.24 748.53

School Weekday 255.88 21.67 277.55 106.50 1,049.60

School Friday 272.38 23.33 295.71 111.58 1,129.50

School Saturday 197.00 16.97 213.97 96.45 932.44

School Sunday 155.01 13.51 168.52 81.55 753.79

Table 16: 2018 On-Road Mobile Source Inventory by Day Type

Season and

Day Type

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

Summer Weekday 87.01 16.33 103.34 50.13 656.24

Summer Friday 91.60 17.17 108.77 51.65 698.62

Summer Saturday 66.33 11.93 78.25 43.10 540.96

Summer Sunday 55.48 9.65 65.13 40.63 474.88

School Weekday 88.34 16.62 104.96 50.51 665.79

School Friday 94.15 17.72 111.87 52.38 716.92
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Season and

Day Type

NO

(tpd)

NO2

(tpd)

NOX

(tpd)

VOC

(tpd)

CO

(tpd)

School Saturday 67.15 12.10 79.25 43.33 548.17

School Sunday 55.59 9.68 65.27 40.69 476.57

For the on-road mobile inventory portion of the HGB subdomain, the EPS3 message files along 

with the gridded files input into the photochemical model are available on the 2006 HGB EPS3 

FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/HGB/eps3/2006/) and the 2018 HGB 

EPS3 FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/HGB/eps3/2018/).

Similar on-road mobile EPS3 message and gridded files for the Texas-only portion of the larger 

12 km modeling domain are available on the 2006 Texas EPS3 FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/Statewide/eps3/2006/) and the 2018 Texas 

EPS3 FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/Statewide/eps3/2018/).

Similar on-road mobile EPS3 message and gridded files for the non-Texas portions of the larger

12 km modeling domain are available on the 2006 U.S. EPS3 FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/USA/eps3/2006/) and the 2018 U.S. EPS3 FTP 

site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/USA/eps3/2018/).

4 ATTAINMENT DEMONSTRATION MOTOR VEHICLE EMISSIONS BUDGET

By definition, the future case on-road NOX and VOC emission estimates input into the final 

attainment demonstration photochemical modeling run should establish the motor vehicle 

emissions budget (MVEB). The 2018 summer weekday on-road emissions are the most 

representative day type for this purpose and are presented below in Table 17: 2018 Attainment 

Demonstration MVEB for the Eight-County HGB Area. As shown, these 2018 summer weekday 

figures match those provided by TTI as summarized above in Table 3, Table 5, and Table 7. 

Since they were not needed to demonstrate attainment in the 2018 future year, no emission 

reduction credits were taken for either local transportation control measures (TCMs) or

voluntary mobile source emission reduction program (VMEP) strategies.

Table 17: 2018 Attainment Demonstration MVEB for the Eight-County HGB Area

Eight-County HGB Area

On-Road Emissions

NOX

(tpd)

VOC

(tpd)

2018 Summer Weekday On-Road Inventory From TTI

Includes RFG, I/M, and TxLED Benefits

Excludes Local TCM or VMEP Strategies

103.34 50.13
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The following pages contain graphical plots of the 2006 and 2018 on-road summer weekday 

NOX and VOC emissions for the greater HGB area. These plots are respectively entitled Figure 1: 

2006 HGB Summer Weekday NOX Emissions, Figure 2: 2006 HGB Summer Weekday VOC 

Emissions, Figure 3: 2018 HGB Summer Weekday NOX Emissions, and Figure 4: 2018 HGB 

Summer Weekday VOC Emissions.
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Figure 1: 2006 HGB Summer Weekday NOX Emissions
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Figure 2: 2006 HGB Summer Weekday VOC Emissions
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Figure 3: 2018 HGB Summer Weekday NOX Emissions
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Figure 4: 2018 HGB Summer Weekday VOC Emissions
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5 NON-HGB AREA ON-ROAD MOBILE SOURCE EMISSION INVENTORIES

On-road emission inventories for 2006 and 2018 were also developed for portions of the 

modeling domain outside of the eight-county HGB area. For twelve counties (Collin, Dallas,

Denton, Ellis, Hood, Hunt, Johnson, Kaufman, Parker, Rockwall, Tarrant, and Wise Counties)

in the Dallas-Fort Worth (DFW) metropolitan area, a similar link-based inventory development 

approach was taken by the North Central Texas Council of Governments for 2006 based on the 

MOVES2010a model and local TDM output. More detail on the development of these on-road 

link-based inventories is available on the following 2006 DFW MOVES FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/DFW/mvs/2006/).

For the Texas counties outside of the HGB and DFW areas, on-road emissions were developed 

by TTI using Highway Performance Monitoring System (HPMS) data as the basis for VMT 

estimates. Summer season emission estimates were developed for the four day types of weekday, 

Friday, Saturday, and Sunday. Hourly emission factors from MOVES2010a were coupled with 

county-level VMT estimates by roadway type for 2006 and 2018. More detail on the 

development of these HPMS-based on-road inventories is available on the 2006 Texas MOVES 

FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/Statewide/mvs/2006/) and the 2018 

Texas MOVES FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/Statewide/mvs/2018/).

For the non-Texas U.S. portions of the modeling domain, the TCEQ ran MOVES2010a in default 

mode to generate July weekday mobile source emissions by county for both 2006 and 2018. 

Pollutant-specific ratios by hour were applied to these July weekday figures to yield emission 

estimates for Friday, Saturday, and Sunday day types. These ratios for non-Texas inventories 

were obtained from the 2006 and 2018 Texas on-road emission estimates developed specifically 

for each day type. More detail on the development of these default MOVES2010a on-road 

inventories is available on the 2006 U.S. MOVES FTP site

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/USA/mvs/2006/) and the 2018 U.S. MOVES 

FTP site (ftp://amdaftp.tceq.texas.gov/pub/Mobile_EI/USA/mvs/2018/).

More detail on this approach is documented in a presentation entitled Using the MOVES Model 

in Inventory Mode to Develop Regional On-Road Emission Inputs for Air Quality Modeling 

Applications (http://www.epa.gov/otaq/models/moves/conference2011/inventory-regionalmoves-2011.pdf), which was presented at an EPA workshop in June of 2011. A summary of the 

different on-road emission estimation approaches by geographic area taken for this HGB SIP 

revision is provided in Table 18: On-Road Inventory Development by Area Within the Modeling 

Domain.
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Table 18: On-Road Inventory Development by Area Within the Modeling Domain

On-Road Inventory

Parameter

HGB and

DFW

Non-HGB and

Non-DFW Texas

Non-Texas U.S.

States and Counties

VMT Source and

Resolution

TDM Roadway

Links

HPMS Data Sets

19 Roadway Types

MOVES2010a Database

12 Roadway Types

Season/Month

Modeled School and Summer Summer Only July Only

Day

Types

Weekday, Friday, 

Saturday, and Sunday

Roadway Speed

Distribution

Varies by

Hour and Link

Varies by Hour and

Roadway Type

MOVES2010a

Default

MOVES Source

Use Types All Thirteen

MOVES Fuel

Types Gasoline and Diesel

Extended Idling

Emissions Allocation Truck Stops Interstates and OtherHighway Types