ATTACHMENT F

DEVELOPMENT OF DFW ON-ROAD EMISSION INVENTORIES FOR THE YEARS 

2012, 2014, 2017, 2020, 2023, 2026, AND 2028
DALLAS-FORT WORTH ON-ROAD EMISSION 

INVENTORIES TO SUPPORT THE ONE-HOUR OZONE AND 

1997 EIGHT-HOUR OZONE NATIONAL AMBIENT AIR

QUALITY STANDARD REDESIGNATION SUBSTITUTE

STATE IMPLEMENTATION PLAN

This attachment documents the development of the on-road mobile emissions inventory (EI) for 

the updates to the Dallas-Fort Worth Ozone Nonattainment Area (DFW) Redesignation 

Substitution (RS) State Implementation Plan.

The development of the RFP EIs was done by the North Central Texas Council of Governments 

(NCTCOG) at the request and under the direction of the Texas Commission on Environmental 

Quality (TCEQ). The on-road mobile source EIs and control strategy reduction estimates reflect 

the most recent planning assumptions for the DFW transportation network. Complete 

documentation of the development and resulting EI is provided in the attached 

document, Dallas-Fort Worth On-Road Emission Inventories to Support One-Hour Ozone and 

1997 Eight-Hour Ozone Redesignation Substitute. The final emissions estimates are 

summarized in Chapter 1: Introduction, in Exhibit 1.3: On-road Emissions for the DFW FourCounty Modeling Domain and Exhibit 1.4: On-road Emissions for the DFW Nine-County 

Modeling Domain. The supporting electronic documents for the EI development, including 

MOVES2014 input and output files and the post processing spreadsheets used to summarize the 

inventories are available upon request in electronic format. Please contact the TCEQ, Air Quality 

Division, Area and Mobile Source Inventory and Data Support Team if a copy of the electronic 

information is needed.

The report also documents the development of year-to-year control strategy reduction estimates 

for each of the RS milestone years between 2012 and 2028. Control strategy emission reduction 

estimates include the effects of the Federal Motor Vehicle Control Program, the DFW vehicle 

inspection and maintenance program, federal reformulated gasoline Phase 1 and Phase 2, and 

the Texas Low Emission Diesel Program. The control scenarios are the basis for quantifying the 

year-to-year reductions.
Dallas-Fort Worth 

On-road Emission Inventories 

to Support One-Hour Ozone 

and 1997 Eight-Hour Ozone 

Redesignation Substitute

 

March 2015 

Collin | Dallas | Denton | Ellis | Johnson 

Kaufman | Parker | Rockwall | Tarrant
What is NCTCOG?

The North Central Texas Council of Governments is a voluntary association of cities, counties,

school districts, and special districts which was established in January 1966 to assist local 

governments in planning for common needs, cooperating for mutual benefit, and coordinating

for sound regional development.

It serves a 16-county metropolitan region centered around the two urban centers of Dallas and 

Fort Worth. Currently the Council has 238 members, including 16 counties, 169 cities, 

22 independent school districts, and 31 special districts. The area of the region is approximately

12,800 square miles, which is larger than nine states, and the population of the region is over 

6.5 million, which is larger than 38 states.

NCTCOG's structure is relatively simple; each member government appoints a voting

representative from the governing body. These voting representatives make up the General

Assembly which annually elects a 15-member Executive Board. The Executive Board is 

supported by policy development, technical advisory, and study committees, as well as a 

professional staff of 310.

NCTCOG's offices are located in Arlington in the Centerpoint Two Building at 616 Six Flags Drive

(approximately one-half mile south of the main entrance to Six Flags Over Texas).

North Central Texas Council of Governments

P. O. Box 5888

Arlington, Texas 76005-5888

(817) 640-3300

NCTCOG's Department of Transportation

Since 1974 NCTCOG has served as the Metropolitan Planning Organization (MPO) for

transportation for the Dallas-Fort Worth area. NCTCOG's Department of Transportation is 

responsible for the regional planning process for all modes of transportation. The department 

provides technical support and staff assistance to the Regional Transportation Council and its

technical committees, which compose the MPO policy-making structure. In addition, the 

department provides technical assistance to the local governments of North Central Texas in 

planning, coordinating, and implementing transportation decisions.

Prepared in cooperation with the Texas Department of Transportation and the U. S. Department

of Transportation, Federal Highway Administration, and Federal Transit Administration.

"The contents of this report reflect the views of the authors who are responsible for the opinions, findings,

and conclusions presented herein. The contents do not necessarily reflect the views or policies of the

Federal Highway Administration, the Federal Transit Administration, or the Texas Department of

Transportation."
Dallas-Fort Worth 

On-road Emission Inventories 

to Support One-Hour Ozone 

and 1997 Eight-Hour Ozone 

Redesignation Substitute

 

March 2015 

Collin | Dallas | Denton | Ellis | Johnson 

Kaufman | Parker | Rockwall | Tarrant
NCTCOG Executive Board 2014 - 2015

President

Kathryn Wilemon

Mayor Pro Tem

City of Arlington

Vice-President

John Horn

County Judge

Hunt County

Secretary-Treasurer

Daniel Scarth

Councilmember

City of Fort Worth

Past President 

Stephen Terrell

Mayor

City of Allen

Director

Vonciel Jones Hill

Councilmember

City of Dallas 

Director

Clay Lewis Jenkins

County Judge

Dallas County

Director 

Tom Lombard

Councilmember

City of North Richland Hills

Director

Laura Maczka

Mayor

City of Richardson

Director

Dr. Larry Marshall

Councilmember

City of Benbrook

Director

Keith Self

County Judge

Collin County 

Director

Kevin Strength

Mayor

City of Waxahachie

Director

Laura Wheat

Mayor

Town of Westlake

Director

B. Glen Whitley

County Judge

Tarrant County

Ex Officio, Non-Voting Member

Jeff Leach

Texas House of Representatives

General Counsel 

Jerry Gilmore

Executive Director

R. Michael Eastland

Regional Transportation Council 2014 - 2015

Mike Cantrell, Chair

Commissioner, Dallas County 

Mark Riley, Vice Chair

County Judge, Parker County 

Ron Jensen, Secretary

Mayor, City of Grand Prairie 

Douglas Athas

Mayor, City of Garland

Brian Barth, P.E.

District Engineer 

Texas Department of Transportation, 

Fort Worth District 

Carol Bush

County Judge, Ellis County 

Sheri Capehart

Councilmember, City of Arlington

Rudy Durham

Councilmember, City of Lewisville 

Andy Eads

Commissioner, Denton County

Charles Emery

Board Chair, Denton County 

Transportation Authority 

Mark Enoch

Board Member

Dallas Area Rapid Transit 

Gary Fickes

Commissioner, Tarrant County

Rob Franke, P.E.

Mayor, City of Cedar Hill

Sandy Greyson

Councilmember, City of Dallas

Mojy Haddad

Board Member, North Texas Tollway 

Authority

Roger Harmon

County Judge, Johnson County 

Vonciel Jones Hill

Councilmember, City of Dallas 

Clay Lewis Jenkins

County Judge, Dallas County

Jungus Jordan

Councilmember, City of Fort Worth

Sheffie Kadane

Councilmember, City of Dallas

Lee Kleinman

Councilmember, City of Dallas

Stephen Lindsey

Councilmember, City of Mansfield

Brian Loughmiller

Mayor, City of McKinney

Laura Maczka

Mayor, City of Richardson

David Magness 

Commissioner, Rockwall County

Scott Mahaffey

Board Chair

Fort Worth Transportation Authority

Matthew Marchant

Mayor, City of Carrollton 

Maher Maso

Mayor, City of Frisco 

John Monaco

Mayor, City of Mesquite 

Kevin Roden

Councilmember, City of Denton

Amir Rupani

Citizen Representative, City of Dallas

Daniel Scarth

Councilmember, City of Fort Worth

Kelly Selman, P.E.

District Engineer

Texas Department of Transportation, 

Dallas District

Lissa Smith

Mayor Pro Tem, City of Plano

Mike Taylor

Mayor Pro Tem, City of Colleyville

Stephen Terrell

Mayor, City of Allen

T. Oscar Trevino, Jr., P.E.

Mayor, City of North Richland Hills 

William Velasco, II

Citizen Representative, City of Dallas

Oscar Ward

Councilmember, City of Irving

Bernice J. Washington

Board Member

Dallas/Fort Worth International Airport

Duncan Webb

Commissioner, Collin County 

B. Glen Whitley

County Judge, Tarrant County

Kathryn Wilemon

Mayor Pro Tem, City of Arlington 

Zim Zimmerman

Councilmember, City of Fort Worth

Michael Morris, P.E.

Director of Transportation, NCTCOG

Surface Transportation Technical Committee

Gregory Van Nieuwenhuize, Chair

Haltom City
ABSTRACT

TITLE: Dallas-Fort Worth On-road Emission Inventories to 

Support One-Hour Ozone and 1997 Eight-Hour

Ozone Redesignation Substitute

DATE: March 2015

AUTHORS: Jenny Narvaez

Principal Air Quality Planner

Jody Loza

Air Quality Planner

SUBJECT: Redesignation for the One-Hour Ozone and 1997 

Eight-Hour Ozone Standards

 SOURCES OF COPIES: Transportation Department

North Central Texas Council of Governments

PO Box 5888

Arlington, Texas 76005-5888

(817) 695-9240

NUMBER OF PAGES: 40

 ABSTRACT: The North Central Texas Council of Governments 

conducted on-road emission inventories to assist

the Texas Commission on Environmental Quality to 

develop the one-hour ozone and 1997-eight-hour 

ozone redesignation substitute State 

Implementation Plan for the Dallas-Fort Worth 

region. Four counties were previously designated 

as nonattainment for the one-hour ozone standard: 

Collin, Dallas, Denton and Tarrant Counties; and 

nine counties previously designated as 

nonattainment for the 1997 eight-hour ozone 

standard: Collin, Dallas, Denton, Ellis, Johnson, 

Kaufman, Parker Rockwall, and Tarrant. This report 

documents the on-road mobile methodologies 

applied and estimated emission results for analysis 

years 2012, 2014, 2017, 2020, 2023, 2026, and 

2028. The estimated emissions are reported for 

oxides of nitrogen, volatile organic compounds, 
carbon monoxide, carbon dioxide, particulate 

matter with aerodynamic diameters equal to or 

less than 2.5 microns, and particulate matter with 

aerodynamic diameters equal to or less than 10 

microns.
ACKNOWLEDGEMENTS

The North Central Texas Council of Governments would like to thank the following individuals for 

their invaluable assistance in preparing this report.

Michael Morris, P.E. Director of Transportation

Dan Kessler Assistant Director of Transportation

Vickie Alexander Administrative Program Supervisor

Berrien Barks Senior Transportation Planner

Emily Beckham Grants and Contract Supervisor

Michael Burbank Program Manager

Cecilia Howard Senior Administrative Assistant

Chris Klaus Senior Program Manager

Dan Lamers, P.E. Senior Program Manager

Chad McKeown Program Manager

Arash Mirzaei, P.E. Senior Program Manager

Behruz Paschai, Ph.D., P.E. Transportation System Modeling Manager

Ashley Releford Grants and Contracts Coordinator

Samuel Simmons Transportation Planner III

Francisco Torres Principal Transportation Planner

Mitzi Ward Principal Transportation Planner

Kathleen Yu Senior Transportation System Modeler

Madhusudhan Venugopal, P.E. Providence Engineering and Environmental Group, LLC.

Chris Kite Texas Commission on Environmental Quality

Naomi Craib Texas Commission on Environmental Quality

Mary McGarry-Barber Texas Commission on Environmental Quality

Chris Owen Texas Commission on Environmental Quality

Zarena Post Texas Commission on Environmental Quality

Leslie Schmidt Texas Commission on Environmental Quality

Matthew Southard Texas Commission on Environmental Quality
GLOSSARY OF ABBREVIATIONS

ASWT - Average School Season

 Weekday

ATR - Automatic Traffic Recorder

CAAA - Clean Air Act Amendments

CO - Carbon Monoxide

CO2 - Carbon Dioxide

DFW - Dallas-Fort Worth

DFX - Dallas-Fort Worth Travel 

Model for the Expanded 

Area

DV - Design Value

EPA - Environmental Protection

Agency

GISDK - Geographic Information 

 System Developer Kit

HBW - Home-Based Work

HNW - Home-Based Non-Work

HOV - High Occupancy Vehicle

HPMS - Highway Performance

Monitoring System

I/M - Inspection & Maintenance

Program

MPA - Metropolitan Planning Area

MPO - Metropolitan Planning

Organization

MOVES2014 - Motor Vehicle Emissions

Simulator

NAAQS - National Ambient Air Quality

Standards

NCT - North Central Texas

NCTCOG - North Central Texas Council

of Governments

NHB - Non-Home Based

NO - Nitrogen Oxide

NO2 - Nitrogen Dioxide

NOX - Oxides of Nitrogen

Pb - Lead

PM - Particulate Matter

PM2.5 - Particulate Matter 2.5 

Microns

PM10 - Particulate Matter 10 

Microns

ppb - parts per billion

SIP - State Implementation Plan

SO2 - Sulfur Dioxide

SUT - Source Use Types

TCEQ - Texas Commission on

 Environmental Quality

TOD - Time-of-Day

TSZ - Traffic Survey Zone

TTI - Texas Transportation 

 Institute

TxDMV - Texas Department of Motor 

Vehicles

TxDOT - Texas Department of

 Transportation

TxLED - Texas Low Emissions Diesel

VHT - Vehicle Hours of Travel

VMT - Vehicle Miles of Travel

VDF - Volume Delay Function

VOC - Volatile Organic Compounds 
TABLE OF CONTENTS

Chapter 1: Introduction ................................................................................................................. 1

Background ......................................................................................................................... 2

Purpose and Scope of Study ............................................................................................... 4

Modeling Approach ............................................................................................................ 4

Chapter 2: Vehicle Activity Estimation Procedures....................................................................... 7

Dallas-Fort Worth Expanded Travel Model ........................................................................ 7

Multimodal Transportation Analysis Process......................................................... 7

Trip Generation Model ............................................................................. 10

Trip Distribution Model............................................................................. 11

Mode Choice Model.................................................................................. 11

Roadway Assignment................................................................................ 11

Speed Estimation Procedure ................................................................................ 12

Local Street VMT................................................................................................... 13

Adjustments...................................................................................................................... 13

Seasonal, Daily, and Hourly Adjustments............................................................. 13

Seasonal and Daily Adjustments........................................................................... 15

Hourly Adjustments.............................................................................................. 16

Model VMT Adjustments (HPMS vs. DFX) ............................................................ 17

Nonrecurring Congestion...................................................................................... 18

VMT Estimates.................................................................................................................. 18

Chapter 3: Emission Factor Estimation Procedure ...................................................................... 20

Mobile Model and Input Parameters ............................................................................... 20

Area Specific Calculations and Procedures....................................................................... 25

SourceUse Type Distribution ................................................................................ 25

Fuel Engine Fractions............................................................................................ 27

MOVES2014 Emission Factors .............................................................................. 27

Adjustments.......................................................................................................... 27

TxLED NOx Adjustment......................................................................................... 27

Sourceusetype Population.................................................................................... 28

Vehicle Miles of Travel Mix (or Fractions) (VMT Mix) .......................................... 29

Chapter 4: Emission Calculation Procedure................................................................................. 32

Emission Estimation.......................................................................................................... 33

Rate Per Distance.................................................................................................. 33

Rate Per Vehicle.................................................................................................... 33

Rate Per Profile ..................................................................................................... 33

Chapter 5: Summary of Vehicle Miles of Travel, Speed, and Emissions...................................... 34

Vehicle Miles of Travel Estimates..................................................................................... 34

Speed Estimates................................................................................................................ 34

Emission Estimates............................................................................................................ 34

Chapter 6: List of Appendices....................................................................................................... 40
TABLE OF EXHIBITS

Exhibit 1.1: DFW Nonattainment Area Map.................................................................................. 1

Exhibit 1.2: DFW Travel Demand Modeling Domain Map............................................................. 4

Exhibit 1.3: On-road Emissions for the DFW Four-County Modeling Domain .............................. 5

Exhibit 1.4: On-road Emissions for the DFW Nine-County Modeling Domain .............................. 6

Exhibit 2.1: DFW Expanded Travel Model Process Forecast Flowchart ........................................ 9

Exhibit 2.2: Socio-economic Demographic Summary.................................................................. 10

Exhibit 2.3: Average Congested Speeds....................................................................................... 13

Exhibit 2.4: ATR Stations.............................................................................................................. 14

Exhibit 2.5: ATR Station Map ....................................................................................................... 15

Exhibit 2.6: Seasonal/Daily Adjustment Factors.......................................................................... 16

Exhibit 2.7: Hourly Adjustment Factors for the DFW Four-County and Nine-County

 Modeling Domains................................................................................................. 17

Exhibit 2.8: 2010 DFW and HPMS VMT Analysis ......................................................................... 18

Exhibit 2.9: Vehicle Miles of Travel (Miles/Day).......................................................................... 19

Exhibit 3.1: MOVES2014 Modeled Pollutants.............................................................................. 20

Exhibit 3.2: MOVES2014 External Conditions.............................................................................. 20

Exhibit 3.3: MOVES2014 Input Parameters................................................................................. 21

Exhibit 3.4: MOVES2014 I/M Descriptive Inputs for Subject Counties........................................ 23

Exhibit 3.5: MOVES2014 Fuel Properties..................................................................................... 24

Exhibit 3.6: County-to-County Worker Flow................................................................................ 26

Exhibit 3.7: TxLED NOx Adjustments............................................................................................ 28

Exhibit 3.8: Population for the DFW Four-County and Nine-County Modeling Domains........... 29

Exhibit 3.9: Vehicle Classification Process ................................................................................... 30

Exhibit 4.1: MOVES2014 Emission Calculation Modeling Process................................................ 32

Exhibit 4.2: DFX Area Type........................................................................................................... 33

Exhibit 5.1: VMT by County ......................................................................................................... 35

Exhibit 5.2: Final Emission Estimates by County........................................................................... 35
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 1

CHAPTER 1: INTRODUCTION

The North Central Texas Council of 

Governments (NCTCOG) conducted an onroad emissions inventory to support the 

Texas Commission on Environmental 

Quality’s (TCEQ) efforts to develop modeling

work for the One-hour Ozone and 1997 

Eight-hour Ozone Redesignation State 

Implementation Plan (SIP). This emission 

inventory covers the Dallas-Fort

Worth (DFW) four-county nonattainment 

area for the one-hour standard: Collin, 

Dallas, Denton, and Tarrant counties as well 

as the nine-county nonattainment area for 

the 1997 eight-hour ozone standard: Collin, 

Dallas, Denton, Ellis, Johnson, Kaufman, 

Parker, Rockwall, and Tarrant counties as 

shown in Exhibit 1.1.

Exhibit 1.1: DFW Nonattainment Area Map
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 2

This report documents the methodology and 

results of the Redesignation Substitute

emission inventory. The Redesignation

Substitute emission inventory analysis years

include: 2012, 2014, 2017, 2020, 2023, 

2026, and 2028. Chapter 1 outlines the 

background for the Redesignation Substitute

emission inventory, the purpose and scope 

of the study, the modeling approach, and 

provides a summary of the four-county and

nine-county estimated emission totals and

activity summaries.

Chapter 2 documents the procedures used 

to develop regional vehicle activity estimates 

in terms of vehicle miles of travel (VMT) and 

average vehicle speed. These procedures 

include development of adjustment factors 

to more accurately reflect regional 

conditions. Seasonal and hourly adjustment 

factors were applied to produce 2012, 2014, 

2017, 2020, 2023, 2026, and 2028 analysis 

year vehicle activity and report vehicle 

activity in hourly periods. Consistent with 

previous emission inventory practices, a 

comparison was made between the DallasFort worth Expanded Travel Demand Mode

(DFX) VMT estimates and appropriate 

Highway Performance Monitoring System 

(HPMS) VMT to develop HPMS adjustment 

factors. Also, a nonrecurring congestion 

adjustment was applied to account for 

vehicle emissions due to traffic accidents not 

captured in the standard four-step travel 

modeling process.

Chapter 3 documents the parameters and 

inputs used to develop on-road mobile 

source emission factors by utilizing the 

United States Environmental Protection 

Agency’s (EPA) mobile source model, Motor 

Vehicle Emission Simulator version 2014

(MOVES2014). This chapter documents 

regionally specific calculations, procedures, 

MOVES2014 emission factors, and 

adjustments to more accurately reflect 

regional vehicle emissions emitted. The 

calculations and procedures include vehicle 

registration, diesel fractions, hourly VMT, 

and trip length distribution. Also accounted 

for are low emission diesel oxides of 

nitrogen (NOX) adjustments and VMT mix.

Chapter 4 documents the four-county and 

nine-county nonattainment area vehicle 

emission calculation procedure.

Chapter 5 summarizes emissions of all 

pollutants by county and analysis year.

The Appendices contains supplemental 

information, including a table containing all 

pollutants calculated, and electronic data 

supporting the DFW Redesignation

Substitute Emissions Inventory. 

Background

The Clean Air Act Amendments (CAAA) of

1990 requires the EPA to set National 

Ambient Air Quality Standards (NAAQS) for 

widespread pollutants considered harmful to 

public health and the environment. The EPA 

set NAAQS for six of the principal pollutants:

ozone, particulate matter (PM), carbon 

monoxide (CO), sulfur dioxide, NOX, and 

lead.

With the signing of the CAAA into law, the 

four counties of Collin, Dallas, Denton, and 

Tarrant County in the DFW region were 

designated as nonattainment under the 

one-hour NAAQS for the pollutant ozone. 

The law also requires the EPA to periodically 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 3

review the NAAQS to ensure they provide 

adequate health and environmental 

protection and to update these standards as 

necessary. Upon completion of a scientific 

review of the one-hour NAAQS, EPA 

determined the one-hour NAAQS was 

insufficient to protect human health. As a 

result, the EPA developed the 1997 eighthour NAAQS, <85 parts per billions (ppb), to 

place greater emphasis on prolonged 

exposure to pollutants.

In April 2004, EPA announced Collin, Dallas, 

Denton, Ellis, Johnson, Kaufman, Parker, 

Rockwall, and Tarrant Counties comprise 

the new DFW nine-county nonattainment 

area for the pollutant ozone under the 1997 

8-hour NAAQS, with an effective 

designation date of June 15, 2004. The 

nine-county nonattainment region received 

a “Moderate” ozone classification with an 

attainment date of June 15, 2010. As a 

result of not reaching attainment by June 

2010, the DFW region was classified as 

“Serious” with the new attainment date of 

June 2013.

On February 10, 2015, the EPA proposed to 

reclassify the DFW area as “Severe” 

nonattainment for the 1997 eight-hour 

ozone standard, since DFW failed to meet 

the June 15, 2013, deadline to reach 

attainment; however, the EPA subsequently 

published a final rule revoking the 1997 

eight-hour ozone standard with an effective 

date of April 6, 2015. Since EPA cannot 

reclassify or redesignate areas based on a 

revoked standard, the DFW region is no 

longer subject to being reclassified as 

“Severe”. The DFW area’s 2014 design value

(DV), the three-year average of the annual 

fourth highest daily maximum eight-hour 

 

1 http://www.tceq.state.tx.us/cgi-bin/compliance/monops/8hr_attainment.pl

ozone concentration measured at each 

monitoring site, is 81 ppb1, bringing the 

region’s DV below the 1997 eight-hour 

ozone standard. Although the DFW region 

can no longer redesignated to attainment

under the revoked standard, the DFW 

region is eligible to submit a redesignation 

substitute to remove the “Serious” antibacksliding requirements for the one-hour 

and 1997 eight-hour standard.

The TCEQ, state’s environmental agency, is 

required under the CAAA to submit a SIP 

revisions requesting designation to 

attainment. A maintenance plan must also 

be submitted with the redesignation, 

including a selection of regulations and 

measures to reduce emissions from 

stationary, area, mobile (on-road and nonroad) sources, which demonstrates how the 

region will stay in attainment.

On-road mobile is a key component of the 

SIP, as a SIP places emission limits on onroad mobile sources. These on-road mobile 

emission limits are termed motor vehicle 

emission budgets and have a direct impact 

on transportation planning. NCTCOG serves 

as the Metropolitan Planning Organization

(MPO) for transportation in the DFW area 

and is responsible for developing and 

maintaining on-road mobile source 

emission inventories for the region. 

NCTCOG applies a four-step travel demand 

model process using TransCAD software to 

forecast regional vehicle activity and utilizes 

EPA’s MOVES2014 with a post-processing 

application to estimate regional mobile 

source emissions.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 4

Purpose and Scope of Study

NCTCOG conducted 2012, 2014, 2017, 2020, 

2023, 2026, and 2028 analysis year on-road 

emission inventories to support TCEQ’s 

efforts to develop a Redesignation Substitute

SIP for the DFW four-county and nine-county 

nonattainment areas. The pollutants to be 

included are: NOX, volatile organic 

compounds (VOC), CO, carbon dioxide 

(CO2), PM2.5, and PM10.

Modeling Approach

The DFX is employed to estimate VMT and 

emissions for the 2012, 2014, 2017, 2020, 

2023, 2026, and 2028 analysis years. DFX’s 

modeling domain includes Collin, Dallas, 

Denton, Ellis, Hill, Hood, Hunt, Johnson, 

Kaufman, Parker, Rockwall, Tarrant, and 

Wise Counties. Hill County is not part of the 

North Central Texas (NCT) Metropolitan 

Planning Area (MPA) boundary; however, to 

capture travel from outside areas, Hill 

County is included in the modeling domain.

The 12-county MPA and the 13-county DFX

modeling domain is shown in Exhibit 1.2.

Exhibit 1.2: DFW Travel Demand Modeling Domain Map
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 5

Several components of the model were 

updated as part of this model expansion. 

These include improvements to the modechoice model; vehicle ownership model; 

external stations; volume-delay-function; 

transit assignment; and traffic assignment 

convergence criteria, which are discussed in 

Chapter 2.The final 2012, 2014, 2017, 2020, 

2023, 2026, and 2028 on-road emissions by 

pollutant and VMT for average summer 

weekday types are shown in Exhibit 1.3 and 

1.4. Appendix G contains the detailed 

emissions by county by pollutant and timeof-day for all NCT counties modeled. 

Exhibit 1.3: On-road Emissions for the DFW Four-County Modeling Domain

Four-county Total Emissions (tons per day)

2012 2014 2017 2020 2023 2026 2028

VMT 158,968,136 166,904,345 182,658,562 193,804,121 203,852,679 214,346,979 225,718,496

NOX 171.20 147.42 96.74 69.67 54.44 43.33 38.83

VOC 78.56 71.20 55.59 46.81 41.53 35.85 32.94

CO 1,012.11 970.62 877.61 813.08 744.34 645.90 597.70

CO2 86,955.07 89,632.14 93,630.82 93,609.47 91,308.15 88,741.64 88,658.97 

HONO 1.37 1.18 0.77 0.56 0.44 0.35 0.31 

NO 152.85 130.42 83.88 58.98 44.66 33.91 29.96 

NO2 16.98 15.82 12.09 10.13 9.34 9.07 8.56 

PM2.5 5.10 4.29 3.00 2.30 1.75 1.47 1.34 

PM10 5.60 4.71 3.30 2.55 1.95 1.64 1.49 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 6

Exhibit 1.4: On-road Emissions for the DFW Nine-County Modeling Domain

Nine-county Total Emissions (tons per day)

2012 2014 2017 2020 2023 2026 2028

VMT 183,855,804 193,671,709 212,516,292 226,113,715 238,584,779 251,758,922 265,309,733

NOX 216.74 188.65 129.19 95.95 77.87 64.62 59.75

VOC 92.17 83.75 65.62 55.36 49.21 42.70 39.49

CO 1,161.55 1,117.46 1,010.18 936.65 859.88 748.53 694.05

CO2 102,142 105,707 111,055 111,582 109,491 107,128 107,375

HONO 1.73 1.51 1.03 0.77 0.62 0.52 0.48

NO 193.33 166.38 110.85 79.73 62.07 48.75 44.16

NO2 21.68 20.76 17.30 15.46 15.17 15.35 15.11

PM2.5 6.48 5.48 3.83 2.94 2.22 1.85 1.68

PM10 7.10 6.01 4.21 3.24 2.46 2.06 1.87
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 7

CHAPTER 2: VEHICLE ACTIVITY ESTIMATION PROCEDURES

This chapter discusses the methodology 

used in estimating the vehicle activity 

measures influencing air quality in the 

North Central Texas area. These measures 

include: vehicle miles of travel (VMT) and 

average speed. The current Dallas-Fort 

Worth (DFW) Expanded Travel Demand 

model (DFX) covers the 12-county 

Metropolitan Planning Area (MPA) of Collin, 

Dallas, Denton, Ellis, Hood, Hunt, Johnson, 

Kaufman, Parker, Rockwall, Tarrant, and 

Wise counties, plus Hill County. The VMT 

and speeds were estimated with the DFX 

using a link-based methodology for each 

time period.

Dallas-Fort Worth Expanded Travel Model

The source of VMT estimates for the 

Redesignation Substitute Emission 

Inventories for the four and nine

nonattainment counties is the networkbased DFX executed by the North Central 

Texas Council of Governments (NCTCOG)

Transportation Department in the TransCAD 

environment. TransCAD is a Geographic 

Information System (GIS)-based commercial 

travel demand software package for 

transportation planning. The DFX supports 

federally required regional transportation 

planning efforts for the DFW region. Since 

1974, NCTCOG has served as the

Metropolitan Planning Organization (MPO)

for the DFW area. The Transportation 

Department provides technical support and 

staff assistance to the Regional 

Transportation Council and its technical 

committees that comprise the MPO policymaking structure.

Multimodal Transportation Analysis Process

The forecasting technique of the DFX is based 

on a four-step sequential process designed to 

model travel behavior and predict travel 

demand at regional, sub-area, or corridor 

levels. These four steps are: Trip Generation, 

Trip Distribution, Mode Choice, and Roadway 

Assignment. 

The roadway network developed for the 

Redesignation Substitute Emissions 

Inventories contains over 30,000 unique 

segments constructed to replicate the

transportation system of the coverage area. 

For these inventories, the transportation 

network was developed for the years 2012, 

2014, 2017, 2020, 2023, 2026, and 2028. 

Each facility link in the network has the 

following attributes:

 Network Node Numbers (defining the 

beginning and end of each link)

 Number of Operational Lanes in the 

AM PM Peak and Off-Peak Periods

 Functional Classification

 Divided/Undivided Roadway Code

 Type of Traffic Control At Link End

 Traffic Direction (One- or Two-Way)

 Length of Link

 Estimated Loaded Speeds In Each 

Period

 Speed Limit

 Traffic Survey Zone

 Tolls

 Area Type

 Free-Flow Speeds

 Hourly Capacities

 Truck Exclusion Code
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 8

Every roadway segment in the network falls in 

one of the functional classes of centroid 

connectors, freeways, principal arterials, minor 

arterials, collectors, ramps, frontage roads, 

and high occupancy vehicle (HOV) lanes.

Trip purposes in the DFX are defined in one of 

four ways: home-based work (HBW), which

includes trips from home to work or work to 

home; home-based non-work (HNW), which

includes non-work trips beginning or ending at 

home; non-home based (NHB), which includes

trips where home is neither the origin nor the 

destination; and other trips that include all 

truck trips as well as all external-internal, 

internal-external, and external-external vehicle 

trips.

The model process begins with an estimate of 

the socioeconomic variables for each zone. 

The data is organized by traffic survey zone 

(TSZ), the smallest zone size available in the 

DFX. The data for each TSZ includes zone 

centroid; median household income; number 

of households; population; basic, retail, and 

service employment; and land area. There are

5,386 TSZs in the model (5,303 internal zones 

plus 83 externals), which is the level of detail 

retained in all four modeling steps. The Trip 

Generation Model generates the number of 

weekday person trips sent to and received 

from each zone. The Trip Distribution Model 

determines the trip interaction between each 

zone and the rest of the zones in the MPA. 

The Mode Choice Model divides the person 

trips into two categories of transit and 

automobile trips. The Assignment Model 

loads the auto demand onto the roadway 

network, and the transit passenger trips onto 

the transit network. Exhibit 2.1 depicts the 

flowchart of the DFX process, commonly 

referred to as the four-step transportation 

modeling process. The DFX model application 

is written by NCTCOG staff in the TransCAD 

script language known as the Geographic 

Information System Developer Kit (GISDK), 

and integrated with a user interface 

developed in visual basic programming 

language.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 9

Exhibit 2.1: DFW Expanded Travel Model Process Forecast Flowchart

DEMOGRAPHIC INFORMATION ZONAL INFORMATION

ROADWAY NETWORK

TRANSIT NETWORK

INPUT

TRIP GENERATION

TRIP DISTRIBUTION

MODE CHOICE

ROADWAY ASSIGNMENT

TRAVEL TIME CONVERGENCE

TRANSIT ASSIGNMENT

ROADWAY SKIM DEVELOPMENT

TRANSIT SKIM DEVELOPMENT

YES NO

DECISION PROCESS LEGEND
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 10

Trip Generation Model

The Trip Generation Model is a computer 

program written in GISDK script language by 

NCTCOG staff. The Trip Generation Model 

converts the population and employment 

data into person trip ends and outputs the 

total number of trips produced by and 

attracted to each zone by trip purpose. The 

2012, 2014, 2017, 2020, 2023, 2026, and 

2028 population and employment forecasts 

were generated with the Disaggregate 

Residential Allocation Model/Employment 

Allocation Model using travel times from 

the Roadway and Transit Assignment Steps

consistent with current planning practice. 

The data can be seen in Exhibit 2.2. The 

cross-classified trip production model is 

stratified by income quartile and household 

size. The allocation of TSZ households into 

the four income quartiles and six household 

size categories is based on distribution 

curves developed from the US Census 

Population data. The cross-classified trip 

attraction model is stratified by area type, 

employment type (basic, retail, and 

service), and, for the case of the HBW trip 

purpose, income quartile. Area type 

designations are a function of the 

population and employment density of a 

zone.

Exhibit 2.2: Socio-economic Demographic Summary

Socio-economic Demographic Summary By County

2012 2014 2017 2020 2023 2026 2028

Population 6,381,750 6,616,981 6,979,143 7,345,926 7,735,614 8,138,777 8,425,438 

Number of Households 2,321,348 2,399,456 2,518,598 2,638,704 2,765,501 2,896,288 2,988,707 

Employment Types

Basic 992,680 1,016,468 1,047,494 1,076,044 1,105,453 1,136,319 1,158,627 

Retail

 566,421 478,639 447,911 467,615 488,520 510,351 525,789 

Service 2,427,176 2,679,536 2,928,246 3,111,986 3,313,504 3,519,420 3,662,658 

Total Employment 3,986,277 4,174,643 4,423,651 4,655,645 4,907,477 5,166,090 5,347,074 

The Trip Generation Model allows the user 

to input trip rates and trip generation units 

associated with special generators such as 

regional shopping malls, hospitals, and 

colleges/universities. At the end of the 

generation process, HBW trips are balanced 

to the estimated trip attractions. All other 

purposes are balanced to the estimated trip 

productions in that zone. Because of the 

uniqueness of the NHB trips, zonal 

productions for NHB trips are later set equal 

to the attractions in a given zone.

The regional trip productions and attractions 

are balanced for each trip purpose. The total 

trip attractions are balanced to the 

estimated trip productions in that zone for 

all other trip purposes.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 11

Trip Distribution Model

The Trip Distribution Model creates the 

production-attraction person trip tables for 

each of the 5,386 model zones. The Trip 

Distribution Model uses the person trips 

produced by and attracted to each zone 

generated in the Trip Generation Model,

plus zone-to-zone minimum travel time 

information from the roadway network to 

estimate the number of person trips 

between each pair of zones for each trip 

purpose. All estimates of roadway travel 

times include a representation of the time 

needed for locating a parking space, paying 

for parking, and walking from the car to the 

final destination. Estimates of these 

terminal times were derived from NCTCOG’s 

1994 Workplace Survey and 1996 Household 

Travel Survey. NCTCOG is in the process of 

updating the trip distribution model 

component based on 2009 household survey 

data. The model uses a gamma-based 

gravity formulation technique to estimate 

the zone-to-zone interchange of trips. 

Iterations of the gravity model are required 

to ensure that the estimated number of 

zonal trips received equals the projected 

number of trip attractions generated by the 

Trip Generation Model.

Mode Choice Model

The Mode Choice Model determines the 

mode of travel and auto occupancy. Using 

the information regarding trip maker 

characteristics (e.g., income and auto 

ownership), roadway and transit system 

characteristics (e.g., in-vehicle time and outof-vehicle time), and travel costs (e.g., auto 

operating costs, parking costs, and transit 

fare), the model splits the trips among all 

applicable modes of travel. The model uses 

a nested logic formulation for all the trip 

purposes. The “Other” trips are assumed to 

be vehicle trips with one occupant and are 

not processed by the Mode Choice Model. 

The trip purposes of HBW, HNW, and NHB 

have nine choice sets: Drive Alone, Two 

Occupant Shared Ride, Three + Occupancy 

Shared Ride, Walk Access to Bus Service, 

Auto Access to Bus Service, Walk Access to 

Rail Service, Auto Access to Rail Service, 

Walk Access to Bus and Rail Service with 

Transfer, and Auto Access to Bus and Rail 

Service with Transfer.

Roadway Assignment

The Roadway Assignment Model consists of 

simultaneous User Equilibrium OriginDestination assignments of drive alone, 

shared-ride, and truck vehicle classes for 

three separate time-of-day periods (6:30 am 

to 9:00 am Morning Peak, 3:00 pm to

6:30 pm Evening Peak, and the 18-hour OffPeak). The drive alone vehicle class is kept 

separate from the shared-ride vehicle class 

so that HOV assignments can be performed 

as an integral part of an equilibrium 

assignment. Trucks are kept separate from 

the other vehicle classes so that the 

modeled truck volumes on all links can be 

tracked, and a separate value-of-time can be 

defined for them. A generalized cost path 

building technique is embedded within the 

model, in which the iterative calculation of 

zone-to-zone impedances are based on 

weighting factors applied to the capacityrestrained travel time, the distance 

(representing fuel cost), and tolls. As is 

standard with all User Equilibrium 

procedures, the TransCAD program uses an 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 12

iterative process to achieve a convergent 

solution in which no travelers can improve 

their path by shifting routes. Since the 

results of the three time-of-day assignments 

can be combined to obtain total weekday 

modeled volumes, validation checks can be 

performed with either time-of-day or 

weekday observed traffic counts.

Speed Estimation Procedure

The link speed in the DFX is estimated by 

dividing the length of the link by its loaded 

travel time. The loaded travel time is the 

sum of the free-flow travel time, traffic 

congestion delay, and the delay caused by 

the traffic control devices (e.g., stop signs, 

yield signs, and signals). These three 

elements of the loaded travel time are all 

functions of the link volume to capacity 

ratio. These functions are programmed in 

the volume delay function (VDF) that is an 

essential input to the traffic assignment step. 

The result of the traffic assignment step is 

the final time-period-specific average loaded 

speeds for each of the 30,000+ links in the 

roadway network. The VMT and vehicle 

hours of travel (VHT) for different time 

periods is included in the output as well to 

obtain an overall average speed (VMT/VHT) 

for any desired length of time.

The free-flow (uncongested) speed is 

defined as the speed limit. Free-flow speeds 

are an important link attribute since they are 

the base for calculating the congested 

(loaded) speeds in the Traffic Assignment 

step.

The VDF in the DFX uses a conical congestion 

delay form defined for each link functional 

classification, a non-linear delay curve based 

on the Webster’s uniform delay formulation 

at signalized intersections, and a linear delay 

curve for the stop and yield controlled 

approaches.

The volume-delay curves were calibrated 

based on the available 2004 daily link traffic 

counts at more than 10,000 locations 

(collected by the Texas Department of 

Transportation [TxDOT]), and the travel time 

runs along freeway and arterial corridors 

(performed by several consultants as part of 

other projects). The time-of-day link counts 

were not available for the calibration of the 

model in each time period.

Finally, all of the delay elements are added 

to the uncongested travel time (based on 

the free-flow speeds) to produce the total 

loaded travel time on each roadway 

segment. Appendix E contains speeds by 

county for each hour of the day. The 

resulting congested DFX county speeds are 

listed in Exhibit 2.3.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 13

Exhibit 2.3: Average Congested Speeds

County 2012 2014 2017 2020 2023 2026 2028

Collin 36.18 35.75 36.39 35.14 34.61 32.99 32.68

Dallas 36.36 36.13 36.31 35.89 35.42 34.91 34.90

Denton 36.67 36.09 36.78 36.41 35.87 34.96 34.86

Ellis 45.71 45.35 46.87 46.33 45.91 44.91 44.54

Johnson 41.62 41.69 42.14 41.61 41.38 40.80 40.37

Kaufman 46.04 45.57 45.85 44.63 43.65 42.27 40.73

Parker 44.85 44.58 45.42 44.99 44.65 44.07 43.86

Rockwall 41.28 40.57 40.80 39.53 38.98 37.55 36.16

Tarrant 37.06 36.96 37.51 36.90 36.21 35.48 35.63

Local Street VMT

The roadway network of the DFX does not 

contain the details of local (residential) 

streets; however, a VMT estimate is possible 

based on data provided by the travel model. 

Local street VMT is calculated for each 

county by multiplying the number of 

intrazonal trips by the intrazonal trip length 

and then adding the VMT from the zone 

centroid connectors. The temporal 

distribution is assumed to be the same as for 

non-local streets.

Adjustments

Seasonal, Daily, and Hourly Adjustments

The vehicle activity data used for this 

analysis is representative of the summer 

season. This section outlines the process 

used to convert the DFX non-summer 

weekday activity to summer (June, July, and 

August) weekday activity. Automatic Traffic

Recorder (ATR) data, collected by the Texas 

Department of Transportation (TxDOT), is 

used to calculate the necessary conversions. 

2012 ATR data was used for all analysis 

years. Exhibit 2.4 lists the stations used in 

this analysis and Exhibit 2.5 is a map showing 

the ATR locations.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 14

Exhibit 2.4: ATR Stations

Station Name Road County

1 A301 ARLINGTON US0080 Tarrant

2 S016 JACKSBORO US0281 Jack

3 S017 DALLAS US0175 Dallas

4 S026 MCKINNEY SH0005 S Collin

5 S027 DENTON FM0428 S Denton

6 S040 CORSICANA IH0045 Navarro

7 S055 DALLAS SH0183 Dallas

8 S121 MCKINNEY US0075 Collin

9 S126 DALLAS IH035E Dallas

10 S130 FT. WORTH IH0030 Tarrant

11 S133 TERRELL US0080 Kaufman

12 S145 TERRELL IH0020 Kaufman

13 S148 DALLAS IH035E Dallas

15 S171 DALLAS IH0635 Dallas

17 S192 ARLINGTON IH0030 Tarrant

18 S193 FT. WORTH IH0820 Tarrant

19 S208 WEATHERFORD IH0020 Parker

20 S220 DALLAS IH0045 Dallas

24 S264 WISE SH0114 Wise

26 S292 ERATH US0067 Erath

28 S297 TARRANT IH0020 Tarrant

29 S337 WISE SH 114 Wise

30 S338 WISE USE 380 Wise

31 S339 WISE US0081 Wise

32 S340 HOOD US0377 Hood

33 S341 PALO PINTO IH0020 Palo Pinto
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 15

Exhibit 2.5: ATR Station Map

Seasonal and Daily Adjustments

ATR data is organized into five day types: 

Sunday, Monday, Midweek (Tuesday, 

Wednesday, and Thursday), Friday, and 

Saturday. To adjust the representative 

average school season weekday (ASWT) 

data from the DFX to summer weekday, an

ASWT to summer ATR conversion ratio is 

calculated. The summer portion of the ratio 

includes traffic volumes recorded between 

June and August. Seasonal midweek

(Tuesday-Thursday) adjustments by area 

type for DFX counties are listed in Exhibit 

2.6. 2012 Midweek adjustment factors 

were used for all analysis years.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 16

Exhibit 2.6: Seasonal/Daily Adjustment Factors

County Type Midweek

2012, 2014, 2017, 2020, 

2023, 2026, and 2028

DFX Counties (ASWT to 

Summer)

Core 

(Dallas/Tarrant) 0.991

Rural 

(Collin/Denton) 0.971

Perimeter 

(Other Counties) 1.030

Hourly Adjustments

Daily volumes recorded for each of the five 

day types described above are aggregated 

by hour to determine the percent of daily 

traffic occurring during each hour, 

representing hourly vehicle activity 

estimates. The DFX county midweek is 

further detailed by utilizing a time period 

volume for aggregation, as opposed to the 

daily volumes provided for the other day 

types. These time periods correspond to 

the time periods utilized in the DFX where 

AM Peak is 6:30 am to 8:59 am, PM Peak is 

3:00 pm to 6:29 pm, and Off-Peak 

represents all other hours of the day 

(12:00 am to 6:29 am, 9:00 am to 2:59 pm, 

and 6:30 pm to 11:59 pm). Periods split by 

mid-hour times utilize an equal division of 

traffic recorded during the hour. Exhibit 

2.7 shows the hourly adjustments for DFX 

counties for the summer season.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 17

Exhibit 2.7: Hourly Adjustment Factors for the DFW Four-County and

Nine-County Modeling Domains

Sunday Monday Midweek Friday Saturday

12:00 am – 12:59 am 2.15% 0.92% 0.95% 1.78% 2.15%

1:00 am – 1:59 am 1.52% 0.63% 0.66% 1.19% 1.52%

2:00 am – 2:59 am 1.34% 0.59% 0.63% 1.05% 1.34%

3:00 am – 3:59 am 0.91% 0.64% 0.63% 0.81% 0.91%

4:00 am – 4:59 am 0.78% 1.10% 1.00% 0.90% 0.78%

5:00 am – 5:59 am 1.08% 2.72% 2.35% 1.52% 1.08%

6:00 am – 6:29 am 0.81% 2.70% 2.33% 1.27% 0.81%

6:30 am – 6:59 am 0.81% 2.70% 2.33% 1.27% 0.81%

7:00 am – 7:59 am 2.15% 7.02% 6.11% 3.43% 2.15%

8:00 am – 8:59 am 3.02% 6.18% 5.49% 4.37% 3.02%

9:00 am – 9:59 am 4.28% 5.19% 4.84% 5.18% 4.28%

10:00 am – 10:59 am 5.56% 4.96% 4.90% 5.89% 5.56%

11:00 am – 11:59 am 6.20% 5.20% 5.29% 6.41% 6.20%

12:00 pm – 12:59 pm 7.29% 5.42% 5.59% 6.70% 7.29%

1:00 pm – 1:59 pm 7.70% 5.57% 5.82% 6.77% 7.70%

2:00 pm – 2:59 pm 7.63% 5.95% 6.23% 6.77% 7.63%

3:00 pm – 3:59 pm 7.54% 6.68% 6.85% 6.77% 7.54%

4:00 pm – 4:59 pm 7.48% 7.49% 7.29% 6.67% 7.48%

5:00 pm – 5:59 pm 7.24% 7.81% 7.35% 6.50% 7.24%

6:00 pm – 6:29 pm 3.25% 3.09% 3.16% 2.99% 3.25%

6:30 pm – 6:59 pm 3.25% 3.09% 3.16% 2.99% 3.25%

7:00 pm – 7:59 pm 5.39% 4.38% 4.96% 5.00% 5.39%

8:00 pm – 8:59 pm 4.38% 3.41% 3.84% 4.14% 4.38%

9:00 pm – 9:59 pm 3.65% 2.88% 3.32% 3.78% 3.65%

10:00 pm – 10:59 pm 2.76% 2.20% 2.83% 3.32% 2.76%

11:00 pm – 11:59 pm 1.85% 1.48% 2.09% 2.53% 1.85%

Model VMT Adjustments (HPMS vs. DFX)

Consistent with previous emission inventory 

practices, the DFW MPO used TxDOT’s

Highway Performance Monitoring System 

(HPMS) data to adjust modeled VMT to 

reflect the HPMS data for consistent 

reporting across the State. This adjustment 

is based on EPA’s guidance for emission 

inventory development.

Prior to beginning the development of 

these emission inventories for the

Redesignation Substitute State

Implementation Plan, NCTCOG performed a 

validation on the DFX model in order to 

meet the transportation conformity 

requirements per the Code of Federal 

Regulations, which states, “Network-based 

travel models must be validated against 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 18

observed counts (peak and off-peak, if 

possible) for a base year that is not more 

than 10 years prior to the date of the 

conformity determination” (40CFR 

§93.122(b)(1)(i). The previous DFX 

validation was performed in 2004, 

triggering an update to the validation. In 

order to be consistent with the planning 

assumptions incorporated in the 2014 

Transportation Conformity, NCTCOG

incorporated the updated DFX model

validation which is based on 2010 

demographics. Exhibit 2.8 shows the

calculation performed to develop the new 

HPMS adjustment factor, 0.9703, based on 

a comparison of 2010 VMT for HPMS and 

DFX. 

Exhibit 2.8: 2010 DFW and HPMS VMT Analysis

Model VMT Adjustment Factor

2010 VMT

HPMS (ASWT)1 165,292,084

DFX (ASWT) 170,346,118

HPMS/DFX Ratio 0.9703

1Annual Average Daily Traffic to ASWT conversion factor applied.

Nonrecurring Congestion

According to a paper published in the 

January 1987 Institute of Transportation 

Engineers Journal by Jeffrey A. Lindley 

entitled Urban Freeway Congestion: 

Quantification of the Problem and 

Effectiveness of Potential Solutions, 

congestion due to traffic incidents accounts 

for twice as much as congestion from 

bottleneck situations. Congestion due to 

incidents, or nonrecurring congestion, 

causes emissions not represented in the 

VMT-based calculations of the base 

emissions. In order to include these effects, 

the delay caused by nonrecurring 

congestion is added to the freeway travel 

times and congestion delay due to 

bottlenecks to obtain an increased freeway 

travel time, which translates into reduced 

speed on freeway facilities. Reducing the 

freeway speeds increases volatile organic 

compounds (VOC) and oxides of nitrogen 

(NOX) emissions by 4.9 percent, resulting in 

a factor of 1.049 for freeway VOC and NOX

emissions in urban and rural counties. This 

is thought to be a conservative estimate of 

increased emissions due to nonrecurring 

congestion. Arterial street emissions are 

not significantly affected by incidents 

because alternate routes on the arterial 

system are generally available. Therefore, 

this factor is not applied to non-freeway 

type facilities.

VMT Estimates

The VMT estimates are located in Exhibit 2.9

for all counties in the nonattainment area. 

VMT is summarized by 2012, 2014, 2017,

2020, 2023, 2026, and 2028 analysis years

for each county. Appendix E contains the 

VMT by county for each hour for all counties.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 19

Exhibit 2.9: Vehicle Miles of Travel (Miles/Day)

COUNTY 2012 2014 2017 2020 2023 2026 2028

Collin 21,747,390 23,326,944 26,286,747 28,681,086 30,690,351 33,028,116 34,814,978

Dallas 72,537,006 75,096,046 80,630,330 84,495,542 87,760,530 91,354,976 95,690,598

Denton 17,698,236 18,800,191 20,960,059 23,077,361 24,809,322 26,220,152 28,168,734

Ellis 6,892,381 7,367,499 8,267,444 9,017,262 9,787,285 10,593,073 11,158,402

Johnson 5,150,957 5,617,011 6,180,756 6,562,122 6,977,379 7,478,108 7,863,226

Kaufman 5,816,886 6,254,501 7,027,324 7,688,720 8,303,318 9,031,372 9,682,475

Parker 4,681,023 5,045,329 5,651,650 6,108,185 6,577,402 6,983,513 7,309,865

Rockwall 2,346,421 2,483,024 2,730,556 2,933,304 3,086,717 3,325,878 3,577,270

Tarrant 46,985,504 49,681,164 54,781,427 57,550,132 60,592,476 63,743,735 67,044,186

Total 183,855,804 193,671,709 212,516,292 226,113,715 238,584,779 251,758,922 265,309,733
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 20

CHAPTER 3: EMISSION FACTOR ESTIMATION PROCEDURE

Mobile Model and Input Parameters

The Environmental Protection Agency’s 

(EPA) Motor Vehicle Emission Simulator 

version 2014 (MOVES2014), is used to 

develop 2012, 2014, 2017, 2020, 2023, 

2026, and 2028 vehicle emission factors for 

this analysis. The emission factors are one 

component in the equation to determine 

vehicle emissions emitted from the region’s 

on-road vehicles. MOVES2014 parameters 

used to develop these emissions inventories

are listed in Exhibits 3.1 through 3.5 with 

the appropriate data source and/or 

methodology applied. Information listed 

applies to all counties unless otherwise 

specified. Referenced files identifying 

specific local data are included in Appendix 

A. MOVES2014 input files utilizing these 

parameters and data for each county are 

included in Appendix B. 

Exhibit 3.1: MOVES2014 Modeled Pollutants

Command

Input Parameter 

Values and 

Molecular Formulas

Description

Pollutant NOX, VOC, CO, CO2, 

PM10 and PM2.5

Oxides of Nitrogen (NOX), Volatile Organic 

Compounds (VOC), Carbon Monoxide (CO),

Carbon Dioxide (CO2), and Particulate Matter 

with aerodynamic diameters equal to or less than

10 (PM10) and 2.5 microns (PM2.5).

Exhibit 3.2: MOVES2014 External Conditions

Command Input Parameter Values Description

Calendar Year 2012, 2014, 2017, 2020, 

2023, 2026, and 2028

One-hour and 1997 Eight-hour 

Redesignation analysis years

Evaluation Month 7 Summer

Minimum/Maximum 

Temperature N/A See Hourly Temperatures

Hourly Temperatures Average Summer

County specific, provided by the Texas 

Commission on Environmental Quality 

(TCEQ)

Relative Humidity Average Summer County specific, provided by TCEQ

Barometric Pressure Average Summer County specific, provided by TCEQ
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 21

Exhibit 3.3: MOVES2014 Input Parameters

Input Parameter Description Source

Source Type 

Population 

Input number of vehicles in geographic area to be 

modeled for each vehicle. Texas Transportation 

Institute’s (TTI) MOVESpopulationBuild module is used to 

convert MOVES2014 based Texas Department of Motor 

Vehicles (TxDMV) registration data for each county into 

13 MOVES2014 SUT population.

2012 and 2014 

TxDMV registration 

data

Source Type 

Age Distribution

Input provides distribution of vehicle counts by age for 

each calendar year and vehicle type. TxDMV registration 

data used to estimate age distribution of vehicle types up 

to 30 years. Distribution of Age fractions should sum up 

to 1.0 for all vehicle types for each analysis year.

2012 and 2014 

TxDMV registration 

data MOVES2014

default used for buses

Vehicle Type 

Vehicle Miles of 

Travel

County specific vehicle miles of travel (VMT) distributed 

to six highway performance monitoring system Vehicle 

types.

Travel Model Output

Average Speed 

Distribution

Input average speed data specific to vehicle type, road 

type, and time of day/type of day into 16 speed bins. 

Sum of speed distribution to all speed bins for each road 

type, vehicle type, and time/day type is 1.0.

Travel Model Output

Road Type 

Distribution 

(VMT Fractions)

Input county specific VMT by road type. VMT fraction 

distributed between the road type and must sum to 1.0 

for each source type.

Travel Model Output

Ramp Fraction Input county specific fraction of ramp driving time on 

rural and urban restricted roadway type.

Travel Model Output

Fuel Supply

Input to assign existing fuels to counties, months, and 

years, and to assign the associated market share for each 

fuel. 

TCEQ, EPA Fuel 

Surveys and default 

MOVES2014 input 

where local data 

unavailable

Meteorology Regional average summer data on temperature and 

humidity.

Local data from TCEQ

Fuel 

Formulation

Input county specific fuel properties in the MOVES2014

database. 

TCEQ, EPA Fuel 

Surveys, and default 

MOVES2014 input 

where local data 

unavailable
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 22

Exhibit 3.3: MOVES2014 Input Parameters (continued)

Input Parameter Description Source

Inspection and 

Maintenance

Coverage

Input inspection and maintenance (I/M) coverage record 

for each combination of pollutants, process, county, fuel 

type, regulatory class and model year are specified using 

this input.

Local data from TCEQ

Fuel Engine 

Fraction / Diesel 

Fraction (AVFT)

Input fuel engine fractions (i.e. Gasoline vs. Diesel 

Engines types in the vehicle population) for all vehicle 

types. 

2012 and 2014 

TxDMV registration 

data MOVES2014

default used for lightduty vehicles and 

buses
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 23

Exhibit 3.4: MOVES2014 I/M Descriptive Inputs for Subject Counties

2012, 2014, 2017, 2020, 2023, 2026, and 2028

Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant I/M Data

I/M Program ID 20 21 22 23 24

Identifies 

program 

number with 

MOVES2014

database 

Pollutant Process 

ID

101, 102, 

201, 202, 

301, 302,

101, 102, 

201, 202, 

301, 302,

101, 102, 

201, 202, 

301, 302,

112 112

Source Use Type 21, 31, 32 21, 31, 32 52, 54 21, 31, 32 21, 31, 32

Begin Model 

Year 1996 X X X 1996

End Model Year Y 1995 Y 1995 Y

Inspect

Frequency

1 1 1 1 1

Annual 

testing; 

program 

specifications

Test Standards

Description

Exhaust 

OBD 

Check

ASM 

2525/501 

5 Phase-in 

Cut Points

Twomode, 

2500 

RPM/Idle 

Test

Evaporative 

Gas Cap 

Check

Evaporative 

Gas Cap and 

OBD Check

I/M Compliance 93.12% for source type 21, 91.26% for source type 31 and 86.6% 

for source type 32*

Expected 

compliance 

(%)

Source: TCEQ

ASM – Acceleration Simulation Mode

RPM – Revolutions Per Minute

Note: Begin Model Year and End Model Year define the range of vehicle model years covered by I/M program. Begin Model 

Year, represented by “X” is calculated as YearID – 2 and End Model Year, represented by “Y” is calculated as YearID – 24.

*http://www.epa.gov/otaq/models/moves/documents/420b15007.pdf
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 24

Exhibit 3.5: MOVES2014 Fuel Properties

2012 and 2014 2017, 2020, 2023, 2026, and 

2028

Counties Core Perimeter All Core Perimeter All

Fuel Type Gasoline Diesel Gasoline Diesel

Fuel 

Formulation ID 9500 20670 9500 20670

Fuel Subtype ID 12 12 20 12 12 20

RVP 7.00 7.80 0.00 7.00 7.80 0.00

Sulfur Level 24.93 24.93 11.00 10.00 10.00 11.00

Ethanol Volume 9.69 9.69 9.69 9.69 9.69 0.00

Methyl Tertiary 

Butyl Ether 

(MTBE) Volume

0.00 0.00 0.00 0.00 0.00 0.00

Ethyl Tertiary 

Butyl Ether 

(ETBE) Volume

0.00 0.00 0.00 0.00 0.00 0.00

Tertiary Amyl 

Methyl Ether 

(TAME) Volume

0.00 0.00 0.00 0.00 0.00 0.00

Aromatic 

Content

13.76 13.76 13.76 13.76 13.76 0.00

Olefin Content 12.03 12.03 12.03 12.03 12.03 0.00

Benzene 

Content

0.44 0.44 0.44 0.44 0.44 0.00

e200 48.32 48.32 48.32 48.32 48.32 0.00

e300 84.70 84.70 84.70 84.70 84.70 0.00

Vol To Wt 

Percent Oxy

3.38 3.38 3.38 3.38 3.38 0.00

BioDiesel Ester 

Volume 0.00 0.00 0.00 0.00 0.00 0.00

Cetane Index 0.00 0.00 0.00 0.00 0.00 0.00

PAH Content 0.00 0.00 0.00 0.00 0.00 0.00

T50 205.41 205.41 205.41 205.41 205.41 0.00

T90 329.31 329.31 329.31 329.31 329.31 0.00
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 25

Area Specific Calculations and Procedures

SourceUse Type Distribution

Sourceuse type age distributions are 

calculated from the Texas Department of 

Transportation’s (TxDOT) vehicle 

registration data. July data sets of 

corresponding analysis years are utilized for

light- and heavy-duty vehicle classes. 

MOVES2014 default values are used for bus 

categories. Light-duty registration data for 

Collin, Dallas, Denton, Ellis, Hood, Hunt, 

Johnson, Kaufman, Parker, Rockwall, 

Tarrant, and Wise counties are weighted for 

commute patterns with the County-toCounty Worker Flow data from the 2006-

2010 Census. Exhibit 3.6 identifies the 

percentages applied for this weighted 

adjustment. The TTI methodology is 

applied to the heavy-duty vehicle data for 

developing registration for all heavy-duty 

vehicles. These files are included in 

Appendix B.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 26

Exhibit 3.6: County-to-County Worker Flow

Resident 

County

County of Employment

Collin Dallas Denton Ellis Hood Hunt Johnson Kaufman Parker Rockwall Tarrant Wise

Collin 65.4% 10.2% 5.1% 0.3% 0.1% 4.2% 0.2% 1.0% 0.0% 7.6% 0.9% 0.0%

Dallas 19.1% 66.0% 10.2% 10.7% 0.9% 3.9% 1.3% 15.8% 1.0% 23.6% 7.7% 0.7%

Denton 11.5% 7.9% 75.6% 0.4% 0.3% 0.0% 0.2% 0.7% 0.9% 0.6% 3.3% 3.1%

Ellis 0.2% 1.8% 0.2% 79.4% 0.2% 0.1% 1.4% 0.7% 0.1% 0.0% 0.6% 0.2%

Hood 0.0% 0.1% 0.0% 0.1% 84.0% 0.0% 2.3% 0.0% 2.4% 0.0% 0.5% 0.4%

Hunt 0.8% 0.4% 0.1% 0.1% 0.0% 84.3% 0.0% 4.4% 0.0% 9.4% 0.0% 0.0%

Johnson 0.0% 0.3% 0.3% 3.5% 3.2% 0.0% 76.2% 0.0% 1.4% 0.2% 3.2% 0.7%

Kaufman 0.3% 1.6% 0.1% 0.7% 0.1% 1.2% 0.0% 72.6% 0.0% 3.6% 0.1% 0.0%

Parker 0.0% 0.1% 0.1% 0.1% 4.3% 0.0% 0.5% 0.0% 77.4% 0.0% 2.6% 5.9%

Rockwall 0.7% 1.2% 0.1% 0.1% 0.5% 5.6% 0.1% 3.7% 0.0% 53.9% 0.1% 0.1%

Tarrant 2.0% 10.3% 7.4% 4.6% 6.2% 0.4% 17.5% 1.1% 14.1% 1.0% 80.3% 10.7%

Wise 0.1% 0.1% 0.8% 0.0% 0.2% 0.2% 0.3% 0.0% 2.5% 0.0% 0.8% 78.2%

Source: American Community Survey for the five-year period between 2006 and 2010.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 27

Fuel Engine Fractions

Diesel fractions for heavy-duty vehicle 

categories utilized state and regional

summed data from July registration data for 

modeling 2012, 2014, 2017, 2020, 2023, 

2026, and 2028 analysis years. July 2012

registration data is used for modeling 2012

and July 2014 is used for modeling 2017, 

2020, 2023, 2026, and 2028 analysis years.

Light-duty and bus categories utilize 

MOVES2014 default values. All diesel 

fraction files, included in Appendix B, list

specific data used for this analysis.

MOVES2014 Emission Factors

MOVES2014 emission factors for all the 

analysis years are reported in Appendix C.

Adjustments

Adjustments are applied to the emission 

factors in a post-process step. Texas Low 

Emission Diesel (TxLED) NOX Adjustment is 

applied to the emission factors. VMT Mix 

adjustment is applied simultaneously with 

the emission calculation procedure 

discussed in Chapter 4.

TxLED NOx Adjustment

The North Central Texas Council of 

Governments (NCTCOG) developed TxLED 

factors for the Dallas-Fort Worth (DFW)

region for the analysis years 2012, 2014, 

2017, 2020, 2023, 2026, and 2028 using the 

TCEQ Excel template 

(ftp://amdaftp.tceq.texas.gov/pub/Mobile_

EI/Statewide/mvs/txled/). The factors 

produced employed the TCEQ average 

diesel source use types (SUT) NOX

adjustments using 4.8 percent reductions 

for 2002 and later, and 6.2 percent

reductions for 2001 and earlier model years 

NOX reductions are from the EPA 

Memorandum, Texas Low Emission Diesel 

(LED) Fuel Benefits, September 2001). The 

TxLED analyses employed 2011 and 2014

regional age distribution factors for 

MOVES2014 runs. NOX, nitrogen oxide (NO), 

and nitrogen dioxide (NO2) emissions for 

Dallas County (DFW Area representative 

county) for all vehicle models years were 

produced for all analysis years. 

MOVES2014 emissions were extracted from 

the MOVES2014 output table. The 

extracted emissions were used in the 

template to estimate TxLED factors for all 

diesel vehicles for the pollutants NOX, NO, 

and NO2. Exhibit 3.7 shows the TxLED 

factors used.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 28

Exhibit 3.7: TxLED NOx Adjustments

Source Use Type

Adjustment Factors

2012 2014 2017 2020 2023 2026 2028

Passenger Car 0.94161 0.94409 0.94843 0.95087 0.95153 0.95169 0.95162 

Passenger Truck 0.94672 0.94749 0.94955 0.95020 0.95060 0.95062 0.95132 

Light Commercial 

Truck 0.94337 0.94400 0.94667 0.94817 0.94942 0.95000 0.95024 

Intercity Bus 0.94173 0.94199 0.94258 0.94387 0.94505 0.94666 0.94819 

Transit Bus 0.94196 0.94223 0.94282 0.94407 0.94547 0.94721 0.94892 

School Bus 0.94207 0.94231 0.94280 0.94395 0.94527 0.94690 0.94863 

Refuse Truck 0.94405 0.94465 0.94580 0.94739 0.94915 0.95083 0.95154 

Single Unit ShortHaul Truck 0.94937 0.94970 0.95108 0.95154 0.95179 0.95194 0.95198 

Single Unit LongHaul Truck 0.94969 0.95006 0.95122 0.95157 0.95178 0.95191 0.95196 

Motor Home 0.94402 0.94440 0.94534 0.94678 0.94790 0.94925 0.95042 

Combination 

Short-Haul Truck 0.94644 0.94727 0.94887 0.94986 0.95086 0.95151 0.95177 

Combination 

Long-Haul Truck 0.94415 0.94495 0.94684 0.94809 0.94978 0.95081 0.95130 

Source: NCTCOG

Sourceusetype Population

TxDOT registration data was used for 

developing sourceusetype population for 

the DFW area. July 2012 registration data is 

used for developing 2012 sourceusetype 

population and July 2014 registration date

is used for developing 2014, 2017, 2020, 

2023, 2026, and 2028 analysis years

sourceusetype population. For years 2017, 

2020, 2023, 2026, and 2028, VMT growth 

rate was used to forecast sourceusetype 

population. All analysis sourceusetype 

population files are included in Appendix B. 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 29

Exhibit 3.8: Population for the DFW Four-County and Nine-County Modeling Domains

2012 2014 2017 2020 2023 2026 2028

Collin 585,036 620,227 686,428 724,097 764,527 807,551 850,693 

Dallas 1,691,351 1,767,818 1,956,518 2,063,880 2,179,121 2,301,755 2,424,710

Denton 471,003 503,003 556,692 587,238 620,032 654,927 689,907

Ellis 126,882 125,962 139,404 147,055 155,266 164,004 172,763

Johnson 120,315 124,429 137,712 145,265 153,379 162,012 170,665

Kaufman 77,503 81,717 90,440 95,401 100,728 106,397 112,080

Parker 95,330 100,729 111,481 117,596 124,163 131,151 138,157

Rockwall 63,637 66,227 73,301 77,323 81,639 86,234 90,839

Tarrant 1,319,720 1,377,959 1,525,046 1,608,726 1,698,552 1,794,145 1,889,986

Four-County 

Total 4,067,110 4,269,007 4,724,684 4,983,941 5,262,232 5,558,378 5,855,296

Nine-County 

Total 4,550,777 4,768,071 5,277,022 5,566,581 5,877,407 6,208,176 6,539,800

Vehicle Miles of Travel Mix (or Fractions)

(VMT Mix)

VMT Mix is applied to the emission factors 

in a post-process methodology. The VMT 

mix enables assignment of emission factors 

by vehicle type to a total volume to 

calculate emissions on a link or functional 

class. VMT mix is estimated for rural and 

urban freeways, arterials, collectors and 

high occupancy vehicle lanes for three time 

periods: AM-Peak, PM-Peak and Off-Peak.

Vehicle counts reported in the latest 

available TxDOT Vehicle Classification 

Report provide a base for the distribution of 

vehicles by type and functional class for the 

freeway, arterial, and collector VMT Mixes. 

The number of vehicles in each of the 12

axle-based categories are combined into 

intermediate groups, and then 

disaggregated into MOVES2014 SUT by 

applying appropriate TxDOT registration 

data and/or MOVES2014 defaults. Exhibit 

3.9 outlines this process. 

For each functional class, the values are 

aggregated across the total vehicles to 

determine the fraction of vehicles from 

each class. Motorcycles are allocated as 0.1 

percent for each functional class, 

subtracted from the Light-Duty Gasoline 

Vehicles category.

This “temporary” VMT mix calculation is 

then redistributed using local truck and 

non-truck splits identified by the DFX 

model. This process is performed for each 

of the three functional classes and three 

time periods, where AM peak is 6:30 am to

8:59 am, PM peak is 3:00 pm to 6:29 pm, 

and Off-Peak represents all other hours of 

the day. Motorcycles, light-duty vehicles, 

and two-axle light-duty trucks are classified 

as non-trucks. Trucks and heavy-duty 

vehicles with three axles or more, to include 

buses, are defined as trucks. 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 30

Exhibit 3.9: Vehicle Classification Process

Axle-Based Vehicle 

Classifications

Intermediate 

Groups/HPMSVtypeID Detailed Groups

C

Passenger 

Vehicles

PV

Passenger 

Vehicles (20) Passenger Car

Passenger Gasoline Vehicle

Passenger Diesel Vehicle

Motorcycle (MC)^

P

2 Axle, 4 

Tire Single 

Unit

Light Duty 

Trucks (30)

Passenger 

Truck

Passenger Gasoline Truck

Passenger Gasoline Truck

Light 

Commercial 

Truck

Light Commercial Gasoline 

Truck

Light Commercial Gasoline 

Truck

B Buses Bus Buses (40)

School Bus

Gasoline School Bus*

Diesel School Bus*

Transit Bus

Gasoline Transit Bus*

Diesel Transit Bus*

Diesel Intercity Bus*

SU2

2 Axle, 6 

Tire Single 

Unit

Heavy 

Duty 

Trucks

Single Unit 

Heavy-Duty 

Vehicles (50)

Single Unit ShortHaul Truck

Single Unit Short-Haul 

Gasoline Truck*

SU3 3 Axle, 

Single Unit Single Unit Short-Haul 

Diesel Truck*

SU4 4+ Axle, 

Single Unit

Single Unit LongHaul Truck

Single Unit Long-Haul 

Gasoline Truck*

SE4

3 or 4 Axle, 

Single 

Trailer

Single Unit Long-Haul 

Diesel Truck*
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 31

Exhibit 3.9: Vehicle Classification Process (continued)

Source: Dallas-Fort Worth Ozone Nonattainment Area SIP Support, 2013, Texas Transportation Institute.

^Motorcycles are allocated as 0.1 percent for each functional class, subtracted from the light-duty vehicles.

*Categories calculated using MOVES2014 defaults.

Axle-Based Vehicle 

Classifications

Intermediate 

Groups/HPMSVtypeID Detailed Groups

SE5

5 Axle, 

Single 

Trailer

Heavy 

Duty 

Trucks

Combination 

Heavy-Duty 

Vehicles (60)

Combination ShortHaul Truck

Combination Short-Haul 

Gasoline Truck*

SE6

6+ Axle, 

Single 

Trailer

SD5

5 Axle, 

Multi 

Trailer

Combination Short-Haul 

Diesel Truck*

SD6

6 Axle, 

Multi 

Trailer Combination Long-haul Diesel Truck*

SD7

7+ Axle, 

Multi 

Trailer
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 32

CHAPTER 4: EMISSION CALCULATION PROCEDURE

Emissions estimates are calculated using 

“TTI emissions inventory estimation utilities 

using moves: movesutl” developed by the 

Texas Transportation Institute (TTI). This 

software combines vehicle activity and 

emission factors to create emission 

estimates. Exhibit 4.1 outlines the emission 

calculation modeling process that is used to 

calculate the emissions estimates for the 

Dallas-Fort Worth ozone nonattainment 

area. Rate per Distance, Rate per Vehicle, 

and Rate per Profile are applied for DFW 

Expanded Travel Demand Model (DFX)

counties outlined in the following sections. 

Exhibit 4.1: MOVES2014 Emission Calculation Modeling Process

TRAVEL DEMAND MOVES2014

POPULATION BUILD

MOVES2014 EPA MODEL 

LINK LEVEL 

VMT & SPEED

POPULATION 

BY SOURCE USE 

TYPE

EMISSION 

RATES

LED NOX 

ADJUSTMENT 

FACTORS

ADJUSTED 

EMISSION 

RATES

MOVES2014

RATE ADJUST 

MOVES2014 EMISSION 

CALCULATIONS 

LINK LEVEL EMISSIONS

EMISSION SUMMARY TAB FILES

BY POLLUTANT, BY FACILITY TYPE, BY TIMES OF DAY

LEGEND

MODEL

INPUT/ 

OUTPUT
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 33

Emission Estimation

The DFX captures the vehicle activity 

information for each roadway segment in 

the transportation network in Collin, Dallas, 

Denton, Ellis, Johnson, Kaufman, Parker, 

Rockwall, and Tarrant counties as discussed 

in Chapter 1. Emission estimation using 

Motor Vehicle Emission Simulator version 

2014 is broken down into three phases.

Rate Per Distance

These include emissions for the processes 

occurring while vehicles are operating (i.e.,

running exhaust tire wear, brake wear, 

evaporative permeation, evaporative fuel 

vapor venting, evaporative fuel leaks, 

crankcase running exhaust, refueling 

displacement, and refueling spillage). The

quantity of emissions estimated is directly 

related to the activity.

Application of emission factors to each of 

these roadway network links requires 

assignment of vehicle miles of travel (VMT)

mix, also known as VMT mix, and 

coordination of functional classes. First, an 

appropriate VMT mix is identified for each 

link. For principal and minor arterials, 

frontage roads, collectors, zone connectors, 

and intrazonal functional, rural or urban 

unrestricted access emission rates are 

applied depending on the area type the link 

represents. For Interstate, freeways, and 

high occupancy vehicle lanes, rural or urban 

restricted access emission rates are applied 

depending on the area type the link 

represents. Exhibit 4.2 shows the area type 

used to apply emission rates. Links that fall 

under area type 1-4 are applied with an 

urban restricted/ unrestricted emission rate 

and links that fall under area type 5 are 

applied with a rural restricted/unrestricted

emission rate. Emission factors are specific 

to the speed identified on the roadway 

segments.

Exhibit 4.2: DFX Area Type

Area Type Description Activity Density Range 

(Per Acre)

1 Central Business District > 125 

2 Outer Business District 30-125 

3 Urban Residential 7.5-30 

4 Suburban Residential 1.8-7.5 

5 Rural <1.8 

Rate Per Vehicle

These include emissions for most processes 

that occur while vehicles are stationary (i.e., 

start exhaust, start crankcase, permeation, 

liquid leaks, and extended idle (long haul 

combination trucks only).

Rate Per Profile

These include emissions from the vapor 

venting process when vehicles are 

stationary. Vapor venting emissions vary 

depending on activity and previous 

temperatures. Rate per profile and rate per 

vehicle-based emissions are directly related 

to the source type population.
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 34

CHAPTER 5: SUMMARY OF VEHICLE MILES OF TRAVEL, SPEED, AND EMISSIONS

Summary emissions results are available in 

this chapter.

Vehicle Miles of Travel Estimates

The vehicle miles of travel (VMT) by county 

is summarized in Exhibit 5.1. Appendix E 

contains the summarized VMT estimates by 

the analysis year and time-of-day (TOD) for 

the counties.

Speed Estimates

Appendix E contains the summarized speeds 

by the analysis year and TOD for the 

counties.

Emission Estimates

The final county emission estimates for each 

analysis year are summarized in Exhibit 5.2. 

Appendix G contains the detailed emissions 

by pollutant, day, and TOD for all counties.

Appendix D contains the detailed tab 

summary of VMT, speeds, and emissions for 

all counties by analysis year, TOD, functional 

class, and vehicle type. 
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 35

Exhibit 5.1: VMT by County 

COUNTY 2012 2014 2017 2020 2023 2026 2028

Collin 21,747,390 23,326,944 26,286,747 28,681,086 30,690,351 33,028,116 34,814,978

Dallas 72,537,006 75,096,046 80,630,330 84,495,542 87,760,530 91,354,976 95,690,598

Denton 17,698,236 18,800,191 20,960,059 23,077,361 24,809,322 26,220,152 28,168,734

Ellis 6,892,381 7,367,499 8,267,444 9,017,262 9,787,285 10,593,073 11,158,402

Johnson 5,150,957 5,617,011 6,180,756 6,562,122 6,977,379 7,478,108 7,863,226

Kaufman 5,816,886 6,254,501 7,027,324 7,688,720 8,303,318 9,031,372 9,682,475

Parker 4,681,023 5,045,329 5,651,650 6,108,185 6,577,402 6,983,513 7,309,865

Rockwall 2,346,421 2,483,024 2,730,556 2,933,304 3,086,717 3,325,878 3,577,270

Tarrant 46,985,504 49,681,164 54,781,427 57,550,132 60,592,476 63,743,735 67,044,186

Four-County 

Total 158,968,136 166,904,345 182,658,563 193,804,121 203,852,679 214,346,979 225,718,496

Nine-County 

Total 183,855,804 193,671,709 212,516,292 226,113,715 238,584,779 251,758,922 265,309,733

Exhibit 5.2: Final Emission Estimates by County

Oxides of Nitrogen (NOX) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 22.06 19.37 13.06 9.77 7.90 6.48 5.58

Dallas 78.90 66.87 43.32 30.32 23.24 18.14 16.40

Denton 20.83 18.30 12.02 9.18 7.44 6.16 5.84

Ellis 13.83 12.50 9.92 8.05 7.35 6.71 6.62

Johnson 7.83 7.16 5.29 4.13 3.57 3.13 3.03

Kaufman 10.65 9.66 7.48 6.17 5.47 5.01 4.97

Parker 9.74 8.85 7.56 6.37 5.75 5.32 5.26

Rockwall 3.49 3.07 2.20 1.56 1.29 1.11 1.05

Tarrant 49.41 42.88 28.35 20.40 15.86 12.54 11.00

Total 216.74 188.65 129.19 95.95 77.87 64.62 59.75
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 36

Exhibit 5.2: Final Emission Estimates by County (continued)

Nitrogen Oxide (NO) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 19.68 17.12 11.29 8.22 6.42 5.01 4.28

Dallas 70.43 59.16 37.58 25.76 19.17 14.29 12.71

Denton 18.56 16.11 10.31 7.62 5.92 4.65 4.31

Ellis 12.30 10.89 8.22 6.32 5.41 4.64 4.45

Johnson 6.98 6.29 4.47 3.34 2.73 2.25 2.12

Kaufman 9.44 8.40 6.18 4.83 4.03 3.46 3.34

Parker 8.65 7.69 6.24 4.98 4.23 3.68 3.54

Rockwall 3.11 2.69 1.86 1.28 1.00 0.81 0.75

Tarrant 44.19 38.03 24.70 17.39 13.15 9.95 8.66

Total 193.33 166.38 110.85 79.73 62.07 48.75 44.16

Nitrogen Dioxide (NO2) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 2.21 2.10 1.67 1.48 1.42 1.42 1.26

Dallas 7.84 7.17 5.39 4.32 3.89 3.70 3.56

Denton 2.10 2.04 1.61 1.49 1.45 1.46 1.49

Ellis 1.43 1.51 1.62 1.66 1.88 2.03 2.12

Johnson 0.78 0.81 0.78 0.76 0.81 0.86 0.89

Kaufman 1.12 1.19 1.24 1.29 1.40 1.51 1.58

Parker 1.02 1.09 1.26 1.34 1.47 1.59 1.67

Rockwall 0.35 0.35 0.32 0.27 0.28 0.29 0.29

Tarrant 4.83 4.51 3.42 2.85 2.58 2.49 2.25

Total 21.68 20.76 17.30 15.46 15.17 15.35 15.11
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 37

Exhibit 5.2: Final Emission Estimates by County (continued)

Volatile Organic Compounds (VOC) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 10.22 9.41 7.50 6.44 5.77 5.02 4.57

Dallas 35.18 31.37 24.15 20.04 17.68 15.22 14.03

Denton 8.74 8.13 6.34 5.44 4.85 4.21 3.91

Ellis 3.84 3.50 2.79 2.38 2.16 1.94 1.86

Johnson 2.87 2.67 2.11 1.79 1.59 1.39 1.31

Kaufman 2.83 2.62 2.05 1.76 1.57 1.41 1.37

Parker 2.68 2.50 2.08 1.82 1.63 1.47 1.42

Rockwall 1.39 1.26 1.00 0.82 0.73 0.64 0.60

Tarrant 24.41 22.29 17.60 14.89 13.22 11.41 10.43

Total 92.17 83.75 65.62 55.36 49.21 42.70 39.49

Carbon Monoxide (CO) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 126.76 123.97 115.29 109.04 101.58 89.02 81.25

Dallas 473.43 446.79 397.80 365.15 331.65 285.93 263.13

Denton 102.10 99.84 90.16 86.11 79.35 68.48 63.63

Ellis 39.65 38.80 35.43 33.57 31.75 28.41 26.61

Johnson 31.75 31.62 27.99 25.66 23.66 20.86 19.35

Kaufman 32.00 31.58 28.82 27.25 25.74 23.20 22.16

Parker 31.87 31.22 28.17 25.96 24.18 21.14 19.67

Rockwall 14.16 13.62 12.16 11.14 10.21 9.02 8.56

Tarrant 309.81 300.03 274.36 252.78 231.75 202.48 189.69

Total 1,161.55 1,117.46 1,010.18 936.65 859.88 748.53 694.05
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 38

Exhibit 5.2: Final Emission Estimates by County (continued)

Carbon Dioxide (CO2) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 11,768 12,399 13,272 13,654 13,549 13,531 13,523 

Dallas 39,784 40,474 41,700 41,232 39,806 38,270 38,069 

Denton 9,898 10,341 10,854 11,205 11,087 10,841 11,045 

Ellis 4,356 4,598 5,044 5,263 5,386 5,480 5,565 

Johnson 3,005 3,217 3,426 3,461 3,452 3,455 3,483 

Kaufman 3,487 3,695 4,026 4,194 4,257 4,339 4,474 

Parker 3,011 3,180 3,467 3,579 3,636 3,659 3,700 

Rockwall 1,328 1,385 1,461 1,475 1,452 1,454 1,495 

Tarrant 25,505 26,418 27,805 27,518 26,867 26,101 26,022 

Total 102,142 105,707 111,055 111,582 109,491 107,128 107,375 

Particulate Matter less than 2.5 (PM2.5) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 0.63 0.55 0.39 0.31 0.24 0.21 0.19

Dallas 2.39 1.98 1.37 1.04 0.78 0.65 0.59

Denton 0.62 0.53 0.35 0.28 0.21 0.17 0.16

Ellis 0.43 0.37 0.26 0.20 0.14 0.12 0.11

Johnson 0.23 0.20 0.14 0.11 0.08 0.07 0.06

Kaufman 0.32 0.27 0.19 0.15 0.11 0.09 0.08

Parker 0.30 0.26 0.18 0.14 0.10 0.08 0.08

Rockwall 0.10 0.08 0.06 0.04 0.03 0.03 0.02

Tarrant 1.46 1.24 0.88 0.68 0.52 0.44 0.40

Total 6.48 5.48 3.83 2.94 2.22 1.85 1.68
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 39

Exhibit 5.2: Final Emission Estimates by County (continued)

Particulate Matter less than 10 (PM10) (tons/day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 0.69 0.60 0.43 0.34 0.27 0.23 0.21

Dallas 2.62 2.17 1.51 1.15 0.87 0.72 0.65

Denton 0.68 0.58 0.39 0.31 0.23 0.19 0.18

Ellis 0.47 0.40 0.28 0.22 0.16 0.13 0.12

Johnson 0.25 0.22 0.15 0.12 0.09 0.07 0.07

Kaufman 0.34 0.30 0.21 0.16 0.12 0.10 0.09

Parker 0.33 0.28 0.20 0.15 0.11 0.09 0.08

Rockwall 0.11 0.09 0.06 0.05 0.03 0.03 0.03

Tarrant 1.61 1.36 0.97 0.75 0.58 0.49 0.45

Total 7.10 6.01 4.21 3.24 2.46 2.06 1.87
ONE-HOUR OZONE AND 1997 8-HOUR OZONE REDESIGNATION SUBSTITUTE 40

CHAPTER 6: LIST OF APPENDICES

Appendix A: MOVES2014 External Files 

Appendix B: MOVES2014 Inputs and Outputs 

Appendix C: MOVES2014 Emission Factors 

Appendix D: Tab Summary Files 

Appendix E: Emission, VMT, and Speed Estimates 

Appendix F: XML 

Appendix G: Redesignation Substitute Emission Inventory Summary Tables 

Appendix H: Project Quality Control Report