Errata 

Date: May 18, 2017 

Issuing Office: Federal Highway Administration—Office of Research, 

Development, and Technology: Infrastructure R&D 

Address: Turner-Fairbank Highway Research Center, 6300 Georgetown 

Pike, McLean, VA 22101 

Name of Document: The Long-Term Pavement Performance Program 

FHWA Publication No.: FHWA-HRT-15-049 

The following change was made to the document after publication on the Federal Highway 

Administration website: 

Location Incorrect Values Corrected Values 

Page 300, Index Scott, Ted M., II, 257, 260 Scott, Ted M., II, 259, 262
Publication No. FHWA-HRT-15-049

HRDI-30/04-15(700)E

Cover image: © MaxyM/Shutterstock.com
THE LONG-TERM PAVEMENT 

PERFORMANCE PROGRAM

Federal Highway Administration

Washington, DC • September 2015
ii    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for 

the use of the information contained in this document. This report does not constitute a 

standard, specification, or regulation. The U.S. Government does not endorse products or 

manufacturers. Trademarks or manufacturers’ names appear in this report only because they 

are considered essential to the objective of the document. 

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs 

and processes to ensure continuous quality improvement. 
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    iii

Table of Contents

Foreword xv

Acknowledgments xvii

Welcome to LTPP xix

PART I. BUILDING AND MANAGING THE LTPP PROGRAM 

Chapter 1.Origins

Introduction 1

The Need To Understand Pavement Performance 2

Long-Term Pavement Monitoring Idea 3

Long-Term Pavement Monitoring Study 3

Strategic Transportation Research Study 4

FHWA Maintains Monitoring Momentum Until SHRP-LTPP Begins 5

Objectives of the SHRP Technical Areas 5

Pavement Condition Monitoring Methods and Equipment Study 6

Early Coordination Activities 7

Long-Term Pavement Performance Goal and Objectives 7

Summary 8

References 9

Chapter 2 Managem

Introduction 11

Under the Strategic Highway Research Program (1987–92) 12

Technical Assistance Contractor Responsibilities 15

Loaned Staff Program 15

Regional Coordination Office Contractor Responsibilities 16

Other Contractor Responsibilities 17

Expert Peer Review Groups 17
iv    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

During the SHRP-to-FHWA Management Transition (1991–92) 18

Under the Federal Highway Administration (1992–Present) 19

Technical Assistance Contractor Responsibilities 20 

Transition of LTPP Program From SHRP to FHWA 20

Regional Support Contractor Responsibilities 23

Other Contractor Responsibilities 24

Expert Peer Review Groups 25

Communication, Coordination, and Outreach 26

Communication With Stakeholders 27

Highway Agency Coordinators’ Meetings 28

Communication Within the Program 29 

Communicating With LTPP Stakeholders via the Web 29

Summary 30

References 31

Leaders of the LTPP Program 32

CHAPTER 3. LTPP PROGRAM PARTNERSHIPS 35

Introduction 35

American Association of State Highway and Transportation Officials 37

Canadian Strategic Highway Research Program 37

State and Provincial Highway Agencies 39

National Research Council/Transportation Research Board 40

Federal Highway Administration 41

Industry, Academia, Professional Associations, and User Organizations 41

International Community 42

International Participation 42

Summary 43

References 43

CHAPTER 4. FEDERAL INVESTMENT IN THE LTPP PROGRAM 45

LTPP Under Five Highway Legislations 45

Funding Variations 45

Surface Transportation and Uniform Relocation Assistance Act 48

Intermodal Surface Transportation Efficiency Act of 1991 50

Transportation Equity Act for the 21st Century 51

Program Adjustments Due to Funding Constraints Under TEA-21 52

Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users 53

Program Adjustments Due to Funding Constraints Under SAFETEA-LU 54

Moving Ahead for Progress in the 21st Century Act 56

Summary 58

References 59

PART II. DEVELOPING THE STUDIES AND THE PAVEMENT 

PERFORMANCE DATABASE

CHAPTER 5. DESIGN AND RECRUITMENT OF THE LTPP EXPERIMENTS 63

Introduction 63

Design of GPS Experiments 64

General Design Criteria 65

Evolution of the GPS Experiments 66
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM  v

Recruitment and Selection of GPS Test Sections 68

Design of SPS Experiments 69

Evolution of the SPS Experiments 70

Supplemental SPS Test Sections 72

Agencies’ Use of Supplemental SPS Test Sections 72

Recruitment and Selection of SPS Test Sections 72

LTPP Experiments and Test Section Locations 74

Summary 74

References 75

Chapter 6 Collect

Introduction 77

Who Collects the Data? 78

What Types of Data Are Collected? 79

Automated Weather Station Data 80

AWS Maintenance Issues 81

AWS Quality Control Programs 81

Decision to Decommission AWS 82

Climate Data—Virtual Weather Stations 82

Dynamic Load Response Data 83

Ground Penetrating Radar Data 83

Inventory Data 84

Structural Data 84

Location Data 85

Maintenance and Rehabilitation Data 85

Maintenance Data 85

Rehabilitation Data 86

Materials Data 87

Materials Sampling and Storage 88

Monitoring Data 89

Deflection Data 89

Distress Data 93

Drainage Data 98

Friction Data 99

Longitudinal Profile Data 99

Rutting Data 102

Transverse Profile Data 103

Seasonal Monitoring Program Data 105

Specific Pavement Studies Inventory Data 105

Traffic Data 106

Historical and Monitored Data 106

Data Collection Equipment 107

Equipment Calibration 107

Summary 108

References 109

Chaptr 7. Special LTPP

Introduction 115

Seasonal Monitoring Program Data 115

Scope 117
vi    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Monitoring Equipment 117

Validation of Data Collection Procedures 117

Data Collected and Monitoring Frequency 119

SMP Phase I Monitoring 119

SMP Phase II Monitoring 119

Quality Control Software 120

Training and Data Interpretation 120

LTPP SPS Traffic Data Collection Pooled-Fund Study 121

Pilot Studies Conducted to Test Protocols 122

Traffic Pooled-Fund Study Process 123

Products of the Study 124

Materials Action Plan 124

Forensic Studies 126

Summary 127

References 128

Chapter 8. Storge,

ofthe LTPP 

Introduction 131

Development of the LTPP Information Management System 133

SHRP-LTPP Database Process (1989 to 1994) 133

FHWA-LTPP Database Process (1995 to 1999) 135

FHWA-LTPP Database Process (2000 to 2011) 136

FHWA-LTPP Database Process (2011 to Present) 139

History of LTPP Information Management System Hardware and Software 141

IMS Hardware 141

IMS Software 141

Data Storage 144

Pavement Performance Database 144

Ancillary Information Management System 147

Growth in LTPP Data 148

Falling Weight Deflectometer Data 148

Longitudinal Profile Data 149

Pavement Distress Data 149

Transverse Profile Data 150

Climate Data 150

Materials Sampling and Test Data 150

Data Dissemination 151

LTPP Data Release History 153

LTPP Data Dissemination Tools 154

LTPP Customer Support Service Center 155

LTPP Library 156

Data Security 157

Safeguards for the LTPP Information Management System 157

Hardware Security and Data Backup Procedures 158

Summary 159

References 159
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    vii

Chapter 9. LTPP Data Qu

Introduction 163

Quality Control Processes Before Data Collection 164

Data Collection Standards 164

Personnel Requirements 167

Equipment Requirements 168

Daily Checks of Inertial Profilers 169

Quality Control Processes During Data Collection 170

Ambient Conditions 170

Monitoring and Reviewing Data Collection in the Field 171

Quality Control Tools to Check Equipment and Data 172

Quality Control Processes After Data Collection 173

Migration to LTAS: Example of LTPP-Developed Quality Control Software 174

Database Checks and Reviews 175

LTPP Quality Assurance Efforts 177

LTPP Quality Assurance Audits 177

Regional Quality Control and Data Flow Management Plans 178

Higher Order Data Checks 178

Time-Series Checks 179

Data Studies 179

Data Analyses 180

Peer Review 181

Feedback Processes 182

Operational Problem Reports 182

Data Analysis/Operations Feedback Reports 182

Software Performance Reports 182

 Conformance With Data Quality Systems and Standards 183

Summary 183

References 184

PART III. CREATING PRODUCTS, LEARNING FROM THE PAST, AND PREPARING FOR THE F

Chapter 10. Turning LTPP

Introduction 189

LTPP Data Analysis 189

Early Analyses 190

Strategic Plan for LTPP Data Analysis: The “Tablecloth” 191

LTPP Data Studies 199

Highway Agency Studies 199

The Mechanistic-Empirical Pavement Design Guide 203

TRB LTPP Data Analysis Working Group 203

International Data Analysis Contest 204

Translating Analysis Results Into Products 204

LTPP Products 204

Development of the LTPP Product Plan 204

LTPP Leverages FHWA’s Transportation Pooled-Fund Program 207

National Pavement Need 1: New and Reconstructed Pavements 207

National Pavement Need 2: Maintenance and Rehabilitation of 

 Pavements 209
viii    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

National Pavement Need 3: Pavement Management System Tools 

 and Techniques 210

National Pavement Need 4: Traffic Loading and Environmental Effects 212

National Pavement Need 5: National Pavement Performance Data Services 215

LTPP Benefits and Broader Impact 216

Key Findings From the LTPP Program 216

The Benefits Study 216

LTPP QC/QA Resources 218

LTPP Contributions to Other Federal Efforts 219

Summary 220

References 220

Chapter 11. Lesons L

Introduction 229

Question All Assumptions 229

Test Site Information Assumptions 230

Traffic Data Assumptions 230

Establish Clear Product Development Expectations 231

Manage From the Center to Succeed 231

Dedicated Funding 231

Dedicated LTPP Program Staff 232

LTPP Norms 233

Dedicated Highway Agency Staff 234

Reassess Periodically 234

SHRP Midcourse Assessment Meeting 234

States Convey Their Needs to LTPP 235

LTPP National Meeting 235

LTPP Program Focus: Assessment and Corrective Actions 236

LTPP SPS Workshop 238

Keep Partners Informed 239

Document Continually 240

Prepare to Change With Technology 240

Summary 240

References 241

Chapter 1. vin

Introduction 243

Securing and Enhancing LTPP Resources 245

LTPP Resources for Data Users 245

Providing Security and Maintenance 246

Improving the Database 246

Supporting LTPP Data Users 247

Collecting Pavement Performance Data 247

Completing the Original LTPP Experiments 248

Conducting Forensic Studies 249

Implementing New LTPP Experiments 249

Conducting Analyses and Developing Products 250

New Insights and Understanding Through LTPP Data Analysis 250

New Tools and Resources for Pavement Researchers, Practitioners, and Managers 251
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    ix

Potential Future Insights and Benefits 251

Contributing to National Initiatives 252

LTPP and a Future of Opportunity 252

References 253

FHWA-LTPP TEAM 255

APPENDIX A. PLANNING AND ADVISORY COMMITTEES SUPPORTING 

THE LTPP PROGRAM 257

APPENDIX B. CONTRACT SERVICES ACQUIRED TO OPERATE THE LTPP PROGRAM 269

APPENDIX C. DATA COLLECTION EQUIPMENT, INSTRUMENTATION, AND

SOFTWARE USED IN THE LTPP PROGRAM 277

INDEX 287

ACRONYMS 305

LIST OF FIGURES

1.1. Report of the Strategic Transportation Research Study. 4

1.2. The 1986 Strategic Highway Research Program Research Plans. 6

2.1. The four LTPP regions and current regional offices. 13 

2.2. Structure of the LTPP organization during the SHRP-LTPP years (1987–92). 14 

2.3. SHRP-LTPP and FHWA-LTPP staff members during the LTPP program transition. 19

2.4. LTPP within the FHWA Turner-Fairbank Highway Research Center organizational 

structure (2012). 21 

2.5. General structure of the LTPP organization during the FHWA-LTPP years 

(1992–present). 22 

2.6. LTPP Committee meeting held in Washington, DC, on October 29, 2013. 26 

2.7. Connecticut Department of Transportation (CT DOT) staff meet with the LTPP program 

and regional support contractor staff. 27 

2.8. LTPP program staff and core contractors meet to discuss the status of different program 

activities. 30 

3.1. Memorandum of Understanding for the recruitment of LTPP SPS test sections. 38 

3.2. Reports of the winning papers from the 2001–2002 and 2003–2004 international data 

analysis contests. 41

4.1. LTPP funding in fiscal years 1987–2014. 48

5.1. Example of the research matrices used to plan the General Pavement Study experiments. 66

5.2. Designated layout for GPS test sites. 69

5.3. Sampling template and cell identification numbers for GPS-1 (Asphalt Concrete on 

Granular Base). 69

5.4. Example of the research design matrices created for the Specific Pavement Study experiments. 70

5.5. Test section layout for SPS-1 and SPS-2 projects (Strategic Studies of Structural Factors for 

Flexible and Rigid Pavements, respectively). 73

5.6. Locations of the 2,509 pavement test sections across the United States, Puerto Rico, and 

Canada. 74

6.1. LTPP data collection categories. 79
x    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

6.2. Complete automated weather station installation with protective fencing. 80 

6.3. Prototype automated weather station used by the LTPP regional support contractors for 

in-house training of staff and to calibrate equipment components. 81 

6.4. A virtual weather station (VWS). 82 

6.5. Van-towed falling weight deflectometer equipment used in the LTPP program. 90

6.6. Falling weight deflectometer equipment at the first LTPP “thump-off.” 90

6.7. The cover of the FWD maintenance manual, used to keep the units operating at peak 

performance. 91

6.8. An FWD being calibrated at the PennDOT regional calibration center early in the LTPP 

program. 92

6.9. Mobile equipment used to photograph pavement distress. 94 

6.10. Sample of a computer-generated distress map from PADIAS 4.2 software. 94 

6.11. Film Motion Analyzer. 95

6.12. Example of the multipage forms used to record distresses observed during LTPP manual 

distress surveys. 96 

6.13. Participants in a field review of distresses at an LTPP distress accreditation workshop. 97 

6.14. Screen shot from DiVA software showing a time-series chart of a pavement distress 

along with the table for all distresses for a test section. 98

6.15. Edge drain inspection using videography. 98

6.16. Locked-wheel skid tester currently in use for collecting friction data. 99 

6.17. The first (DNC 690) Profilometers used in the LTPP program. 99 

6.18. The T6600 Profilometer, in use from 1996 to 2002. 100 

6.19. ICC Profiler MDR 4086L3 (Ford E350 van), in use from 2002 to 2013. 100 

6.20. Ames Profiler in Ford E150 van, acquired in 2013. 100

6.21. Manual Face® Dipstick® used to collect profile data in the LTPP program. 101

6.22. Profile coordinators with four ICC profilers and the last K. J. Law Profilometer,

gathered for a rodeo at MnROAD in 2007. 101

6.23. Profile coordinators gather in College Station, TX, in 2013 to receive training from the 

LTPP program on the new Ames profiler units. 101 

6.24. Measuring rut depth with the 4-ft straightedge. 102 

6.25. Diagrams of the PASCO/CGH ROADRECON-75 showing (a) the transverse surface profiler 

system mounted in a vehicle; and (b) the geometric relations between the system’s optical 

bar and camera. 103 

6.26. Translating photographs produced by the automatic profilers into digital format. 103 

6.27. Normalization of transverse profiler measurements to lane edges. 104 

6.28. Three Face® Dipstick® profile measuring devices with carrying cases. 105 

6.29. A sample data transmittal form used by the highway agency to submit historical traffic data 

to the LTPP regional support contractor. 106 

6.30. A sample data transmittal form used by the highway agency to submit traffic estimates to 

the LTPP regional support contractor. 108 

7.1. Distribution of instrumented sites in the LTPP Seasonal Monitoring Program. 116

7.2. A piezometer monitoring well and cap, used to determine ground water levels. 117

7.3. Mobile monitoring equipment for downloading data collected at seasonal monitoring

sites. 117

7.4. The moisture probe designed at the FHWA highway research center. 118
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xi

7.5. Schematic of the moisture probe that was used to obtain moisture content in unbound base 

and subgrade materials in the SMP, designed at the FHWA highway research center. 118

7.6. SMP Phase II seasonal monitoring equipment installation at the Lake Ontario State 

Parkway site on SR 947A in western New York. 120

7.7. Traffic ETG members who provided technical guidance and direction to the traffic 

pooled-fund study. 122 

7.8. Participating States in the LTPP SPS Traffic Data Collection Pooled-Fund Study. 123 

7.9. Load cell WIM installation. 124

7.10. Staggered bending plate WIM sensors installed in concrete pavement. 124

7.11. Installation of quartz piezoelectric WIM sensor spanning a full lane. 124

7.12. Screen shot from LTPP Traffic Analysis Software showing loadings of Class 9 traffic. 125

7.13. LTPP regional support contractor staff use the dynamic core penetrometer to determine 

the strength and density of the subgrade at the SPS site in Minnesota. 126

7.14. Workers prepare a trench for forensic investigation of an SPS-5 site in Arizona. 127

8.1. The LTPP Information Management System. 133

8.2. Overview of the initial SHRP-LTPP database process, data flow, and releases circa 1989 

to 1994. 134

8.3. Functional diagram of LTPP data processing flow circa 1995 to 1999. 136

8.4. Functional diagram of LTPP data processing flow circa 2000 to 2011. 138

8.5. Functional diagram of LTPP data processing flow circa 2011 to present. 140

8.6. DEC MicroVAX 3900 computer running the UNIX® operating system, used as the first 

LTPP National Information Management System (NIMS) server from 1989 to 1993. 143

8.7. The LTPP DEC Alpha 3000 AXP 400 S computer system running the UNIX® operating 

system, used for NIMs server functions from 1993 to 1997. 143

8.8. Compaq® ProLiant 1500 server running Windows® NT 16-bit operating system, used for the 

central database server 1997 to 2001. 143

8.9. DellTM PowerEdgeTM 2900III installed in May 2009 at FHWA’s Turner-Fairbank Highway 

Research Center to serve as the secure central repository for LTPP electronic data into 

the future. 143

8.10. Historical changes in the number of FWD data sets contained in LTPP data releases. 148

8.11. Growth in number of FWD basin and load transfer measurements contained in the LTPP 

database since 2002. 148

8.12. Growth in number of longitudinal pavement profile measurements. 149

8.13. History of LTPP pavement surface distress surveys. 149 

8.14. Increase in transverse profile measurements since 1996. 150

8.15. Growth in number of hourly climate data measurements collected by the LTPP program as 

part of the Seasonal Monitoring Program and automated weather station data collection 

efforts. 150

8.16. Increase in total number of records in the materials test module starting in 1996. 151

8.17. Growth in materials data for resilient modulus (Mr

), creep compliance, and indirect tensile 

strength (IDT) using the P07 version 2 test protocol. 151 

8.18. Home page of the LTPP InfoPaveTM Web site. 155

8.19. LTPP InfoPave’s interactive map feature, showing the locations of LTPP test sections. 156

9.1. Data collection guidelines published as manuals for profile measurements and processing, 

distress identification, and falling weight deflectometer measurements. 165
xii    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

9.2. Distress raters evaluate a pavement surface in an LTPP accreditation workshop. 167

9.3. Profiler rodeo held at the Minnesota Road Research Project (MnROAD) site in 

Albertville. 170

9.4. ProQual software, used to evaluate the acceptability of profile data. 172

9.5. The Traffic Monitoring Guide. 175

9.6. A distress-versus-time graph produced by the DiVA software. 179

9.7. LTPP Data Analysis/Operations Feedback Report, used to provide feedback to the program 

regarding data that require investigation or correction. 183

10.1. Introduction to the original LTPP Strategic Plan for Long-Term Pavement Performance 

Data Analysis, page 1, as adopted in 1999. 193

10.2. Graphical compilation of the 1999 LTPP Strategic Plan for Long-Term Pavement Performance Data Analysis, its strategic objectives and product priorities. 194

10.3. Illustration of the expanded strategic plan for LTPP data analysis, showing the extent and 

complexity of the plan as it has evolved since 1999. 195

10.4. Excerpt of the expanded strategic plan for LTPP data analysis, showing analysis outcomes, 

supporting projects, and problem statements for Strategic Objective 1: Traffic Characterization and Prediction. 196

10.5. Excerpt of the expanded strategic plan for LTPP data analysis, showing analysis outcomes, 

supporting projects, and problem statements for Strategic Objective 6: Maintenance and 

Rehabilitation Strategy Selection and Performance Prediction. 197

10.6. MnROAD low-volume road and mainline test roadways owned and operated by the 

Minnesota Department of Transportation. 201

10.7. Daniel Franta, a graduate student at the University of Minnesota, receives the 2012 

ASCE-LTPP Data Analysis Contest Winner award. 204 

10.8. LTPP Product table from the 2001 LTPP Product Plan showing how existing and planned 

LTPP products address national pavement needs. 206

10.9. LTPP Dynamic Modulus Prediction software, available from the LTPP program. 209

10.10. Distress Identification Guide, Asphalt Concrete Pavements. 211

10.11. Participating States in the LTPP SPS Traffic Data Collection Pooled-Fund Study. 213

LIST OF TABLES

1.1. LTPP General and Specific Pavement Study experiments. 8

4.1. LTPP program Federal funding (fiscal years 1987–2014). 46

4.2. LTPP Timeline—Highway legislated and other funding sources. 47

4.3. LTPP program funding under STURAA (fiscal years 1987–91). 49

4.4. LTPP program funding under ISTEA (fiscal years 1992–97). 50

4.5. LTPP program funding under TEA-21 (fiscal years 1998–2003). 52

4.6. LTPP program funding under SAFETEA-LU (fiscal years 2004–2009). 54

4.7. LTPP program funding under MAP-21 (fiscal years 2010–2014). 57

5.1. Evolution of the General Pavement Study experiment designs. 67

5.2. Evolution of the Specific Pavement Study experiment designs. 71

5.3. LTPP General and Specific Pavement Study experiments. 74
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xiii

6.1. LTPP database modules (circa 2014). 79

7.1. LTPP WIM system performance requirements. 122

8.1. IMS computer hardware used in the LTPP program. 142

8.2. Contents of the Ancillary Information Management System. 147

8.3. Nominal dates for major LTPP data releases. 152

8.4. Backup frequency for the LTPP Information Management System, 2014. 158

9.1. LTPP data collection guidelines. 166

9.2. LTPP data collection equipment and components. 168

10.1. LTPP data analysis research funded by the National Cooperative Highway 

Research Program. 198

10.2. Status of research studies related to the Strategic Plan for LTPP Data Analysis 

(1999-2014). 199

12.1. Importance of completing the long-term monitoring of the original LTPP experiments. 248
xiv    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

© Comstock
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xv

Why read this report? For highway professionals the 

answer is obvious. This report is a treasure trove of 

information about pavements and their performance. 

But why should others read it? Because the report 

details how a long-term, strategically oriented research 

program was conceived, initiated, and successfully carried out. In the 1980s such research had disappeared 

from the transportation field, displaced by short-term 

efforts aimed at narrowly focused problem solving or 

policy adjustments. Such research is needed of course, 

but it cannot answer fundamental questions about the 

performance of transportation infrastructure—the 

very questions that the “infrastructure crisis” of the 

1980s brought to the fore. Such questions require wellorganized, interconnected programs of research such 

as the Long-Term Pavement Performance program, 

better known as LTPP.

To understand LTPP, one must first understand the 

discontent and frustration among transportation agencies during the latter part of the 1970s and 1980s. Public works of all kinds seemed to be falling into disrepair 

at an alarming rate. The popular press dubbed it “the 

Infrastructure Crisis.” Roadways, especially roadway 

pavements, seemed to be most prominently afflicted. 

Highway pavements, whether on country lanes or 

modern expressways, were simply not living up to the 

expectations of motorists and freight carriers. Nor 

were they living up to the expectations of the transportation agencies. No one was quite sure why this crisis 

arose or how it might be overcome. What was certain 

was that investments in highway research had fallen to 

a historic low. In the late 1970s, the U.S. Congress began 

to focus on the infrastructure crisis and the role of 

research in providing solutions. The key legislative 

action was the passage of the Surface Transportation 

and Uniform Relocation Assistance Act in 1987. This 

act significantly increased funds available for highway 

research and specifically funded a Strategic Highway 

Research Program (SHRP) previously recommended 

by a select committee of the Transportation Research 

Board. A key element of SHRP was the studies of the 

LTPP program. These studies were explicitly designed 

to address concerns about the long-term behavior of 

highway pavements and how that behavior was influenced by climate, materials properties, traffic, design, 

construction, and maintenance. 

The pages that follow recount the history and outcomes to date of the LTPP program. The program’s 

Foreword
xvi    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

studies have tracked the performance of more than 

2,500 pavement test sections located throughout the 

United States and Canada, in some cases for more than 

20 years. What might not be evident in this history is 

how daunting a task it all seemed at the beginning, considering what was expected of the program.

LTPP was intended to be the largest pavement 

research effort ever—transcontinental in its scope. It 

was expected to involve the active collaboration of the 

transportation agencies of the 50 American States, 

Puerto Rico, the District of Columbia, and, ultimately, 

all 10 Canadian Provinces. The individual test sites 

would be widely dispersed, and the research teams 

would have to be masters of logistics. One part of LTPP 

would study the past and future performance of inservice test sections typical of pavements in current 

use. The second part of the effort would study specially constructed pavements where factors deemed 

important to pavement performance could be carefully controlled. 

LTPP was expected to be truly “long term,” lasting 

at least 20 years. This expected longevity also posed a 

host of concerns about funding, continuity of the 

research, materials sample storage, data storage and 

access, and the like. Most of all, it required long-range 

research and management plans. 

The studies were to be comprehensive, considering 

how variations in climate, materials, designs, maintenance activities, and other factors augment or limit 

pavement life. Also, a host of practical outcomes were 

expected, including new, more reliable pavement 

design procedures and standards, cost allocation methodologies, improved pavement management techniques, and pavement maintenance policies.

These grand goals, grand expectations, and grand 

plans were seen as too grand by skeptics. They held 

that LTPP would wither before the studies were completed and would not meet the grand goals. Turn now 

to The Long-Term Pavement Performance Program and 

judge for yourself.

Neil F. Hawks

SHRP-LTPP Director, 1987–1992
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xvii

A great deal of gratitude is owed those who gathered 

in the 1980s to not only discuss the condition of the 

Nation’s highway system but to also articulate a vision for 

its improvement and to develop a plan to make the vision 

a reality. Thus, the Long-Term Pavement Performance 

(LTPP) program came to be.

Thank you to the many authors of this history for taking time to record the facts about the program’s development so that future generations can have a good 

understanding of how the LTPP program began, has 

been managed, and has overcome the many challenges 

inherent in a long-term pavement monitoring effort. Staff 

members of the National Academy of Sciences’ Transportation Research Board (TRB) who work with the program are due thanks for helping to sustain the LTPP 

vision through the many changes in volunteer and staff 

participation over the years. The Federal Highway 

Administration’s Division Offices are also recognized for 

their role in maintaining communications between the 

LTPP program office and the highway agencies.

Acknowledgement is given to the many efforts and 

contributions of the LTPP program staff, its contractor 

staff, and the supporting TRB LTPP committees who 

have devoted countless hours to review the contents of 

this book for accuracy and completeness, and for 

providing the pictures displayed throughout the pages.

Leading the effort to assemble this book has been both 

a challenge and pleasure over the past several years. The 

primary goal for this document is to provide a detailed, 

written record of the LTPP program that serves the 

needs of different readers—from the chief engineer in the 

highway agency who wants a better understanding of the 

origins of the program (chapter 1) to the pavement engineer who wants to learn more about the different LTPP 

products (chapter 10) to the student who needs to know 

the different types of pavement performance data 

collected by the program (chapter 6). Thank you to 

management for the privilege of working on this assignment. Thank you to those who offered encouragement 

on those challenging days, but sincerest gratitude goes to 

the communications director who worked diligently to 

help resolve the big issues and tiniest details to complete 

this book. Read on, to learn about the LTPP program’s 

rich history and its future direction.

 

Deborah Walker

Research Civil Engineer, LTPP Team Member

Federal Highway Administration

Acknowledgments
The Long-Term Pavement Performance program partners, data elements, and data collection, storage, and analysis activities. 

(Concept by Eric Weaver, Federal Highway Administration; executed by Jim Elmore, CSI.)
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xix

The mission to study pavement performance systematically across the United States and to promote extended 

pavement life had been advanced since the late 1950s 

by the National Academy of Sciences’ Transportation 

Research Board, the American Association of State 

Highway and Transportation Officials, and the U.S. 

Department of Transportation’s Federal Highway 

Administration (FHWA). By the 1970s, deterioration of 

the highway systems built two and three decades earlier was a growing concern, and highway budgets were 

increasingly devoted to maintenance, rehabilitation, 

and reconstruction. By the 1980s, the bill coming due 

for pavement repair and replacement by the year 2000 

was estimated at $400 billion.1,2 Highway agencies 

were creating pavement management programs to help 

them invest public funds more strategically, but lacked 

historical data to support those programs. Although 

many highway agencies were conducting pavement 

research, a broader, long-term, coordinated effort was 

needed to understand better how to design, build, and 

maintain long-lasting, high-performing pavements. 

Congress, in the Surface Transportation Assistance 

Act of 1978, directed the Secretary of Transportation, 

assisted by the Congressional Budget Office, to “invesWelcome to LTPP

tigate . . . the need for long-term or continuous monitoring of roadway deterioration to determine the 

relative damage attributable to traffic and environmental factors.”3

 The Congressional Budget Office responded with Guidelines that outlined the effort needed:

Many of the uncertainties about pavement...can be unequivocally resolved only by carefully monitoring the 

volume and mix of traffic on selected roads over an extended period and by monitoring changes in the serviceability of the pavement over the same period. . . . This 

undertaking would also produce information that could 

improve practices followed in the construction and 

maintenance of pavement. The selection of the roads to 

be monitored should be made in such a way that the 

study will include a representative set of climatic and environmental conditions. In addition, it is important that 

a wide range of road types be monitored, including roads 

on every functional system and both urban and rural 

roads. To the greatest extent possible, wide variations in 

the mix of traffic should be sought at otherwise similar 

monitoring points, so that additional assessment of the 

relative effects of heavy and light vehicles can be made.4

Nearly a decade later, with passage of the Surface 

Transportation and Uniform Relocation Assistance Act 
xx    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

of 1987, Congress authorized the Long-Term Pavement 

Performance (LTPP) program as part of the first Strategic Highway Research Program (SHRP), a 5-year applied 

research program funded by the 50 States through a dedicated share of the Highway Trust Fund.5 The program 

was joined by Canada, whose leaders were also seeking 

to advance highway research and were closely involved 

in planning for SHRP. Canada’s 10 Provincial highway 

agencies participated in SHRP and the LTPP program. 

The mission of the LTPP program was ambitious: 

• Collect and store performance data from a large 

number of in-service highways over an extended period to support analysis and product development. 

• Analyze these data to describe how pavements perform and explain why they perform as they do. 

• Translate these insights into knowledge and usable 

engineering products related to pavement design, 

construction, rehabilitation, maintenance, preservation, and management.

After extensive planning, data collection officially 

began in 1989. Four LTPP regional offices and a small 

national office were established to coordinate the collection of data within 17 scientifically designed experiments. Eventually, 2,509 pavement test sections on 

in-service highways were selected or constructed to 

address specific questions about how differently constructed and maintained pavements perform under the 

wide range of climatic, soil, and traffic conditions in 

the United States and Canada. Such an ambitious program required identifying the constituent materials 

and structural design of each test section and its maintenance history, monitoring weather conditions, determining traffic loads and volumes, and monitoring the 

resultant pavement performance. This vast store of 

information had to be carefully collected and safeguarded for future analysis.

At the end of SHRP in 1992, the LTPP program continued under the leadership of FHWA, and continues today, 

with the participation of highway agencies in all 50 States 

and 10 Canadian Provinces as well as the District of 

Columbia and Puerto Rico. Pavement test sections are 

monitored until they reach the end of their design life or 

are otherwise recommended to be taken out of study by 

the participating highway agency. By following these test 

sections over time, researchers are gaining insight into 

how and why pavements perform as they do, which provides valuable lessons on how to build and maintain longer lasting, more cost-effective pavements. 

New experiments are being added to monitor the 

performance of pavement materials and technologies 

that were not yet in use when the LTPP program began, 

such as warm-mix asphalt and pavement preservation. 

As highway agencies implement other pavement materials and technologies, the LTPP program will consider 

whether they should be added to the program for longterm monitoring.

 The LTPP program has generated a broad array of 

benefits across the pavement engineering and performance spectrum. Numerous applications now make 

use of LTPP data, and the utility of the data is increasing. LTPP benefits and products fit broadly within 

three categories:

• The largest and most comprehensive pavement 

performance database (approximately 280 million 

records of data and climbing) in the world.

• Advances in pavement performance measurement.

• Contributions to pavement design and management.

Because of the foresight of leaders in the highway 

community three decades ago and the resolve of all parties involved in the program, LTPP-related findings continue to benefit the highway community and ultimately 

the taxpayers and driving public. In some cases, highway 

agencies have seen cost-savings in the millions of dollars 

on their highway systems as a result of these findings. 

To make the best use of the LTPP data, some understanding of the history of the program and the decisions that shaped it is needed. Many people and 

The goal of the Long-Term Pavement Performance 

program is to increase pavement life by investigation of various designs of pavement structures and 

rehabilitated pavement structures, using different 

materials and under different loads, environments, 

subgrade soil, and maintenance practices.
organizations have participated in this extraordinary 

data collection, analysis, and product development 

effort. Program decisions have evolved over time to 

implement what has been learned and to adopt advances 

in technology. This report was prepared to document 

the history of the LTPP program as a foundation for 

future work, to review lessons learned, and to consider 

how future pavement managers, researchers, and engineers can benefit further from the program. The report 

is organized in three parts: 

I. Building and Managing the LTPP Program

Chapter 1. Origins of the LTPP Program—the program’s conception, pre-implementation studies, 

and early development.

Chapter 2. Management of the LTPP Program—the 

program’s organizational structure, peer review and 

advisory functions, and communication and coordination activities, and an introduction to the program’s managers. 

Chapter 3. LTPP Program Partnerships—the major 

collaborators in the program and their contributions.

Chapter 4. Federal Investment in the LTPP Program

—the U.S. Federal legislative mandates for the program, its budgetary support, and the impact of funding reductions on program activities.

II.Developing the Studies and the Pavement 

Performance Database

Chapter 5. Design and Recruitment of the LTPP 

Experiments—the planning process that determined 

what variables would be studied at the test sites that 

were to be chosen for the General Pavement Studies 

and constructed for the Specific Pavement Studies.

Chapter 6. Collection of the LTPP Data—datagathering efforts, technologies, and procedures. 

The LTPP program continues to improve its data 

collection and quality control procedures through 

lessons learned and by adapting to changes in 

equipment and pavement technology. Although 

data collection and quality control procedures 

have varied over time, the principal data types 

collected since the beginning of the program, 

shown in the graphic above, have not. The program has collected these data in a consistent and 

systematic manner over the years, and they will 

be the primary source for evaluating pavement 

performance for the foreseeable future.6

Types of Data Collected AT 

Climate

Response

Load

Structure

Distress

Materials

THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xxi
xxii  THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Chapter 7. Special LTPP Data Collection Efforts—

data collected through special programs that were 

not in the original experiment designs—the Seasonal Monitoring Program, Traffic Data Collection 

Pooled-Fund Study, Materials Action Plan, and 

forensic studies.

Chapter 8. Storage, Growth, Security, and Dissemination of the LTPP Data—history of the data storage 

and distribution technologies and procedures. 

Chapter 9. LTPP Data Quality Efforts—manual and 

automated quality control and assurance processes 

established to ensure that the data stored are of 

research quality. 

III. Creating Products, Learning From the Past, and

Preparing for the Future

Chapter 10. Turning LTPP Data Into Results—data

analysis activities, LTPP products, research findings, and realized economic and performance

benefits.

Chapter 11. Lessons Learned From the LTPP Program—lessons learned from some of the thornier

problems that the program wrestled with, their

outcomes, and insights gained.

Chapter 12. Paving the Way to the Future—preservation, refinement, and analysis activities required of

the program to maximize the LTPP investment, and 

plans for monitoring the performance of new pavement materials and technologies.

Three appendices outline the program’s advisory 

bodies, technical contracts, and data collection equipment and software.

References are provided throughout this history, 

many with links to the World-Wide Web. Over time, 

these links may become obsolete. Readers seeking 

these source documents or more up-to-date information about the program and its future should refer to 

the LTPP home page and the LTPP InfoPaveTM Web site.

REFERENCES

1. America’s Highways: Accelerating the Search for 

Innovation (Special Report 202). Transportation

Research Board, National Research Council, 

Washington, DC, 1984, p. 7. 

2. “Total Disbursements for Highways, by Function 

1945–2000.” Web page. http://www.fhwa.dot.gov/

ohim/hs00/pdf/discht.pdf.

3. U.S. Statutes at Large 92 (1978): 2760. Surface

Transportation Assistance Act of 1978. 

4. Guidelines for A Study of Highway Cost Allocation; As 

Required by Public Law 95-599. Congressional Budget 

Office, Congress of the United States, February 1979, 

p. 36.

5. U.S. Statutes at Large 101 (1987): 132–261. Surface

Transportation and Uniform Relocation Assistance Act 

of 1987.

6. “Long-Term Pavement Performance” (FHWA-HRT15-018; brochure). Federal Highway Administration, 

McLean, VA, January 2015. http://

www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/15018/15018.pdf. 
THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM    xxiii

©Janis Knight, www.homeplanetimages.com

Building and Managing the LTPP Program

I 
xxvi    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP program began with a high level of support from 

the U. S. Congress and from a wide array of organizations that 

were represented in formulating the program.

© apiguide/Shutterstock.com
1: origs of the

Origins of the Ltpp Progr

1

Introduct

The LTPP program is an ongoing effort to collect and 

understand information about how and why pavements 

behave as they do. The program consists of experiments 

that were carefully designed to answer specific questions about how certain variables—pavement design, 

construction, and materials; maintenance and rehabilitation practices; traffic loading; and climate—affect 

pavement performance over time. Pavement test sections are established throughout the United States and 

Canada with the cooperation and support of the State 

and Provincial highway agencies. Some test sections are 

selected from existing highways and others are constructed to the program’s specifications. Information 

on the design, construction methods, materials, and 

The LTPP program officially began in 1987, after much planning and preparation. Its purpose was simple: 

gather high-quality data needed to understand pavement performance—and the variables affecting it—

and make the data available for research and development of high-value products well into the future. 

The execution of this mandate, however, has been exceedingly complex, involving dozens of organizations, 

hundreds of participants, thousands of decisions, and volumes upon volumes of data and analysis. 

Several decades later, the program continues to positively impact the highway community.

maintenance and rehabilitation activities are collected 

for each test section. The program monitors the performance of these sections, their traffic loads and climatic 

conditions, and the data collected are made available to 

the highway community. The LTPP program is the largest and longest lasting pavement monitoring program, 

and it has assembled one of the most comprehensive 

national and international pavement performance databases in the world. 

The LTPP program evolved from long-term pavement monitoring studies that were conducted in the 

early 1980s. Planning for a long-term monitoring program gained momentum as supporters of the concept 

realized the potential return that investment in long-
2    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Key Milestones in the Origins

of L

1978 Surface Transportation Assistanc

Act calls for long-term roadway 

monitoring

1982 FHWA implements the Long-Term 

Pavement Monitoring Study

1984 AASHTO approves recommendations from Strategic Transportatio

Research Stud

1984 Office of SHRP interim director

established

1985 AASHTO Task Force approves

research plans

1985 Contractors chosen for SHRP

research areas

1985 FHWA funds the Pavement 

Condition Monitoring Methods and 

Equipment Study

1986 SHRP research plans publishe

1987 U.S. Congress authorizes

SHRP-LTPP program

the NE

PAVEMEN

At the time SHRP was conceived, the United States 

had reached a low point in highway research investment at the State and Federal levels and in private 

industry. By comparison with other developed countries, other industries, and its own previous levels of 

investment, the country was falling behind in its commitment to highway research.2,3 At the same time, the 

Nation faced an impending crisis in the aging of its 

highway infrastructure, which was due for massive 

investments in repair and replacement. Accountability 

for the use of public funds was becoming a much greater priority for government agencies. Highway expenditures were $50 billion annually at the time,4 and it 

was estimated the Nation would spend $400 billion 

replacing and rehabilitating pavements by the year 

2000.5 People recognized that improved understanding of how pavement design, materials, construction 

techniques, maintenance practices, traffic loads, and 

climate affected the life cycle of pavements would lead 

to longer lasting pavements and a more efficient use of 

public funds. 

The need to improve design methods was pressing. 

Pavement design guides in wide use by highway agencies between the 1960s and 2000s6,7,8 largely relied on 

models of pavement behavior developed primarily from 

the American Association of State Highway Officials 

(AASHO) Road Test,9 conducted in the late 1950s. The 

AASHO Road Test had a very small inference space of 

monitored pavements and loading parameters. By the 

mid-1980s, truck traffic loads far exceeded the levels 

experienced 30 years prior, and the AASHO Road Test 

was no longer applicable to the design of modern pavements. No other long-term, nationwide research had 

been conducted on pavement performance. Despite 

their limitations, in some cases the design models in use 

worked reasonably well, and they were enhanced with 

professional judgment and calibration factors to more 

accurately predict true performance. In other cases, 

however, predictions of design performance varied 

drastically from observed performance, resulting in 

overdesigns and underdesigns that taxed highway 

agency budgets. Legislators demanded better, more 

reliable methods of budgeting available transportation 

term pavement research would ultimately bring. After 

years of preparation, the LTPP program officially 

began as part of the 5-year Strategic Highway Research 

Program (SHRP) authorized by Congress in 1987.1 A 

critical component of the multi-pronged SHRP effort, 

the LTPP program carried an initial price tag of $50 

million over 5 years. The ultimate return on investment would be the economic benefits realized from 

better design, construction, monitoring, and management of the Nation’s pavements—the anticipated outcome of long-term pavement performance monitoring 

and the research it would enable. Before the launch of 

such an ambitious research program, extensive planning and preparation were necessary. 

This chapter focuses on the conception, planning, 

precursor studies, and early coordination activities that 

laid the groundwork and prepared the management 

structure for implementation of the LTPP program.

© mexrix/Shutterstock.com
1: origs of the

dollars, with some assurances that a major failure 

would not occur to derail years of planning. 

A secondary impetus for long-term monitoring of 

pavements in service came from the need for models to 

make pavement management systems more accurate in 

their predictive capabilities. In the mid-1980s, pavement 

management was becoming recognized as a valuable 

tool. Improvements were needed in pavement performance models, and standards for collecting researchquality pavement performance data were lacking.10,11 

Leaders in the highway community called for a 

large-scale, national approach to learning how best to 

design, build, and maintain long-lasting highway infrastructure. Highway managers and engineers at the 

time were convinced that the opportunity to make vast 

improvements in the understanding of pavement 

performance was a prudent fiscal investment. In the 

United States, the Federal Highway Administration 

(FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) strongly 

supported the initiative, and Canada joined in the planning and implementation phases of the program, with 

representation on the SHRP Task Force and on each of 

its seven technical area advisory committees. State and 

Provincial agencies worked together to locate suitable 

test sections for monitoring and helped in numerous 

workshops and meetings to guide the development of 

the program in the mid-1980s. AASHTO, FHWA, and 

the Transportation Research Board (TRB) of the 

National Research Council, together with leaders in 

the international highway community and the pavement industry, began a dialogue about the need to collect pavement performance data over an extended 

period. The remainder of this chapter describes the 

research and planning that led up to implementation of 

the SHRP-LTPP program.

LONG-TERM PAVEMEN

In Section 506 of the Surface Transportation Assistance Act of 1978 (Public Law 95-599), the Congress of 

the United States directed the Secretary of Transportation to study and investigate “. . . the need for long-term 

or continuous monitoring of roadway deterioration to 

determine the relative damage attributable to traffic 

and environmental factors.”12 This provision offered 

an opportunity to begin a serious initiative. 

The initiating agencies in the highway community—

FHWA, AASHTO, representing the State highway 

agencies, the Road and Transportation Association of 

Canada, and TRB—began preparations for SHRP and 

its long-term pavement monitoring component. These 

preparations extended from 1980 through the 1987 

SHRP authorization and included two major studies: 

the Long-Term Pavement Monitoring Study and the 

Strategic Transportation Research Study. In connection 

with these studies, the partners began forming an organizational structure to carry out the LTPP program and 

to formulate plans for the pavement experiments. The 

FHWA also funded the Pavement Condition Monitoring Methods and Equipment Study in 1985 to evaluate 

and select the best available equipment for the data collection effort. These preparations are described below.

Long-Term Pavement Monitoring St

The FHWA’s Office of Highway Planning developed 

concepts for a long-term pavement monitoring study, 

drawing strongly on opinions and ideas from other 

offices of FHWA. It was decided to shape the proposed 

effort as a cooperative program among FHWA, an 

AASHTO Advisory Panel, and participating highway 

agencies. In June 1981, a joint meeting of the TRB Pavement Management Task Group, AASHTO Joint Task 

Force on Pavements, and FHWA was held to plan for 

pilot studies to assess the feasibility of conducting a 

large-scale, long-term pavement monitoring program 

and the potential opportunities and challenges in 

building a national database that could be used to 

improve understanding of pavement damage relationships. The initial study, the Long-Term Pavement Monitoring Study, a cooperative program among FHWA, 

AASHTO, and eight States, was implemented in 1982 

to monitor selected pavements in those States (Arkansas, California, Colorado, Idaho, Iowa, New Mexico, 

Pennsylvania, and Washington).13

The primary objectives of the pilot effort were to 

assess the problems associated with building a database 

that could be used to improve existing design procedures, evaluate rehabilitation techniques, examine the 

effectiveness of construction techniques and maintenance procedures, and respond to questions asked by 
4    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Congress on pavement issues. Funding for the pilot 

study was provided under an FHWA contract managed 

by the Office of Research and Development. The 

FHWA’s Office of Highway Planning provided support 

and additional oversight.

One of the first efforts undertaken in this study was 

to develop a guide for data collection.14 Findings 

revealed that while within the States a significant body 

of knowledge was available, across the States methods 

used to collect and record pavement information varied widely, making use of the data on a national scale 

difficult or impossible. The Data Collection Guide,

developed over several years, sought to bring consistency to the collection of both project-specific and 

network-level data. This guide used the Concrete Pavement Evaluation System15 as a starting point, and then 

added significant detail with input from recognized 

professionals in the industry. 

In October 1984, FHWA sponsored the Long-Term 

Pavement Monitoring Workshop, where experts from 

Federal, State, and private agencies reviewed the States’ 

experiences in the pilot program. Looking ahead to the 

proposed LTPP program, the industry experts refined 

the stated objectives, data needs, and data collection processes associated with long-term pavement monitoring. 

Participants agreed that, to be successful, the proposed 

program must have “a long-term commitment of money 

and dedicated permanent staffing.”16 They also called for 

better uniformity in data collection, better historical 

records of performance, standardized data definitions, 

and standardized procedures for collecting the data, as 

well as extensive training in collecting and processing 

data. The results of the Long-Term Pavement Monitoring Study showed that it was feasible to identify a set of 

test sections in multiple States, implement a standardized 

data collection procedure, and collect key information 

that could be used to satisfy the objectives of the study. 

Strategic Transportation Research S

Concurrent with the Long-Term Pavement Monitoring 

Study, FHWA commissioned TRB to conduct a study to 

develop a strategy for a major new research emphasis 

on key technological gaps with a potential for high 

payoff. The results of this effort, called the Strategic 

Transportation Research Study, were published in 

1984 in the “Stars” report, TRB Special Report 202, 

America’s Highways, Accelerating the Search for Innovation (figure 1.1).17 One of the primary recommendations from this study was for long-term pavement 

monitoring. As it became clear that the major agencies 

involved in pavement design, construction, and management were recognizing the need for a national database of long-term data from highway monitoring, they 

joined together to develop these plans.

A committee of highway leaders directed the Strategic Transportation Research Study. This committee 

focused on developing a national research program 

aimed at high priorities that were not being adequately 

addressed by existing programs. They compared the 

distribution of highway agency expenditures with that 

of highway research expenditures to identify research 

areas that were being neglected relative to their importance to the agencies. Materials, paving technology, 

and maintenance emerged as areas of high agency 

investment that were being neglected in research. The 

committee chose six technical research areas in which 

focused, accelerated, results-oriented research promised significant benefits.

The committee recommended that $150 million be 

spent over 5 years, funded by 0.25 percent of Federal-Aid 

Highway Program funds. The committee also presented 

a brief assessment of several administrative options 

under which the proposed program could be managed. 

In July 1984, AASHTO approved the recommendations of the Strategic Transportation Research Study and 

SHRP was established to carry out the proposed 5-year 

research program.18 The objectives for the six technical 

areas for the SHRP study in the Stars report were developed further during SHRP planning (see sidebar on 

facing page).

Figure 1.1. Report of

Strategic Transportati

Research Study, TRB Spe

Report 202 (1984) or “Stars

report, which identified

high-priority areas for a

national highway research

program.
1: origs of the

The FHWA-sponsored Long-Term Pavement Monitoring Study and the Strategic Transportation Research 

Study generated enthusiasm for the SHRP proposal 

and its LTPP component. FHWA, with the SHRP office 

and its Advisory Committee, began developing a transition plan to transfer FHWA’s monitoring activities to 

SHRP. FHWA funded these pre-implementation activities, outlined in the next section, to maintain the 

momentum until SHRP was officially authorized and 

funded by Congress, which occurred in the 1987 highway authorization bill, the Surface Transportation and 

Uniform Relocation Assistance Act.19

FHWA Maintains Monitoring Momentu

Until SHRP-LTP

The FHWA and contractor staff had been involved in 

the Long-Term Pavement Monitoring initiative for 3 

years (1982–1984) when FHWA decided to support 

SHRP in planning the LTPP study. LTPP transition 

activities were undertaken through increased scope 

and revision of FHWA’s ongoing Long-Term Pavement 

Monitoring contract. As previously stated, this project 

had demonstrated that a national data collection effort 

was feasible and that uniform data collection procedures 

would allow the creation of a uniform database of information, which in turn would allow the objectives of the 

SHRP-LTPP study to be realized. 

In October 1984, under the auspices of TRB’s 

National Cooperative Highway Research Program 

(NCHRP) Project 20-20, “SHRP Research Plans,” the 

office of the SHRP interim director was established 

and plans were set in motion to implement SHRP 

under the guidance of a special task force. Six contractors were selected in early 1985 to develop the specific 

research plans for the six technical areas, including 

Pavement Performance. The technical assistance conAsphalt: To improve pavement performance through 

increased understanding of the chemical and physical properties of asphalt cements and asphaltic 

concretes. The research results would be used to 

develop specifications, tests, and construction procedures needed to achieve and control the pavement performance desired. . . . 

Long-Term Pavement Performance: To incr

pavement life by investigation of various designs of 

pavement structures and rehabilitated pavement 

structures, using different materials and under 

different loads, environments, subgrade soils, and 

maintenance practices. . . . 

Maintenance Cost-Effectiveness: To develop elements of pavement maintenance management systems, which establish budgets, administer program

and allocate resources more efficiently. In addition, 

the development of equipment, materials, and 

processes that will increase the productivity and 

reduce service life costs of pavement maintenance 

are also sought. . . . 

Concrete Bridge Component Protection: To pro

methods to protect existing chloride-contaminated 

concrete components against deterioration and to 

rehabilitate and protect those components that are 

already exhibiting corrosion-induced distress. . . . 

Cement and Concrete: To increase service life throu

an improved understanding of the chemistry of 

cement hydration, the properties of concrete, and 

the performance of concrete in the highway environment. Particular attention will be given to improving 

the understanding of the mechanisms of setting and 

strength development, and the chemical processes 

during hydration of the cementitious component. 

Attention will also concentrate on improving the production, placement, quality control, nondestructive 

testing, and durability of concrete. . . . 

Snow and Ice Control: To provide more cost-effectiv

ways to remove the buildup of snow and ice on highways and streets during winter conditions; reduce 

deterioration of bridges, pavements, and vehicles; 

and mitigate adverse environmental consequences 

of snow and ice control.20

Objectives of the S
6    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

potential types of studies: General Pavement Studies 

(GPS), Specific Pavement Studies (SPS), and Accelerated 

Pavement Testing. It was later decided to pursue Accelerated Pavement Testing research through avenues 

other than SHRP. Development of the experimental 

design matrices for the GPS and SPS experiments are 

detailed in chapter 5.

Following adoption of the research plans, detailed 

presentations were made at the 1986 TRB Annual Meeting to broaden awareness of SHRP among highway representatives in the United States and abroad. The 

research plans were published in a document, Strategic 

Highway Research Program Research Plans, Final Report,

May 1986.21 This publication is known as the “Brown 

Book” to many (figure 1.2), and it laid the foundation for 

all of the research work to be conducted under SHRP, 

including the LTPP studies. It is a valuable reference for 

anyone seeking to learn about the program, providing a 

comprehensive list of the organizations and people 

involved in the development, review, and oversight of 

the program. The Brown Book established the goals and 

objectives for each of the six technical research areas. A 

year after its publication, SHRP officially began.

Pavement Condition Monitoring Meth

and Equipment Stu

Meanwhile, in 1985, FHWA funded the Pavement 

Condition Monitoring Methods and Equipment Study 

contract. The study was designed to serve both the 

pre-implementation needs of LTPP planning and the 

industry in general by evaluating deflection and pavement distress survey equipment and methods offered 

at the time. 

The study included a comprehensive comparison of 

deflection equipment, conducting the first side-by-side 

tractor and staff for the pavement performance technical area were involved in the planning, and later the 

implementation, of the LTPP program. 

The AASHTO Task Force on the Strategic Highway 

Research Program was appointed, and the Task Force 

established advisory committees for each of the technical research areas of SHRP. The SHRP-LTPP Advisory 

Committee included about 30 representatives from 

highway agencies, industry, academia, FHWA, a city, 

and a county (appendix A). The Advisory Committee 

met for the first time in February 1985, and members 

were briefed by the interim director for SHRP on SHRP 

planning, by FHWA on the plan for transitioning from 

the Long-Term Pavement Monitoring Study to the LTPP 

component of SHRP, and by the contractors relative to 

their proposed approach to the experimental design. 

The findings and recommendations from the 1984 LongTerm Pavement Monitoring Workshop were reviewed. 

The Advisory Committee discussed issues such as what 

types of pavements should be studied, developed a set of 

objectives, made decisions on management of the program, and decided what portions of the transition plan 

they supported.

A procedure was developed at this meeting for iterative review and guidance, with Advisory Committee 

meetings occurring approximately every 2 months. 

The approach was for the FHWA and contractor team 

to proceed with the experimental design and other 

assignments and to present the results of these studies 

to the Advisory Committee. The Advisory Committee 

would then discuss these presentations and other 

issues that surfaced and provide decisions and guidance for the team to follow as the work progressed to 

the next checkpoint. This procedure became a very 

effective means of gaining input from the highway 

community and guidance from those selected to supervise the planning of the LTPP study.

A national SHRP workshop was held in Dallas in 

September 1985 to provide a preview of the research 

plans under development for the technical areas. U.S. 

and foreign professionals were invited. At the end of 

October 1985, the Advisory Committee held its fifth 

meeting to finalize the research plan. The resultant 

plan was presented to the AASHTO Task Force in 

November 1985, and received unanimous approval. 

The plan for pavement monitoring included three 

Figure 1.2. The 

Strategic Highway 

Research Program 

Research Plans, known

as the “Brown Book.”
1: origs of the

field tests of the Dynatest falling weight deflectometer 

(FWD), Kuab FWD, Phoenix FWD, Benkelman Beam, 

C.E.B.T.P. (France’s Center for Experimental Research 

and Studies of Building and Construction) Curvimeter, 

Dynaflect, and Road Rater. The results of this comparison were published in Evaluation of Pavement Deflection Measuring Equipment.22

To get a better understanding of state-of-the-practice 

pavement distress survey methods and to improve upon 

them, a companion track of the study evaluated, on a 

common set of test sections, the results of the following 

distress survey technologies:

•	 Manual distress mapping.

•	 Detailed visual surveys using manual recording and

automated data logging. 

•	 PASCO ROADRECON survey vehicle.

•	 GERPHO survey vehicle.

•	 ARAN (Automatic Road Analyzer) survey vehicle.

•	 Laser Road Surface Tester survey vehicle.

PASCO was at the time a Japanese firm; the GERPHO 

vehicle was of French origin and widely used in Europe 

in the 1980s.23

The results of this comparison study were published 

in Improved Methods and Equipment to Conduct Pavement Distress Surveys.24 This study set the course for 

the rigorous equipment performance specifications 

that the LTPP program has maintained to ensure consistency and accuracy in data collection.

Early Coordination Activit

By the time these preliminary studies had reached 

their conclusions and the LTPP study under SHRP 

officially began in 1987, the structure to carry it out 

was in place. People from different organizations had 

joined in a concerted effort to develop a sound 

research program. Management was in the hands of 

the SHRP interim director, later director, assisted by 

SHRP engineers assigned to the four LTPP regions 

established by SHRP. Day-to-day LTPP operations 

were carried out by the technical assistance contractor (in later years called technical support services 

contractor) and four regional coordination office 

contractors (in later years called regional support 

contractors), who had assisted with preparations for 

the program prior to 1987. 

The highway agencies were heavily involved in 

these initial phases, for they provided the pavements 

with which the experiments could be carried out, as 

well as some of the required data. The basic structure 

of the program and the roles and responsibilities of 

these participants are described in chapter 2 for both 

this SHRP-LTPP period and the program’s continuation under FHWA from 1992 forward. 

LONG-TERM PA

GOAL AND OBJ

The goal established for the SHRP-LTPP studies was 

“to increase pavement life by the investigation of longterm performance of various designs of pavement 

structures and rehabilitated pavement structures, using 

different materials and under different loads, environments, subgrade soil, and maintenance practices.”25

This goal was established by the Strategic Transportation Research Study and adopted by the SHRP-LTPP 

Advisory Committee. The Advisory Committee identified six specific objectives to support the goal:

1. Evaluate existing design methods.

2. Develop improved design methodologies and strategies for the rehabilitation of existing pavements. 

3. Develop improved design equations for new and 

reconstructed pavements.

4. Determine the effects of (1) loading, (2) environment, 

(3) material properties and variability, (4) construction quality, and (5) maintenance levels on pavement 

distress and performance.

5. Determine the effects of specific design features on 

pavement performance.

6. Establish a national long-term pavement data base 

to support SHRP objectives and future needs.26

Building the LTPP database, the final objective, is key 

to achieving the first five objectives. Although research 

to answer key performance-related questions can be 

conducted at any time, monitoring the changes as they 

develop in the pavement is a time-critical mission. In 

addition, the monitoring data must be collected systematically and consistently over the life of the pavement, as 

demonstrated by the findings from the early studies that 
8    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

were conducted. As such, the LTPP program’s efforts 

were initially focused on obtaining equipment, developing protocols, and maintaining schedules for routine 

data collection to populate the national pavement performance database with research-quality data.

SUMMA

By the 1980s, substantial knowledge had been accumulated related to the design and construction of highways. A variety of materials had been employed in 

many ways to reflect the experience of pavement engineers as to the best ways to support transportation 

needs as economically as possible. Numerous design 

procedures had evolved over time, each representing 

some form of model for pavement performance, and 

construction techniques and specifications had also 

been developed and refined. Although the traveling 

public had generally been well served, the service life 

expectations of the pavements constructed were sometimes not achieved, and the successes were not always 

cost effective. By the mid-1980s, a lot had been learned, 

but managers and engineers realized that more could 

be done to predict with greater confidence how different designs would perform and how new technologies 

could benefit the science of pavement engineering.

The LTPP program began with a high level of support from the U.S. Congress and a wide array of organizations—State, Provincial, and local highway agencies 

and departments of public works; engineering firms 

and consultants; manufacturers of pavement materials 

and highway-related trade groups; highway engineers; 

university departments of civil engineering; research 

institutes; and other agencies—who were represented 

in formulating the program through the SHRP research 

advisory committee. Considerable advance research, 

including the pilot Long-Term Pavement Monitoring 

Study, the Strategic Transportation Research Study, 

and the Pavement Condition Monitoring Methods and 

Equipment Study, provided important preparation 

activities. Most notably, the SHRP research plans, 

funded by FHWA, laid the groundwork for the LTPP 

study and the many years of work that would follow. 

This preparation and additional work during the early 

years of the program resulted in the final formulation of 

the LTPP experiments (table 1.1), a process described in 

chapter 5. As new technologies and high-performance 

materials emerge, the LTPP framework can be used to 

address the performance questions these advances elicit. In 2012, for example, the LTPP program began plans 

to monitor the performance of different warm-mix 

asphalt technologies. Recruitment began in 2014 with 

the expectation that a warm-mix site will be monitored 

in each of the 50 States and 10 Canadian Provinces.

The next chapter discusses the management of the 

LTPP program since its inception to its present day. 

Table 1.1. LTPP General and Specific Pavement Study ex

General Pavement Study (GPS) Experiments Specific Pavement Study (SPS) E

GPS-1 Asphalt Concrete Pavements on Granular Base

GPS-2 Asphalt Concrete Pavements on Bound Base

GPS-3 Jointed Plain Concrete Pavements

GPS-4 Jointed Reinforced Concrete Pavements

GPS-5 Continuously Reinforced Concrete Pavements

GPS-6 Asphalt Concrete Overlay of Asphalt Concrete

Pavements 

GPS-7 Asphalt Concrete Overlay of Portland Cement

Concrete Pavements 

GPS-8 Bonded Portland Cement Concrete Overlay

(discontinued, later replaced by SPS-7

GPS-9 Unbonded Portland Cement Concrete Overlay

of Portland Cement Concrete Pavements 

SPS-1  trategic Study of Structural Factors for Flexible Pav

SPS-2  trategic Study of Structural Factors for Rigid Pav

SPS-  Preventive Maintenance Effectiveness of Flexible Pavement

SPS-  Preventive Maintenance Effectiveness of Rigid Pavement

SPS-  Rehabilitation of Asphalt Concrete Pavement

SPS-  Rehabilitation of Jointed Portland Cement Concret

Pavements 

SPS-  Bonded Portland Cement Concrete Overlay of Portlan

Cement Concrete Pavements 

SPS-8  tudy of Environmental Effects in the Absence of H

Loads 

SPS-  Validation of Strategic Highway Research Program Aspha

Specification and Mix Design (Superpave

SPS-10 Warm-Mix Asphalt Overlay of Asphalt Pavements (201
1: origs of the

RE

1. U.S. Statutes at Large 101 (1987): 132–261. Surface 

Transportation and Uniform Relocation Assistance Act.

2. America’s Highways: Accelerating the Search for 

Innovation (Special Report 202), Transportation 

Research Board, National Research Council, 

Washington, DC, 1984, pp. 27–33.

3. Committee for a Study for a Future Strategic Highway 

Research Program. Strategic Highway Research: Saving 

Lives, Reducing Congestion, Improving Quality of Life 

(Special Report 260). Transportation Research Board, 

National Research Council, Washington, DC, pp. 32–45, 

2001. http://www.nap.edu/openbook.php?record_

id=10223&page=32.

 4. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986, p. 1.

5. America’s Highways: Accelerating the Search for 

Innovation (Special Report 202), Transportation 

Research Board, National Research Council, 

Washington, DC, 1984, p. 7. 

6. AASHO Interim Guide for Design of Pavement

Structures. American Association of State Highway 

Officials, 1961, 1972. 

7. National Cooperative Highway Research Program. 

AASHTO Guide for Design of Pavement Structures. 

American Association of State Highway and Transportation Officials, Washington, DC, 1972, 1993. 

8. Supplement to the AASHTO Guide for Design of 

Pavement Structures. Part II—Rigid Pavement Design 

and Rigid Pavement Joint Design. American Association 

of State Highway and Transportation Officials, 

Washington, DC, 1998. 

9. The AASHO Road Test: Special Report 61A. History and 

Description of the Project. Highway Research Board, 

National Research Council, National Academy of 

Sciences, Washington, DC, 1961. 

10. J. Brent Rauhut and David S. Gendell. “Proposed 

Development of Pavement Performance Prediction 

Models from SHRP/LTPP Data,” presented at the 

2nd North American Pavement Management 

Conference, 1987, pp. 2.23–2.24. 

11. A. L. Simpson, G. R. Rada, and A. López, Jr. 

“Contributions of the Long-Term Pavement Performance Program to Pavement Management System 

Improvements: Better Data and Performance Models,” 

presented at the 7th International Conference on 

Managing Pavement Assets, 2008. 

12. U.S. Statutes at Large 92 (1978): 2760. Surface 

Transportation Assistance Act of 1978.

13. L. G. Byrd. “Pavement Performance: A Key Element in 

the Strategic Highway Research Program,” presented 

at the 1st North American Pavement Management 

Conference, 1985. 

14. Data Collection Guide for Long-Term Pavement Performance Studies, Operational Guide No. SHRP-LTPPOG-001. Strategic Highway Research Program, National 

Research Council, Washington, DC, January 1988.

15. M. I. Darter, J. M. Becker, M. B. Snyder, and R. E. Smith. 

Portland Cement Concrete Pavement Evaluation System 

(COPES), NCHRP Report 277. Transportation Research 

Board, Washington, DC, 1985. 

16. L. G. Byrd. “Pavement Performance: A Key Element 

in the Strategic Highway Research Program,” presented 

at the 1st North American Pavement Management 

Conference, 1985, pp. 4–30. 

17. America’s Highways: Accelerating the Search for Innovation

(Special Report 202). Transportation Research Board, 

National Research Council, Washington, DC, 1984.

18. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986, p. iv.

19. L. G. Byrd. “Pavement Performance: A Key Element in 

the Strategic Highway Research Program,” presented 

at the 1st North American Pavement Management 

Conference, 1985, pp. 4–33.

20. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986, 

pp. 8, 14, 15, 17, 19, and TRA 2-6. 

21. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986.

22. W. R. Hudson, G. E. Elkins, W. Uddin, and K. T. 

Reilley. Evaluation of Pavement Deflection Measuring 

Equipment (FHWA-TS-87-208). Federal Highway 

Administration, Washington, DC, March 1987. 

23. Z. Hoque. “Highway Condition Surveys and Serviceability Evaluation.” The Handbook of Highway Engineering. T. F. Fwa., Ed. CRC Press, CRCnetBase, 2005. 

http://www.crcnetbase.com/isbn/9781420039504.

24. Improved Methods and Equipment to Conduct Pavement 

Distress Surveys: Final Report (FHWA-TS-87-213). Federal 

Highway Administration, McLean, VA, April 1987.

25. America’s Highways: Accelerating the Search for 

Innovation (Special Report 202). Transportation 

Research Board, National Research Council, Washington, DC, 1984, p. 80. 

26. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986.
10    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Managing the LTPP program presents budgetary, administrative, 

and technical challenges, requiring the cooperation of 62 transportation 

agencies and involving the concerns of numerous stakeholders 

in the highway community.

© S.Dashkevych/Rawpixel/Shutterstock.com
2: MANAGEMENT OF THE LTPP PROGRAM    11

Management of the LTPP Program

2

Introduct

The LTPP program began operations in 1987 under 

the 5-year, $150 million, Strategic Highway Research 

Program (SHRP) administered by the National 

Research Council of the National Academy of Sciences. 

In 1991, the Federal Highway Administration (FHWA) 

made a commitment to assume LTPP management 

and administrative responsibilities when SHRP ended 

in 1992 to complete the pavement performance monitoring. From the program’s inception, it was understood that realizing the full benefit of this research 

investment would require the program to continue 

over the long term. Experience has shown that even 

periods upwards of 40 years are needed to better 

characterize the performance of some types of pavement structures.

Ambitious objectives were set for the LTPP program from the start, whose achievement has been challenged 

by multiple internal and external factors including transitions between two management agencies and 

five highway legislations. The program’s success can be attributed to the support and investment of the 

participating highway agencies, the expertise of the advisory structure, and the tenacity and focus of 

management staff who guided and executed the program with the support of its professional contractors. 

It was also understood that for the LTPP program to 

meet its objectives, the individual experimental studies 

in the program had to be carefully designed to yield verifiable conclusions, and the massive data collection effort 

had to be uniform and consistent from study to study and 

from place to place. The data had to be stored and made 

readily accessible to all LTPP participants and future 

researchers. These conditions required a nationwide 

level of cooperation among highway agencies, researchers, contractors, and national organizations seldom seen 

in pavement research. SHRP and then FHWA managed 

and coordinated this multi-organizational effort with the 

cooperation of the highway agencies, advisory groups, 

and sister organizations, and with the assistance of contractors at the regional and national levels.
12    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

It was thought that data collection activities would 

be most effectively managed on a regional basis provided that adequate quality assurance (QA) programs were 

in place to ensure quality and consistency. Four regions 

were defined in the United States and Canada—North 

Atlantic, North Central, Southern, and Western—each 

with an office established and staffed by contracted 

firms with expertise in pavement performance monitoring. The LTPP regional offices served as collection 

and validation centers for pavement section data. In 

addition, a technical assistance contractor assisted 

SHRP and, later, FHWA management in overseeing the 

program. Figure 2.1 shows the four LTPP regions, their 

boundaries, and the locations of the LTPP offices.

This chapter describes the program’s management 

through national and regional contracts and staffing 

arrangements, first under SHRP (1987 to 1992), then 

under the transitional period when SHRP was ending 

(1991 to 1992), and finally under FHWA’s management 

(1992 through the present). During the latter period, 

funding levels under U.S. highway legislation have varied. Priorities and activities are often driven by the 

availability of funds, and reductions in Federal funding 

have had a major impact on the LTPP program. Additional management issues related to these changes in 

Federal funding are discussed in chapter 4. This chapter also discusses the various communication, coordination, and outreach practices followed by the LTPP 

program throughout the years.

UNDER THE STRATEGIC

RESEARCH PROGRAM (19

The Surface Transportation and Uniform Relocation 

Assistance Act of 1987 authorized and provided funding to SHRP. That same year, under the sponsorship of 

the National Research Council, a SHRP program office 

was established in Washington, DC, continuing the 

pre-implementation work and contractual relationships that had been ongoing since 1984 for a long-term 

monitoring study (discussed in chapter 1). Of the six 

research areas proposed for SHRP, operations began in 

 

Key Milestones in the Management

of LTPP

1987 SHRP 5-year program 

authorized and funded by Surface 

Transportation and Uniform 

Relocation Assistance Act 

1987 SHRP awards Technical Assistance 

Contract

1987 SHRP establishes Pavement 

Performance Advisory Committee 

1987 SHRP awards four Regional 

Coordination Office Contracts to 

begin in 1988

1991 Transition to FHWA management of 

LTPP begins

1991 FHWA funding for LTPP continuation 

granted by Intermodal Surface 

Transportation Efficiency Act

1992 SHRP ends; FHWA assumes 

management of LTPP

1992 FHWA awards its first Technical 

Assistance Contract and Regional 

Coordination Office Contracts

1993 FHWA contracts with TRB for 

services of Pavement Performance 

Advisory Committee

1995 TRB establishes Long-Term 

Pavement Performance Committee

2006 Customer support functions 

transferred from contract to LTPP 

Team and General Administration 

Support Contract

2006 Six TRB LTPP ETGs merged into two

2011 First LTPP Webinar held

2013 Two TRB LTPP ETGs merged into one

© Gubin Yury/Shutterstock.com
2: MANAGEMENT OF THE LTPP PROGRAM    13

four: Asphalt Characteristics, Concrete and Structures, 

Highway Operations, and Long-Term Pavement Performance.1,2 (The proposed Snow and Ice Control and 

Maintenance Cost-Effectiveness research areas were 

combined in the Highway Operations area, which also 

addressed work zone safety. The proposed Concrete 

Bridge Component Protection and Cement and Concrete research areas were combined within the Concrete and Structures area.)

The SHRP executive director was responsible for 

overall program management, while four SHRP program managers were responsible for the daily operations in their respective focus areas with the support of 

a small staff of engineers and loaned staff, who played a 

major role in the program. Collectively, the SHRP 

executive director, program managers, and support 

staff represented the central management staff for the 

four SHRP program areas. 

For the LTPP program area, a senior engineer, the 

SHRP-LTPP director, was responsible for all technical 

activities, and four other engineers in the SHRP central 

office were individually responsible for pavement 

monitoring activities, field sampling and materials 

testing activities, database operations, and traffic monitoring activities. The management structure is shown 

in figure 2.2.

In addition, four engineers contracted to SHRP 

served as extensions to the central LTPP management 

staff, each based at one of the four regional coordination offices. The SHRP regional engineers were responsible for overseeing and reporting on the regional 

contractors’ activities to the central management staff 

in Washington, DC, as well as for providing overall 

support to the regional offices in a variety of activities 

including program marketing and test section recruitment. Specific activities carried out by regional engineers included the following:

•	 Providing administrative and technical review of

regional contractor functions.

•	 Providing written and verbal comments and recommendations on various technical and administrative 

aspects of the existing program and proposed new 

program elements.

•	 Representing the LTPP program at various meetings, seminars, and training sessions held within 

their respective regions.

•	 Representing the LTPP program at various meetings

for recruitment and development of LTPP test sites.

Figure 2.1. The four LTPP reg

and current regional offices (Nort

Atlantic and North Central: Buffal

Southern: Austin, TX; Western: Ren

NV). In 2003, Buffalo, NY, became 

regional office for both the Nor

Atlantic and North Central regi

The office for the central technical

support services contractor is also

shown: Beltsville, MD

WESTERN 

REGION

NORTH 

CENTRAL

REGION

SOUTHERN

REGION

NORTH ATLANTIC

REGION

Hawaii

Puerto

Rico

Alaska
14    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

NATIONAL ACADEMY O

NATIONAL RESEARCH COUNCIL

STRATEGIC HIGHWAY RESEAR

(SHRP

Executive Committee

SHRP EXECUTIVE

SHRP Central Office

Pavement Performance 

Advisory Committee and 

Expert Task Groups

Asphalt Characteristics 

Research Area

Highway Operations 

Research Area

LTPP Coordinator

Highway Agency Staff

Concrete and Structures 

Research Area

Long-Term Pavement 

Performance Research 

Area 

SHRP CENTRAL OFFI

SHRP-LTPP Director

SHRP-LTPP Senior Engineers

SHRP-LTPP Technical Engineers

SHRP-LTPP Loaned Staff

SHRP-LTPP Contracto

Technical Assistance Contractor

Testing and Data Collection Contractors

Information Management System Contractor

Data Analysis Contractor

LTPP North Atlantic Regional O

Regional Coordination Office Contractor

SHRP-LTPP Regional Engineer

LTPP North Central Regional

Regional Coordination Office Contractor

SHRP-LTPP Regional Engineer

LTPP Southern Regional Of

Regional Coordination Office Contractor

SHRP-LTPP Regional Engineer

LTPP Western Regional Of

Regional Coordination Office Contractor

SHRP-LTPP Regional Engineer

Figure 2.2. Structure of the LTPP organization during the SHRP-LTPP years (1987
2: MANAGEMENT OF THE LTPP PROGRAM    15

•	 Serving as the focal pointfor public information and

comments concerning the LTPP program.

•	 PromotingLTPPprogram activities, goal, and objectives, and the products of SHRP.

•	 Reviewing and validating payment claims from

materials testing contractors. 

Additional staffing was provided to the LTPP program 

through the loaned staff program (see sidebar), which 

allowed employees of highway and transportation 

agencies (both national and international) to assist in 

program implementation while bringing their agencies’ perspectives to program management at the 

national level. FHWA had staff on loan to SHRP from 

the program’s inception. For example, in May 1987, six 

of the 10 SHRP-LTPP staff were on loan: one from 

FHWA, one from Sweden, one from Canada, and three 

from highway agencies. Other professional experts 

who contributed to the LTPP program through the 

loaned staff program were university professors and 

researchers. In some cases, professors were on sabbatical while working with the LTPP program staff. When 

SHRP ended and FHWA assumed management, the 

practice continued. Nearly 100 individuals have participated in the LTPP program through these interagency loans, providing both practical support and an 

essential cross-fertilization of ideas to the program.

Technical Assistance Contractor Responsibili

The P-001 LTPP Technical Assistance Contract, 

awarded in 1987, was the first contract under the LTPP 

program. The central LTPP management staff retained 

the services of this contractor to provide technical and 

management services in support of SHRP in the development and conduct of the LTPP studies. The contractor was referred to as the “technical assistance 

contractor” under SHRP. The activities provided by 

this contract included the following: 

•	 Completing the General Pavement Study experimental designs, building upon the framework that 

was developed during the 1985–87 SHRP preimplementation effort.

•	 Assisting highway agencies and the LTPP regional

contractors in the selection of monitoring sites.

•	 Assisting in the selection and procurement of equipment and services for data collection, materials testing, and other tasks.

Loaned Sta

The LTPP program has been enriched through the 

direct participation of staff from highway agencies in the States and Provinces and abroad since 

the early SHRP years. To encourage participation, 

a loaned staff program was developed under 

which a highway agency employee, nominated by 

his or her agency, could complete a 1-year or 

longer tour of duty working with the LTPP Team. 

The sponsoring highway agency supported the employee’s salary during the loan period, and SHRP 

and later FHWA supplied a housing allowance. 

The program allowed the loaned staff to 

broaden their technical expertise and interact 

with the pavement community at the national 

and international levels, while giving their 

agencies a voice in the direction of the program. 

Typically, loaned staffers tended to focus their 

efforts on specific technical activities such as 

traffic monitoring and seasonal monitoring. The 

LTPP program benefited as the team gained 

first-hand knowledge of the operations, perspectives, and priorities of highway agencies. This 

mutual arrangement benefited both the LTPP 

program and the highway agencies.
16    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 Assisting the highway agencies in the assembly of

all necessary test section inventory data describing 

existing and past conditions regarding design, traffic, construction, maintenance, rehabilitation, environment, and skid resistance.

•	 Inspecting all candidate sites to verify the accuracy

of inventory data, adherence to experiment requirements, and proper identification of the sites with 

signs.

•	 Utilizing SHRP-LTPP data collection procedures.

•	 Scheduling and coordinating data collection activities with highway agencies that provided traffic 

control during data collection.

•	 Scheduling emergency data collection when conditions required it, such as during unexpected 

maintenance. 

•	 Scheduling and supervising the field testing and

sampling of test sections, which were performed by 

highway agencies, and forwarding the samples 

obtained to the designated testing facilities.

•	 Collecting deflection data from each site using

falling weight deflectometer (FWD) equipment

provided by SHRP and collecting profile data using 

the road profiling systems provided by SHRP.

•	 Collecting distress and transverse profile data

with other contractors selected by SHRP to collect 

these data.

•	 Performing data reduction and data input for all test

section measurements into the LTPP database using

computer equipment and software provided by SHRP.

•	 Coordinating with highway agencies to obtain monitoring data on maintenance, rehabilitation, traffic 

counts, vehicle classification and weight, and friction measurements (friction data were collected for 

a short period).

•	 Training highway agency personnel on LTPP data

collection, monitoring procedures, and QC to ensure 

adherence to the stipulated requirements.

•	 Coordinating and conducting other similar LTPP

activities as these evolved during the program.

•	 Coordinatingwith SHRP and the other regional coordination office contractors to assure that the overall 

program was efficiently and consistently executed.

•	 Providing field data collection services to other

SHRP research activities.

•	 Developing and implementing methods and procedures for data collection, sampling, and testing, with 

necessary provisions for updating manuals and 

organizing additional training to ensure continued, 

consistent, and accurate data collection by State 

personnel and other SHRP research contractors.

•	 Developing and implementing QA and quality control (QC) procedures for collecting data and for 

collecting and testing samples.

•	 Assisting central SHRP staff in the coordination of

activities of other participants in the LTPP studies.

•	 Developing procedures for processing and entering

data into the national pavement performance database (i.e., LTPP database), including the processing of 

test section distress records to quantify distress data.

•	 Conducting periodic QC evaluations of all contractor and highway agency data collection activities.

•	 Developing the Specific Pavement Study (SPS)

experiments in coordination with highway agencies, 

other SHRP contractors, and advisory groups.

•	 Performing periodic analyses and statistical studies

on simulated and real data to evaluate the study 

designs and the utility of the database for producing 

the anticipated results and to highlight avenues of 

promising research.

•	 Developing procedures to obtain environmental data.

Regional Coordination Office Con

Responsibilitie

After the Technical Assistance Contract was awarded 

in 1987, several additional contracts were awarded to 

advance full implementation of the LTPP program. 

Many of these were directly associated with the four 

LTPP regions. 

Together with the LTPP Technical Assistance Contract, the four LTPP regional office contracts, implemented in 1988, represented the primary and largest 

(cost-wise) LTPP contracts (P-004, North Atlantic; 

P-005, Southern; P-006, North Central; and P-007, 

Western). The objective of the regional contracts was 

to provide technical and management services to 

SHRP in the collection of high-quality data and related 

activities in the development and conduct of the LTPP 

studies. The activities provided by these contractors 

included the following:
2: MANAGEMENT OF THE LTPP PROGRAM    17

•	 Maintaining SHRP-provided equipment, including

computers and testing equipment.

•	 Coordinating with highway agencies and SHRP

contractors to ensure that all safety standards and 

legal requirements were met.

•	 Working with highway agencies in the recruitment

and construction of SPS test sites.

•	 Hosting SHRP-LTPP regional meetings.

Other Contractor Responsibil

Other major LTPP contracts were awarded during the 

1987 to 1992 SHRP era (appendix B) to perform the 

following activities at the LTPP test sections: 

•	 Conduct photographic pavement surface distress

surveys and provide digital conversions of the film 

records (P-002 Pavement Distress Record Contract).

•	 Provide road surface profiling equipment used by

the regional coordination office contractors (P-003 

Road Profiling System Contract).

•	 Perform laboratory testing of Portland cement concrete materials (P-008 Portland Cement Concrete 

Laboratory Materials Testing Contract).

•	 Perform laboratory testing of asphalt, aggregate, and

soil materials for each region (P-012, P-013, P-014, and 

P-015 Regional Soil and Asphalt Testing Contracts). 

•	 Develop a management system to store data and

information (P-016 Information Management System Development Contract).

•	 Reimburse highway agencies for the purchase of

traffic data collection equipment (P-017 Traffic Data 

Collection Equipment Contract).

•	 Operate and maintain the Information Management

System (IMS) (P-019 Information Management 

System Operations Contract).

•	 Perform initial data analysis studies for the first

five LTPP program objectives (P-020 Data Analysis 

Contracts).

•	 Provide structural evaluation equipment used by

the regional coordination office contractors (P-021 

Falling Weight Deflectometers Contract).

•	 Perform drilling and materials sampling for each

region (P-022, P-023, P-024, and P-025 Regional 

Drilling and Materials Sampling Contracts).

•	 Provide technical advice and guidance for collecting traffic classification and weight data at LTPP 

test sites. 

Although not of the financial magnitude of those listed 

above, a few other contracts were awarded during the 

SHRP-LTPP era. Examples include the development 

and implementation of FWD calibration centers, 

which became a major SHRP product, and the evaluation of ground-penetrating radar technology for use in 

layer thickness determinations at LTPP test sections.3

The Materials Reference Library was established 

under a SHRP contract and later transferred to the 

LTPP program.

Expert Peer Review Grou

During the SHRP-LTPP years, the Pavement Performance Advisory Committee (hereafter Advisory Committee) provided oversight and guidance for the LTPP 

program. This was the first of two volunteer committees of the National Research Council of the National 

Academy of Sciences to provide advice pertaining to 

the LTPP program, and it performed its function until 

1995. The Advisory Committee provided programmatic 

review and technical commentary on the program 

objectives, long-range plans, near-term operational 

activities, and progress of the LTPP research program. 

It also conducted external, nongovernmental reviews 

of, and comments on, the technical progress of ongoing 

pavement performance research, and it identified 

needs for further research projects.

The committee was also required to provide assistance to FHWA in its selection and implementation of 

SHRP research products. Accordingly, some of its tasks 

included monitoring the SHRP implementation activities of FHWA and providing written critiques of 

specific technology transfer efforts related to SHRP 

products. The committee developed advice on alternative technology transfer techniques and other actions 

needed to ensure effective deployment of and technical support for SHRP research products.

Various subcommittees to the Advisory Committee, known as the Expert Task Groups or ETGs,

addressed specific program technical issues. Members of the ETGs were experts in their respective

research areas and were drawn from highway agencies, industry, academia, SHRP, and FHWA. Eight 

ETGs existed during the 1987 to 1992 SHRP period

of the LTPP program: 
18    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 Loaning FHWA staff members who were to become

part of the new central management staff to SHRP

during the transition period.

•	 Transferring paper and electronic files, data collection equipment, computer equipment and software, 

and 35-mm distress film from SHRP to FHWA. 

•	 Contracting by FHWA with the National Research

Council to continue providing the peer review functions of the LTPP Pavement Performance Advisory 

Committee and its supporting ETGs for a period of

15 months, from July 1, 1992, to September 20, 1993. 

As part of this contract, FHWA also retained the 

services of the LTPP regional engineers and took 

responsibility for the international coordination 

activities associated with the annual TRB meeting 

over the same 15-month period.

•	 Re-advertising and awarding, by FHWA, major

LTPP contracts that were in place under SHRP but 

were coming to an end. These included the four 

SHRP-LTPP Regional Coordination Office Contracts, awarded in May 1992, and a new materials 

testing contract to help highway agencies with SPS 

testing, awarded in June 1992. Other major contracts, such as the LTPP Technical Assistance Contract, were awarded shortly after the conclusion of 

the transition period. 

The last Pavement Performance Advisory Committee 

meeting under SHRP took place during the week of 

April 6, 1992, and the last SHRP Executive Committee 

meeting took place June 2–3, 1992. The seamless transition of LTPP program management and operation 

activities from SHRP to FHWA was completed on June 

30, 1992, and FHWA began administrating the program 

on July 1, 1992. Figure 2.3 shows the SHRP-LTPP and 

FHWA-LTPP staff members who served during the 

program transition.

It should be noted that FHWA also took over the 

responsibility of carrying on the activities and implementing the results and findings from the other three 

major SHRP research areas—Asphalt, Concrete, and 

Highway Operations. In addition, FHWA took over 

management of the Materials Reference Library established under the SHRP Asphalt research area, which 

over time would become an important repository of 

LTPP materials samples and 35-mm distress film as well 

•	 Deflection Testing and Backcalculation ETG.

•	 Equipment Evaluation ETG.

•	 Experimental Design and Analysis ETG.

•	 Automated Distress Identification ETG.

•	 Traffic Data Collection and Analysis ETG.

•	 Weigh-in-Motion Equipment and Technology ETG.

•	 Environmental Data ETG.

The membership and scope of the ETGs are described

in appendix A.

DURING THE SHRP-T

MANAGEMENT TRANSITION (1

In 1991, as SHRP was approaching the completion of its

mandate, a task force composed of high-level decision 

makers from the American Association of State Highway and Transportation Officials (AASHTO), FHWA, 

SHRP, and the Transportation Research Board (TRB) 

was assembled to evaluate and recommend the best 

approach for a seamless transition of the LTPP program 

from SHRP to a new management organization. 

The consensus of this task force was to recommend 

FHWA as the rational option for assuming management of the LTPP program in 1992 and seeing it 

through to its conclusion. FHWA was recommended 

for three reasons: 

•	 Logistics—Ability to work with the various players

involved in the program, including highway agencies, industry, academia, contractors, and international participants.

•	 Personnel—Ability to assign full-time employees to

the program without the need of contracts.

•	 Budget sustainability—Availability of funding to

ensure long-term continuation of the program to its 

end.

The task force established a transition period of 

December 18, 1991 (date on which the Intermodal 

Surface Transportation Efficiency Act or ISTEA was 

enacted) to June 30, 1992. Transition activities during 

that 6-month period included the following:

•	 Hiring of SHRP-LTPP staff by FHWA following

established agency procedures.
2: MANAGEMENT OF THE LTPP PROGRAM    19

FHWA. The LTPP Team falls under FHWA’s Office of 

Infrastructure Research and Development. Figure 2.5 

shows the organization of the FHWA-LTPP program.

The FHWA-LTPP team leader is responsible for 

overall program management and daily operations of 

the LTPP program. In addition to the team leader, the 

central FHWA-LTPP management staff includes these 

members:

•	 An engineer responsible for overseeing the LTPP

regional support contractors and for managing 

LTPP materials sampling and testing activities, 

including the various contractors, Materials Reference Library contract, and the contract for the latest 

LTPP experiment (warm-mix asphalt).

•	 An engineer responsible for LTPP database operation activities, the Technical Assistance Contract 

(more recently named “Technical Support Services 

Contract”), and the contract that has developed the 

as the repository of materials samples from other important national research studies.

UNDER THE FEDERAL 

ADMINISTRATION (1992–

Enacted December 18, 1991, ISTEA authorized continuation of the LTPP program and implementation of 

SHRP products under FHWA management (see sidebar). ISTEA also provided FHWA funding to support 

these activities. FHWA established the LTPP program 

office at FHWA’s Turner-Fairbank Highway Research 

Center (hereafter, the FHWA highway research center) in McLean, Virginia.

The FHWA organizational structure has changed a 

number of times since the LTPP program began; however, the 2012 structure presented in figure 2.4 fairly 

represents the LTPP program’s functioning within 

Figure 2.3. SHRP-LTPP and FHWA-LTPP staff members during the LTPP program transi

Front Row (left to right): Cal Berge, Cheryl Richter, Rita Leahy, Neil Hawks, Brenda Buchbinder, Margie Sheriff, Karen Smith, Kris Gupta, 

Paul Teng, Vondell Little. Second Row: Marsha Barrett, Guy Hager, Cindy Baker, Monte Symons, Keizo Kamiya, Juliet Narsiah, Marty 

Laylor, Cindy Johnson, Harry Jones, David Esch, Carliss Parker-Smith, Homer Wheeler. Third Row: Shahed Rowshan, Ivan Pecnik, Joe 

Lamond, Bill Carr, Bob Kelley, Kathy Brosseau, Don Harriott, Stella White, Ray Torrey, Lisa McNeil, Harold Von Quintus, Amir Hanna. 

Back Row: Aramis López, Bill Bellinger, Dick Ingberg, Brian Cox, Shashikant Shah, Damian Kulash, Jack Youtcheff, Radu Andrei, 

John Hibbs, Robert Raab, Ed Harrigan, K. T. Thirumalai.
20    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

LTPP Web-based system that allows users to access 

LTPP data and other program information.

•	 An engineer responsible for traffic data collection

and communication and coordination activities.

•	 An engineer responsible for data analysis activities

and profile operations.

The pavement performance monitoring activities as 

well as other LTPP functions not listed above, such as 

management of data collection equipment, product 

development, and customer support services, have 

been distributed among the team members based on 

their experience and the team’s needs. While there 

have been some functional changes of responsibilities, 

the structure of the LTPP Team has been consistent 

over the years. 

Between 1992 and 2002, the FHWA-LTPP central 

management staff also depended on the services of four 

FHWA engineers who were based at the LTPP regional 

coordination offices (although they are not shown in 

figure 2.5). These engineers performed the same functions assigned to the SHRP-LTPP regional engineers 

during the SHRP 1987 to 1992 period. 

Like the SHRP managers, the FHWA-LTPP Team 

has also counted on the support of loaned staff from 

State, Provincial, and international highway agencies, 

especially during the 1990s. These individuals typically 

have rotated on a 1- to 2-year basis and have tended to 

focus their efforts on specific technical activities such as 

deflection testing, traffic data collection, and the Seasonal Monitoring Program.

The States and Provinces continue to make significant contributions to the LTPP program under 

FHWA’s management, as they did during the SHRP 

years. The highway agencies provide test section construction, materials testing, traffic control and other 

data collection management support, staff, and equipment required for the broad array of LTPP activities. 

In addition, groups of States have entered into pooledfund agreements in support of several important 

LTPP activities for which no other financial support 

was available.

Technical Assistance Contractor Responsibili

The first FHWA-LTPP Technical Assistance Contract 

was awarded by FHWA in July 1992 to provide all necessary facilities, equipment, services, supplies, materials, 

and personnel to perform pavement engineering, traffic 

engineering, and IMS technical activities in support of 

the FHWA-LTPP program. Specific activities required 

under this contract have included the following:

•	 Participating in the development, refinement, and

assessment of pavement performance monitoring

activities conducted in support of LTPP research 

and providing technical services in the conduct of 

those activities, including such items as quality and 

uniformity of field operations for pavement distress 

In January 1992 at the 71st Annual 

TRB Meeting, Neil Hawks, SHRP-LTPP 

Program Director, and Paul Teng, FHWA 

LTPP Division Chief, announce the 

transfer of the LTPP program from 

SHRP to FHWA. This handshake 

marked the beginning of the transitional period, when the staff from 

both organizations worked together to 

ensure that the mission of the program 

would continue until the program’s goal 

and objectives were achieved.4

transition of
2: MANAGEMENT OF THE LTPP PROGRAM    21

Federal Hig

Office of Research, De

Office of Infrastructur

Research and Developm

• Program Management

• Bridge and Foundation 

Engineering Team

• Hazard Mitigation Team

• Infrastructure 

Management Team

• Long-Term Pavement 

Performance Team

• Pavement Design and 

Construction Team

• Pavement Materials Team

Office of Operati

Research and Developm

• Program Management

• Transportation Enabling 

Technologies Team

• Transportation Operations 

Applications Team

• Transportation Operations 

Concepts and Analysis 

Team

Office of Resou

Management

• Program Management

Office of Corpor

Research, Technology, an

Innovation Management

• Program Management

• Exploratory Advanced 

Research Team

• Innovation Management 

and Communications 

Team

• Research and Technology 

Program Development and 

Partnership Team

Office of Safety Resea

and Developme

• Program Management

• Human Factors Team

• Roadway Team

• Safety Management Team

Figure 2.4. LTPP within the FHWA Turner-Fairbank Highway Research Center organizational structure

data (both photographic and manual condition surveys), pavement profile data (both longitudinal and 

transverse), and deflection testing with FWDs,

among other items.

•	 Providing support services in the collection of

pavement response data using onsite instrumentation to monitor both environmental (i.e., temperature and moisture) changes and pavement 

response. Specific items covered have included 

dynamic load response, seasonal monitoring, and 

climatic data collection.

•	 Participating in the development, refinement, and

assessment of LTPP traffic data collection activities. Specific items covered have included providing the facilities and manpower to house and 

maintain the LTPP Central Traffic Database hardware and software, developing and maintaining 

standards for traffic data collection, developing 

procedures for QC review of data collection, developing specifications for the traffic data processing 

program, and documenting traffic data collection 

and processing procedures.

•	 Providing technical services in support of the LTPP

materials characterization program. Specific items 

covered have included developing QA criteria and 

precision statements, evaluating testing procedures, 
22    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

and assisting with other activities related to materials testing.

• Providing technical support to the LTPP staff in the 

development of procedures and specifications for QC/

QA on data in the LTPP IMS, including these activities:

– Providing specifications for software coding or 

database structure for the LTPP database for 

software development.

– Assisting with QC/QA procedures and checks.

– Assisting the LTPP regional and other contractors with data entry and processing, QC/QA 

checks, procedural issues, and data extraction.

– Developing and modifying software to help LTPP 

regional contractors track data. 

– Assisting in the review and revision of existing 

IMS manuals, procedures, and documentation 

OFFICE OF RESEARCH, DEVELOPMENT,

AND TECHNOLOGY

Turner-Fairbank Highway Research Center

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

OFFICE OF INFRASTRUCTURE

RESEARCH AND DEVELOPMENT

FHWA-LTPP OFFICE STAFF

LTPP Team Leader

LTPP Technical Engineers

TRB ADVISORY GROUPS

LTPP Committee and 

Expert Task Groups

LTPP Coordinators

Highway Agency Staff

FHWA-LTPP Contractors

Technical Support Services Contractor

General Administration Support Contractor

Materials Reference Library Contractor

Equipment and Data Collection Contractors

Web-Interface Portal Contractor

(LTPP InfoPaveTM)

LTPP North Atlantic Regional Office

Regional Support Contractor

LTPP North Central Regional Office

Regional Support Contractor

LTPP Southern Regional Office

Regional Support Contractor

LTPP Western Regional Office

Regional Support Contractor

FIGURE 2.5. General structure of the LTPP organization during the FHWA-LTPP years (1992–present).
2: MANAGEMENT OF THE LTPP PROGRAM    23

•	 LTPP customer support functions were transitioned

to the FHWA-LTPP Team and FHWA’s General

Administration Support Contractor in 2006. 

•	 Development, refinement, and assessment of traffic

data collection activities were not formally incorporated into the contract until 1997, when the second 

FHWA-LTPP Technical Support Services Contract 

was awarded.

•	 As noted earlier, FHWAentered into a contract with

SHRP to, among other things, retain the services of 

the original four SHRP-LTPP regional engineers for 

a period of 15 months, from July 1, 1992, to September 20, 1993. At the end of that contract, the functions of the LTPP regional engineers were 

incorporated into the 1992 FHWA-LTPP Technical 

Assistance Contract, and they remained in place 

until the award of the 2002 FHWA-LTPP Technical 

Support Services Contract. 

•	 Assistance in relocating database equipment to

FHWA. Prior to 2011, responsibility for housing the 

computer hardware for the LTPP program’s IMS 

and databases remained with the Technical Assistance/Support Services contracts. As discussed in 

chapter 8, in 2011, this equipment was secured at 

FHWA’s highway research center, and the support 

contract retained responsibility for the production 

databases.

Regional Support Contractor Responsibil

The first regional office contracts under FHWA management were issued in May 1992 for a 4-year period 

during the transition of the LTPP program from SHRP 

to FHWA. As the contracts were ending, they were readvertised and awarded for additional 5-year periods 

in 1996, 2001, 2006, and 2011 (appendix B). 

The objective of the LTPP regional contracts is to provide technical services in support of the development 

and conduct of LTPP studies, including all data collection, data processing, and data quality activities for LTPP 

project sections within each region’s geographical 

boundaries, as previously defined under SHRP. Not only 

are the regional contractors responsible for day-to-day 

operations and maintaining a high level of data quality, 

but they play an important part in sustaining the program through their active coordination with the highway 

and in the development of new IMS policies, 

procedures, documentation, and reports; assisting in tracking the status of new and existing 

test sections.

– Ensuring that status changes are properly 

recorded in the database, evaluating the LTPP 

database as development continues, and providing recommendations for enhancements and 

improvements.

•	 Providing technical support in several areas: review

and assessment of LTPP experimental designs and 

status, general planning and coordination of the 

experiments, special needs that arise, and LTPP 

regional field operations. The contract also has provided for periodic assessments of the LTPP program 

and for the services of the four LTPP regional offices.

•	 Providing general support to FHWA for the maintenance and operation of the LTPP database and its

customers. Specific items have included housing, 

staffing, and maintaining the database hardware 

and software operations and providing general 

technical support to LTPP participants and, later, 

customers, developing software coding, developing 

hardware specifications, periodically updating the 

Data User’s Guide,5

 evaluating new software or software upgrades, and periodically releasing LTPP 

data to the public.

•	 Coordinating activities with other LTPP contractors, FHWA, participating States and Canadian 

Provinces, and LTPP customers as required.

•	 Providing technical support services on other special projects.

The 1992 LTPP Technical Assistance Contract was in 

place until 1997. It was re-advertised and awarded by 

FHWA in 1997, 2002, and 2009. The name of the contract changed to LTPP Technical Support Services 

Contract or TSSC in 1997 and remains as such today. 

Other historical facts with regard to the objectives for 

the LTPP Technical Assistance and Technical Support 

Services contracts include the following:

•	 Maintenance and operation of the LTPP database

and support for its customers were formally incorporated into the contract in 1993, a year after FHWA 

awarded the initial contract.
24    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

agencies. Specific activities that have been required 

under these contracts are listed below:

•	 Working with participating highway agencies to

recruit test sections, oversee and document SPS 

test section construction, and assemble required 

data (inventory, design details, traffic, construction, 

maintenance, rehabilitation, environment, and skid 

resistance).

•	 Conducting tests and collecting field data, including

periodic deflection testing, profile testing, manual

distress surveys by accredited raters, Seasonal Monitoring Program measurements, and automated 

weather station data collection. Providing support 

for traffic, maintenance, and rehabilitation data collection by the highway agencies; materials sampling 

and testing by the highway agencies and other LTPP 

contractors; and ensuring the uniformity and consistency of the data they collect.

•	 Managing the data handling and database including

processing data for input into the LTPP database, and 

implementing data QC processes, including checks 

and correction of errors, data uploads, database system 

management, and response to data quality concerns.

•	 Developing QC/QA procedures, including implementation of written QC programs, cooperation with 

and participation in the LTPP QA review program, 

and development of biannual work plans addressing 

the quantity and frequency of data to be collected as 

well as quantities of that data to reach QC Level E, the 

highest assigned quality level (see chapter 9 for a 

description of the database QC levels and checks).

•	 Assisting in coordination and communication,

including: 

– Reviewing and commenting on LTPP documents 

and proposed activities.

– Cooperating and coordinating with other LTPP 

participants.

– Participating in meetings, conferences, and 

workshops.

– Hosting regional LTPP meetings (until the early 

2000s).

– In later contracts, developing and maintaining 

up-to-date regional operations Web sites.

•	 Maintaining and repairing government-furnished

equipment; establishing and implementing comprehensive equipment preventive maintenance programs, calibrations, and checks to ensure equipment 

meets operating standards; and providing secured 

storage space for the equipment.

•	 Carrying out other miscellaneous LTPP program

support activities on an as-needed basis such as special data collection and testing, special database 

management, computer software development, and 

technical services.

•	 Collecting additional data to support other FHWA

studies, as needed.

Other Contractor Responsibil

As SHRP had done earlier, FHWA has awarded other 

major LTPP contracts (appendix B) to perform the 

following activities: 

•	 Collecting material samples and testing these samples (Materials Sampling and Test Contracts).

•	 Overhauling or providing new equipmentfor FWDs

and high-speed profilers (Equipment Contracts). 

•	 Providing a permanent, high-resolution record of

the pavement condition for the entire length and 

width of each LTPP test section (Photographic Distress Contract).

•	 Analyzing data collected at LTPP test sections to

answer specific pavement issues (Data Analysis 

Contracts). 

In addition, other contracts have been awarded by 

FHWA to further meet the goal and objectives of the 

LTPP program. These contracts provided or are providing the following services:

•	 Providing onsite administrative support (General

Administration Support Contract).

•	 Maintaining a facility to store LTPP material samples (Materials Reference Library Contract).

•	 Developing and distributing LTPP products to the

highway community (LTPP Products Contracts).

•	 Determining layer thickness oftest sections and collecting ground penetrating radar data (Determining 

LayerThicknesses Using Ground PenetratingRadar

Contract).

•	 Performing video inspections of edge drains for

select SPS projects (Video Edge Drain Inspections 

Contract).
2: MANAGEMENT OF THE LTPP PROGRAM    25

•	 Collecting high-quality traffic data at select SPS

projects (LTPP SPS Traffic Data Collection PooledFund Study Contracts).

•	 Improving the FWD calibration procedures (FWD

Calibration Center and Operational Improvements 

Pooled-Fund Study Contract).

•	 Improving the level ofintegrity for ride quality measurements by developing calibration processes and 

verification procedures (Improving the Quality of 

Pavement Profiler Measurement Pooled-Fund Study 

Contract).

•	 Examining the effects that multiple freeze-thaw

events versus deep frost penetration has on pavement performance (Effect of Multiple Freeze-Thaw 

Versus Deep Frost Penetration on Pavement Performance Pooled-Fund Study Contract).

•	 Developing an automated pavement distress analysis system (Automated Distress Analysis for Pavements Contract).

More information for each of these contracts is discussed in appendix B.

Expert Peer Review Grou

As noted earlier, FHWA entered into a contract with 

SHRP to continue to provide the peer-review functions of the LTPP Pavement Performance Advisory 

Committee and its supporting ETGs for a 15-month

period ending September 20, 1993. Subsequently, the 

FHWA entered into a direct contract with TRB to 

provide formal peer review regarding LTPP program 

matters. This contract has been renewed throughout 

the life of the LTPP program. 

Once SHRP ended in 1992, the Pavement Performance Advisory Committee provided its counsel to 

FHWA and AASHTO until 1995, when the committee 

was retired. The TRB Long-Term Pavement Performance Committee (LCOM) was then established to provide advice on LTPP’s program planning and operations, 

review progress, and coordinate work conducted by 

variousETGsubcommittees onspecific technicalissues.

Thus, LCOM became the second of two committees of

the National Research Council to provide advice pertaining to the LTPP studies. The charge to LCOM by 

TRB is as follows:

This committee, acting through the National Research 

Council, will advise the Federal Highway Administration (FHWA) and the American Association of State 

Highway and Transportation Officials (AASHTO) on 

the planning and execution of the Long-Term Pavement 

Performance (LTPP) studies. The LTPP studies are a set 

of operational activities consisting of compiling and analyzing data that is being collected on more than 2,500 

in-service pavements in the United States and Canada. 

The principal objective of this data collection and analysis is to further the understanding of how and why pavements deteriorate when subjected to traffic loadings and 

environmental conditions. Data collection and analysis 

began in 1987 and will continue beyond 2013 for a substantial number of test sections that are still providing 

valuable data. The program is also adding test sections to 

investigate the performance of warm-mix asphalt and 

other pavement topics. The committee will prepare reports, including letter reports, containing the committee’s evaluations and suggested mechanisms to enhance 

the utility to the states of the studies’ outcomes.6

This charge is in line with the objective established 

under FHWA’s contract with TRB, which is to continue to conduct and document a program to assist in 

the guidance of current and future activities related 

to the conduct and operation of LTPP data collection, 

analysis, product development, delivery, coordination, evaluation, and communication activities. Furthermore, the contract stipulates that accomplishing 

this objective is the responsibility of LCOM. This 

group convenes twice a year to develop and provide 

strategic recommendations that assist in the guidance 

of current and future activities related to the conduct 

and operation of the LTPP program (figure 2.6). These 

recommendations are sent in the form of a letter 

report to the FHWA Administrator and AASHTO 

Executive Director after each meeting.

As was the case with the TRB Pavement Performance Advisory Committee, various subcommittees or 

ETGs were formed to address specific program technical issues in support of LCOM. These groups enlisted 

experts from highway agencies, industry, academia, 

and FHWA. Through 2006, five ETGs provided support to LCOM:

•	 LTPP Automated Distress Identification ETG.

•	 LTPP Materials Data Collection and Analysis ETG.

•	 LTPP Data Analysis ETG.

•	 LTPP Database Development and Operations ETG.

•	 LTPP Traffic Data Collection and Analysis ETG.
26    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The scope and membership of the 

ETGs are described in appendix A.

In addition to these ETGs, two

subcommittees served LCOM. The 

Subcommittee for Product Development and Delivery was established in 

1999 to define a future course for the 

LTPP program to maximize its outcomes and products (chapter 10).7

The Program Improvement Subcommittee, composed of selected members from LCOM, was established in 

1997 to review and oversee FHWA’s 

implementation of the results of the 

1996 Program Assessment—a formal 

evaluation of the program’s achievements in relation to its goal, objectives, and future direction.8 Activities 

identified as a result of that assessment, which became part of the subcommittee’s purview, included the 

following: 

•	 Clearing data backlog.

•	 Addressing missing data.

•	 Classifying test sections.

•	 Adjusting schedules for monitoring.

•	 Formulating analysis and product development

plans.

•	 Implementing data studies and preliminary analyses.

This subcommittee ended in 1999, when the program 

improvements were well underway.

In 2006, as a direct result of the budget constraints 

imposed on the LTPP program by the 2005 highway 

legislation (Safe, Accountable, Flexible, Efficient 

Transportation Equity Act: A Legacy for Users), the 

number of ETGs providing support to LCOM was

reduced to two. The TRB ETG on LTPP Traffic Data

Collection and Analysis was continued, and a multipurpose TRB ETG on LTPP Special Activities was created that assumed many of the technical functions of

the ETGs that were discontinued.

Between 2006 and 2013, LCOM, with the support of 

the Traffic Data Collection and Analysis and Special 

Activities ETGs, provided the formal peer review functions for all LTPP-related activities. In 2013, the Traffic 

ETG was retired, and its functions were assigned to the

Special Activities ETG.

COMMUNICATIO

AND O

The LTPP program’s longevity and success is due to 

the open dialogue and constant feedback that has been 

in practice since the SHRP years. The planners of the 

program had the foresight to know that clear communication and a well-coordinated effort with many people and organizations would be required to achieve the 

goal and objectives of such a detailed and grand 

research program. The communication and coordination practices of the LTPP program have distributed 

important information about the program, and allowed 

a feedback mechanism for the program’s stakeholders, 

partners, and data users to share their input to improve 

the research being conducted.

Figure 2.6. LTPP Committee meeting held in Washington, DC, on 

2013. Left to right, clockwise: Randy Iwasaki (Contra Costa Transport

Authority), Gary Hoffman (Pennsylvania Asphalt Pavement Association),

Jorge Pagán-Ortiz (FHWA), Pat Hu (Office of Secretary of Transportation

Larry Wiser (LTPP Program), Aramis López (LTPP Program), Olga Selezne

(Applied Research Associates, Inc.), William Temple, Chair (Concret

Aggregates Association of Louisiana), and Robert Raab (

© Transportation Research Board, www.trb.org
2: MANAGEMENT OF THE LTPP PROGRAM    27

Communication With Stakeholders

Disseminating information to stakeholders has been a 

high priority for the LTPP program. The program has 

used different communication mechanisms throughout the years, from holding national meetings and 

workshops, to meeting with individual highway agencies, to participating in agency-sponsored LTPP meetings. In addition, reports, articles, newsletters, and 

other publications have been made available. The 

methods used to communicate with LTPP stakeholders have changed over the years with changes in technology and resources.

Meetings

Communicating the benefits of the LTPP program and 

listening to stakeholder input concerning its plans and 

progress have been of paramount importance to SHRP 

and FHWA. A key piece of this communication has 

involved participating in national and regional conferences over the years. Highlights include many different 

events at the annual TRB meetings in Washington, DC, 

such as the LTPP State Coordinators’ Meeting, International Coordinators’ Meeting, LTPP Technical Session, and presentations during other technical sessions. 

The LTPP sessions held each year during the TRB 

annual meeting discuss different topics relating to the 

program and often feature presentations from a highway agency perspective or from a university that has 

used LTPP data in its curriculum. 

In addition to participating in the 

TRB annual meeting, the LTPP program has held national meetings 

through the years with stakeholders to 

discuss data collection and monitoring 

issues and provide an update on the 

program’s progress and plans. These 

national meetings include the Colorado 

Mid-Course Assessment Meeting in 

1990, California LTPP National Meeting in 1996, Rhode Island LTPP Specific Pavement Study Workshop in 

2000, LTPP Pavement Analysis Forum 

in 2010, and many others. The LTPP 

program has also been represented in 

many AASHTO meetings, including 

those of the Standing Committee on 

Research, Research Advisory Committee, and Subcommittee on Materials. 

Coordination meetings have been held with individual highway agencies since the program began. The 

LTPP program staff and its contractors often meet 

with representatives of State and Provincial agencies 

and FHWA Division Offices, for example, to discuss 

data collection, equipment installation, and traffic control issues, as well as other LTPP-related issues specific 

to the highway agency. In the early years of the program, these coordination meetings focused on recruitment and nomination of LTPP test sections. In the last 

several years, the agency visits have focused on plans to 

establish two new SPS experiments (warm-mix asphalt 

and pavement preservation).

The LTPP regional support contractors held meetings for many years to bring together the LTPP Coordinators from the highway agencies within their respective 

regions to discuss progress within their agencies and to 

hear presentations on big-picture items within the LTPP 

program. These meetings were phased out in the early 

2000s as program funds became more limited and outof-state travel became more difficult for highway agency 

personnel. Later, the LTPP program began to hold faceto-face meetings at State/Provincial highway agency 

offices with agency staff, regional contractors, and LTPP 

program staff. Figure 2.7 shows a meeting held in 2011 

with the Connecticut Department of Transportation.

FIGURE 2.7. Connecticut Department of Transportation (CT DOT) staff meet

with the LTPP program and regional support contractor staff. Pictured from

left to right: Edgardo Block, Thomas Harley, Anne-Marie McDonnell (LTPP

State Coordinator), Ravi Chandran (CT DOT); Frank Meyer (LTPP North

Atlantic Region); Aramis López (LTPP Program); Amy Jackson-Grove

(Connecticut FHWA Division Office); Jack Springer (LTPP Program); and

Basel Abukhater (LTPP North Atlantic Region).
28    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

LTPP meetings held by the highway agencies have 

helped to sustain agency commitment to the program. 

The meetings have kept agency staff informed and 

encouraged fruitful exchanges between agency staff 

and the program. For example, in the State of Texas, 

each district office met every 12 to 18 months with 

someone from the LTPP program staff, regional support contractors, and other contractors to learn more 

about the program and why it is important at the State 

and national levels (see sidebar). Because the meetings 

kept the State’s field staff informed about the test sections in their respective districts, the staff understood 

why it is necessary to monitor the test sections until 

the end of their design life, without jeopardizing the 

safety of the driving public. State efforts like the Texas 

meetings possibly allowed many LTPP test sections to 

remain in the program for continued monitoring longer than they otherwise would have. 

Some highway agencies have held their 

own LTPP meetings to discuss the importance of the LTPP program with their field 

staff. These meetings proved to be beneficial to both the highway agencies and the 

program. For example, in the mid-1990s, 

the LTPP State Coordinator for the Texas 

Department of Transportation met every 

12 to 18 months with the 25 district offices 

to discuss Texas’ role in and commitment 

to the LTPP program. These meetings 

brought together the district contacts, 

LTPP program staff, regional support 

contractors, other contractors, and the 

FHWA Division Office staff. Recognizing 

the benefits of national pavement research, Texas established more LTPP test 

sections than any other highway agency 

and continues to be an active partner in 

the program.

Highway Agency 

Achieving Real Results on Re

LTPP team members also participate in a variety of 

other national meetings, including the annual North 

American Travel Monitoring Exhibition and Conference, TRB’s biannual Data Analysis Working Group,

and the annual Road Profiler User Group and Falling

Weight Deflectometer User Group meetings. The participation of team members in these meetings allows 

them to collaborate with others on technical issues, 

keeping the program abreast of the latest in data collection and information technologies, and to offer face-toface assistance to highway agencies.

The LTPP Web site and, in more recent years, Web 

conferencing technology have enabled a much larger 

number of people to participate in direct learning about 

the program and database and to do so with more 

frequency than face-to-face conferences would allow. 

The technology also enables the LTPP Team to benefit 

from a broader range of stakeholder feedback about the 
2: MANAGEMENT OF THE LTPP PROGRAM    29

program and its products and a wider collaborative network as the program moves into the future. The first 

LTPP Webinar was held in September 2011 to give an 

overview of the program (see sidebar). Recorded Webinars are available on the LTPP Web site.

Publications

Special reports, brochures, exhibits, and various print 

and Web documents have been used to relay program 

information to wider audiences. Examples of reports 

include:

•	 The Long-Term Pavement Performance Program 

Roadmap: A Strategic Plan.9

•	 LTPP: The Next Decade.10,11

•	 An Investment Benefiting America’s Highways: 

The Long-Term Pavement Performance Program.12

•	 LTPP Product Plan.13

•	 LTPP and the 2002 Pavement Design Guide.14

•	 LTPP Beyond FY 2009: What Needs to Be Done?15

•	 Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009.16,17

In addition, the program has published articles in highway publications, such as Focus, TRB’s TR News, 

Research & Technology Transporter, Roads & Bridges, 

Public Roads, and EDC News to present important 

pavement engineering issues to the broader community. The LTPP Web pages bring LTPP research and 

products directly to data users and also serve as an 

archive for program activities. The Web pages carry 

the LTPP Newsletter,18 communicating directly with 

stakeholders, the Year in Review articles that summarize activities and progress in the program, Key Findings reports that summarize LTPP data analysis 

projects,19,20 and hundreds of research reports that provide the findings from different studies.

Communication Within the Progra

While the success of the LTPP program is largely 

attributable to the partnerships that exist between the 

program and the highway engineering community, 

internal communication between the LTPP program 

staff and its supporting contractors has also played a 

vitally important role in the program’s achievements. 

LTPP management holds regular team meetings and 

teleconferences to maintain clear communication and 

Communicat

Stake

The first LTPP Webinar was held September 2011 

to provide more direct contact and interaction 

between the LTPP Team and program stakeholders. The team conducts informational Webinars, 

usually bimonthly, that are open to highway agencies, pavement industries, contractors, vendors, 

university professors and students, consultants, 

metropolitan planning organizations, and others 

with an interest in the program. Topics range from 

the general (future plans, program updates) to 

the very specific (demonstration of the dynamic 

modulus software, how traffic data are used) and 

include LTPP products and case studies.

coordinate program activities with the FHWA-LTPP 

staff and contractors both onsite at FHWA’s highway 

research center and offsite. These activities include a 

weekly staff meeting attended by FHWA-LTPP Team 

members, onsite contractors, and key offsite contractors, as well as personnel from other FHWA offices on 

occasion. Meetings feature briefings on the progress of 

program activities, discussion of pending and future 

issues, and planning and review of future LTPP Newsletter articles and Webinars.

As the LTPP technical support services contractor 

and the regional support contractors are primarily 

responsible for the program’s data collection and processing, data QC/QA, equipment maintenance, and 
30    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

other field activities, it has been particularly important 

to hold regular meetings with them to ensure consistency in various procedures and technical issues 

throughout the four LTPP regions. The FHWA-LTPP 

staff holds a 2-day formal meeting twice a year with 

the program’s core contractors to discuss many of the 

program’s large-scope issues and identify actions to 

resolve these issues (figure 2.8). Earlier in the program, 

these meetings were held quarterly. Another critical 

and very important communication tool used to ensure 

consistency among the LTPP regions is the use of 

program directives. Directives provide written instructions to the regions for collecting, processing, and 

managing LTPP data, equipment, and software. 

In addition, the FHWA-LTPP staff holds routine 

meetings and teleconferences with the technical and 

regional support contractors to discuss issues specific 

to various program areas, such as distress, deflection,

profile, traffic, automated weather stations, the Seasonal Monitoring Program, and the IMS. Targeted 

meetings and teleconferences are also held to discuss 

special projects. In the past, these have included projects such as the Materials Action Plan, the database, 

and forensic studies, as well as FHWA pooled-fund 

studies that involve the LTPP program.

SUMMA

Managing the LTPP program presents a number of 

challenges—budgetary, administrative, and technical. 

The program spans two countries, requires the cooperation of 62 transportation agencies, and involves the 

concerns of numerous stakeholders within the highway community. Implementation challenges have been 

met with the expert advice and support of professional 

groups, industry organizations, and research institutions through the National Research Council advisory 

committees and related expert task groups. A significant management challenge arose when SHRP ended 

in 1992 and the objectives of long-term pavement performance monitoring had not yet been fulfilled. 

FHWA’s commitment to the program and assumption 

of its management enabled it to continue, and the management transition from SHRP to FHWA in 1992 was 

carefully planned and smoothly executed.

Throughout the program, a rigorous emphasis on 

quality has been maintained. To achieve a consistently 

high level of data quality across the program required 

planning and coordinating the activities of the many 

technical contractors who have served the program in 

various capacities, and addressing the concerns of the 

Figure 2.8. LTPP program staff and core contractors meet to discuss the status of different program activi

including data collection, database management and development, and future plans of the program. Front Row (left to 

right): William Bellinger, Kevin Senn, Larry Wiser, Deborah Walker, Miriam Pitz, Basel Abukhater, Jane Jiang, Jer

Daleiden. Second Row: Jack Springer, Tommy Clark, Gary Elkins, Sarah Tarpgaard, Frank Meyer. Third Row: Aramis Lóp

Jason Puccinelli, Gabe Cimini, Jonathan Groeger, Mark Gardner (2011 in Austin, Texas
2: MANAGEMENT OF THE LTPP PROGRAM    31

highway agencies. Consistent and constant communication and coordination with stakeholders and within the 

program are vital to meeting the program’s objectives.

As the program grew, management had to adapt to 

rapid technological changes in pavement monitoring and 

data management while also facing painful reductions in 

Federal funding (discussed in chapter 4) that have jeopardized the program’s completion. Nonetheless, the 

program has weathered these difficulties with the wisdom and guidance of the program managers, who are 

introduced in the following pages, and the support and 

commitment of its partners, whose contributions are 

acknowledged in chapter 3. On this solid foundation, the 

LTPP program is prepared to address the pavement 

research needs and technologies of the future.

REFERE

1. SHRP: Paving the Way for Tomorrow’s Highways 

(Video VH-120). Federal Highway Administration, 

McLean, VA, 1989. https://www.youtube.com/

watch?v=UCPYBs6raeo.

2. Strategic Highway Research Program Research Plans. 

Final Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986.

3. K. R. Maser. Ground Penetrating Radar Surveys to 

Characterize Pavement Layer Thickness Variations at 

GPS Sites (SHRP-P-397). Strategic Highway Research 

Program National Research Council, Washington, DC, 

1994. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-P-397.pdf.

4. N. F. Hawks. “LTPP at Year Five.” TR News, No. 158 

(January 1992), pp. 14–17, 32. http://trid.trb.org/

view/1992/C/365970.

5. Long-Term Pavement Performance Information 

Management System: Pavement Performance Database 

User Reference Guide (FHWA-RD-03-088). Federal 

Highway Administration, Washington, DC, 2003. 

www.fhwa.dot.gov/pavement/pub_details.cfm?id=96.

 6. “Project Information.” Web page. http://www8.

nationalacademies.org/cp/projectview.

aspx?key=49564.

7. A. L. Abbott. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 7), July 13, 1999, 

p. 5. http://onlinepubs.trb.org/Onlinepubs/sp/ltpp_

letter_7.pdf.

8. LTPP Program Focus: The Assessment: Final Summary 

Report. Federal Highway Administration, McLean, VA, 

March 1997. Available at LTPP InfoPave Web site.

9. The Long-Term Pavement Performance Program: 

Strategic Plan (FHWA-RD-95-200). Federal Highway 

Administration, McLean, VA. September 1995. 

http://isddc.dot.gov/OLPFiles/FHWA/014731.pdf.

10. C. J. Churilla. “LTPP: The Next Decade.” Public Roads,

vol. 62, no.1 (July/August 1998). https://www.fhwa.dot.

gov/publications/publicroads/98julaug/ltpp.cfm.

11. “LTPP: The Next Decade” Web page. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/decade.cfm.

12. An Investment Benefiting America’s Highways: 

The Long-Term Pavement Performance Program

(FHWA-RD-01-094). Federal Highway Administration, 

McLean, VA, n.d. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/01094/01094.pdf.

13. LTPP Product Plan (FHWA-RD-01-086). Federal 

Highway Administration, McLean, VA, n.d. http://

www.infopave.com/InfoPave_Repository/Reports/

C40/C40_20/01086.pdf.

	 14.	LTPP and the 2002 Pavement Design Guide (FHWARD-00-129). Federal Highway Administration, McLean, 

VA, n.d. http://www.infopave.com/InfoPave_

Repository/Reports/C40/C40_20/00129.pdf.

15. LTPP Beyond FY 2009: What Needs to Be Done?

(FHWA-HRT-09-052). Federal Highway 

Administration, McLean, VA, 2009. http://www.

infopave.com/InfoPave_Repository/Reports/C40/

C40_20/09052.pdf.

16. Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009 (FHWAHRT-10-071). Federal Highway Administration, 

McLean, VA, 2010. http://www.infopave.com/

InfoPave_Repository/Reports/C40/C40_20/10071.pdf.

17. Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009 (FHWAHRT-10-072). Federal Highway Administration, 

McLean, VA, 2010. http://www.infopave.com/

InfoPave_Repository/Reports/C40/C40_20/10072.pdf. 

18. “LTPP Newsletter Home.” Web page. http://www.fhwa.

dot.gov/publications/ltppnews/.

19. Key Findings From LTPP Analysis: 1990–1999 

(FHWA-RD-00-085). Federal Highway 

Administration, McLean, VA, 2000. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/key.cfm.

20. Key Findings From LTPP Analysis: 2000–2003 

(FHWA-HRT-04-032). Federal Highway 

Administration, McLean, VA, 2003. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/reports/04032/04032.pdf.
NEIL F. HAWK

SHRP-LTPP Program Manager, 

1987–1992

Neil Hawks, P.E., recently retired 

from the Transportation Research 

Board (TRB) of the National Academies, where he was the Director 

of the second Strategic Highway Research Program 

(SHRP 2). SHRP 2 was a concentrated, focused program seeking to make strategic advances that will 

improve the safety, planning, travel-time reliability, 

and renewal of America’s highway system.

Mr. Hawks joined the staff of the National Academies in 1982. From 1982 to 1987, he was the TRB Engineer of Soils, Geology and Foundations. From 1987

through 1992, Mr. Hawks was with the first Strategic 

Highway Research Program. At SHRP, he directed the 

Long-Term Pavement Performance Program and initiated the SHRP Asphalt Research Program. In 1992, he 

rejoined TRB as the Director of Special Programs. In 

this role, he provided direction to the five TRB Innovations Deserving Exploratory Analysis (IDEA) programs and to committees advising on the conduct of 

research and technology implementation.

Prior to joining TRB, Mr. Hawks worked for the 

Pennsylvania Department of Transportation for 14 

years in geotechnical engineering, highway design, and 

construction.

He is a graduate of Columbia University and a registered professional engineer. 

LEADERS OF

LTPP PROG

T. PAUL TE

LTPP Division Director, 1991–1995

Paul Teng, P. E., started his highway engineering career conducting 

paving materials research while 

pursuing a graduate degree at the 

University of Mississippi in 1964. 

Prior to joining the Federal Highway Administration 

(FHWA) in 1981, he held a range of engineering positions with the Mississippi State Highway Department, 

where he was the Department’s Research and Development Division Engineer from 1974 to 1981. 

At FHWA, Mr. Teng was assigned to a number of 

engineering, operations, and research and development 

positions and worked with industries, universities, 

trade associations, State highway agencies, and FHWA 

Division Offices on pavement engineering, rehabilitation, and management practices. In 1991, he established 

the Long-Term Pavement Performance Division, and 

was responsible for the transition of SHRP activities 

from the National Research Council to FHWA in 1992. 

He was selected into the U.S. Senior Executive Service 

and appointed as FHWA’s Chief Pavement Engineer in 

1994. In 1999, Mr. Teng became Director, Office of Infrastructure Research and Development.

He has received numerous commendations and 

awards including the FHWA Administrator’s Award for 

Superior Achievement and the Secretary of Transportation’s Meritorious Achievement Award. As a professional engineer, Mr. Teng has authored many authoritative 

technical publications in the highway pavement and 

materials areas. He retired from FHWA in 2005. 

32    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
CHARLES J. CH

LTPP Team Leader, 1995–1999

Charles Churilla, P.E., has had a 

professional career of more than 

40 years in the materials, geotechnical, and pavement engineering 

disciplines. During those years he 

worked for the Pennsylvania Department of Transportation, Federal Highway Administration (FHWA), and 

as a Principal Engineer for Applied Research Associates, Inc. He was the lead in the development of the 

FHWA Highways for LIFE concept and saw it through 

to fruition. He also led the FHWA Infrastructure Team 

in the development of the first-ever Infrastructure 

Research and Technology Plan. Mr. Churilla led the 

Long-Term Pavement Performance (LTPP) program 

from 1995 to 1999. Working with other FHWA headquarters and field offices he was instrumental in beginning the development and delivery of the LTPP 

technical products. He was responsible for the development and implementation of FHWA’s Full Scale 

Accelerated Testing Program using the ALF (accelerated loading facility) pavement testing machine.

Mr. Churilla was a member of the National Academy of Sciences, the American Association of State 

Highway Transportation Officials, and the Transportation Research Board. He is a registered professional 

engineer and an Honorary Member of Chi Epsilon, a 

civil engineering fraternity.

MONTE SY

LTPP Team Leader, 1999–2001

Monte Symons, P.E., received his 

B.S. and M.S. degrees in Civil Engineering from the University of 

Illinois and joined the Federal 

Highway Administration (FHWA) 

in 1975. In his career with FHWA, Mr. Symons served as 

Geotechnical Engineer in the Federal Lands Highway

Program, Materials and Research Advisor to the Kuwait 

Ministry of Public Works Motorway System, Regional 

Pavement and Materials Engineer in Region 5, Team 

Leader for the Long-Term Pavement Performance 

research program, and Team Leader of the Infrastructure Team in the Midwest Resource Center. He finished 

his FHWA career as Team Leader for the National 

Pavement and Materials Resource Center Team.

Mr. Symons’ accomplishments included completing 

over 200 reports on pavement condition and design as 

well as subsurface reports for landslides and bridge foundations; developing and implementing the initial roadway inventory program for the U.S. National Park Service; 

assisting State highway agencies with pavement and 

materials issues; directing research programs to improve 

pavement performance and design life; and leading 

efforts to implement the latest pavement technologies.

After retiring from FHWA in 2005, he joined 

Auburn University as Director of the Airport Asphalt 

Pavement Technology Program, a 5-year, $4.8 million 

effort that completed 19 projects. He is currently the 

CEO of Montista Consulting LLC.

ARAMIS LÓP

LTPP Team Leader, 2001–Present 

Aramis López, P.E., was a Civil 

Engineer with the Puerto Rico 

Department of Transportation 

before joining the Federal Highway Administration (FHWA) in 

1978 as a participant in the FHWA Highway Engineer 

Training Program. Mr. López has held several different 

engineering positions within FHWA in the areas of 

construction, design, research, and management in the 

Oregon, California, Texas, and Louisiana FHWA Division Offices, and at headquarters. In 1991, he was 

assigned to assist in the transition of the Long-Term 

Pavement Performance (LTPP) program from the Strategic Highway Research Program to FHWA. He is currently the Team Leader of the LTPP program in the 

Office of Infrastructure Research and Development at 

the Turner-Fairbank Highway Research Center.

Mr. López earned a Bachelor’s of Science in Civil 

Engineering from the University of Puerto Rico at 

Mayagüez. He has received numerous awards and commendations including the FHWA Administrator’s 

Award for Superior Achievement for his vision and 

leadership of the LTPP program, the U.S. Department 

of Transportation Secretary’s Volunteer Service Award, 

and the U. S. Department of Transportation Excellence 

in Teamwork Award. His leadership and commitment 

to pavement research and the LTPP program since 1991 

has produced the most comprehensive pavement performance database in the world. 

LEADERS OF THE LTPP PROGRAM    33
34    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Partnerships with the highway agencies, academia, and industry not only 

keep the LTPP program relevant and responsive, but also enable it 

to draw on the highest levels of technical and managerial expertise.

Data Collection

Data Analysis

Product Development and Delivery

AASHTO

Task Force on SHRP Implementation

NCHRP Joint Task Force on Pavements 

Subcommittee on Materials 

Funding

SHRP and FH

Program Management 

Data Management 

and Communication

STATES a

PROVINCE

Test Sections

Implementation

NRC/TR

LTPP Committee

LTPP Subcommittees

Expert Task Groups

C-SHRP

Provincial Participation

C-LTPP Study

Funding

© Luis Molinero/Shutterstock.com
3: LTPP PROGRAM PARTNERSHIPS    35

LTPP Program Partnerships

3

Intro

Since the LTPP program began, partnering with the 

highway engineering community has been another 

key to the program’s longevity and success. Even as 

the program was being planned as part of the Strategic Highway Research Program (SHRP), it benefited 

from the international outreach and involvement of 

industry and academia that were integral to the 

SHRP-LTPP planning process.

In particular, the LTPP program depends on the 

cooperative efforts of the American Association of State 

Highway and Transportation Officials (AASHTO), 

the Canadian Strategic Highway Research Program 

(C-SHRP), the highway agencies in the States and 

Provinces, the National Research Council (NRC) through 

SHRP and the Transportation Research Board (TRB), 

Since its inception, the LTPP program has relied on a close working relationship with many organizations 

and individuals. The unique blend of expertise among the partners brings focus to every area of the 

research study. The open and often very candid interaction with the partners has had a positive impact 

on the program’s direction. The dedication and commitment of those in this partnership arrangement 

has strengthened the LTPP program and has supported the program’s efforts to provide resources that 

benefit the highway community. 

the Federal Highway Administration (FHWA), and 

the international highway community. By extension, 

LTPP partners also include the various paving industries, trucking industry, highway user groups, material suppliers, equipment manufacturers, and the 

engineers and researchers who use LTPP research 

results. Each of these partners has played and will 

continue to play a key role in helping the LTPP program achieve its full potential.

The illustration on the facing page represents 

the LTPP program’s primary partners (1987 to the 

present) and their areas of participation, while the 

summaries below describe how the partners contribute to the program.
36    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

“I have had the good fortune to be associated 

with the Long-Term Pavement Performance 

program in various ways since its inception. 

While the extensive database and the many 

products stand out of course, the importance 

of partnerships, direct and indirect or 

implicit, represents both an evolution and 

a legacy of accrued benefits. State, Federal, 

and local agencies and researchers are 

direct beneficiaries. The organizations 

and the individuals involved have gained 

experience and expertise, and the state 

of knowledge and practice has advanced 

substantially. In turn, the LTPP program 

itself can justifiably take pride in the many 

achievements of having more and better 

trained people in the program and in the 

partnerships; as well in the receptiveness 

shown to the needs of the partners. But the 

ultimate beneficiaries are really the public, 

who are served by better and safer roads, 

by skilled people, and by good management 

of the assets.”

 Ralph Haas 

The Norman W Mcleod Engineering Professor 

and Distinguished Professor Emeritus 

University of Waterloo

Meeting of the TRB Expert Task Group on LTPP Special

Activities held in Washington, DC, on October 15, 201

From bottom left, clockwise: Dean Wolf (Applied Resear

Associates, Inc.), Rebecca McDaniel, Chair (Purdu

University), Robert Raab (TRB), Rick Reel (Florida DO

Deborah Walker (LTPP Program ), Gary Taylor (Professiona

Engineer, Michigan), Olga Selezneva (Applied Research

Associates, Inc.), Barbara Ostrom (AMEC), and Catherine

Lawson (State University at New Yo

© Transportation Research Board, www.trb.org
3: LTPP PROGRAM PARTNERSHIPS    37

AMERICAN ASSOCIATION OF S

HIGHWAY and TRANSPORTA

OFFICIALS

AASHTO is the national representative of State transportation agencies in the United States. Through funding from participating agencies, AASHTO lobbies the 

U.S. Congress on transportation-related issues, conducts national and regional meetings with State representatives on transportation-related topics, publishes 

materials and testing specifications and standards of 

practice, and provides reference material services and 

accreditation to materials testing laboratories. 

AASHTO has played a critical role in the LTPP program from its start. From working with States to establish the LTPP program using Federal-Aid highway 

funds to recruiting test sections to the adoption of 

LTPP-developed methods, procedures, and guidelines 

as standards for pavement engineering, AASHTO has 

provided the collective leadership for many of the 

program’s successes to date. For example, in 1996, 

AASHTO passed a Memorandum of Understanding on 

the LTPP Program, to help in obtaining the remaining 

Specific Pavement Study (SPS) test sections (figure 3.1). 

It was not until an AASHTO resolution was passed in 

April 1998 seeking the States’ help that the effort began 

in earnest to resolve LTPP data deficiencies identified 

during a 1996 Program Assessment.1

 Likewise, in 2003, 

LTPP management worked with the AASHTO Subcommittee on Materials to address issues related to the 

resilient modulus for unbound materials. In addition, 

through its Standing Committee on Research, AASHTO 

provided $13.83 million to the LTPP program through 

the National Cooperative Highway Research Program 

(NCHRP) to supplement data collection and data 

analysis activities during a severe funding shortfall 

(chapter 4). AASHTO was represented on the various 

SHRP planning committees and the Pavement Performance Advisory Committee, and continues to be represented on the LTPP Committee.

CANADIAN STRATEGIC HIG

RESEARCH PROGRAM

Representatives of Canada were involved with SHRP 

and the LTPP program from the earliest planning stages. In the spring of 1985, Transport Canada, the country’s national transportation agency, funded a study to 

explore Canadian involvement in SHRP. Canada’s participation was coordinated by the Roads and Transportation Association of Canada (RTAC) (known as 

“Transportation Association of Canada” since 1990) 

through its Council on Highway and Transportation 

Research and Development. 

RTAC worked closely with AASHTO and SHRP, 

and Provincial officers represented Canada on the 

SHRP Task Force, SHRP Advisory Committee on 

Overview and Integration, and on the SHRP technical 

area advisory committees, including the Advisory 

Committee on Long-Term Pavement Performance 

(appendix A), which developed the initial SHRP-LTPP 

plans. Canada’s highway agencies were also represented in early SHRP workshops in 1985 and 1986, and 

RTAC conducted meetings and a workshop in the fall 

of 1985 involving key highway agency and research 

representatives. In 1986, Canada established its own 

Strategic Highway Research Program—C-SHRP—with 

initial funding of $5 million CAD, with 10 percent of 

the costs covered by the Federal government and the 

balance by the Provinces.2,3

The Canadian approach to highway research included monitoring SHRP research, pursuing technology 

transfer related to SHRP and C-SHRP, and conducting 

two separate research programs: 

•	 Integrated Program—Canadian sites and facilities

were incorporated into the SHRP program, with 

SHRP contractors conducting the testing as in the 

United States. Canadian highway agencies retained 

responsibility for traffic control and coordinating 
38    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Figure 3.1. Memorandum of Understanding for the recruitment of LTPP SPS test se
3: LTPP PROGRAM PARTNERSHIPS    39

site visits. The Provinces were part of LTPP’s North 

Atlantic, North Central, and Western regions, and 

data from 127 sections across the 10 Provinces are 

contained in the LTPP database. As SHRP began operations, RTAC was represented on the SHRP-LTPP 

staff through the loaned staff program; this staff participation continued into the FHWA-LTPP years.

•	 C-LTPP—In 1989, Canada funded a separate, smallscale research program, structured to be compatible 

with and complementary to SHRP-LTPP, to examine factors of particular interest to Canada that were 

not addressed in SHRP. Focused on rehabilitation 

practices, this program consisted of 24 test sites 

with a total of 65 test sections constructed between 

1989 and 1992 to investigate various thicknesses 

and types of asphalt overlays, with particular consideration of frost action and seasonal variations.4

C-LTPP was continued until 2004 and resulted in 

a database and numerous research reports. The 

data and other information for the test sections 

monitored by Canada are available on the LTPP 

InfoPaveTM Web site.

C-SHRP has played a major role in the achievements of 

the LTPP program by providing sponsorship and support for LTPP test sections in Canada, supporting LTPP 

data collection efforts in Canada, participating on the 

Pavement Performance Advisory Committee and LTPP 

Committee, and sponsoring LTPP-related data analysis 

projects. During a period of reduced LTPP program 

funding, C-SHRP contributed $120,000 to cover digitization of distress survey film and also funded an LTPP 

publication. Due to Canada’s close support and coordination, it is the only country other than the United 

States with test section data in the LTPP database.

STATE AND PROVINCIAL HIG

AGENCIE

The LTPP program began as part of SHRP, which was 

a “State’s” initiative, and it included the departments of 

transportation for the 50 States, the District of Columbia, and Puerto Rico. These agencies, along with the 10 

Provincial transportation agencies of Canada, are both 

owners and customers of the program.

As owners, highway agencies have made significant 

investments in the program by investment of funds, 

designating test sites, constructing and monitoring test 

sections, supplying test materials, collecting traffic and 

other data, and providing traffic control. In addition, 

these agencies have optimized the benefits from their 

investment in the LTPP program (and their highway 

networks) by sponsoring and submitting LTPP-related 

NCHRP research problem statements for data analysis, product development, and implementation activities; participating in LTPP-related pooled fund studies; 

sponsoring LTPP-related data analysis with agency 

funds; and participating on AASHTO, TRB, and 

NCHRP committees, expert task groups (ETGs), and 

task forces. Many agencies have also loaned staff to 

work directly with the LTPP program in certain technical areas of the program. These arrangements gave 

the agency detailed insight about the everyday operations of the program and the opportunity to affect 

decisions made at the national level. 

As customers of the program, the highway agencies 

are the primary users of the results garnered and yet to 

be garnered from the program. LTPP data and products 

are a resource for pavement designers, materials engineers, maintenance engineers, traffic forecasters, and 

pavement management engineers. For example, the 

LTPP data will be important to the local and regional 

calibration of the AASHTOWare® Pavement ME Design 

software. In addition, with the ready availability of 

LTPP data via the Standard Data Releases and online 

support (LTPP InfoPave), agencies can more easily 

gain access to the data to address their local and regional pavement information/technology needs. 

The active participation of highway agencies in the 

program was largely driven by their expectation that 

the tools and knowledge that the LTPP program generated would provide answers to issues of importance 

to them. In formal interviews conducted with chief 

engineers in the highway agencies as part of the LTPP 

Program Assessment (chapter 11), the engineers voiced 

the following expectations:

•	 We need to know what maintenance treatments

are effective. What do they cost? When should 

they be used? How much do they extend the life of 

the pavement?
40    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 We need to know what the best rehabilitation

design is for a given road structure. How can we 

minimize the risk of our choice? What are the lifecycle costs?

•	 We need better designs, developed from models

that predict with assurance that the newly built or

reconstructed pavements based on these designs 

will last a specified number of years.

•	 We need dramatic improvements in technology, not

incremental changes.

•	 We need to know what performance trends are discernable from the LTPP data.

•	 We need improvements in WIM technology. We

need to measure equivalent single-axle loads more 

accurately.

The States’ concerns echo strongly those cited in the 

AASHTO Interim Guide for Design of Pavement Structures, known as the “Blue Book,”5

 and the Strategic 

Highway Research Program Research Plans, Final 

Report, known as the “Brown Book,”6 but have a more 

tangible feel. In essence, the agencies want useful engineering tools and an enhanced knowledge base on 

which to base management and engineering decisions—these are their high-priority needs in terms of 

answers from the LTPP program.

To ensure that general program information and 

research results are communicated consistently, each 

of the highway agencies has designated an LTPP State 

Coordinator, who serves as liaison and point of contact 

between the agency and the LTPP program staff. Each 

year during the annual TRB meeting, an LTPP State 

Coordinators’ meeting is held at which the coordinators learn about the status of the program and LTPP 

program staff learn how highway agencies are using 

LTPP data and products at the agency level. Each LTPP 

State Coordinator has been important to the success of 

the LTPP initiative.

NATIONAL RESEARCH COUN

TRANSPORTATION RESEARCH B

As previously discussed, the LTPP program originated 

and operated for 5 years within SHRP, an independent 

unit of the National Research Council. From 1987 to 

1992, SHRP managed the day-to-day operations of the 

LTPP program. Specific activities included development of guidelines for recruiting test sections, testing 

materials, collecting and processing data, establishing 

the database, and orchestrating and coordinating LTPP 

activities. The National Research Council also provided peer advisory committees to the LTPP program 

through SHRP. Later, TRB, a sister entity to SHRP 

under the National Research Council’s umbrella began 

operating several committees that have provided an 

independent forum in which the States, Provinces, 

industry, and academia have contributed input and 

advice on the conduct of LTPP research and implementation activities. 

As part of the partnership with the LTPP program, 

TRB has sponsored special LTPP events. In September 

2010, for example, the LTPP Committee sponsored an 

LTPP Pavement Analysis Forum that brought together 

pavement design, management, preservation, and traffic data experts to update the Strategic Plan for LTPP 

Data Analysis. Jointly planned and implemented by 

FHWA’s LTPP Team and the LTPP Committee, the 

forum was designed to identify, define, and prioritize 

the analytical studies that will produce results that can 

be further developed and combined into products that 

highway agencies can use to help design, build, and 

maintain—on a mechanistic/empirical basis—existing 

and future highways.7

 In addition, many of TRB’s 

research projects, such as NCHRP Project 1-37A 

(Mechanistic-Empirical Pavement Design Guide) and 

NCHRP Project 1-34D (Effects of Subsurface Drainage 

on Performance of Asphalt and Concrete Pavements: 

Further Evaluation and Analysis of LTPP SPS-1 and 

SPS-2 Field Sections), have been strengthened through 

the use of LTPP data.

The work of all of the LTPP advisory committees 

and ETGs exemplifies the dedication of individual 

stakeholders who have offered advice and provided 

guidance to the program. 

The highway agencies have been critical 

to the LTPP program’s achievements 

and will continue to play a pivotal role 

in the future.
3: LTPP PROGRAM PARTNERSHIPS    41

The Asphalt Institute, International Grooving and 

Grinding Association, Asphalt Recycling and Reclaiming Associations).

•	 Manufacturers of paving materials (e.g., National

Stone, Sand, and Gravel Association; Concrete and 

Aggregates Association).

•	 Highway users (e.g., American Automobile Association; American Trucking Associations, Inc.; Roadway Express, Inc.).

The LTPP program has enjoyed a unique partnership 

with the American Society of Civil Engineers (ASCE). 

Since 1998, ASCE and FHWA-LTPP have jointly 

sponsored a series of international contests on LTPP 

Data Analysis to recognize the use of LTPP data by 

university students and professors. The contest is 

designed to encourage university students, professors, and highway department engineers from around 

the world to get involved in using the LTPP database. 

ASCE’s participation is managed by its Task Committee on the Long-Term Pavement Performance Contest, which is a subcommittee of the Highway 

Pavement Committee of ASCE’s Transportation and 

Development Institute.

The contest usually makes awards in four categories (Undergraduate students, Graduate students, 

Partnership, and Challenge) with a theme that changes each year. Prizes have included expense-paid 

attendance at the TRB Annual Meeting, cash awards, 

and publication of winning papers (figure 3.2).8,9,10

FEDERAL HIGHWAY ADMINISTRA

The FHWA has been a prime mover behind the LTPP 

program, from investing in preliminary research in longterm pavement monitoring in 1984, before SHRP-LTPP 

began, through its sponsorship and extension of the 

LTPP program beginning in 1992 and continuing into 

the future. The agency has provided a permanent 

“home” for the program by securing the LTPP Information Management System, performance data, and other 

program products at FHWA’s Turner-Fairbank Highway Research Center, and by continually upgrading the 

software and hardware required for accurate and reliable data collection and management. The FHWA has 

also provided budgetary support to supplement congressional authorizations and in-kind staff and overhead 

throughout much of the LTPP program’s existence.

INDUSTRY, ACADEMIA, PROFESS

ASSOCIATIONS, AND

ORGANIZATIO

From the earliest landmarks in the LTPP program’s 

formative years, a broad range of viewpoints and areas 

of expertise has been represented on planning and 

decisionmaking bodies. The “Stars” report, the first 

official call for SHRP and LTPP, was prepared by a 

13-member steering committee that included two academic institutions and two major corporations as well 

as a county executive and a public policy group. In the 

formulation of the SHRP Research Plans, although the 

State and Provincial highway agencies were the predominant groups, university departments of civil engineering and transportation research institutions were 

also well represented, and engineering firms and trade 

organizations comprised the balance. The LTPP advisory committees and expert task groups have continued this practice of providing diverse input into 

program planning and management.

Highway industry and user groups have also been 

providing input since the beginning of the LTPP program, for example:

•	 Paving associations (e.g., National Asphalt Pavement

Association, American Concrete Pavement Association, Association of Asphalt Paving Technologists, 

Figure 3.2. Reports of the winning papers from

2001–2002 and 2003–2004 international data analysis

contests.
42    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

INTERNATIONAL COMM

Other governments around the world were facing 

pavement issues similar to those in the United States 

when the LTPP program was first envisioned. Consequently, SHRP invited collaboration from international highway agencies during the pre-implementation 

phase to obtain information about research and to 

solicit suggestions for future cooperation. SHRP also 

sponsored a number of international workshops and 

conferences. After the first workshop, held in 1986 in 

Alexandria, Virginia, SHRP adopted a formal policy of 

international cooperation, and several other conferences followed. In 1988, LTPP was one of two themes 

at a SHRP International Technical Workshop held in 

Bath, England. Delegates representing 17 countries11

exchanged information and plans for data collection 

testing procedures, information management systems, 

laboratory accreditation, and other issues related to 

measuring long-term pavement performance. 

By 1994, more than 10 countries were conducting 

their own LTPP studies, while others were planning to 

do so, and 30 countries had each identified an international coordinator to facilitate the exchange of information about the LTPP program and pavement 

research. Researchers from other countries also use 

LTPP data to address their research needs. Members of 

highway agencies in many countries have participated 

in the LTPP loaned staff program (Australia, Canada, 

Denmark, Finland, France, Germany, Japan, Norway, 

Romania, Slovenia, South Africa, Sweden, Venezuela, 

and the United Kingdom during the SHRP years 

alone)12 and have served as members in one or more 

of the TRB LTPP committees or ETGs (e.g., Canada, 

Denmark, Germany, Sweden, The Netherlands, and 

the United Kingdom). From time to time, international 

International Coordinator Meeting,

Washington, DC, 19

Face-to-face meetings were one avenue of participation for the international highway community. 

The international coordinators reported on their 

own highway research programs at SHRP-sponsored 

workshops and TRB’s Annual Meeting and contributed their expertise through on-site staff assignments in Washington, advisory committees, and 

ETGs. Represented at the pictured meeting were 

Canada, Australia, Finland, Germany, Sweden, 

Norway, Austria, Denmark, and the United Kingdom, 

with others. Participation came from as far as 

South Africa, Egypt, and Japan.

Interna

organizations, such as the International Road Federation, Pan-American Institute of Highways, USAID, 

World Road Association-PIARC, and The World Bank, 

have also been represented in forums and on committees. International exchange of information and onsite 

visits have continued throughout the LTPP program.
3: LTPP PROGRAM PARTNERSHIPS    43

5. AASHTO Interim Guide for Design of Pavement 

Structures. American Association of State Highway 

and Transportation Officials, Washington, DC, 1972, 

rev. 1981. 

6. Strategic Highway Research Program, Research Plans, 

Final Report. Transportation Research Board, National 

Research Council, National Cooperative Research 

Program, Washington, DC, May 1986.

7. “Thank You for Saying ‘Yes’ When We Called,” LTPP 

Newsletter, vol. 7, no. 1 (Winter 2011; FHWA-HRT-11-

028), p. 2. http://www.fhwa.dot.gov/publications/

ltppnews/11028.pdf.

8. R. G. Hicks and J. B. Sorenson (Eds.). LTPP Data: 

Making Something of It: Papers From the International 

Contest on LTPP Data Analysis 1998–1999. American 

Society of Civil Engineers, Reston, VA, 2001.

9. J. Arellano et al. Improving Pavements With Long-Term 

Pavement Performance: Products for Today and 

Tomorrow, Papers From the 2003-2004 International 

Contest on Long-Term Pavement Performance Data 

Analysis (FHWA-HRT-06-109). Federal Highway 

Administration, McLean, VA, 2006.

10. “Transportation & Development Institute (T&DI) 

of the American Society of Civil Engineers (ASCE) 

and Long-Term Pavement Performance (LTPP) 

International Data Analysis Contest.” Web document. 

http://www.fhwa.dot.gov/research/tfhrc/programs/

infrastructure/pavements/ltpp/contestguide2015.pdf.

11. SHRP-LTPP International Participation: Five-Year 

Report (SHRP-P-389). Strategic Highway Research 

Program, National Research Council, Washington, DC, 

1994, pp. 1–3, 131, 133–136. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-389.pdf.

12. SHRP-LTPP International Participation: Five-Year 

Report (SHRP-P-389). Strategic Highway Research 

Program, National Research Council, Washington, DC, 

1994, p. 131. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-P-389.pdf.

SUMMARY

The LTPP program has flourished within a cooperative 

structure that from the program’s beginning has involved 

the State and Provincial highway agencies, their representative organizations AASHTO and C-SHRP, TRB’s 

research advisory capacity by way of its advisory committees and ETGs, the participation of professional organizations and researchers from other countries, 

continuous support from FHWA, a dedicated management corps, and experienced contractor staff. With a 

commitment to fulfill the program’s goal through 

changes in management and funding, including financial contributions that are discussed in the next chapter, this productive collaboration among the partners 

has moved the LTPP program forward for more than 

25 years. Continuing these partnerships into the 

future will assure that the program remains relevant 

to the needs of highway agencies and the pavement 

research community.

REFERENCES

1. LTPP Program Focus: The Assessment: Final Summary 

Report. Federal Highway Administration, McLean, VA, 

March 1997. Available at LTPP InfoPave Web site.

2. RTAC News (Sept.–Oct. 1986), vol. 12, no. 5. Roads and 

Transportation Association of Canada, Ottawa, ON, 

pp. 1, 2.

3. Canadian Strategic Highway Research Program—

C-SHRP. Council on Highway and Transportation 

Research and Development, Road and Transportation 

Association of Canada, Ottawa, ON, pp. 1–7.

4. P. Benson. “International Experiments: A Prime 

Example.” Long-Term Pavement Performance: 

Proceedings of the SHRP Midcourse Assessment 

Meeting. National Research Council, Washington, DC, 

April 1991, pp. 60–61. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-91-514.pdf.
44    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The ultimate return on investment from the LTPP program is the economic 

benefit realized from better design, construction, and management 

of the Nation’s pavements.

© muratart/Shutterstock.com
4: federalinestmen

Federal Investment in

the LtpP Prog

LTPP UNDER FIVE HIG

LEGISLATION

Since 1987, the LTPP program has been fortunate to 

have dedicated funding to carry out its goal and objectives (chapter 1) through five Federal transportation 

statutes: Surface Transportation and Uniform Relocation Assistance Act of 1987 (STURAA), which implemented the program; Intermodal Surface Transportation 

Efficiency Act of 1991 (ISTEA); Transportation Equity 

Act for the 21st Century (TEA-21); Safe, Accountable, 

Flexible, Efficient Transportation Equity Act: A Legacy 

for Users (SAFETEA-LU); and continues now under 

Moving Ahead for Progress in the 21st Century 

(MAP-21). Table 4.1 shows Federal funding for the program from 1987 through 2014.  

The Federal investment in the LTPP program through fiscal year 2014 (over a period of 27 years) is 

$311.56 million. This investment includes funding allocated over five highway authorizations. In addition 

to the Federal investment, the program has benefited from significant direct and indirect support from 

AASHTO, C-SHRP, and individual States and Provinces. 

Funding Variations

LTPP funding levels have varied over the life of the 

program and have relied on Federal and other sources. 

Although this section focuses primarily on the Federal 

investment that has been dedicated to the program 

through authorizing legislation, other funds have been 

used to perform program activities. Table 4.2 details 

annual LTPP funding and funding sources from the 

program’s beginning through 2014. Figure 4.1 illustrates the variation in funding received from the highway bills and compensatory contributions received to 

support LTPP activities after dedicated Federal funding was reduced in 1999. Added to these contributions 

are resources that the Federal Highway Administration (FHWA) has supplied, which are not included in 

the summaries of Federal expenditures in tables 4.1 

4
46    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

and 4.2. These contributions include the cost of engineering and clerical staff salaries, travel funds, equipment, supplies, and routine overhead. 

Initially, in 1987, the LTPP program received $50 

million of the $150 million provided to the Strategic 

Highway Research Program (SHRP) by STURAA. In 

1992, the administration of the program was transferred to FHWA, and ISTEA provided $37.52 million 

through 1997, with FHWA contributing an additional 

$49.77 million from its research and technology funds. 

The combined funds averaged $14.55 million per year, 

approximately the amount that was estimated would 

be needed to sustain the LTPP studies when the program was transferred from SHRP to FHWA. From 

1998 through 2003, funding from TEA-21 and the Revenue Aligned Budget Authority (RABA) of TEA-21 plus 

contributions to the program from the American Association of State Highway and Transportation Officials 

(AASHTO) provided on average $12.59 million per 

year for the LTPP program. From 2004 through 2009, 

funding through extensions of TEA-21, SAFETEA-LU 

and its associated technical corrections bill, and the 

FHWA Innovative Pavement Research and Deployment Program (IPRD) provided approximately $8.91 

million per year for the LTPP program. Finally, from 

2010 through 2014, funding through extensions of 

SAFETEA-LU, the passage of MAP-21, and FHWA’s 

IPRD funds is estimated to provide $7.47 million per 

year to continue the LTPP mission. 

States and Provinces have contributed resources estimated to be in excess of $500 million to the program in 

services and direct expenditures. Their highway agencies have provided construction of the test sections, 

materials testing, traffic control, traffic data collection, 

management, loaned staff, and equipment supporting 

the broad array of LTPP activities. During periods of 

reduced Federal funding, their contributions to pooledfund studies have sustained critical LTPP activities. 

Canada’s Strategic Highway Research Program, 

known as C-SHRP, also contributed to the program during funding shortfalls. Between 1999 and 2001, C-SHRP 

funded the data interpretation of film images collected 

during the automated distress surveys, contracting with 

the survey vendor to interpret about 490 LTPP test 

sections in the United States and Canada at a cost 

of $120,000. C-SHRP also funded the publication of 

Preserving and Maximizing the Utility of the Pavement 

Table 4.1. LTPP program Federal funding (fiscal years 19

    Funding 

Fiscal Years Authorizing Highway Legislation (in millions of dollars)

1987–1991 Surface Transportation and Uniform Relocation Assistance Act $50.0

(Public Law 100-17, April 2, 1987)

1992–1997 Intermodal Surface Transportation Efficiency Act 87.

(Public Law 102-240, December 18, 1991)

1998–2003 Transportation Equity Act for the 21st Century 75.52 

(Public Law 105-178, June 9, 1998)

2004–2009 TEA-21 Extension + Safe, Accountable, Flexible, Efficient Transportation 53.44

Equity Act: A Legacy for Users 

(Public Law 109-59, August 10, 2005)

2010–2014 SAFETEA-LU Extensions + Moving Ahead for Progress in the 21st Century 45.3

(Public Law 112-141, July 6, 2012)

TOTA  $311.

States and Provinces have contributed 

resources estimated to be in excess of 

$500 million to LTPP in services and direct 

expenditures. Their contributions to pooledfund studies have sustained critical LTPP 

activities, and their support through 

AASHTO has been critical to the program. 
4: federalinestmen

Performance Database. In this document addressed to 

the highway community, the Transportation Research 

Board (TRB) LTPP Committee stated its view of what 

would be needed beyond 2009 (the anticipated end of 

the program) to complete LTPP data collection, data 

analysis, and product development and to preserve and 

make accessible LTPP data for future researchers.1

The distribution of LTPP program expenditures by 

cost element can only be roughly estimated. Expenditures have varied from year to year in response to program priorities set in consultation with the advisory 

committees, the maturing of the program, and varying 

levels of Federal investment. Some costs are difficult to 

quantify, for example, the activities supported financially by the States and Provinces (estimated at more 

than $500 million), product development covered by 

non-LTPP funds, and overhead costs and staffing supported by FHWA. Excluding expenditures such as 

these, the distribution of the Federal investment by 

cost element, averaged over the years, is estimated as 

follows: program management, outreach, and coordination, 8 percent; data collection (equipment, personTable 4.2. LTPP Timeline—Highway legislated and other funding sources (in millions of

Legislated AASHTO RABA IPRD Total Funding

Highway Legislation FY Funding FunFunding2 Funding3 per Yea

SHRP Management

 STURAA 1987 $10.00 $10.00

1988 10.00 10.00 

1989 10.00 10.00 

1990 10.00 10.00 

1991 10.00 10.00 $50.00 

FHWA Management

 ISTEA 1992 13.7  13.7

1993 12.14 12.14 

1994 14.94 14.94 

1995 14.80 14.80 

1996 15.83 15.83 

1997 15.80 15.80 87.29 

 TEA-21 1998 10.00 10.00 

1999 8.83 $4.70 13.53 

2000 8.71 5.03 13.74 

2001 8.77 3.55 12.32 

2002 9.04 0.55 $3.10 12.69 

2003 8.94 4.30 13.24 75.52 

 TEA-21 Extension 2004 9.40 9.40 9.40

 SAFETEA-LU 2005 8.23 8.23

2006 7.14 $0.16 7.30 

2007 7.45 1.23 8.68 

2008 8.70 0.90 9.60 

2009 8.82 1.41 10.23 44.04 

 SAFETEA-LU 2010 8.81 0.61 9.42

 Extension 2011 8.72 1.60 10.32 

2012 8.53 8.53 28.27

 MAP-21 2013 8.32 8.32 

2014 8.72 8.72 17.04 

 Total $284.42 $13.83 $7.40 $5.91

(1) A significant portion of the LTPP funding during the TEA-21 highway legislation years came from AASHTO. AASHTO’s Standing Committee on Resear

passed a resolution to use National Cooperative Highway Research Program project funds to support LTPP program activities from 1999 to 2002. 

(2)  Significant funding was also provided by RABA, a provision of TEA-21 that adjusted transportation funding to match actual revenue from gas an

vehicle taxes.

(3) The FHWA IPRD provided non-LTPP funds to the program during the SAFETEA-LU years for product developme
48    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

nel, data processing and quality assurance, laboratory 

testing, and training), 52 percent; database management (information management systems, data storage 

and distribution, and customer service), 30 percent; 

data analysis and product development, 10 percent.

The following sections, and tables 4.3 through 4.7, 

provide more detailed information about funding during the STURAA, ISTEA, TEA-21, SAFETEA-LU, and 

MAP-21 highway legislation periods associated with 

the LTPP program, including period covered, funding, 

legislation requirements, impact on operations, and, 

where applicable, delays in legislation passage. 

SURFACE TRANSPORTATIO

UNIFORM RELOCATION ASSISTANCE 

STURAA, which was enacted April 2, 1987, as Public 

Law 100-17, authorized SHRP and provided $30 million per year or a total of $150 million for carrying out 

the program, which the States paid for by contributing 

0.25 percent of their Federal-Aid Highway Program 

funds.2 The STURAA legislation covered LTPP operations for a period of 4 years and 8 months, from April 2, 

1987, to December 18, 1991, when the next highway legislation was enacted (see the sidebar for excerpts from 

the legislation).

Of the funding provided to SHRP, $10 million per 

year or a total of $50 million was dedicated to the 

LTPP program (table 4.3). This projection matched 

the funding called for in the preliminary LTPP plans 

contained in the Strategic Highway Research Program 

Research Plans, Final Report, May 1986 or “Brown 

Book.”3

 However, once implementation of the program commenced, it became apparent fairly quickly 

that the funding level provided was not sufficient to 

carry out all of the planned activities. The budget 

realities had an impact on a number of program 

Figure 4.1. LTPP funding in fiscal years 1

$0.00

$2.00

$4.00

$6.00

$8.00

$10.00

$12.00

$14.00

$16.00

In Millions of Dollars

Fiscal Year

Legislated Funding AASHTO Funding RABA Funding IPRD Funding

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

20052006

2007

2008

2009

2010

2011

2012

2013

2014
4: federalinestmen

issues, such as reductions in the types and numbers of 

pavement layer materials tests that could be performed, but perhaps no impacts were as significant 

and long lasting as the following two:

•	 Under the General Pavement Study (GPS) suite of

experiments, the materials testing activities were 

centralized through sampling and testing contractors under the direct control of the program. 

Because of budget limitations, however, the pavement layer materials testing program was decentralized for the Specific Pavement Study (SPS) 

experiments. Thereby the responsibility for sampling and testing many of these projects was handed 

over to the participating agencies. However, as the 

LTPP program began to review the materials data 

from the SPS test sections, considerable variation 

was discovered among the States and Provinces 

in their sampling and testing procedures, and the 

SPS materials test results were found to be inconsistent and incomplete relative to the program’s 

standards.

•	 Responsibility for traffic data collection for the

GPS and SPS test sites was assigned to the individual participating highway agencies. However, 

SEC. 128. Strategic Highway Research Progra

Section 307 of title 23, United States Code (relating 

to research and planning), is amended by redesignating subsections (d) and (e) (and any references 

thereto) as subsections (e) and (f), respectively, and 

by inserting after subsection (c) the following new 

subsection:

“(d) STRATEGIC HIGHWAY RESEARCH PROGRAM.—

“(1) ESTABLISHMENT. —The Secretary, in consultation with the National Academy of Sciences and 

American Association of State Highway and 

Transportation Officials, shall carry out such 

research, development, and technology transfer 

activities as the Secretary determines to be strategically important to the national highway 

transportation system.

“(2) COOPERATIVE AGREEMENTS.—The Secretary 

may make grants to, and enter into cooperative 

agreements with, the American Association of 

State Highway and Transportation Officials and 

the National Academy of Sciences to carry out 

such activities under this subsection as the Secretary determines are appropriate. Advance payments may be made as necessary to carry out 

the program under this subsection.

“(3) PERIOD OF AVAILABILITY.—Funds set aside to 

carry out this subsection shall remain available 

for the fiscal year in which such funds are made 

available and the three succeeding fiscal years.

. . . .

“(5) ANNUAL REPORT.—The Secretary shall transmit a report annually beginning on January 1, 

1988, to the Committee on Environment and 

Public Works of the Senate and the Committee 

on Public Works and Transportation of the House 

of Representatives which provides information 

on the progress and research findings the program conducted under this subsection.”

Surface Transpor

Table 4.3. LTPP program funding under STURAA (fiscal years 

Funding by Fiscal Year (in millions of dollars) T

Funding Source    1987 1988 1989 1990 1991 Funding

STURAA $10 $10 $10 $10 $10 $5

Total $10 $10 $10 $10 $10 $5
50    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

traffic-monitoring technology never fulfilled early 

expectations that it would be economically and 

technically feasible to install reliable weigh-inmotion equipment at every LTPP test site. The lack 

of appropriate equipment, coupled with problems 

that arose regarding data quality and timely 

monitoring, led to large gaps in traffic data in the 

LTPP database.

The impact of the materials and traffic data issues on 

LTPP operations became quite evident in the mid1990s and led to the development and implementation 

of important materials testing and traffic monitoring 

action plans to address data deficiencies. These remedial actions, discussed in chapter 7, required a significant level of additional funding.

INTERMODAL SURFACE TRANSPOR

EFFICIENCY ACT OF 19

ISTEA was enacted December 18, 1991, as Public Law 

102-240.4 The legislation provided funding for implementation of SHRP products as well as continuation of 

the LTPP program (see sidebar).

Enactment of the ISTEA legislation defined the end 

of SHRP and the beginning of LTPP under FHWA 

management, and the legislation covered LTPP operations for a period of 5 years and 8 months, from 

December 18, 1992, to June 9, 1998. ISTEA provided 

$37.52 million for continuation of the LTPP program, 

and FHWA assigned an additional $49.77 million from 

its research and technology funds; together these 

resources averaged $14.55 million per year (table 4.4). 

SEC. 6001. Research and Technology Prog

Subsections (a), (b), and (c) of section 307 of title 23, 

United States Code, are amended to read as follows: 

. . . .

“(b) MANDATORY CONTENTS OF RESEARCH 

PROGRAM. —

. . . . 

“(2) SHRP RESULTS.—

“(A) IMPLEMENTATION.—The highway research 

program under subsection (a) shall include a 

program to implement results of the strategic 

highway research program carried out under 

subsection (d) (including results relating to automatic intrusion alarms for street and highway 

construction work zones) and to continue the 

long-term pavement performance tests being 

carried out under such program.

“(B) MINIMUM FUNDING.—Of amounts deducted 

under section 104(a) of this title, the Secretary 

shall expend not less than $12,000,000 in fiscal 

year 1992, $16,000,000 in fiscal year 1993, and 

$20,000,000 per fiscal year for each of fiscal 

years 1994, 1995, 1996, and 1997 to carry out 

this paragraph.”

Intermodal Su

Table 4.4. LTPP program funding under ISTEA (fiscal years 

Funding Funding by Fiscal Year (in millions of dollars) T

Source 1992 1993 1994 1995 1996 1997 Funding

ISTEA § 60011 $4.00 $6.00 $8.00 $6.00 $7.52 $6.00 $37.

FHWA GOE2,3 9.78 6.14 6.94 8.80 8.31 9.80 49.77

TOTAL $13.78 $12.14 $14.94 $14.80 $15.83 $15.80 $87.

(1)  Section 6001 provided $108 million to FHWA for SHRP implementation and the continuation of LTPP ($12 million in FY 1992, $16 million in FY 19

and $20 million per fiscal years 1994 through 1997). 

(2) FHWA GOE = General Operating Expenses. These amounts do not include staff salaries for eight engineers, one clerk, travel, equipment, and supplies 

at an approximate cost of $750,000 per year or $3.75 million for fiscal years 1992 to 1997. Routine overhead costs were also provided by FHWA.

(3) Over the 5-year period, $5.4 million was deducted from this total for management and coordination activities.
4: federalinestmen

This budget represented a 45 percent increase compared to STURAA funding during the 1987 through 1991 

SHRP years. More importantly, this budget increase 

permitted the LTPP program to make important adjustments as well as to implement new initiatives that would 

later prove to have a positive impact on the program. 

These adjustments and initiatives included:

•	 Increased monitoring frequencies on LTPP test sections, particularly for falling weight deflectometer

(FWD) deflection testing and longitudinal profile 

surveys.

•	 Formal introduction of manual pavement surface

distress surveys (in addition to the photographic 

distress surveys).

•	 Implementation of the Seasonal Monitoring Program

to study the impact of seasonal climate variations on

pavement performance. 

•	 Planning and initial implementation ofthe Dynamic

Load Response Program at select SPS-1 and -2 projects 

(structural factors for flexible and rigid pavements, 

respectively).  

TRANSPORTATION EQUITY 

THE 21ST CEN

TEA-21 was enacted June 9, 1998, as Public Law 105-

178.5 The legislation provided funding for continuation 

of the LTPP program and, unlike ISTEA, also required 

that the LTPP program “prepare products to fulfill 

program objectives and meet future pavement technology needs” (see sidebar).

TEA-21 covered LTPP operations for a period of 

7 years and 2 months, from June 9, 1998, to August 10, 

2005. The LTPP program operated under the TEA-21 

TITLE V—Tr

Subtitle A—Funding

SEC. 5001. Authorization Of Appropriations. . . .

(c) ALLOCATIONS.—

(1) SURFACE TRANSPORTATION RESEARCH.—Of 

the amounts made available under subsection (a)(1)—

(A) $10,000,000 for each of fiscal years 1998 

through 2003 shall be available to carry out section 502(e) of title 23, United States Code (relating to long-term pavement performance); . . . .

Subtitle B—Research and Technology . .

SEC. 5102. Surface Transportation Researc

Chapter 5 of title 23, United States Code (as added 

by section 5101 of this title), is amended by adding at 

the end the following: 

“§ 502. Surface transportation research . . . .

“(e) LONG-TERM PAVEMENT PERFORMANCE PROGRAM.— 

“(1) AUTHORITY.—The Secretary shall complete 

the long-term pavement performance program 

tests initiated under the strategic highway research program established under section 307(d) 

(as in effect on the day before the date of enactment of this section) and continued by the Intermodal Surface Transportation Efficiency Act of 

1991 (105 Stat. 1914 et seq.) through the midpoint 

of a planned 20-year life of the long-term pavement performance program. 

“(2) GRANTS, COOPERATIVE AGREEMENTS, AND 

CONTRACTS.—Under the program, the secretary shall make grants and enter into cooperative agreements and contracts to— 

“(A) monitor, material-test, and evaluate highway test sections in existence as of the date of 

the grant, agreement, or contract; 

“(B) analyze the data obtained in carrying out 

subparagraph (A); and 

“(C) prepare products to fulfill program objectives 

and meet future pavement technology needs.”

Transportation
52    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

legislation for the longest period of any legislation, 

which had impacts on operations due to its reduced 

funding level. In contrast to ISTEA, which increased 

the LTPP budget by 45 percent from that provided 

under STURAA, TEA-21 reduced LTPP funding more 

than 30 percent, from $14.50 million per year to 

approximately $9.00 million per year after the yearly 

appropriations takedown (or rescission), which varied 

each year, was applied to the authorized funding for 

the program (table 4.5). There was no takedown in 1998. 

From October 1, 2003 (anticipated end of TEA-21 legislation), until August 10, 2005 (actual passing of the 

next highway legislation), the LTPP program operated 

under a series of extensions to TEA-21 and continuing 

resolutions. These extensions incrementally provided 

funding in the amount of $9.40 million per year. 

Program Adjustments Due to Fundin

Constraints Under TEA-

The budget cuts had an impact on the LTPP program’s 

ability to effectively plan and execute key activities 

required to complete the program’s mission. While 

many of the core activities continued, the decreased 

level of funding required that LTPP make some significant program adjustments, taking into consideration 

contractual obligations and programmatic issues. 

Those adjustments included the following:

•	 Basic data collection (manual distress and profile

surveys, deflection testing, and other field evaluations) and processing activities were reduced to levels below those under the ISTEA legislation. 

•	 Important data collection activities were either postponed or delayed, including drainage surveys, forensic 

investigations, within-test-section thickness surveys 

(using ground penetrating radar) and some quality 

assurance review activities such as the profiler and 

FWD comparisons. The purchase of much-needed 

replacement equipment also had to be postponed. 

•	 The Seasonal Monitoring Program was terminated.

•	 Development andpopulationof key computedparameters for storage in the database were postponed. The 

most important of these parameters was the dynamic 

modulus of hot-mix asphalt concrete mixtures (often 

referred to as |E*|), which was considered essential in 

the calibration of AASHTO’s Mechanistic–Empirical 

Pavement Design Guide atthe regional and local level.

Other affected computed parameters included the 

moisture content of unbound layers from timedomain reflectivity readings, frost/thaw depth determinations from resistivity measurements, and elastic 

layer moduli backcalculation from deflection data. 

•	 The ability to plan for future procurements stopped

due to budget uncertainties. In addition, two major 

planned contract procurements ready for advertisement were put on hold—the photographic distress survey contract and a centralized materials 

testing contract. 

•	 Minimal task order work assignments were made to

the data analysis contracts awarded during the original TEA-21 legislation. 

Table 4.5. LTPP program funding under TEA-21 (fiscal years 1

Funding Funding by Fiscal Year (in millions of dollars) T

Source 1998 1999 2000 2001 2002 2003 Funding

TEA-21 $10.00 $8.83 $8.71 $8.77 $9.04 $8.94 $54.29

AASHTO — 4.70 5.03 3.55 0.55 — 13.8

RABA — — — — 3.10 4.30 7.40

TOTAL $10.00 $13.53 $13.74 $12.32 $12.69 $13.24 $75.

Perhaps the most critical impact of the 

TEA-21 extensions to achievement of the 

program’s objectives was the program’s 

inability to monitor aging pavement 

test sections at the needed intervals.
4: federalinestmen

•	 No new product development activities were started.

•	 Key activities in support of the Ancillary Information Management System were either cut back or 

postponed, including work on the LTPP library and 

on information not contained in the database (e.g., 

raw profile and deflection data and distress photographs and images). 

•	 Vital communication and coordination activities

were hampered due to limited funds, especially 

those involving the TRB LTPP Committee and expert task groups (ETGs). A number of important

meetings could not be held, and attendance at others was limited. Visits with State partners for coordination activities had to rely more on teleconferences rather than face-to-face meetings.

The TEA-21 adjustments were clearly painful cuts for a 

long-term program to endure and still deliver the products it was designed to produce. Perhaps the most critical impact of the TEA-21 extensions on achievement of 

the program’s objectives was the program’s inability to 

monitor aging pavement test sections at the needed 

intervals. Cutbacks in monitoring frequency resulted in 

sections being dropped from the study without the final 

round of condition measurements being recorded.

Were it not for the contributions made to the program by AASHTO, which provided $13.80 million 

during fiscal years 1999 through 2002, and funding 

derived from RABA, which amounted to $7.40 million 

during fiscal years 2002 and 2003, the adverse impact 

of TEA-21 on LTPP operations would have been much 

more severe. 

SAFE, ACCOUNTABLE, FLEXIB

EFFICIENT TRANSPORTATION

ACT: A LEGACY FOR USER

SAFETEA-LU was enacted August 10, 2005, as Public 

Law 109-59 (see sidebar).6 This legislation was to take 

the LTPP program to its formal conclusion at the end 

of fiscal year 2009—the end of the 20-year period considered to be the minimum period required to realize 

the benefits of long-term monitoring. At the time of 

(i) Long-Term Pavement Performance Pr

(1) IN GENERAL.—Section 502(f) of such title (as 

redesignated by subsection (b) of this section) is 

amended to read as follows:

“(f) LONG-TERM PAVEMENT PERFORMANCE PROGRAM.—

“(1) AUTHORITY.—The Secretary shall continue to 

carry out, through September 30, 2009, tests, 

monitoring, and data analysis under the longterm pavement performance program.

“(2) GRANTS, COOPERATIVE AGREEMENTS, 

AND CONTRACTS.—Under the program, the Secretary shall make grants and enter into cooperative agreements and contracts to—

“(A) monitor, material-test, and evaluate highway test sections in existence as of the date of 

the grant, agreement, or contract;

“(B) analyze the data obtained under subparagraph (A); and

“(C) prepare products to fulfill program objectives and meet future pavement technology 

needs.”

(2) FUNDING.—Of the amounts made available by 

section 5101(a)(1) of this Act, $10,120,000 for 

each of fiscal years 2005 through 2009 shall be 

available to carry out section 502(f) of such title.

Safe, Accountable, Fle

A Legacy for  U
54    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

SAFETEA-LU’s enactment, however, much additional 

work remained to be done to fulfill the LTPP mission.

LTPP program funding under the SAFETEA-LU 

legislation was set at $10.12 million per year. However, 

after a reduction was applied to correctfor theTitleV—

Surface Transportation Research Development and 

Deployment overdesignation, the program received the 

amounts shown in table 4.6. Moreover, as was the case 

under the previous TEA-21 legislation, SAFETEA-LU 

required that the program “prepare products to fulfill 

program objectives and meet future pavement technology needs.”7

 Additional funds were provided to the 

LTPP program in fiscal years 2006–2009 from FHWA 

IPRD Program funds and from the SAFETEA-LU Technical Corrections Act of 2008 (Public Law 110-244) in 

fiscal years 2008 and 2009 (table 4.6). These additional 

funds brought the average annual LTPP budget under 

this legislation to around $8.8 million per year. 

To put these numbers into perspective, in 2001 the 

TRB LTPP Committee had projected that the funding 

required to fulfill the LTPP mission from fiscal year 

2004 through fiscal year 2009 was $120 to $125 million, or approximately $20 million per year.8 This figure included activities that FHWA had planned to 

accomplish by the end of the legislation and those 

designed to address some of the program’s high-priority needs. With the budget provided by SAFETEA-LU, 

however, it was not possible to perform many of the 

actions proposed by the TRB LTPP Committee. Furthermore, whether LTPP operations would be extended past 2009 was uncertain. Like previous legislation, 

SAFETEA-LU extended authority for the program’s 

operation only for the 5 years the act covered. Since the 

future of the LTPP program was not clear, FHWA 

decided that the most responsible course of action for 

use of program funds was to prepare simultaneously 

for both a transition of LTPP activities past 2009 and 

possible program termination in 2009.9

Program Adjustments Due to Fundin

Constraints Under SAFETEA-L

As the LTPP program prepared for the unknown outcomes of the delayed legislation, the uncertainties led 

to the adoption of the following statement to describe 

the primary program deliverable come September 

2009: “a quality pavement performance database and 

supporting ancillary information and document warehouse that enables researchers to better fulfill the goals 

of understanding pavement performance on which the 

program was founded.”10 Five specific attributes of the 

database were defined as necessary to achieving the 

primary programmatic goal by 2009:

•	 A database containing complete data sets (i.e., inventory, materials, traffic, climate, maintenance and 

rehabilitation, and pavement performance data) for 

most LTPP test sections.

•	 A database whose contents have been reviewed and

checked through quality control/quality assurance 

(QC/QA) processes and data studies and that is as 

error-free as time and the program budget will allow.

•	 A database that is documented not only in terms of

its content but also in how those data were collected 

and their quality.

•	 A database that is accessible to the public.

•	 A database that conforms to Federal Government

information dissemination quality guidelines. 

Table 4.6. LTPP program funding under SAFETEA-LU (fiscal years 20

Funding Funding by Fiscal Year (in millions of dollars) T

Source 2004 2005 2006 2007 20081 20091 Funding

TEA-21 Extension $9.40 — — — — — $9.40

SAFETEA-LU — $8.23 $7.14 $7.45 $8.70 $8.82 40.3

FHWA IPRD Program —   0.1  1.2  0.90 1.41 3.

TOTAL $9.40 $8.23 $7.30 $8.68 $9.60 $10.23 $53.

(1) Includes the SAFETEA-LU Technical Corrections Act of 2008 (Public Law 110-244, June 6, 2008
4: federalinestmen

Working towards this deliverable, it was decided that 

LTPP program funds provided by the SAFETEA-LU 

legislation would be used for the following high-priority 

program needs:

•	 Completing data sets:

– Continue implementation of the Traffic Data 

Action Plan at SPS project sites to collect missing 

traffic volume and load data (chapter 7).

– Continue implementation of the Materials Data

Action Plan at SPS project sites to collect missing 

materials property data (chapter 7).

– Perform one more round of pavement performance measurements on selected LTPP test 

sections.

•	 Refining database and ancillary information:

– Continue the database QC/QA activities and 

investigation of discrepancies.

– Complete the database and program documentation.

– Improve direct user access to the database and 

ancillary information.

– Provide annual data releases.

•	 Coordinating program activities:

– Continue program coordination with TRB, highway agencies, AASHTO, and other FHWA offices.

– Continue internal program coordination.

•	 Developing and publishing a post-2009 plan to secure the legacy of the LTPP program. This plan 

would provide for the continuation of essential 

LTPP activities: 

– Storage, maintenance, and user support for the 

LTPP database and associated information. 

– Storage and user support for the LTPP Materials 

Reference Library. 

– Collection of missing data and monitoring of 

LTPP test sections that had not reached the end 

of their performance life. 

– Implementation of the LTPP Strategic Data 

Analysis Plan (chapter 10).

– Implementation of the LTPP Product Development Plan (chapter 10).

The decision to make use of available LTPP resources 

for the designated high-priority needs, listed above, 

required significant adjustments to other program 

activities. Similar to adjustments made under TEA-21, 

activities were either reduced or eliminated in data 

collection, database development, data analysis, product development, and coordination as follows: 

•	 Data collection activities:

– Frequency of pavement condition data collection 

was reduced.

– More than 300 active test sections were placed in 

the out-of-study category (i.e., no future monitoring would be performed). These sections were 

in the SPS-3 (preventive maintenance of flexible 

pavement), -4 (preventive maintenance of rigid 

pavement), and -7 (bonded Portland cement concrete (PCC) overlay) experiments and the GPS-4

( jointed reinforced concrete), -5 (continuously 

reinforced concrete), and -9 (unbonded PCC 

overlay on PCC) experiments. 

– On the remaining active test sections, monitoring 

would only be performed on a subset of priority 

test sections. 

– Quantitative pavement surface images (photographic images) for distress interpretation would 

not be obtained. 

– Structural response measurements with the 

FWD were suspended.

– LTPP program funds were not used to support 

the regional FWD calibration centers. 

– Aging materials tests previously planned for inclusion in the SPS Materials Action Plan were 

eliminated.

– Planned activities to characterize test section

drainage features were eliminated.

– Additional ground penetrating radar measurements to obtain layer thickness measurements 

within the monitoring portion of the test section 

were eliminated.

– Activities planned to address deficiencies in traffic volume and load data at GPS project sites

were eliminated.

–	 No program funds were used to replace or update

field data collection equipment.
56    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 Database development activities:

– Development of an analysis database was suspended. 

– Overhaul of the LTPP database automated quality checks was suspended.

– Development of a complete metadata database

for all offline LTPP ancillary information was 

suspended. 

– LTPP data releases were reduced to an annual 

cycle.

– Conversion of LTPP data element units to a common standard was suspended.

– LTPP funding was not provided to support 

DataPave Online (user-friendly software for working with the LTPP database) and database user 

training. 

•	 Data analysis activities:

– Limited LTPP program funds were dedicated to 

formal data analysis projects through 2009. 

•	 Product development activities:

–	 No LTPP program funds were allocated to product development from 2006 to 2009.

•	 Coordination activities:

– LTPP-sponsored national and regional meetings 

were eliminated.

–	 National coordination meetings with LTPP data

collection contractor staff and meetings between 

the data analysis contractors and operations staff 

were reduced.

–	 TRB ETGs were reduced in number and membership size.

MOVING AHEAD FOR PROGRESS 

THE 21ST CENTUR

On July 6, 2012, MAP-21 (Public Law 112-141) was 

signed into law (see sidebar).11 MAP-21 emphasizes 

performance measurement and evaluation and sets the 

stage for a more long-term, nationally coordinated 

approach to investing in the Nation’s transportation

needs. With the removal of most earmarks and the consolidation of Federal transportation programs from 

about 90 to fewer than 30, the act is designed to focus 

resources on key goals, reduce duplication of effort, 

and provide more flexibility in managing infrastructure investment.12 

The first long-term highway authorization to be enacted since 2005, MAP-21 included an additional 

extension of SAFETEA-LU to the end of fiscal year 2012. 

Thus, new provisions of the law took effect October 1, 

2012. For fiscal years 2013 and 2014, MAP-21 reauthorized the Federal-Aid Highway Program at $40.40 

billion and $41.00 billion, respectively, equal to current funding levels plus inflation. 

Under Sections 52003 and 52013 of the act, related 

to Transportation Research and Development Strategic Planning, the Secretary of Transportation is 

directed to develop a 5-year strategic research and 

development plan to address the following purposes: 

promoting safety, reducing congestion and improving 

mobility, preserving the environment, preserving the 

existing transportation system, improving the durability and extending the life of transportation infrastructure, and improving goods movement.13

MAP-21 continues authorization for LTPP program 

activities under Title 23, Section 503(b), Highway 

Research and Development Program, of the United 

States Code. The act provides $115 million per year for 

the Highway Research and Development program, 

emphasizing research and development activities that 

maintain infrastructure integrity, meet user needs, 

and “link Federal transportation investments to improvements in system performance.”14 Research areas include 

highway safety, infrastructure integrity, planning and 

environment, highway operations, exploratory advanced 

research, and support for the Turner-Fairbank Highway 

Research Center. “Long-term infrastructure performance 

programs addressing pavements, bridges, tunnels, and 

other structures” are among the activities to be carried 

out under the program. With the exception of adding two 

new LTPP experiments, the program continues to perform the same activities as it did during the SAFETEALU period. LTPP’s resources under SAFETEA-LU 

extensions and MAP-21 are detailed in table 4.7.
4: federalinestmen

Table 4.7. LTPP program funding under MAP-21 (fiscal years 20

Funding Funding by Fiscal Year (in millions of dollars) T

Source 2010 2011 20121 2013 2014 Funding

SAFETEA-LU Extension $8.81 $8.72 $6.45 — — $23.9

FHWA IPRD Progra  0.61 1.60 — — — 2.

MAP-21 — — 2.08 8.32 8.72 19.12

TOTAL $9.42 $10.32 $8.53 $8.32 $8.72 $45.

(1) Fiscal year 2012 was funded by extensions of SAFETEA-LU and, for the last 3 months, by MAP-21

SEC. 52003. Research and Technolo

Development and Deployment.

(a) IN GENERAL.—Section 503 of title 23, United 

States Code, is amended to read as follows:

‘‘§ 503. Research and technology development

and deployment

‘‘(a) IN GENERAL.—The Secretary shall—

‘‘(1) carry out research, development, and deployment activities that encompass the entire innovation lifecycle; and

‘‘(2) ensure that all research carried out under this 

section aligns with the transportation research 

and development strategic plan of the Secretary 

under section 508.

‘‘(b) HIGHWAY RESEARCH AND DEVELOPMENT 

PROGRAM.— . . . . 

‘‘(3) IMPROVING INFRASTRUCTURE INTEGRITY.—

‘‘(A) IN GENERAL.—The Secretary shall carry out 

and facilitate highway and bridge infrastructure 

research and development activities—

‘‘(i) to maintain infrastructure integrity;

‘‘(ii) to meet user needs; and

‘‘(iii) to link Federal transportation investments 

to improvements in system performance. . . . .

‘‘(B) OBJECTIVES.—In carrying out this paragraph, the Secretary shall carry out research 

and development activities— . . . . 

‘‘(iii) to increase the reliability of lifecycle performance predictions used in infrastructure 

design, construction, and management;

‘‘(iv) to improve the ability of transportation 

agencies to deliver projects that meet expectations for timeliness, quality, and cost;

‘‘(v) to reduce user delay attributable to infrastructure system performance, maintenance, 

rehabilitation, and construction;

‘‘(vi) to improve highway condition and performance through increased use of design, materials, construction, and maintenance innovations; . . . . 

‘‘(C) CONTENTS.—Research and technology activities carried out under this paragraph may include—

‘‘(i) long-term infrastructure performance programs addressing pavements, bridges, tunnels, and other structures; . . . . ”

Moving Ahea
58    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

SUMMARY

Although FHWA management submits a budget to 

Congress, the final decision on funding is made by the 

Congress. With a Federal investment of more than 

$300 million, the LTPP program has had some years of 

generous funding that led to advances in pavement 

research, while in the leaner years, the program has 

had to make some tough decisions on what could and 

could not be accomplished and what had to be postponed. Even though funding levels for the program 

have declined over the years, the program’s goal and 

objectives have not changed.

FHWA’s commitment to support the LTPP program 

is still strong today. The LTPP program is helping to 

answer the questions of how and why pavements perform as they do. With an aging highway infrastructure 

facing the Nation, the need continues for a robust

research pavement program to help current and future 

transportation officials in their decision making. As 

shown throughout this report, the LTPP program has 

created standard practices that are commonly used by 

highway agencies and has developed a pavement performance database that is renowned worldwide. 

Although there have been significant returns on this 

Federal investment in the program, many dividends 

are still to be gained in the years ahead.

The next section in this report describes how the 

studies were developed, and the manner in which the 

data are collected, stored, and checked for quality. The 

section begins with the design and recruitment of the 

research experiments.

© f11photo/Shutterstock.com
4: federalinestmen

REFERENCES

 1. Long-Term Pavement Performance Committee, 

Transportation Research Board. Preserving and 

Maximizing the Utility of the Pavement Performance 

Database. Transportation Research Board, Washington, 

DC, 2009. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_report_2009.pdf. 

 2. U.S. Statutes at Large 101 (1987): 132–261. Surface 

Transportation and Uniform Relocation Assistance Act 

of 1987.

 3. Strategic Highway Research Program, Research Plans, 

Final Report. Transportation Research Board, National

Research Council, National Cooperative Research

Program, Washington, DC, May 1986, pp. 2, A-3.

 4. U.S. Statutes at Large 105 (1991): 1914–2207. 

Intermodal Surface Transportation Efficiency Act of 1991.

 5. U.S. Statutes at Large 112 (1998): 107–509. 

Transportation Equity Act for the 21st Century.

 6. U.S. Statutes at Large 119 (2005): 1144–1978. Safe, 

Accountable, Flexible, Efficient Transportation Equity 

Act: A Legacy for Users. 

 7. U.S. Statutes at Large 119 (2005): 1784. Safe, Accountable, Flexible, Efficient Transportation Equity Act: 

A Legacy for Users. 

8. Fulfilling the Promise of Better Roads: A Report of the 

TRB Long-Term Pavement Performance Committee. 

Transportation Research Board, The National Academies. National Academy Press, Washington, DC, 2001,

pp. 4, 21–29. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_report_2001.pdf.

 9. LTPP Beyond FY 2009: What Needs To Be Done? Federal 

Highway Administration, Washington, DC, August 

2009. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/09052/09052.pdf. 

 10. Long-Term Pavement Performance Program: Year in 

Review 2005. Federal Highway Administration, 

Washington, DC, January 2006, p. 2. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/06086/ltpp2005yir.pdf. 

 11. U.S. Statutes at Large 126 (2012): 405–988. Moving 

Ahead for Progress in the 21st Century Act. 

 12. “Summary of Moving Ahead for Progress in the 21st 

Century (MAP-21).” http://epw.senate.gov/public/

index.cfm?FuseAction=Files.View&FileStore_

id=6d1e2690-6bc7-4e13-9169-0e7bc2ca0098. 

 13. “Moving Ahead for Progress in the 21st Century Act 

(MAP-21): A Summary of Highway Provisions.” Web 

page. Federal Highway Administration, Office of Policy 

and Governmental Affairs, July 17, 2012. http://www.

fhwa.dot.gov/map21/summaryinfo.cfm. 

 14. U.S. Statutes at Large 126 (2012): 873. Moving Ahead for 

Progress in the 21st Century Act.

 15. “FHWA Pavement Performance Research Saves $50 

Million Annually in Highway Construction Costs.” 

Press Release. U.S. Department of Transportation, 

Office of Public Affairs, Oct. 31, 2001. http://www.fhwa.

dot.gov/pressroom/fhwa0135.cfm. 

“LTPP research is significantly advancing the pavement engineering process nationwide. 

The better the process, the better the product. That’s why the LTPP investment is so 

essential——it yields the kind of substantive, long-lasting improvements the public expects 

for its transportation dollars.”

——Mary E. Peters, Federal Highway Administrator 2001–2005

Developing the Studies and the Pavement 

Performance Database

II 
The shaping of the LTPP experiments was a lengthy process that was 

already underway before the program officially began and has extended 

through both the SHRP and FHWA management periods.
5: design and recruitment of the LTPP Experimen  

Design and Recruitment of 

the LTPP Experiments

5

INTRODUCTION

The shaping of the LTPP experiments was a lengthy 

process that was already underway before the program 

officially began and has extended through both the 

Strategic Highway Research Program (SHRP) and 

Federal Highway Administration (FHWA) management periods. In the early 1980s, FHWA had been 

working on design plans to field test different pavements and materials to evaluate their performance 

over time. 

Experts in the pavement engineering and statistics 

areas, including those on the Expert Task Group (ETG) 

on Experimental Design and Analysis (appendix A), 

helped to formulate the LTPP experiments. The ETG 

worked with the Pavement Performance Advisory 

Committee to identify the types of experiments they 

envisioned would accomplish the different objectives 

At the heart of the LTPP program were the pavement experiments. The design of the experiments was an 

integral part of the planning and preparation for the program, and ultimately critical to its success. Highway 

agency, industry, and university representatives collaborated to design experiments located across various 

climates that would use different materials and carry different traffic loads to assist in understanding how 

and why pavements perform as they do.

for the pavement performance monitoring program.1,2,3

In the mid-1980s when planning began, three study 

types were considered: General Pavement Studies 

(GPS), Specific Pavement Studies (SPS), and Accelerated Pavement Testing.

The GPS experiments sought to use in-service pavement sections to examine general performance by 

pavement type. It was thought that these sections 

would provide relatively quick and cost-efficient 

insights into the performance of pavement designs 

generally used in the United States and Canada at the 

time. In contrast, the SPS studies were designed to 

investigate the influence on performance of specific 

features, such as drainage, layer thickness, and rehabilitation or maintenance treatments. These sections 

were to be constructed specifically for the LTPP study. 
64 HE LONG-T

Key Milestones in the Design 

of the Experiments

1985 First meeting of the Pavemen

Performance Advisory

Committee to discuss LTP

objectives, experiment 

designs, and management 

of the program 

1988 Selection of first GPS test 

1988 First FWD and materials d

collection, in North Caroli

1989 Selection of SPS test sites beg

1990 Construction of first SPS pro

1990 First SPS maintenance 

rehabilitation sections selected 

1992 First pilot for SPS-9, in Ari

2000 Construction of last SPS proj

under original LTPP experiment

2012 Planning for warm-mix asphalt 

experiment begins, first new LTPP

experiment in 20 years

2014 Recruitment begins for ne

warm-mix asphalt experiment 

(SPS-1

2014 Planning for pavement 

preservation experiment begins

In the third type of study proposed, Accelerated Pavement Testing, sections would be constructed and loaded using a machine simulating traffic for rapid study 

results. After consideration and deliberation, it was 

ultimately decided to proceed with the GPS and SPS 

experiments as part of the SHRP-LTPP program and to 

pursue accelerated pavement testing under separate 

efforts. As highway agencies adopt new pavement 

technologies, new experiments are designed to evaluate the long-term performance of these technologies. 

The remaining sections in this chapter briefly discuss 

the original experiment designs and recruitment of the 

test sections, as well as the roles that SHRP, FHWA, and 

the program’s contractors had in implementing the 

LTPP experiments. The general design criteria and 

design issues specific to the GPS and SPS experiments 

are discussed in the sidebar. A more thorough discussion of the evolution of the LTPP experiments is found 

in SHRP-LTPP Overview: Five-Year Report.4 

DESIGN OF GPS EXPERIMENTS

As mentioned previously, the purpose for monitoring 

GPS test sections was to observe the performance of 

in-service pavement sections to the end of their design 

lives. This approach had both advantages and disadEarly program planners meet to discuss the experiment 

designs and vision for the LTPP program (left to right, 

Ralph Haas, John German, Virgil Anderson, and Ed Pensok).

© junyyeung/Shutterstock.com
In formulating the design criteria for the GPS and SPS 

experiments, certain criteria were common for both 

experiments. For example, all GPS and SPS test sections are in the outside single lane (“slow lane”) of the 

roadways. In addition, the original test section length 

was planned to be 1,500 ft (457.2 m), but at the 

SHRP-LTPP Advisory Committee meeting in February 1988, it was agreed to shorten the section length 

to 500 ft (152.4 m). Reasons for this change included 

the difficulty in finding homogeneous sections 1,500 

ft in length and the acknowledgment that performance should be sufficiently consistent over a 500-ft 

length to account for general roadway conditions. In 

addition, 500 ft was the shortest length permitting 

measurement of 250-ft (76.2-m) longitudinal profile 

wavelengths.5 In practice there are some exceptions: 

some SPS-6 sections (rehabilitation of jointed Portland cement concrete) are 1,000 ft (304.8 m) long, 

and some “supplementals” are shorter or longer than 

the prescribed 500 ft. “Supplementals” are test sections added to SPS sites by the States and Provinces 

to examine features of particular interest to them.

Gener

vantages. It allowed for relatively rapid implementation, as no construction was required, and it provided 

data to begin populating the LTPP database. On the 

other hand, the structural condition of the pavement 

when it was first built, or its condition prior to overlay 

for some experiments, was sometimes unknown, making it extremely difficult to consider this important 

information in analysis of the data. 

Nine pavement types or studies were originally 

planned for the GPS experiments. Preliminary work in 

these studies focused on finding pavement test sections meeting the defined criteria for each of the studies. Experimental matrices were developed to help 

encourage a distribution of primary experimental factors, such as layer thickness, traffic level, and subgrade 

type (figure 5.1). 

5: design and recruitment of the LTPP Experimen  

LTPP test site 331001 in New Hampshire (GPS-1: asphalt concrete on granular base). In the unique six-digit 

identifier, the first two digits indicate the State or Province where the test site is located.
66 HE LONG-T

It became clear from early efforts that many of 

the factorial combinations did not exist. Certain 

pavement types had not been built in some parts of 

the country, and highway agencies did not build 

relatively thin roadways for relatively heavy traffic. 

As a result of the initial section recruitment efforts, 

modifications to the GPS experiment plans were 

considered. After review, pavement experts and statisticians recommended changes to seven of the nine 

original experiments.

Evolution of the GPS Experiments 

Following review and discussion by the Advisory 

Committee with expert input from pavement engineers and statisticians, several changes were made to 

the GPS experiments. Table 5.1 outlines the basic 

experiments as originally called for, the changes recommended, and the decision to implement the changes by SHRP. Each experiment had sub-experiments 

not shown in table 5.1. For example, the variations in 

the design of asphalt concrete (AC) thickness, AC 

stiffness, and base and subbase characteristics were 

examined in the GPS-1 test sections (as shown in 

figure 5.1). Details of the design process and the final 

GPS designs are available in the SHRP 5-year and 

midcourse assessment meeting reports. 7,8,9

At subsequent meetings of the LTPP Advisory 

Committee, two other significant changes were made: 

•	 The minimum truck traffic requirement was relaxed to make finding 

suitable projects easier.

•	 The GPS-6 and -7 overlay experiments were split into two experiments each. One set, the 6A (existing

AC overlay of AC) and 7A (existing 

AC overlay of Portland cement concrete (PCC)) experiments, would 

include sections with existing overlays, where the condition prior to 

overlay was not known. The second 

set, 6B (planned AC overlay of AC)

and 7B (planned AC overlay of PCC),

would include sections where the

condition prior to overlay was known, 

which would make the information 

gained from this study much more 

valuable. In this way early results 

could be obtained, and later studies 

from overlays with known prior condition would provide stronger longterm understanding.

Later in the program, the GPS-6 and -7

overlay experiments were further divided as a result of the Program Assessment 

undertaken in 1996 (chapter 11). This

assessment determined that the program

lacked rehabilitation test sections and 

that this area of the program needed 

Figure 5.1. Example of the research matrices used to plan the

experiments (AC = asphalt concrete, SN = structural number).6 
5: design and recruitment of the LTPP Experimen  

Table 5.1. Evolution of the General Pavement Study experiment desig

Original GPS Experiments

Asphalt Concrete (

Over Granular Ba

AC Over Stabilized 

Jointed Plain Concrete

(JPC

Jointed Reinforced

Concrete (J

Continuously Reinforce

Concrete (

AC Overlay 

AC Overlay of Joint

Portland Cement Concret

(PC

Bonded Jointed Concrete

Pavement (JCP) Overlay o

JCP andCRC Pavem

Unbonded JCP Overlay 

JCP andCRC Pavem

Changes Recommended

• Non

• Expand acceptable base types and classif

as bituminous and nonbituminous.

• Expand acceptable binder type

• Include coarse-grained subgrade

• Add traffic level and subgrades as factor

• Remov AC stiffness as a fac

• Consider plant mix base

• Consider soil cement and sand asphal

• Consider pavements in dry–no freez

zone placed directly on subgrade.

• Non

• Add dry–no freeze region as a factor leve

• 

emove base type as a structur

factor and replace with percentage 

of reinforcement as the structural factor.

• Add condition of pavement before overla

as a factor in planned overlays.

• Delet AC stiffness as a design fac

• Combine dry–freeze and dry–no freeze int

one combined dry environmental zone.

• Eliminate JRC as original pavement

the dry environmental zone due to lack 

of projects.

• Add condition of pavement before overla

as a factor in planned overlays.

• Delet AC stiffness as a design fac

• Eliminate due to lack of project

• Delete traffic level, subgrade type

and original pavement condition as 

design factors.

• Allow overlay type as a structural facto

and RC pavement as an overlay ty

• Include both existing and planned overlay

• Accept virtually any project that fits th

title of the study.

Were Changes Implemented? 

No. Final experiment name

• GPS-: AC Pavements on Granular

Yes. In addition, the experiment was further

modified to allow delineation of asphalt-treated 

base and cement-treated base. Final experiment

name:

• GPS-: AC Pavements on Bound 

No. JPC placed directly on treated o

untreated subgrade was not permitted in 

the experiment. Final experiment name:

• GPS-3: Jointed Plain Concrete Paveme

No. Final experiment name

• GPS-4: Jointed Reinforced Concrete Pavem

Yes. Final experiment name:

• 

PS-5: Continuously Reinforced Co

Pavements.

Yes. The experiment was divided into existing

and planned overlays, and C stiffness wa

deleted as a factor. Final experiment name:

• GPS-: AC Overly of AC Pa

Yes. However, the dry environmental zones

were not combined, but JRC pavement wa

eliminated. The experiment was divided into

existing and planned overlays, and C stiffnes

was deleted as a factor. Final experiment name:

• GPS-: AC Overlay of PCC Pa

Yes. The SPS-7 (bonded PCC overlay

pavements) experiment was later formulated to 

address this rehabilitation alternative.

Yes. Final experiment name:

• 

PS-9: Unbonded PCC Over

Pavements.
68 HE LONG-T

the variation in experimental factors desired was 

actually achieved. SHRP program staff, assisted by 

the technical assistance contractor (later called “technical support services contractor”), reviewed the 

potential candidates and provided recommendations 

for acceptance or rejection of a candidate section. 

Once this was done and sections meeting the stated 

criteria were identified, the highway agencies were 

advised of the selections. Wherever there were multiple projects meeting needs of the same cell, the test 

sections were sorted and information was maintained 

for substitution if needed.

After the highway agencies identified the sections, 

the regional coordination office contractors made field 

trips to confirm section characteristics and to find and 

mark out 500-ft (152.4-m) sections for study (figure 5.2). 

These field trips were an eye-opening experience, as in 

many cases it was found that the actual section characteristics were vastly different from what was expected. 

In some cases, layer types and thicknesses varied, and 

in others the cut/fill transitions or traffic generators 

(on/off ramps or intersections) prevented the identification of suitable sections for study. During these field 

visits, cores were obtained at the ends of each section, 

to confirm layer types and thicknesses. Wherever possible, a section location was found, documented, 

marked out, and confirmed for study. 

Once the field visits were completed, the sections 

were re-sorted in the experiment matrices based on 

actual field conditions. This process resulted in many 

sections changing experiment cells. To fill in the cell 

gaps, additional sections were recruited and selected. 

In this iterative process, the GPS experiments were 

populated with test sections for study. Figure 5.3 

shows an example of a GPS sampling template used to 

populate the LTPP experiments. 

In the end, many cells were devoid of sections. 

Many of these empty cells had extreme criteria, for 

example, thin sections with high traffic and fine subgrade. These sections simply had not been built, since 

the highway agencies knew that they would fail in a 

short time. It was also found that certain pavement 

types did not exist in certain parts of the country, 

making the combination of pavement type and environmental zone difficult to achieve in some places. 

improvement. To remedy this deficit, it was decided 

that once a highway agency rehabilitated a test section 

to address safety or deterioration issues, the LTPP program would move the test section to one of the following GPS-6 or -7 sub-experiments,with the concurrence

and continued support of the highway agency:

•	 GPS-6C (AC overlay using modified asphalt of AC

pavement).

•	 GPS-6D (AC overlay on previously overlaid AC

pavement using conventional asphalt).

•	 GPS-6S (AC overlay of milled AC pavement using

conventional or modified asphalt).

•	 GPS-7C (AC overlay using modified asphalt on PCC

pavement).

•	 GPS-7D (AC overlay on previously overlaid PCC

pavement using conventional asphalt).

•	 GPS-7F (AC overlay using conventional or modified

asphalt on fractured PCC pavement).

•	 GPS-7R (concrete pavement restoration treatments

with no overlay).

•	 GPS-7S (second AC overlay, which includes milling

or geotextile application, on PCC pavement with 

previous AC overlay).10

RECRUITMENT AND SELECTION OF GPS 

TEST SECTIONS

In the recruitment of GPS test sections, participating 

highway agencies were advised of the section needs 

and asked to review their records for pavements 

meeting the study criteria. Agency personnel 

reviewed many potential roadways to find sections 

that met the needs of the program and submitted 

them to their respective LTPP regional coordination 

office contractor (later called “regional support contractor”) for consideration. The LTPP regional coordination office contractors were firms with expertise 

in pavement monitoring and testing. Under SHRP 

management of the LTPP program, a SHRP regional 

engineer was also assigned to each regional office. 

The SHRP regional engineer and the regional coordination office contractor staff sorted the candidate sections into the experimental matrices to ensure that 
5: design and recruitment of the LTPP Experimen  

DESIGN OF SPS EXPERIMENTS

The GPS experiments were to be augmented by 

research into the impact of specific design features 

in the SPS experiments. The two study types share a 

symbiotic relationship, in that the findings from each 

complement the other. The primary difference in the 

two is that the SPS experiments generally involve some 

type of construction and tighter control of experimental parameters. Construction focused on providing 

specific design features for study, such as drainage 

features, layer thicknesses, base types, or treatment 

prior to rehabilitation. It was recognized that in some 

cases SPS results would take longer to realize, but the 

insights offered would be worth the wait. 

Consequently, some GPS experimental cells were 

destined to remain empty. Some of these needs could 

be addressed through the SPS experiments, where 

sections would be constructed, but in other cases, 

there was no practical way to address the gap.

Later in the program, as the pavement performance 

of some of the test sections began to decline and highway agencies needed to restore performance through 

rehabilitation activities, many of the pavements in the 

flexible (GPS-1 and -2) and rigid (GPS-3, -4, and -5) 

experiments moved to the GPS-6 (AC overlay of AC

pavement) and GPS-7 (AC overlay of PCC on concrete 

pavements) experiments after rehabilitation. Continued monitoring of these sections provided ample data 

before and after rehabilitation.

Figure 5.2. Designated layout for GPS test sites.11 Figure 5.3. Sampling template and cell ident

numbers for GPS-1 (asphalt concrete on granular base).12
70 HE LONG-T

Efforts began with a “shopping list” of potential 

studies, gathered over a period of time. In the original 

plans for the SPS experiment designs, 18 general topics 

were selected for intensive experiments for flexible 

and rigid pavements, and design matrices were formulated for many of them in the Strategic Highway 

Research Program Research Plans (“Brown Book”) (see

example in figure 5.4).13

The SHRP technical assistance contractor developed preliminary designs based 

on the matrices and details presented in 

the Brown Book. The preliminary designs

were reviewed by a working group that 

included representatives from highway 

agencies, FHWA, SHRP, and the contractors. Drawing on the observations of the 

working group, the SHRP contractors then 

prepared a draft design, and the draft was 

presented in study workshops for review 

by representatives of State and Provincial 

highway agencies, the pavement industry, 

and FHWA. As many as 26 highway agencies were represented in the study workshops, and the recommendations from the 

workshop reviews were incorporated in 

the final experimental designs.14

Evolution of the SPS Experiments 

In 1987, an effort was undertaken to reduce 

the number of original SPS design plans 

and to define the methods required to analyze the data from each. At that time a decision was made to divide the SPS into five 

major categories: Structural Factors, Preventative Maintenance, Pavement Rehabilitation, Environmental Factors, and Load 

Equivalencies. These major categories 

were further subdivided into specific 

experiments (table 5.2). 

During 1989 and 1990, a number of analytical studies were undertaken to further 

define the SPS experiment designs. In particular, Strategic Pavement Design Initiatives for SPS-1 (structural factors for flexible 

pavements) and SPS-2 (structural factors 

for rigid pavements) were considered, and the value of 

sub-experiments to explore and isolate the relative 

effects of different factors and combinations of factors 

was investigated. These investigations led to the development of experiment designs and research plans for 

SPS-1 and SPS-2. During the same time, guidelines were 

developed for nomination and evaluation of candidate 

projects for SPS-5 (rehabilitation for asphalt concrete 

Figure 5.4. Example of the research design matrices created

the Specific Pavement Study experiments (JCP = jointed concrete 

pavement; AC = asphalt concrete; JRCP = jointed reinforced 

concrete pavement).15
pavements), SPS-6 (rehabilitation of jointed concrete

pavements), and SPS-7 (bonded PCC overlays). Ultimately, a suite of guidelines was developed—for nomination and evaluation, data collection, material 

sampling and testing, and construction—for each of the 

SPS experiments. 

Concurrent with the development of the LTPP 

GPS and SPS experiments, the asphalt research area 

under SHRP was developing the Superpave® mix 

design method. Once the method was developed and 

ready for field implementation, it was deemed prudent to study the performance of the new mix designs 

in the field in controlled experiments. In the 1990s, 

the SHRP Asphalt Research Group worked with the 

LTPP program to develop an SPS experiment (SPS-9: 

Validation of Strategic Highway Research Program 

Asphalt Specification and Mix Design (Superpave®))

for the long-term study of performance of the Superpave mixtures. This experiment design included 

placement of three test sections: a control section 

using the highway agency’s normal mix design, a section with a Superpave mix designed for the climate in 

question, and a section with a Superpave mix designed 

one grade lower than optimum. The Superpave projTable 5.2. Evolution of the Specific Pavement Study experiment desig

Original SPS Experiments Changes Recommended Were Changes Implemented? 

• Asphalt Concrete (AC) Subdrainage Structural Factors Yes. Resulted in two exper

• New Concepts for Flexible Pavements • Study structural factors for • SPS-1: Strategic Study of

• Portland Cement Concrete (PCC) flexible and rigid pavements. actors for Flexible Pav

 Subsurface Drainae  • SPS-2: Strategic Study of S

• High-Strength PCC    Factors for Rigid

• PCC Shoulder Des

• PCC with Non-Erodible High-Str

Bases

• New Concepts for Rigid Paveme

• AC Preventive Maintenance Preventive Maintenance No. Preventive maintenance st

• PCC Preventive Maintenance • None. were given specific n

 • PS-3: Preventive Mainten

Effectiveness of Flexible Pavement

 • PS-4: Preventive Mainten

Effectiveness of Rigid Pavement

• AC Hot Recycling Pavement Rehabilitation Yes. Resulted in three experi

• AC Cold Recycling • Hot Recycling of AC. • SPS-5: Reha

• Pretreated Jointed Concrete Pavement • Restoration and Overlayof  Pavemen

(JCP) withAC Overlay Jointed PCC Pavement. • SPS-6: Rehabilitation 

• PCC Retrofit Shoulder • Bonded PCC Overlay of PCC  P

• PCC Restored JCP Pavement. • SPS-7: Bonded PCC Ov

 Pavements.

• AC Environmental Distress Environmental Factors Yes. Resulted in one exper

• PCC Environmental Distress • Study environmental effects on • SPS-8: Study of En

• AC Low-Volume Roads pavements under light loads. 

ffects in the Absence

 • Each test site location to includ  Loads

 two flexible and two rigid 

 pavement sections.

• AC Load Equivalence Factors Load Equivalencies No. At the time, separating 

• PCC Load Equivalence Factors • None. to study true load equivalencie

impractical, so the experiment was 

not considered beyond the conceptual 

phase in spite of the perceived relative 

importance of the result. 

5: design and recruitment of the LTPP Experimen  
72 HE LONG-T

ects were both new construction and rehabilitation 

projects that covered an array of asphalt aggregate 

mixture specifications and were recruited consistent 

with the methods used to find sites for the other SPS 

experiments.16 The data were collected as part of the 

LTPP program and stored in the database.

Supplemental SPS Test Sections 

Unlike the GPS test sections, highway agencies were 

permitted to construct supplemental sections for all 

SPS projects, in addition to the core experimental sections to monitor factors specific to their agency. Two 

such examples are described in the sidebar. Data from 

these supplemental sections are collected as part of the 

LTPP program and included in the database.

RECRUITMENT AND SELECTION OF SPS 

TEST SECTIONS

Recruitment of sites for the SPS test sections was even 

more involved than for the GPS sections. For the SPS 

experiments, the test sections were to be constructed, 

meaning that suitable projects and a commitment from 

the highway agency to incorporate special provisions 

for construction into a planned project had to be 

obtained. The SPS sections also differed in that each 

SPS project incorporated several test sections at a location. Given the complexity of the studies and the 

importance of the results, intensive planning was 

required. Because of these requirements, and because

agencies must work construction activities into their 

existing programs, some SPS projects were constructed as late as 2000.

Although the SPS experiments had been generally 

defined, construction details had not been finalized to 

the point that construction documents could be developed from them. A series of national meetings was held 

in the late 1980s to obtain input from all of the involved 

partners and to develop draft construction guideline 

documents for each of the high-priority SPS experiments: SPS-1, -2, -5, and -6. (The final guidelines are

listed in table 9.1.) These particular experiments were 

considered high priority because they were new sites 

with specific design and construction criteria to meet a 

particular research need for the LTPP program. The 

other LTPP experiments were just as important to the 

overall goal of the program, and were equally imporMany highway agencies chose to construct supplemental sections on SPS projects. Recognizing the 

value of consistent long-term monitoring on these 

sections, a variety of approaches were taken in their 

design. For example, many agencies used their standard mix design and structural section on the pavement adjacent to the 12 core sections on an SPS-2 

project to compare the performance of their standard 

practice with that of the core sections. 

The Arizona Department of Transportation took 

this strategy a step further and constructed nine supplemental sections that examined alternative joint 

configurations, structural sections, and even pavement types. The department is currently studying the 

performance, after 20 years, of the supplemental 

sections relative to each other and to the core sections—recognizing that all 21 sections are still in the 

study and there is more to be learned going forward.

Typical variations between the core sections and 

supplemental sections involve changing material 

properties, structural thicknesses, and design properties (e.g., lane width). In another example of supplemental sections, several States in the western part of 

the country—Arizona, California, Colorado, Nevada, 

and Utah—collaborated on a study of joint sealants as 

part of the SPS-4 experiment. This study included 

more than 100 supplemental sections. As future SPS 

projects are constructed, the opportunity to include 

supplemental sections is an excellent incentive for 

participation on the part of highway agencies.

Agences’ Use o
tant in meeting the program’s objectives. 

SHRP program staff and the LTPP technical assistance contractor gathered all of the 

input and worked this information into 

comprehensive construction guidelines 

that highway agencies could use to develop 

project plans. These documents also served 

as the basis for the project recruitment 

guidelines, since they essentially outlined 

project needs. The guidelines generally 

covered nomination and evaluation, data 

collection, materials sampling and testing, 

and construction. The guidelines also provided clear instruction for field activities 

and data forms for recording required 

information through the site evaluation 

and construction process. An example of 

an SPS test section layout for SPS-1 and -2 

is shown in figure 5.5. It is important to 

note, however, that the number of test sections monitored for other SPS experiments 

may differ from what is shown.

The other SPS experiments that were 

new construction included SPS-8 (environmental factors in absence of heavy loads) 

and some SPS-9 sites. SPS-3 and -4 were 

maintenance studies of flexible and rigid 

pavements, respectively, and SPS-7 and some SPS-9s 

were overlays. All of these experiments followed a 

similar but less restrictive process of nomination and 

construction than the high-priority SPS experiments. 

On the high-priority sites, deviations from the design 

and construction guidelines were not permitted. 

The project nomination and screening process was 

organized and methodical, designed to select the best 

candidates for study from the available construction 

projects. Test section locations were to be selected to 

minimize or avoid altogether transitions from cut to fill 

or unusual variations in distress along the project 

length. On ramps, off ramps, or other traffic generators 

were also to be avoided. With these and other considerations to be met, selection of projects became a challenging task. Still, in the end, recruitment and selection 

efforts resulted in a majority of the required experiment design needs being filled.

In response to feedback from highway agencies 

regarding concerns about increased costs for items such 

as traffic control needed during field testing, collection 

of traffic data, and costs associated with more detailed 

materials testing, FHWA agreed to monetary incentives 

for agency participation in the construction of SPS projects. Agencies were provided $50,000 for each SPS-1 or 

SPS-2 project they constructed and $35,000 for each 

SPS-5 or SPS-6 project they constructed. The roles and

responsibilities of the highway agencies had to be understood and agreed to, as part of the data collection 

requirement fell on their shoulders (mainly materials 

testing and monitored traffic data collection). 

With all of these pieces in place, highway agencies 

started the process of identifying projects best suited 

to the construction for the SPS test sections. This process was a slow one, starting in about 1989 and ending 

in about 2000. Suitable projects were identified, construction plans developed and altered to include the 

5: design and recruitment of the LTPP Experimen  

Figure 5.5. Test section layout for SPS-1 and SPS-2 proj

(Strategic Studies of Structural Factors for Flexible and Rigid 

Pavements, respectively).17
74 HE LONG-T

test sections, and specifications developed for pay 

items not part of normal agency practice (e.g., permeable asphalt-treated base). 

Construction coordination frequently involved participation of the LTPP regional coordination office 

contractor in a pre-construction meeting with the 

agency staff and its contractor to discuss the importance of the experimental test sections and adherence 

to the plans and specifications. Agreement also had to 

be reached on the function of the LTPP regional coordination office contractor staff on site, typically during 

the construction process, to monitor the progress and 

record key pieces of information during construction. 

In many ways this was a difficult process for highway 

agency construction contractors to understand, and 

success depended on their, as much as the agency’s, 

understanding and accepting the requirements. 

The need for monitoring of the original SPS experiments continues into the future. In addition, the LTPP 

program is adding new SPS experiments to address 

21st century pavement needs, such as warm-mix 

asphalt concrete (SPS-10) and the monitoring of pavement preservation treatments. 

LTPP EXPERIMENTS AND 

TEST SECTION LOCATIONS

The new experiments that were ultimately designed 

for the program are listed in table 5.3. The test sections 

cover a broad spectrum of pavement types. The evenFigure 5.6. Locations of the 2,509 pavement 

sections across the United States, Puerto Rico, and 

Canada: 791 in the General Pavement Studies (GPS) 

and 1,718 in the Specific Pavement Studies (SPS) over 

the course of the LTPP program. In 2014, 372 GPS and 

360 SPS test sections were still being monitored.

tual distribution of test sections across the United 

States and Canada, including Puerto Rico and the District of Columbia, is shown in figure 5.6.

SUMMARY

Establishing the LTPP experiments and selecting the 

appropriate test sections was not an easy task for those 

involved. However, the data that have been collected 

and the results obtained, as will be discussed later in 

Table 5.3. LTPP General and Specific Pavement Study experimen

General Pavement Study (GPS) Experiments Specific Pavement Study (SPS) Experiments

GPS-1  Asphalt Concrete Pavements on Granular

GPS-2 Asphalt Concrete Pavements on Bound 

GPS-3 Jointed Plain Concrete Pavemen

GPS-4 Jointed Reinforced Concrete Paveme

GPS-5  Continuously Reinforced Concrete Pave

GPS-6  sphalt Concrete Overlay of Asphalt 

Pavements 

GPS-7  sphalt Concrete Overlay of Portland

Concrete Pavements

GPS-8 Bonded Portland Cement Concrete Ove

(discontinued, later replaced by SPS-7

GPS-9  nbonded Portland Cement Concrete 

of Portland Cement Concrete Pavement

SPS-1  trategic Study of Structural Factors for Flexible P

SPS-2  trategic Study of Structural Factors for Rigid P

SPS-  Preventive Maintenance Effectiveness of Flexible Pavem

SPS-  Preventive Maintenance Effectiveness of Rigid Pavem

SPS-5  ehabilitation of Asphalt Concrete Pav

SPS-6  ehabilitation of Jointed Portland Cement Co

Pavements 

SPS-  Bonded Portland Cement Concrete Overlay of Port

Cement Concrete Pavement

SPS-8  tudy of Environmental Effects in the Absence 

Loads 

SPS-  Validation of Strategic Highway Research Program As

Specification and Mix Design (Superpa

SPS-10 Warm-Mix Asphalt Overlay of Asphalt Pavements 
this report, have been worth the effort. The careful 

planning, close collaboration among the LTPP program, highway agencies, industry, and contractor staff, 

and careful attention to the design details of the experiments have resulted in a sound research program that 

continues today. The following chapter covers the 

types of data collected at the LTPP test sections, the 

collection methods, and the equipment and instrumentation used since the beginning of the program.

R

1. Strategic Highway Research Program Research Plans, Final 

Report. TransportationResearchBoard, NationalResearch

Council, Washington, DC, May 1986, p. TRA 2-11.

 2. W. O. Hadley. SHRP-LTPP General Pavement Studies: 

Five-Year Report (SHRP-P-387). Strategic Highway 

Program Research Program, National Research Council, 

Washington, DC, March 1994, pp. 2, 4–30. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-387.pdf.

 3. A. N. Hanna with S. Tayabji and J. S. Miller. SHRPLTPP Specific Pavement Studies: Five-Year Report

(SHRP-P-395). Strategic Highway Program Research 

Program, National Research Council, Washington, DC, 

April 1994, pp. 9–30. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-395.pdf.

 4. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Program Research

Program, National Research Council, Washington, DC, 

June 1994, pp. 7–76. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-416.pdf.

 5. G. Elkins. “The GPS Experiments as Implemented.” 

Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991, 

p. 4. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-91-514.pdf. 

	 6.	Strategic Highway Research Program Research Plans, Final 

Report. TransportationResearchBoard, NationalResearch

Council, Washington, DC, May 1986, p. TRA 2-42.

 7. W. O. Hadley. SHRP-LTPP General Pavement Studies: 

Five-Year Report (SHRP-P-387). Strategic Highway 

Research Program, National Research Council, 

Washington, DC, March 1994. http://onlinepubs.trb.

org/onlinepubs/shrp/SHRP-P-387.pdf.

 8. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Program Research

Program, National Research Council, Washington, DC, 

June 1994, pp. 7–40. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-416.pdf.

 9. G. Elkins. “The GPS Experiments as Implemented.” 

Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991, 

pp. 3–8. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-91-514.pdf.

 10. Long-Term Pavement Performance Information 

Management System Pavement Performance Database 

User Reference Guide (FHWA-RD-03-088 (Update)). 

Federal Highway Administration, McLean, VA, 

September 2013. http://www.ltpp.org/IMSUserGuide

2013.pdf. 

 11. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Program Research

Program, National Research Council, Washington, DC, 

June 1994, p. 28. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-416.pdf.

 12. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Program Research

Program, National Research Council, Washington, DC, 

June 1994, p. 11. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-416.pdf.

 13. Strategic Highway Research Program Research Plans, 

Final Report. Transportation Research Board, National

Research Council, Washington, DC, May 1986, pp. TRA

2-55–TRA 2-95.

 14. A. N. Hanna with S. Tayabji and J. S. Miller. SHRPLTPP Specific Pavement Studies: Five-Year Report

(SHRP-P-395). Strategic Highway Program Research 

Program, National Research Council, Washington, DC, 

April 1994, p. 9. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-395.pdf.

 15. Strategic Highway Research Program Research Plans, Final 

Report. TransportationResearchBoard, NationalResearch

Council, Washington, DC, May 1986, p. TRA 2-81.

	16.	R. S. McDaniel, R. B. Leahy, G. A. Huber, J. S. Moulthro

and T. Ferragut. The Superpave Mix Design System: 

Anatomy of a Research Program (NCHRP Web-Only 

Document 386). National Cooperative Highway Research

Program, Transportation Research Board of the National

Academies, Washington, DC, August 2011. http://

onlinepubs.trb.org/onlinepubs/nchrp/nchrp_W186.pdf.

 17. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Program Research

Program, National Research Council, Washington, DC, 

June 1994, p. 44. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-416.pdf.

5: design and recruitment of the LTPP Experimen  
76    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The challenge in LTPP data collection is to capture research-quality data of 

diverse types using highly specialized, state-of-the-art equipment with 

the involvement of many people across different geographical areas.
6: coction o

Collection of the LTPP Data

6

Introdu

LTPP data collection focuses on understanding the 

performance of pavements from a mechanistic engineering perspective—the attempt to define a structure’s performance by modeling the factors that lead 

to performance degradation and the need for maintenance, rehabilitation, or reconstruction. Figure 6.1 

illustrates the relationships between data collection 

categories for mechanistic-based pavement performance modeling. Climate and traffic loading are two 

primary factors affecting a pavement structure’s 

performance. Climate affects mainly the properties of 

the materials contained in the pavement structure. 

Traffic loads are directly supported by the pavement 

structure. Traffic loads and climate create responses 

in the materials contained in the pavement structure 

Since 1989, millions upon millions of discrete data have been gathered and collected from pavement test 

sections across North America by highway agency personnel and the LTPP program through its contractor 

staff using a myriad of methods and equipment. The procedures and equipment used in the collection 

process were subject to careful planning and systematic quality controls designed to ensure that the 

data would be as consistent, comparable, and useful as possible for future research.

and subgrade that lead to various forms of distress. 

The data collection design for the LTPP program 

aims to measure, characterize, and quantify the factors that explain how and why a pavement performs 

as it does.

 Providing high-quality data is of paramount importance to the LTPP program. Thus, collecting data with 

careful quality control/quality assurance (QC/QA) 

processes in place has been and continues to be a primary focus of the program (chapter 9). This chapter 

describes the development of LTPP’s data collection 

procedures. The key data collection activities that have 

been adopted and continuously refined over the course 

of the program are the following:

•	 Maintaining data collection procedures, guides, and

protocols.
78    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 Ensuring that personnel in different geographic regions receive the same data collection and process 

training.

•	 Using properly maintained and calibrated state-ofthe-art equipment.

•	 Training personnel to correctly use the equipment

and meticulously follow procedures.

•	 Documenting problems to provide input, feedback,

or answers for enhancing data collection efforts or 

for future data analysis work.

•	 Tracking all efforts to ensure that data are not lost

nor efforts wasted and to allow steps to be retraced 

should issues develop.

•	 Checking, inspecting, and following up to ensure

that data are of high quality.

Key Milestones in Data Collection

1987 First edition of Distress Identification 

Manual published

1987 Inventory data collection begin

1988 First manual distress survey performed

1988 First FWD equipment purchase

1989 FWD Operational Field Guidelines

published

1989 FWD data collection begin

1989 First inertial profiling equipment purchased

1989 First automated distress surveys (PASCO) 

performed

1991 First FWD calibration protocol publishe

1991 First manual distress workshop conducted

1992 First FWD calibration center open

1992 Climate data collection begins

1994 Automated Weather Station 

installations begin

1994 Global Positioning System units purchased

2001 LTPP SPS Traffic Data Collection PooledFund Study initiate

2003 GPR study of SPS test section layer 

thicknesses conducted

2003 FWD maintenance and overhaul

manual developed

2004 FWD Calibration Center and Operational

Improvements Pooled-Fund Study initiate

2005 GPS data updated for test sites, weather 

stations, and weigh-in-motion scales

2008 Automated Weather Station data 

collection phase-out begins

2009 LTPP protocols adopted for AASHTO 

FWD calibration standar

2010 Operation of FWD calibration centers

transferred to AASHTO MRL

2011 FWD calibration protocol update

2013 FWD equipment and software upgrade

2013 Profiling equipment and software 

upgraded

2013 Climate data upgraded

2014 Fifth edition of Distress Identification 

Manual published

Who Collects the Data?

The data collection processes have involved both the 

highway agencies and the LTPP program’s contractors. 

The highway agencies agreed to collect the materials 

and traffic data as well as friction data. In some cases, 

the highway agencies were not able to provide all of the 

data needed by the LTPP program to perform critical 

data analysis projects or studies. Therefore, the program initiated special data collection efforts such as 

the Materials Action Plan and the LTPP Specific Pavement Study Traffic Data Collection Pooled-Fund Study

to collect these critical data elements (chapter 7). 

The remaining pavement-related data were collected 

by LTPP’s contractor staff: regional support contrac-© mexrix/Shutterstock.com
6: coction o

The source, type, method of capture, quality, and quantity of the 

different data elements are quite 

varied. With the exception of the 

Administration module, which contains no performance-related data 

and therefore is not discussed here, 

the remainder of this chapter 

describes each of the LTPP database modules and its associated 

data element(s). 

It is important to mention that 

LTPP data are also used to develop 

special data sets. One example is 

the Mechanistic-Empirical Pavement Design Guide (MEPDG) data sets, used by highway agencies to calibrate the design models for their 

local pavement conditions. The MEPDG data sets,

which are part of the Traffic data module, are computed data. Nearly all of the LTPP data modules have 

computed data—not collected or measured data—

such as dynamic load response data, falling weight 

deflectometer backcalculation, and equivalent single-axle load values. Also, the SPS data module actually refers to inventory data for the SPS projects (as

discussed later in this chapter).

tors, the technical support services contractor, equipment vendors, and service contractors. 

Data QC was integral to data collection activities.

Each regional support contractor is required to have a

Quality Control Plan and Working Guide covering all

aspects of data collection and review. The plan must be 

implemented and maintained. Through the years, the 

LTPP program has managed quality issues using various mechanisms such as unannounced field or office 

visits to observe data collection and processing procedures, conference calls, Data Analysis and Operations

Feedback Reports, Operational Problem Reports, and 

Software Problem Reports.

What Types of Data Are Collected?

The different data types described in this chapter are 

collected at both the General Pavement Study (GPS)

and Specific Pavement Study (SPS) experiments with

few exceptions. Early in the LTPP program, most of

the data elements were collected annually. However, as 

the funding levels for the program were reduced, the 

frequency of data collection was reduced.1,2 Some data

elements have been collected more frequently for certain LTPP experiments, but nearly all of the experiments have annual monitoring data (e.g., distress, 

deflection, profile) in addition to inventory, and maintenance and rehabilitation data. These data elements 

are stored in the LTPP database in tables that are organized by modules, listed in table 6.1. 

Figure 6.1. LTPP data collection categories

Table 6.1. LTPP database modules (circa 2014

Database Modul

Administration (ADM

Automated Weather Station (AWS)

Climate (CLM)

Dynamic Load Response (DL

Ground Penetrating Radar (GPR)

Inventory (as-built) (IN

Maintenance and Rehabilitation (MNT and RHB)

Materials Testing (TST)

Monitoring (MON)

• Deflection (MON_DE

• Distress (MON_

• Drainage (MON_DR

• Friction (MON_FRICTIO

• Profile (MON_PROFILE

• Rutting (MON_RUT)

• Transverse Profile (MON_T_PROF)

Seasonal Monitoring Program (SMP)

Specific Pavement Studies (SPS) Inventor

Traffic (TRF)
80    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

AUTOMATED WEATHER ST

Automated weather station (AWS) data collected

from the LTPP test sections include site-specific 

weather information: air temperature, humidity, 

precipitation, solar radiation, wind direction, and 

wind speed. To understand the influence of various 

environmental conditions on the performance of a 

specific type of pavement, one must first learn what 

those conditions are. 

Weather stations with remote data collection 

capabilities were installed at newly constructed SPS-1

(structural factors for flexible pavements), -2 (structural factors for rigid pavements), and -8 (environmental effects in the absence of heavy loads) projects. At 

some locations, particularly in Delaware, Nevada,

Ohio, andWisconsin, multiple SPS projects were located within a short distance of each other, reducing the 

number of weather stations required. Thus, it was cost 

beneficial to install a single AWS at these study sites.

The weather stations collected data at 15-minute 

intervals: air temperature, relative humidity, precipitation, solar radiation, and wind speed and direction. 

These data were accumulated into hourly, daily, and 

monthly statistics. Measurements began in August

1994 and continued through December 2008, with the

start and end of data collection varying from one 

weather station to another. The automated weather 

stations were also intended to validate the data from 

the virtual weather stations (discussed in the climate 

data section).

Before data collection began, a review of commercially available weather stations was conducted, after 

which aCampbell Scientific, Inc.(CSI) unitwas selected

and installed on the grounds of the Federal Highway 

Administration (FHWA) research center for further 

evaluation. During the evaluation period, the LTPP

technical support services contractor developed an 

automated weather station manual covering the installation of the weather stations, data collection, and 

maintenance.3

 The initial training for installation 

occurred near Phoenix, Arizona, in July 1994. In 

September 1994, the LTPP program issued a directive

(a written communication circulated program-wide to 

ensure uniformity in data collection) for its contractors 

to follow that described the installation, data collection, and maintenance activities required for the 

weather station.4 As weather station activities changed, 

the program issued subsequent directives to update 

procedures and complement or change instructions 

provided in the AWS Installation and Data Collection

Guide.5 These directives covered such topics as parts 

replacement, sensor calibration, remote data collection, and preventive maintenance plans.

The weather instrumentation and equipment were 

centrally purchased by FHWA and shipped to the 

LTPP regional support contractors to install at the SPS

sites. In addition to providing the instrumentation, the 

LTPP program also performed the data collection and 

maintenance activities through the regional support 

contractor staff. The highway agency sponsoring 

the site provided the concrete pad for the weather 

tower, the tipping bucket base, and compound fencing 

(figure 6.2). In most cases, telecommunication and 

Figure 6.2. Complete automated weather statio

installation with protective fencing.

Data collection for the LTPP program 

aims to measure, characterize, and 

quantify the factors that explain how 

and why a pavement performs as it does. 

Consequently, data collection was 

established to support the envisioned 

data analyses and product development.
6: coction o

power costs were assumed by the highway agency. See

appendix C for more information on the type of AWS

equipment and software used to collect, store, and process the weather data.

AWS Maintenance Issues

Maintenance became a major issue for the weather stations. One of the problems encountered at the weather 

stations was the tipping buckets would become clogged 

with various types of debris. Similarly, the relative

humidity probe filter would become plugged, retain 

moisture, and provide false high readings. Remote 

access was often an issue, as the modems used to connect the dataloggers with the LTPP regional support 

contractor’s office computers were prone to lightning 

damage. The onsite storage modules were also prone 

to data retrieval problems that required returns to the 

office for data extraction. 

Site visits were needed more frequently than had

been anticipated. Maintenance was performed on the

weather stations every 2 years, and exchange of instrumentation was part of the maintenance procedure. In 

addition, when collecting other LTPP data elements at 

a site, the regional support contractors visited the 

weather stations to inspect the equipment and perform 

minor maintenance (such as unclogging a tipping bucket rain gauge). However, at some locations, the highway 

agencies assisted with minor maintenance. Any instrumentation that needed to be returned to the regional 

support contractor’s office was checked for accuracy 

using the manufacturers’ guidelines. Out-of-tolerance 

instruments were either calibrated in-house (figure 6.3) 

or returned to the manufacturer for calibration. Most of

the regional support contractors purchased equipment 

and spare parts for servicing the tipping bucket rain 

gauges and the wind monitors, but preferred to return 

the relative humidity/air temperature probe units and 

pyranometers to the vendor for calibration. In addition 

to maintaining the instrumentation, there was often a 

need to service the dataloggers, storage modules, and 

modems or to replace batteries. 

AWS Quality Control Programs

Two DOS-based programs were developed to check

the quality of the AWS data. The first was AWSScan,

which performed basic data checks in the field including range, time-series consistency, and required data 

elements. One of the key functions of the AWSScan

program was to make sure the measurement equipment was operating properly and alert the field technician to potential issues that could be corrected in the 

field. AWSScan was used at the time data were being

downloaded, whether onsite or remotely. The second 

program, AWSCheck, was developed for office processing purposes and was used to combine raw data 

files, edit/remove invalid data, allow for time stamp 

corrections (that correspond with standard/daylight 

saving time), view additional graphical outputs for 

time-series consistency and logical ordering of climate 

statistics (i.e., maximum ≥ average ≥ minimum), generate upload files for entry into the LTPP database, recompute daily statistics when bad hourly measurement 

values were deleted, and replicate the QC checks that 

would be performed after the data had been uploaded 

Figure 6.3. Prototype automated weather station use

by the LTPP regional support contractors for in-house

training of staff and to calibrate equipment components.
82    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Because the LTPP test sites were not typically colocated with operating weather stations, it was necessary to extract data from nearby operating weather 

stations and, using a distance-weighted averaging function, create virtual weather statistics for each LTPP test 

site. One of the first steps in creating a virtual (i.e., statistical) weather station was to identify up to five operating weather stations (see example in figure 6.4) that met 

the following criteria in the order listed: 

1. Type of station, first order stations being preferred 

over cooperative stations.

2. Operating weather station(s) coverage time period 

relative to the pavement test section construction 

date.

3.	 Distance between the test site and operating weather station(s).

4.	 Elevation difference between the test site and operating weather station(s).

5. Location of mountains. 

6.	 Microclimate effects.

In the early years of the program, the services of a 

climate specialty contractorwere used to obtain NCDC

and CCC data, perform initial weather station selection based on the above criteria, and provide daily data 

from the operating weather stations to the LTPP program in ASCII format. Subsequent processing created

the daily, monthly, and annual summaries for the virtual weather stations. 

into the database. The time stamps needed adjustment 

because the time in the dataloggers did not change 

with standard/daylight saving time. All of the AWS

data in the database are in local time (based on the

location of each station’s time zone). User guides for

AWSScan and AWSCheck were developed in 1995 and

1996, respectively.6

Decision to Decommission AWS

The LTPP automated weather stations received regular maintenance and instrumentation replacement at 

2-year intervals until 2006, when the decision was

made to continue servicing only those stations that 

could be maintained with minimal investment of time 

and expenditure. As stations started to require maintenance due to component failure, they were dismantled 

or turned over to the respective highway agencies. 

Phase-out was completed in December 2008, and all

sites were decommissioned. At the conclusion of the 

AWS data collection activities, 9 to 13 years of weather

data had been collected from the SPS-1, -2, and -8 projects and stored in the LTPP database. 

CLIMATE DATA—VIRTUAL 

STATIO

Unlike the AWS data which cover detailed data for a

subset of the LTPP test sections, the climate data—

precipitation, temperature, wind, and humidity—

cover all test sections. The climate conditions at the 

GPS and SPS test sites have been obtained from the

United States National Climatic Data Center (NCDC)

and the Canadian Climate Center (CCC). The climate 

module includes data from both operating weather 

stations and “virtual” weather stations. However, 

efforts are underway to improve the coverage, completeness, and quality of the LTPP climate data 

through the use of Modern Era-Retrospective Analysis for Research and Applications (MERRA)7

 data 

from the National Aeronautics and Space Administration (NASA). These efforts are still ongoing, and

hence the focus of this section is on the legacy 

approach that relied on NCDC and CCC data.

Figure 6.4. A virtual weather station (VWS). Thi

example shows the locations of five operating weather

stations used to create the VWS for GPS section 8318

on Trans-Canada Highway 1 in southwestern Manitoba.

(Source: Esri, Digital Globe, i-cubed, Earthstar Geographics, CNES/Airbus 

DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, Swisstopo, and 

the GIS User Community; created in ArcGIS 10.1)
6: coction o

The climate data provided by the LTPP program 

are “computed parameters.” In other words, they are 

estimates derived from measured values. Daily statistics (temperature, rainfall, wind speed, and humidity) 

are obtained from the operating weather stations and 

subjected to range and logic checks as defined in the 

LTPP QC Manual.8 Only data passing all data checks 

are used to compute the daily virtual weather station 

statistics. The daily statistics are aggregated into 

monthly and annual statistical summaries. Automated QC checks are performed on the monthly and 

annual statistics to verify reasonable ranges and logical relationships.

The last update of the climate data was performed 

in 2013 and included data through 2012, the most upto-date data available at the time. This update used the 

rawdata collected from theNCDCandCCC.TheLTPP

program has also incorporated into the Climate module data from NASA’s MERRA project, which provides

much finer spatial resolution and offers more data elements that can be implemented without the use of virtual weather station interpolation concepts.

DYNAMIC LOAD RESP

The LTPP database contains data that measure the

pavement response under controlled loading conditions for two SPS projects. These data, known as

dynamic load response or DLR data, were collected in

North Carolina and Ohio from 1996 to 1997. 

In North Carolina, four Portland cement concrete 

(PCC) pavement sections at the SPS-2 project were

instrumented to collect DLR data. In Ohio, asphalt

concrete (AC) and PCC pavement test sections from 

the SPS-1 and SPS-2, respectively, were instrumented

to monitor the DLR of vehicles with known weights.

Three types of instrumentation were installed at the 

project sites: 

•	 Instruments to measure pavement response including

vertical displacements, vertical pressures, and strains 

at selected locations within the pavement structure.

•	 Instruments to collect environmental data such as

temperature with depth, moisture content of the 

various pavement layers, water table depth, and 

frost/thaw depth (i.e., the same subsurface moisture 

and temperature equipment installed at the LTPP 

test sections making up the Seasonal Monitoring

Program (SMP)). The only LTPP test section instrumented with environmental condition sensors was 

test section 370201 in North Carolina.

•	 Instruments to collect air temperature, precipitation

(rain and snow), wind speed, wind direction, relative 

humidity, and incoming solar radiation as described 

in the section on AWS.

Thus, at each project site, a comprehensive set of data 

was collected—DLR measurements within the pavement and on the pavement surface, subsurface moisture 

and temperature conditions, and ambient conditions.

Results of the DLR initiative are discussed in LTPP 

Data Analysis: Influence of Design and Construction 

Features on the Response and Performance of New Flexible and Rigid Pavements.9 The North Carolina DLR

data are included in the LTPP database. An update and 

reinterpretation of the DLR data collected between

1996 and 1997 from the SPS-1 and -2 sites in Ohio were

made available in the LTPP database starting in 2013.

GROUND PENETRA

Pavement structure is one of the four primary factors 

whose separate and combined effects influence the 

performance of a pavement. To understand how pavement thicknesses vary along LTPP test sections, which 

are generally 500 ft (152 m) long, ground penetrating

radar (GPR) measurements were performed on a subset of LTPP test sections. GPRis a nondestructive technique based on reflection of radio waves transmitted in 

the ground to determine subsurface changes in material properties. For pavement applications GPR is typically used to determine the thickness of pavement 

layers and the dielectric constant of paving materials. 

Among other potential applications are detection of 

subsurface voids and moisture concentrations.

The primary interest in GPR technology by the

LTPP program was to measure pavement layer thicknesses. In 1994, a study of 10 GPS LTPP asphalt test

sections in the southern and eastern United States concluded that GPR could be used to accurately character-
84    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

ize asphalt thickness.10 In 2002, the LTPP program

initiated plans to collect GPR measurements on all

SPS-1test sections and at1jointed plain concrete pavement section at the Arizona SPS-2 site, 10 AC overlay

sections at the Oklahoma SPS-5 (rehabilitation of AC

pavements) site, and 5 test sections at the Oklahoma 

SPS-6 (rehabilitation of jointed PCC pavements) project site. Nineteen SPS sites consisting of multiple test

sections were surveyed in 17 States within a 6-week

timeframe in 2003.11

To ensure the collection of high-quality data, GPR

measurements took place only on dry pavement surfaces. GPR data were collected along both wheelpaths

at posted highway speeds. To precisely locate the GPR

data for each pass, a photo-reflective laser switch, 

mounted to the rear of a survey vehicle, transmitted 

and received a signal pulse from polarized reflectors 

set up along each test section. These position pulses 

were automatically recorded in the GPR data files for

each pass. The depth of the AC, treated base, and aggregate layers can be shown in a GPR report.

Only the interpretations of the GPR data from the

2003 measurements were included in the DLR module

in the LTPP database; data from the 1994 study were 

not included. While no report on the findings from the 

2003 GPR measurements was published, the LTPP

program did not implement GPR measurement technology as a routine pavement measurement device on 

LTPP test sections.

INVENTORY

Inventory data include location (e.g., latitude, longitude, 

state, county, route, milepost) of the test section, pavement type, layer thicknesses and types, material properties, composition, previous construction improvements, 

and other background information. Inventory information was collected for all GPS test sections and for SPS

sections originally classified as maintenance and rehabilitation experiments. The inventory data in the LTPP 

database are supplied by the State and Provincial highway agencies. Structural information, such as shoulder

width and milepost, was derived from highway agency 

project records or measurements taken at the test sections by the LTPP program. The inventory data includes:

•	 Location information thatidentifies the test section.

•	 Site information from the time of construction (or

rehabilitation) such as the composition and temperature of the paving mixture, aggregate and cement 

properties, and ambient conditions; joints, reinforcement, compaction, strength, drainage features; 

properties of the subgrade and base; completion and 

opening dates; and other characteristics of the pavement at the time of construction or rehabilitation.

•	 Geometric details of the test section.

•	 Initial cost data for the construction or maintenance

of the section, as well as information on snow and

ice control.

Inventory data collection began in 1988 and continues with the inclusion of the latest LTPP experiments (warm-mix asphalt and pavement preservation 

experiments). Because some inventory data were 

incorrect or missing, various efforts have been undertaken to collect or correct the missing data. This was 

the case with the Program Assessment and Improvement Campaign in the mid-1990s, which looked at the

availability of data for the LTPP test sections (chapter 

11). The regional support contractors have worked 

very closely with the highway agencies to collect this 

information, and they continue to obtain inventory 

data from highway agencies whenever a maintenance 

or rehabilitation activity occurs at a test site. The 

inventory data module contains structural and location data for each LTPP test section, which are discussed below.

Structural Data

Collecting the structural data (layer types and thicknesses) presented challenges. Significant time and

effort were needed to process huge amounts of data 

onto forms. Highway agencies often did not have the 

resources (staff, time, or funds) to locate data and complete data forms. Some data elements had not been collected by agencies, and some historical data had been 

discarded over time and were no longer available.

The LTPP program worked with the highway 

agencies to retrieve as much data as possible. Some

agencies sent all of their data to the LTPP regional 

support contractor, who completed the required 

forms for the agencies. In other cases, the regional 
6: coction o

support contractors visited agencies to help collect 

data and complete the LTPP forms. 

Agency data were not necessarily representative of 

the test sections—the data covered highway lengths of 

from 1to 10 mi (1.6 to 16.1 km) while the LTPP sections

were only a 500-ft (152-m) segment of that distance.

Data had to be processed to determine a “best fit” scenario for LTPP use.

Location Data

The purpose for this data element was to establish 

accurate location information for every LTPP test 

section using maps, satellite technology, and other 

methods. The effort began with the agencies collecting latitude and longitude coordinates, and elevation 

data. After some initial investigations, discrepancies 

were found; for example, some data had been interpolated from maps that were only approximations of 

accurate measurements.

In 1994, first-generation Garmin® Global Positioning System units were purchased, and a new inventory

form was developed to collect data onsite.12 Around 

2001, newer generation global positioning units were

acquired, as the technology had improved dramatically. Magellan® global positioning tracking devices

were used. Then, in 2005, updated coordinates were

collected from pavement test sections using modern 

global positioning system receivers.13 A test section’s 

coordinates were also collected for AWS and weighin-motion (WIM) scale installations. The Garmin

eTrex® Global Positioning System receiver (GPSr)

with trip and waypoint (Model Legend C) was

employed for this purpose. Data were typically collected by the LTPP regional support contractors, coinciding with manual distress surveys. Measurements

were verified by comparing the coordinates with previous measurements and plotting the locations on 

digital maps. In cases where field measurements could 

not be performed, up-to-date mapping software 

(MapSource® 6.0 or Google EarthTM mapping service)

was used. Measurements and location estimates were

based on the World Geodetic System 84 datum. The

original latitude, longitude, and elevation data were 

replaced with the new and more accurate data, which 

are stored in the LTPP database. 

In 2007, the global positioning component of the

location data was moved from the Inventory module 

and placed in the Administration module. Accurate 

global positioning coordinates are now available for 

all LTPP sites. In 2013, the LTPP program began collecting location data using the new GPSr equipment

connected to the falling weight deflectomter and profile units.

MAINTENANCE AND R

DATA

The maintenance and rehabilitation data tables in the

LTPP database have been consolidated in a single module. The maintenance tables contain information about 

treatments—seal coats, patches, joint resealing, grinding, milling less than 25 mm (1 inch), and grooving—

applied to test sections after (and in some cases before) 

the section’s inclusion in the LTPP program. The rehabilitation tables contain information on resurfacing, 

reconstruction, joint repair, and similar activities, 

which typically alter pavement structure.

Maintenance Data

Maintenance-type treatments that are reported by

highway agencies and stored in the LTPP database 

include thin surface treatments, crack sealing, joint 

sealing, and patching performed on in-service test sections. Obtaining the data elements that are needed to 

accurately and completely document maintenance 

activities performed on GPS and SPS test sections has

been a challenge throughout the LTPP program. This 

effort has been complicated by the wide variations in 

maintenance policies, practices, and data collection 

procedures among agencies, and the need for coordination between the agencies and the LTPP program. 

LTPP maintenance data document 

surface treatments that do not change 

pavement structure—seal coats, crack 

sealing, patching, joint sealing, grinding, 

grooving, and shallow milling.
86    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The highway agencies were asked to follow a maintenance policy that required coordination with the 

LTPP regional support contractor responsible for data 

collection at sections located within their State or

Province. Through this coordination and advanced 

notification that a maintenance activity is scheduled to 

take place, the value of the data obtained from a test 

section after it had been monitored for a number of 

years would be increased significantly because a set of 

performance data could be obtained prior to and after 

the maintenance treatment. Maintenance decisions

and agreements between each agency and the LTPP 

program were worked out with a cooperative spirit, 

with consideration for the needs of the agency. The 

agency was asked to provide all details of the maintenance activity on the LTPP maintenance data sheets to 

facilitate entry into the LTPP database.

Although this cooperative spirit existed between 

the highway agency and the LTPP program, on many 

occasions a maintenance activity was completed without the program’s knowledge. As a result, the last data 

point before maintenance took place, which is critical 

to understanding a pavement’s long-term performance, 

was not collected. Also, sufficient data were not always 

available to establish a new starting point for the LTPP 

section after maintenance took place. In these cases, 

the LTPP regional support contractor made every 

effort, working with the highway agency, to obtain the 

details of the maintenance activity that had been performed. These efforts included visiting agencies, 

searching through files and archives, and talking with 

staff who were at the job site when maintenance was 

performed. Often, further information was retrieved, 

but some maintenance data remain missing.

The collected maintenance data provide information 

such as when the activity was performed and the materials, construction equipment, and practices used. The following guides have been used in collecting the data: 

Long-Term Pavement Performance Maintenance & Rehabilitation Data Collection Guide;

14 Specific Pavement Studies, Data Collection Guidelines for Experiment SPS-3, 

Maintenance Effectiveness for Asphalt Concrete Pavements;

15 and Specific Pavement Studies, Data Collection 

Guidelines for Experiment SPS-4, Maintenance Effectiveness for Portland Cement Concrete Pavements.

16 LTPP 

program directives also provide additional information.17

Rehabilitation Dat

Most rehabilitation procedures, such as recycling or

placing overlays, produced a test section with a modified pavement structure. Other procedures, such as 

undersealing, were considered to restore the existing 

pavement structure. Reworking shoulders and placement of edge drains are other examples of improvements that could be made without changing the 

primary pavement structure. 

Highway agencies were asked to notify the LTPP 

program whenever rehabilitation was planned, so that 

the condition of the pavement could be observed and 

recorded prior to the rehabilitation activity. They were 

also responsible for providing the program with information about the treatment. 

The LTPP program had to ensure that all rehabilitation data were complete and processed promptly and 

thoroughly because these data were key to successful 

data analyses. In many cases, not all of the required 

information was provided to give a new starting point 

for the LTPP test section. More intensive searches on

the part of the LTPP regional support contractors, as 

with maintenance data, yielded positive results. However, rehabilitation data for many LTPP test sections 

are still missing. Although this missing data can be 

added to the LTPP database if the highway agencies 

are able to provide it, the rehabilitation test sections 

where data continues to be lacking may provide little 

to no value for certain data analysis studies. 

LTPP documents provide guidelines regarding 

when a section that had undergone rehabilitation could 

continue to be monitored by the program. These documents include the Long-Term Pavement Performance 

Maintenance & Rehabilitation Data Collection Guide,

18

guidelines specific to SPS sections,19 and LTPP program 

directives.20 Some of the rehabilitation treatment types

caused a section to be removed from further study. Others resulted in the test section being moved to a new 

experiment. In some cases, there was overlap between 

SPS-5, -6, -7 (rehabilitation studies), and GPS-6 and -7

(overlays of AC and PCC) rehabilitation data. Some

data for the SPS rehabilitation experiments are stored

LTPP rehabilitation data document a change 

to the pavement’s original structure.
6: coction o

in the maintenance and rehabilitation module and not 

in the respective SPS module. Access to these data has

been streamlined in the new LTPP InfoPaveTM system.

MATERIALS DA

The LTPP database has materials sampling and testing 

information for all test sections. The primary objective 

for performing materials sampling and testing was to 

provide a comprehensive evaluation of the pavement 

layer structure and layer thicknesses of the pavement 

materials used in each section or project. The material 

testing data represent the condition of the material at the 

time of sampling and testing. The work was accomplished by core drilling, augering, test pit opening, sampling, and nuclear density testing, followed by performing 

a suite of laboratory material characterization tests (see 

sidebar, next page). To help with data collection, standard material sampling and laboratory testing protocols 

with data entry sheets were developed to record the data 

collected in the field and in the laboratory.

The GPS and SPS experiments followed different

approaches to materials sampling. For GPS experiments, FHWA contracted out this task, and a drilling 

supervisor from the LTPP regional support contractor’s office was responsible for QC. For SPS experiments, the highway agencies were tasked with the 

drilling. In addition, the sampling approach for each 

SPS experiment was different. A material sampling

guide was prepared for the GPS experiments, and specific sampling guides were prepared for each of the 

SPS experiments.

The initial GPS Materials Sampling and Testing

Guidelines were issued in May 199021 and finalized in 

February 1991.22 A series of SPS Materials Testing and

Sampling Guidelines was developed between November 1989 and February 1996. The Laboratory Testing 

Guidelines were finalized in May 1992, but a series of

revisions was issued between October 1992 and September 2001. In 2007, the Long-Term Pavement Performance Project Laboratory Materials Testing and 

Handling Guide was issued.23

For projects that received overlays that were still to 

be monitored by the LTPP the program, the agencies 

would obtain the materials with assistance from the 

LTPP regional support contractors, who were responsible for getting the right materials to the right location 

for testing. The regional staff assisted the agencies’ 

drilling crews during the sampling operations to 

ensure that the onsite sampling operations were completed accurately, efficiently, and safely. The safety of 

the operating crews as well as the traveling public was 

of the utmost importance. 

Before going to each of the LTPP sites to collect samples, a formal plan was prepared indicating the sections, 

locations of the samples, and different layers that were 

to be collected from each location. The location numbers and sample numbers also needed to be defined. For 

each SPS project, a unique sampling and testing plan

had been prepared before the project was constructed. 

The SPS experiment-specific guidelines provided the

approach to be used in preparing the project-specific 

plans before, during, and after construction of the SPS

sections. The advance planning ensured a smooth process of sample collection, labeling, wrapping, and transportation to the designated labs.

All samples collected were marked with a pen or 

labeled with a keel chalk immediately after sampling. 

Blue (AC samples), white (PCC samples), or yellow 

(granular material) labels were also prepared for each 

sample and taped or inserted inside the bag or the box 

where the sample was to be stored. Labels contained the 

State code and LTPP test section ID, sample location,

sample number, sample date, and field set number.

While the core samples were set aside to dry, the 

regional staff measured and recorded the length of the 

cores and the quality of the samples before they left the 

site. Cores were also marked to indicate the direction 

of traffic. Once the cores had dried, they were wrapped 

with transparent plastic film and bubble wrap to prevent damage and packaged for shipment to the designated laboratories.

Materials data included information necessary to

characterize the various layers of each test section. The 

testing was performed by highway agency laboratories 

and by laboratories contracted by FHWA. For example, 

a laboratory hired by FHWA performed all of the resilient modulus tests. In addition, the concrete laboratory 

at FHWA’s highway research center performed the 

PCC coefficient of thermal expansion testing. Each

laboratory has an ID number in the LTPP database.
88    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Sampling Activities

Materials sampling activities are performed at the 

LTPP test sections using special equipment such as 

the dynamic cone penetrometer, shown below. The 

materials collected are tested in a laboratory, the 

data are stored in the LTPP database to provide information for pavement analyses, and the samples 

are stored in the Materials Reference Library (MRL).

Materials Reference Libra

The MRL was created in the late 1980s under the 

Strategic Highway Research Program (SHRP) in 

Austin, Texas, to provide a central storage facility 

for asphalt cement and aggregate samples collected under the Asphalt Research program and for 

pavement and subsurface materials samples collected from the LTPP test sites across the United 

States and Canada. One of the facility’s main objectives is to address a problem associated with the 

original American Association of State Highway 

Officials Road Test, conducted in Ohio in the 1950s, 

where there was a shortage of materials available 

for subsequent research. 

In 1993, the FHWA-LTPP program took over management of the MRL facility and moved it from 

Austin, Texas, to Reno, Nevada. The MRL continues 

MATERIALS SAMPLING A

to be managed by FHWA to store materials samples 

for the LTPP test locations. Over the years, other 

pavement research programs, such as the Asphalt 

Research Consortium, WesTrack, the FHWA Crumb 

Rubber Modifier Project, and the WesTrack Project 

have sent samples from their test sections for storage in the MRL. Materials from the research conducted at the National Center for Asphalt Technology and 

the Western Research Institute are also stored there. 

The MRL stores over 1,000 tons of asphalt 

cement, Portland cement, natural aggregates, and 

combinations of these materials in both loose and 

core forms. In addition to storing the samples, the 

MRL maintains a temperature-controlled room to 

house photographic film records of distress collected from the LTPP test sites. Most of the materials at 

the MRL are from LTPP projects, including samples 

taken during construction of the SPS test sections. 

The materials samples have been used to support 

more than 30 national highway research projects. 

The samples enable the application of as-yet undeveloped test methods to LTPP materials, thereby 

enabling updates of the LTPP data to reflect new 

technologies. The MRL will continue to provide a 

common pool of materials for future research.

The samples are available to the public, and more 

detail is available at the MRL Web site (http:// 

192.186.205.27/ltppt/mrl).
6: coction o

In the early stages of the LTPP program, all samples 

collected from GPS sites were sent to LTPP contractor

laboratories to perform the required laboratory tests. 

Later, when an overlay was placed at a site, some of the 

cores were sent to the highway agency’s laboratory for 

testing in addition to the LTPP contactor laboratory 

that ran resilient modulus tests on these cores.

The samples collected from the SPS projects before,

during, and after construction were sent to both the 

agency lab for testing and to the LTPP contactor laboratory that ran resilient modulus testing and other 

tests. It is important to note that the quality of the SPS

materials test data was always a concern for the LTPP 

program as testing was done by numerous laboratories 

(i.e., a different laboratory for each highway agency or, 

in many cases, agencies had more than one laboratory 

perform the testing). As a result, the LTPP program 

kept the option open to repeat some of the tests performed by the highway agencies. Some SPS projects

were still missing materials data, as was discovered 

during an LTPP program assessment,24 so the LTPP 

program developed a plan to collect this missing data. 

The details of the Materials Action Plan are described

in the following chapter, Special LTPP Data Collection

Efforts.

MONITORI

The monitoring data module contains pavement performance information that is collected primarily by 

LTPP contractors. Since 1988, with the first materials

and falling weight deflectometer data collected at 

LTPP test section 373807 in North Carolina, the LTPP

program has been collecting distress, drainage, friction, rutting, and longitudinal and transverse profile 

data, with some exceptions. (Friction data were collected by the highway agencies and submitted to the 

program for inclusion in the LTPP database. The 

drainage data were collected by LTPP contractors for 

only a subset of LTPP test sections for a few months.) 

More information about each data type is discussed in

this section.

Deflection Data

One of the six objectives of the LTPP program is to 

improve pavement prediction and design models (as 

discussed in chapter 1). A variable needed to accomplish this objective is the change in seasonal and longterm response to pavement loads. For both GPS and

SPS sections,the LTPP program uses the falling weight

deflectometer (FWD) to measure the deflection

response of a pavement to a load of known magnitude. 

The program has conducted basin tests on AC and PCC 

pavements and load transfer tests on PCC pavements. 

LTPP program efforts have significantly improved 

the accuracy and precision in measuring pavement 

strength. Ultimately, efforts within the program to

achieve greater reliability and precision in FWD data

resulted in the establishment of calibration centers 

around the country and the development of muchimproved nationwide calibration standards: LTPP protocols formed the basis for American Association of 

State Highway and Transportation Officials (AASHTO)

Standard Recommended Practice R 32-09, Calibrating

the Load Cell and Deflection Sensors for a Falling

Weight Deflectometer, adopted in 2009 by AASHTO,

and updated as Standard Recommended Practice

R 32-11.25,26 This section highlights some of the activities that culminated in those advancements, which are 

detailed in chapter 10.

Just south of Winston-Salem in North 

Carolina, a pilot study was conducted 

to field test the Materials Sampling 

and Testing plan and the falling weight 

deflectometer protocol testing patterns. 

The pilot took place December 7, 1988, 

but due to a rare snow storm that hit 

Winston-Salem that day, the testing was 

completed on December 8. This GPS 

test section, 373807, was the first site 

where data were collected for the LTPP 

program. Officially, LTPP data collection 

began in 1989.
90    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

FWD Data Collection and Equipment 

Parts of the FWD data collection process are automated—the computer controls the operation, acquiring

and processing the data at high speed. In addition to 

sensing and recording load and deflection data, the system measures and collects air and surface temperature, 

time, and distance traveled on the roadway data. Some

manual measurements are required, however: the 

FWD operator uses a probe to measure the subsurface

temperature. Initially in the LTPP program, the subsurface temperature measurements were taken at 

three depths, but later these measurements were taken 

at five depths depending on the pavement structure. In 

2003, the FWD gradient temperature data collection

changed from drilling temperature holes at 25 mm 

from the top, at the middle, and 25 mm (1 inch) from 

bottom of the pavement surface layers to set intervals 

of 25, 50, 100, 200, and 300 mm (1, 2, 4, 8, 12 inches)

from the top of the pavement surface. The operator 

also measures the width of joints when testing load 

transfer efficiency on rigid pavements. Any cracks or 

surface distresses that might affect the measurements 

are included in the operator’s report.

During the early years of the LTPP program, under

the Strategic Highway Research Program (SHRP) and

later under the management of FHWA, each LTPP 

regional support contractor was responsible for storing, maintaining, and operating an FWD unit and its

towing vehicle. The first four FWD units were purchased in 1988. The FWD equipment has been

replaced or upgraded four times over the course of the 

program (in 1995, 2000, 2002, and 2014), and when

FWD data collection was expanded in 1995 to meet

the added demands of the SMP and new SPS sites, one

additional FWD was purchased for each region to permit the expanded data collection resulting from these 

new demands.

Figure 6.5 shows an FWD used by the LTPP program to collect deflection data. See appendix C for

more information on the type of FWD equipment and

software used to collect, store, and process the data 

over the years.

FWD equipment comparisons were held periodically, where the FWDs from the four LTPP regions

were brought together to assess their performance. 

Referred to as “FWD thump-offs,” these comparisons

were used to qualify newly purchased equipment for 

acceptance and program use, to perform periodic evaluations of the equipment’s operational status, and to 

conduct cross-training exercises for regional contractor staff (figure 6.6). The thump-offs were later dropped 

in favor of FWD User Group meetings, where regional

FWD operators and coordinators had an opportunity

to review problems and exchange information on the 

LTPP activities in FWD calibration led 

to the adoption of a national FWD calibration standard: AASHTO Standard 

Recommended Practice R 32-11.

Figure 6.5. Van-towed falling weight deflectomete

equipment used in the LTPP program.

Figure 6.6. Falling weight deflectometer equipment a

the first LTPP “thump-off,” which was held at Purdue

University in November 19
6: coction o

operation and maintenance of the FWD equipment

and analysis of FWD data.

FWD Maintenance

Continuous preventive maintenance is necessary to 

keep the complex hydraulic-electrical-mechanical 

FWDs operating under demanding conditions to collect high quality data and pass rigorous annual reference calibrations. The LTPP program developed a 

preventative maintenance plan to ensure that the 

FWDs (and other equipment) are maintained to a high

standard. The manufacturer’s owner’s manual provides guidance on most repairs and troubleshooting; 

however, eventually, after years of service, FWDs

require a complete overhaul, which the program has 

successfully done in recent years.

In spring 2003, the LTPP Southern Regional Support Contractor overhauled one of the FWDs operated

for the LTPP program, documenting the complete disassembly and reassembly with instructions and photographs. This maintenance and overhaul manual 

provides FWD owners, operators, and technicians

with instructions and guidelines that supplement the 

Dynatest 8000 owner’s manual (figure 6.7).27 In 2014,

the LTPP regional support contractors completely 

overhauled all of the FWD equipment with the Southern Region playing a key role in this activity.

FWD Quality Control Checks

Five validity checks (roll-off, nondecreasing deflections, overflow, load variation, and deflection variation) were built into the FWD software to alert the

operator of possible problems.

28 To further check 

the integrity of the data, the FWDScan software was

created for use in the field and again in the office to 

check data files for completeness and readability 

and to flag potential problems before data are loaded 

to the LTPP database. Similarly, the LTPP program

developed FWDCheck to allow for subdividing the

FWD deflections into uniform sections and provide

statistical information on the FWD readings. This

check was developed because earlier backcalculation exercises lacked uniform sections, which influenced the FWD results. FWDCheck also generated

an overall structural capacity in terms of effective 

Structural Number.

Another QC check used by the LTPP program is a 

deflection sensor location program called SLIC (an

acronym for the authors Stubstad, Lukanen, Irwin,

Clevenson).29 This program was developed and tested 

on FWD data collected by the LTPP program. Its LTPP

use is summarized in Study of Long-Term Pavement 

Performance (LTPP): Pavement Deflections.

30 SLIC was

a QC check for the sensor locations. The LTPP regional 

support contractors used engineering judgment to 

determine whether or not to use the FWD data based

on the data’s overall quality.

Because theFWD data are intended for research use,

the collection protocols required many more data than 

would be needed for routine pavement evaluation and 

rehabilitation purposes. Four drop-heights of equivalent 6,000-, 9,000-,12,000-, and 16,000-lbfloadings (26,

40, 53, and 71 kN) were selected for AC pavements and

three drop-heights of 9,000-, 12,000-, and 16,000-lbf

loadings for rigid pavements. Random errors in readings were handled by taking four drops at each height. 

Sensor history data were collected for each sensor and

the load cell atthe fourth drop of each height.A60-millisecond window was used to capture the history data.31

Just as the FWD equipment has been updated over the

years to improve data collection, the various software 

procedures used to ensure quality deflection data have 

also been updated as needed (appendix C).

Figure 6.7. The cove

of the FWD maintenance

manual, used to keep

the units operating at

peak performance.
92    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Establishment of FWD Calibration Centers 

At the first FWD thump-off, in 1988, SHRP recognized

the need to ensure that data being collected from each

FWD unit be comparable across the LTPP program. As

a result, the early program managers developed a 

methodology to calibrate FWDs to an independent reference standard and established centers to carry out 

the calibrations. 

The Dynatest FWD, which has been used by the

program, repeats itself very well, but comparison of the 

FWDs among the regions revealed statistical differences. Efforts were begun to reference-calibrate the

FWDs by adjusting the sensor readings to a reference

sensor to reduce significant statistical differences 

between the units. The prototype for this calibration 

procedure was developed atCornell University in Ithaca, New York, in 1988.32 Initial trial comparisons were 

conducted at Purdue University with the participation

of all four LTPP regional FWDs. The results of the

comparisons showed that, when calibrated, the four 

SHRP FWDs could be used interchangeably. A calibration protocol was published in 1991,33,34 updated in 

1994,35 and revised in 2011.36

The first production calibration center was built 

at the Pennsylvania Department of Transportation

(PennDOT) Bridge and Maintenance Office in Harrisburg and operations began in 1992. In the same year 

and using the same protocol, additional calibration 

centers were opened in Texas, Nevada, and Minnesota.

At the completion of the calibration centers, a round 

robin “Cal Off” was conducted with all four SHRPLTPP regional FWDs.This comparison indicated there

was minimal difference between the calibration centers, although some problems specific to individual 

centerswere noted.This activity also allowed the FWD

operators to compare their regions’ procedures with 

the other regions and refine them, if needed. 

The LTPP program provided the calibration centers 

(1) annual QA review and certification of the center 

operators and (2) technical services—training, troubleshooting, equipment replacement, and annual reference load cell calibration. Figure 6.8 shows an FWD

readied for testing in an LTPP calibration center. 

When the need to upgrade the calibration centers 

exceeded LTPP program resources, FHWA initiated, 

in 2004, Transportation Pooled-Fund Study TPF-5

(039): Falling Weight Deflectometer (FWD) Calibration Center and Operational Improvements.37 This 

study resulted in new, highly portable calibration 

equipment and in updates and improvements in the 

FWD calibration procedure.

38 The new procedure is 

demonstrated in a video available at the LTPP program’s InfoPave Web site.

Also among the pooled-fund study’s several objectives was to identify a source of support for the calibration centers over the long term. The study determined 

that the AASHTO Materials Reference Laboratory

(AMRL) was qualified to continue providing these calibration center support services in the future. FHWA 

and AASHTO worked together on transitional activities over 2 years, resulting in a complete transfer of 

calibration center support to AMRL on September 1,

2010.39,40 AMRL now provides the centers the review,

certification, and technical services previously provided by the LTPP program.

Frequency of FWD Calibrations

The LTPP program requires the regional FWDs to

have annual reference calibrations, every 9 to 14 

months and following any repairs or major maintenance of FWD sensors or processor.

41,42

Figure 6.8. An FWD being calibrated at the PennD

regional calibration center early in the LTPP program.
6: coction o

While the FWD calibration procedures have been	

updated over the years, the load cell calibration 

remained unchanged. However, the deflection sensor 

calibrations were modified to allow for a group of 

sensors to be calibrated in a stand with an accelerometer versus the linear variable differential transformer 

(a deformation measurement device) used as the reference device. This simplified the procedure and made it 

less dependent on soil and slab condition. 

FWD Manuals

In 1989, the SHRP-LTPP Manual for FWD Operational 

Field Guidelines, Version 1.0, was published, outlining

the requirements for test setups for both flexible and

rigid pavements, monthly relative calibrations, and 

temperature data collection requirements.43 In 1992, 

six sets of SPS site-specific guidelines were also issued.	

Interim changes in protocol were provided to the 

LTPP regional support contractors in the form of program directives, and the FWD manuals were updated	

to incorporate the SPS-related guidelines, revised calibration procedures, software changes, and step-bystep instructions for FWD data collection in 1993	

(version 2.0),44 2000 (versions 3.0 and 3.1),

45 2005	

(version	4.0),46	and	2006	(version	4.1).47

Major	changes	in	the	guidelines	were	occasioned	by

implementation of the Dynatest25 (Dyna25) software	

in 2000 and FWDWin in 2005. After the Texas 1996	

reference center calibration comparisons and operator 

exchange session, the LTPP regions performed followup	testing	with	the	Dyna25	software,	and	in	September	

2000 were directed to fully implement the new software and Operational Field Guidelines, Version 3.1. 

Subsequent versions simplified some of the earlier	

instructions and incorporated LTPP program directives into the text. 

FWD Meetings 

FWD comparisons were conducted and provided an	

opportunity to review problems and allow for exchange 

of information among FWD operators.These comparisons were later dropped in favor of attendance by the 

LTPP regional FWD coordinators at FWD User Group	

meetings, which were also a venue for FWD calibration center meetings. These annual meetings were

formed as a means for the exchange of information on 

the operation, maintenance, and analysis of FWD data.

These meetings gave the LTPP program an opportunity to meet with highway agency staff which was very 

important in the early days of the program. 

Distress Data

Distress surveys are performed to documentthe condition of the surface of LTPP test sections in terms of visible distresses—such as cracking, defects, deformations, 

joint deficiencies, rutting—by severity and quantity. 

Distress data have been collected using both photographic (film-based) surveys and manual surveys. Photographic surveys were the priority with manual 

surveys serving as backup at the start of the LTPP program. However, significant differences were noticed 

between the two methods, and so the program gradually began to depend more on the manual survey 

because of the known limitations with the photographic 

survey and the increased confidence in the distress 

rater accreditation process.

Photographic Distress Surveys 

The photographic distress survey’s objective was to 

provide a record of distress for data interpretation and 

archival purposes. Under SHRP management, a contract was awarded in 1989 to Pacific Aerial Survey

Company (PASCO USA) of Japan to collect the permanent distress records for all test sections in each of the 

four LTPP regions beginning in the fall of that year. 

PASCO was the only vendor able to record cracks as

small as 1 mm in width using backlit cameras and 

35-mm film. Between contracts, PASCO sold their

North American rights and equipment to Cumberledge, Gramling and Hunt (CGH) around 2000,

who subsequently bid and were successful in retaining

the contract with FHWA.

In the early part of the LTPP program, photographic surveys were conducted once every 2 years. As time 

passed, surveys were subject to budget constraints and 

typically occurred once every 3 to 5 years. Due to funding limitations, 2004 was the last year that CGH performed photographic surveys. At the conclusion of the

last photographic survey contract, the LTPP program 

began collecting detailed photographs of the test sec-
94    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

tions with each manual survey, so in effect the program 

is still collecting a photographic record of the LTPP 

test sections.

The photographic distress permanent record systems 

in the early 1990s were housed in vans (figure 6.9). The

distress was recorded on high-resolution 35-mm blackand-white motion picture film from overhead cameras 

directed at the pavement. Testing was conducted at night 

using artificial lighting to produce the highest quality 

images and minimize disruption to traffic.

Photographic distress or permanent record surveys 

had to be performed under dry conditions and were not 

taken at remote locations (e.g., Hawaii, Alaska, Puerto 

Rico, and Newfoundland). Also if the PASCO unit was

not able to get to a test section prior to maintenance,

rehabilitation, or closeout activities, then a manual distress survey was performed. Due to limitations with the

PASCO data collection system (such as not being able to

detect low-severity hairline cracking (< 1 mm) or to rate 

joint seal damage and crack sealant, faulting, and severity of potholes), the LTPP regional support contractors 

began to concentrate on doing manual distress surveys 

when visiting the test sites for other reasons, such as 

FWD testing. This ensured that distress data would be

available and that data elements that were not available 

from the PASCO film could be obtained.

Photographic Distress Interpretation

PASCO/CGH performed the initial distress rating, and

sent the film to the technical support services contractor, who performed the secondary review and QA, performed distress ratings, and electronically logged the 

resulting distress types, severities, and quantities. The 

electronic copy of the data was provided to the regional 

support contractors for additional QA and to load into 

the LTPP database, and hard-copy outputs were provided for review and historical records. Computer-generated distress maps were also produced (figure 6.10).

The SHRP Distress Identification Manual (described 

in the Manual Distress Surveys section) for rating distress was used to determine the severity and extent of 

each distress. Some distress types could not be easily

determined from the film. These are listed below by 

pavement type:

•	 AC—bleeding, polished aggregate, raveling, lane/

shoulder drop-off.

Figure 6.9. Mobile equipment used to photograp

pavement distress. Mounted on a boom extending from

the front of the vehicle is the motion picture camera,

synchronized with vehicle speed for continuous filming;

flood lights are mounted on the custom front bumper.

On a boom extending from the rear of the vehicle is 

35-mm pulse camera, which collects transverse profile.

The camera is controlled by a distance measuring instrument that can trigger the camera at preset intervals;

a strobe projector is mounted on the rear bumper.

Figure 6.10. Sample of a computer-generated distres

map from PADIAS 4.2 software.
6: coction o

•	 PCC—joint seal damage, polished aggregate, faulting,

lane/shoulder drop-off, lane/shoulder separation.

•	 Continuouslyreinforcedconcretepavement(CRCP)—

polished aggregate, lane/shoulder drop-off, longitudinal joint seal damage. 

The film images were rated using the Film Motion

Analyzer (figure 6.11) which PASCO USA had developed for the LTPP program. This device projected the 

film image onto a digitizing board. Because the film 

was on spools, the apparatus included a system to move 

the film through the projector. Initially a grid system, 

Pavement Distress Analysis System (PADIAS) 1.0, was

used to determine the area and length of distresses; 

later a vector system, PADIAS 4.2, was developed. A

study of LTPP distress data variability in the late 1990s

found that “Although differences in data interpreted 

with the PADIAS v1.x and v4.x systems exist, there is

excellent overall agreement between the two systems 

for all pavement types, especially for total distress 

quantities and for cracking-related distresses.”48

Photographic Distress Quality Control Checks

The four LTPP regional support contractors performed a QA check on 10 percent of the distress data

interpreted by the technical support services contractor from the film images before accepting it for loading 

to the database. The regions had a similar but somewhat less sophisticated apparatus and setup for checking the film as compared to the technical support 

services contractor. Three copies of the film were produced: a copy retained by PASCO, a copy provided to

the technical support contractor for rating (which was 

then forwarded to the regions for secondary review 

and storage), and a third copy for the highway agency. 

Due to the sensitive nature of the film and to preserve

the film’s images, the canisters that were stored at the 

regional offices early in the program were later transferred to an environmentally controlled room at what 

is now the LTPP Materials Reference Library in

Sparks, Nevada. (The reference library was begun

under the SHRP asphalt program and later transferred

to FHWA-LTPP management.)

QC/QA procedures were put in place with the automated distress survey contractor. Initial data reviews 

found discrepancies in the database between the photographic and manual distress ratings. This was particularly noticeable when using Distress Viewer and

Analysis (DiVA), a stand-alone software tool developed

in 2000 by the LTPP program to plot the historical

changes in distress over time.49 This resulted in a decision to redo the ratings on all the film (except SPS-3

and -4) using the PADIAS 4.2 software.

As part of the QC/QA procedures, film distress raters were required to attend distress rater accreditation 

workshops to become accredited FHWA-LTPP distress raters. This was to ensure that qualified personnel were performing the distress interpretations and 

that the ratings would be similar to those of the manual 

distress surveys. Due to the different data collection

methods, some discrepancies were still sometimes evident between the photographic and manual distress 

survey methods.

Manual Distress Surveys

Manual distress surveys were initially instituted as a

backup to the permanent film record distress method. 

These “walking surveys” were performed by trained 

and accredited raters. Before becoming a designated 

scheduled LTPP activity, manual distress surveys were 

not routinely performed by the LTPP regional support 

contractors exceptin the SouthernRegion, where manual distress surveys were performed at all sites as part 

of the site selection and verification process and later at 

sites visited for FWD testing. In 1995, the LTPP program issued a directive that outlined the measurement 

frequency and priorities for manual distress surveys.50

Stringent guidelines for the identification, interpretation, measurement of the quantity, and determiFigure 6.11. Film Motion Analyzer
96    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

nation of the severity of the distress, and 

documentation of the findings were followed. 

Raters were also required to provide manually prepared distress maps, photographs, videos, and distress data forms as needed to 

record the conditions at the time of the survey and any unusual distresses observed. 

These requirements were described in the 

SHRP Distress Identification Manual (DIM),

which was used to conduct the surveys. 

Development of the initial manual was funded by FHWA prior to the launching of SHRP,

to be used in the distress data collection that

would be performed under the original SHRP

program. The manual was written by SHRP’s

technical assistance contractor and drew on 

various Federal and State/Provincial manuals. The photographs included came mainly 

from these documents.51 The manual contains 

the forms that surveyors use to record and 

summarize cracks, faulting, and other surface 

distresses observed on the pavement during 

a manual survey (figure 6.12). These forms 

provide input to the LTPP manual distress 

data module.

After a secondDIMwaspublishedin1990,52

ratings became more consistent among all of 

the LTPP regions. The third version of the 

DIM was issued in 1993,53,54 and the fourth 

version, released in 2003, incorporated refinements, changes, and LTPP program directives 

that had been issued since the previous edition.55,56 The DIM was updated in 2014 in its

fifth version.57 

Following release of the fourth version, the LTPP 

program developed four pocket editions to assist 

field engineers in conducting manual distress surveys. Plasticized and durable, the pocket guides 

covered distress identification for AC, PCC, and 

CRCP, with an additional AC guide designed for 

local agencies.58 The pocket guides were developed 

by the North Dakota Local Technical Assistance

Program Center for use by local agencies with funding from FHWA. The Baltimore FHWA Resource 

Center reprinted a modified version. Both the techFigure 6.12. Example of the multipage forms used to rec

distresses observed during LTPP manual distress surveys. For each

pavement type, a different form is used to record surface distresses.

This is page 1 of the form for asphalt concrete pavement.

nical assistance program center and resource center 

versions were printed in 2005.

The DIM is also used in workshops to provide

examination and accreditation to LTPP distress raters 

in identifying various pavement distresses. These 

workshops were initiated early in the program to 

ensure consistency in data collection among different 

raters throughout the LTPP regions.

Over the course of the LTPP program, procedures for 

manual surveys changed as technical developments 

occurredor fundingwas adjusted.Some examples follow:
6: coction o

•	 Documentation of distress in photos during surveys,

made mandatory later in the LTPP program to provide a permanent visual record of the survey.59

•	 Population of a Distress Image/Photo database software table by LTPP regional support contractors 

with detailed information of all distress photographs taken since the beginning of their contracts.60

•	 Cessation of night time (artificially illuminated)

manual distress surveys, to reduce concerns over 

the safety of raters performing the surveys and the 

agency traffic control crew members, as well as the 

quality and consistency of the data being collected.

•	 Clarification of procedures for surface patches, creating the need to review map sheets and summaries before they are uploaded to the LTPP database.

Manual Distress Workshops

The first manual distress workshop was conducted in 

Arlington, Texas, in 1991, with representatives from all 

four LTPP regions attending. There were many discussions on what constituted distress, how it should be 

categorized, and what parameters should be used for 

ratings. There was also a distinct difference between 

how individuals from the north perceived distress and 

severity levels versus those coming from the south. 

Based on this workshop, it was evident that work 

would be required to get a consensus on what distresses would be categorized and how. For example, some of 

the more significant issues that required resolution 

were how to rate the distresses in the wheelpath, identify the cracks (e.g., longitudinal, fatigue), and rate the 

extent and severity of each distress.

Early reviews of regional distress surveys for consistency between raters indicated a need for training 

and standardization. Therefore, the LTPP program 

developed a workshop for accreditation of the LTPP 

regional distress raters.61 The raters were to be trained 

within the region and would attend the workshop to 

be accredited to conduct distress surveys for the LTPP 

program. Distress accreditation workshops were conducted every 2 years and included a distress presentation, field review of distresses, distress rating on 

flexible and rigid pavements, and the accreditation. 

The distress workshops were rotated among the 

regions, and accreditation expired after 24 months (or 

could be extended to the next available workshop). 

Other requirements, such as the need to conduct a 

minimum of 15 manual distress surveys each year, 

were added to ensure that only experienced raters 

were performing the manual distress survey duties, 

thus ensuring research-quality results.62 Between 1991 

and 2014, the LTPP program has held 38 manual distress workshops, 32 for LTPP regional support contractor raters, and six for PASCO/CGH raters. In the

early years of the program, two to three workshops 

were held each year; currently one workshop is held 

each year. Figure 6.13 shows a field exercise at a manual distress workshop.

Office Review of Surveys

Internal LTPP regional office reviews of distress surveys are also conducted. They include detailed checks 

for errors in math, summarization, and visual comparison with previous surveys regarding distress types 

and quantities.

After the initial mathematics checks and overall 

review, the manual distress survey is compared to the 

last visit for a time-series check. When noticeable discrepancies from survey to survey were found, a program 

directive was issued allowing the rater to take the prior 

survey maps into the field. Once the survey had been 

performed and summed, it was checked against the prior survey while on site. This allowed an explanation of 

the differences in distress before leaving the site.63 

Figure 6.13. Participants in a field review of distresses a

an LTPP distress accreditation workshop.
98    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Back in the office, the LTPP regional support contractors conducted reviews of the distress data 

entered into the database. In 2004, the DiVA software

was issued for use as an integral part of the regional 

office QC/QA activities, as well in the time-series 

evaluation of distress data (figure 6.14).64 The purpose 

for this software has been served, and it is no longer 

being used by the LTPP program for distress reviews.

Drainage Data

The drainage data contain information on the inspection of drainage features and, more specifically, information on the condition of the edge drain systems and 

the location of the lateral-side drainage structures. 

Drainage information gathered includes the presence

and type of subsurface drainage features, such as permeable layers, transverse drains, and longitudinal 

drains. The best source of information on the effect of 

in-pavement drainage systems will be from comparison ofthe drained and undrained sections on SPS-1 and

SPS-2 projects.

Two investigations were performed to explore the 

condition of the edge drains at the SPS-1, SPS-2, and

SPS-6 projects. Although some GPS projects contain

edge drains, they were not included as a primary 

experimental factor.

The first investigation included a video survey, 

wherein a camera on the end of a semi-flexible cord 

was inserted into the outlet and pushed into the drain 

pipe, recording the condition of the outlet itself as well 

as the drain pipes’ condition (figure 6.15). Observations 

included crushed pipes; sags; ponding water; pipes 

clogged with dirt, silt and construction debris; and 

numerous animals and their nests. The intent of this 

investigation was to determine the degree to which the 

pipes were properly constructed, and, if it was necessary to clean them out to ensure proper operation. 

Edge drain videos and reports were sent to the respective highway agencies, and the completed inspection 

forms (and associated data) were entered into the 

LTPP database.

The second drainage investigation conducted at 

the LTPP test sites included field investigations to 

evaluate the effectiveness of the drains themselves. 

As part of the study, Effects of Subsurface Drainage on

Performance of Asphalt and Concrete Pavements: 

Further Evaluation and Analysis of LTPP SPS-1 and

SPS-2 Field Sections (NCHRP 01-34D), liquid with

dye was injected into holes drilled in the pavement 

surface at a set distance from the drain outlet, and the 

length of time required for the dyed water to be 

detected exiting the drainage outlets was measured. 

In some cases the dye appeared very quickly, and in 

others it never appeared at all.65 This information 

may help explain anomalous findings in pavement 

performance and drainage effectiveness predictions.

Figure 6.14. Screen shot from DiVA software showing 

time-series chart of a pavement distress along with the

table for all distresses for a test section.

Figure 6.15. Edge drain inspection using videograp
6: coction o

Longitudinal profile data are collected almost exclusively by automated profilers, and manual Dipstick®

measurements as well as rod and level measurements 

are sometimes used as a backup. The Dipstick is the

backup device in the event an inertial profiler is unable 

to be scheduled or for remote sections that can not be 

visited due to distance (e.g., Hawaii and Puerto Rico). 

The Dipstick is still used for longitudinal profile comparisons because it is an ASTM standard profile measuring device. A list of profile data collection equipment 

used by the LTPP program over the years is shown in 

appendix C. 

Inertial Profiler and Dipstick Equipment and 

Verification Tests 

Inertial profiling equipment was first purchased in 

1989 and was replaced in 1996, 2002, and 2013 as technologies improved and as equipment deteriorated. The 

profilers, purchased by SHRP and then FHWA, underwent rigorous testing to ensure that they met the 

requirements specified in the contract documents. 

After each LTPP regional support contractor took 

delivery of a replacement profiler, a comparison of the 

new and old profilers was performed before the new 

profiler was put into service. These verification tests 

compared the output from the old and new equipment.

When the first profilers were delivered to the LTPP 

regional support contractors in 1989 (shown in figure 

6.17), some of the regions added video cameras to the 

equipment to provide backup evidence of pavement 

condition at the time of survey. The videotaping also 

helped in determining if maintenance had occurred at 

the test sections. 

Figure 6.17. The first (DNC 690) Profilometers used 

the LTPP program. Three were mounted in the Champion

motor home chassis with Ford underpinning with dual rear

wheels, and the fourth in a Ford E350 van chassi

Friction Data

The LTPP database contains the results of friction tests 

on pavement sections where the State/Provincial highway agency was willing to provide the data. Because 

friction data hold the potential risk for litigation, submission was made voluntary. 

The LTPP data collection guidelines for friction 

data recommend using the ASTM E-274 (AASHTO T

242) procedure as the preferred method for obtaining 

data. The ASTM E-274 procedure uses a lockedwheel skid tester in a trailer assembly (figure 6.16). 

Friction test results are reported as Skid Numbers. It

should be noted that although the LTPP program provided guidelines for friction testing, the program has 

no control over the data collection method, measurement equipment, or calibration of the equipment 

used for these measurements. In addition, prior to 

2014, the LTPP database did not contain surface texture data or related information that are traditionally 

used to link pavement properties to measured friction 

levels.

Longitudinal Profile Data

Profile data are collected because pavement smoothness/roughness is perhaps the most important user 

parameter (i.e., level of service). Profile data and 

smoothness indices are used to track the performance 

of the section and provide input to the development of 

models, especially models that are related to user cost 

and benefits. Research-quality data require a stateof-the-art profiler to collect ride statistics and longitudinal profiles for long-term comparisons and the 

development of future smoothness indices. 

Figure 6.16. Locked-wheel skid tester currently in use fo

collecting friction data.
100    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The T6600 Profilometer and the ICC profiler are

pictured in figure 6.18 and figure 6.19, respectively. In 

2013, through a competitive process, the LTPP program replaced the ICC profilers with state-of-the-art 

Ames Engineering, Inc. profilers with added capabilities: macrotexture measurements are a new data collection element, and all of the data, including ambient 

and surface temperature, are referenced with Global

Positioning System coordinates (figure 6.20). The

new system’s software was designed through a collaborative manufacturer/LTPP program process.

As stated earlier, the LTPP program has used the 

Dipstick over the years in addition to the high-speed

profilers to collect profile data. (A manual Dipstick is

shown in figure 6.21.) A comparison study of the profiler, the manual Dipstick, and a portable rolling surface profiler manufactured by Face was conducted at 

the Virginia I-95 LTPP test section (511023) to provide

data for use in developing software for the manual collection of longitudinal profile data. The portable rolling profiler was found not to be an ideal tool for the 

LTPP program’s purposes. Safety issues arose with the

collection of transverse profiles because it was necessary to roll the profiler past the centerline in the adjacent lane to capture the profile at the centerline.

In 2003, issues were identified with the distance

as recorded from the various Dipsticks and the actual length of a section. To compensate for these differences, the LTPP program developed a procedure 

to determine the “effective Dipstick footpad spacing” as determined by applying the difference 

between the foot pad distance and actual distance. 

The Dipstick survey for the MnROAD profile comparison used the “effective” spacing and determined 

that it provided a more accurate distance when collecting Dipstick profiles.

66 

Comparison studies (sometimes called profile rodeos or rough-offs) are conducted at regular intervals to 

compare the output from the four LTPP profilers. For 

each study, several test sections are laid out, and reference profile measurements along each wheelpath are 

obtained using the Dipstick. Thereafter, profile measurements are performed on the test sections by the 

inertial profilers. The primary method for checking if 

the profilers are functioning accurately is to compare 

the International Roughness Index (IRI) values computed from Dipstick data with the values computed

from the data obtained from the profilers. The repeatability of the profilers is evaluated by analyzing the 

standard deviations of the IRI, which are computed 

using the IRI values obtained from repeat measurements on a test section. In the profiler comparison 

studies that have been performed since 1998, in addition to comparing the IRI values, profiles obtained by 

the profilers are compared to evaluate profiler repeatability and reproducibility. These are just some of the 

activities that the profile rodeo data analysis covers. 

The LTPP program has held 10 profiler rodeos in various locations across the country (see sidebar). Some of

Figure 6.19. ICC profiler MDR 4086L3 (Ford E350 

in use from 2002 to 2013.

Figure 6.20. Ames profiler in Ford E150 van, acquired

2013.

Figure 6.18. The T6600 Profilometer, in use from 1996 t

2002.
6: coction of

LTPP Profiler Rode

• 1990 in Austin, Texas.

• 1991 in Ann Arbor, Michigan.

• 1992 in Ames, Iowa.

• 1996 at LTPP Regional Support 

Contractor Offices.

• 1998 in Urbana, Illinois.

• 2000 in College Station, Texas.

• 2002 at LTPP Regional Support 

Contractor Offices. 

• 2003 at MnROAD, Minneapolis, Minnesota.

• 2007 in Minneapolis, Minnesota.

• 2010 in Minneapolis, Minnesota.

the rodeos have led to improvements, such as the integration of an updated calibration oscillator into the 

ICC profiler processor in 2003. Profilers and profile

coordinators at the 2007 rodeo are shown in figure

6.22. A summary of the profiler comparisons, Guide to 

LTPP Profiler Comparison Resource (2010), is available

from the LTPP Customer Support Service Center

(Email: ltppinfo@dot.gov). In 2013, the program held a

training session in College Station, Texas, to accept

delivery of the new profilers and teach the profile coordinators how to operate them (figure 6.23). In addition 

to the rodeos, in 2004, an analysis was undertaken to

quantify and resolve the differences in the longitudinal 

profile and roughness indices that are attributable to 

the different profilers that have been used in the LTPP 

program. The analysis indicated good agreement of 

IRI values among the different inertial profilers.67

The highway agencies often use FHWA-LTPP profile data as a reference for checking or calibrating their 

own profilers. Numerous profile comparisons have been 

performed among the FHWA-LTPP, agency, and contractor profilers.

Profiler Quality Control Checks

The LTPP program developed ProQual, which is a 

DOS-based software used to QC profilometer data collected at LTPP test sections. The major features were 

the ability to check for repeatability between runs (as 5 

error-free runs were required) and to generate ride 

quality indices other than IRI.68 ProQual was later 

updated to have the ability to identify spikes due to 

“lost lock” and “saturation” (which was a common 

problem with the incandescent profile system) and to 

accept longitudinal and transverse Dipstick data.

Issues with the calculation of IRI (related to smoothing) and slope variance (related to sample interval and 

sharp slopes) were identified and addressed in 1996 

(Tech Memo, March 1996). ProQual was further developed to incorporate office QC and calibration routines, 

and updated with additional features.

Figure 6.22. Profile coordinators with four ICC profiler

and the last K. J. Law Profilometer (center), gathered for a

rodeo at MnROAD in 200

Figure 6.23. Profile coordinators gather in Colleg

Station, TX, in 2013 to receive training from the LTPP

program on the new Ames profiler units.

Figure 6.21. Manual Face® Dipstick® used to collec

profile data in the LTPP program.
102    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

A Windows-based version of ProQual with additional features was issued in 2002. In particular, the

ability to handle multiple years of data and the refinement of sub-sectioning SPS projects were added.69

ProQual 2002 was updated again in 2005 to add the

ability to backup data and files and to address issues

identified by the LTPP regional support contractors 

to further enhance the software.70 ProQual became 

the basis for FHWA’s profile processing software 

package, ProVAL,whichwas first released in 2001.71,72

ProXport was developed to create 25-mm data in the 

new industry-accepted text file format (.erd) developed by the Michigan Transportation Research Institute’s Engineering Research Division.73 ProQual 2012

was designed to efficiently and effectively process all 

data being collected with the latest profilers, Dipstick, and SurPRO; this version introduced the Sidekick® program to process the new macrotexture

measurement data elements as well as the new temperature and GPS coordinate data. ProQual 2014 is

the latest version of the ProQual software. This version combines all of the previous exterior programs 

(ProXport, Sidekick) into one robust modern language software package.

Profile Manual

In 1989, the first profile manual, Manual for Profile 

Measurement: Operational Field Guidelines, was 

developed and distributed to the LTPP regions for 

their use in collecting pavement longitudinal and 

transverse profile data.74 As profile equipment 

changed and data collection activities improved 

with technology, the LTPP program updated the 

manual to reflect these changes in 1994,75 1997,76

1999,77 and 2002.78 Subsequent updates of the manual in 2004,79 2008,80 and 201381,82 carry the title 

“LTPP Manual for Profile Measurements and Processing.” The manual contains procedures for collecting data using automated profiler equipment, the 

Dipstick, and the rod and level; performing calibration tests and calibrating and maintaining the equipment; recordkeeping; office processing of data 

collected in the field; and guidelines for performing 

interregional comparison tests. Figure 6.24. Measuring rut depth with the 4-ft straightedge

Rutting Dat

While rutting information derived from PASCO’s

semi-automated transverse profile methods was the 

primary method at the start of the LTPP program, the 

backup manual method was initially based on a 4-ft 

(1.2-m) straightedge (figure 6.24). The straightedge 

rut-depth method is based on positioning the straightedge at various locations in each half of the lane until 

the maximum displacement from the bottom of the 

straightedge to the top of the pavement surface is 

found. Only the maximum rut depths in the left and 

right wheelpath are reported from this measurement 

and stored in the LTPP database.

The 4-ft straightedge method was based on the rut 

measurement protocol from the American Association 

of State Highway Officials (AASHO) Road Test. It is

important to note that the wheelpath locations at the 

road test were marked with paint to channelize this 

early form of accelerated pavement test. In the early 

implementation tests of the automated transverse profile measurement equipment, it was discovered that on 

public highways, it was not uncommon for the depressions in the wheelpaths to be wider than 4 ft (1.2 m). 

This was particularly noticeable on wider lanes. 

Because the baseline reference of the 4-ft straight edge 

would sometimes fit inside the wheelpath depression, 

the resulting rut depth measurement was less than the 

actual depth. 

Although the eventual manual backup method to 

the semi-automated procedure to measure transverse 

profile was through the use of a Dipstick, rut data measurements using the 4-ft straightedge method were 

required for all SPS-3 (preventive maintenance of flexible pavements) test sections. The 4-ft straightedge 

method was only in use in the LTPP program from 

1989 to 1991.
6: coction of

Transverse Profile Data

In the early stages of the LTPP program, transverse 

profile was determined from 35-mm picture frames 

by the string line method/algorithm. A string was 

stretched over the high spots and the vertical distance 

measured at the deepest depression in the wheelpaths. This interpretation was performed by PASCO.

Photographic and manual techniques have been 

used to represent the transverse profile of the test section pavements and to calculate rut depth and cross 

slope. With photographic techniques, images are 

obtained using an automated film-based profiler system mounted on the back of the PASCO/CGH survey

vehicle, and these images were translated into points of 

data. With manual techniques, Dipstick measurements

must also be translated to be comparable with profiler 

data. The LTPP regional support contractors are 

responsible for collecting manual transverse profile 

data for their regions. The national data collection contractor that took the photographic distress measurements also took the photographic transverse profile 

measurements. Measurements were typically taken at

15.25-m (50-ft) intervals. The data collected from photographic transverse profiling were used to compute 

the rutting data found in the LTPP database.83 

Automated Transverse Profiling

Initially, the primary method used by the LTPP program to capture distortions in a pavement’s transverse 

profile was photographic, using the ROADRECON-75

equipment manufactured by PASCO. The system used

a 35-mm black-and-white optical imagery photographic technique. A pulse camera mounted on the survey 

vehicle photographs hairline optical bars projected 

onto the pavement surface (figure 6.25). The camera 

shutter and hairline projector are synchronized with 

vehicle speed, allowing the distance between measurement locations to be specified.

The initial analog-to-digital conversion of the transverse surface profile was obtained by projecting the 

recorded image of the hairline on the pavement onto a 

digitizing table and tracing its shape using a high precision mouse (figure 6.26). Up to 30 transverse and vertical (X-Y) points in the transverse profile shape were 

captured. As illustrated in figure 6.27, the elevations in 

Figure 6.25. Diagrams of the PASCO/CGH ROADRECON75 showing (a) the transverse surface profi

mounted in a vehicle; and (b) the geometric relations

between the system’s optical bar and camera.

Figure 6.26. Translating photographs produced by th

automatic profilers into digital format. Transverse profile/

rutting was determined from 35-mm picture frames by the

string line method/algorithm. Generally 30 points defin

the transverse profile.
104    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

the initial digital profile are then converted to “normalized” elevations using the geometric relationships 

between the hairline projector and camera, simple 

trigonometry relationships, and proprietary calibration factors to account for optical distortions from the 

camera lens. Due to the limitations of this technology,

the shape of the transverse profile from these measurements is normalized so that the beginning and end 

points of the profile are assigned a zero elevation. Thus 

while these measurements provide information on 

many aspects of the characteristics of the distortion in 

the shape of the transverse profile, they do not provide 

an indication of the pavement’s cross slope. 

Dipstick Becomes Choice for Collecting 

Transverse Profile and Cross-Slope Information

As noted earlier, simple rut-depth measurements 

using a 4-ft (1.2-m) straightedge did not sufficiently 

measure the actual rut depths in all cases or capture 

all features of interest in the transverse profile. In an 

early comparison of rut depth indices derived from 

PASCO and Dipstick measurements on a sample set of

test sections, the two devices were found to provide 

repeatable results within the realm of engineering 

accuracy.84 Consequently, the Dipstick was adopted

by the LTPP program in 1992 as the manually operated measurement device to perform transverse profile 

measurements because it is an ASTM standard profile

measuring device. 

Dipstick data were collected in conjunction with

manual distress surveys. The Dipstick’s principle of

operation is that it measures the difference in elevation 

between its two reference elevation feet located 1 ft 

(305 mm) apart. For transverse profile measurements,

each transverse profile measurement start point is 

assigned a zero elevation. By adding the cumulative 

elevation differences between readings this measurement device is capable of recording the elevation difference between the beginning and end points of a 

transverse pavement surface profile. To conform to the 

transverse measurement protocol from the PASCO

ROADRECON-75 system initially adopted by the LTPP

program, all Dipstick transverse profile measurements

are stored as normalized elevations in the LTPP database. Three different models of Dipstick have been

used during the program, Face® models 1500, 2000,

and 2200, as shown in figure 6.28.

Dipstick calibration is performed on a per-site basis,

using the zero check (to ensure meter’s elevation reading is the same when rotated 180o) and the calibration

block check (if elevation reading is zero, the result 

from this check should be 3.2 mm or very close to the 

height of the block) before and after each site visit. The 

calibration procedures followed are detailed in an 

LTPP program directive,85 the Distress Identification 

Manual,

86 and Profile Manual.87 

Dipstick data are entered to update the transverse

profile database using the ProQual software. Header 

information and graphical displays of the forward and 

backward passes and of the normalized elevations can 

be reviewed. Output files of the normalized elevations 

(rounded to the nearest millimeter) and cross slope are 

stored in the LTPP database.

In 2003, the LTPP program decided to capture the

pavement cross-slope information contained in the 

Dipstick manual transverse profile measurements by

reinterpreting the raw data from previous measurements and performing one round of manual transverse 

profile measurements using the Dipstick on PCC-surfaced pavements. The objective was to extract the 

cross-slope information contained in the raw dipstick 

measurements to enable translations of the normalized profiles into actual transverse pavement profiles. 

The motivation for this action was to provide an analytical basis on the potential of ruts to hold water 

within the cross-elevation profile and to provide 

Figure 6.27. Normalization of transverse profi

measurements to lane edges. The transverse elevations

are adjusted to a reference line through the endpoints so

that the elevations of the endpoints are zero.
6: coction of

cross-slope data for other analysis objectives. The first 

release of the cross-slope data was in 2004. In 2012,

another round of transverse profile measurements 

was begun on active PCC test sections.

PCC Transverse Profiles

In the early years of the program, transverse profile 

measurements were performed on both AC- and PCCsurfaced test sections using the PASCO automated measurement device. In more recent years, transverse 

profile images on PCC-surfaced test sections have not 

been interpreted due to program budget cuts. A littleknown fact is that the LTPP program has collected data 

which show that PCC pavements also exhibit depressions in the wheelpath. The LTPP database contains 

information on distortion in the transverse profile of 

PCC-surfaced pavements that is not available elsewhere.

SEASONAL MONITORIN

Temperature and moisture-related changes in pavement structures, both within a day, from season-to-season, over the course of a year, and from year-to-year, can 

have significant impact on the structural characteristics 

of pavement layers, thus affecting the pavement’s 

response to traffic loads and, ultimately, its useful life. 

To attain a fundamental understanding of the magnitude and impact of temporal (daily, seasonal, and annual) variations in pavement response and material 

properties due to the separate and combined effects of 

temperature and moisture variations, SHRP envisioned

the SMP. The study concept received strong support

from the LTPP stakeholder community and was also 

endorsed by the Transportation Research Board (TRB) 

LTPP Pavement Performance Advisory Committee.

Because the SMP was not part of the original LTPP

program plan and has involved a large investment of 

resources, its development and implementation under 

FHWA are discussed in chapter 7. The chapter 

describes the scope, equipment, data collection procedures, data collected (onsite air temperature and precipitation data, subsurface temperature and moisture 

content data, and frost-related measurements), and 

monitoring frequency. 

SPECIFIC PAVEMENT S

INVENTORY

SPS experiments that were newly constructed (SPS-1,

-2, -8, and some -9) made it possible for the LTPP program to collect the construction and materials data for 

these test sites. Therefore, a separate data module was 

created in the LTPP database specifically for the SPS

experiments to store what is essentially inventory data.

Because the constructed SPS test sections were

built to meet specific requirements, data associated 

with the construction of each project were recorded 

for the purpose of evaluating the performance of each 

test section within the project. After each SPS project

was completed, a report was prepared by the LTPP 

regional support contractor with information collected during the different stages of construction. Many of

the construction reports included details of meetings

that took place in preparation for the construction of 

the SPS sections as well as sampling and testing performed before, during, and after the new pavement layers were constructed. Any data collected and pertinent 

drawings were included in the reports, which are available on the LTPP InfoPave Web site. The reports’ 

appendices included a correspondence section, any 

materials or QC data provided by the agency or the 

contractor on site, photos of the different equipment 

and activities performed during construction, and a 

Figure 6.28. Three Face® Dipstick® profile measurin

devices with carrying cases. Left to right are the 1500,

2000, and 2200 models.
106    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

summary explaining any deviation from the experiment guidelines that was documented during the different stages of construction.

In addition to the data collected on site by the LTPP 

regional support contractor, the highway agency had 

the responsibility of submitting information about the 

SPS experiments: for example, inventory forms for

overlay SPS experiments, construction sheets from all

SPS experiments, and information about the asphalt or

concrete plant and other equipment and procedures 

used during construction. The submitted inventory 

and construction data were not always complete. In 

some cases, the LTPP regional support contractors, 

through agency visits and archive searches, retrieved 

further information, but some SPS construction data

are still missing and are likely to remain missing despite 

many attempts to collect these data.

TRAFFIC DAT

Since the beginning of the LTPP program,

highway agencies have committed to provide 

traffic loading (weight), classification, and volume data for each LTPP test site. The LTPP 

database contains historical and monitored 

traffic data, which are discussed in the following sections. A special traffic data collection 

effort, initiated by FHWA under a pooledfund study that was supported by the State/

Provincial partners, is discussed in chapter 7.

Historical and Monitored Data

“Historical data” is defined as data collected 

during a period beginning at the initial opening of the pavement to traffic (or the most 

recent overlay or rehabilitation project) and 

extending through 1989 and applies only to 

GPS test sections. The purpose of collecting

historical traffic data was to determine the 

best estimate of annual traffic levels at each 

test section before LTPP performance monitoring began at the pavement section. “Monitored data” is defined as data collected at the 

initiation of LTPP performance monitoring of 

the pavement test section to date. 

Historical traffic data on sections in service before 

and after the start of LTPP monitoring in 1990, were

provided by the highway agency. There were occasions 

when the traffic characteristics of a site were either not 

known or questionable, and this required effort from 

the LTPP program and the highway agency, working 

together, to obtain this information. Figure 6.29 shows 

an LTPP traffic data sheet that the highway agencies 

use to submit historical traffic data. 

Monitored traffic data are usually collected separately for each lane being monitored. For the LTPP 

program, data collection was planned only for the outside lane (test lane) in one direction. Earlier in the program, the highway agencies were encouraged to 

provide traffic data from all lanes to populate the average annual daily traffic (AADT) tables. Monitored trafFigure 6.29. A sample data transmittal form used by the highwa

agency to submit historical traffic data to the LTPP regional support

contractor.
6: coction of

fic data are submitted on a monthly, quarterly, or 

annual basis depending on the practices of the individual agencies.

Traffic data include distribution of traffic by vehicle 

classes, days of data collected, and distribution of axle 

loads for single, tandem, tridem, and quad axles by 

vehicle class. For locations where traffic data have been 

submitted for all lanes, the data could include AADT

and percent trucks. Beginning in 1990, data have been

submitted in one of the electronic record formats documented in FHWA’s Traffic Monitoring Guide, second 

through fifth editions, issued in 1992, 1995, 2001, and

2013.88 

Highway agencies submit traffic information on 

individual data reporting forms, 16 in all, which provide historical and estimated volume and load data for 

the test site. The LTPP regional support contractor is 

responsible for tracking the data transmittal sheets, 

soliciting them from agencies when required, checking 

them for reasonableness, and entering them into the 

LTPP database. 

Although every effort has been made by both the 

highway agencies and the LTPP program, there are 

still gaps in the traffic data. Collecting traffic data at the 

LTPP test sections has not been as straightforward as 

collecting the other data described in this chapter. 

Many challenges existed, such as different types of

traffic data collection equipment used by different 

highway agencies and the lack of equipment calibration. These are just two of the challenges which the 

LTPP program sought to remedy in the early to mid 

2000s. One approach was to collect at least 1 week of

continuous classification data at those sites where no 

traffic data existed in the LTPP database (internal 

memorandum, “Minimum Standards for Traffic Monitoring Data Collection on LTPP Sites,” January 21,

2009).The other approach required partnering with as

many agencies as possible because it involved substantial funding and personnel resources to successfully 

carry out. This particular effort, better known as the 

LTPP SPS Traffic Data Collection Pooled-Fund Study,

TPF-5(004), is covered in more detail in chapter 7.

Data Collection Equipme

Equipment used to collect traffic data by the highway

agencies varied from different kinds of piezoelectric 

cables to bending plates to load cells. In the design of 

the LTPP program, the expectation was that all sites 

would be instrumentedwithreliable,low-cost($5,000)

weigh-in-motion (WIM) scales. However, the original

estimated cost and assumed reliability of equipment 

were not realistic. Therefore expectations for traffic 

data collection were redefined, and were described 

using three levels of effort:89

•	 Preferred—Continuous WIM data.

•	 Desirable—Continuous automatic vehicle classification (AVC) with site-specific seasonal WIM.

•	 Minimum—1 year’s worth of continuous AVC at

some time within a 5-year period, with seasonal 

WIM within that same period.

Data collection was to occur near the test section

wherever possible. Where the pavement section under 

study and the traffic monitoring equipment were not 

co-located, which was true for nearly 15 percent of the 

pavement test sections, highway agencies were asked 

to provide measured data to determine the differences 

in traffic between the two locations. This information 

was not provided, however, by every highway agency. 

Several years into the program it became clear that

many agencies did not have the resources to meet even 

the minimum option at most locations. For sites for 

which monitored traffic data are not being collected, 

highway agencies are asked to provide the LTPP program with estimates of the traffic at the site using the 

traffic data sheet shown in figure 6.30.

 Equipment Calibrati

Two new LTPP protocols, detailing the guidelines and 

procedures for traffic data collection and calibration 

of data collection equipment, were issued in April 

1998.90,91 The equipment calibration protocol was 

issued because of significant anecdotal information 

that equipment was being installed without calibration 

or subsequent validation. 

Because high-quality traffic data collection 

requires verification of what is being collected, suggested practices were developed for agency use. After 

further minor revisions, in April 2000, the LTPP program implemented the Guide to LTPP Traffic Data 

Collection and Processing.

92 Updated in 2001,93 and 

2009,94 the guide contains all sheets required to be 
108    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

submitted with historical, calibration, and 

electronic traffic data submissions.

The LTPP program encouraged the highway agencies to check and calibrate, if necessary, their equipment every time it was used 

to collect data for the LTPP program. In addition, permanent WIM scales are expected

to have their calibration settings field validated (and updated as necessary) at least 

twice a year, and data were to be monitored 

on a monthly basis to ensure that the scales 

remain calibrated. This calibration check 

was to include both the weight and vehicle 

classification data produced by the equipment. It was recommended that data collected from an improperly functioning WIM

device not be sent to the LTPP program for 

inclusion in the database. However, it was 

apparent to the LTPP program that some 

data were sent for uncalibrated traffic data 

collection equipment.

By the late 1990s, it had become clear that

the spatial distribution, timeliness, quantity, 

and quality of the traffic monitoring data 

needed to be improved. Issues included nonuniform data collection equipment between 

highway agencies, infrequent or no calibration 

of the equipment, and insufficient checking of 

collected data. These deficiencies in the data 

motivated the LTPP program to develop a plan 

to collect traffic data of the quality that would be needed for future data analysis studies. This data collection 

effort was managed by the program from 2001 to 2014

and is covered in more detail in chapter 7.

SUMMA

Data collection is the primary activity in the LTPP

program, which supplies the information from which 

all productive activities follow—data analysis, product development, and standards. The challenge—to 

capture research-quality data of diverse types using 

highly specialized, state-of-the-art equipment with 

the involvement of many different people spread 

across North America—is great. Documentation of

the processes used has been essential, and as the 

LTPP program advanced, data collection guidelines, 

QC procedures, and equipment specifications have 

been created of necessity to assure the integrity of the 

data. These program documents have become models 

for other data collection efforts and have led in several cases to national industry standards. The program has kept pace with advances in technology by 

investing in improved data collection equipment and 

software, and has undertaken major efforts over the 

years to assure that the LTPP data are of sufficient 

quality and quantity to support pavement performance research. These efforts are discussed in the 

next chapter.

Figure 6.30. A sample data transmittal form used by the highwa

agency to submit traffic estimates to the LTPP regional support

contractor.
6: coction of

REF

	 1.	Directive GO-38, “LTPP Pavement Performance

Monitoring Adjustments,” Mar. 17, 2006. Federal

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/GO_01-49/GO-38.pdf.

	 2.	Directive GO-47, “Pavement Performance Monitoring

Guidelines,” Apr. 19, 2009. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

GO_01-49/GO-47.pdf.

 3. LTPP-SPS Automated Weather Stations: Automated 

Weather Station (AWS) Installation. Arizona Department of Transportation Open House, Phoenix, AZ, 

July 20–21, 1994.

	 4.	Directive AWS-1, “Installation, Data Collection, and

Maintenance of Automated Weather Stations at SPS-1,

2, and 8 Projects,” Sept. 12, 1994. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/AWS/AWS-01.pdf.

	 5.	 “Automated Weather Station Documents.”

Available at the LTPP InfoPave Web site. 

6. LTPP-SPS Automated Weather Stations: AWSScan 

Program Background and Users Guide, Version 0.5. 

Federal Highway Administration, McLean, VA,

October 1995; LTPP-SPS Automated Weather Stations: 

AWSCheck Users Guide, Version 1.0. Federal Highway 

Administration, McLean, VA, August 1996.

	 7.	MERRA: Modern Era-Retrospective Analysis for

Research and Applications Web page. http://gmao.gsfc.

nasa.gov/research/merra/intro.php.

8. LTPP Information Management System: IMS Quality 

Control Checks. Federal Highway Administration, 

McLean, VA, May 2002 (rev. September 2013).

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/qcm/qcm.pdf.

9. K. Chatti et al. LTPP Data Analysis: Influence of Design 

and Construction Features on the Response and Performance of New Flexible and Rigid Pavements (NCHRP 

Web-Only Document 74). Transportation Research

Board,Washington, DC, June 2005, pp. 88,115, 274. http://

onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w74.pdf.

	 10.	K. R. Maser.Ground Penetrating Radar Surveys to 

Characterize Pavement Layer Thickness Variations at GPS 

Sites(SHRP-P-397). Strategic HighwayResearch Program,

National Research Council, Washington, DC,1994. http://

www.trb.org/publications/shrp/SHRP-P-397.pdf.

	 11.	G. E. Elkins, B. Ostrom, B. Visintine, and J. Groeger.

Long-Term Pavement Performance Ancillary 

Information Management System (AIMS) Reference 

Guide (FHWA-HRT-12-058). Federal Highway

Administration, Washington, DC, November 2012, p. 8.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/12058/12058.pdf.

	 12.	Directive I-37, “Processing of Global Positioning

Measurements,” Dec. 20, 1995. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/IMS_001-049/I-37.pdf.

	 13.	Directive GO-34, “Measurement and Update of

Location Coordinates,” Mar. 16, 2005. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/GO_01-49/GO-34.pdf.

	 14.	A. L. Simpson and T. Thompson. Long-Term Pavement 

Performance Maintenance & Rehabilitation Data 

Collection Guide (FHWA-HRT-06-068). Federal

Highway Administration, McLean, VA, March 2006.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/06068/06068.pdf.

15. Specific Pavement Studies, Data Collection Guidelines 

for Experiment SPS-3, Maintenance Effectiveness for 

Asphalt Concrete Pavements. Strategic Highway

Research Program, National Research Council, 

Washington, DC, June 1990.

16. Specific Pavement Studies, Data Collection Guidelines 

for Experiment SPS-4, Maintenance Effectiveness for 

Portland Cement Concrete Pavements. Strategic

Highway Research Program, National Research 

Council, Washington, DC, November 1991.

	 17.	Directives GO-22, “Guidelines for Maintenance and

Rehabilitation of LTPP Test Sections,” July 30, 1999,

and GO-28, “Policy for Monitoring Continuation on

Rehabilitated Test Sections,” Nov. 7, 2001. Federal

Highway Administration, McLean, VA. http://ltpp.org/

dirs/GO_01-49/0_go_dir_list.shtml.

18. Long-Term Pavement Performance Maintenance & 

Rehabilitation Data Collection Guide (FHWA-HRT-06-

068). Federal Highway Administration, McLean, VA,

March 2006. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/06068/

06068.pdf.

	 19.	 “Specific Pavement Studies, Data Collection Guidelines

for Experiment SPS-5, Rehabilitation of Asphalt

Concrete Pavements” (Operational Memorandum

No. SHRP-LTPP-OM-015; Strategic Highway Research

Program, National Research Council, October 1990);

and “Specific Pavement Studies, Data Collection

Guidelines for Experiment SPS-6, Rehabilitation of

Jointed Portland Cement Concrete Pavements” 

(Operational Memorandum No. SHRP-LTPP-OM-023;

Strategic Highway Research Program, National

Research Council, May 1991).

	20.	LTPP directives GO-08, GO-13, GO-14, GO-22, GO-28,

and GO-33 provide information guidelines for maintenance and rehabilitation, test section monitoring and 

classification, and related forms (available at http://

www.ltpp.org/dirs/GO_01-49/0_go_dir_list.shtml).
110    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

21. SHRP-LTPP Guide for Laboratory Material Handling 

and Testing Version 2.0 (SHRP-LTPP-OG 006). 

Strategic Highway Research Program, National 

Research Council, Washington, DC, 1990–5. 

Available from LTPP Customer Support Service 

Center (ltppinfo@dot.gov). 

22. GPS Sampling Guidelines (SHRP-LTPP-OG-006). 

Strategic Highway Research Program, National 

Research Council, Washington, DC, February 1991.

23. A. L. Simpson, P. N. Schmalzer, and G. R. Rada. 

Long Term Pavement Performance Project Laboratory 

Materials Testing and Handling Guide (FHWA-HRT-07-

052). Federal Highway Administration, McLean, VA, 

September 2007. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07052/07052.pdf.

24. LTPP Program Focus–The Assessment, Final Summary 

Report, Federal Highway Administration, McLean, VA, 

March 1997, p. 8. Available at the LTPP InfoPave Web site.

25. R 32-09, “Calibrating the Load Cell and Deflection 

Sensors for a Falling Weight Deflectometer,” Standard 

Specification for Transportation Materials and Methods 

of Sampling and Testing, Part 1B: Specifications. 

American Association of State Highway and 

Transportation Officials, Washington, DC, 2009.

26. L. H. Irwin, D. P. Orr, and D. Atkins. FWD Calibration 

Center and Operational Improvements: Redevelopment 

of the Calibration Protocol and Equipment (FHWAHRT-07-040). Federal Highway Administration, 

McLean, VA, October 2011. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07040/07040.pdf.

27. R. Belt, T. Morrison, and E. Weaver. Long-Term 

Pavement Performance Program Falling Weight 

Deflectometer Maintenance Manual (FHWA-HRT05-153). Federal Highway Administration, McLean, 

VA, December 2006. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/05153/05153.pdf.

28. P. N. Schmalzer. Long-Term Pavement Performance 

Program Manual for Falling Weight Deflectometer 

Measurements. Version 4.1 (FHWA-HRT-06-132). 

Federal Highway Administration, McLean, VA, 

December 2006, p. 12. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/06132/06132.pdf.

29. R. N. Stubstad, L. H. Irwin, E. O. Lukanen, and M. L. 

Clevenson. It’s 10 O’Clock? Do You Know Where Your 

Sensors Are? Transportation Research Record: Journal of 

the Transportation Research Board No. 1716, 2000.

30. R. Stubstad, E. Lukanen, and L. Clevenson. Study of 

Long-Term Pavement Performance (LTPP): Pavement 

Deflections (FHWA-RD-03-093). Federal Highway 

Administration, McLean, VA, August 2006. http://

www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/03093/03093.pdf. 

31. LTPP Manual for Falling Weight Deflectometer Measurements Operational Field Guidelines, Version 3.1. Federal 

Highway Administration, McLean, VA, August 2000. 

32. Part 2: Pavement Strength and Deformation Characteristics: History and Development of U.S. Procedures for 

Falling Weight Deflectometer Calibration. Transportation 

Research Record: Journal of the Transportation Research 

Board, 2005, vol. 1905, pp. 66–72. http://trb.metapress.

com/content/556t384545h6277m/fulltext.pdf.

33. Strategic Highway Research Program: FWD Calibration 

Protocol. Strategic Highway Research Program, National 

Research Council, Washington, DC, October 1991.

34. Strategic Highway Research Program: Reference Calibration of Falling Weight Deflectometers—FWDREFCL, 

Version 3.2 A&B—Software User’s Guide and Instructional 

Manual. Strategic Highway Research Program, National 

Research Council, Washington, DC, October 1991.

35. “SHRP/LTPP FWD Calibration Protocol.” March 1994. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/fwdcal/fwdcal2.pdf.

36. L. H. Irwin, D. P. Orr, and D. Atkins. FWD Calibration 

Center and Operational Improvements: Redevelopment of 

the Calibration Protocol and Equipment (FHWA-HRT-07-

040). Federal Highway Administration, McLean, VA, 

October 2011. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/07040/

07040.pdf.

37. “FWD Calibration Improvements and Plans for the 

Future.” LTPP Newsletter (Fall 2009; FHWA-HRT-10-

031), vol. 5, no. 4, pp. 1–3. http://www.fhwa.dot.gov/

publications/ltppnews/LTPPFall2009.pdf.

38. L. H. Irwin, D. P. Orr, and D. Atkins. FWD Calibration 

Center and Operational Improvements: Redevelopment 

of the Calibration Protocol and Equipment (FHWAHRT-07-040). Federal Highway Administration, 

McLean, VA, October 2011. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07040/07040.pdf.

39. “FWD Calibration: Today’s Improvements and Future 

Plans.” Focus (November 2009; FHWA-HRT-10-008). 

http://www.fhwa.dot.gov/publications/focus/09nov/

03.cfm.

40. “In Brief.” LTPP Newsletter (Summer 2010; FHWAHRT-10-074), vol. 6, no. 3, p. 2. http://www.fhwa.dot.

gov/publications/ltppnews/10074.pdf.

41. Guidelines for Users of the SHRP FWD Calibration 

Centers (FHWA-SA-95-038). Federal Highway 

Administration, Washington, DC, November 1994.
6: COLLECTION OF THE LTPP DATA    111

42. “SHRP/LTPP FWD Calibration Protocol.” March 1994. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/fwdcal/fwdcal2.pdf.

43. SHRP-LTPP Manual for FWD Testing, Operational 

Field Guidelines, Version 1.0 (SHRP-LTPP-OG-002). 

Strategic Highway Research Program, National 

Research Council, Washington, DC, January 1989.

44. PCS/Law Engineering and Braun Intertec Pavement, Inc. 

Manual for FWD Testing in the Long-Term Pavement 

Performance Program, Version 2.0 (SHRP-P-661). Strategic 

Highway Research Program, National Research Council, 

August 1993 (Version 2.0, Feb. 1993 internally; Version 2.0 

including SPS Guidelines released May 1993). http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-661.pdf.

45. LTPP Manual for Falling Weight Deflectometer Measurements, Operational Field Guidelines, Version 3.1. Federal 

Highway Administration, McLean, VA, August 2000. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/fwdman/fwdman1.pdf. 

46. LTPP Manual for Falling Weight Deflectometer Measurements, Version 4.0. Federal Highway Administration, 

McLean, VA, April 2005. Available from LTPP Customer 

Support Service Center (ltppinfo@dot.gov).

47. P. N. Schmalzer. Long-Term Pavement Performance 

Program Manual for Falling Weight Deflectometer 

Measurements, Version 4.1 (FHWA-HRT-06-132). 

Federal Highway Administration, McLean, VA, 

December 2006. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/06132/06132.

pdf. Details on the evolution of the document are 

available at www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/06067/chapt6.cfm.

48. G. R. Rada, C. L. Wu, R. K. Bhandari, A. R. Shakharan, 

G. E. Elkins, and J. S. Miller. Study of LTPP Distress 

Data Variability, Volume I (FHWA-RD-99-074). Federal 

Highway Administration, McLean, VA, September 1999, 

p. 112. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/99074/99074.pdf.

49. “Distress Viewer and Analyzer (DiVa) Online.” LTPP 

Newsletter (Spring 2008; FHWA-HRT-08-060), vol. 4, 

no. 2, p. 1. http://www.fhwa.dot.gov/publications/

ltppnews/08060.pdf.

50. Directive D-5, “Measurement Frequency and Priorities 

of Manual Distress Surveys,” Mar. 14, 1995. Federal 

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/DIS_01-49/D-05.pdf.

51. K. D. Smith, M. I. Darter, K. T. Hall, and J. B. Rauhut. 

Distress Identification Manual for the Long-Term 

Pavement Performance Studies, Strategic Highway 

Research Program, National Research Council, 

Washington, DC, 1987.

52. K. Benson, H. Castedo, D. G. Goulias, with W. R. Hudson. 

Distress Identification Manual for the Long-Term Pavement Performance Studies (2d rev. ed.) (SHRP-LTPP/FR90-001). Strategic Highway Research Program, National 

Research Council, Washington, DC, October 1990. 

53. Strategic Highway Research Program, National 

Research Council, Washington, Distress Identification 

Manual for the Long-Term Pavement Performance 

Project (3d rev. ed.) (SHRP-P-338). Strategic Highway 

Research Program, National Research Council, 

Washington, DC, 1993. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-338.pdf.

54. Directive D-1, “LTPP Manual Distress Data Conversion,” 

Oct. 22, 1993. Federal Highway Administration, McLean, 

VA. http://ltpp.org.phtemp.com/dirs/DIS-01-49/D-01.pdf.

55. J. S. Miller and W. Y. Bellinger. Distress Identification 

Manual for the Long-Term Pavement Performance Project

(4th rev. ed.; FHWA-RD-03-031). Federal Highway 

Administration, Washington, DC, June 2003. http://

www.fhwa.dot.gov/pavement/pub_details.cfm?id=91.

56. Directive D-36, “Distress Identification Manual for the 

Long-Term Pavement Performance Program,” Oct. 20, 

2003. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-36.pdf.

57. J. S. Miller and W. Y. Bellinger. Distress Identification 

Manual for the Long-Term Pavement Performance 

Project (5th rev. ed.; FHWA-HRT-13-092). Federal 

Highway Administration, McLean, VA, May 2014. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/13092.

58. AC Distress Identification Guide (Pocket Edition, 

FHWA-RC-05-001); PCC Distress Identification Guide

(Pocket Edition, FHWA-RC-05-002); CRCP Distress 

Identification Guide (Pocket Edition, FHWA-RC-003); 

and the AC Distress Identification Guide (Pocket 

Edition, LTAP-05-001) for local agencies (out-of-print).

59. Directive D-16, “Distress Photographs Using Digital 

Cameras,” May 2, 2000. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

DIS_01-49/D-16.pdf.

60. Directive D-44, “Distress Survey Photographs,” Jan. 31, 

2006. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-44.pdf.

61. Directive D-6, “Policy on Distress Data Collection,” Apr. 

27, 1995. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-06.pdf.

62. Directive D-53, “LTPP Distress Data Quality—

Accreditation of Distress Raters,” May 14, 2012. 

Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_50-99/D-53.pdf.

63. Directive D-11, “Use of Distress Maps from Prior 

Surveys,” Feb. 7, 1997. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

DIS_01-49/D-11.pdf.
112    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

	64.	Directive D-39, “Initial Release of Distress Viewer and

Analysis (DiVA) Software, Version 1.0,” Aug. 30, 2004.

Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-39.pdf.

65. K. T. Hall and J. A. Crovetti. NCHRP Report 583: Effects 

of Subsurface Drainage on Pavement Performance: 

Analysis of the SPS-1 and SPS-2 Field Sections. Transportation Research Board, National Research Council, 

Washington, DC, 2007. http://onlinepubs.trb.org/

onlinepubs/nchrp/nchrp_rpt_583.pdf.

	66.	Directive P-37, “LTPP Manual for Profile Measurements

and Processing, Version 4.1, May 2004,” May 25, 2004.

Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/PRF/P-37.pdf.

	 67.	R. W. Perera and S. D. Kohn. Quantification of Smoothness 

Index Differences Related to Long-Term Pavement 

Performance Equipment Type (FHWA-HRT-05-054).

Federal Highway Administration, Washington, DC,

September 2005. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/05054/05054.pdf.

	68.	PROQUAL V1.4—User Documentation. Stantec,

Amherst, NY, June 1992.

	69.	Directive P-31, “Upgrade of PROQUAL Software to

PROQUAL2002 Version 3.0.2.1,” Sept. 3, 2002. Federal

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/PRF/P-31.pdf.

	70.	Directive P-41, “Upgrade of PROQUAL Software to

PROQUAL 2005 Version 5.0 Release 2 Build 2,” May 9,

2005. Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/PRF/P-41.pdf.

71. “ProVAL. View and analyze pavement profiles.” 

Software Web site. http://www.roadprofile.com/.

72. “Pavement Profile Viewer and Analyzer” (Product 

Brief; FHWA-RD-03-070). Federal Highway Administration, McLean, VA, June 2003. https://www.fhwa.dot.

gov/publications/research/infrastructure/pavements/

ltpp/reports/03070/03070.pdf.

	73.	Directive P-42, “Initial Release of Profile Export

(ProXport) Software Version 1.1,” May 9, 2005. Federal

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/PRF/P-42.pdf.

74. SHRP-LTPP Manual for Profile Measurements: 

Operational Field Guidelines, Version 1.0 (SHRP-LTPPOG-005). Strategic Highway Research Program, National

Research Council, Washington, DC, December 1989.

75. Manual for Profile Measurement: Operational Field 

Guidelines (SHRP-P-378). Strategic Highway Research

Program, National Research Council, Washington, DC,

1994. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-P-378.pdf.

	76.	Directive P-16, “Manual for Profile Measurements:

Operational Field Guidelines, Version 3.0, July 1997,”

July 28, 1997. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

PRF/P-16.pdf. 

	 77.	R. W. Perera, S. D. Kohn, and G. R. Rada. LTPP Manual 

for Profile Measurements, Version 3.1. Federal Highway 

Administration, McLean, VA, January 1999. http://ltpp.

org.phtemp.com/dirs/PRF/P-25.pdf.

	78.	R. W. Perera, S. D. Kohn, and G. R. Rada. LTPP Manual 

for Profile Measurements Operational Field Guidelines 

Version 4.0. Federal Highway Administration, McLean,

Va, September 2002. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/ltpp/

profman/profman.pdf.

	 79.	Directive P-37, “LTPP Manual for Profile Measurements and Processing, Version 4.1, May 2004,” May 25,

2004. Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/PRF/P-37.pdf. 

	80.	R. W. Perera, S. D. Kohn, and G. R. Rada. LTPP Manual 

for Profile Measurements and Processing (FHWAHRT-08-056). Federal Highway Administration,

McLean, VA. November 2008. http://www.fhwa.dot.

gov/publications/research/infrastructure/pavements/

ltpp/08056/08056.pdf.

	 81.	Directive P-48, “LTPP Manual for Profile Measurements and Processing, December 2013,” December 18,

2013. Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/PRF/P-48.pdf. See also

Directive P-49, “LTPP Manual for Profile Measurements and Processing, December 2013—Revised

Appendix B,” Mar.11, 2014. http://ltpp.org.phtemp.com/

dirs/PRF/P-49.pdf. 

	82.	R. W. Perera and G. E. Elkins. LTPP Manual for Profile 

Measurements and Processing. Federal Highway Administration, McLean,VA, December 2013. http://www.ltpp.

org/Profiler_Manual_12-19-13.pdf.

	 83.	G. E. Elkins, T. Thompson, A. Simpson, and B. Ostrom,

Long-Term Pavement Performance Information Management System: Pavement Performance Database User 

Reference Guide (FHWA-RD-03-088 (update)), Federal

Highway Administration, Washington, DC, November

2012. http://www.ltpp.org/PPDBuser2012.pdf.

	 84.	 “Comparison of Rut Depths from Dipstick and

PASCO Transverse Profile Measurements, Technical

Memorandum EC-42,” Texas Research and

Development Foundation, Jan. 30, 1990.

	 85.	Directive D-8, “Automated Dipstick Transverse Profile

Measurement Procedure,” Apr. 22, 1996. Federal

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/DIS_01-49/D-08.pdf.
6: coction of

	86.	 J. S. Miller and W. Y. Bellinger. Distress Identification 

Manual for the Long-Term Pavement Performance 

Project (5th rev. ed.; FHWA-HRT-13-092). Federal

Highway Administration, McLean, VA, May 2014.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/13092.

	 87.	R. W. Perera and G. E. Elkins. LTPP Manual for Profile 

Measurements and Processing. Federal Highway Administration, McLean,VA, December 2013. http://www.ltpp.

org/Profiler_Manual_12-19-13.pdf.

88. Traffic Monitoring Guide (FHWA-PL-01-021). Federal

Highway Administration, Office of Highway Policy 

Information, Washington, DC, June 1985. Subsequent

editions were issued in October 1992 (2nd ed.), February 

1995 (3rd ed.), May 2001(4th ed.), and September 2013

(5th ed.; FHWA-PL-13-015). http://www.fhwa.dot.gov/

policyinformation/tmguide/tmg_fhwa_pl_13_015.pdf.

	89.	G. R. Rada. SHRP-LTPP Monitoring Data: Five-Year 

Report (SHRP-P-696). Strategic Highway Research

Program, National Research Council, Washington, DC,

August 1994, p. 42.

	90.	Directive TDP-10, “Revised Traffic Monitoring Protocol

for LTPP Test Sites,” Apr. 30, 1998. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/TDP_01-49/TDP-10.pdf.

	 91.	Directive TDP-11, “Traffic Data Collection Equipment

Calibration,” Apr. 30, 1998 (rev. May 10, 1998). Federal

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/TDP_01-49/TDP-11.pdf.

	92.	Directive TDP-18, “Implementation of “Guide to LTPP

Traffic Data Collection and Processing,” Apr. 18, 2000.

Federal Highway Administration, McLean, VA. http://

ltpp.org.phtemp.com/dirs/TDP_01-49/TDP-18.pdf.

93. Federal Highway Administration. Guide to LTPP Traffic 

Data Collection and Processing. Federal Highway 

Administration, McLean, VA. Mar. 12, 2001.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/trfcol/trfcol.pdf.

94. B. Ostrom. LTPP Traffic Data Collection and Processing 

Guide, Version 1.3. Federal Highway Association, 

McLean, VA, October 2009. Available from LTPP

Customer Support Service Center (ltppinfo@dot.gov).
114    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP program has mounted three major data collection efforts that have 

improved the quality and quantity of its climate, traffic, and materials data, and 

has led the way in investigating pavement performance through forensic studies.

© Lane V. Erickson/Shutterstock.com
7: SPECIAL LTPP DATA COLLECTION EFFORTS    115

Special LTPP Data Collection Efforts

7

Introdu

The LTPP program has planned and executed three 

major efforts to enrich the LTPP database or to address 

areas where data did not meet the program’s expectations for quality or sufficiency. These programs went 

beyond the original experiments in the General Pavement Studies (GPS) and Specific Pavement Studies (SPS). 

So that pavement responses can be correlated with climatic conditions and traffic loads, the Seasonal Monitoring Program (SMP) gathered daily and seasonal weather 

data. To remedy the program’s lack of consistent, highquality monitoring traffic data, the LTPP SPS Traffic 

Data Collection Pooled-Fund Study, supported by the 

highway agencies, collected continuous classification 

and weight data at SPS projects where various design 

and rehabilitation strategies were being monitored. To 

supplement and correct incomplete materials data, 

Only data of the highest quality, in sufficient quantity, can be relied upon to yield true and useful answers to 

research questions. The LTPP program, with the assistance of expert peer groups, has continually reviewed 

and expanded its collected data to make the LTPP database more valuable to pavement researchers.

the Materials Action Plan was carried out. This chapter 

describes these “special” multiyear data collection efforts 

and the forensic investigations that have been conducted 

to increase understanding of pavement performance. 

SEASONAL MONITORING PR

Temperature and moisture-related changes in pavement 

structures, both within a day, from season to season, 

over the course of a year, and from year to year, can have 

significant impact on the structural characteristics of 

pavement layers, thus affecting the pavement’s response 

to traffic loads and, ultimately, its useful life. To attain a 

fundamental understanding of the magnitude and impact 

of temporal (daily, seasonal, and annual) variations in 
116    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Key Milestones in Special Data

Collection Efforts

1992 Seasonal Monitoring Program 

begins

2001 LTPP SPS Traffic Data Collectio

Pooled-Fund Study initiated

2003 Traffic data collection begins for 

traffic pooled-fund study

2004 Seasonal Monitoring Program en

2004 Materials Action Plan 

implementation begins

2004 LTPP develops framework for 

forensic investigation

2008 LTPP conducts four forensic studies

2009 Materials Action Plan completed

2014 LTPP SPS Traffic Data Collection 

Pooled-Fund Study ends 

pavement response and material properties due to the 

separate and combined effects of temperature and 

moisture variations, the Strategic Highway Research 

Program (SHRP) envisioned the SMP. The study 

concept received strong support from the LTPP stakeholder community and was also endorsed by the LTPP 

Pavement Performance Advisory Committee.

Unlike the GPS and SPS experiments, the SMP, 

which began in 1992, was not a planned experiment 

during formulation of the LTPP program in the 1985–87 

pre-implementation phase. Rather, the study evolved as 

an extension of the ongoing LTPP deflection testing 

activities that began in 1989. The original study concept 

was to perform deflection testing on a more frequent 

basis on a subset of LTPP test sections to provide the 

data necessary to “conquer the last frontier” in the 

structural evaluation of pavements—understanding the 

daily and seasonal variations in pavement deflections. 

However, the scope increased to include not only more 

frequent deflection basin and joint load transfer testing, 

but also more intensive profile and distress measureFigure 7.1. Distribution of instrumented sites in

LTPP Seasonal Monitoring Program.

ments as well as measurements of surface elevation, 

joint openings in Portland cement concrete (PCC) 

pavements, and various in situ surface and subsurface 

moisture and temperature parameters. The instrumented sites were widely distributed and represented a 

variety of climatic and soil conditions (figure 7.1).

It was envisioned that the products from the seasonal 

monitoring study would provide the means to link 

pavement response data obtained at random points in 

time to critical design conditions; the means to validate 

models for relationships between environmental conditions (e.g., temperature and precipitation) and in situ 

structural properties of pavement materials; and 

expanded knowledge of the magnitude and impact of 

the changes involved. When this study was terminated 

in 2004, it represented the end to perhaps one of the 

most successful undertakings within the LTPP program. The seasonal study provided input on the effects 

of temperature on falling weight deflectometer (FWD) 

deflection data, seasonal changes in performance of 

pavements, and the effects of heave (frost) and swell 

(expansive soils) on pavement performance. This information allowed for better decision making in the use of 

FWD data and update of current analytical models.

Detailed information about the SMP such as the 

scope, equipment, data collection procedures, data 

collected (onsite air temperature and precipitation 

data, subsurface temperature and moisture content 

data, and frost-related measurements), and monitoring 

frequency is discussed below.

© Gubin Yury/Shutterstock.com
Scope

Resource limitations made it impossible to monitor all 

LTPP test sections on a seasonal basis. Consequently, 

an experimental matrix of 32 cells was established 

addressing the following key pavement factors: 

•	 Pavement type—Thin asphalt concrete (AC), thick

AC, jointed plain concrete pavement, and reinforced 

PCC.

•	 Subgrade—Fine and coarse soil.

•	 Precipitation—Dry and wet conditions.

•	 Frost—Freeze and no-freeze conditions.

Traffic was not considered in the experimental matrix, 

as it was not felt critical to achieving the study objective.

During the test section recruitment effort, 3 sections 

were sought for each of the 16 AC pavement experiment cells and 1 section for each of the 16 PCC experiment cells—a total of 48 AC pavement test sections and 

16 PCC pavement test sections. To cover different soil 

and environmental conditions, the LTPP program 

identified 16 sites in each of the four LTPP regions. 

Ultimately, 63 of the targeted 64 test sections were 

selected from the GPS and SPS studies to populate the 

SMP experimental matrix.1

 These test sections were 

part of the SMP Phase I or Phase II monitoring frequency, as described later in this section.

Monitoring Equipment

At the start of the SMP only minimal funds were available, which meant that most of the options to be considered for instrumentation had to be “low tech” with 

manual data collection. Moisture data was collected 

with time domain reflectometer (TDR) probes connected to a Tektronics 1502B cable tester. Thermocouples connected to a precision multi-meter were 

used to collect temperature readings, and similarly, a 

resistivity probe was used to determine frost/thaw 

activity. A piezometer monitoring well (figure 7.2) was

chosen to monitor water levels. Rod and level surveys 

were also conducted at the time of FWD data collection to determine any pavement movement due to frost/

thaw activates or swelling of cohesive soils. Figure 7.3 

shows the SMP mobile monitoring equipment. Details 

of the evaluation, selection, and development of probes 

and other equipment used and challenges encountered 

are available in appendix C.

Validation of Data Collection Procedures

From 1990 to 1992, pilot studies and training sessions 

were held to select the instrumentation to be used for 

surface and subsurface moisture and temperature measurements, as well as to finalize the instrumentation

installation, and data collection guidelines. GPS test section 361011 which is a flexible pavement on I-481 near 

Syracuse, New York, was selected as the first pilot. 

The New York State Department of Transportation 

(NYSDOT) had conducted various temperature and 

frost/thaw studies in the past and had in-house expertise 

that could help with assembly of the instrumentation. 

The pilot installation on October 22–25, 1991, was attended by the LTPP program and contractor staff, NYSDOT, 

and CRREL (the U.S. Army Corps of Engineers’ Cold 

Regions Research and Engineering Laboratory). During 

the installation, CRREL provided insight on the instrumentation data collection along with the algorithms to 

analyze the voltage outputs from the thermocouples.

7: SPECIAL LTPP DATA COLLECTION EFFORTS    117

Figure 7.2. A piezometer monitoring 

and cap, used to determine ground water

levels.

Figure 7.3. Mobile monitoring equip

for downloading data collected at seasonal

monitoring sites.
118    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP regional support contractors had the opportunity to review the different instrumentation and procedures. A major consideration coming out of the pilot 

and subsequent data collection at this site was the need 

to refine the instrumentation and to automate the data 

collection process.2 

Following the initial pilot, the selection and development of instrumentation proceeded as plans were 

put in place for additional pilots, which were conducted at test section 163023, a rigid pavement near Boise, 

Idaho, in November 1991; and test section 308129, a 

flexible pavement near Billings, Montana, in August 

1992.3,4 A Campbell Scientific, Inc. (CSI) CR10 Datalogger was purchased, and software was developed to 

automate the data collection. After the evaluation of 

the TDR alternatives, a 3-prong, 203-mm-long, stainless steel tube probe was selected because of its accuracy, repeatability, and ease of installation. However, 

to reduce the instability of the electronic signal caused 

by differences in cable length, staff from the LTPP 

program and the Electronics Laboratory at the Federal 

Highway Administration’s (FHWA) Turner-Fairbank 

Highway Research Center designed a special TDR 

Figure 7.4. The moisture probe designed at the 

highway research center.

Figure 7.5. Schematic of the moisture probe that was used to obtain moisture conten

unbound base and subgrade materials in the SMP, designed at the FHWA highway research center.5

probe. This probe was designed to accurately measure 

the apparent length of the probe that is used to calculate the dielectric constant of the material surrounding 

the probe. The dielectric constant is an input to the 

calculation of moisture content in unbound base and 

subgrade materials. The final design was fabricated by 

the Electronics Laboratory specifically for the SMP 

data collection (figure 7.4 and figure 7.5).
7: SPECIAL LTPP DATA COLLECTION EFFORTS    119

Data Collected and Monitoring Frequency

Monitoring of select LTPP test sections that were also 

part of the seasonal study began in 1992 and had a more 

extensive and more frequent data collection monitoring schedule than the other LTPP test sections. The 63 

seasonal sites were monitored in SMP Phase I and 24 

of them were monitored in SMP Phase II. Although the 

two phases were monitored at different times throughout the year, the frequency of the data collected was 

monthly. However, in the spring and fall, the data were 

collected twice a month.

Regardless of the monitoring phase, the same data 

elements were collected for each SMP site. The core 

data elements collected were deflection, profile, and 

distress data. In addition, surface elevations, ambient 

temperature, precipitation, sub-surface moisture, subsurface temperature, frost depth, and ground water 

table elevation were also collected.6 It should be noted 

that procedures for cold weather FWD testing were 

developed specifically for the SMP.

SMP Phase I Monitoring

Approximately half of the seasonal test sections were 

monitored in alternate years—one loop of test sections 

in 1992, 1994, 1996, and 1998 and the other loop of test 

sections in 1993, 1995, 1997, and 1999. This data collection schedule was used because of the limited availability of the instrumentation, equipment, and LTPP 

program contracting resources. Once one loop of testing was complete, the instrumentation and equipment 

were rotated to the second loop of test sections for 

monitoring. However, the initial data collection cycle 

was extended by a year to compensate for problems 

encountered early in the SMP, including battery pack 

failures. The D-cell battery packs were replaced with 

gel cell batteries that could be recharged or continuously charged through a solar panel.

It was originally envisioned that seasonal monitoring would be performed on three alternate years per 

test section, from 1992 to 1997, but the instrumentation 

performed better than expected and there was a great 

deal of interest in the study by the participating highway agencies, so monitoring was extended until 1999. 

This period of monitoring would eventually be called 

the SMP Phase I monitoring, and it extended over an 

8-year period.

SMP Phase II Monitoring

As a result of the success of the SMP Phase I data collection activities, many highway agencies supported the 

continuation of the program, and planning began in 1998 

for a second phase (see sidebar). The objective of the SMP 

Phase II monitoring, which began in 1999, was to continue to provide the data needed to attain a fundamental 

understanding of the magnitude and impact of diurnal, 

seasonal, and annual variations in pavement response and 

properties due to the separate and combined effects of 

temperature, moisture, and frost penetration. However, 

unlike Phase I, this phase was limited to test sections that 

had available the full suite of data (i.e., monitoring, 

In April 1999, the LTPP program and its contractor 

staff held a Phase II pilot at the LTPP 510114 test 

site in Danville, Virginia, to install the instrumentation that was to be used in the Phase II monitoring 

and to perform a trial test (internal document, 

“LTPP Seasonal Monitoring Program, Phase 2 

Installation and Monitoring Activities,” April 

2006). Based on the results from this pilot, the 

LTPP program developed a manual to upgrade 

SMP sites to Phase II instrumentation. The photograph below shows a completed installation of 

monitoring equipment at the SMP Phase II pilot.
120    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

materials, and inventory data) required for pavement 

performance monitoring. Figure 7.6 shows the monitoring equipment installed at a Phase II seasonal site.

Twenty-four of the SMP Phase I monitoring test 

sections were selected for the SMP Phase II monitoring on the basis of data completeness, instrumentation 

condition, and willingness of the highway agency to 

support the effort. Data collection requirements 

remained largely the same as in the first phase, but the 

frequency of deflection testing was reduced, and the 

option was provided for either fixed-interval testing or 

direct-event testing, depending on the climatic regime 

at the site. The direct-event option was made possible 

in part because at 10 of the 24 test sections, equipment 

was upgraded to automate collection of moisture and 

frost/thaw data when triggered by precipitation or 

specified soil temperatures. Unlike temperature measurements, which were continuously collected during 

SMP Phase I monitoring, moisture and frost/thaw 

depth measurements had been collected manually at 

4-hour intervals on the days of deflection testing, using 

the mobile monitoring equipment. During SMP Phase 

II, moisture and frost/thaw depth data were collected 

continuously when the new equipment was triggered 

by conditions (i.e., when the temperature reached a 

certain degree, frost information was collected). This 

direct-event testing equipment was rotated among the 

24 test sections. 

Quality Control Software

Software was developed for field quality control (QC) 

and review of the SMP data. In 1995, during Phase I, the 

LTPP program developed the ONSFIELD software to 

QC and review onsite data (temperature and rainfall), 

and the MOBFIELD software to review the mobile data 

(moisture and frost/thaw).7

 In addition, Seasonal Monitoring Program Check, or SMPCheck, was developed 

for central office processing and loading of data into the 

LTPP database, with a manual released in 1996.8

During Phase II, the CR10 operating software was 

updated to the PC208 Windows version. This resulted 

in changes to the data collection routines and provided 

a better user interface, eliminating the need for the 

CR10 procedural routines developed in the DOS version.9 A CR10 procedural program along with documentation was developed to provide a systematic 

approach for the SMP data collection,10 and later a 

comprehensive data collection guidelines document 

was created to ensure high-quality data would be collected.11 LTPP program directives were issued to provide resolutions for data collection and processing 

issues from October 1993 to November 2002 and to 

document changes in procedures. 

Training and Data Interpretation

Training sessions were held throughout the SMP when 

new versions of the equipment or software were made 

for processing and interpreting SMP data. Editing of 

the plots to “null” timeframes that contained no data, 

the removal of bad data, and the interpretation of TDR 

traces were part of the training. This training was often 

conducted in conjunction with data training for the 

automated weather stations (chapter 6). 

An evaluation of the moisture determination from 

TDR methods was also done. This method of developing and identifying inflection points, along with the 

Topp et al. procedure for determining the volumetric 

moisture content of soils from dielectric constant,12

was adapted by the LTPP program.13 As both manual 

TDR traces on paper and automated traces were collected, an interpretation manual was developed for the 

TDR traces. This manual outlined the procedures on 

how to interpret different trace types and generate volumetric moisture values from manual traces.14 

The evaluation of the automated resistance/resistivity data to determine frost/thaw depths was more difficult, as no mathematical solution could be applied (since 

the input voltage was not recorded). As such, manual 

interpretation of the traces was required. Evaluating 

the 2-point and 4-point resistivity, manually collected 

Figure 7.6. SMP Phase II seas

monitoring equipment installation

at the Lake Ontario State Parkw

site on SR 947A in western

York.
7: SPECIAL LTPP DATA COLLECTION EFFORTS    121

at the time of site visits, had the same limitations. Using 

the 4-point resistivity to determine soil moisture and 

other conditions was also considered impractical as 

soil volume changes with weather and seasons. 

TDR and resistivity data collected from the seasonal 

monitoring sites do not directly provide information 

useful to pavement engineers. Rather, the data must be 

interpreted to develop subsurface moisture content 

and frost condition information. The LTPP program 

has sponsored four studies to compute these parameters. Two initial studies were conducted to compute 

frost conditions and moisture content from data 

collected through 1998.15,16 After these studies were 

completed, additional data were collected but were not 

routinely interpreted. Considering this, FHWA sponsored two other studies to evaluate the methodologies 

used in the initial studies and to compute frost and 

moisture content for all of the data in the LTPP database. The procedures used were modified from the 

original studies, and computations were made for all 

collected SMP data.17,18

SMP data collection ended in October 2004, for reasons ranging from failing sensors, sections being rehabilitated or going out of study, and financial constraints.19

At the completion of Phase II data collection, the 

instrumentation and equipment from most of the SMP 

sites were removed and returned to the LTPP regional 

offices (with the exception of the in-ground instrumentation). Exceptions were in Arizona and Ohio, where

the SMP site/equipment was transferred to the highway agency. At some of the sites, a forensic study of the 

condition of the instrumentation was undertaken in 

which the in-ground instrumentation was removed and 

examined. The installation, decommissioning, and recommissioning of seasonal monitoring sites are documented in reports that detail the instrumentation, its 

location within the pavement layers, material properties, and any problems.20 

The SMP projects have provided pavement designers 

and researchers with an abundance of research-quality 

environmental data. Combined with measurements taken at the automated and virtual weather stations, these 

data have already proven useful in evaluating and modifying rigid pavement design procedures, refining the 

selection of performance-graded binders, evaluating 

seasonal load restrictions, and defining moisture and 

frost penetration prediction models.

LTPP SPS TRAFFIC DATA COLLEC

POOLED-FUND 

A 1996 program assessment (chapter 11) revealed major 

traffic data deficiencies in the LTPP database. To 

address this issue, the LTPP program and the Transportation Research Board Expert Task Group (ETG) 

on LTPP Traffic Data Collection and Analysis studied 

the problem and developed an action plan.21 This 1999 

action plan provided guidelines to improve traffic 

monitoring by assuring uniformity of data collection 

equipment across States and Provinces, establishing 

regular equipment calibrations, and ensuring that a 

sufficient quantity of data would be collected to support research and product development.22

Around this time, weigh-in-motion (WIM) technologies were greatly improved; however, their cost and 

the additional staff needed to maintain, calibrate, and 

operate the systems properly made it impossible to 

install a permanent WIM system at every LTPP test 

site. Therefore, the LTPP program and the Traffic ETG 

(figure 7.7) decided to collect traffic loading data only at 

SPS experiments, specifically SPS-1 (structural factors 

for flexible pavements), -2 (structural factors for rigid 

pavements), -5 (rehabilitation of AC pavements), and 

-6 (rehabilitation of jointed PCC pavements).23 To 

implement the traffic monitoring action plan, FHWA, 

with the support of the American Association of State 

Highway and Transportation Officials (AASHTO) and 

the participation of many highway agencies, initiated 

the LTPP SPS Traffic Data Collection Pooled-Fund 

Study, TPF-5(004), in 2001.

 The objective of this study was to improve the quality and increase the quantity of monitored traffic data 

(volumes, classifications, and weights) at selected LTPP 

SPS test sites. Since 2003, this multiyear study has 

collected “research-quality data” for at least 5 years at 

The LTPP SPS Traffic Data Collection 

Pooled-Fund Study aimed to improve 

the quality and increase the quantity 

of monitored traffic data at select LTPP 

SPS test sites.
122    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

28 of the 84 SPS sites using bending plate, load cell, and 

quartz WIM sensors. For the purpose of this study,

research-quality data was defined to be at least 210 days 

of data (in a year) of known calibration meeting LTPP’s 

performance requirements for steering and tandem 

axles, gross vehicle weight, bumper-to-bumper vehicle 

length, vehicle speed, and axle spacing, as listed in table 

7.1. In this study, the first contracted WIM equipment 

was installed in 2005 in Illinois; the last installation 

was in Indiana in 2008. These two locations along with 

others are still producing research-quality data. 

Many pooled-fund studies use the funds contributed by participating States for any area of the study. In 

this study, however, each State’s contribution goes to 

its own data collection needs at its SPS projects. Six of 

the 28 participating States (figure 7.8) recognized the

value of the study—as well as the potential for advancing their own traffic data collection activities—and 

decided to become donor States. Their contributions 

allowed the LTPP program to expand data collection.

Before the traffic pooled-fund study began, the 

LTPP program field-tested the installation of the WIM 

equipment and the calibration and validation protocols at five pilot locations. 

These pilot studies are discussed in the 

next section.

Pilot Studies Conducted to

Test Protocols

The LTPP program developed a series of 

protocols and guidelines to acquire uniformly collected, research-quality traffic 

data. The guidelines include a suggested 

performance-based equipment specification for equipment replacement, a 

performance specification for validating equipment 

operation in the field, and pavement smoothness criteria. 

In addition, a field protocol addressing the calibration 

and validation procedures was prepared for all traffic 

data collection activities.24

Over the summer and fall of 2001, LTPP staff oversaw five pilot studies to verify that the new performance 

specifications and field procedures were feasible. The 

pilots looked at both piezoelectric cable and bending

plate sensor systems installed in AC and PCC pavements. One of the pilot sites was used to test the reinstallation process, and a side-by-side comparison of 

the principal sensor systems, piezoelectric cable, and

bending plate was performed at another site.25

The following sites were examined as part of the 

pilot studies in 2001:26

1.	 Arizona SPS-6 site 040600. The traffic monitoring

equipment included inductance loops and bending 

plates in all lanes installed in a PCC pavement about 

500 ft (152 m) in length. The WIM installation process was tested at this location.

2. Florida WIM site not part of the LTPP experiment.

The traffic monitoring equipment included inductance loops/piezoelectric cable sensors as well as

inductance loops/bending plate installations in the

northbound and southbound lanes in an AC pavement.Aside-by-side comparison ofthe piezoelectric

cable and bending plate sensors at this non-LTPP 

site showed that the piezoelectric cable did not

perform as well as the bending plate. 

3. Maryland SPS-5 site 240500. This site had a system 

with a pair of piezoelectric cable sensors without

direct temperature compensation and a pair of 

Table 7.1. LTPP WIM system performance requireme

Pooled-Fund Site Factor 95 Percent Confiden

Limit of Error

Loaded Single Axles ± 20 percent 

Loaded Axle Groups ± 15 percent 

Gross Vehicle Weights ± 10 percent 

Vehicle Length greater of 1.5 ft or ± 3 percent 

Vehicle Speed ± 1 mi/h 

Axle Spacing Length ± 0.5 ft [150 mm]

Figure 7.7. Traffic ETG members who provided technical guidance

direction to the traffic pooled-fund study (left to right: Andrew Nichol

Elizabeth Stolz, Patricia Hu, David Cebon (Chair), Anne-Marie McDonnell,

and Richard Reel). Not pictured but also instrumental in developi

study were members Larry Scofield (former Chair), Richard Quinle

Richard Rogers, and James Kram
inductance loops installed in asphalt. The sensors 

had been installed in late 2000 and had never been 

calibrated. The previous sensors were also piezoelectric cables and were still visible in the pavement. 

Only one piezoelectric cable was used to capture

weight data. The original sensors at this site were 

from a bending plate that had never produced satisfactory results. In addition to Michigan and Texas, 

this site was used to test the field procedures.

4. Michigan SPS-1 site 260100. This site was visibly 

rough, as vehicles were observed to bounce as they 

approached the scale. The initial analysis was based 

on 80 runs split between three trucks, and there 

were several truck breakdowns during testing.

5. Texas SPS-1 site 480100. The equipment was a 

bending plate installed in asphalt and used four test 

trucks to field validate the procedures. 

As a result of the pilot studies, the following conclusions were reached:

•	 The equipment performance specifications were

achievable with current practice and technology.

•	 The smoothness specification was too restrictive for

actual field conditions and required revision.

•	 The recommendation of bending plate sensors in

smooth PCC did produce research-quality data.

•	 The recommended field practices, including the

conditions for vehicles, speeds, and temperatures, 

were achievable.

Although the LTPP pavement smoothness specification was found to be too restrictive, further testing in 

several States resulted in revisions to the specification, 

which later was adopted as the AASHTO Standard 

Specification for Smoothness of Pavement in Weighin-Motion Systems.27 The pilot studies also verified 

that WIM equipment options used in the pooled-fund 

study should include load cells (figure 7.9), bending 

plates (figure 7.10), or quartz piezoelectric sensors

(figure 7.11). Following the pilots, the data collection 

and processing methods were adopted for use in the 

traffic pooled-fund study.

Traffic Pooled-Fund Study Process

To satisfy the requirements for SPS traffic data collection 

and implement the objectives of the traffic pooled-fund 

study, FHWA selected two independent contractors. 

One contractor installed, maintained, and replaced WIM 

equipment; performed daily QC checks of the data; and 

7: SPECIAL LTPP DATA COLLECTION EFFORTS    123

Figure 7.8. Participating States in the LTPP SPS Traffic Data Collection Pooled-Fund St

Map shows the donor States, States with assessments only, and weigh-in-motion equipment

installed by the State or the LTPP contractor.

Contractor WIM Installations

State WIM Installations

One-Time Site Assessment

Donor States

Non-Participating States

CA

AZ NM

CO

KS

TX

FL

LA

AR

TN

MS AL

WA

ID

UT

GA

NY

VA

IN PA

MN

WI

MI

OH IL

NC

ME

CT

NJ

MD

MB

DE
124    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

submitted the data on a weekly basis to the LTPP 

regional support contractors for further QC and processing. The second contractor performed field evaluation and validation of all WIM equipment installations, 

including equipment installed by highway agencies. 

Highway agencies that installed and maintained their 

Figure 7.9. Load cell WIM installat

Figure 7.11. Installation of quartz piezoelec

WIM sensor spanning a full lane.

Figure 7.10. Staggered bending plate

sensors installed in concrete pavement.

own WIM equipment sent the data directly to the LTPP 

regional support contractors for processing. 

An extra step in processing the traffic data was to 

check for gross data changes over time. The LTPP 

regional support contractors used the LTPP Traffic 

Analysis Software to check the weekly data against a 

reference data set. The reference data set covers the 

14 days immediately following a successful calibration 

and validation of the WIM system and provides the typical vehicle classification and loading conditions for the 

site. Data reviewed after the 14-day period are expected 

to reasonably match the reference data set (figure 7.12). 

Although the pooled-fund study ended in 2014, its 

field validation, data collection, and other activities 

continue to be centrally managed by the LTPP program (at select sites) with the support of the contractors and highway agencies.

Products of the Study

Some of the products that have been developed as a 

result of the traffic pooled-fund study are the LTPP Field 

Operations Guide for SPS WIM Sites (WIM Data Quality 

Guidelines), a glossary of WIM terms, LTPP vehicle classification table, and new traffic defaults for use with the 

Mechanistic-Empirical Pavement Design Guide, as well 

as the AASHTO smoothness specification. Guidelines 

for equipment calibration checks and equipment model 

specifications were also developed and are available 

through the LTPP Customer Support Service Center 

(Email: ltppinfo@dot.gov). The information gathered, 

documentation produced, and lessons learned from this 

effort were shared with pavement and traffic engineers 

and traffic data collectors in WIM workshops that were 

held by the States. This study led to significant advances 

in the accuracy and reliability of permanent traffic monitoring equipment and has significantly improved the 

availability and quality of monitored traffic data for pavement, bridge, and other analysis studies.

MATERIALS ACTION

Collection of accurate and reliable materials data is a

critical element of the LTPP program. As discussed in 

chapter 11, in 2004 the LTPP program undertook a 

major effort, the SPS Materials Action Plan, to fill iden-
tified gaps in the materials data for the SPS projects. 

Efforts begun in 1997 had brought improvement, but 

serious gaps remained. The plan for resolving materials data deficiences was laid out in an internal LTPP 

document, “LTPP SPS Materials Data Resolution: 

Update and Final Action Plan, August 2004.” The plan 

addressed three major areas of materials data needs for 

SPS-1, -2, -5, -6, and -8 projects:

•	 Resolution of materials data gaps—urgently required.

•	 Aging and new materials testing—highly desirable.

•	 Collection of materials samples—desirable.

The sampling and testing requirements that addressed 

these three areas were based on criteria defined in the 

internal Final Action Plan. These criteria were based 

on missing data per layer type and the requirement 

that three test results were needed for each layer. 

The initial Materials Action Plan pilot took place in 

Maryland in 2005.28

To get the plan underway, the LTPP regional support contractors developed site-specific sampling 

plans and coordinated all activities with the highway 

agencies. The regional contractors were present during the sampling operations to ensure that the plans 

(approved by the LTPP program and the highway 

agencies) were followed. They identified and marked 

all sampling locations, performed some of the field 

testing, and were responsible for labeling, packing, and 

shipping samples to the laboratories involved in the 

testing and for completing the sampling data sheets. 

The highway agencies’ responsibilities were to provide traffic control, perform field sampling, and patch 

the holes where samples were taken. Due to the multiple activities at the site, coordination between the 

agency’s field crew and the regional support contractor’s crew was essential to ensure that samples were 

properly collected and tests were performed without 

interruption. A new, Web-based system was developed 

to track the layers and samples as they were collected, 

shipped, and tested, and as laboratory results were 

loaded into the database.

One challenge encountered during the SPS materials 

sampling was the lack of material to perform some of the 

laboratory tests. To resolve this, samples were combined 

for testing. A special form was used to log the different 

samples that should be combined for performing certain 

tests. For example, two or more bags of unbound granular material were combined to perform the resilient 

modulus testing (P46), and four cores were used to 

perform the asphalt resilient modulus testing (P07). 

In the field, the regional contractor staff had the 

responsibility of performing some of the tests, mainly 

7: SPECIAL LTPP DATA COLLECTION EFFORTS    125

Figure 7.12. Screen shot from LTPP Traffic Analysis Software showing loadings of Cla

traffic over a 5-week period in March 2011. “Comp” line represents the reference data set.

New Mexico, SPS-1 Test Section 35010
126    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

the dynamic cone penetrometer for unbound layers, as 

shown in figure 7.13, and also thickness measurements 

and moisture determination.

The plan was to use two laboratories, one to perform the resilient modulus testing and one to perform 

the remaining tests. In the end, the contract for both 

testing functions was awarded to a single contractor; 

thus all testing was performed at one location with the 

exception of the coefficient of thermal expansion (P63) 

test, which was performed in the Concrete Laboratory 

at the FHWA highway research center. 

The contracting laboratory was AASHTO-certified 

for performing standard procedures on soils, aggregates, 

asphalt binder, asphalt emulsion, and hot-mix asphalt 

and also had a current laboratory assessment from 

the ASTM Cement and Concrete Reference Laboratory. 

The contracted laboratory’s quality management 

system was certified for compliance with AASHTO 

Standard Practice R 18, Standard Practice for Establishing and Implementing a Quality Management 

System for Construction Materials Testing Laboratories. The contractor was required to have a QC program to provide control over the activities that can 

affect the quality of materials laboratory testing. The 

LTPP program conducted a startup inspection visit in 

October 2005, with additional visits in the following 

years to inspect resilient modulus testing procedures 

and quality management compliance with AASHTO 

Standard Practice R 18. Upon approval, data that passed 

the quality assurance (QA) review were transmitted to 

the LTPP regional support contractors for input to the 

LTPP database. The primary objective of the QC/QA 

activities was to ensure that the required data collected 

were of high quality.

Under the Materials Action Plan, approximately 

95 percent of the materials tests ordered from the 

LTPP contract laboratory were able to be tested using 

the rigorous LTPP test protocols, with a total of 10,863 

tests performed. Although the collection of samples for 

future use was strongly supported by the LTPP program, it was assigned a lower priority due to financial 

constraints. Of the desired samples, 74 percent of the 

12-inch (305-mm) core samples and 61 percent of the 

4-inch (102-mm) core samples were delivered to the 

Materials Reference Library (1,544 cores in total), and 

1,488 samples of bulk material were added to the collection. Data from tests not previously performed were 

added to the database, corrections were made to some 

pavement structure information from new field investigations, and, where possible, previous data deficiencies were corrected. The final report for this effort 

provides extensive detail on the amount of data collected and the reduction in missing data elements in 

the LTPP database.29

FORENSIC STU

Data that can be collected at the end of a test section’s 

life can help to improve understanding of the causes of 

premature pavement failure and, in exceptionally longlasting pavements, the reasons for superior performance. Ideally, whenever an LTPP pavement test section 

fails, is scheduled for replacement or rehabilitation, or is 

removed from an LTPP experiment for other reasons, a 

forensic study would be conducted to investigate in 

detail the processes of pavement deterioration and failure. By illuminating the causes and mechanisms of pavement distresses, forensic data can be used to design and 

implement an effective rehabilitation strategy for the 

pavement and prevent similar failures from occurring in 

the future. Forensic data are essential to improving 

design practices and updating construction techniques 

and can be valuable in the development or calibration of 

performance-prediction models. End-of-life evaluations also provide an opportunity to collect missing or 

incomplete test section data for the LTPP database.30

Figure 7.13. LTPP regional support contractor staff

the dynamic core penetrometer to determine the strength

and density of the subgrade at the SPS-5 site in Minnesota.
Forensic investigations are considered an important 

element of the LTPP program; however, funding constraints made implementation difficult. In 2004, the 

program developed a manual, Framework for LTPP 

Forensic Investigations—Final, to promote consistency 

in forensic studies and maximize their benefits.31 In 

2008, FHWA funded four LTPP forensic studies. These 

studies examined hot-mix asphalt pavements that 

were exhibiting cracking and rutting:32 

•	 Arizona SPS-5 (rehabilitation of AC pavements)—

To identify the cause of higher-than-expected rutting 

in the recycled sections (figure 7.14).

•	 Ohio SPS-1 (structural factors for flexible pavements)—To determine why the project had many 

more pavement distresses than the SPS-9 (SuperpaveTM) project that is located in the same area.33

•	 New York SPS-8 (environmental effects in the absence of heavy loads)—To investigate the observed 

early pavement distresses, which occurred in the 

absence of heavy loads.34

•	 Texas SPS-5 (rehabilitation of AC pavements)—To

determine why the project was performing substantially better than the surrounding pavement with 

similar pavement characteristics, and to examine 

reflection cracking and rutting in individual layers.35

Other highway agencies have conducted their own forensic studies as well, notably Connecticut in connection 

with the Seasonal Monitoring Program, Texas (SPS-1), 

Colorado (SPS-5), Arizona (SPS-9, Superpave), Virginia

(SPS-1), Quebec (GPS-3), and North Carolina (GPS-2).

In November 2012, in support of NCHRP Project 

01-49, Guidelines for Conducting Forensic Investigation of Highway Pavements, the LTPP program sponsored a national workshop that brought together 

representatives of highway agencies to discuss their 

current agency practices and review the new national 

guidelines developed in Project 01-49.36 The workshop 

presented the complete forensic investigation process 

that was established in the guidelines, from study initiation through the use of nondestructive and laboratory techniques to investigation closeout. 

The LTPP program has played an important role in 

developing national guidelines that promote the effectiveness and efficiency of future forensic investigations 

of LTPP test sections as well as other pavement studies 

by highway agencies. Future forensic investigation of 

LTPP test sections that have failed prematurely or have 

shown unexpectedly good performance will contribute great value to the understanding of the variables 

that affect pavement performance.

SUMMA

The LTPP program mounted three successful multiyear 

data collection efforts to improve the quality and quantity of the program’s monitoring of climate, traffic, and 

materials data. The SMP was a 12-year study with the 

goal of enriching the understanding of the effects of climatic variations in temperature and moisture on pavement responses. This program resulted in a wealth of 

new environmental data. 

The LTPP SPS Traffic Data Collection Pooled-Fund 

Study was organized to improve the LTPP traffic data

by providing uniformity in data collection equipment, 

regular equipment calibrations, and daily QC checks of 

the data. This 11-year data collection effort gathered 

upwards of 400 million vehicle records and 2.3 billion 

individual axle-load records—the largest quantity of 

research-quality traffic data ever assembled. These traffic data are now available to researchers in raw form or 

summarized as axle-load probability distributions.

The Materials Action Plan was carried out over 5 

years to address priority materials data needs for SPS-1, 

-2, -5, -6, and -8 projects. Under this effort, 10,863 materials tests were performed under the rigorous LTPP test 

7: SPECIAL LTPP DATA COLLECTION EFFORTS    127

Figure 7.14. Workers prepare a trench for fore

investigation of an SPS-5 test site in Arizona.
protocols. The materials data were improved significantly, and more than 3,000 cores and other samples 

were added to the Materials Reference Library. 

Finally, a rich source of performance data is the 

forensic investigation of test sections as they reach the 

end of their useful lives. The LTPP program has developed a framework for forensic evaluation of pavements, participated in the development of national 

guidelines for forensic studies, and conducted four 

studies on hot-mix asphalt test sections.

The investment in the special efforts described 

above and the ongoing, routine data collection activities discussed in chapter 6 have yielded an unprecedented amount of pavement performance information. 

The systems developed to store, manage, secure, and 

distribute this information to the public are described 

in the next chapter.

REFEREN

1.	G. R. Rada, G. E. Elkins, B. Henderson, R. J. Van Sambeek,

and A. López, Jr. LTPP Seasonal Monitoring Program: 

Instrumentation Installation and Data Collection 

Guidelines, Version 2.1 (FHWA-RD-94-110). Federal 

Highway Administration, McLean, VA, January 1995,

p. I-2. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/94110/94110.pdf. 

 2. Seasonal Testing Instrumentation Pilot: GPS 361011, 

IH 481 S.B., E. Syracuse, NY, Oct. 22–25, 1991. Available 

from LTPP Customer Support Service Center 

(ltppinfo@dot.gov).

 3. Seasonal Testing Instrumentation Pilot: GPS 163023, IH 

84 W.B., W. Boise, ID, Nov. 5–7, 1991. Available from LTPP 

Customer Support Service Center (ltppinfo@dot.gov).

 4. Seasonal Testing Instrumentation Pilot: GPS 308129, 

US-12 E.B., N.W. Billings, MT, Aug. 11–12, 1992. Available 

from LTPP Customer Support Service Center 

(ltppinfo@dot.gov).

5.	G. R. Rada, G. E. Elkins, B. Henderson, R. J. Van Sambeek,

and A. López, Jr. LTPP Seasonal Monitoring Program: 

Instrumentation Installation and Data Collection 

Guidelines, Version 2.1 (FHWA-RD-94-110). Federal 

Highway Administration, McLean, VA, January 1995,

p. II-3. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/94110/94110.pdf. 

6.	G. R. Rada, G. E. Elkins, B. Henderson, R. J. Van Sambeek,

and A. López, Jr. LTPP Seasonal Monitoring Program: 

Instrumentation Installation and Data Collection 

Guidelines, Version 2.1 (FHWA-RD-94-110). Federal 

Highway Administration, McLean, VA, January 1995,

p. III-1. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/94110/94110.pdf.

 7. Directive SM-10, “Use of ONSFIELD and MOBFIELD 

QC Programs,” Apr. 1, 1995. Federal Highway 

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/SMP/SM-10.pdf. 

 8. LTPP Seasonal Monitoring Program Seasonal Monitoring Program Check Users Guide, Version 2.5. Federal 

Highway Administration, Pavement Performance 

Division, McLean, VA, Oct. 28, 1996.

 9. Directive SM-44, “Upgrade of OnsPlus Software to 

Version 1.09,” Feb. 21, 2002. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

SMP/SM-44.pdf.

	 10.	G. R. Rada, G. E. Elkins, B. Henderson, R. J. Van Sambeek,

and A. López, Jr. LTPP Seasonal Monitoring Program: 

Instrumentation Installation and Data Collection 

Guidelines, Version 2.1 (FHWA-RD-94-110). Federal 

Highway Administration, McLean, VA, January 1995,

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/94110/94110.pdf.

11.	G. R. Rada, G. E. Elkins, B. Henderson, R. J. Van Sambeek,

and A. López, Jr. LTPP Seasonal Monitoring Program: 

Instrumentation Installation and Data Collection 

Guidelines, Version 2.1 (FHWA-RD-94-110). Federal 

Highway Administration, McLean, VA, January 1995.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/94110/94110.pdf.

 12. G. C. Topp, J. L. Davis, and A. P. Annan. “Electromagnetic determination of soil water content: Measurements in coaxial transmission lines.” Water Resource 

Research, 16:574–582, 1980.

 13. Directive SM-13, “TDR Trace Interpretation Method 

for Calibration and Function Checks,” Aug. 17, 1995. 

Federal Highway Administration, McLean, VA.

http://ltpp.org.phtemp.com/dirs/SMP/SM-13.pdf.

 14. Directive SM-28, “Interpretation Manual TDR Traces,” 

Aug. 7, 1998. Federal Highway Administration, McLean, 

VA. http://ltpp.org.phtemp.com/dirs/SMP/SM-28.pdf.

 15. H. A. Ali and S. D. Tayabji. Determination of Frost 

Penetration in LTPP Sections, Final Report (FHWARD-99-088). Federal Highway Administration, 

McLean, VA, September 1999. www.fhwa.dot.gov/

pavement/pub_details.cfm?id=127.

 16. Y. J. Jiang and S. D. Tayabji. Analysis of Time Domain 

Reflectometry Data from LTPP Seasonal Monitoring 

Program Test Sections—Final Report (FHWA-RD-99-

115), Federal Highway Administration, July 1999. 

www.fhwa.dot.gov/pavement/pub_details.cfm?id=128.

128    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
17.	O.I. Selezneva, Y. J. Jiang, G. Larson, and T. Puzin.

Long Term Pavement Performance Computed Parameter: 

Frost Penetration (FHWA-HRT-08-057). Federal 

Highway Administration, McLean, VA, November 2008.

www.fhwa.dot.gov/pavement/pub_details.cfm?id=640.

 18. D. Zollinger, S. Lee, J. Puccinelli, and N. Jackson. 

Long Term Pavement Performance Computed Parameter: Moisture Content (FHWA-HRT-08-035). Federal 

Highway Administration, McLean, VA, March 2008.

www.fhwa.dot.gov/pavement/pub_details.cfm?id=567. 

 19. Directive GO-36, “Termination of LTPP Seasonal 

Monitoring Program,” Oct. 27, 2004. Federal Highway 

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/GO_01-49/GO-36.pdf.

 20. Forensic studies are available from LTPP Customer 

Support Service Center (ltppinfo@dot.gov).

 21. Action Plan for Improving Quality of LTPP SPS Traffic 

Loading Data. Draft. Office of Infrastructure Research, 

Development, and Technology, Federal Highway 

Administration, McLean, VA, 1999.

 22. Eighth Letter Report of the Transportation Research 

Board Long-Term Pavement Performance Committee. 

Transportation Research Board, The National 

Academies, Washington, DC, Dec. 27, 1999. http://

onlinepubs.trb.org/onlinepubs/sp/ltpp_letter_8.pdf.

 23. D. Walker and D. Cebon. “The Metamorphosis of 

Long-Term Pavement Performance Traffic Data.” 

TR News, No. 277, November–December 2011, p. 9–17.

 24. “Pilot Projects Kick Off Traffic Data Pooled-Fund Study.” 

Focus (FHWA-RD-02-008), March 2002. http://www.

fhwa.dot.gov/publications/focus/02mar/pilot.cfm.

 25. D. Walker and D. Cebon. “The Metamorphois of 

Long-Term Pavement Performance Traffic Data.” 

TR News, No. 277, November–December 2011, p. 12.

 26. SPS Traffic Site Evaluation—Pilots Summary and Lessons 

Learned. Federal Highway Administration, McLean, VA,

2002, pp. 23–48. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/reports/

lessons/lessons.pdf.

 27. AASHTO MP 14-08, Aug. 1, 2008. www.techstreet.com/

cgi-bin/detail?doc_no=aashto%7Cmp_14_08; product_

id=1583807.

 28. Materials Data Resolution Sampling and Testing Plan, 

SPS-5 Project 240500, US-15 NB, near Frederick, MD, 

May 2005. Available from LTPP Customer Support 

Service Center (ltppinfo@dot.gov).

29.	P. N. Schmalzer, R. W. Plett, and G. E. Elkins. LTPP

Specific Pavement Studies (SPS) Materials Action Plan 

Final Report (FHWA-HRT-10-049). Federal Highway 

Administration, McLean, VA, August 2010. http://www.

fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/10049/10049.pdf.

 30. “Forensic Evaluations of the Long Term Pavement 

Performance (LTPP) Test Sites.” LTPP Newsletter, vol. 

4, no. 2 (Spring 2008), p. 1. http://www.fhwa.dot.gov/

publications/ltppnews/08060.pdf.

 31. MACTEC Engineering and Consulting of Georgia, Inc. 

Framework for LTPP Forensic Investigations—Final. 

Federal Highway Administration, McLean, VA, April

2004. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/framework/

framework.pdf.

 32. “In Brief.” LTPP Newsletter, vol. 4, no. 4 (Fall 2008), 

p. 3. http://www.fhwa.dot.gov/publications/

ltppnews/09021.pdf.

 33. S. M. Sargand, I. S. Khoury, A. G. Harrigal, L. M. 

Sargent, and H. Kim. Evaluation of Pavement Performance on Del-23—Interim Report—Forensic Study for 

Sections 390103, 390108, 390109, and 390110 of Ohio 

SHRP U.S. Rt. 23 Test Pavement. Ohio Department 

of Transportation, Federal Highway Administration, 

and Ohio University, Columbus, OH, January 2006. 

http://www.dot.state.oh.us/Divisions/Planning/SPR/

Research/reportsandplans/Reports/2006/

Pavements/14768-ForensicReport.pdf.

34.	C. Olmedo and R. Korczak. “Forensic Pavement Study:

Practical Methods, Analysis and Applications.” Paper 

presented at the Annual Conference of the Transportation Association of Canada, Halifax, NS, Sept. 26–29, 

2010. http://conf.tac-atc.ca/english/resourcecentre/

readingroom/conference/conf2010/docs/p3/olmedo.pdf.

 35. Fugro Consultants, Inc. Forensic Investigation Report on 

the LTPP Texas SPS-5 Project. July 2009. Available at 

LTPP’s InfoPave Web site.

 36. G. R. Rada, D. J. Jones, J. T. Harvey, K. A. Senn, and 

M. Thomas. NCHRP Report 747. Guide for Conducting 

Forensic Investigations of Highway Pavements. National 

Cooperative Highway Research Program, Transportation Research Board of the National Academies, 

Washington, DC, 2013. http://onlinepubs.trb.org/

onlinepubs/nchrp/nchrp_rpt_747.pdf.

7: SPECIAL LTPP DATA COLLECTION EFFORTS    129
130    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP database provides nearly three decades of pavement performance 

information and continues to evolve in size, content, and structure.

© gyn9037/Shutterstock.com
8: Storage, Growth, Seurity and Di

Storage, Growth, Security, and

Dissemination of the Ltpp Data

8

Introducti

The founders of the LTPP program knew that to 

achieve the primary engineering objectives of the program, it would be necessary to establish a robust pavement performance research database. Previous efforts 

to collect research-quality pavement performance data 

had been short-lived and geographically limited, and 

they did not secure the data for future use. The LTPP 

program has successfully accomplished the major 

challenge of developing, maintaining, and updating a 

database to support a national approach to improving 

pavement engineering and management tools.

Today the LTPP database is recognized by the 

Transportation Research Board (TRB) as LTPP’s principal operational tool, its principal product, and its 

principal legacy to future highway researchers and 

practitioners.1

 The primary objective of the LTPP 

The extraordinary volume and complexity of pavement performance data present a real challenge to 

the LTPP program—providing quality control, security, and ease of access are the primary considerations. 

Fortunately, as the mountain of data grows, computer technology advances in ways that continue to 

benefit the program. 

database is to serve as a central repository for data 

collected by the program in a format that is secure, of 

known quality, easy to disseminate, and compatible 

with current database software. Successful completion 

of this objective has required many changes to the 

database over time. This chapter summarizes the 

development of the LTPP database and includes an 

overview of major structural and processing changes, 

improvements in computer hardware technology, and 

upgrades in database management and operating 

system software. Information on the state of the database with references to other information resources are 

also included. Although some of the procedures protecting data quality are described here, chapter 9 provides 

a full discussion of LTPP quality control/quality assurance (QC/QA) processes used by the program.
132    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Key Milestones in Storing and

Disseminating LTPP 

1989 LTPP database created using 

Oracle® 5

1991 First data release

1993 Switch from DOS-based data entry

to Windows

1995 FHWA assumes data distribution

function from TRB

1997 Database operations, engineerin

specifications, computer programming, and management merged in 

one contract 

1997 FHWA-LTPP Customer Support

Service Center and Customer 

Survey processes started

1997 DataPave 1.0 releas

1998 AIMS data release policy establishe

2002 New policy provides access to all 

LTPP data regardless of quality 

status

2002 DataPave Online launch

2003 First Standard Data Releas

2006 Customer Support Service Center 

moves to FHWA’s highway research

center

2008 IMS moves to FHWA’s highw

research center

2009 FHWA pledges to continue LTPP

operations

2011 FHWA moves all LTPP data to FHW

research center 

2011 Data entry centralized throug

online LTPP Data Entry Porta

2012 AIMS files centralized online with

AIMS Data Entry Porta

2014 Debut of LTPP InfoPav

The overall system used to manage information 

intended for LTPP’s public dissemination is called the 

Information Management System (IMS) (figure 8.1). 

The system’s major components are LTPP products, 

the Pavement Performance Database (PPDB, or LTPP 

database), and the Ancillary Information Management System (AIMS). Products are program results 

and tools that can be used to improve pavement performance management and are discussed in chapter 

10. At the time of this report, the LTPP database contained 330 million data records: pavement-related 

data, computed parameters, and summary weather 

and traffic data. The AIMS contains 2.7 million additional files: documents, videos, photos, and raw data 

files created in the LTPP program. Together these 

© kubais/Shutterstock.com
8: Storage, Growth, Seurity and Di

collections occupy a significant amount of electronic 

storage (over 5 TB).

An introduction to the IMS is not complete without 

a review of the structure and development of the LTPP 

database. Most LTPP data are collected and processed 

by the four LTPP regional support contractors; other 

data are provided by central sources. Each regional 

support contractor is responsible for loading and processing data for the region’s test sections. These data 

are input into the national database, which is operated 

by the central technical support services contractor 

(referred to as the “technical assistance contractor” 

earlier in the program). The technical support services 

contractor is responsible for managing the IMS, loading data from other central data sources, performing 

extended central checks on all data, creating some central computed parameters, and creating data releases 

to the public on a periodic cycle. The LTPP Customer 

Support Service Center staff is responsible for data dissemination and data user support. The following sections describe how this data processing structure has 

matured over time.

DEVELOPMENT 

INFORMATION MANAG

Over the course of the LTPP program, changes in the 

program’s sponsorship and contractual relationships 

and advances in information technology have influenced the development of the program’s information 

management processes. This section briefly describes 

how the data were managed, from point of collection 

through dissemination to data users, during four 

time periods. 

SHRP-LTPP Database Process (1989 

After the national long-term pavement performance 

database was established under Strategic Highway 

Research Program (SHRP) management in 1989, the 

LTPP IMS, which included the LTPP data and its supporting information, consisted of a central node (the 

national IMS, or NIMS) located at the TRB office in 

Washington, DC, and the regional nodes (regional IMS, 

or RIMS), one at each of the four LTPP regional offices. 

Figure 8.2 illustrates the initial LTPP database process, 

dataflow, quality checks, and data releases under central 

operation of the LTPP database by TRB. The four SHRPLTPP regional coordination office contractors (under 

the Federal Highway Administration (FHWA) called 

“regional support contractors”) had primary responsibility for collection and entry of the data into the RIMS. 

The data were then transferred into a “shadow database” at TRB where all of the regional databases were 

combined. The shadow database served as intermediate 

storage while QC checks were run centrally on the data 

by central SHRP-LTPP contractor staff. A feedback loop 

to the regional contractors was used to address issues 

with data failing a QC check. Data exchange between 

the RIMS and the NIMS was accomplished by mailing 

cassette tapes to avoid the high cost of telecommunicating large volumes of data.

Products • Research findi

    • New software too

    • Test guidelin

    • Measurement protocols

LTPP Information Management Sy

PPDB   • Pavement struc

    • Material properties

    • Distress measurement

    • Clima

    • Traffic loa

AIMS    • Raw data fil

    • Distress map images

    • Test section photos & vid

    • Scanned data forms

Figure 8.1. The LTPP Information Manageme

(IMS) includes Products, the Pavement Perfo

Database (PPDB), and the Ancillary Informati

Management System (AIMS).

The LTPP Information Management System 

includes LTPP Products, the Pavement 

Performance Database, and the Ancillary 

Information Management System.
134    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Information supporting the data, such as distress 

photographs, laboratory data sheets, and core samples, 

was retained by the regional contractors for future reference. In the early years of the program, this information, which would evolve into the AIMS, was not stored 

centrally or made available for release. 

Figure 8.2 also illustrates two data release categories. Category 1 was data released back to the participating agency where the test section was located. 

Category 1 data could be released without passing data 

quality checks. The category 2 data release was to the 

general public, and these data had to pass five levels of 

data quality checks. These data quality checks and 

their impact on how the LTPP program disseminated 

the data are discussed in the following Data Release 

Policy section.

The LTPP database is a relational database optimized for data storage and data entry. The database 

consists of records with multiple elements. Although 

one or more elements in a record may be subject to 

automated review, the record is tagged with the worst 

outcome of all data elements in the record. Data are 

released at the record level, not as elements from a 

record. In the release discussions that follow, data and 

records should be considered synonymous. 

Data Release Policy

In the early years of the LTPP program, data released 

to the public were required to pass a series of data quality checks. In preparation for release of data to the public, five types of QC checks, labeled from A to E, were 

performed by the NIMS software as part of the level 1 

processing. The checks were applied in series, and data 

did not proceed to the next check until satisfying the 

previous one. Not all data elements in a record were 

checked at every level. 

A—Random checks to ensure correct RIMS-NIMS upload exchange.

B—Data dependency checks to ensure that basic section

information (location, experiment, etc.) is recorded.

C—Minimum data search for critical elements (e.g., 

friction data should include skid number).

D—Expanded range checks to identify data elements

that fall outside an expected range. 

Figure 8.2. Overview of the initial SHRP-LT

process, data flow, and releases circa 1989 to 1994, with

the database of the Strategic Highway Research Pro

(SHRP) offices residing at the Transportation Re

Board (TRB). (Adapted from J. T. Maddock 199

Data 

Available 

to all

Requesters 

(Category 2)

Release 

Newsletter 

Data

Source

Shadow

Database

at TRB 

SHRP

Regional

Offices

National

Pavement

Performance

Database

at TRB

Periodic

Releases

Request 

for Data by

Data Source

(Category 1) 

Data Checks

Regional

Coordination

Office

Contractor or

Data Source 

Quality Checks 

Central SHRP-LTPP

Contractor

E—Intramodular checks to verify consistency of data 

within or between records.3

Data passing all five level 1 checks, qualified as a level 1, 

category 2, data release to the general public. Data passing the level 1 checks were also called “level E” data 
8: Storage, Growth, Seurity and Di

because the field named RECORD_STATUS contained 

an entry of E to indicate a record had passed.

A level 2 set of data QC checks, tied to what was 

called an “experiment release,” was planned but not 

implemented. The plan was for data passing level 1 

checks to be subject to the following four types of additional global, cross-modular checks:

F—Intermodular cross checks to verify existence and 

consistency of data for related categories.

G—Experiment and cell assignment checks based on 

collected data.

H—Various checks involving frequency distributions 

and bimodal and variance checks.

I—Statistical checks for outliers, missing data, and 

completeness of experiment. 

Although the full progression of QC checks to level 2 

for all data was not realized, the planned level 2 checks 

have since been applied in a more limited way as part 

of some of the level 1 checks, other forms of postupload checks, and formal data studies.

Beginning in January 1991, four data releases were 

made available to the public, upon request, at 6-month 

intervals. All were level 1 releases of data from the General Pavement Studies (GPS).4 Details of the QC/QA 

processing are discussed in chapter 9.

FHWA-LTPP Database Process (1995 to

Following the end of SHRP and transfer of the LTPP 

program to FHWA, management of the LTPP IMS 

remained with SHRP under a contract between the 

two parties from 1992 to 1995. In 1995, TRB transferred 

management of the LTPP IMS to FHWA. Operation of 

the central LTPP database became the responsibility of 

the LTPP pavement database contractor, and the central hardware was moved to the contractor’s location in 

Oak Ridge, Tennessee.

Also circa 1994 to 1995, a major shift of responsibility 

to the regional support contractors for primary QC processing of LTPP data was being implemented. This 

change was inspired by the relatively long time lag 

between the results of central QC checks from the central LTPP contractor and subsequent resolutions/data 

corrections by regional contractors. To provide automation and central review of QC check results, the central 

LTPP contractor created a software program named 

“Browser.” The Browser program allowed the regional 

contractors to comment on data failing a QC check and 

provided rudimentary scripts to perform manual 

upgrades to a record’s QC status. In concept, all manual 

upgrades to data records failing a QC check would be 

reviewed by the central LTPP contractor and the comments explaining these manual QC upgrades would be 

made available to data users. Figure 8.3 illustrates the 

changes in data processing responsibilities and flow 

from the initial database model shown in figure 8.2.

In 1998, a new process was introduced to document the outcome of data review and correction 

processes. The Data Analysis/Operations Feedback 

Report (DAOFR) became a method by which any user 

of LTPP data could raise questions about data 

elements or data processes and initiate review and 

corrective actions by the LTPP program. The DAOFR 

became a method of systematically documenting 

issues identified by researchers and others about 

completeness and validity of data. 

During this time period, supporting data to be associated with AIMS continued to be retained by the 

regional support contractors. 

In 1997, FHWA combined the central technical 

assistance services for pavement engineering, database 

management, and traffic engineering into a single contract. This was a significant milestone for the LTPP 

database: it fostered effective, direct communications 

among these three technical professions that previously were split into three separate contracts. A true 

synergy developed among the pavement engineering 

staff, who understood what the pavement engineering 

data meant; traffic engineers, who knew what the traffic data meant; and the computer database staff, who 

knew how best to use available computer technology to 

store, process, and disseminate the combined pavement and traffic data that comprises the majority of the 

LTPP database. It was around this time that the program developed formal guidelines for adding new elements to the database, modifying existing elements, 

and resolving issues. The guidelines provided conventions and specifications to ensure that engineers and 

software programmers could communicate effectively 

and efficiently to develop the database.5

 
136    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

to the physical pavement structure existing at the time. Adding 

the sequential numbering system to indicate all work activities 

performed on a test section during LTPP monitoring provided 

a convenient method to indicate these changes. Implementing this major change to the database required close collaboration 

between the LTPP program 

office and its contractor staff 

to review the technical details 

of the change and to resolve 

inconsistencies. This change was 

reflected in the database and in 

data releases from November 

2001 forward. 

During this period, there was 

explicit recognition of the value 

of LTPP information that exists 

outside of the database for researchers. Loss of AIMS-eligible 

data due to media failures led to 

a transition from floppy disks to 

CD-ROMs as the primary backup and storage medium in 2001. 

This change created the foundation of the structure 

for AIMS and the first submissions for central distribution. In 2005, the types of ancillary data included 

were expanded, the structures revised, and the storage and distribution medium changed to DVD.

Data Release Policy

A database paradigm shift occurred in 2002 with a 

change to LTPP’s data release policy. The decision was 

made to release all LTPP data contained in the database, regardless of its quality, to the public, free of 

charge.6 Previously, only data that had passed the automated QC checks or had been manually upgraded by 

LTPP contractor staff to level E (previously referred to 

as category 2) were generally available to the public. 

So, those interested in all LTPP data during that time 

period had to make a special request that needed to be 

approved by the LTPP program office. This policy creFigure 8.3. Functional diagram of LTPP data processing flow circa 1995 

which allowed regional support contractor offices to make manual quality control

(QC) upgrades and explain them in the Browser software

External Data

Sources

Regional

Databases

Custom Data Rele

Level E On

LTPP Central Contractor

Feedback

Central Production

Database 

LTPP Central Contractor

LTPP Regional Contractors

QC Checks

Data Corrections

Manual Upgrades

LTPP Regional Contractors

Secondary QC Checks 

LTPP Central Contractor

Browser Comments

Data Release Policy

During the 1995 to 1999 time period, the data release 

policy for the NIMS remained the same as it was during the SHRP-LTPP years: data released to the public 

had to pass all level 1 QC checks and be at level E. The 

comments explaining manual upgrades made by the 

regional support contractors were provided to data 

users. In 1998, a policy for release of data contained in 

AIMS was established.

FHWA-LTPP Database Process (2000 to

An interesting LTPP database improvement was made in 

2001, when the LTPP program began recording pavement structural changes by incrementing the test section 

construction number each time a maintenance or rehabilitation activity occurred on a test section. The construction number is a critical field in many LTPP database 

tables that links pavement performance measurements 
8: Storage, Growth, Seurity and Di

ated problems of perception over the quality and 

amount of available LTPP data.

Level E records should not be considered better or 

worse than records at other levels for various reasons:

•	 Although the automated QC checks are extensive,

they are not capable of detecting all types of data 

issues. The checks have changed and continue to 

evolve over time as new problems are discovered. 

Records that may have passed a QC level previously 

may not pass now.

•	 The structure of the LTPP database record contains

multiple data fields of related data elements. Just 

because one data element fails a check does not 

mean that other values contained in the same record are not valid.

•	 There have been no direct means for a data user to

know which records have passed all QC checks and 

which records have been manually upgraded in 

status. A plan was developed to provide this information to the data user, but it has not yet been 

implemented. A data user has to manually peruse 

the comments tables to understand previously recognized data issues.

•	 Releasing only level E data masked potential missing data issues: a data user did not know whether or

not data were missing at level E. 

By releasing all available LTPP data, the LTPP program 

gave data users the opportunity to evaluate data quality 

concerns relative to their intended analysis objective 

for themselves.

LTPP Standard Data Release

Another major milestone in LTPP database history, 

concurrent with the change in LTPP database release 

policy, was the development of the LTPP Standard 

Data Release (SDR) in Microsoft® Access®. The idea for 

the LTPP SDR started with a national review of data by 

the pavement engineers who were part of LTPP’s technical support services contractor staff. Because of the 

high cost of licenses for Oracle® (the software used for 

the LTPP database) and the complexity involved in 

working with it, the LTPP regional support contractor 

staff sent the data in Microsoft Access format to the 

technical contractor for review prior to releasing the 

data to the public. The Microsoft Access format 

allowed the pavement engineers to simply “look” at the 

data, sort the data by fields to find outliers, and perform other automated calculations to detect data 

anomalies without extensive Oracle knowledge. 

The concept for the SDR was born from the recognition that pavement engineers performing research are 

not likely to have easy access to an Oracle license. Since 

the Microsoft Access database format was already being 

used to disseminate LTPP data to the program’s pavement engineers, it was a simple step to make this format 

available to the public as a standard release format. The 

only drawback to using Access was that the LTPP database had to be divided into a series of smaller databases 

due to a 2-GB limit on the size of an Access database. 

The first LTPP SDR was distributed in January 2003 in 

CD-ROM format. This was LTPP data release 15 and 

contained data through summer 2002. 

Figure 8.4 illustrates the functional LTPP database 

flow and QC checks that existed in 2011. Notice that the 

technical support services contractor no longer 

reviewed data generated by the Browser program or 

reran the automated QC checks at the national level. 

Central checks of the data were manual checks performed by the technical support services contractor 

based on data issues discovered since the last data 

upload, changes to existing data modules, new data 

modules, and verification of action taken by regional 

support contractors in the DAOFR process. AIMS data 

were submitted directly to the database archive at 

FHWA’s Turner-Fairbank Highway Research Center in 

McLean, Virginia (hereafter called “FHWA’s highway 

research center”) without formal quality data inspections by the technical support services contractor.  

The first LTPP Standard Data Release 

was issued in January 2003 as SDR 15. 

It contained data collected through 

summer 2002.
138    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Figure 8.4. Functional diagram of LTPP data processing flow circa 2000 to 2011. The central contractor 

support services contractor) performs secondary quality control (QC) checks before adding data to the Pavem

Performance Database (PPDB) and the Central Traffic Database (CTDB) and preparing the Standard D

for delivery to the LTPP Customer Support Service Center (CSSC) at the FHWA Turner-Fairbank Hig

Center (TFHRC) for distribution. The Data Analysis/Operations Feedback Report (DAOFR) form is used 

data issues and their resolution. Ancillary Information Management System (AIMS) data flow directly from the

regional support contractors to the central archive.

External Data

Sources

Regional

Databases

Publi

Distribution

DAOFR

Feedback

Central Production

Database 

LTPP Central Contractor

LTPP Regional Contractors

QC Checks

Data Corrections

Manual Upgrades

LTPP Regional Contractors

Secondary Data Checks

and Data Studies 

LTPP Central Contractor

AIMS

Data

PPDB &

CTBD

Databases

Standard Data Release

Delivered to LTPP Customer 

Support Service Center

at FHWA TFHRC

Central Archival Databases 

at FHWA TFHRC
8: Storage, Growth, Seurity and Di

FHWA-LTPP Database P

(2011 to present)

In 2009, FHWA developed a strategic plan to maintain 

and further develop the LTPP database. This internal 

document provided for continued customer support 

service to LTPP data users, public access to the LTPP 

database via the Internet, and use of the Internet for 

data submissions by the regional support contractors. 

Development of a new LTPP Data Entry Portal 

(LDEP) began in 2010 and was completed in 2011.7 By 

creating a single central data entry portal accessible 

over the Internet, the LDEP reduces program costs for 

purchasing and upgrading software and equipment in 

the regional offices and allows for secure and efficient 

transfer of LTPP data from the regional support contractors through the portal. This change also keeps the 

LTPP database current with computer technology. To 

convert the LTPP database to an online system, the following migration process was used:

•	 A new server and associated hardware were procured. (The history of database hardware is summarized in the following section.)

•	 The existing LTPP database, automated data entry

software, LTPP Traffic Analysis Software (LTAS), 

and QC software were ported to Internet-compatible 

software platforms using a semi-automated process 

followed by a manual review of the code, debugging, 

and necessary changes.

•	 Approximately 95 manual data entry forms for currently active data modules were modified to a current 

version of Java to work on the new system and to 

extend their shelf life for future platform changes. 

•	 Approximately 50 QC programs for active database

modules were altered to change database referential 

code, alter mathematical algorithms, and adapt the 

report functions to the Internet platform. 

•	 Approximately 28 programs that automate the process of reading electronic data and creating records 

in the database tables were altered.

•	 The LTAS software was set up in a separate but

integrated portion of the data entry portal. Changes 

to accommodate the Internet-based computing 

platform included modification of data loader programs, QC routines, and data graphing functions.

•	 Following traditional software testing procedures,

the internal set of alpha tests performed by the technical support services contractor was followed up 

with beta testing by the regional support contractors.

•	 At the end of the alpha and beta test periods, the

LDEP was opened for a validation test.

– The validation test consisted of a limited period 

of dual data entry into the old and new systems.

– At the end of the dual entry period, comparisons 

were made between the old and new systems to 

validate that the new system was performing 

correctly.

•	 The new Internet-based system was officially

opened for full operation in 2011.8

•	 For security,the contents ofthe old system were electronically archived and stored in the central LTPP 

repository at FHWA’s highway research center.

•	 A newly established automated software issue

reporting and tracking system was developed to 

perform corrections, updates, and modifications to 

the system as new issues are discovered.

Figure 8.5 illustrates the greater centralization of data 

processing that currently exists. The shift from regional database servers to a central database server at 

FHWA’s highway research center allows secondary 

central data QC functions to be performed continuously as the regional support contractors enter data. 

From a logistical viewpoint, centralization also simplifies rollout of new database software and central data 

updates since the need for consistency in software 

between the central server and four different regional 

database servers no longer exists. Updates to software 

and data are now done only on the central operational 

database server, and processing and QC checks are 

carried out in a secure Internet zone. Since the introduction to the Web-based LTPP database, operations 

are continually refined to keep current with computer 

technology and to improve overall operations.9,10,11

The other significant operational change in LTPP 

electronic data file management allowed by the 
140    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

FIGURE 8.5. Functional diagram of LTPP data processing flow circa 2011 to present created by integration of LTPP

regional databases into the LTPP central operational database. Processing and quality control (QC) checks are carried

out in the secure Internet zone. The FHWA Turner-Fairbank Highway Research Center (TFHRC) maintains the Information Management System (IMS).

External Data

Sources

LTPP Customer

Support Service

Center

LTPP InfoPaveTM

LTPP Data Entry Portal

Distributes Standard 

Data Release

Provides Custom

Data Extractions

Provides Customer 

Support

National LTPP IMS

at FHWA TFHRC

Pavement Performance Database

LTPP Traffic Database or LTPP Traffic Data

Ancillary Information

Standard Data Release

Reference Library

LTPP Products

SECURE INTERNET ZONE

Primary Data 

Processing QC

LTPP Regional 

Contractors

Secondary Data 

Processing QC

LTPP Central

Contractor

LTPP Regional Contractors
8: Storage, Growth, Seurity and Di

migration to a Web-based paradigm was creation of 

the AIMS Data Entry Portal (ADEP) within the LDEP. 

AIMS, which contains raw data forms, images, electronic recorded data, and interpreted data sets, is comprised of a set of electronic files organized into a logical 

file directory storage structure. It is updated over time 

as new documents are created from continuing data 

collection and operational activities. To support periodic updates and changes, the ADEP was set up within 

the LDEP using the TortoiseSVN open source version 

control system. Use of this file management software 

structure now allows the LTPP program to add new 

files as updates to the central archive instead of performing complete replacements. 

HISTORY OF L

MANAGEMENT SYSTEM H

AND SOFT

Changes in LTPP data storage and dissemination were 

driven by the rapid increase in data collected and by 

advances in computing technology. The rising capabilities and falling costs of computer hardware, accompanied by advances in database software, made it possible 

to keep pace with the challenges inherent in a program 

of this magnitude. This section describes the computer 

hardware and software used throughout the years to 

store LTPP data and information. 

IMS Hardware

The history of the LTPP IMS hardware is outlined in 

table 8.1, and photographs appear in figure 8.6, figure 

8.7, figure 8.8, and figure 8.9. 

These changes in computer hardware technology 

are indicative of the technology challenges faced by the 

LTPP program. Servers that cost more than $120,000 

at the start of the program, with very limited capacity, 

now cost less than $10,000 with capacities and capabilities that were hard to imagine in 1987. 

Between 2006 and 2007, FHWA management began 

plans to consolidate operations of the LTPP Customer 

Support Service Center and the IMS from Oak Ridge, 

Tennessee, to FHWA’s highway research center. This 

shift in operation started with locating a suitable space 

at the research center to house the new national database server where the pavement performance data 

would reside. The AIMS data that support the pavement data were also consolidated at the research center—all of the raw data files, images of paper data forms, 

and video in electronic format. Relocation of the LTPP 

IMS was completed in spring 2008.12,13 In 2009, both 

the pavement performance database and AIMS were 

installed on the newly purchased, state-of-the-art 

server at the research center. 

IMS Software

Software operating systems and database management 

systems have changed at a pace similar to hardware 

changes. The LTPP program has continually updated 

its software in response to these changes. The LTPP 

database is a relational database originally implemented in Oracle 5 format. As of this writing, the IMS 

operating system is Windows Server 2008 and the 

database is implemented in Oracle 11g. Due to its widespread use, Microsoft Access 2000 is used to distribute 

the SDR, and both Microsoft Access and Excel® can be 

used to download LTPP data online. 

The Oracle relational database management system (RDBMS) was initially selected by SHRP in 1989 

because it was the only RDBMS available at the time 

that supported different computer operating systems. 

The initial plan for development of the LTPP IMS was 

for the regional support contractors to operate the 

RIMS on Microsoft Disk Operating System (MSDOS®) personal computers and for the NIMS to run 

on the VMS operating system used on the UNIX®-

based computer operated by TRB. VMS® stands for 

Virtual Memory System, which provides a multiuser, 

multitasking environment, and was introduced in 1979 

by DEC with the first VAX® minicomputer. The Oracle 

5 RDBMS product was selected because it could run 

on both the MS-DOS and VMS operating systems and 

included Structured Query Language for data manipulation and maintenance, forms management, menu 

management, and reporting tools. Also, many thirdparty products were available at the time that interfaced with this software.14 

Over the years, the LTPP program migrated the 

database software from the initial MS-DOS–based 
142    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Table 8.1. IMS computer hardware used in the LTP

Year Purpose Model  Capacity  Cost* 

1989 RIMS Compaq® 25 MHz, 2 MB RAM, 300 MB hard drive; $12,50

NIMS 80386-25DX Everex Cartridge Tape Dri

1989 NIMS  Digital Equipment Corp. 33 MHz, 32 MB internal memory; maximum I/O $120

 (DEC) MicroVAX 3900 rate 3.3 MB/sec; 9-track external tape

 drive; connected to the Compaq® 386-25 via 

 high-speed Ethernet link

1992 Additional traffic Optical disk drives 1,000 MB $5,000

data storage 

capacity in the RIM

1993 NIMS, to increase  DEC Alpha 3000 96 MB RAM, 1 GB internal SCSI disk drive; $160

storage and computa- AXP 400 S 10 GB external storage (hard drive chassis

tional speed (about containing three 1.6-GB disk drives, Qualstar®

3 times faster than 6250 bpi SCSI 9-track tape drive, and Winchest

MicroVAX) FlashDAT Turbo single-tape backup subsystem

with 4 GB capacity 4 mm tape drive) 

1993 RIMS, for database  Ideal 486DX2-50 50 MHz, 512 MB hard drive, 14,400-baud modem $7

storage

1995 RIMS, for traffic data Micron® Pentium® 90 MHz $6,70

quality processing

1997 NIMS, for database Compaq ProLiant Pentium®, 166 MHz, 4.3 GB hard drive storage $35,00

server 1500 5/166P

2001 NIMS, one each for  DellTM PowerEdgeTM Dual Intel® Petium III Xeon®, 1 GB SDRA

production database 4400 5 No. 36-GB 10,000 RPM SCSI hard drives in 

and test database RAID-5 array, DLT4000 40/80 GB internal t

RIMS backup, uninterruptible power supply

2001 NIMS  Dell Precision 530 Dual Intel Petium III 1 GHz processor, 7

RIMS  Workstation GB of 800 ECC RDRAM, 40-GB hard drive, 12X

 32X CD read-write drive, 16X DVD read dr

2005 NIMS  Dell/EMC AX100SC 1 TB storage $9,

 external Storage Area 

 Network Fibre Channel

2007 NIMS, to replace  Dell PowerEdge 2900 2 Dual-core Intel Xeon 5120 1.8 GHz processors, $

PowerEdge 4400 2 GB RAM, internal RAID-5 hard drive array

 876 GB storage, PowerVaultTM 110T-LTO2-L tape 

 backup, 2200VA uninterruptible power supply, 

 external 500 GB USB disk drive, 48X IDE C

VD-ROM 

2009 NIMS, for both LTPP  Dell PowerEdge 2900III Dual quad-core Intel Xeon 5450, 3.0 GH

database and AIMS processors, 32 GB RAM, internal RAID-5 h

drive array, 8 TB storage, external RD1000 US

drive with removable hard disks for data backup, 

2200VA uninterruptible power supply, 16X DVD-R

2011 Central LDEP  Dell PowerEdge R510 Dual 6-core Intel Xeon 5675, 3.06 GHz processors, $

 Web server 32 GB RAM, 1 TB RAID 1 hard drive array (two 1

drives) for the OS, 12 TB RAID-5 hard drive arra

(eight 2TB drives using one as a hot spare) for data, 

external RD1000 USB drive with removable har

disks for data backup, USB hu

RIMS = Regional Information Management System; NIMS = National Information Management System; AIMS = Ancillary Information Manag

System; LDEP = LTPP Data Entry Porta

* Cost shown in dollar value for the year the equipment was purchased.
8: Storage, Growth, Seurity and Di

Figure 8.9. DellTM PowerEdgeTM 2900III ins

in May 2009 at FHWA’s Turner-Fairbank Highw

Research Center to serve as the secure cent

repository for LTPP electronic data into

future. The server contains 8 TB disk stor

dual quad core Xeon® 3 GHz processors, 32 GB

RAM, and the Windows® Server 2008 64-bi

operating system.

Figure 8.8. Compaq® ProLiant 1500

running Windows® NT 16-bit operating sys

used for the central database server 1997

to 2001.

Figure 8.6. DEC MicroVAX 3900 computer running 

operating system, used as the first LTPP National Inform

Management System (NIMS) server from 1989 to 1993

Figure 8.7. The LTPP DEC Alpha 3000 AXP 4

system running the UNIX® operating system, used for

server functions from 1993 to 1997.
144    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

computer operating system platform to Microsoft 

Windows® platforms. One of the first significant 

migrations occurred in 1993, when, with the conversion from Oracle 5 to 6, the DOS-based manual data 

input forms were converted to run under Microsoft 

Windows using a third-party software package. Some 

of the manual data entry forms programmed early in 

the program are still based on an MS-DOS sequential 

function key-based technology to reduce the programming costs associated with point-and-click 

technology. 

LTPP’s technical support services contractor 

maintains an internal Software Performance Report 

(SPR) database that documents all changes to LTPP 

database software performed by the contractor. The 

SPR database is an excellent tool that was developed 

to document and track software-related issues. It 

contains all critical information: problem description, 

problem resolution, submission and resolution dates, 

and other details. SPRs can be submitted by the 

regional support contractors for problems they have 

experienced using the LTPP database software or by 

the technical support services contractor for issues 

requiring correction. 

The next upgrade challenge was to adapt the LTPP 

custom software to the new 64-bit Windows operating 

system and Oracle version for the new Dell PowerEdge 

2900III installed at FHWA’s highway research center 

in 2009. The LTPP program has developed a systematic approach based on quality management principles 

to meet the challenges of implementing new computer 

software, in order to continue to serve the program’s 

changing software needs. 

DATA STO

The LTPP program stores the majority of the performance data collected from the LTPP test sections in an 

electronic relational database format. In addition, the 

program stores raw data files and other information 

about the test sections in AIMS. 

Pavement Performance Datab

The pavement performance data are stored in a relational database, meaning that it is composed of separate, but related, tables of data. All data are stored in 

simple row/column format tables. Rows are referred to 

as records and columns as fields. Each row of data in a 

table is uniquely identified by the values in a primary 

key column or a combination of columns. In addition, 

relationships exist among the tables of the database 

that are represented by common data values stored in 

more than one table. For example, many data tables 

contain State code and SHRP identification columns, 

which uniquely identify the test sections and projects. 

These fields are used to locate or join data for a specific 

test section from different tables.

Database Modules

The data storage tables in the LTPP database are organized into modules containing similar tables. With the 

exception of the tables in the Administration module, 

the first part of the table name identifies the module to 

which a particular table belongs. In the LTPP SDR, the 

modules are as follows:

Administration (ADM)—The master test section control table consisting of metadata tables that describe 

the structure and content of the database, and the general comments tables. 

Automated Weather Station (AWS)—Site-specific climatic information measured at automated weather 

stations installed near almost all Specific Pavement 

Studies (SPS) -1 (structural factors for flexible pavements), -2 (structural factors for rigid pavements), and 

-8 (environmental effects in the absence of heavy loads) 

project sites. 

Climate (CLM)—General environmental information 

from government-operated weather stations located 

near test sections. Data may be from a single site within 7 mi (11 km) of the section or from a site-specific statistical estimate based on sites within a 50-mi (81-km) 

radius.

Data Compilation Views (DCV)—Data compiled from 

other existing tables with the primary intent of reducing the number of tables a user needs to examine for 

similar types of data elements. 

Dynamic Load Response (DLR)—Dynamic load response 

instrumentation data from SPS test sections located in 

North Carolina and Ohio. 
8: Storage, Growth, Seurity and Di

Ground Penetrating Radar (GPR)—GPR measurements 

performed on a subset of SPS-1, -2, -5 (rehabilitation of 

asphalt concrete), and -6 (rehabilitation of jointed 

Portland cement concrete) sections performed in 2003.

Inventory (INV)—Inventory information for all GPS 

test sections and for SPS sections originally classified 

as maintenance and rehabilitation experiments. Tables 

in this module contain general pavement information 

on the sections’ pavement structure prior to their 

inclusion in the LTPP program. 

Maintenance (MNT) and Rehabilitation (RHB)—Maintenance and rehabilitation data are combined into one 

module in the SDR because they are closely related. 

The data tables, however, are identified by MNT or 

RHB in the table names. 

Monitoring (MON)—A series of submodules organized 

by data type. The submodules contained in the MON 

module are deflection, photographic distress, manual 

distress, drainage, friction, longitudinal profile, and 

transverse profile distortion (rutting). 

Deflection (MON_DEFL)—Deflection measurements 

from falling weight deflectometer (FWD) testing, 

pavement temperature gradient data measured during FWD testing, and computed parameters based 

on FWD measurements. The names of all tables in 

this submodule begin with “MON_DEFL.”

Distress (MON_DIS)—Distress survey data from 

both manual and film-based surveys that include the 

amount and severity of cracking, patching, and potholes and the existence of surface deformation, joint 

defects, and other types of pavement surface defects. 

Drainage (MON_DRAIN)—Information on the inspection of subsurface drainage features on selected 

SPS-1, -2, and -6 test sites. 

Friction (MON_FRICTION)—Friction measurements 

performed by participating highway agencies. 

Profile (MON_PROFILE)—Longitudinal profile data 

collected by automated inertial profiler or by manual 

Dipstick® measurements.

Rutting (MON_RUT)—Rutting data measured using 

a 1.2-m (4-ft) straightedge.

Transverse Profile (MON_T_PROF)—Transverse 

profile data and computed transverse profile distortion indices (rut depth) from manual Dipstick measurements or the optical Pavement Distress Analysis 

System (PADIAS) method. 

Seasonal Monitoring Program (SMP)—SMP-specific 

data, such as the onsite air temperature and precipitation data, subsurface temperature and moisture content data, and frost-related measurements. 

Specific Pavement Studies (SPS)—Construction and 

general information for SPS test sites. SPS test sites that 

were newly constructed for the LTPP program are part 

of the SPS-1, -2, -8, and -9 (Superpave®) experiments. 

SPS-3 (preventive maintenance of flexible pavements), 

-4 (preventive maintenance of rigid pavements), -5, -6, 

-7 (bonded Portland cement concrete (PCC) overlay of 

PCC pavements), and -9 consist mainly of existing pavements with experimental maintenance or rehabilitation treatments. SPS-9 contains both newly constructed 

and pre-existing pavements.

Traffic (TRF)—Traffic load, classification, and volume 

data. 

Test (TST)—Field and laboratory materials testing data 

from LTPP test sections. 

Detailed technical information on all tables contained in 

these LTPP database modules is available in the LTPP 

Information Management System User Guide.

15 Due to 

the changing nature of the LTPP database, this guide is 

updated for each data release and is also included in the 

SDR in the LTPP Reference Library. The IMS User 

Guide includes tutorials on common questions such as 

how to find linked materials data on SPS test sites. Prior 

to the release of SDR 28 in January 2014, the previous 

versions of this guide were referred to as the LTPP Information Management System, Pavement Performance 

Database User Reference Guide.16 The name of the guide 

was changed because information on AIMS and LTAS 

was added. 

Computed Parameters

A primary consideration in the design of the LTPP 

database was to disseminate data in their most disaggregated “raw” form; however, occasionally computed parameters have been added to the database for 

the data user’s convenience. Computed parameters 

are aggregations, computations, summarizations, or 

interpretations of raw data to derive new data ele-
146    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

ments. The LTPP program policy on incorporating 

computed parameters, which at one time were called 

“computed quantities,” was first established in 1996.17

In 2000, a new program policy changed the name to 

“computed parameters” and defined the roles of 

those involved with their creation.18

Some computed parameters are standard indices or 

data concepts with broad acceptance, such as soil classification following the methodology of the American 

Association of State Highway and Transportation Officials. Others are statistical representations of repeat 

measurements such as average and standard deviation. 

Still others are more complex derivations from multiple sources of raw data such as equivalent single-axle 

load, rut depth from transverse profile measurements, 

and backcalculated pavement layer moduli from FWD 

and pavement thickness measurements.

Most of the computed parameters contained in the 

LTPP database are internally computed. This means the 

parameters are computed by the database software as 

part of the normal processing and storage of raw data. 

Examples of internal LTPP computed parameter include:

•	 Roughness indices from longitudinal profile measurements.

– International Roughness Index.

– Slope variance.

– Root mean squared vertical acceleration at various wavelengths.

•	 Material properties from laboratory tests.

– Resilient modulus and creep compliance on hotmix asphalt (HMA) materials.

– Resilient modulus of unbound materials.

– Compressive strength of PCC materials.

•	 Distortion indices from multipoint transverse profile measurements.

– 1.8–m (6-ft) straightedge rut depths. 

– Lane-width wire reference rut depths.

– Positive, negative, and fill area distortion indices.

•	 Climate data.

– Freeze index.

– Number of freeze–thaw cycles.

– Virtual weather station climate estimates.

External computed parameters contained in the 

LTPP database are those where data were extracted 

from the database at some point in time, calculations 

performed external to the LTPP program, and the 

resulting computed parameters entered into the database. The primary operational issue with external 

computed parameters is updating or changing quality 

labels for the computed parameters when changes 

are made to the input data. External parameters 

included in the LTPP database are those where significant engineering expertise and computation 

resources are needed that are not available to many 

data users. In concept, provision of these complex 

computed parameters will promote many types of 

analysis efforts using LTPP data at lower cost to the 

sponsoring agency. Examples of the external computed parameters in the LTPP database include:

•	 Moisture contents of unbound materials from time

domain reflectometer (TDR) measurements on

SMP sites.

– Moisture estimates from automated TDR measurements using the traditional regression base 

dielectric constant approach.

– Moisture estimates from manual TDR measurements using a speculative dielectric constant interpretation approach coupled with traditional 

regression-based dielectric constant-moisture 

content approach.

– Moisture estimates from automated TDR measurements using the Transmission Line Equation 

approach coupled with a micro-mechanistic 

model to estimate moisture content.

•	 Subsurface frost penetration estimates on SMP sites.

•	 Backcalculated pavement layer moduli from FWD

measurements.

Computed parameters are aggregations, 

computations, summarizations, or 

interpretations of raw data to derive 

new data elements.
8: Storage, Growth, Seurity and Di

•	 Dynamic modulus–based |E*| estimates for HMA

materials using empirical- and mechanistic-based

models derived from generalized material classification and LTPP resilient-modulus test measurements inputs.

•	 Climate data computed from the National Aeronautics and Space Administration’s satellite-based 

Modern-Era Retrospective Analysis for Research and 

Applications, or MERRA, data.

Like the other tables in the LTPP database modules, 

detailed technical information on computed parameters is included in the IMS User Guide.19 

Ancillary Information Management System

The LTPP database was intended to disseminate as 

much raw data as possible, but some raw data containing information on the performance of test sections 

were not included in the database due to cost and other 

practical reasons. The objective of AIMS is to provide a 

central source of information and data that are not 

available in the pavement performance database, are 

frequently requested by LTPP data users, or provide a 

historical record of data reported on paper data forms. 

Table 8.2 lists the data contained in AIMS. 

AIMS data are stored in the LTPP IMS at FHWA’s 

highway research center. The data and images are 

Table 8.2. Contents of the Ancillary Information Management

Data Type Electronic Fil

Falling weight deflectometer data • Raw files containing deflection-time history measurements

• Raw files from reference and relative calibration tests

Longitudinal profile data • Raw data files with 25-mm interval elevations

• Profile measurements at weigh-in-motion sites

• Files created by the ProQual pre-processing software

Transverse profile data • Profile measurements

Pavement distress data • Digitally scanned, hand-drawn distress maps from manual distress surve

• Digital images from manual distress surve

• Digital distress maps generated from photographic film interpretati

• Digital images scanned from 35-mm black and white photographic fi

• Data summary forms from photographic film interpretati

Traffic data • Binary data files for select weigh-in-motion sites

• ASCII data files for select weigh-in-motion sites containing data to hundredth

of a second

• Site summary reports for ASCII data fil

• Volume, classification, and weight data in Traffic Monitoring Guide formats

Digitally scanned paper data • Invent

collection forms • SPS construction

• Seasonal Monitoring Program

• Rehabilitation

• Maintenance

• Material sampling and testing forms

• Traffic estimates

• Traffic data equipment validation and calibration visits

• Pavement gradient temperature measurement during FWD tes

• Friction measurements

• Faulting measurements

• Dipstick measuremen

• Test section status change forms

Digitized test section videos • Initial walking video inspections of test secti

• Walking video inspections performed during manual distress surve

• Through-the-windshield video during profiler measurements

• Drainage pipe inspectio
148    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

stored electronically using a defined directory structure and file-naming convention.20 Access to a large 

portion of these data is now available through the 

LTPP InfoPaveTM Web interface. 

In 2011, the Central Traffic Database became a component of AIMS, having been managed separately as a 

repository of agency-supplied data from the initiation 

of data collection. The database contains traffic data 

processed through LTPP software that was used to 

compute the annual estimates contained in the pavement performance database. Traffic data are reported 

in daily, hourly, and per-vehicle record formats for traffic volume, vehicle classification, and truck gross vehicle and axle weights. 

GROWTH IN

In a long-term research program, the number of data 

elements naturally increases over time as new observations are added. The following time-series graphs 

illustrate changes in some of the significant data elements that help to explain pavement performance. 

The time-series graphs illustrate the general trend 

in increase of data over time; however, some decreases 

also occurred due to data quality concerns, changes in 

data collection/measurement technology, and changes 

in data release policies. 

Another interesting point to note in the following 

graphs is the magnitude of LTPP data. The LTPP 

database now contains the most extensive source of 

detailed engineering data and information ever collected on the performance and properties of modern 

highway pavements. 

Falling Weight Deflectometer Data

The history of FWD data in the public data release 

can be traced back to the beginning of the program. 

The first release of FWD data occurred in July 1991. 

Figure 8.10 illustrates the growth in LTPP FWD data 

sets over time based on record counts in the deflection master table. One record exists in this table for 

each set of FWD measurements performed on a test 

section during a calendar day. The apparent decrease 

in the 1992 data release represents a change in LTPP 

QC processing, since only level-E data were released 

during this time period. The flat line from 2005 to 

2009 represents a reduction in FWD measurement 

frequency due to budgetary constraints. The increase 

in number of measurements after 2009 reflects the 

change in LTPP monitoring policy to renew FWD 

testing but at a lower intensity on fewer test sections.

To illustrate the large volume of data stored in the 

LTPP database, figure 8.11 shows the growth in the 

number of individual deflection measurement data 

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

9,000,000

8,500,000

8,000,000

7,500,000

7,000,000

6,500,000

1990	 1995	 2000	 2005	 2010 2000	 2005	 2010

Year Ye

Number of FWD Data Sets

Falling Weight Deflectometer Data Sets Over Time Falling Weight Deflectometer Deflection Measurements Over Time

Figure 8.10. Historical changes in the number of

data sets contained in LTPP data relea

Figure 8.11. Growth in number of FWD basin and 

transfer measurements contained in the LTPP data

since 2002.

Number of FWD Basin and Load Transfer

Measurements
8: Storage, Growth, Seurity and Di

since 2002. At each test point, the LTPP FWD data set 

contains the measured deflection basins of up to four 

drops from up to four drop heights. Analyzing the more 

than 9 million FWD deflection measurements accumulated through 2013 is a significant task. 

Longitudinal Profile Da

Measurement of the longitudinal profile of a test section 

is how the LTPP program computes pavement roughness parameters. Figure 8.12 shows the number of profile measurement data sets contained in the LTPP 

database. The LTPP measurement protocol requires 

five repeat profile measurements to be stored in the 

LTPP database for each measurement data set performed by high-speed road profilers, and one data set 

for manual measurements performed using the Dipstick® device. The amount of filtered profile elevation 

data stored in the database depends on the measurement device. A longitudinal profile measurement data 

set from a high-speed road profiler contains around 

2,000 data points using a 6-inch (152.4-mm) or 5.9-inch 

(150-mm) moving average filter. Dipstick measurements 

are recorded every 12 inches (304.8 mm), however, so 

only 1,000 data points are stored in the database for a 

test section that is 500 ft (152.4 m) long. 

Pavement Distress Dat

Three different types of pavement surface distress data 

are stored in the LTPP database: 

•	 PADIAS data are distress interpretations from 35-

mm photography using the initial interpretation 

hardware. 

•	 PADIAS 4.2 data are distress interpretations from

the 35-mm photography using updated hardware 

and methods. 

•	 Manual distress survey data are collected by LTPP

regional contractors who record their observations during a physical field inspection of a test 

section. 

Figure 8.13 shows the growth in number of pavement 

surface distress measurements contained in the LTPP 

database starting in 1992. The PADIAS 4.2 interpretation process for the 35-mm distress images was introduced in 1997. Over time, the images interpreted using 

the older PADIAS method were reinterpreted using 

the 4.2 method. The PADIAS method used a grid coordinate system for plotting and measuring surface distresses and the PADIAS 4.2 used a vector system. Data 

from the two methods were basically the same, and 

120,000

100,000

80,000

60,000

40,000

20,000

0

1990	 1995	 2000	 2005	 2010 1990	 1995	 2000	 2005	 2010

Year Ye

Longitudinal Measurements Over Time Pavement Distress Surveys Over Time

Number of Longitudinal Profile Measurements

Figure 8.12. Growth in number of longitudinal pave

profile measurements.

Figure 8.13. History of LTPP pavement surface 

surveys. Decline in PADIAS distress survey data is due 

replacement with PADIAS 4.2 reinterpretations of t

same images.

Number of Distress Surveys

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

Manual distress surveys

Padias42 distress surveys

Padias distress surveys
150    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

after a survey had been reinterpreted, the previous 

PADIAS data were removed from the database. Most of 

the PADIAS images that have not been reinterpreted 

are from test sections in the SPS-3 and -4 experiments 

for the period 1989 to 1992, due to funding limitations. 

Transverse Profile D

Transverse profile measurements are used to characterize different aspects of the pavement surface, such 

as rutting and pavement cross slope, on both AC- and 

PCC-surfaced pavements. As noted in chapter 6, two 

methods have been used by the LTPP program to 

measure transverse profile. Because the photographic 

method was not capable of measuring the cross slope, 

transverse profiles are stored normalized to the beginand endpoints in the database.21 However, since the 

Dipstick does measure the true elevation difference 

between begin- and endpoints, starting in 2004, this 

elevation difference was added to the database in the 

transverse profile cross-slope table. This is why in 

figure 8.14 there is a spike in cross-slope data starting 

in 2004. 

Climate Dat

The LTPP program performed direct climate measurements at test sections included in the SMP and at 

SPS-1, -2, and -8 experiments that were instrumented 

with automated weather stations (AWS). The LTPP 

program developed QC software and data edit programs to check this data and make adjustments for 

daylight saving time shifts. As discussed in chapter 7, 

data collection for the SMP began in August 1992 and 

was terminated in October 2004.22 LTPP AWS data 

collection began in August 1994 and was terminated 

in December 2008.23 The LTPP program attempted to 

provide as much data as possible, but the hourly data 

are not continuous over the collection period due to 

equipment malfunctions and breakdowns. Figure 8.15 

illustrates the massive amount of hourly climate data 

collected by the LTPP program. 

Materials Sampling and Test Da

Figure 8.16 shows the growth in the total number of 

records in the materials test data module starting in 

1996. The total number of records is a relative indica225,000

200,000

175,000

150,000

125,000

100,000

75,000

50,000

25,000

0

6,000,000

5,000,000

4,000,000

3,000,000

2,000,000

1,000,000

0

1995	 2000	 2005	 2010 1990	 1995	 2000	 2005	 2010

Date Da

Figure 8.14. Increase in transverse profile measurements since 1996. The collection of cross-slop

began in 2004. Cross-slope data allow for evaluation 

water retention, which has the potential to produce

hydroplaning at the pavement surface.

Figure 8.15. Growth in number of hourly climate 

measurements collected by the LTPP program as par

the Seasonal Monitoring Program and automated weath

station data collection efforts. Decreases in the timeseries represent the result of quality control checks to

remove suspect data.

Transverse Profile Data Sets

Padias42 distresssurveys

Padias distresssurveys

Total Hourly Climate Data

AWS

SMP

Number of Hourly Observations

Transverse Profile Measurements Over Time Hourly Climate Data Over Time
8: Storage, Growth, Seurity and Di

tor in the growth in materials data because during 

this time period changes were made to some of the 

internal data tables that did not result in the addition 

of more data. An example of this is a drop in the number of records in 2004 caused by removal of administrative tables TST_L06 and TST_L07, which were 

used to track materials samples and did not contain 

usable material test data. However, the increase in the 

total number of records in the materials testing module clearly shows the impact of the Materials Action 

Plan that was implemented to address missing materials data on SPS projects. 

The LTPP program invested significant resources in 

developing a research-quality test on the measurement 

of the resilient modulus of AC from field samples. 

(Development of the LTPP resilient modulus protocols 

is discussed in chapter 10.) Materials test data from the 

first LTPP P07 test protocol were removed from the 

database in 2000.24 Version 2 of the P07 protocol had 

been developed, which in addition to resilient modulus 

includes creep compliance and indirect tensile strength 

measurements. Figure 8.17 shows the growth in the 

amount of P07 version 2 data. 

DATA DISSEMIN

Dissemination of information is one of the stated 

objectives of the LTPP program. The program’s primary information distribution effort is the periodic 

macro release of “raw” data for use by scientist, engineers, and researchers for engineering-based analysis. 

The program also publishes and distributes research 

reports, data collection guidelines, and other documents related to pavement performance data collection and pavement research.

The LTPP program dissemination efforts comply 

with Federal information dissemination guidelines that 

were issued by the Office of Management and Budget on 

January 2, 2002, to implement the Data Quality Act, 

sometimes referred to as the “Information Quality Act” 

(title 5, section 515, Treasury and General Government 

Appropriations Act for Fiscal Year 2001).25,26 The purpose of the Federal guidelines is to ensure and maximize 

the quality, utility, objectivity, and integrity of information that is disseminated by Federal agencies. 

The U.S. Department of Transportation consequently established policy on information quality for 

the department’s agencies. This policy resulted in 

700,000

600,000

500,000

400,000

300,000

200,000

100,000

0

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

0

1995	 2000	 2005	 2010 1995	 2000	 2005	 2010

Date Da

Figure 8.16. Increase in total number of record

the materials test module starting in 1996. T

decrease in records in 2004 was due to removal of

two administrative tables from the test module and

not to a decrease in available measurement data.

Figure 8.17. Growth in materials data for resil

modulus (Mr), creep compliance, and indirect tensile

strength (IDT) using the P07 version 2 test protocol. Number of Data Sets and Test Resu

Number of Records in the Materials

Test and Sampling Module

Mr & Creep Data

N0. Test Data Sets & IDT Data

Materials Test Records Over Time Materials Data Sets for Mr, Creep, and IDT Data Over Time
152    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

FHWA developing its Information Quality Initiative 

(see sidebar).27 In 2008, the LTPP program issued a 

formal report on compliance with the Federal guidelines (Long-Term Pavement Performance Compliance 

With Department of Transportation Information Dissemination Quality Guidelines) that includes issues 

related to publications and disseminated summaries of 

data, micro data releases, source and accuracy statements, and pre-dissemination reviews.28

This section outlines LTPP data dissemination 

efforts through periodic releases of data, the development of software tools to aid data users, and, ultimately, 

online availability. As technology has changed, the program has adapted its methods to provide ease of access 

and improved functionality to users. 

Table 8.3. Nominal dates for major LTPP da

Release No. Date ZIP Size (GB)  Primary

1 January 1991 (data on 226 test sections) N/A N/A

2 July 1991 N/A N/A

3 January 1992 N/A N/A

4 July 1992 N/A N/A

5 January 1994 N/A N/A

6 September 1994 N/A N/A

7 February 1996 N/A N/A

8 September 1997 N/A N/A

9 January 1999 N/A N/A

10 October 1999 N/A N/A

11 January 2001 N/A N/A

12 January 2002 N/A N/A

13 March 2002 N/A N/A

14 July 2002 1.91 C

15 January 20031 2.15 C

16 July 2003 2.14 C

17 January 2004 2.24 C

18 July 2004 2.33 C

19 January 2005 2.57 C

20 October 2005 2.52  

21 January 2007 2.56  

22 January 2008 2.58  

23 January 2009 2.85  

24 October 20102 4.02  

25 January 2011 5.28  

26 January 2012 4.47  DVD and thumb dr

27 January 2013 4.67 Thumb drive

28 January 20143 (data on 2,509 test sections) 4.87 Thumb drive

1 The January 2003 data release was the first Standard Data Release—the first release in Microsoft® Access® format and the first to contain data at

all quality control levels.

2 The October 2010 data release increased in file size due to the addition of traffic tables, which were removed in the January 2012 data release.

3 The January 2014 data release is the first Standard Data Release available on the LTPP InfoPaveTM Web site. LTPP InfoPave contains the first pub

release of the LTPP AIMS data

In response to the Data Quality Act, FHWA established the Information Quality Initiative, which 

promoted the Federal guidelines for dissemination 

of data and other information to the public.
8: Storage, Growth, Seurity and Di

LTPP Data Release H

Table 8.3 provides the sequential release numbers 

assigned to the major LTPP database releases and 

their release dates. In the early years of the program, 

data releases contained partial data sets by module. 

For example, the first data release contained mostly 

inventory data from GPS test sections. In the mid1990s, partial database uploads by module, assigned 

fractional data release numbers, were common. These 

fractional data release numbers are not shown in 

table 8.3. 

The LTPP data release policy has also changed 

over the years. In the early years of the program, only 

data that passed all LTPP data quality checks were 

made available to the public, and a fee of $77 to $100 

was charged for each extraction to partially defray 

the cost of fulfilling the request. Participating highway agencies could obtain all of the data from test 

sections in their jurisdiction at no charge. In November 2002, the LTPP program changed the data release 

policy to provide access to all data regardless of the 

quality level and to provide data in the standard 

release format free of charge.29

While data users can still request custom extractions of data from the database in specific formats, 

these requests have been minimal since the introduction of the SDR in Microsoft Access format.

The following principles currently apply for release 

of LTPP data and information:

•	 LTPP data and information are distributed under

the sponsorship of the U.S. Department of Transportation in the interest of information exchange. 

The U.S. Government assumes no liability for its 

contents or use. 

•	 Understanding LTPP data collection procedures,

principles, and practices is the responsibility of data 

users who interpret and draw conclusions based on 

LTPP data and information. Data users can contact 

the LTPP Customer Support Service Center to inquire about availability of documentation not distributed with the data or contained on the LTPP 

Web site. 

•	 Although the LTPP program strives to provide data

and information at no cost to the data user, program 

funding limitations may limit the level of effort 

spent on user requests. 

•	 Extractions from the LTPP database are provided

free of charge to data users who request data in SDR 

formats.

•	 Custom extractions from the database may be

requested.

•	 Delivery of data in raw data collection formats,

access to internal documents, and access to other 

LTPP offline information are assessed on a caseby-case basis. 

LTPP Standard Data Release

The LTPP SDR is an extraction of all data from the central LTPP database, split up and formatted as a series of 

Microsoft Access databases (based on the North American software version). In addition to the data, the SDR 

includes updated software and documentation specific 

to the contents of the data release, together with the 

following significant elements:

•	 Microsoft Access databases in compressed format

that use long file names based on LTPP data module 

names.

•	 Data release notes that contain a historical record of

significant changes starting with data release 16 in 

July 2003. 

•	 Table Navigator software, which provides an intuitive point-and-click user interface to descriptions 

of all tables, all fields in each table, and the meaning of all code fields. The Table Navigator software 

is an automated metadata resource that all LTPP 

data users are encouraged to use to better navigate 

and understand the LTPP database. 

•	 Updated Database User Reference Guide.

•	 LTPP Reference Library, containing electronic copies of LTPP program documentation. 

Since the first SDR was issued in January 2003, the 

most up-to-date data from the LTPP program are distributed in this format on an annual basis free of charge 

to data requesters. Data at all quality levels, without 

restriction, are included in the release. 
154    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

LTPP Data Dissemination

As computer technology has evolved, the LTPP program 

has developed new and more efficient ways to make the 

data available to the pavement community. The program 

has engaged the State and Provincial agencies, industry, 

and academia partners in beta testing the software to 

ensure that users are able to access the pavement data 

provided in a format useful to them. The LTPP program 

continues to involve its partners and other users of the 

LTPP data in developing dissemination tools. 

LTPP Data Sampler and Data Request Program

The earliest software developed to aid users of LTPP 

data was the Data Sampler and Data Request Program, 

developed by the LTPP program. Before the program 

started distributing the data, this software allowed 

pavement engineers, researchers, and others to select 

and request the data using a standard data request 

form. The form was submitted to FHWA via the technical support services contractor, who would follow up 

with the data requestor to make sure the data being 

prepared to send to the requestor was appropriate for 

the requestor’s use. 

Made available to the public in Version 5 on 5.25-

inch floppy disk as early as January 1994, the sampler 

program helped users view and navigate the summary 

GPS data and request comprehensive data on selected 

sections. Version 7, released in early 1997, added features that allowed users to create their own data files 

using GPS data ordered from the LTPP program. It 

included a sample of the most up-to-date inventory, 

climate, traffic, layer material, and deflection data 

available for GPS sites.30, 31 

DataPave

DataPave was a CD-ROM–based product developed by 

the LTPP program to disseminate LTPP data in a userfriendly format. Its graphical user interface program 

was designed to help a data user select, view, and 

extract LTPP data of interest. Development of the 

DataPave program was based on the LTPP Data Sampler and Data Request Program. 

Three versions of DataPave were produced by the 

LTPP program. Version 1 and 1.1 were released in 1997, 

Version 2 in 1999, and Version 3 and 3.1 in 2001. Version 3, 

released in November 2001, was the first to include the 

new numbering system that reflected maintenance and 

rehabilitation activities performed at a section. Version 1 

required a single CD-ROM; versions 2 and 3 required two 

CD-ROMs. Due to data storage limitations, the DataPave 

CD-ROM did not contain all available LTPP data. After 

production of DataPave 3.1, creation of the CD-ROM version of the program was discontinued due to the development of DataPave Online in 2002 and the LTPP SDR. 

DataPave Online 

The LTPP DataPave Online program provided access 

to LTPP data through a user-interactive format. It was 

designed as a training tool for users of LTPP data who 

may not have been acquainted with the use of database 

technology. The online version of DataPave limited a 

user to simple queries and downloads of a relatively 

small amount of data at a time. Users desiring access to 

large amounts of data were encouraged to obtain a 

copy of the SDR.

LTPP InfoPaveTM

The newest data dissemination tool, LTPP InfoPave, 

was released in January 2014 (figure 8.18). LTPP 

InfoPave is an interactive Web portal to the world of 

LTPP data, providing on-demand, integrated access to 

LTPP products and the entire scope of the LTPP IMS—

the complete database, ancillary information in AIMS, 

and the LTPP Reference Library—through an interface 

that is easy and quick to use. LTPP InfoPave replaces 

DataPave and LTPP Products Online (discussed in chapter 10) and encompasses the SDR with the added option 

to obtain data releases for individual States/Provinces. 

The system’s software allows users to prepare customized searches, download data in Microsoft Access 

or Excel, generate customized reports, and personalize 

the LTPP InfoPave home page to their needs. The maps 

feature (figure 8.19) shows the LTPP tests sites throughout the United States and Canada and allows users to 

select data for one or multiple test sites. The contextual 

search feature connects the user to processed data, raw 

data, images, video, and reports. In addition, new features will include predefined, ready-to-use data sets 

that target specific analyses, prepared by expert data 

users; seamless activation of data analysis tools; and an 

interactive learning center to familiarize users with the 

system’s features and use of LTPP data. 
8: Storage, Growth, Seurity and Di

Highway agency staff and other pavement researchers participated in the design of LTPP InfoPave 

through focused Webinars that solicited data users’ 

opinions on the portal’s features and functionality. 

Refinement of the system with user input will continue 

during the coming years.

LTPP Customer Support Service

Since the LTPP program started disseminating data, 

customer support has been vital in helping users 

understand what data are available, in what formats 

the data can be provided, and how the data can be used 

to answer their pavement performance questions. The 

program’s customer support service function has 

changed over the years. After 1995, when responsibility 

for the database was transferred from TRB to FHWA, 

data distribution functions were transferred to the 

Figure 8.18. Home page of the LTPP InfoPaveTM W

technical support services contractor. In 1997, when 

the database operation, engineering specifications, 

computer programming, and management functions 

were merged into a single contract for central technical 

support of the program, the synergy of direct interactions among engineers, programmers, and data delivery staff led to rapid improvement in the quality of data 

delivery and user support functions.

It was not until 2002 that the LTPP customer support service function was formalized and assigned to 

the technical support services contractor. The purpose of the LTPP Customer Support Service Center is 

to provide a single point of responsibility for the program in responding to requests for data and technical 

questions from data users. The traditional customer 

support function was preparation of the SDR, support 

documentation, and user aids for release to the public. 
156    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

In 2006, due to program funding limitations, 

FHWA management moved the LTPP Customer Support Service Center to its highway research center, 

where it is operated under supervision from the program staff with support from an onsite contractor. 

The support center still operates as the single point of 

contact for LTPP data and information requests. As 

Figure 8.19. LTPP InfoPave’s interactive map feature, showing the locations of LTPP te

an onsite activity, the support center can provide 

reduced response times and access to other FHWA 

pavement resources. 

LTPP Lib

In addition to disseminating the pavement data, the 

LTPP program makes available a host of documents 
8: Storage, Growth, Seurity and Di

highway research center to provide a secure central 

location for the invaluable information collected since 

the program began in 1987. 

Since September 2011, LDEP, the central data entry 

Web portal leading to a production database, has been 

operated by LTPP’s technical support services contractor. LTPP’s regional support contractors are still responsible for collecting, processing, checking, and entering 

data. The data are now entered, however, through the 

centralized Web-enabled system and are uploaded on a 

continual basis instead of annually. This production 

database is used to update the central national archival 

IMS periodically at FHWA’s highway research center. 

Security measures continue at the offices of the regional 

support and technical support services contractors, and 

additional security procedures have been established at 

FHWA’s highway research center.

Safeguards for the LTPP Informa

Management System

In 2011, the LTPP program completed the transition to 

a new state-of-the art server that has adequate storage 

capacity for the entire IMS—the central production 

and AIMS databases and the LTPP library—and an 

electronic archive of the IMS. To secure the system, 

the following measures are currently enforced:

•	 Entry and exit to FHWA’s highway research center

are secured by locked gates and security guards who 

control access. 

•	 Physical access to the server room requires passage

through two locked doors.

•	 People who enter the server room must sign in and

sign out upon exiting.

LTPP compliance with the “Security of 

Federal Automated Information Resources” 

circular ensures that the data will be 

secure from unauthorized data modification, 

destruction, and loss. No significant loss 

has occurred to data entered into the 

LTPP IMS. 

that were created as part of the program that others 

can use or reference, such as data collection guidelines and reports from previous LTPP research projects. These documents are physically housed at 

FHWA’s highway research center. The vision for the 

LTPP document collection is to have at least one 

hard copy of all LTPP program documents and publications along with an electronic copy of each. The 

current LTPP electronic library is distributed as the 

Reference Library in the SDR package on DVD and is 

available at the LTPP InfoPave Web site. 

DATA SEC

Since the beginning of the LTPP program, data security has been a prime issue based on lessons learned 

from the American Association of State Highway Officials (AASHO) Road Test. Although some loss of 

LTPP data has occurred due to problems in field data 

equipment, LTPP data collection protocols contain 

instructions on data backup procedures to prevent 

data loss from faulty field data collection equipment. 

No significant loss has occurred to data entered into 

the LTPP IMS. 

As described earlier, prior to fall 2011, the LTPP 

program used a distributed data collection structure 

that culminated in a central production database. The 

distributed data collection structure was operated by 

the four regional support contractors, who collected, 

processed, checked, and entered data into their 

respective regional databases. The regional databases 

were uploaded annually into the central, secure LTPP 

production database operated by the technical support services contractor. Security was maintained by 

the LTPP technical support services contractor and at 

the respective LTPP regional support contractor 

offices. Many of the earlier security measures are 

documented in Long-Term Pavement Performance, 

Compliance with Department of Transportation Information Dissemination Quality Guidelines.32 These protections continue.

In 2008, the LTPP program began to centralize the 

program’s databases—pavement performance and central traffic databases—along with its AIMS data and 

other electronic and physical documents at FHWA’s 
158    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 The LTPP server hardware is housed in a covered

and locked rackmount system (see figure 8.9).

•	 The server is not connected to any external networks at the research center.

•	 Procedures are in place to minimize production

downtime in the event of hardware or software failure (“Data Processing Workstation Disaster Recovery (DR) and Continuity of Operations Plan 

(COOP),” internal document, December 14, 2012).

•	 Electronic backup media are stored offsite at a

secure location.

•	 The IMS is archived and sent to the National

Archives and Records Administration annually.

The Office of Management and Budget Circular A-130, 

Appendix III, “Security of Federal Automated Information Resources,”33 requires agencies to perform a 

review of the security controls within each system 

and formally approve the system’s operation. The 

LTPP program has completed the security process 

and is following the established guidelines. Compliance with these extensive standards means that LTPP 

data will be secure from unauthorized data modification, destruction, and loss. 

Hardware Security and Data Backup Procedur

Data backup procedures are in place at every level of 

the LTPP IMS. This section outlines the backup provisions for the program’s central server at FHWA’s highway research center.

The LTPP central server is currently a Dell PowerEdge 2900 server running Windows Server 2008, service pack 2. It has two 3.0 GHz Xeon E5450 dual core 

processors. It contains one 8-disk RAID 5 array with 

8 TB of storage. RAID 5 is able to recover from a single drive failure because parity information is striped 

across the disks. Therefore, if one, and only one, disk 

is corrupted, the system will continue to run. The 

drives are hot-swappable, so a faulty drive can be 

replaced, and it will be rebuilt automatically using the 

parity information stored on the other drives. The 

operating system, the Oracle software, and database 

instances are stored on this RAID 5 array. It also has 

two attached 15-disk RAID 5 arrays for a total of 

50 TB of additional storage.

The server is protected from power failures by an 

uninterruptible power supply, Smart UPS 2200, which 

was purchased with the server. The server is on a 

circuit that is powered by an emergency generator to 

support uninterrupted operation. 

The LTPP database system does not have critical 

uptime requirements; however, scheduled down time 

is minimized by doing the majority of the backup during nonbusiness hours. Daily backups are not deemed 

necessary due to the low volume of updates to the 

LTPP database. Major changes to software or the content of the database are received electronically and 

can be recreated in the case of system failure. Because 

recovery of every transaction to the point of failure is 

not necessary, all recovery is performed by restoring 

all the data files from a cold backup and restarting the 

database. The server is partitioned to contain different segments of the IMS, and the backup procedures 

for the segments vary according to the level of activity 

they experience, as outlined in table 8.4. 

Table 8.4. Backup frequency for the LTPP Information Management Sys

Server Segment  Update Cycle Full Backup Incremental Ba

Operating system  Daily Biweekly Alternate da

Working storage; workstation backup  Daily Biweekly Alternate d

Ancillary Information Management System Quarterly Quarterly Not applicabl

Traffic  Daily Biweekly Alternate da

Standard Data Release database Quarterly Biweekly Not applicabl

Production database  Daily Biweekly Alternate da

Test database  Daily Biweekly Alternate da

Recovery Not applicable Quarterly Not applicable

Archive of historical data/software Quarterly Quarterly Not applicable
8: Storage, Growth, Seurity and Di

SUMMA

The LTPP database came into being in 1989 and has 

been successfully adapted to the many changes in 

computer hardware and software technology over the 

years. The database represents a significant investment of resources. The quality management features 

of the LTPP database, implemented before the development of formal quality management standards and 

mandated Federal quality and security guidelines, have 

resulted in a well-documented and robust national 

data archive of pavement research data. The database 

security procedures implemented by the LTPP program assure the preservation of all LTPP data; there 

will be no loss of data as occurred with the AASHO 

Road Test data, where many of the data were lost 

because they were not converted as technology 

changed over the years.34

The LTPP program has amassed the largest and 

most comprehensive engineering data set on the performance of modern pavements in the world. The 

LTPP database spans the pavement engineering spectrum from time-series distress and roughness measurements to detailed measurements of changes in 

pavement materials due to climate and response of 

pavement materials under loading. LTPP InfoPave, 

launched in 2014, is a great leap forward in providing 

continuous access to the database, AIMS, pavement 

research, software, and other LTPP products.

Today, the LTPP database can be described as a 

complex, rich, research data warehouse that, to be 

used efficiently, requires some knowledge of the program. The LTPP program can claim successful accomplishment of the sixth major objective for the program 

listed in the 1986 research plan:35 A national long-term 

pavement performance database has been established 

and is improving continually. Maintaining data quality 

is an important function of the program that is discussed in the next chapter.

REFERE

1. TRB Pavement Performance Committee. Preserving 

and Maximizing the Utility of the Pavement Performance 

Database. Transportation Research Board, Washington, 

DC, 2009. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_report_2009.pdf. 

2. J. T. Maddock. “Accessing the Database: Policies and 

Procedures, Strategic Highway Research Program.” 

Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991, 

p. 213. http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-91-514.pdf. 

3. LAW PCS. Introduction to LTPP Data. Federal Highway 

Administration, McLean, VA, April 1999, p. 2. http://

www.fhwa.dot.gov/publications/research/ 

infrastructure/pavements/ltpp/resguide/resguide.pdf. 

4. W. O. Hadley. SHRP-LTPP Overview: Five-Year Report 

(SHRP-P-416). Strategic Highway Research Program, 

National Research Council, Washington, DC, 1994, 

pp. 160–164, 170. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-416.pdf. 

5. Directive I-56, “LTPP IMS Standards and Conventions,” July 1, 1998. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_050-099/I-56.pdf. 

6. Directive I-102, “LTPP Data Release Policy,” Nov. 19, 

2002. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/IMS_100-149/I-102.

pdf. 

7. Directive I-157, “Full Implementation of LTPP Data 

Entry Portal,” Dec. 19, 2011. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_150-199/I-157.pdf. 

8. Directive I-157, “Full Implementation of LTPP Data 

Entry Portal,” Dec. 19, 2011. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_150-199/I-157.pdf. 

9. Directive I-155, “Software Performance Reports,” 

Dec. 19, 2011. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_150-199/I-155.pdf. 
160    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

10. Directive TDP-54, “Release of LTPP Traffic Analysis 

Software Version 2.0,” Aug. 10, 2011. Federal Highway 

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/TDP_50-99/TDP-54.pdf. 

11. Directive GO-53, “AIMS Data Entry Portal (ADEP) 

Open,” June 7, 2012. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

GO_50-99/GO-53.pdf. 

12. “LTPP Database Server Relocation.” LTPP Newsletter, 

vol. 4, no. 3, Summer 2008, p. 2. http://www.fhwa.dot.

gov/publications/ltppnews/08072.pdf. 

13. “The Place to Go for LTPP Data and Information.” 

Focus, November 2008 (FHWA-HRT-09-008). http://

www.fhwa.dot.gov/publications/focus/08nov/06.cfm. 

14. J. T. Maddock. “Accessing the Database: Policies and 

Procedures, Strategic Highway Research Program,” 

Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991. 

http://onlinepubs.trb.org/onlinepubs/shrp/SHRP-91-

514.pdf. 

15. G. Elkins, T. Thompson, B. Ostrom, A. Simpson, and B. 

Visintine. Long-Term Pavement Performance, Information Management System, User Guide (FHWA-RD03-088, updated). Federal Highway Administration, 

McLean, VA, September 2013. http://www.ltpp.org/

IMSUserGuide2013.pdf. 

16. G. Elkins, P. Schmalzer, T. Thompson, and A. Simpson. 

Long-Term Pavement Performance Information 

Management System, Pavement Performance Database 

User Reference Guide (FHWA-RD-03-088). Federal 

Highway Administration, McLean, VA, November 2003; 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/reports/03088/

03088.pdf. 

17. Directive GOD-3, “Policy on Incorporating Computed 

Quantities in the LTPP IMS,” Dec. 16, 1996. Federal 

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/GO_01-49/GO-03.pdf. 

18. Directive GO-25, “Procedures for Adding Computed 

Parameters to the LTPP IMS,” May 2, 2000. Federal 

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/GO_01-49/GO-25.pdf. 

19. G. Elkins, T. Thompson, B. Ostrom, A. Simpson, and B. 

Visintine. Long-Term Pavement Performance, Information Management System, User Guide (FHWA-RD03-088, updated). Federal Highway Administration, 

McLean, VA, September 2013. http://www.ltpp.org/

IMSUserGuide2013.pdf. 

20. G. Elkins, T. Thompson, B. Ostrom, A. Simpson, and B. 

Visintine. Long-Term Pavement Performance, Information Management System, User Guide (FHWA-RD03-088, updated). Federal Highway Administration, 

McLean, VA, September 2013, pp. 237–250. http://

www.ltpp.org/IMSUserGuide2013.pdf. 

21. G. Elkins, P. Schmalzer, T. Thompson, and A. Simpson. 

Long-Term Pavement Performance Information 

Management System, Pavement Performance Database 

User Reference Guide (FHWA-RD-03-088). Federal 

Highway Administration, McLean, VA, November 2003; 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/reports/03088/

03088.pdf.

22. Directive GO-36, “Termination of LTPP Seasonal 

Monitoring Program,” Oct. 27, 2004. Federal Highway 

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/GO_01-49/GO-36.pdf. 

23. Directive AWS-21, “Operation, Maintenance & 

Calibration of Automated Weather Stations, and 

Termination of Data Collection,” Feb. 19, 2008, Federal 

Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/AWS/AWS-21.pdf. 

24. Directive I-83, “Removal of SHRP P07 Data from IMS,” 

Dec. 21, 2000. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_050-099/I-83.pdf. 

25. Office of Management and Budget, Executive Office of 

the President. Guidelines for Ensuring and Maximizing 

the Quality, Objectivitiy, Utility, and Integrity of 

Information Disseminated by Federal Agencies 

(Final Guidelines), Jan. 3, 2002. http://www.

whitehouse.gov/omb/fedreg_reproducible. 

26. U.S. Statutes at Large 114 (2000): 2763A-153. Treasury 

and General Government Appropriations Act for Fiscal 

Year 2001. http://www.gpo.gov/fdsys/pkg/PLAW106publ554/pdf/PLAW-106publ554.pdf. 

27. Secretary of Transportation. Secretary’s Policy 

Statement on Information Quality. August 2002. 

http://www.dot.gov/sites/dot.gov/files/docs/

DOT%20Information%20Dissemination%

20Quality%20Guidelines.pdf. 

28. G. Elkins. Long-Term Pavement Performance, Compliance with Department of Transportation Information 

Dissemination Quality Guidelines (FHWA-HRT08-065). Federal Highway Administration, McLean, 

VA. November 2008. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/08065/08065.pdf. 
8: Storage, Growth, Seurity and Di

29. Directive I-102, “LTPP Data Release Policy,” Nov. 19, 

2002. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/IMS_100-149/I-102.

pdf. 

30. “LTPP Program Offers Data Sampler on Disk.” Focus, 

April 1995, p. 4. Available from LTPP Customer Support 

Service Center (ltppinfo@dot.gov).

31. “New Software Makes LTPP Data More Accessible.” 

Focus, April 1997 (FHWA-SA-97-022). http://www.

fhwa.dot.gov/publications/focus/97apr/47ltpp.cfm. 

32. G. Elkins. Long-Term Pavement Performance, 

Compliance with Department of Transportation 

Information Dissemination Quality Guidelines 

(FHWA-HRT-08-065). Federal Highway Administration, McLean, VA, November 2008. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/08065/08065.pdf. 

33. Office of Management and Budget Circular A-130, 

Appendix III, Security of Federal Automated Information Resources. Dec. 30, 1985. http://www.whitehouse.

gov/omb/circulars_a130_a130appendix_iii. 

34. L. Mason. “Smithsonian to Archive Road Data.” 

TR News, No. 232, May–June 2004, p. 24. http://

onlinepubs.trb.org/onlinepubs/trnews/trnews232.pdf. 

35. Strategic Highway Research Program, Research Plans, 

Final Report. National Cooperative Highway Research 

Program Project 20-20, Transportation Research 

Board, Washington, DC, May 1986.
162    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

LTPP data requirements are based on achievement of the program’s goal 

and objectives and, as a result, include literally thousands 

of measurement concepts.

© American Concrete Pavement Association, www.acpa.org
9: LTPP Data Quality Effo

LTPP Data Quality Efforts

9

Introduc

Since the program’s start, data quality has been a prime 

concern in the development and operation of LTPP 

activities. High-quality data have been critical to the 

program’s success. Given the program’s data requirements—a large number of data elements of varying 

complexity—as well as the available data acquisition 

and source options, achieving high-quality data is not 

only a major challenge, but also one that requires significant resources.

LTPP data requirements are based on achievement 

of the program’s goal and objectives and, as a result, 

include literally thousands of measurement concepts. 

During the program planning process, experts in each 

associated engineering discipline participated in 

developing the data requirements, which were then 

reviewed and critiqued by other stakeholders. Like 

The many quality control/quality assurance processes described in this chapter keep the focus of the people 

involved in the LTPP program on the quality of the work they do. Achieving a high level of data quality is a 

program expectation. This expectation created the environment that enabled development of cutting-edge 

quality control processes more than 10 years in advance of accepted industry standards and will enable 

continued improvements in quality control processes. 

the data requirements, the methods used to acquire 

LTPP data were developed by expert staff working 

in concert with program stakeholders and other 

authorities. A comprehensive planning process was 

used to examine and evaluate data acquisition methods that took into account budget, complexity, and 

time considerations. 

Due to the complexity of many LTPP data elements, 

an early program decision was made to select qualified 

regional support contractors who had experience in 

operating technical data collection equipment and 

working with highway agencies to collect data. 

Increased planning was needed for data collection that 

requires special equipment, such as the falling weight 

deflectometers (FWDs) used in nondestructive deflection testing and the profilers used to collect profile 
164  THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Key Milestones in Data Quality

Efforts

1987 First Distress Identification Manual 

released

1989 SHRP-LTPP Customer Suppo

Services established

1991 SHRP-LTPP reference calibratio

procedure for FWDs developed

1992 First Distress Accreditation 

Workshop held in Reno, Nevada

1992 ProQual developed 

1993 Original LTPP Materials Testing and 

Handling Guide published

1993 Original Traffic Software used to

process traffic data

1994 Software Problem Report for

formally adopted

1995 Operational Problem Report 

formally implemented

1997 Comparisons with distress maps 

from prior manual surveys required

1998 FHWA regional operations audits 

formalized

1998 Data Analysis/Operations Feedback 

Reports process started

2002 LTPP Traffic Analysis Software

(LTAS) first used by regional

support contractors 

2006 LTPP Materials Testing and Handling 

Guide revised

2012 Traffic Data Collection and 

Processing Guide (v. 3) issued

data. These early program planning efforts to establish 

data requirements, acquisition methods, and sources 

provided a solid foundation for achieving high-quality 

data, but they were just the beginning of the LTPP 

quality initiatives. 

Data quality control/quality assurance (QC/QA) 

processes have been developed, updated, and implemented throughout the LTPP program. The processes 

fall into several categories:

• QC processes before data collection.

• QC processes during data collection.

• QC processes after data collection.

• Database checks and reviews.

• Regional quality management plans and Federal

Highway Administration (FHWA) QA audits.

• Higher order data checks.

• Peer review.

• Feedback processes.

These processes are detailed over the remainder of 

this chapter. In addition, products that emerged from 

LTPP QC/QA development and implementation 

efforts are summarized in chapter 10. The various 

documents referenced in this chapter—directives, 

guidelines, manuals, and studies—are available at 

LTPP’s InfoPaveTM Web site.

QUALITY CONTROL PROC

DATA COLL

After the selection of data collection equipment and 

regional support contractors, before data collection 

began, three elements were identified as critical 

to providing a solid foundation for high-quality 

LTPP data. These elements are data collection 

standards, personnel requirements, and equipment 

requirements. 

Data Collection Standar

To promote uniform, consistent, and high-quality data, 

the LTPP program has published formal standards in 

the form of data collection guidelines, guides, and 

manuals that specify data collection frequencies, types 

© Joseph Sohm/Shutterstock.com
9: LTPP Data Quality Eff

of data collection, standard definitions, measurement 

procedures, test protocols, operation of electronic data 

collection devices, and data collection forms. These 

standards are implemented through the issuance of 

LTPP program directives, which present program policy to be followed by regional support contractors, 

materials laboratory contractors, and participating 

highway agencies. When guidelines are revised and 

updated, program directives are used to document 

changes in processes, procedures, equipment, and data 

collection activities.

A team process has been used to develop data collection guidelines. The process starts with the development of a draft guide by the central technical team. 

LTPP managers solicit review and comment from 

stakeholders—related expert task groups (ETGs), 

highway agencies, regional support contractors—on 

an initial draft. Feedback from the combined team 

obtained through written comments, teleconferences, Webinars, regional meetings, and national meetings is used to craft a proposed final version. The 

proposed guidelines are tested and refined through 

pilot activities and, when final, are issued through a 

formal LTPP program directive. Following implementation, data collection personnel can report 

equipment problems, issues with data collection 

forms, needed changes to procedures, and other 

issues using the formal Operational Problem Report

(OPR) process. Changes and updates to the guidelines are also issued in a program directive. 

Some of the data collection guidelines have been compiled and published as manuals containing standards specific to the LTPP program. 

Examples include the highly requested Distress Identification Manual for 

the Long-Term Pavement Performance 

Program,

1

 the Long-Term Pavement 

Performance Manual for Profile Measurements and Processing,

2,3 and the 

Long-Term Pavement Performance 

Manual for Falling Weight Deflectometer Measurements4 (figure 9.1). These 

publications, like most of the many 

other LTPP guides, manuals, and guidelines (some of 

which date back to 1988), have undergone major revisions and updates over the years. A list of the major 

LTPP data collection guidelines is presented in table 9.1.

In addition to providing standard definitions, 

measurement procedures, and data collection forms, 

guidelines also typically address equipment issues 

and, in the case of electronically collected data, software and data processing issues. For example, the 

latest version of the LTPP Manual for Falling Weight 

Deflectometer Measurements covers all aspects of 

measurement, from equipment setup through data 

handling procedures. Similarly, the LTPP Manual 

for Profile Measurements and Processing includes 

everything from equipment maintenance to interregional comparison tests and processing profile data 

in the office. 

Data collection guidelines typically include and 

require the completion of data collection forms, 

whether data are collected using electronic means 

(which have comprised the bulk of LTPP data) or 

manual methods. These forms include written 

instructions on all requested pieces of information 

and pertinent information needed to complete the 

form. Also, all forms are numbered and dated for 

document control, and revisions to forms are issued 

by formal directives that document the changes. Most 

of the data collection guidelines within the LTPP 

program are implemented through formal issuance 

of directives.

FIgurE 9.1. Data collection guidelines published as manuals for profile 

measurements and processing, distress identification, and falling 

weight deflectometer measurements.
166  THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Table 9.1. LTPP data collection guidel

Date*

Distress Identification Manual for the Long-Term Pavement Performance Studies 198

SHRP-LTPP Data Collection Guide 198

SHRP-LTPP Interim Guide for Laboratory Materials Handling and Testing 19

Framework for Traffic Data Collection for the General Pavement Studies’ Test Sections 19

SHRP-LTPP Guide for Field Materials Sampling, Handling and Testing 19

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-5: 1

Rehabilitation of Asphalt Concrete Pavements

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-6: 1

Rehabilitation of Jointed Portland Cement Concrete Pavements

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-7: 1

Bonded Portland Cement Concrete Overlays

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-1: 1

Strategic Study of Structural Factors for Flexible Paveme

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-2: 1

Strategic Study of Structural Factors for Rigid Paveme

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-8: 1

Study of Environmental Effects in the Absence of Heavy Load

Manual for Profile Measurement: Operational Field Guidelines 1994

LTPP Seasonal Monitoring Program: Instrumentation Installation and Data Collection Guidelines 1

SPS-2 Seasonal and Load Response Instrumentation, North Carolina DOT 

Data Collection Guidelines Under Less Than Ideal Conditions (Seasonal Monitoring Program) 1

Specific Pavement Studies Data Collection Guidelines for Experiment SPS-9A: Superpave® Asphalt Binder Stud

Guidelines for IMS Data Entry for SPS-9 Project 

SPS-1, SPS-2 and SPS-8 Data Collection Guidelines for Experiment

Guide to LTPP Traffic Data Collection and Processing 2001

LTPP Inventory Data Collection Guide 200

Long-Term Pavement Performance Maintenance and Rehabilitation Data Collection Guide 2006

Guidelines for the Collection of Long-Term Pavement Performance Data 2006

Long-Term Pavement Performance Program Manual for Falling Weight Deflectometer Measurements 2006

Long-Term Pavement Performance Program Falling Weight Deflectometer Maintenance Manual 2006

Long-Term Pavement Performance Project Laboratory Materials Testing and Handling Guide 2007

LTPP Field Operations Guide for SPS WIM Sites (Version 1.0) 

LTPP Traffic Data Collection and Processing Guide (Version 1.3) 2012

Long-Term Pavement Performance Program Manual for Profile Measurements and Processing 2013

LTPP Information Management System (IMS) Quality Control Checks (updated annually) 

Distress Identification Manual for the Long-Term Pavement Performance Program 201

* Year published. Earliest and most recent versions released are listed. Intermediate versions have been publish
9: LTPP Data Quality Effo

Personnel Requiremen

Well-trained and knowledgeable data collection personnel are another critical element to achieving high-quality 

data. Accordingly, the data collection contractor selection 

process has included consideration of experience in 

operating various types of pavement data collection 

equipment, conducting field pavement data collection 

activities, or performing laboratory material tests, 

depending on the subject of the data collection contract. 

In addition, the LTPP program has established minimum 

criteria for data collection personnel, including previous 

experience in data collection, formal training with the 

data collection procedures using a training plan and syllabus approved by the LTPP program staff, and time 

spent assisting experienced personnel in performing data 

collection before doing so independently. Implementation of personnel requirements within the LTPP program 

is accomplished contractually with the data collection 

contractors or through formal program directives.5,6

In the case of pavement distress data, for example, an 

accreditation program was established in 1992, requiring that all pavement distress data be collected by 

accredited raters. The regional support contractor staff 

are required to attend the distress accreditation workshops held by the LTPP program to receive and maintain their accreditation. To be eligible to attend, raters 

first have to be trained to a high level of competence in 

the knowledge and procedures contained in the Distress Identification Manual using a combination of 

classroom and field training activities. The regional 

support contractors are required to provide formal 

training based on the FHWA National Highway Institute’s “Pavement Distress Identification Workshop” 

course. In addition, new raters are required to assist 

experienced personnel in performing distress data collection for asphalt and jointed concrete pavement (a 

minimum of two sections each) before becoming eligible to attend an accreditation workshop.7

The first distress accreditation workshops were held 

in 1992 in Reno, Nevada,8 and workshops were held at 

least annually early in the LTPP program. More recently, the workshops have been held less frequently due to 

budget limitations. The accreditation process consists 

of two major parts: a written examination to test the 

general knowledge of the rater and a field data collection or film interpretation examination to measure the 

rater’s capabilities in observing and recording distress 

data. Grading and accreditation are accomplished by 

comparing the rater’s results to the reference values 

established by a team of experienced raters.

The distress accreditation workshops are intended 

for trained, experienced personnel only; they are not 

intended to train personnel. Their primary purpose is to 

assure high quality and uniformity in identifying pavement distress. Furthermore, to maintain their accreditation, distress raters have to meet minimum recertification 

requirements, including performing at least 15 surveys in 

a 12-month period—ideally evenly distributed throughout that time period—and successfully completing the 

accreditation workshop annually, or as required by the 

LTPP program. Figure 9.2 shows a distress accreditation 

workshop held in Columbus, Ohio, in May 2010.

Training sessions focused on the handling of 

weather and seasonal data were conducted as well. 

Personnel learned how to review the weather plots 

and identify and edit erroneous data collected from 

the automated weather stations, and they were trained 

in data processing QC procedures for the Seasonal 

Monitoring Program.

To promote consistency in data collection across the 

test sites, national and regional meetings of regional 

support contractor staff as well as teleconferences 

involving data collection personnel are conducted on 

each major data collection topic. These interactions, 

which vary in frequency according to the need and the 

maturity of each data collection activity, allow for the 

exchange of ideas and improvements as well as the discussion and resolution of issues.

Figure 9.2. Distress raters evalu

a pavement surface in an LTPP

accreditation workshop, where raters’

proficiency is tested.
168    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

survey, dynamic load response, seasonal monitoring, 

and traffic data collection equipment. 

LTPP data collection activities rely on equipment 

that is often of a fairly sophisticated nature, which has 

been built using technologically advanced components 

to meet the program’s specifications (table 9.2). The 

basic inertial profiler components, for example, include 

laser sensors, accelerometers, data collection triggers, 

a distance-measuring instrument, and a computer system that combines the measurements from each of the 

components to provide the longitudinal profile data. 

In 2013, texture measurements, surface temperature, 

GPSr (Global Positioning System receiver), and photo 

and video capabilities, were added. 

Because properly functioning equipment is critical 

to achieving high-quality data, the maintenance, repair, 

checks, and calibration of equipment used in data 

collection have been an integral part of LTPP QC/QA 

efforts since the program’s beginning. Most data collection guidelines address equipment maintenance, 

repair, checks, and calibration procedures, and each 

regional support contractor is required to establish and 

follow an equipment preventive maintenance plan that 

is accepted and monitored by LTPP program staff. 

Throughout the course of the program, many direcIn addition, the regional support contractors’ QC 

plans, mandated by the LTPP program, include processes for training new staff and reviewing the performance of existing staff, including some exchanges of 

equipment operators between the regions to review 

each other’s efforts. The training requirements within 

these QC plans address not just the distress data collection, but all collection activities such as FWD, profile, 

and the Seasonal Monitoring Program. (Regional contractors’ QC plans are addressed later in this chapter, 

along with FHWA QA audits.)

Equipment Requiremen

In developing the LTPP data collection plans, it was 

determined that the program should own and operate specialized data collection equipment to best 

achieve the program’s objectives. However, some 

data collection services were engaged due to consideration of the equipment cost, advanced operating 

requirements, or volume of data measurements to be 

performed. Contracted services have been used to 

collect photographic distress data, perform laboratory materials tests, and take ground penetrating 

radar measurements. The LTPP program has 

acquired FWD, inertial profiling, manual distress 

Table 9.2. LTPP data collection equipment and compon

Georgia faultmeter

Rod and level

Seasonal Monitoring Program Mobile Unit (CR10 data logger, Tektronix time domain reflectometer cable tester

electrical resistivity function generator, and digital multimeters) 

Megadac (dynamic load strain sensors, stress sensors, and displacement sensors) 

Profilometers (laser sensors, accelerometers, data collection triggers, distance-measuring instrument, surface temperature 

sensors, macrotexture measuring lasers) 

Dipstick® profile measuring devices

Falling weight deflectometers (air and surface temperature sensors, load plates, load cells, deflection sensors, 

high-accuracy distance-measuring instrument)

Climate and subsurface monitoring equipment (temperature sensors, rain gauges, subsurface temperature probes, 

moisture probes, frost/thaw probes, piezometers)

Traffic monitoring equipment (piezo electric sensors, inductive loops, pneumatic tubes, radar or infrared beams)

Materials testing equipment (closed-loop servo hydraulic test system—load frame, load cells, hydraulic system, deformation 

devices, triaxial pressure chamber, temperature chambers, computer, dynamic cone penetrometer)

Weigh-in-motion equipment (bending plate, load cell, and quartz sensor)
9: LTPP Data Quality Effo

tives have been issued that address specific maintenance checks and calibration procedures for LTPP 

data collection equipment.

Calibrations and checks are performed on all data 

collection equipment to insure proper functioning 

before they are used in the field or laboratory. In those 

cases where it is not possible to calibrate a device, 

equipment checks are used. For example, temperature 

sensors (thermistor probes) in the Seasonal Monitoring Program were placed in substances of known temperature such as ice and boiling water. If the sensors 

were found to be outside an established range, they 

were either returned to the manufacturer for adjustment or replacement.

Although the LTPP program uses existing technology to the extent that is practical, in some cases it has 

had to develop calibration and check procedures for 

program equipment. For instance:

Daily Check

For inertial profilers, it is imperative that the individual components as well as the overall system 

be calibrated, where possible, to National Institute of Standards and Technology standards. In 

those cases where it is not possible to directly 

calibrate a component, checks are carried out to 

insure proper function. For example, these checks 

on the LTPP inertial profiler components are 

performed each day before data collection:

• Laser sensor checks, using a series of calibrated blocks of different heights to ensure 

that they are accurately measuring height.

• Tire examinations and pressure checks (the 

distance-measuring instrument is affected by 

the tire’s rolling radius).

• Static/bounce tests to verify that the accelerometers and laser sensors are functioning 

together properly.

• Texture and pavement surface temperature 

sensor checks (a requirement with the newest 

LTPP profilers). 

•	 The program developed the first reference calibration procedure for FWDs in the United States. This 

development process was independent of the equipment supply contractor, and Federal, State, and international highway agencies subsequently adopted 

the LTPP FWD reference calibration procedure.9,10,11

•	 The program developed cutting-edge laboratory

equipment calibration methods for highly sensitive tests for elastic response of pavement 

materials in 1997,12 which were later expanded and 

modified in a 2005 publication.13 These tests, informally called startup procedures, involved expert 

instrumentation engineers who checked the internal functions of advanced laboratory electronic 

measurement equipment to identify sources of 

bias and error that could not be reliably detected 

through inspection of the output data. These 

checks measured the output from a controlled 

electrical input into the system to discern if the instrumentation was correctly calibrated to the manufacturer’s specifications.

A number of software programs have also been developed and implemented to help identify potential equipment problems and to check calibrations. Examples 

include:

•	 FWDCAL—This program automates analysis of 

the relative calibration test procedure results for 

the FWD geophones and includes these functions: 

check FWD relative calibration data file for compliance with LTPP test setup requirements, calculate new relative gain factors for each geophone, 

check the ratios between existing and new relative 

gain factors to determine if they are within established tolerances, perform an analysis of variance 

on the data to determine the statistical significance 

of key test factors, provide a statistical summary of 

the test results, provide guidance to the user on 

needed gain changes or further testing needs, compute the gain factor for a replacement sensor, process up to three data sets in the same file, and compute an average new relative gain factor from 

relative calibration tests performed as a part of the 

LTPP reference calibration procedures.
170    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 MOBILE—This program was used in the Seasonal 

Monitoring Program to perform measurements on 

the time-domain reflectivity calibration reference 

cable installed in a user-specified port and was intended to be an aid in diagnosing problems with the 

time-domain reflectivity data collection system 

whenever an anomaly was encountered.

Another important concept, introduced by the 

LTPP program in the early 1990s, was the use of equipment comparisons, which are referred to as “FWD 

thump-offs” and “profiler rodeos.” Such comparisons 

were used not only as a means of accepting equipment 

for program use, but also for performing periodic evaluations of the equipment’s operational status and for 

cross-training exercises. For example, upon delivery of 

the profilers now in use, a stringent acceptance procedure was conducted in February 2013 on reference test 

sections in College Station, Texas, and a week-long 

training was held in April 2013.14

In the profiler rodeos, the LTPP profilers were compared against each other as well as against a reference 

device, the Face Dipstick and rod and level, to ensure 

that the equipment was collecting high-quality profile 

data (as described in chapter 6). These rodeos required 

the establishment of multiple test sections. The profile 

of each test section was then measured by the Face 

Dipstick and profilers, and the resulting data were analyzed to determine compliance with established elevation bias and precision criteria along with the 

International Roughness Index (IRI) values.15 Figure 

9.3 shows four profilers prepared for testing at a 2007 

rodeo in Minnesota. 

Ultimately, it is the responsibility of the regional support contractors to maintain the data collection equipment they use in good-working, calibrated condition. 

This equipment has included devices such as the levels 

used for surface elevation surveys and pavement and air 

temperature probes used in conjunction with FWD testing and profile surveys. Furthermore, as noted earlier, 

each regional support contractor is required to establish 

and follow an equipment preventive maintenance plan 

as accepted and monitored by LTPP program staff.

QUALITY CONTROL

DURING DATA

While the data collection guidelines, personnel requirements, and equipment requirements described in the 

previous section provide an excellent foundation, additional QC elements are needed to assure that data are of 

high quality. Key elements to be considered during data 

collection are the ambient conditions, monitoring of 

data collection activities in the field by responsible personnel, and the use of QC tools to check equipment and 

data in the field. 

Ambient Conditio

Ambient conditions must not be neglected when planning for or performing data collection because they 

can significantly affect data quality, as shown in these 

LTPP-specific examples: 

•	 Hot-mix asphalt pavements in some southern States

can show less cracking during the hot summer months

Figure 9.3. Profiler rodeo held at the Minnesota Road Research Project (MnROAD

Albertville. From May 14 to 18, 2007, researchers performed a comparison test of the profilers used

by the four LTPP regional support contractors.
9: LTPP Data Quality Effo

than in the winter. Likewise, temperature affects the 

distresses visible in Portland cement concrete pavement, including crack and joint openings. Thus the 

temperature of a pavement at the time distress measurements are performed is important to identify 

potential discrepancies in time-series trends.

•	 Inertial profiler laser height sensors can malfunction at very high and very low temperatures. At 

approximately 0 °C and 50 °C (32 °F and 122 °F), 

some lasers begin to produce errors, and at approximately -40 °C and 70 °C (-40 °F and 158 °F), a laser 

sensor can turn off to prevent damage.16

•	 The rolling radius of the tire, which is related to tire

pressure and hence temperature, directly affects 

distance-measuring instrument measurements. 

•	 The interior vehicle environment can be critical to

the operation of on-board computers as many computers have a safe operating range of temperature 

that should be observed before power is applied. 

•	 Inclement weather conditions, such as rain, snow,

or heavy cross winds, can interfere with the collection of acceptable distress, FWD, and profile data. 

•	 The ability to see and rate some types of distresses is

very sensitive to lighting conditions, angle of the incident light, and light intensity.

These ambient condition considerations led to the 

issuance of formal LTPP program directives, such as 

these:

•	 Cessationof “NightTime”ManualDistress Survey

17

•	 Special Provisions forColdWeather FWD Testing.

18

•	 FWD Surface Temperature Measurements in Cold

Weather.19

•	 Data Collection Guidelines Under Less Than Ideal

Conditions.20

Most of these directives have been incorporated 

into the latest versions of the data collection guidelines 

discussed in the previous section. 

Monitoring and Reviewing Data Collectio

the Field

Reducing errors at the time of testing, when it is possible to correct a problem, is a priority within the LTPP 

program. It is standard procedure for the regional support contractor’s staff carrying out data collection 

activities to follow program guidelines and to continuously monitor the data being collected to ensure that 

the equipment is functioning properly and the data 

appear reasonable. If either questionable data or 

improperly functioning equipment is suspected during 

data collection, activities are suspended until the issue 

in question is resolved.

In the case of field activities, data collection personnel are required to survey the test section area to ensure 

there are no obstacles or debris on the pavement surface that could affect data collection. They are also 

required to check and to ensure that the start and end 

of each test section are well defined so that measurements are taken at the appropriate locations.

Once data collection activities begin, a number of 

monitoring tools are available to determine whether 

the data appear reasonable and the equipment is functioning properly. For example, cameras are installed on 

all LTPP FWD units to aid in establishing the accurate 

location for joint deflection tests on rigid pavements. 

Another example is the automated data checks contained in the LTPP FWD data collection software, 

which includes the following error conditions:

•	 Roll-off—Deflection of the pavement surface, as 

recorded by a deflection sensor, does not return to 

near zero within 60 milliseconds of the trigger 

activation. 

•	 Nondecreasing deflections—Deflections measured 

by the deflection sensors do not decrease with 

increasing distance from the load plate. 

•	 Overflow—A measured deflection exceeds the range 

of the deflection sensor or 2030 μm (80 mils) for the 

FWDs operated by the program.

•	 Load variation—The peak load for repeat drops at 

the same drop height varies by more than the 

amount specified. 

• Deflection variation—The load-normalized peak 

deflections for repeat drops vary by more than the 

amount specified. 

If deflection errors occur, the operator is required to 

attempt to identify the source of those errors. If the 
172    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

errors are determined to be due to problems with the 

FWD equipment, the problems have to be fixed before 

testing continues. If the errors are related to localized 

pavement conditions, the operator is required to reposition the FWD and comment on the condition. If the 

errors are determined to be due to pavement conditions that are representative of the test section as a 

whole or due to factors such as truck traffic that are out 

of the operator’s control, then the operator is required 

to accept the error and comment on the condition.

As described, there are many valid reasons why 

some of these “errors” may actually be an accurate 

reflection of pavement conditions, such as a transverse 

crack between sensors leading to a nondecreasing 

deflection warning. This is another example of why the 

LTPP program stresses the importance of using trained 

and experienced field personnel. 

Quality Control Tools to Check Equipment and 

Once data collection has been completed, field personnel are required to review the collected data prior 

to leaving the site. In the case of longitudinal profile 

data, for example, profiler operators use the LTPP 

ProQual software (discussed in chapter 6) to evaluate the acceptability of the profile runs based on 

established criteria. ProQual uses collected profile 

data to compute IRI values for the left and right

wheelpaths, as well as the average IRI of the two

wheelpaths (figure 9.4). 

Profiler operators are also required to use ProQual to 

perform a visual comparison of profile data collected by 

the left, right, and center sensors for one profile run. As 

a further check on the data, the operator compares the 

current profile data with those obtained during the previous site visit. If there are discrepancies between profiles from the current and previous site visits, the 

operator is required to investigate whether these differences were caused by equipment problems or were due 

to physical pavement features such as those caused by 

maintenance or rehabilitation activities.

After the profile visual comparison is completed, an 

IRI comparison of current versus previous site visit

data is also performed. If IRI values from the most

recent profiler runs meet the LTPP criteria and the 

operator finds no other indication of errors, no further 

testing is needed at that site.

Other examples of automated field data collection 

QC tools used within the LTPP program include the 

following:

•	 AWSSCAN—A program developed to permit field 

checks on the integrity and quality of the automated 

weather station data collected as part of the Specific 

Pavement Study (SPS) -1 (structural factors for flexible pavements), -2 (structural factors for rigid pavements), and -8 (environmental effects in the absence 

of heavy loads) experiments.

•	 ONSFIELD and MOBFIELD—Programs developed 

to permit field checks on the integrity and quality of 

the onsite and mobile data collected as part of the 

LTPP Seasonal Monitoring Program. They were 

used in the field to identify data anomalies whenever onsite or mobile seasonal data were collected.

There are also instances within the LTPP program 

where data collection is not automated, as is the case 

with manually collected distress data. In those instances, 

efforts were made to develop and implement procedures that ensure consistent and uniform data. In the 

case of the manual distress surveys, for example, the 

regional support contractors were required to run the 

DiVA (Distress Viewer and Analysis) software on each 

section’s data after the survey as part of the office 

review to identify inconsistencies among previous surveys. (The DiVA software is described in greater detail 

later in this chapter.) Furthermore, regional support 

contractor staff in the field are required to comply with 

the following policy:

Figure 9.4. ProQual software, used to evalu

the acceptability of profile data.
9: LTPP Data Quality Effo

•	 Raters assigned to perform a manual survey on an

LTPP test section must obtain a copy of the distress 

map made during the prior survey. (This map would 

have undergone office review and had any discrepancies and questions resolved before it was made 

available.)

•	 The prior survey map is to be used by the rater to

(1) become familiar with the types, severity, and 

quantities of distresses; (2) determine the survey 

limits; and (3) determine the wheelpath locations.

•	 The rater is then to map the test section independently: a new map, not an edited version of the prior 

map, is to be drawn.

The intent of this policy is to promote consistency, 

not to perpetuate errors. The rater is required to note 

disagreements with the prior map information and 

bring any issues to the attention of the office reviewer 

for resolution. In addition, inconsistencies with prior 

surveys are required to be documented by the rater 

using video or photographs. 

QUALITY CONTROL PROC

DATA COLL

After data have been collected, the regional support 

contractors carry out numerous quality checks before 

entering the data into the database. These checks range 

from basic—are profile data files readable and complete, is the manual distress data package complete, are 

survey date stamps correct—to sophisticated, as 

explained below. The primary objective of these data 

checks is to prevent “bad” (i.e., erroneous) data from 

being entered into the database. Examples of the data 

check tools developed by the LTPP program to avoid 

loading bad data into the LTPP database include: 

•	 AWSCHECK—Used for automated weather station 

data. In addition to range and integrity checks, the 

program plotted the climate data, allowing for timehistory consistency checks to be performed. This preprocessor program allowed deletion of bad measurement data and adjustments to data fields, corrected 

time stamps for daylight saving time, and prepared 

the data file for loading into the database. 

•	 FWDCHECK—Used until about 1996 to analyze deflection data to determine test section homogeneity, 

the degree to which test pit data are representative 

of the section, the presence of data outliers within 

the section, and overall reasonableness from a structural capacity viewpoint.

•	 FWDSCAN—Scans electronic FWD data files to 

identify data collection rule violation issues, data 

file format integrity, and range values violations. 

•	 P46CHECK—A preprocessor program that automates checks on the results of laboratory resilient 

modulus tests on unbound materials. In addition to 

all routine checks on data values, advanced statistically based checks are performed. 

•	 P07CHECK—A preprocessor program and a computed parameter generator. While the primary 

function of this preprocessor program is to check 

the integrity of the results of resilient modulus measurements in indirect tension on asphalt concrete 

(AC) cores, it also uses an algorithm to calculate the 

test results from the raw measurement data to store 

in the database.

•	 ProQual—Both a pre-upload data check processor 

program and a computed parameter generator (like 

P07CHECK). ProQual processes, evaluates, and 

generates computed parameters for both longitudinal and transverse profile measurements. The output files from this program are used as input files to 

load data into the database.

•	 SMPCHECK—A preprocessor program allowing 

deletion of bad data and time-based adjustments. In 

addition to automated range and integrity checks on 

the data, time-history plots of this temporal data are 

also used to identify data inconsistencies. Output 

files created by this program were used as input files 

to the database. 

•	 LTAS—LTPP Traffic Analysis Software, providing 

multiple functions (see sidebar).

Electronic data obtained from third parties are also 

evaluated and subjected to automated data checks 

before entry into the LTPP database. Two of the largest 

modules of data from other noncontract agencies are 

traffic monitoring data and climate data. The following 
174    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP Traffic Analysis Software (LTAS) provides 

multiple functions for evaluating and reviewing 

traffic data collected at the LTPP test sites by 

highway agencies and LTPP contractors. LTAS 

provides both graphical and automated range 

checks and statistical checks to identify suspect, 

invalid, duplicate, and erroneous traffic load and 

classification data.

Early in the program, each LTPP regional support contractor used in-house developed software to check the files received from highway 

agencies. These checks included detection of 

issues related to date gaps, lane identification, 

direction, station identification, start and end 

dates, times, left justification, optional agency 

data, blank lines, invalid line lengths, and the like, 

as well as sorting of the data. The files received 

were compared with the forms for classification 

and weight files submitted by the participating 

highway agency. Data identified as suspect were 

returned to the agencies for review and comment. 

Data identified as erroneous through this process 

were purged from the system before generation 

of annual traffic estimates. 

Later in the program, LTAS was developed to 

ensure uniformity and consistency of processing 

traffic data between LTPP regions and to provide 

detailed QC checks of the data prior to making 

them available to the public. LTAS is used to perform a detailed review that is used to identify 

data that are atypical for the time period and test 

site. The software currently performs quality 

checks on automated vehicle classification (AVC) 

and weigh-in-motion (WIM) data, which are output 

graphically. These checks include:

AVC Dat

1. Missing Hours in a 24-Hour Period 

2. 1:00 a.m. Volume > 1:00 p.m. Volume 

3. 8 Plus Hours of Consecutive Zeroes Check 

4. 4 Plus Hours of Static Non-Zeroes Volume

WIM Data:

5. Gross Vehicle Weight Distribution Curves 

for Class 9 Vehicles (and Other Trucks) 

6. Axle Distributions for All Vehicles 

7. Equivalent Single Axle Load per Vehicle

Variance Over Multiple Year

8. Tandem Axle Spacin

9. Class 9 Front Axle Weight Graph 

Comparison of AVC and WIM Da

10. Atypical Pattern 

11. Average Volume Match 

12. Match of Weight and Classification 

Volumes by Type of Vehicle

In addition to the QC graphs, LTAS has reports that 

can provide assistance in looking at the data to 

determine its accuracy. Some of these reports are:

1. Annual Summary Repor

2. Annual Summary Report—Class by Lane

3. Annual Summary Report—Weight by Lane

4. Annual Estimate Statistics

5.  Specific Pavement Studies Summary Re

The three Annual Summary Reports include monthly data, monthly statistics, and error summaries.

Since LTAS was first implemented in 2002, 

the software has evolved and continues to evolve 

to enable provision of high-quality data to LTPP 

data users.

Migration to LTAS: Exam

Quality C
explains the data checks that have been used by the 

LTPP program for these data:

•	 Traffic monitoring data are supplied by participating highway agencies in the standard data submittal 

formats described in FHWA’s Traffic Monitoring 

Guide,21 shown in figure 9.5. Screening and processing of the traffic data submitted by the highway 

agencies are described in the LTAS sidebar. 

•	 Until 2013, climate data were obtained from the

National Climatic Data Center and Environment 

Canada. Due to their large volume, these raw data 

were loaded into an independent set of database tables. Automated checks on completeness, range, 

and logical statistics were performed on the data, 

and flags were set in the records to store the results. 

Records not passing the LTPP QC checks were excluded from use in the analysis process that creates 

temporal summary climate statistics for each LTPP 

test site. This summary information was then loaded into the database.

DATABASE CHECKS AND 

As data are entered into the database by the regional 

support contractor, they undergo a hierarchy of automated, progressive QC checks. The results of these 

checks are recorded in the record status field. Every 

data record in the database starts with a record status 

of A. When a data record with a status of A passes all 

level B checks, it is assigned a status of B, and so on. 

(Chapter 8 provides more detail about the different 

quality checks performed on the data.) Over time most 

of the level-B checks were removed, which left three 

major types of database QC checks:

•	 Level C checks—Determine if all required fields 

within a specific table have been populated. In some 

cases, level C checks were supplanted by non-null 

restrictions placed on critical fields during the table 

design that prevented a record from being created if 

a value for that field was not entered.

•	 Level D checks—Determine if the values entered in a 

field are valid and reasonable. For example, the 

range check for deflection data from the center sensor on an FWD is 5 to 2032 μm (80 mils)

•	 Level E checks—Determine if the value in one field

of a table is comparable to the value in another field 

that may or may not be in the same table (commonly 

referred to as a “relational check”). For example, a 

level E check is used to see if pavement layer temperature gradient data exist for each FWD data set. 

The QC level checks are performed sequentially. 

Level D checks are applied only to records passing 

level C checks, and level E checks are applied only to 

records passing level D checks. Record statuses of A

and B are used for data that either have not undergone 

QC check processing or have not passed the level C 

checks. If a record fails a check, its record status 

remains at the next lower status. For example, records 

failing a level D check have a status of C. Alternatively, 

the record status can be manually upgraded if the 

record has been examined and has been found to be 

acceptable.

Records with level E status could mean either of the

following:

•	 Records have passed all of the data checks.

•	 Records may have failed some data checks but were

later manually upgraded after inspection.

In either case, level E records may contain errors 

that have not been detected by the data review process. 

On the other hand, records with a non-level E status 

could be interpreted as any of the following:

Figure 9.5. 

Traffic Monitoring 

Guide, published

by FHWA’s Off

of Highway Poli

to assist States

with collecting and

submitting traffic

data in a uniform

format to FHWA

9: LTPP Data Quality Effo
176    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 Records have not completed the QC process.

•	 Records have completed the QC process, but have

been left at a lower level because they contain an 

anomaly.

•	 Records have not been subjected to the QC process

by policy.

It is important to note that data users assume 

responsibility for conclusions based on their interpretation of the data collected by the LTPP program. 

Level E data should not be considered more reliable 

than non-level E data. Likewise, non-level E data 

should not be considered less reliable than level E 

data. The record status for non-level E data can be 

used as a relative indicator of potential issues or pavement anomalies that might exist for these data.

It was not practical, particularly when considering 

the wide variety of materials, climatic conditions, and 

local practices, to inspect all of the data for all types of 

potential anomalies. As the program evolved and 

improvements were made to the data QC checks, 

level E data included in previous releases may have 

been reclassified. It is also important to note that the 

LTPP program works diligently to identify and 

address critical data errors. 

Likewise, it is important to recognize that the program has established standard and formal methods for 

the correction of data errors identified from the database checks. It is the LTPP program’s policy to not load 

known “bad” data into the database, which is why the 

automated data check processors and screening methods were developed. Although steps are taken to prevent entry of erroneous data, with such vast quantities 

of data coming from multiple sources, there are 

instances when data in the database are still found to 

contain typographical errors. 

When data errors are identified, the standard 

response is to correct the error if possible, to remove 

the data from the database, or to place the data at a 

lower data quality status. Error correction procedures are transmitted by LTPP program directives 

such as “Manual Upgrades to QC Checks,” which 

describes the steps to take when data fail an automated check.22

During the QC error resolution process, errors that 

are not possible to rectify are also identified. Some 

examples include:

• Equipment measurement errors. When a record failing a QC check can be traced to an identifiable 

equipment measurement error, manual upgrades 

cannot be employed to elevate a data element to a 

higher status. 

• Required data not available. Circumstances can 

develop where critically required data are not available. There are instances when a required data element was not collected, was collected improperly, 

or is no longer possible to obtain or measure (e.g., 

thickness of an AC layer that was subsequently 

milled). In these exceptional circumstances, a test 

section may be removed from the LTPP study. 

• Issues requiring investigation. When new tables are 

added to the database or new QC programs are issued, some records failing a QC check require further investigation to determine the cause. There are 

instances when it cannot be immediately determined if the error was a result of equipment malfunction, abnormal phenomenon, or program error. 

Some of these problems are resolved through the 

Software Performance Report (SPR) process, which

is discussed later in this chapter. 

The above database checks and review guidelines 

apply to data after entry into the LTPP database. Error 

correction guidelines are also contained in the field 

data collection and processing documents. 

After the data have been entered into the LTPP 

database and have undergone checks by the regional 

support contractors, the technical support services 

contractor’s staff reviews the contents of the entire 

database before releasing data to potential users. See 

chapter 8 for illustrations of the data flow and QC 

checks at different points in time. Data problems 

identified following release are documented using the 

Data Analysis/Operations Feedback Report (DAOFR)

process, which is discussed later in this chapter.
9: LTPP Data Quality Effo

LTPP QUALITY ASSURANCE 

There are two types of QA procedures the LTPP program follows to maintain a high quality level in the database. These efforts, performed by the program staff, the 

technical support services contractor, and the regional 

support contractors, are discussed below.

LTPP Quality Assurance Audits

Since the early days, the LTPP program has performed 

QA audits of data collection contractor activities, 

including those of the regional support contractors, 

materials testing laboratories, central pavement distress data contractor, and FWD calibration centers. 

However, those audits were not formalized until 1998 

through “LTPP Regional Operations Quality Assurance Reviews,” a program directive that enhanced and

further standardized the data collection process used 

by the regional contractors.23 This directive required, 

on a routine basis, the conduct of QA reviews of the 

regional data collection contractors in the areas of 

automated weather stations, distress, FWD, profile, 

and the Seasonal Monitoring Program.

After implementation of the directive, multiple QA 

reviews of regional support operations were conducted each year by teams consisting of four highly qualified individuals, typically including one from the LTPP 

program, two from the technical support services contractor, and one from a regional support contractor 

other than the one under review. These teams reviewed 

field and office operations during the course of their 

visits, sometimes together and at other times independently. Members of the review team were not allowed 

to interact with data collection or office personnel during the conduct of their activities; the reviewers could 

only observe and take notes.

Regional contractors were rated by the review

team as being “Fully Compliant,” “Compliant—Minor 

ChangesRequired,” or “Non-Compliant—MajorChanges

Required,” depending on how closely LTPP guidelines

and directives were followed. Individual personnel 

were also given a “Compliant” or “Non-Compliant” 

rating on the basis of the review results. In the event 

that one or more individuals were found to be “NonCompliant,” the contractor was required to submit a 

remediation plan to the LTPP program office within 

15 days of receiving such a rating. A follow-up review 

of “Non-Compliant” personnel was conducted within 

6 months after the initial review and if at that time the 

individuals were still rated “Non-Compliant,” they were 

not allowed to collect data for the LTPP program until 

they were found to be compliant at a later review. Beginning in December 1998, only contractor personnel rated 

“Compliant” were permitted to collect LTPP data.

QA audits were also performed on FWD reference 

calibration facilities used by the program and operated 

under cooperative agreements with selected highway 

agencies. The facilities used LTPP-provided equipment and followed LTPP test protocols. Annual audits 

were performed in conformance to test protocols, 

audit results were documented, and certificates of 

compliance were issued.

QA audits for materials testing were performed 

independently by the American Association of State 

Highway and Transportation Officials (AASHTO). The 

LTPP program required that the materials testing contractors be certified by AASHTO standards. 

In 2001, LTPP’s approach to QA audits was significantly revised with the re-letting of the four regional 

LTPP data collection contracts. As part of those contracts, FHWA required the regions to formally document their data collection and processing QC systems 

in accordance with ISO (International Organization 

for Standardization) 9001 quality management systems accreditation standards. The documents were 

referred to as “Regional Operations Quality Control

and Data Flow Plans,” as described in the following 

section. Some of the relevant features of this management process include:

•	 Designation of aRegional Data QC Manager on each

regional contractor’s staff, with the following responsibilities: 

– Conducting both regularly scheduled and impromptu internal audits of compliance with QC, 

data collection and data processing guidelines, 

and procedures. 

– Documenting internal audits.

– Documenting corrective actions resulting from 

internal and external audit findings.

– Conducting annual, or more frequent, reviews and 

updates of the QC and management procedures.
178    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 The technical support services contractor established a QA audit team and process to assess compliance by the regional support contractors with 

their data QC and management guidelines and 

compliance with LTPP program requirements. The 

QA audits include the following: 

– Announced field or office visits to review designated sections of the QC and management plans. 

The different parts of the plans are rotated so 

that each part is reviewed on a 2-year cycle, budget permitting. Prior to an audit, a data review is 

conducted to identify data issues of concern to be 

investigated during the audit. 

– Unannounced audits of field data collection or 

office personnel. Auditors arrive unannounced to 

observe activities and compliance with both the 

contractor’s internal requirements and the LTPP 

program’s requirements. 

– A documented audit report that includes a description of audit activities, items reviewed, 

positive findings, corrective action requests, 

and improvement recommendations. All corrective action requests and improvement recommendations are discussed with the regional 

support contractor in order to reach an agreement on corrective actions to be taken. On each 

audit visit, all corrective action findings and 

improvement requests previously agreed to are 

reviewed. 

Regional Quality Control and Data F

Management Plans

Each region developed a formal Regional Operations

Quality Control and Data Flow Plan circa 2001. These 

QC plans specified data collection, processing activities, data flow, and roles, responsibilities, and qualifications of staff members by position. QC activities 

were put in place to provide formal checks to identify 

bad, erroneous, and missing data prior to entry into 

the database. The regional contractors submitted QC 

and data flow plans for the following data elements:

•	 Deflection measurements.

•	 Longitudinal profile measurements.

•	 Distress surveys.

•	 Seasonal Monitoring Program data.

•	 Automated weather station data.

•	 Traffic data.

•	 Maintenance and rehabilitation data.

•	 Materials sampling and testing.

•	 Information Management System.

Plans varied among the regions; for example, the 

North Atlantic Regional Support Contractor developed the first LTPP QC plan for the automated weather station. Initially this region prepared a separate 

document for each data element, but later combined 

these into one document. In contrast, the Western 

Regional Support Contractor prepared a single document covering the QC processes for all of the data elements they collected and processed.

In 2004, the regional support contractors developed 

Working Guides as a means of standardizing regional 

procedures and ensuring consistency in training, field 

data collection, maintenance, calibration, and the processing and uploading of data. The purpose of these 

guides was to ensure compliance with the Data Quality 

Act.24 In the North Atlantic Region, individual Working Guides were issued for each data element (like the 

initial QC and Data Flow Plans). 

HIGHER ORDE

Although the QC processes discussed in the previous 

sections of this chapter can identify a wide array of 

data issues or problems, they cannot identify all of the 

potential data problems. Once these initial QC efforts 

have been completed, higher order data checks and 

reviews are used to identify other types of data issues. 

Important higher order review activities within the 

program include time-series checks, data studies, and 

engineering data analysis techniques. The term “data 

study” was introduced into the LTPP lexicon to indicate intensive higher order data reviews that employ a 

variety of analysis techniques performed against the 

entire LTPP data set and data subsets. While not in 

explicit alignment, these data studies tend to serve the 

same purpose as the level 2 QC checks described in the 
9: LTPP Data Quality Effo

Strategic Highway Research Program (SHRP) 5-year

report on the LTPP Information Management System 

(IMS).25 The final tier of higher order data checks 

comes from the results of formal analysis of LTPP data.

Time-Series Chec

An important higher order review activity performed 

within the LTPP program is the time-series review of 

pavement section performance data. In the case of distress data, for example, once data have been uploaded to 

the database, time-series checks are performed using 

the DiVA program. This software automates extraction, 

compilation, and time-series review of distress data 

from the database. The key subset of distresses included 

in the time-series review by pavement type is summarized below by pavement surface type:

•	 Asphalt-concrete-surfaced pavements—fatigue cracking, longitudinal cracking, transverse cracking, 

patch/patch deterioration, and block cracking.

• Jointed concrete pavements—corner breaks, longitudinal cracking, transverse cracking, and patch/

patch deterioration.

•	 Continuously reinforced concrete pavements—longitudinal cracking, transverse cracking, patch/patch 

deterioration, and punchouts.

The DiVA software produces a graph of the selected 

distress versus time for each section and distress type, 

starting from the time the test section was included in 

the LTPP program. An example is shown in figure 9.6. 

The graph includes both photographic and manual distress data for each test section along with error bands 

around the individual data points and a trend (best-fit) 

line to aid in the review. The variability bands are 

applied to the total quantity of distress—the sum of 

quantities over all severity levels. The upper and lower 

limits of each distress represent three standard deviations. Ninety-nine percent of the data from a given data 

set are expected to fall within three standard deviations of the mean of that data set.

Actions resulting from the time-series review vary 

from data being acceptable (most common outcome), 

to identification of issues that may be caused by correctable items such as unreported maintenance or 

rehabilitation activities on the test section (most common issue), to correction of individual distress data 

classification issues (infrequent occurrence). 

Data Studies

In addition to the time-series checks, another important higher order review activity within the program is 

the conduct of data studies using data extracted from 

the database. Data studies are also used to develop, refine, 

or implement new or advanced data collection systems. 

Some examples of data studies conducted by the LTPP 

program include:

Figure 9.6. A distressversus-time gr

produced by the DiVA

software.
180    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

•	 LTPP distress data variability study—Since the 

methods used to rate pavement distresses rely on 

subjective interpretation by trained personnel, a 

study was conducted in 1997 to examine variability 

between raters and between rating methods.26

Based on a statistical sample of data obtained from 

nine distress rater accreditation workshops (and 

later updated and confirmed with data from an 

additional 13 distress rater accreditation workshops),27 the study was conducted by engineering 

and statistical experts and peer-reviewed by the 

Transportation Research Board’s (TRB) ETG on

Pavement Distress Monitoring. In addition to documenting probable ranges of uncertainty in distress measurements, the study provided recommendations on improving the rating methods that 

were implemented into the LTPP distress rater 

accreditation process, thereby reducing future 

distress data variability. 

• LTPP distress data consolidation study—The objectives of this study were to produce a comprehensive 

consolidated distress data set and to reconcile differences between data collected using photographic 

and manual methodologies. This study led to the 

implementation of the distress data time-series 

checks using the DiVA software, which, in turn, led 

to the identification and correction of numerous 

discrepancies: 17 percent were attributed to human 

error, 6 percent to data collection methodology, 

36 percent to the strategies used in the study, and 

41 percent were unidentifiable.28

•	 LTPP AC resilient modulus data study—A data study 

was performed on the resilient modulus test, developed by the LTPP program, for AC mixes in indirect 

tension. Due to the severity of the problems found 

with the data from these tests and the uncertainty 

associated with test results, which had originally 

appeared reasonable, significant amounts of data 

were archived, removed from the database, and not 

distributed to the public.29

•	 LTPP field data collection equipment studies—As a 

part of the QC process, data studies are routinely 

performed on the LTPP FWDs and pavement profilers. These data studies typically consist of a statistically designed experiment that uses an analysis of 

variance approach to evaluate the results of side-byside equipment comparisons. These procedures are 

also used to evaluate equipment during the procurement process. 

•	 FWD calibration center pooled-fund study—A Statesponsored pooled-fund study, managed by the LTPP 

program, was established to investigate and improve 

the LTPP-developed FWD calibration protocols. 

The purpose of the study was to evaluate current 

methods, procedures, and instrumentation and develop an improved system compatible with current 

computer technology.30

Data Analyses

The last tier of LTPP higher order review activities 

is associated with the performance of formal data 

analysis projects. A multiproject approach, by topic 

area, is used for analysis of LTPP data. The LTPP 

program, other FHWA program offices, the National 

Cooperative Highway Research Program, and the

States have sponsored many research analysis projects that have used LTPP data. More detailed information concerning LTPP data analysis efforts is 

provided in chapter 10.

LTPP-sponsored analysis projects are primarily 

intended to yield insights, benefits, and products from 

analysis of the data. A fundamental requirement of any 

research investigation is evaluation of the empirical 

data used in the investigation. In recognition that the 

operational structure of the LTPP program serves to 

provide relevant data of known quality for achievement of program goals through analysis of the collected data, the DAOFR process, discussed below, was

established in 1998.31 Over time, the DAOFR process

has been used to report suspect data issues discovered 

in data analyses and studies by users both within and 

outside the LTPP program.
9: LTPP Data Quality Effo

PEER REV

An integral component of LTPP’s data quality 

approach is extensive peer review, both external and 

internal, of the various program areas and activities. 

At the start of the program, an external peer review 

process was created to monitor the status and progress of the LTPP studies and provide technical assistance to SHRP and later to FHWA, as discussed in

chapter 2 and appendix A. The TRB LTPP Committee

and its ETG structure incorporated experts and practitioners from the highway pavement community and 

provided advice regarding the technical and managerial direction of the LTPP program. National outreach 

stakeholder meetings such as the 1990 SHRP Assessment Meeting in Denver, Colorado; 1996 SHRP LTPP

National Meeting in Irvine, California; 2000 LTPP 

SPS Workshop in Newport, Rhode Island; and 2010

LTPP Pavement Analysis Forum in Irvine, California, 

provided additional external peer review input on 

LTPP program activities. 

Internal peer review is also a major contributor to 

high-quality data and the program’s success. Internal 

peer review touches on every element of the program, 

including the various QC/QA activities described in 

this chapter. 

A few highlights of LTPP peer review activities, 

both external and internal, are summarized below:

•	 The LTPP experiment designs were developed and

reviewed by statisticians with pavement research 

experience. These designs were also reviewed by an 

ETG consisting of statisticians and pavement 

research engineers.

•	 The LTPP data requirements were developed by

experts in each of the engineering disciplines associated with the program. These requirements were 

reviewed and critiqued by other stakeholders 

through TRB-facilitated national meetings. This

process continues.

•	 The LTPP data collection guidelines are developed

by experts in each of the engineering disciplines

associated with the program. These guidelines are 

reviewed and critiqued by the appropriate TRB

LTPP ETGs.

•	 Before the contents of the database are released,

they are reviewed by experts and specialists on 

the technical support services contractor’s staff. By 

design, these review staff are not involved with data 

collection or analysis.

•	 The LTPP Strategic Plan for Data Analysis was developed and continues to be refined based on input 

from program staff, highway agency personnel, industry stakeholders, and academicians through an 

outreach process.32 The plan was developed in 

concert with the LTPP ETG on Data Analysis, and 

it is periodically updated using the ETG peer review process. Review of LTPP-sponsored data

analyses and reports is based on a formal peer review process. Data analysis documents that contain estimates and projections are required to contain a description of the analysis methodology, and 

they receive both an internal and an independent 

external review by subject matter experts before 

publication.

•	 All published LTPP reports use the FHWA publication process, which includes editorial review 

for conformance with FHWA publication standards and provides a report documentation page. 

Since the introduction of section 508 of the Rehabilitation Act, LTPP publications have been formatted in conformance with the Act and reviewed 

by individuals trained in section 508 compliance 

standards.

Furthermore, to allow input from both external and 

internal sources, better serve its customers, and 

determine customer satisfaction, the LTPP program 

provided customer support services and customer 

survey processes starting in 1989. In 2006, FHWA 

moved the formal LTPP Customer Support Service 

Center to its Turner-Fairbank Highway Research

Center, in McLean, VA.
182    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

FEEDBACK PROCE

Another important data quality element is the feedback process. Initial LTPP feedback efforts were 

mostly limited to national and regional meetings 

involving LTPP State Coordinators and regional 

support contractors. Teleconferences were also held 

with the data collection staff from the regional support contractor offices. These meetings and conferences were scheduled as needed and allowed 

problems, ideas, and solutions to be shared among 

all participants.Later, more formal procedures (OPRs,

DAOFRs, and SPRs) were established to ensure

that the feedback processes contribute toward the 

improvement of data quality and to the LTPP program’s success.

Operational Problem Repo

The first LTPP feedback mechanism, formally implemented by policy in 1995, was the OPR form, which

enables personnel in the regions to report problem 

issues—equipment, software, and procedural problems 

associated with data collection, and, in particular, 

uncommon circumstances. This feedback mechanism 

provides a uniform way of reporting, handling, and 

tracking problems associated with the LTPP automated weather station, distress, FWD, profile, and seasonal 

monitoring data. Over time, LTPP program directives 

were issued extending and formalizing the OPR process to different data collection areas, such as materials 

sampling and testing.

A log of the OPRs is used to track the circumstances

oftheproblemsandtheir resolution.OPRsarereviewed,

analyzed, and discussed by the LTPP program and contractor staff during teleconferences, and resolutions are 

provided by the regional support or technical support 

services contractors. Quarterly updates are sent to the 

program office and regions. 

The OPR feedback process has resulted in several

major benefits: standardizing the process for submitting problems associated with data collection activities; simplifying tracking when a problem was 

submitted, who was responsible for resolving it, 

whether or not it had been resolved, and how and 

when it was resolved; and reducing the probability of 

issues being forgotten or resolutions not making it 

back to the problem’s initiator. More than 400 OPRs

had been submitted and resolved by 2014.

Data Analysis/Operations Feedback Repo

The second LTPP feedback mechanism formally instituted by policy (in 1998) was the DAOFR process,33

which enabled users of the database to report issues 

encountered during data analysis that suggest or demonstrate the need for corrective actions or further 

investigation (figure 9.7). In an effort to examine all 

data in the database, the program developed a series of 

DAOFRs for use by the regional support contractors

and data analysts to provide commentary and to load, 

edit, fix, clean, or remove any suspect data collected by 

the regions or received from the highway agencies. 

The approach to completing DAOFRs varies for each

data collection element. For example, the Traffic 

DAOFR process started with the out-of-study sites

(sites that were no longer being monitored) as well as 

the tables that had been completely populated (no new 

data were expected) or were part of the module closeouts. Data for active SPS and General Pavement Study 

sites were examined next.

The DAOFR form and DAOFR resolutions are available to LTPP data users online.34 Situations in which 

use of the DAOFR process is appropriate include the

absence of critical data for specific test sections; data 

that appear to be incorrect, contradictory, or otherwise 

suspect; data not collected but necessary to fill voids 

identified in the analysis; and recommendations arising from the analysis regarding data collection procedures that can be improved. By 2014, close to 1,400 

DAOFRs had been submitted.

Software Performance Repor

An early program feedback effort was the implementation of the LTPP database SPRs, which the contractors used to report problems, comments, change 

requests, and document changes made to the database management software. Although suggestions 

for software diagnosis and correction are often provided via phone calls and emails, actual diagnosis 
9: LTPP Data Quality Effo

(by re-creating the conditions and modifying the software) occurs via the SPR process. An SPR submitted

on a specific version of software includes a concise 

description of the problem and relevant extractions 

of test section information. 

The SPR process was put in place in the early 1990s,

and an SPR form was adopted to report issues with the

traffic software in 1996,35,36 but the SPR process was

not formally implemented by policy until 2005.37,38 In 

2011, the SPR form was Web-enabled.39 In all, more 

than 4,300 pavement performance database and traffic 

SPRs have been submitted.

Conformanc

Qual

Sta

Another important approach to data 

quality that was implemented by the 

LTPP program in the early years was to 

adopt existing concepts in other large 

databases to maintain consistency 

across the database. Such adoptions 

include the following:

•  Federal Information Processing Standards for geographic code

•  National Transportation Thesaur

for keywords.

•  World Geodetic System 1984 for location coordinates

•  AASHTO classification system f

soils and unbound base material.

•  AASHTO materials testing standard

•  American Society for Testing a

Materials test standards.

Still another data quality approach 

implemented from 2006 to 2008 was 

the self-assessment of the program relative to its compliance with U.S. Department of Transportation Information 

Dissemination Quality Guidelines, and 

the resulting report, as discussed in 

chapter 8.40,41

SUMMA

LTPP QC/QA practices have resulted in a high-quality 

pavement performance database. The program’s quality 

expectations have created an environment that 

promotes advancements in QC processes to help in 

understanding pavement performance. The program 

has developed an extensive and robust set of modern 

pavement engineering QC methods and tools, several of 

which have been adopted by the pavement engineering 

Figure 9.7. LTPP Data Analysis/Operations Feedback Report, u

provide feedback to the program regarding data that require investigation or correction.
184    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

community. These and other products are discussed in 

the next chapter. The next section also includes chapters on lessons learned and plans for the future.

REFERE

 1. J. S. Miller and W. Y. Bellinger. Distress Identification 

Manual for the Long-Term Pavement Performance 

Program (5th rev. ed.) (FHWA-RD-13-092). Federal

Highway Administration, McLean, VA, May 2014. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/13092/13092.pdf.

	 2.	R. W. Perera, S. D. Kohn, and G. R. Rada. Long-Ter

Pavement Performance Program Manual for Profile 

Measurements and Processing (FHWA-HRT-08-056).

Federal Highway Administration, McLean, VA, 

November 2008. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/08056/08056.pdf.

 3. Directive P-49, “LTPP Manual for Profile Measurements 

and Processing, December 2013—Revised Appendix B.”

Mar. 11, 2014. Federal Highway Administration, McLean, 

VA. http://ltpp.org.phtemp.com/dirs/PRF/P-49.pdf.

4. P. N. Schmalzer. Long-Term Pavement Performance 

Manual for Falling Weight Deflectometer Measurements, 

Version 4.1 (FHWA-HRT-06-132). Federal Highway

Administration, McLean, VA, December 2006. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/06132/06132.pdf.

	 5.	Directive D-10, LTPP Distress Rater Qualifications,” Fe

7, 1997. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-10.pdf.

 6. Directive D-46, “LTPP Distress Data Quality—

Accreditation of Distress Raters,” Oct. 21, 2005.

Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-46.pdf.

	 7.	Directive D-10, “LTPP Distress Rater Qualifications,” Fe

7, 1997. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/DIS_01-49/D-10.pdf.

 8. PCS Law. Accreditation for the Long-Term Pavement 

Performance Studies Pavement Distress Raters (SHRPP-653). Strategic Highway Research Program, National

Research Council, Washington, DC, 1993, p. 13. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-653.pdf.

	 9.	AASHTO R32-03. “Calibrating the Load Cell a

Deflection Sensors for a Falling Weight Deflectometer.” 

Standard Specifications for Transportation Materials 

and Methods of Sampling and Testing, Part 1B: 

Specifications, American Association of State Highway 

and Transportation Officials, Washington, DC, 2006.

	10.	AASHTO R 32-09. “Calibrating the Load Cell a

Deflection Sensors for a Falling Weight Deflectometer.” 

Standard Specifications for Transportation Materials 

and Methods of Sampling and Testing, Part 1B: 

Specifications, American Association of State Highway 

and Transportation Officials, Washington, DC, 2010.

 11. “FWD Calibration Improvements and Plans for the 

Future.” LTPP Newsletter, vol. 5, no. 4, Fall 2009, pp. 1–3. 

http://www.fhwa.dot.gov/publications/ltppnews/

LTPPFall2009.pdf.

 12. S. Slavi, T. Merport, T. Wilson, J. Groeger, and A. López. 

LTPP Materials Characterization Program: Resilient 

Modulus of Unbound Materials (LTPP Protocol P46) 

Laboratory Startup and Quality Control Procedures

(FHWA-RD-96-176). Federal Highway Administration,

McLean, VA, January 1997. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/96176/96176.pdf.

 13. J. L. Groeger and A. Bro. Long-Term Pavement Performance Materials Characterization Program: Verification 

of Dynamic Test Systems With an Emphasis on Resilient 

Modulus (FHWA-RD-02-034). Federal Highway

Administration, McLean, VA, September 2005. http://

www.fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/02034/02034.pdf.

	14.	 “New Profilers Hit the Road Smoothly.” LTPP Newsletter

vol. 9, no. 2, Spring 2013, pp. 1–2. http://www.fhwa.

dot.gov/publications/ltppnews/13074.pdf.

 15. Soil and Material Engineers. 2007 Comparison Testing 

of LTPP Profilers Final Report. Federal Highway 

Administration, McLean, VA, October 2007. 

http://www.infopave.com/InfoPave_Repository/

Reports/C20/C20_70/rodeo07.pdf.

	16.	R. W. Perera and G. E. Elkins. LTPP Manual for Profil

Measurements and Processing. Federal Highway 

Administration, McLean, VA, December 2013. 

http://www.ltpp.org/Profiler_Manual_12-19-13.pdf.

 17. Directive D-19, “Cessation of ‘Night Time’ Manual 

Distress Surveys,” May 10, 2000. Federal Highway 

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/DIS_01-49/D-19.pdf.

 18. Directive FWD-5, “Special Provisions for Cold Weather 

FWD Testing,” Jan. 28, 1994. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/

dirs/FWD/FWD-05.pdf.

 19. Directive FWD-14, “FWD Surface Temperature 

Measurements in Cold Weather (below 0°F),” Feb. 1, 

1995. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/FWD/FWD-14.pdf.

 20. Directive SM-07, “Data Collection Guidelines Under 

Less Than Ideal Conditions,” Mar. 14, 1995. Federal 

Highway Administration, McLean, VA. http://ltpp.org.

phtemp.com/dirs/SMP/SM-07.pdf.
9: LTPP Data Quality Effo

 21. Traffic Monitoring Guide. Federal Highway 

Administration, Office of Highway Policy Information, 

Washington, DC, September 2013, ch. 7. http://www.

fhwa.dot.gov/policyinformation/tmguide/tmg_fhwa_

pl_13_015.pdf. 

 22. Directive I-85, “Guidelines for Manual Upgrades to 

LTPP IMS Quality Control Checks,” Mar. 24, 2003. 

Federal Highway Administration, McLean, VA. http://

ltpp.org.phtemp.com/dirs/IMS_050-099/I-85.pdf.

	23.	Directive GO-6, “LTPP Regional Operations Quali

Assurance Reviews,” Apr. 1, 1998. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/GO_01-49/GO-06.pdf. 

 24.U.S. Statutes at Large 114 (2000): 2763A-153. Treasury 

and General Government Appropriations Act for Fiscal 

Year 2001. http://www.gpo.gov/fdsys/pkg/PLAW106publ554/pdf/PLAW-106publ554.pdf.

 25. W. O. Hadley and C. Copeland. Long Term Pavement 

Performance Information Management System: 

Five-Year Report (SHRP-P-679). Strategic Highway

Research Program, Washington, DC, March 1994.

http://onlinepubs.trb.org/onlinepubs/shrp/SHRPP-679.pdf.

	26.	G. R. Rada, C. L. Wu, R. K. Bhandari, A. R. Shekhara

G. E. Elkins, and J. S. Miller. Study of LTPP Distress 

Data Variability, Volume I (FHWA-RD-99-074). Federal

Highway Administration, McLean, VA, September 

1999. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/99074/99074.pdf.

	27.	G. R. Rada, A. L. Simpson, and G. E. Elkin

“Updated LTPP Manual Distress Data Bias and 

Precision Estimates” (Report No. 07-0419), in TRB 86th

Annual Meeting Compendium of Papers CD-ROM,

Transportation Research Board, Washington, DC, 2007.

http://pubsindex.trb.org/view.aspx?id=801092.

 28. A. L. Simpson and J. F. Daleiden. Distress Data 

Consolidation, Final Report (FHWA-RD-01-143).

Federal Highway Administration, McLean, VA, October 

2003, p. 34. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/

reports/01143/01143.pdf.

 29. A. Yau and H. L. Von Quintus. Study of LTPP Laboratory 

Resilient Modulus Test Data and Response Characteristics:

Final Report(FHWA-RD-02-051). Federal Highway

Administration, McLean, VA, October 2002. http://

www.fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/reports/02051/02051.pdf.

 30. L. H. Irwin, D. P. Orr, and D. Atkins. FWD Calibration 

Center and Operational Improvements: Redevelopment 

of the Calibration Protocol and Equipment (FHWAHRT-07-040). Federal Highway Administration,

McLean, VA, October 2011. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07040/07040.pdf.

 31. Directive GO-15, “Data Analysis/Operations Feedback 

Process,” Nov. 9, 1998. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

GO_01-49/GO-15.pdf.

32. “Long-Term Pavement Performance Data Analysis 

Program: Strategic Plan Objectives, Analysis Outcomes, 

and Supporting Projects.” Dec. 11, 2013. Web page. 

http://www.fhwa.dot.gov/research/tfhrc/programs/

infrastructure/pavements/ltpp/pdf/tablecloth_

complete.pdf.

33. Directive GO-15, “Data Analysis/Operations Feedback 

Process,” Nov. 9, 1998. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

GO_01-49/GO-15.pdf. 

	 34.	 “LTPP Data Analysis/Operations Feedback Report.”

http://www.fhwa.dot.gov/research/tfhrc/programs/

infrastructure/pavements/ltpp/getdata.cfm.

	 35.	Directive TDP-05, “Software Performance Report

(SPR) Form,” May 28, 1996. Federal Highway Administration, McLean, VA. http://ltpp.org.phtemp.com/dirs/

TDP_01-49/TDP-05.pdf.

 36. Directive TDP-40, “Traffic Data Processing Software 

Performance Reports,” June 10, 2005. http://ltpp.

org.phtemp.com/dirs/TDP_01-49/TDP-40.pdf.

 37. Directive I-123, “Pavement Performance Database 

Software Reports,” June 10, 2005. Federal Highway

Administration, McLean, VA. http://ltpp.org.phtemp.

com/dirs/IMS_100-149/I-123.pdf.

	38.	Directive I-152, “Software Performance Reports,” Aug.1

2011. Federal Highway Administration, McLean, VA. 

http://ltpp.org.phtemp.com/dirs/IMS_150-199/I-152.pdf.

	39.	Directive I-155, “Software Performance Reports

Dec. 19, 2011. Federal Highway Administration, 

McLean, VA. http://ltpp.org.phtemp.com/dirs/

IMS_150-199/I-155.pdf.

 40. DOT Report for Implementing OMB’s Information 

Dissemination Quality Guidelines. U.S. Department of 

Transportation, Research and Innovative Technology

Administration, Bureau of Transportation Statistics, 

Washington, DC, August 2002. http://www.rita.dot.

gov/bts/sites/rita.dot.gov.bts/files/subject_areas/

statistical_policy_and_research/data_quality_

guidelines/index.html. 

 41. G. E. Elkins. Long-Term Pavement Performance 

Compliance With Department of Transportation 

Information Dissemination Quality Guidelines 

(FHWA-HRT-08-065). Federal Highway

Administration, McLean, VA, November 2008. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/08065/08065.pdf.

Creating Products, Learning From the Past,

 and Preparing for the Future

III
188 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP program continues to develop and 

distribute its data, knowledge, and software tools 

to improve understanding of pavement 

performance, the quality of pavement research, 

and industry practice.

© hxdyl/Shutterstock.com
10: Turning LTPP Data INTOESU

Turning LTPP Data into Results

10

Introd

When pavement designers in Houston determine what 

materials and base structure an alternate truck route 

should incorporate, or when engineers ponder the 

effects of the hot dry climate on highways in Phoenix, 

the LTPP database is freely accessible to help them 

make crucial choices. Thanks to the foresight of a generation of engineers and administrators who knew the 

value that comprehensive pavement performance data 

would have for the future, the LTPP program has more 

than paid for itself in delivering dozens of products 

that have improved our highway system.

This chapter describes some of the more important 

contributions achieved through LTPP research, data 

analysis, and product development. In numerous studies over the years, pavement researchers have used 

LTPP data in the evaluation and development of design 

While providing a treasure trove of information for researchers, the LTPP program also focuses on providing 

products to pavement practitioners at the local, State/Province, and national levels. By developing and 

following strategic data analysis and product development plans, the program has directly supported a wide 

range of improvements to pavement management, design, and construction practices. These benefits have 

resulted in cost savings in the millions of dollars for highway agencies.

procedures, most recently in the development of the 

Guide for Mechanistic-Empirical Design of New and 

Rehabilitated Pavement Structures (MEPDG). Analysis 

has led to improvements in pavement management 

systems, with new insights into the performance of 

rehabilitation and maintenance activities. LTPP data 

analysis has also led to many innovations and tools that 

pavement researchers and engineers are using to 

advance pavement quality and durability. 

LTPP DATA ANALYSI

Designing the experimental matrices, defining data 

collection procedures, and developing and populating 

the database are all critical steps to enable the LTPP 
190 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Key Milestones in Turning LTPP 

Data Into Results 

1992 First calibration protocol for FWDs 

finalized

1994 First SHRP-LTPP data analyses 

published

1997 NHI develops LTPP-based distress 

rating course

1997 Vehicle Classification Report 

published

1998 ASCE-LTPP International Data 

Analysis Contest introduced

1998 NCHRP MEPDG project begins using 

LTPP data to develop new design 

software

1999 FHWA-LTPP updates SHRP Manuals 

of Practice 

1999 AASHTO adopts LTPP-developed 

Standard Practice R 32

1999 LTPP Strategic Plan for Data 

Analysis adopted

2001 LTPP Product Plan published

2001 ProVAL software released

2006 Pavement Performance Forecast 

Online developed

2007 ProVAL software’s data format 

becomes ASTM standard

2010 Major review and update of LTPP 

Strategic Plan for Data Analysis

2011 LTPP Dynamic Modulus Prediction 

software developed

2013 Update of the LTPP Strategic Plan 

for Data Analysis

2014 ProQual software updated

program to address its end objectives. Answering key 

questions requires a robust data analysis program. 

Although LTPP data analysis activities have been 

impacted by funding challenges over the years, nonetheless, significant resources have been invested into 

analyzing the data, and substantial returns have already 

been realized. Some notable examples are introduced 

in this section.

Early Analyses

SHRP-P-020 Contract—Data Analysis

As the first major effort under the Strategic Highway 

Research Program (SHRP) to use LTPP data for specific analytic purposes, the SHRP P-020 contract supported a number of studies to accomplish a variety of 

research objectives:

• To better understand the effects of a broad range of 

loading, design, environmental, materials, construction, and maintenance variables on pavement performance.

• To evaluate and improve the American Association 

of State Highway and Transportation Officials’ 

(AASHTO) overlay design procedures.

• To evaluate and improve models included in the 1986 

AASHTO Guide for Design of Pavement Structures.1

• To plan for future analyses when the General Pavement Studies (GPS) and Specific Pavement Studies 

(SPS) time-sequence data would become more 

available.

The studies, conducted in 1992 and 1993, utilized GPS 

data collected during the first 5 years of the program, 

since collection of SPS data was just getting underway. 

The results were published in five volumes.2 The fifth 

volume, Lessons Learned and Recommendations for 

Future Analyses,3 was notable in its identification of 

problems and deficiencies of the LTPP database and 

changes that would improve its utility for future 

researchers. The report identified procedures for 

developing predictive models and proposed procedures for evaluating design methods. The SHRP P-020 

studies laid the foundation for later analyses using 

LTPP data.

© 2015, Shutterstock.com
Pavement Maintenance Studies—SHRP-H-106 Reports

The SHRP H-106 project, Innovative Materials Development and Testing,1991–93, was designed to evaluate

the cost-effectiveness of pavement maintenance materials and procedures in the most extensive pavement 

surface maintenance experiment that had ever been 

conducted. The experiment studied the performance 

of unique combinations of materials and treatment 

methods for pothole repair (eight test sites, 1,250 potholes) and transverse and longitudinal crack sealing 

and filling (22,000 ft [6,700 m]) in asphalt concrete

(AC) pavements and for joint resealing (1,600 joints)

and partial-depth repair (four test sites, 1,600 partialdepth repairs) in Portland cement concrete (PCC) 

pavements. The study sites were distributed through 

the program’s four climatic regions, and the performance of the maintenance treatments was evaluated 

18 months after the repairs were made. SHRP H-106

generated comprehensive reports and manuals of 

practice for each of the maintenance activities.4,5,6,7 

When the SHRP program concluded, the LTPP program under the Federal Highway Administration 

(FHWA) continued annual evaluations of the test sites 

between August 1993 and December 1997 through its

Long-Term Monitoring of Pavement Maintenance 

Materials Test Sites study. At the end of the study, the 

LTPP program published extensive reports on PCC 

partial-depth spall repair,8 joint resealing,9,10 crack 

treatment,11 and pothole repair.12 In 1998, a 5-year data

analysis review of the maintenance of SPS-313 and -414

was published, followed by an update of the original 

four SHRP Manuals of Practice in 1999 with information collected during the continued monitoring, as

described in the LTPP Products section.15

FHWA Broad Agency Announcement

After the LTPP program transitioned from SHRP to 

FHWA, a series of LTPP data analysis contracts were 

funded under a Broad Agency Announcement (BAA). 

The BAA was issued before the development of the 

Strategic Plan for LTPP Data Analysis, discussed below, 

and the majority of the work was performed between 

1994 and 1996. Examples of projects completed under

the BAA include the following:

•	 Design and Construction of PCC Pavements. The 

study focused on the development of practical recommendations that could be implemented by highway agencies to increase pavement life.16,17,18

•	 Temperature Predictions and Adjustment Factors for 

Asphalt Pavement. An analysis of data from 40 sites 

in the Seasonal Monitoring Program (SMP), this 

study led to the practical LTPP Guide to Asphalt 

Temperature Prediction and Correction, with a 

spreadsheet for use in implementation of the methods recommended.19,20

•	 Rehabilitation Performance Trends. The earliest indepth look at the SPS rehabilitation experiments, 

this study examined performance data from SPS-5 

(rehabilitation of AC pavements), SPS-6 (rehabilitation of jointed PCC pavements), and SPS-7 (bonded

PCC overlay on PCC pavements).21

•	 Rutting Trends in Hot-Mix Asphalt Pavements. Based 

ondata from575GPS sites,this study foundthatpavements with high levels of rutting on average were constructed of asphalt mixes containing more fine 

aggregates than recommended by the Superpave® 

aggregate specifications; that hot weather, thin pavements, soft asphalts, and wet or low-density bases or 

subgrades also contribute to rutting; and that properly 

designed and constructed asphalt pavements can 

serve for 20 years or more without excessive rutting.22

Following the BAA, FHWA began to use an umbrella 

data analysis contract or data analysis IDIQ—indefinite delivery/indefinite quantity—contract for most 

LTPP data analysis activities.

Strategic Plan for LTPP Data Analysis: 

The “Tablecloth”

With such a wide array of potential analysis efforts, the 

LTPP program recognized the need to develop a strategic plan for LTPP data analysis. Led by the Transportation Research Board (TRB) Expert Task Group (ETG) on 

LTPP Data Analysis and the program office, this focused 

effortinthe late 1990sbenefitedfromtheparticipationof

subject matter experts across the pavement spectrum.23

The LTPP Data Analysis ETG took on responsibility for 

developing a strategic plan using LTPP data “to develop 

knowledge, relationships, and models to facilitate 

improved pavement design and reliable performance 

predictions.”24 Soliciting input from academic, industry, 

agency, and other pavement experts, the ETG identified 

10: Turning LTPP Data INTOESU
192 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

a wide array of analysis topics and outcomes. Through a 

series of meetings and other interactions, these items 

were organized into seven strategic objectives:

1.	 Improve traffic characterization and prediction.

2. Improve materials characterization.

3.	 Improve consideration of environmental effects in

pavement design and performance prediction.

4. Improve evaluation and use of pavement condition 

data in pavement management.

5. Evaluate existing and develop new pavement response and performance models applicable to pavement design and performance prediction.

6.	 Provide guidance for maintenance and rehabilitation strategy selection and performance prediction.

7.	 Quantify the performance impact of specific design

features (e.g., presence or absence of positive drainage, differing levels of pre-rehabilitation surface 

preparation).

Each of these objectives had multiple “product outcomes,” further grouping the analysis activities to 

ensure optimum return on investment.

Upon reaching consensus on the Strategic Plan, the 

LTPP Data Analysis ETG formally voted to implement 

it at its meeting on November 8–9,1999, and advocated

that all partners and participants adopt it as well. The 

original plan is shown in figure 10.1 and figure 10.2.The

LTPP program office assumed responsibility for maintaining the Strategic Plan, including periodically organizing in-depth reviews of the plan and its constituent 

problem statements. 

In September 2010, a LTPP Pavement Analysis

Forum was held in Irvine, California, where 50 pavement specialists from highway agencies, universities, 

and consulting firms met to review and refine targeted 

analytical outcomes under the Strategic Plan (see sidebar). The 3-day forum was a joint effort of the LTPP

program office and FHWA management, along with 

the TRB LTPP Committee.25 The group developed 122

analysis outcomes, project definitions, or research 

LTPP Pavement Analysis Forum Participants at TRB Beckman Center in Irvine, CA, September 2010. Front Row (left to right): 

Larry Wiser, Ahmad Ardani, David Orr, Susan Tighe, Eric Weaver, Judith Corley-Lay, Steve Jessberger, Mike Heitzman, 

Shie-Shin Wu, Tahar El-Korchi, Nadarajah Sivaneswaran, Gil Baladi, Newt Jackson. Second Row: Jane Jiang, Amelia Mathis, 

Deborah Walker, Wes Yang, Olga Selezneva, Julie Vandenbossche, Bob Lytton, Lynne Irwin, Jerry Hajek, Cheryl Richter,

Neil Hawks, Danny Dawood, Ralph Haas, Tom Yu, Amir Hanna, Andy Johnson, Ray Moore, Rick Reel, Karim Chatti, Robert Raab, 

Becky McDaniel, Jon Epps, Tom Baker, Luis Rodriguez. Third Row: Gary Elkins, Kevin Senn, Brian Schleppi, Andy Mergenmeier, 

Shelley Stoffels, Jonathan Groeger, Jack Springer, Ben Worel, Charlie Churilla, Mark Gardner, Aramis López, Tom White, 

Frank Meyer, John Donahue. Not in the picture: Mike Ayers. Absent: Carl Monismith.
Figure 10.1. Introduction to the original LTPP Strategic Plan for Long-Term Pavement Performance Da

Analysis, page 1, as adopted in 1999.

10: Turning LTPP Data INTOESU
194 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Over the years, many projects have addressed areas 

within the Strategic Plan. The LTPP program supported 

some of these projects, while others were supported by 

non-LTPP funds from FHWA or through the National 

Cooperative Highway Research Program (NCHRP) 

(see table 4.2, LTPP Timeline—Highway legislated and 

other funding sources). The following sections present 

examples of NCHRP- and FHWA-funded analysis 

research; however, for a complete view of progress 

in LTPP data analysis—studies planned, completed, 

and underway—refer to the Strategic Plan for LTPP 

Data Analysis.

LTPP Analysis Research Funded by NCHRP

In 1999 and 2000, a series of LTPP data analysis projects were awarded and administered through NCHRP 

under Research Field 20—Special Projects. These projects, which have all been completed (results available 

online), are listed in table 10.1.

problem statements, which were provided to the TRB 

LTPP Committee for review and recommendation for 

implementation in future years.26,27 

During the pavement analysis forum, the Strategic 

Plan was expanded with the addition of two new strategic objectives:

8.	 Analyses Supporting and Enhancing the Use of the

MEPDG.

9.	 Comprehensive Use of LTPP to Improve the Management of Pavement Assets.

The plan is a living document, and has been revised and 

updated regularly since its adoption to show the status 

of analysis projects.28 Owing to the paper size required 

to legibly print the document on a single sheet of paper, 

the strategic data analysis plan was nicknamed the LTPP 

data analysis “tablecloth.” Figure 10.3 displays the plan,

illustrating its size. Figure 10.4 and figure 10.5 show plan

detail for Strategic Objectives 1 and 6.

Figure 10.2. Graphical compilation of the 1999 LTPP Strategic Plan for Long-Term Pavement Performance D

Analysis, its strategic objectives and product priorities. 
Figure 10.3. Illustration of the expand

strategic plan for LTPP data analysis showing the 

extent and complexity of the plan as it has 

evolved since 1999 (October 30, 2014)

10: Turning LTPP Data INTOESU
196 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

FIGURE 10.4. Excerpt of the expanded strategic plan for LTPP data analysis, showing analysis outcomes, supporting 

projects, and problem statements for Strategic Objective 1: Traffic Characterization and Prediction (October 30, 2014).

Strategic Objective 1: Traffic Characterization and Prediction.

A. Guidelines for data collection (hardware, software, placement, calibration, data collection frequency). Some elements require work beyond LTPP 

data analysis, but analysis is needed to provide some components. 

B. Guidelines for using traffic data in pavement applications.

C. Procedures for forecasting and backcasting traffic loading data.

FHWA $249,977

Verification, Refinement, and Applicability of LTPP Classification Scheme.

Report pending Sept. 30, 2009 to Dec. 31, 2012

ARA, Inc. Selezneva/Walker

Problem Statement Number 1B2

Evaluation of Lane and Directional Changes of Traffic Loading Over Time.

12 months $150,000

FHWA 

LTPP WIM Approach Smoothness Specifications.

AASHTO MP-14 Nov. 2005

MACTEC UMTRI/Wiser

FHWA $258,409

Development of New Default Traffic Datasets for the MEPDG Using the 

SPS Traffic Data Collection Pooled Fund Study Data.

Report pending Sept. 30, 2009 to May 30, 2012

ARA, Inc. Selezneva/Walker

FHWA $293,000

Estimating Cumulative Traffic Loads, Phase 2.

FHWA-RD-03-094 Oct. 31, 1999 to Dec. 20, 2002

Eres Consultants, Inc. Hajek/Wiser

Problem Statement Number 1A2

Validate Vehicle Simulation Model and Provide Recommendations for Improved WIM Site Selection and Calibration.

36 months $750,000

Problem Statement Number 1A5

Collecting Data From Static Scales.

12 months $75,000

NCHRP 1-39 $500,000

Traffic Data Collection, Analysis, and Forecasting for Mechanistic Pavement Design.

Reports 509 and 538 Aug. 30, 2000 to July 30, 2004 

Cambridge Systematics Weinblatt/Hanna

FHWA $266,058

Optimization of Traffic Data Collection for Specific Pavement Applications.

FHWA-HRT-05-079 Jan. 23, 2003 to Aug. 15, 2005

(Coordinated with NCHRP 1-39) Papagiannakis/Wiser 

FHWA $250,000

Estimating Cumulative Traffic Loads, Phase 1.

FHWA-RD-00-054 Oct. 15, 1998 to Sept. 30, 2001 

Eres Consultants, Inc. Hajek/Wiser

Problem Statement Number 1A1

Evaluation of WIM Site Data and Tools to Improve Load Data Collection.

24 months $300,000

Problem Statement Number 1B3

Guidance to Facilitate the Analyst’s Use of the LTPP Traffic Data.

24 months $350,000

Problem Statement Number 1A4

Adding Axle Groupings Beyond Quad Tire Groups to LTPP Database.

1 to 2 months $30,000

FHWA FALCON 4.012

Refinement of Pavement Smoothness Requirements for WIM Systems.

AASHTO MP14-12 Oct. 1, 2009 to Aug. 1, 2012

ProVAL; Optimal WIM Locator (OWL)

Problem Statement Number 1B1

Effect of Traffic Data Quality and Quantity on the Outputs of the MEPDG.

24 months $350,000

Problem Statement Number 1C1

Modeling and Predicting Truck Loading Patterns for Pavement Design.

TBD TBD

Problem Statement Number 1A3

Truck Tire Wander, Pressure, and Width Data Collection.

12 to 18 months $150,000

Problem Statement Number 1A6

Innovative Cost-Effective Alternatives to Traditional WIM Calibration.

12 months $200,000

C 1 C 2

VH 3

Sequence numbers denote the order 

in which analysis outcomes should 

be addressed for a given objective. 

Analysis outcomes with the same 

sequence number can be addressed 

at the same time.

Note: 1) Problem statements are 

assigned a three-character number 

using the convention ‘O_A_n’. 

‘O’ is the associated strategic 

objective number (1 through 7); 

‘A’ is the associated analysis 

outcome letter (A, B, C, etc.); and 

‘n’ is an arbitrarily assigned number 

used for identification purposes. 

The number ‘n’ does not imply 

a sequence in which problem 

statements should be addressed. 

Boxes are ongoing NCHRP projects that were 

initiated by the LTPP ETG. Solid light blue 

boxes are completed projects.

Boxes are planned FHWA projects or 

data studies that will be funded using 

LTPP budgeted funds.

Boxes are ongoing NCHRP projects that were 

initiated by other agencies or work groups, but 

are directly associated with LTPP data analysis 

plan strategic objectives and analysis outcomes. 

Solid pink boxes are completed projects.

Boxes are ongoing FHWA projects that 

were funded using LTPP budgeted funds.

Boxes are completed projects with 

reports pending.

Boxes are completed projects with 

reports published. Boxes are proposed research problem statements 

that were developed at LTPP workshops. See 

Note 1) for an explanation of the problem 

statement numbering scheme.

Priorities

Critical

Very High

High

Sequence 1 2 3
10: TURNING LTPP DATA INTO RESULTS 197

FIGURE 10.5. Excerpt of the expanded strategic plan for LTPP data analysis, showing analysis outcomes, supporting 

projects, and problem statements for Strategic Objective 6: Maintenance and Rehabilitation Strategy Selection and 

Performance Prediction (October 30, 2014). Refer to the legend in figure 10.4 for further explanation.

Strategic Objective 6: Maintenance and Rehabilitation Strategy Selection and Performance Prediction.

A. Up-to-date LTPP maintenance and rehabilitation data validated for 

analysis use.

B. Efficacy and performance prediction for pavement maintenance 

and rehabilitation options.

C. Guidelines for optimal timing of pavement maintenance and 

rehabilitation treatments.

D. Selection of timely and effective maintenance and rehabilitation 

activities.

FHWA $54,000

LTPP Maintenance and Rehabilitation Data Review.

FHWA-RD-01-019 July 1999 to Apr. 2000 

Fugro-BRE Von Quintus/Richter

Problem Statement Number 6B1

Performance Efficacy and Characterization of the Series of Pavement Maintenance/Preservation and Rehabilitation Activities Needed Over the Life of a 

Pavement System.

24 months $500,000

Problem Statement Number 6C2

Development of Cost-Effective Combinations of Scheduled M&R 

Treatments Over Long-Life Pavement Design Periods.

24 months $375,000

Problem Statement Number 6D2

Cost Effectiveness of Maintenance and Rehabilitation Design Features.

18 months $150,000

FHWA $54,000

Performance of Rehabilitated AC Pavements in the LTPP Experiments.

FHWA-RD-00-029 Oct. 1, 1997 to Aug. 1, 1999 

Fugro-BRE Rauhut/Richter

NCHRP 14-14 $312,397

Guide for Optimal Timing of Pavement Preventive Maintenance Treatment 

Applications. 

Report 523 Apr. 10, 2000 to Sept. 30, 2003 

Applied Pavement Tech. Peshkin/Hanna

Problem Statement Number 6A2

Determination of LTPP Experiment Maturity for Analysis in Maintenance 

and Rehabilitation and Other Strategic Objective Analytical Projects.

18 months $180,000

NCHRP 20-50(3/4) $250,000

Effectiveness of Maintenance and Rehabilitation Options.

Web Document 47 Oct. 14, 1999 to Mar. 31, 2002 

Kathleen Hall Hall/Hanna

NCHRP 1-38 $100,000

Guide on Pavement Rehabilitation Strategies.

Web Document 35 Mar. 1, 1999 to Mar. 31, 2001 

Kathleen Hall Hanna

NCHRP 9-40 $428,000

Optimization of Tack Coat for HMA Placement.

NCHRP Report 712 Jul. 1, 2005 to Dec. 31, 2011

Louisiana Transportation Rsrch. Ctr. Louay/Harrigan

Problem Statement Number 6A1

Review and Validation of LTPP Maintenance and Rehabilitation Data.

12 months $100,000

FHHA $25,433

Assessment of the SPS-7 Bonded Concrete Overlays Experiment.

FHWA-RD-98-130 July 1, 1999 to Dec. 1. 2000

Eres Consultants, Inc. Smith/Richter

FHWA $415,197

Pavement Performance Measures and Forecasting, and the Effects of 

Maintenance & Rehabilitation Strategy on Treatment Effectiveness.

Report Pending Sept. 30, 2013 to Mar. 31, 2016 

Michigan State University Baladi/Jiang

Problem Statement Number 6C1

Followup of NCHRP to 14-14 Research With Emphasis on Quantitative 

Analysis of Enlarged LTPP M&R Database and Supplemental M&R Data 

From SHAs and Others.

18 months $250,000

Problem Statement Number 6D1

Determine the Effect of Repair Techniques on the Performance of Subsequent HMA Overlays.

24 months $250,000

Problem Statement Number 6C3

Development of Optimal Distress Threshold Triggers for Unscheduled 

Rehabilitation Treatments.

18 months $250,000

Problem Statement Number 6D3

Selection of Optimal Rehabilitation Techniques for Existing Conditions.

24 months $200,000

Problem Statement Number 6D4

Methodology to Enable Development of Long-Term Rehabilitation and 

Maintenance Schedules.

36 months $750,000

C

C

H

H

1

2

1

2
198 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

LTPP Analysis Research Funded by FHWA 

(Non-LTPP Funds)

Several research efforts sponsored or conducted by 

FHWA appear in the Products or Benefits section later 

in this chapter. Following is a sampling of specific studies undertaken in recent years.

•	 LTPP Computed Parameter: Moisture Content (2005–

2007). This project completed the interpretation of 

LTPP time domain reflectometry measurements 

and provided estimates of moisture contents from 

these measurements in the LTPP database in January 2008 on Standard Data Release 22.

37

•	 LTPP Computed Parameter: Frost Penetration (2005–

2007). With the completion of monitoring measurements on the SMP sections in October 2004, this 

project completed the interpretation of measurements not previously interpreted and added the results of these interpretations to the database.38

•	 LTPP Computed Parameter: Dynamic Modulus 

(2007–2009). The primary objective of this study 

was to develop estimates of the dynamic modulus 

of hot-mix asphalt (HMA) layers on LTPP test sections following the models used in the NCHRP 

Guide for MEPDG for storage in the LTPP database. A software tool was developed as part of 

this project.39

•	 Estimation of Key Portland Cement Concrete, Base, 

Subbase, and Component Engineering Properties 

From Routine Tests and Physical Characteristics 

(2007–2009). The results of this project enable 

pavement design and materials engineers to make 

well-founded decisions about materials and materials specifications to be used in pavement construction. Potential cost savings resulting from better 

materials selection, fewer premature pavement failures, and avoidance of overdesign are significant. 

The project report was published together with a 

user’s guide that summarizes the models developed, 

describes their application for specific project conditions, and lists their limitations.40,41

•	 Impact of Design Features on Pavement Response 

and Performance in Rehabilitated Flexible and Rigid 

Pavements (2007–2009). With new data available in 

the LTPP database, it was necessary to obtain a 

better understanding of the effects of design and 

construction features on pavement response and 

performance of rehabilitated flexible and rigid 

pavements. Published in 2011, this research provides preliminary information on the relationship 

between pavement response and performance, 

guidance for identifying appropriate features for 

different pavement types, and recommendations for 

improving data collection activities.42 

Table 10.1. LTPP data analysis research funded by the National Cooperative Highway Research Prog

Project Number(s) Titl

NCHRP 20-50(10&16) LTPP Data Analysis: Influence of Design and Construction Features on the Response and

Performance of New Flexible and Rigid Pavements29

NCHRP 20-50(10) LTPP Data Analysis: Factors Affecting the Performance of Flexible and Rigid Pavements (folded 

into NCHRP 20-50(10&16))

NCHRP 20-50(14) LTPP Data Analysis: Significance of “As-Constructed” AC Air Voids to Pavement Performance30

NCHRP 20-50(2) LTPP Data Analysis: Relative Performance of Jointed Plain Concrete Pavements With Sealed and 

Unsealed Joints3

NCHRP 20-50(3&4) LTPP Data Analysis: Effectiveness of Maintenance and Rehabilitation Options, 200232

NCHRP 20-50(5) LTPP Data Analysis: Variations in Pavement Design Inputs3

NCHRP 20-50(7&12) LTPP Data Analysis: Daily and Seasonal Variations in Insitu Material Properties3

NCHRP 20-50(8&13) LTPP Data Analysis: Factors Affecting Pavement Smoothness35

NCHRP 20-50(9) LTPP Data Analysis: Feasibility of Using FWD Deflection Data to Characterize Pavement

Construction Quality36
Fulfilling the LTPP Strategic Plan

Completing the research projects in the Strategic Plan 

for LTPP Data Analysis will require continued funding. 

Since the conception of the data analysis plan, a total of 

211 projects have been identified (table 10.2). Although

scores of analysis projects defined in the plan have been 

completed, more than 100 defined research projects

remain to be performed, and new research needs will 

arise in the future. Some analysis projects are not ready 

for development of research problem statements because 

other underlying research has not been performed, or 

more data are needed. It is also recommended that many 

earlier findings derived from LTPP data be re-evaluated 

to determine if the short-term trends were correct. The 

additional data collection performed since early studies 

were finished (e.g., Effectiveness of Maintenance and 

Rehabilitation Options, completed in 199943) warrant 

consideration of follow-up investigations.

The TRB LTPP Committee continues to monitor 

the status of LTPP analysis projects and provide technical advice and assistance to FHWA concerning 

future direction of the projects. For example, in its 2011

letter report to FHWA and AASHTO, the Committee 

listed 22 analysis projects they considered to be of 

highest priority for early starts.44 

To continue the LTPP analysis research, FHWA 

issued a second BAA in June 2013, with the purpose of

providing sponsorship for a series of research projects 

involving innovative analysis of data obtained through 

the LTPP program to better understand pavement performance. As stated in the BAA, the projects that comprise the LTPP data analysis program serve two broad 

functions that must be addressed if LTPP is to fulfill 

expectations: (1) the projects provide the basis for

identifying and developing products that engineers 

and managers can apply to design more cost-effective 

and better performing pavements; and (2) the projects 

check whether the data being collected are of the quality and completeness needed to answer questions 

about how and why pavements perform as they do.

LTPP Data Studies

While the “tablecloth” is the guiding document for 

most centralized LTPP data analysis activities, a number of additional investigations have been performed 

internally by the LTPP program office and LTPP contractor staff to improve the program’s overall operation. 

One such example is the study of variability between 

distress raters (discussed in chapter 9).45,46 Using data 

from nine LTPP distress accreditation workshops, 

analyses regarding rater-to-rater variation were completed. It was found that significant variability was 

observed from one rater to the next, particularly with 

regard to severity levels for individual distresses, 

and that variability increased as distress quantities 

increased. Due to this study, the program implemented 

changes including adding time-series reviews and 

enhancing rater training activities.

Highway Agency Studies

Many State and Provincial highway agencies have 

performed analyses using LTPP data and have developed their own research programs incorporating 

LTPP standards as a basis for data acquisition and 

processing. The following pages describe a sample of 

these analyses.

Table 10.2. Status of research studies related to the Strategic Plan for LTPP Data Analysis (1999–201

    Unaddressed Pro

Research Vehicle Studies Completed Studies Ongoing Studies Planned Statements Remainin

FHWA-LTPP Data Analysis 50 7 13 

Contracts (using LTPP 

budgeted funds)

National Cooperative Highway 26 11 0 

Research Program

Total 76 18 13 104

10: Turning LTPP Data INTORES
200 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Arizona SPS Analysis

Recognizing that much could be learned by analyzing the performance of the LTPP experiments within 

their own agency, the Arizona Department of Transportation (DOT) sponsored analyses of their SPS 

projects. These efforts were specifically targeted at 

evaluating pavement performance and determining 

“lessons learned.” Specific focus was given to the distress, longitudinal profile, and falling weight deflectometer (FWD) data sets. Distresses were grouped by 

failure mechanism (i.e., traffic/load-related and climate/materials-related) into structural and environmental damage indices, and these indices were 

tracked over time. Similarly, time-series investigations were made on deflection data to examine reductions in layer moduli and effective structural number, 

and on longitudinal profile data to track changes in 

International Roughness Index (IRI) values, power 

spectral density, roughness profiles, and filtered 

profiles (for short, medium, and long wavelengths) 

over time. 

Cross correlations were also examined to study, for 

example, the impact of distress propagation on longitudinal profiles. One lesson learned was that roughness and roughness progression alone cannot be used 

to represent the health of a test section. Many test 

sections did not exhibit changes in roughness in proportion to the amount of fatigue cracking experienced, and sections that had clearly reached the end 

of their service lives did not necessarily have roughness values that would trigger a rehabilitation event. 

Arizona DOT, through the Arizona Transportation 

Research Center, is publishing these reports for their 

SPS-1 (structural factors for flexible pavements),47 -2 

(structural factors for rigid pavements), -5 (rehabilitation of AC pavements), -6 (rehabilitation of jointed

PCC pavements), and -9 (Superpave) projects.

Colorado LTPP Implementation

Like Arizona, the Colorado DOT (CDOT) recognized 

that improvements to internal processes could be 

made by analyzing their LTPP test sections. CDOT was 

proactive in examining their SPS-2 (structural factors 

for rigid pavements) and SPS-4 (preventive maintenance of flexible pavements) projects, starting with the 

construction practices. In the case of the SPS-2 experiment, a follow-up study found that using a 14-ft(4.3-m)

slab width instead of a 12-ft (3.7-m) width was equivalent to adding 1inch (25.4 mm) of slab thickness. Based

on this finding, CDOT adopted the 14-ft slab in 1996

based on the results of the LTPP SPS-2 experiment, 

and continues to follow this practice today.48,49

Before constructing the Colorado SPS-4 project, 

CDOT used a standard double cut for 3/8-inch (9.5-

mm) joints. In building the SPS-4, CDOT learned that 

a single-cut, 1/8-inch (3.2-mm) joint was equally

effective, while being less labor-intensive and requiring less sealant material. A cost-benefit analysis was 

performed, and it determined that going to the singlecut standard resulted in a savings of 57 cents per linear foot of joint, which equated to almost $1.7 million

in savings for 100 mi (161 km) of two-lane concrete

pavement.50 

Kansas Binder Selection

When implementing the Superpave performance 

grade binder specifications, the Kansas DOT (KDOT) 

turned to a popular LTPP product to optimize binder 

selection: LTPPBind. KDOT uses the software as an 

integral part of their pavement design process. KDOT 

pavement designers use LTPPBind to determine the 

performance grades at the various depths of the pavement structure and for different traffic conditions. 

The software incorporates actual site temperatures, 

providing an improvement to the temperature information in the original SHRPBind software. In many 

instances, KDOT found that LTPPBind changed the 

binder grade, which provided improved pavement 

performance.51 

MnROAD

Constructed near Albertville, Minnesota, in 1994, the

MnROAD facility (figure 10.6) was designed to study

cold weather pavement design, materials, and performance for both low-volume and interstate test sections. Primarily funded by the Minnesota DOT and the 

Minnesota Local Road Research Board, MnROAD 

activities have also been supported by industry, public-, 

and private-sector organizations at the State, national, 

and international levels.
The LTPP program and MnROAD staff work 

closely together, and many LTPP data collection 

activities have taken place on MnROAD sections, 

including manual and automated distress surveys 

(MnROAD uses a modified LTPP manual distress 

process), longitudinal and transverse profile measurement, and FWD testing. MnROAD has LTPP-like 

seasonal monitoring data, and once housed an onsite 

FWD calibration center. There are 11 LTPP test sections located at the MnROAD facility of which three 

remain active today. 

MnROAD has gone through two phases since it 

opened to traffic in 1994. As the first set of MnROAD

studies was nearing completion, a second phase of 

research was begun that largely involved reconstructing many of the original test sections. Phase 2 activities 

are guided by the Transportation Engineering and 

Road Research Alliance (a research governance structure formed in 2004), and construction/reconstruction activities are nearing completion. Phase 3 will

begin in 2016 with a focus on maintenance and rehabilitation. It is very possible that the LTPP test sections 

will be used during this phase. 

Among key findings from the first generation of 

MnROAD studies were revised spring load restriction 

and winter load increase policies, improved low temFigure 10.6. MnROAD low-volume road and mainline test roadways owned and operated by the Minnesota Departm

of Transportation (2003). 

10: Turning LTPP Data INTOESU

©Minnesota Department of Transportation
202 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

perature cracking resistance and pavement sealing 

practices, and mechanistic-empirical design methods 

for concrete and flexible pavements. These results save 

Minnesota $33 million annually.

New Jersey Seasonal Monitoring Program

As part of its preparations to implement the MEPDG, 

the New Jersey DOT initiated a seasonal variation and 

material characterization study in 2001. Twenty-four

test sections across the State were instrumented following LTPP SMP protocols. FWD and seismic testing 

were performed monthly over a 2-year period to supplement the continuous climatic data collection and 

to investigate the impact of environmental parameters 

on pavement response. Through regression analyses, 

temperature and seasonal correction factors were 

developed specific to New Jersey conditions.52 

New Jersey IRI Models for Pavement 

Management System

The New Jersey DOT has also used LTPP data to verify 

and refine models that are used in its pavement management system to determine when a pavement is in 

need of repair. The State’s system had a default IRI 

performance model that triggered rehabilitation at 

170 inch/mile (0.0027 m/km) or 9 years. To validate

these criteria, the State accessed the data from its 

SPS-5 (rehabilitation of AC pavements) and SPS-9A

(Superpave) test sites using DataPave Online. The 

results predicted pavement life as long as 20 years 

before an IRI of 170 inch/mile would be reached and

any type of treatment would be required. Neither New 

Jersey’s data set (using some of the State’s 1999 construction projects) nor data from DataPave Online 

(using LTPP SPS test sites) ever reached the trigger IRI 

value of 170 inch/mile. Access to LTPP data allowed

New Jersey to develop realistic IRI prediction models.53

Pennsylvania Joint Design

The Pennsylvania DOT (PennDOT) has a pavement 

network with over 3,200 mi (5,150 km) of PCC pavements. Based on LTPP pavement performance data, 

PennDOT modified its PCC joint designs from using 

skewed joints to constructing perpendicular joints. 

Multiple benefits were realized with this modification, 

including reduced construction and maintenance 

costs, fewer maintenance-related disruptions to traffic, 

and a smoother ride for motorists.54 

Texas SMERP—Supplemental Maintenance 

Effectiveness Research Program 

The SMERP study was designed to “establish the effectiveness of typical and promising maintenance treatments used in Texas to prolong the life of asphalt 

pavements.”55 The Texas DOT (TxDOT) allocated 

$1 millionto build test sections of preventive treatments

that were of interest to Texas but were not being studied in the SHRP-LTPP national experiment. By analyzing the data from the LTPP SPS-3 experiment

(preventive maintenance for flexible pavements), with 

16 sites inTexas, andthe SMERPstudies,TxDOThoped

to identify the best treatment selection strategies and 

get the best return on its preventive maintenance funds. 

In designing the experiment, TxDOT followed the basic 

design of the LTPP SPS-3 experiment and used an

ASCII data format that would be compatible with output from the LTPP database so that SMERP and LTPP 

data could be combined for analysis. In 1993, at each of

20 test locations throughout the State, six treatment 

sections and a control section were established: asphalt 

rubber chip seal, polymer-modified emulsion chip seal, 

latex-modified asphalt cement chip seal, unmodified 

asphalt cement chip seal, fog seal, and a microsurfacing 

treatment (two sites did not have a fog seal or control 

section).56 The sites were inspected at 6 months and

annually for 8 years, with nine sections surviving the

full 8 years. The SMERP study resulted in treatment

selection recommendations for TxDOT districts that 

were based on actual performance data. An important 

finding was that the pre-treatment condition of a pavement is a major determinant of a treatment’s effectiveness when deterioration is measured over time.57,58,59 

Texas Evaluation of LTPP Data and Implementation of 

the Texas Transportation Institute Overlay Tester

Performance data from LTPP test sections were used by 

TxDOT to develop its performance prediction models 

for the Texas mechanistic-empirical flexible pavement 

design system. The proposed rutting model for HMA 

pavements was calibrated using rutting and traffic data 

from the Texas LTPP SPS-5 (rehabilitation of AC pavements) test sections and the National Center for Asphalt 
Technology Pavement Test Track. Predicted rutting was 

compared with measured rutting in the LTPP database. 

In investigations of the use of the Overlay Tester in predicting fatigue cracking in HMA pavements, LTPP data 

were used to develop and calibrate the transfer function 

in calculating the amount of fatigue cracking.60,61 

The Texas Flexible Pavements Database

TxDOT used the LTPP database as an example to 

design its Texas Flexible Pavements Database.62 This 

database is being used to develop guidelines for local 

calibration of the MEPDG. A 5-year project was initiated to collect materials and pavement performance 

data on a minimum of100highway test sections around

the State, incorporating both flexible pavements and 

overlays. Besides being used to calibrate and validate 

mechanistic-empirical design models, the data collected will also serve as an ongoing referencedata source 

and diagnostic tool for TxDOT engineers and other 

transportation professionals. 

The Mechanistic-Empirical Pavement 

Design Guide

Externalto the LTPP program, NCHRP Project1-37(A),

Development of the 2002 Guide for the Design of New 

and Rehabilitated Pavement Structures,63 was initiated 

to develop a replacement for the 1993 AASHTO Pavement Design Guide. Using increased computational 

speeds and improved understanding of key inputs (i.e., 

traffic loads, environment, and material properties), the 

project’s objective was to develop a more mechanisticbased design methodology. It soon became apparent to 

the project team that developing a mechanistic-empirical pavement design guide was going to require pavement data from coast to coast, and the LTPP database 

provided access to this critical information.

The LTPP database has contributed significantly to 

the enhancement of pavement evaluation and design 

through the development of the MEPDG and, later, 

the AASHTOWare® Pavement ME Design software 

developed to implement the MEPDG.64 It has been 

said that “without LTPP data for the national calibration, the MEPDG distress models could not have been 

validated for use throughout the country.” The distress and smoothness prediction models that are key 

to the MEPDG required calibration with measured 

long-term performance data that were available only 

from the LTPP database. The database is also serving 

as an extremely valuable tool in implementation of the 

new guide. For the guide to be efficient for individual 

agencies, the national models will need to be evaluated against local and regional performance data. The 

LTPP test section data provide a resource for highway 

agencies to use in determining whether local calibration is required.

TRB LTPP Data Analysis Working Gro

Twice each year the TRB Data Analysis Working 

Group (DAWG), sponsored by the TRB LTPP Committee, organizes an international forum on the analysis 

of pavement performance data in connection with a 

major highway pavement conference (appendix A).66

Researchers are invited to informally present their 

work in progress, usually concerning the development of techniques for extracting and analyzing data 

and the early results of applying these techniques. 

Typical topics are model building, sensitivity analysis, 

and development of transfer functions linking structural response to distress. These forums have provided 

a venue where researchers can benefit from the input 

of others who are engaged in pavement research, 

design, maintenance, and rehabilitation and are 

interested in collecting, processing, and analyzing 

data and in developing insights into pavement performance. The analysis of LTPP data has frequently 

been the subject of research presented at DAWG 

forums, which serve to support and promote LTPP 

data analysis.

10: Turning LTPP Data INTOESU

“Without LTPP data for the national 

calibration, the MEPDG distress models 

could not have been validated for use 

throughout the country. In addition, 

the LTPP data is invaluable to each 

State highway agency for its own local 

validation and calibration purposes.”

 —Michael Darter, Applied Research 

Associates, Inc.65
International Data Analysis Contest 

As a means to both further LTPP data analysis activities 

and introduce the next generation of pavement engineers to the LTPP database, FHWA and the American 

Society of Civil Engineers (ASCE) teamed up in 1998 to 

create the LTPP International Data Analysis Contest.67

The contest provides incentive for innovative use of 

LTPP data to solve common pavement engineering 

problems. Recently revamped, the contest offers general 

and challenge topics to contestants each year and has 

four entry categories (Challenge Topic, Partnership, 

Undergraduate Students, and Graduate Students). Winners are invited to present at the TRB Annual Meeting in 

Washington, DC, and winning papers are published by 

FHWA. The 2012 winner is pictured in figure 10.7.68

This successful competition has resulted in many 

universities implementing the LTPP data in their 

undergraduate and graduate curricula, and use of the 

LTPP data has expanded significantly since the contest 

began. The success of the contest has been due to the 

partnership between the LTPP program and ASCE and 

a great number of contributions through the years 

from ASCE’s Transportation and Development Institute’s Pavements Committee and its many members. 

Translating Analysis Results Into Products

As analyses are performed, whether by the LTPP program office, NCHRP, or highway agencies as discussed 

in the previous pages, the logical next step is to develop 

useful and usable highway engineering products from 

these analyses that help to explain how and why pavements perform as they do. The following section covers some of the key products that have been developed 

as a result of the program. 

LTPP PRODUCTS 

After the first few years of data collection, the LTPP program began work on developing products that could be 

used by highway agencies to improve their practices. 

Product development became a requirement in 1998 

under the Transportation Equity Act for the 21st Century (TEA-21). This act continued support of the program for 6 years with the following stipulation:

Under the program, the Secretary shall make grants and 

enter into cooperative agreements and contracts to (A) 

Monitor, material-test, and evaluate highway test sections 

in existence as of the date of the grant, agreement, or contract; (B) Analyze the data obtained in carrying out subparagraph (A); and (C) Prepare products to fulfill program 

objectives and meet future pavement technology needs.69

Development of the LTPP Product Plan

In the early days of the program, when data collection, 

processing, and quality control/quality assurance (QC/

QA) procedures were being established, many products were developed in support of LTPP operations. 

The program has played a major role in the development of pavement-related guidelines and standards 

FIGURE 10.7. Daniel Franta, a graduate student at the 

University of Minnesota, receives the 2012 ASCE-LTPP 

International Data Analysis Contest Winner award for his 

winning paper “Classification of Features of Pavement 

Profiles Using Empirical Mode.” Presenting the award is C. 

Michael Walton, then President of ASCE’s Transportation 

and Development Institute.

204 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The ASCE-LTPP International Data 

Analysis contest is designed to 

encourage student involvement in 

analyzing LTPP data. As a result of 

the contest, several universities 

are using the LTPP data as part 

of their pavement curricula.
throughout its history. A partial listing of these achievements includes: 

•	 Standardizing data collection and QC practices.

–	 Pavement distress.

–	 Automated profile.

–	 FWD.

•	 Developing equipment calibration procedures.

•	 Standardizing automatic vehicle classification (AVC)

and weigh-in-motion (WIM) data storage formats.

•	 DevelopingamethodologyforAVCandWIMdataQC.

•	 Developing a startup procedure for laboratory

equipment and standardized laboratory and field 

testing protocols.

LTPP product development was elevated to a higher level by the language of TEA-21. In response to this charge,

the program office with the support of FHWA management, requested that the TRB LTPP Committee evaluate 

five potential changes to the program:

•	 Establishment of an LTPP Product Subcommittee.

•	 Consideration of national pavement needs.

•	 Expansion of ETG responsibilities to address product development.

•	 Establishment of a new FHWA Product Development and Delivery Program.

•	 Development of an LTPP Product Plan.

The TRB LTPP Committee supported the LTPP Product 

Subcommittee recommendation and asked the subcommittee to assist in creating the LTPP Product Plan. This 

document was published in 2001(figure 10.8), and identified five “national pavement needs” on which product 

development activities would be focused:70

1.	 New and reconstructed pavements.

2. Maintenance and rehabilitation of pavements.

3.	 Pavement management system tools and techniques.

4. Traffic loading and environmental effects.

5. National pavement performance data services. 

To achieve a fully integrated plan, the Product Subcommittee related these national pavement needs to the 

objectives in the Strategic Plan for LTPP Data Analysis. 

Research knowledge and findings contained in analysis 

reports are not ready to use and are only building blocks 

for future products. The goal articulated in the product 

plan, however, is to develop and deliver products that 

meet the following definition: LTPP products are readyto-use guidelines, procedures, protocols, best practices, 

software, equipment, and other tools that are packaged 

for and delivered primarily to the management and 

technical staff in the highway agencies. It should be 

noted that a research report is not considered to be an 

LTPP product as defined in the plan.

As part of the LTPP Product Plan, FHWA’s Office of 

Pavement Technology was charged with coordinating 

product development activities both internally with the 

LTPP program office and externally with supporting 

organizations such as the AASHTO Research Advisory 

Committee, Standing Committee on Highways, Subcommittee on Materials, and the Joint Task Force on 

Pavements. Funding issues have impacted the products 

area severely, with reductions in FHWA Office of Pavement Technology staffing and in dedicated moneys for 

product development. Nevertheless, the LTPP program 

has made significant advances in product development. 

In some cases, highway agencies have contributed 

money through pooled-fund studies for these activities 

(see sidebar). The program has frequently polled customers from highway agencies, industry, and academia 

to determine the needs of potential data users. In particular, chief engineers from the highway agencies have 

played a key role in identifying products needed to 

address national pavement needs. 

LTPP products have benefited the pavement community by improving existing practices and providing 

tools to improve decisionmaking. Some of these products are described in the following sections. Although 

the listed products were developed both before and 

after the LTPP Product Plan was created, the prodLTPP products are ready-to-use 

guidelines, procedures, protocols, 

best practices, software, and equipment 

that are packaged for and delivered 

primarily to the management and 

technical staff in the highway agencies.

10: Turning LTPP Data INTOESU
Figure 10.8. LTPP Product table from the 2001 LTPP Product Plan showing how existing and planned LTPP 

products address national pavement needs.

206 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
The LTPP program and NCHRP were not the only 

sponsors of projects developing LTPP-related benefits. The transportation pooled-fund program is a way 

for FHWA, States, and other organizations to partner 

when significant or widespread interest is shown in 

solving transportation-related problems.72 Under this 

arrangement, the partners pool funds and other 

resources to solve problems through research, planning, and technology transfer activities. The quality 

and accessibility of LTPP data lends itself to supporting a wide range of pavement-related activities as in 

the pooled-fund studies named below. 

• Effect of Multiple Freeze-Thaw Versus Deep 

Frost Penetration on Pavement Performance, 

TPF-5(013). 

• Falling Weight Deflectometer (FWD) Calibration 

Center and Operational Improvements, 

TPF-5(039). 

• Long-Term Pavement Performance (LTPP) 

Specific Pavement Study (SPS) Traffic Data 

Collection, TPF-5(004). 

• Improving the Quality of Profiler Measurement, 

TPF-5 (063).

These are studies in which the LTPP program led 

the effort, but many other projects completed at 

the local, State/Province, and national levels have 

used LTPP data for the benefit of other operations 

and the pavement community as a whole.

ucts discussion is organized around the national 

needs and the goals included in the product plan. In 

addition, the objectives from the Strategic Plan for 

Data Analysis are listed for each national need. More 

products are listed in figure 10.8 and in the LTPP Benefits Report.71

Nationl 

New and Reconstructed Pavement

Goal: Identify improved designs and design features wi

more accurate service predictions, tendencies, or trends.

• Objective 5: Development of pavement re

and performance models applicable to pavement 

design and performance prediction.

• Objective 7: Quantification of the perfo

impact of specific design features (presence or 

absence of positive drainage, differing levels of 

pre-rehabilitated surface preparation, etc.).

• Objective 8: Analyses supporting and enh

the use of the MEPDG.

To address the national need for improved design 

and construction of new and reconstructed pavements, the LTPP program has created software tools 

and test procedures. In addition, the pavement performance data played an important role in the development of the MEPDG as discussed above. This 

section covers a few of the LTPP products related to 

pavement design.

Rigid Pavement Design Software 1998 AASHTO 

Supplement

The LTPP Rigid Pavement Design software was 

developed to facilitate the application of the 1998 Supplement to the Guide for Design of Pavement Structures.73,74 The guidelines in this publication were 

developed based on studies conducted during NCHRP 

Project No. 1-30. The software automates the computations required to use the 1998 supplemental guidelines and includes separate tables for determining 

accumulated traffic loading, seasonally adjusted 

k-values, and depth to rigid layer, and for performing 

corner break and faulting checks. The magnitude of 

the cost savings from following the 1998 supplemental guidelines and using the software will vary with 

site conditions, with a 30 percent reduction being a

reasonable average.

LTPP Levera ges FHWA’s Transporta

10: Turning LTPP Data INTOESU
LTPPBind Software

Based on an analysis of the LTPP data and on the original binder selection software known as SHRPBind, 

LTPPBind is a Microsoft® Windows®-based program 

that can help highway agencies select the most suitable 

and cost-effective Superpave asphalt binder performance grade (PG) for a particular site. LTPPBind features a database of high and low air temperatures 

(minimum, mean, maximum, standard deviation, and 

number of years) for U.S. and Canadian weather stations, along with several modifications that provide 

users with the ability to (1) select PGs based on actual

temperature conditions at their site and at the level of 

risk designated by their highway agency; (2) use either 

the original temperature models developed by SHRP 

or LTPP’s revised temperature models for determining 

a site’s binder PG; and (3) adjust PG selection for different levels of traffic loading and speed.75

Resilient Modulus Test Procedures for Bound and 

Unbound Layers 

The LTPP program has made significant contributions 

in characterizing material properties by improving test 

protocols as well as in providing a database of properties that are linked to actual field performance—both of 

which have furthered the development and use of 

mechanistic approaches in pavement engineering. 

When establishing characteristics in the unbound 

layers—including subgrade, subbase, and base materials—resilient modulus is the property most relevant 

to pavement design. Consequently, establishing granular layer resilient modulus values has been a priority 

activity for the program. In the program’s early days, 

no concise test protocol existed for resilient modulus 

testing. This was observed when samples from the 

same location were tested (both in the same laboratory 

and in different laboratories) with wide variation in the 

test results.

To address variability in the laboratory equipment 

and procedures, the program developed the LTPP laboratory startup procedure. This comprehensive procedure was developed to test the ability of the equipment 

and personnel to perform resilient modulus testing.77

At the same time, the program made a considerable investment in establishing LTPP Test Protocol 

P46—Resilient Modulus of Unbound Materials.78

This protocol has been widely adopted,79 a process 

that was accelerated first by a series of videos and 

then by a CD-ROM containing the videos and additional documentation. 

Similar to its role in the development of Test Protocol P46, the LTPP program was responsible for developing a highly repeatable test protocol to determine 

asphalt resilient modulus—LTPP Protocol P07.80 The 

LTPP asphalt resilient modulus CD-ROM contains a 

15-minute video describing the startup and QCprocesses as well as a comprehensive package of information 

and data related to resilient modulus. The P46 and P07

CD-ROMs are available through the LTPP Customer 

Support Service Center (Email: ltppinfo@dot.gov).

|E*| Computation of LTPP Sites

An FHWA-funded project was undertaken using the 

LTPP database to compute estimates of the dynamic 

modulus of HMA layers on LTPP test sections. Dynamic modulus, |E*|, is a fundamental property of AC mixtures that characterizes strain response as a function of 

loading rate and temperature. |E*| is one of the primary 

material property inputs in AASHTOWare® Pavement 

ME Design software;81 it is one of the primary properties measured in the Asphalt Mixture Performance 

Test protocol that complements volumetric mix design 

with mechanical properties; and it is one of the fundamental linear viscoelastic material properties that can 

be used in advanced pavement response models based 

on viscoelasticity.

Engineers use LTPPBind to more 

accurately determine the asphalt binder 

(cement) grade needed for their specific 

environmental conditions. A national review 

of LTPPBind shows it helps highway agencies 

save at least $50 million in construction 

costs each year by reducing the need to 

apply modified binders, a factor that can 

drive up the costs of construction.76

208 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
In addition to populating the LTPP database with 

|E*| data, the project developed a user-friendly software, LTPP (known as LTPP Star), to facilitate |E*| 

computations (figure 10.9). The software can batch

process data from a file to compute large quantities of 

|E*| estimates in accordance with the model hierarchy. 

This software can be very useful for agencies that 

would like to estimate |E*| using legacy data sets or 

those limited to older test procedures,82 and it is available free on the LTPP InfoPaveTM Web site or from 

the LTPP Customer Support Service Center (Email: 

ltppinfo@dot.gov).

Researcher’s Guide to the Long-Term Pavement 

Performance Thickness Data

A byproduct of the LTPP-sponsored research, “Review 

of LTPP Layer Thickness Data” is the new guide, 

Researcher’s Guide to the Long-Term Pavement Performance Thickness Data, which helps database users 

understand the differences between (and, thus, appropriate uses of ) the layer thickness data found in different database tables.83

Nationl P

Maintenance and Rehabilitation of Pavements

Goal: Identify cost-effective methodologies a

strategies for the rehabilitation and maintenance of 

existing pavements.

• Objective 5: Development of pavement re

and performance models applicable to pavement 

design and performance prediction.

• Objective 6: Maintenance and rehabili

strategy selection and performance prediction.

Many highway pavement engineers and managers 

have asked the question, what type of treatment do I 

apply and when do I apply the treatment to extend the 

life of my pavements? These questions have been and 

continue to be major issues for highway agencies. 

Although there are no easy answers, the LTPP program has developed the following products to address 

these concerns.

Pavement Treatment Effectiveness

A national site evaluation conducted by the LTPP program on the preventive maintenance experiments after 

5 years of service yielded new understanding of the 

effectiveness and optimal timing of the treatments.84,85

The SPS-3 (structural factors for flexible pavements)

and -4 (structural factors for rigid pavements) experiments were constructed in 1990, and in 1995, early field

performance information was collected.

Crack sealing, slurry seals, chip seals, and thin hotmix overlays were evaluated in the SPS-3 analysis,86

and under sealing and joint sealing in SPS-4.87 The 

analyses considered three important characteristics of 

the preventive treatments: performance, timing of 

application, and cost-effectiveness.

The field review and evaluation of the SPS-3 and -4

test sections were valuable technology transfer tools, 

and involved a sharing of experiences among the 

highway agencies as part of the process. As a result, 

maintenance treatments are better understood 

throughout the industry, and improved materials and 

construction specifications have been identified.

Figure 10.9. LT   Dynamic Modulus Predicti

software, available from the LTPP program.

10: Turning LTPP Data INTOESU
Pavement Maintenance Manuals of Practice

As mentioned in the LTPP Data Analysis section, the 

SHRP-H-106 project (Innovative Materials Development and Testing) monitored 22 sites throughout the 

United States and Canada to evaluate the performance 

and cost-effectiveness of maintenance materials and 

procedures. The project resulted in the publication of a 

set of manuals on asphalt and concrete repair. In 1999,

the LTPP program revised and updated the original 

four SHRP manuals with the latest long-term performance and cost-effectiveness information generated 

by its continued monitoring of the SHRP-H-106 project sites. The manuals cover the performance of repair 

materials and methods, the availability and relative 

costs of repair materials, and the planning, designing, 

construction, and performance monitoring for the 

repair activities.

•	 Materials and Procedures for Rapid Repair of PartialDepth Spalls in Concrete Pavements—Manual of 

Practice.88

•	 Materials and Procedures for Repair of Potholes in 

Asphalt-Surfaced Pavements—Manual of Practice.89

•	 Materials and Procedures for Repair of Joint Seals in

Portland Cement Concrete Pavements—Manual of 

Practice.90

•	 Materials and Procedures for Sealing and Filling

Cracks in Asphalt-Surfaced Pavements—Manual of 

Practice.91

Nationl P

Pavement Management System Tools 

and Techniques

Goal: Identify improved measurement and predicti

tools.

• Objective 2: Materials characteri

• Objective 4: Evaluation and use of pa

condition data in pavement management.

• Objective 9: Comprehensive use of LTPP to i

the management of pavement assets.

The LTPP program is a project-level program, but the 

data collection guidelines and procedures and equipment protocols are also useful for network-level programs, such as pavement management systems. The 

following products have contributed to the quality of 

the pavement condition data collected by highway 

agencies to populate their pavement management 

systems and to help them determine which pavement 

sections should receive some type of treatment 

or rehabilitation.

Distress Identification Manual

The LTPP program developed the Distress Identification Manual for the Long-Term Pavement Performance 

Program (Standard Edition)92 to establish a consistent, 

uniform basis for collecting pavement distress data. 

The manual is divided into three sections, each focusing on one type of pavement: AC, PCC, and continuously reinforced concrete pavement (CRCP). It 

provides a common language for describing cracks, 

potholes, rutting, spalling, and other distresses being 

monitored by the program, and contains color 

photographs, drawings, and text that clearly label, 

describe, and illustrate each type of distress. Many 

highway agencies have adopted the manual’s procedures and definitions. 

The Local Technical Assistance Program, with 

assistance from the FHWA Resource Center, developed four pocket versions of the manual:

•	 AC Distress Identification Guide (Pocket Edition).

•	 PCC Distress Identification Guide (Pocket Edition).

•	 CRCP Distress Identification Guide (Pocket Edition).

•	 AC (for Local Agencies) Distress Identification

Guide (Pocket Edition).93

Created with the field technician in mind, the pocket 

editions are made of durable plasticized material 

(figure 10.10). They have not been updated, however,

and do not reflect the most recent definition for every 

distress type. 

The fifth and latest version of the standard edition 

was published inMay 2014.The manual and the pocket

210 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
guides are available by contacting the LTPP Customer 

Support Service Center (Email: ltppinfo@dot.gov).

FWD Calibration Procedures

Early in the LTPP program, the need for FWD calibration procedures and regional calibration centers was 

identified as a priority. The original calibration protocol was finalized in 1992, and calibration centers were

established in Pennsylvania, Texas, Minnesota, and 

Nevada (the latter eventually was moved to Colorado). 

These centers provided calibration services not only 

for LTPP FWDs, but also for FWDs operated by highway agencies and private consultants. In the first 3

years of center operation, many of the non-LTPP units 

were found to be significantly out of calibration. Hence, 

the LTPP calibration centers provided an essential 

public service that resulted in significant construction 

savings, especially in situations where design is driven 

by FWD measurements, such as flexible pavement 

overlay design and jointed rigid pavement load transfer 

rehabilitation design. Since 1997, more than 500 FWD

calibrations have taken place at these centers.

Considering that the LTPP FWD calibration centers 

had been operating with essentially the same equipment and procedures since 1992, the Falling Weight

Deflectometer Calibration Center and Operational

Improvements Pooled-Fund Study, TPF-5(039), was

initiated in 2004 to improve the calibration process 

and update the calibration center equipment and software.94 The study’s reports contain the new protocol, 

equipment specifications, and other updated specifications of interest to engineers and technicians who perform structural evaluation of pavements.95,96 The new 

calibration equipment is highly portable and allows 

calibrations to be performed at a location of the FWD 

owner’s choosing. The new protocol has been implemented at all of the FWD calibration centers operated 

by State highway agencies, for which technical support 

and QA audits have been assumed by the AASHTO 

Materials Reference Laboratory, as noted in chapter 6.

These centers continue to be used by highway agencies 

and private consultants to calibrate their FWDs. Accurate data that are a direct result of the calibration procedure yield large dividends to stakeholders in the 

form of improved decisions and increased efficiency. 

Perhaps the most significant outcome of the FWD 

pooled-fund study was AASHTO’s adoption of the 

new calibration system as Standard Practice R 32-09,

Calibrating the Load Cell and Deflection Sensors for 

a Falling Weight Deflectometer, in 2009 (updated

in 2011).97,98 The new procedure is demonstrated in a 

video.99 It has been adopted by Denmark and Australia, 

and other countries are considering using the procedure, as well.

Figure 10.10. Distress Identification Guid

Asphalt Concrete Pavements, one of the five pocket 

versions of the Distress Identification Manual that 

were created for use by field technicians.

The most significant outcome of the 

FWD pooled-fund study was AASHTO’s 

adoption of the new calibration system 

as Standard Practice R 32, Calibrating 

the Load Cell and Deflection Sensors 

for a Falling Weight Deflectometer. 

10: Turning LTPP Data INTOESU
Pavement Profiler Standards 

In 2002, FHWA initiated a pooled-fund study, Improving the Quality of Profiler Measurement, TPF-5 (063),

to assist in developing AASHTO standards for QA programs related to ride quality data collection, and to 

establish a level of integrity to pavement profiler measurements through calibration processes and verification procedures.100 The resulting standards included:

•	 AASHTO M 328-10, Standard Equipment Specification for Inertial Profiler.

101 

•	 AASHTO R 56-10, Certification of Inertial Profiling

Systems.

102 

•	 AASHTO R 57-10, Operating Inertial Profiling Systems.

103

•	 AASHTO R54-10,Accepting PavementRide Quality

When Measured Using Inertial Profiling Systems.104

One of the main objectives of this multiyear, multitasked, $2.4 million study was to deliver a profile 

analysis software program. The Profile Viewing and

Analysis (ProVAL) software was released in 2001, and

its native data format became an ASTM International 

standard in 2007, E 2560-07, Standard Specification

for Data Format for Pavement Profile. The free software enables users to view and analyze pavement 

profiles collected by profile measurement equipment.105 Different equipment manufacturers use different data formats and standards, making it difficult 

to compare profiles collected by diverse brands of 

equipment. ProVAL is the first and only software

application that can read data from numerous pavement profilers and unify them using a common data 

format.106 The software is continually upgraded, and 

new features are added.

Nationl 

Traffic Loading and Environmental Effects

Goal: Identify improved weigh-in-motion (WI

technology and data interpretation that will more 

accurately determine specific traffic volumes and 

determine the environmental effects on pavement 

performance.

• Objective 1: Traffic characterization and pred

• Objective 3: Determination of environ

effects in pavement design and performance 

prediction.

Understanding the performance of pavements requires 

knowing the traffic loading and environmental conditions imposed on them. Over the years, the LTPP 

program has contributed to improving traffic data 

monitoring by objectively examining the types of traffic data collection equipment, developing standard 

equipment calibration and validation protocols, and 

identifying quality checks to perform on the data. In 

addition, the program has improved its climatic database by using data from the National Aeronautics and 

Space Administration’s (NASA) Modern Era Retrospective Analysis for Research and Applications 

(MERRA) to establish weather data for the LTPP test 

sites. This section covers some of the LTPP products 

related to the impact of traffic and climate on pavement performance.

Traffic Data Collection Advancements

The LTPP program has been on the leading edge of traffic monitoring technology. The program has developed 

and continues to refine several procedures to address 

variability in traffic data that can be attributed to multiple factors: equipment type, calibration procedures (or 

lack thereof ), and duration of monitoring. These procedures include the WIM calibration protocol and smoothness specifications for pavement in the vicinity of the 

traffic monitoring equipment. Also, work in improving 

how vehicles are classified continues to be an important 

aspect of LTPP’s traffic data monitoring work.107 

ProVAL is the first and only software 

application that can read data from 

different pavement profilers and unify 

them using a common data format.

212 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
10: Turning LTPP Data INTOESU

Figure 10.11. Participating States in the LTPP SPS Traffic Data Collection Pooled-Fund Study. M

shows the donor States, States with assessments only, and weigh-in-motion equipment (WIM) equipment 

installed by the State or the LTPP contractor. (28 highway agencies, with 26 weigh-in-motion (WIM) 

installations in 22 States).

Contractor WIM Installations

State WIM Installations

One-Time Site Assessment

Donor States

Non-Participating States

CA

AZ NM

CO

KS

TX

FL

LA

AR

TN

MS AL

WA

ID

UT

GA

NY

VA

IN PA

MN

WI

MI

OH IL

NC

ME

CT

NJ

MD

MB

DE

Initiated in 2001 by FHWA, the LTPP SPS Traffic

Data Collection Pooled-Fund Study, TPF-5 (004), was 

established to install, calibrate, and validate continuous traffic data for as many as 84 SPS sites throughout

the United States and Canada.108 Ultimately, only 28

SPS sites were selected to collect the data because of

the high costs of equipment installation, calibration, 

and maintenance (figure 10.11). Although highway

agencies contributed millions of dollars to this study 

with the LTPP program also contributing millions, 

funding simply was not available to install and maintain adequate traffic monitoring equipment at each of 

the proposed SPS sites for a minimum of 5 years. The 

number of study sites was limited to assure that the 

work conducted at each site would be of high quality. 

This study has resulted in the development of equipment and WIM site selection specifications, pavement 

smoothness specifications, data collection and processing protocols, and a standard vehicle classification 

algorithm. More importantly, the availability and quality of monitored traffic data has improved significantly 

because of this data collection effort. 

Products related to the traffic data pooled-fund 

study include the LTPP Field Operations Guide for 

SPS WIM Sites, as discussed in chapter 7, as well as

several others: 

•	 The pavement smoothness specification was revised, tested in several States, and adopted provisionally by AASHTO in 2008 as MP 14-08, Standard

Specification for Smoothness of Pavement in Weighin-Motion (WIM) Systems. In 2013, AASHTO adopted M 331-13, Standard Specification for Smoothness of Pavement in Weigh-in-Motion (WIM) 

Systems.109

•	 The LTPP Optimal Weigh-in-Motion Site Locator

(OWL) software was originally developed as the 

LTPP WIM Index. OWL uses longitudinal profile 

data to determine if a particular pavement is suitable for a WIM installation, and identifies the opti-
214 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

mal location to install a WIM system to collect the 

best traffic data.110 OWL was developed as a new 

module of the ProVAL software to implement the

method adopted inAASHTO M 331-13. ProVAL is an

engineering software application used to view and

analyze pavement profiles.111

•	 The LTPP Classification Algorithm, the first national standard classification algorithm to classify vehicles in the FHWA scheme, was developed and verified by the LTPP program and adopted by the TRB 

Traffic ETG in January 2013.112 In addition, the algorithm is being used as an example by FHWA’s Office 

of Highway Policy Information for States to use in 

their own vehicle classification efforts. 

•	 The LTPP program developed the LTPP Pavement

Loading User Guide (LTPP-PLUG) software to assist highway agencies in selecting axle loading defaults to use with the MEPDG. These defaults can 

be used for pavement sites where site-specific traffic data collected by WIM equipment are limited or 

do not exist—helping transportation agencies to 

“plug” their traffic loading data gaps when designing pavements.113,114 LTPP-PLUG is available on the 

LTPP InfoPave Web site.

LTPP Seasonal Monitoring Program CD-ROM

The LTPP SMP was an intensive monitoring effort 

undertaken on a subset of the LTPP test sections to 

obtain data to improve understanding of seasonal 

variations in pavement structures and the factors 

that cause those variations. An SMP CD-ROM was 

created to provide a project summary and supporting 

documentation needed to facilitate future application of the LTPP data. The CD-ROM includes videos 

produced by the North Carolina and Colorado DOTs 

that show how the monitoring instrumentation was 

installed at the SMP test sections in both States. The 

CD-ROM can be obtained from the LTPP Customer 

Support Service Center (Email: ltppinfo@dot.gov).

Pavement Performance Forecast Online Tool 

Funded through the pooled-fund study, Effect of Multiple Freeze-Thaw Cycles versus Deep Frost Penetration on Pavement Performance, TPF-5(013), and

procured under the LTPP Data Analysis program, 

pavement performance comparisons were made for 

different frost climates using prediction models developed specifically for the study.115 In light of this analysis, a thorough review of agencies’ standard practices 

for mitigating frost-related damage was conducted. 

Consideration was given to the new MEPDG. Additional analysis was performed to quantify the cost 

implications of maintaining pavements in frost areas. 

The final report has been published,116 and an online 

tool providing pavement performance predictions (i.e., 

roughness and distress) for both flexible and rigid 

pavements using the models developed in this project 

is available on the LTPP InfoPave Web site or by contacting the LTPP Customer Support Service Center 

(Email: ltppinfo@dot.gov). The online program can be 

used by State, Provincial, county, and local highway 

agencies to estimate performance trends for pavement 

sections within their jurisdictions.

Arizona SPS-2 Curl and Warp Report

An analysis was conducted of the roughness and 

roughness progression of 21test sections on the SPS-2

(structural factors of rigid pavements) site in Arizona 

over the first 16 years of the experiment. Traditional

profile analyses revealed roughness was caused by 

transverse and longitudinal cracking on some test 

sections and some localized roughness was caused by 

built-in defects. However, the analyses showed that 

curl and warp contributed to, and in some cases dominated, the roughness on many of the test sections. 

The study applied objective profile analyses to quantify the level of curl and warp on each section, using 

automated algorithms to estimate the gross strain 

gradient needed to deform each slab into the shape 

present in the measured profile. This study demonstrated the potential value of applying the methods 

used to other jointed concrete pavements, including 

other SPS-2 sites.117
10: TURNING LTPP DATA INTO RESULTS 215

NATIONAL PAVEMENT NEED 5: 

National Pavement Performance Data Services

GOAL: Establish and maintain an accurate, accessible, 

and high-quality database.

As the LTPP program continues, the database is and 

will continue to be the primary and pivotal product 

of the program. An important role for the program is 

to support this national need by providing pavement 

performance data that are accessible and usable not 

only to the pavement community, but other possible 

users such as bridge engineers, air quality researchers, freight policy makers, and transportation statisticians. In conjunction with the data, the program 

has developed tools to disseminate the data and to 

support potential users in working with the data 

effectively. The LTPP database is unique not only in 

its size and quality, but also in that access to the data 

is freely provided.

Dissemination Tools

As the database has matured, the LTPP program has 

improved access to the data with each advancement in 

computer and communications technology. This section 

briefly describes some of these dissemination tools in 

chronological order, with details provided in chapter 8. 

• The LTPP Data Sampler and Data Request Program 

was used early in the program to distribute data to 

users. 

• DataPave was a user-friendly interface adopted in 

the mid-1990s, distributed on CD-ROM. The DataPave CDs were quite popular in that they assisted 

users unfamiliar with the LTPP database to access a 

limited amount of data.

• The Data Dictionary was a searchable list of LTPP 

tables and fields that allowed users to identify the 

location within the numerous tables where specific data are stored. By searching a pavement engineering term, the user was not required to know 

specific table and field nomenclature.

• As the Internet came into wide use, DataPave was 

converted to a Web-based format called “DataPave 

Online.” 

• The primary data delivery mechanism has been the 

Standard Data Release, typically timed for delivery 

at the TRB Annual Meeting. Distribution was first 

made by CD-ROM, then DVD, and later by thumb 

drive before being made available over the Internet. 

This annual release includes the database and new 

data collected over the course of the year, along with 

any new tables developed as part of data analysis 

projects or to assist end users.

• Products Online was established as a “one-stop 

shopping” Web site for multiple LTPP Products including DataPave Online, as well as other valuable 

program information. More than 40,000 downloads 

have been completed by upwards of 3,000 unique 

users worldwide. 

• Moving beyond DataPave Online and Products 

Online, the LTPP program developed an integrated, 

comprehensive Web site—LTPP InfoPave—to make 

the LTPP data more accessible and functional for users. The Web site offers new and expanded features, 

not only to the pavement performance data (encompassing the Standard Data Release), but also to information that supports and extends the stored data—raw 

data, images, reference materials, guidelines, resource 

documents, and studies and analyses published by 

FHWA. LTPP InfoPave allows users to streamline 

their access by creating a “My LTPP” menu customized to their needs, and offers the added benefit of professional networking within a growing LTPP user 

community through linked social media. A smartphone application, LTPP InfoPave Mobile, developed 

in tandem with the Web site, allows users to map and 

select LTPP test sections using visual navigation, retrieve section detailed information, and access LTPP 

data collection guidelines such as the LTPP Distress 

Identification Manual.

LTPP Customer Support and Feedback Mechanisms

The LTPP program has always made it possible for users 

to obtain data—from the early days, sending out data on 
216 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

floppy disks, to today, assisting customers with identifying and downloading data that meet their analysis needs. 

In 1997,theLTPPCustomer Support ServiceCenterwas

formally established to handle data requests and to also 

provide a feedback mechanism for data users. Since the 

center was established, more than 8,000 requests for

data, research reports, products, software, and other 

LTPP program information have been received.

The program also plays a role in educating data 

users. With the development of DataPave, the program staff created a demonstration workshop to help 

data users transition to the new way of accessing 

LTPP data. In 1998, in partnership with ASCE, the

LTPP program presented the workshop in 16 locations to an audience of highway agency personnel, 

practitioners, and university professors.118

In 2011, the program began hosting Webinars to

provide updates and important information to users. 

Examples of Webinar topics include the history and 

future plans for the program, the program’s impact on 

industry, roles and responsibilities of the LTPP State 

Coordinators, and LTPP’s new initiative to construct 

and monitor warm-mix asphalt pavements. Most of the 

Webinar sessions are recorded and are available on the 

LTPP Web site.

LTPP BENEFITS AND BROADER I

The emergence of new technologies over time and 

the LTPP program’s emphasis on continuously 

improving operations led to improvements in the 

program’s practices that have benefited the entire 

pavement community. For instance, LTPP QC/QA 

processes were developed to fill a void in pavement 

engineering practice, as no formal procedures existed for many of the activities conducted by the program. These procedures were necessary because the 

size and scope of the program required the use of 

different pieces of equipment (although of the same 

make and model) and the involvement of multiple 

individuals in different locations. Standard equipment protocols, training, and data collection procedures were needed to assure reliability of the data. 

As the program addressed these needs, highway 

agencies and the pavement industry benefited from 

the knowledge, improved standards, and QC procedures that resulted.

Key Findings From the LTPP Program

The LTPP data analyses have addressed a broad array 

of topics, from field validation of pavement design 

procedures, to the study of variability in traffic and 

materials data, to investigating pothole repair techniques. Many findings from these studies provide 

information that is critical for the improvement of 

pavement technology. 

To identify some of the key findings, the LTPP program reviewed studies reported between 1990 and

1999 and published a roster of more than 60 key findings for that decade.119 The summarized results were 

organized by topic: site conditions, structural features, 

materials, initial roughness, pavement maintenance, 

pavement rehabilitation, AASHTO design validation, 

and performance modeling. In 2004, a second review 

and report drew on results published from 2000 to 

2003. Again, more than 60 significant findings were

identified and summarized, and scores of related publications were listed.120 In the 2000–2003 report, local

calibration of the 2002 Pavement Design Guide was 

added as a new topic area, but the AASHTO validation 

and performance modeling were not included.

The goal of these data analysis reviews was to provide LTPP partners with information that would help 

them in their efforts to design, build, and maintain 

cost-effective and long-lasting pavements, and to make 

the partners aware of the vast amount of information 

available to them. Most of the documents identified in 

the reports are available at the LTPP, NCHRP, and TRB 

Web sites. 

The Benefits Stud

To capture the wide array of benefits resulting from the 

LTPP program, a formal data analysis project was 

awarded in 2006. Multiple objectives were part of the

project scope, including:

•	 Investigating the benefits derived from the LTPP

program to traffic characterization and prediction.

•	 Studying the improvement in materials characterization originated from the LTPP program.
10: Turning LTPP Data INTOESU

•	 Determining the environmental effects on pavement design and performance prediction contributed by the LTPP data.

•	 Evaluating the benefits of LTPP data in pavement

management.

•	 Investigating the benefits of using the LTPP data in

the evaluation of existing design methods and in the 

development of new pavement response and performance models applicable to pavement design 

and performance prediction.

•	 Studying the effects of LTPP data on the development of maintenance and rehabilitation strategies.

•	 Determining the influences of the LTPP data on the

evaluation of specific design features on pavement 

performance.

•	 Investigating future benefits that can be cultivated

from the LTPP program.

Hundreds of reports, products, and other information 

were collected and summarized, and in examining all 

this, three primary areas were identified within which 

benefits resulting from LTPP activities to date could be 

categorized:121

•	 The LTPP database.

•	 Improved measurement processes.

•	 Pavement design and management.

LTPP Database

As discussed in the previous section, the single most 

significant product of the LTPP program is the pavement performance database. The database supports 

national, State/Provincial, and local research projects, 

as well as a variety of international analysis efforts. 

With appropriate maintenance and update activities in 

place, the database will continue to be the primary 

source of information for future generations of pavement and other researchers.

An outcome that has benefitted the education community is the introduction and use of LTPP data in 

university engineering curricula. A number of engineering schools with pavement engineering classes 

have developed course curricula around the database. 

This application has dual benefits: students are challenged with computational problems based on actual 

field data, and they learn to use database manipulation 

tools. Students emerge with conceptual and practical 

knowledge that will benefit the pavement engineering 

community into the future.

Improved Measurement Processes

The LTPP program has advanced data quality procedures in both the field and the office, as discussed in 

chapter 8 and chapter 9. This section highlights

advances in equipment specifications and maintenance procedures, software, and laboratory and data 

collection protocols that have led to a higher quality 

standard for pavement performance measurement for 

the pavement community (see sidebar). 

LTPP protocols have formed the basis for improved 

measurement standards, and the pavement industry has 

been proactive in using these standards to support their 

chartered objectives. For example, efforts within the 

LTPP program to achieve greater reliability and precision 

in FWD data resulted in the establishment of calibration 

centers and the adoption of much-improved nationwide 

calibration standards (chapter 6). In addition, traffic data

collection equipment suppliers have improved their 

hardware and software, and some have incorporated 

more stringent data checks as a result of the program’s 

requirements (chapter 7). Equipment manufacturers

have also adopted the program’s resilient modulus protocols as a QC check during equipment production.

The program has significantly improved other data 

collection practices for a wide range of operations including manual and automated distress surveys and longitudinal and transverse profiles. Numerous LTPP data 

collection procedures have been adopted by industry. The 

most widely implemented of these procedures is the 

LTPP Distress Identification Manual. The manual is used 

by more than 20 State highway agencies and numerous 

local entities. In 1997, the National Highway Institute

(NHI) developed a distress training course using the 

LTPP Distress Identification Manual and LTPP distress 

accreditation procedures. The LTPP program funded the 

course, offering it to the States free of charge. Although 

the course is no longer offered by NHI, it was delivered to 

many domestic and international participants.

The program has purchased a variety of sophisticated data collection equipment and systems. The 

process by which the equipment specifications were 
218 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Software Programs

LTPP software QC/QA programs such as FWDCAL, 

ProQual, SMPCHECK, DiVA, and LTAS are discussed 

in earlier chapters. While much of this software was 

tailored specifically for LTPP operations, some of 

these programs have been used throughout the 

pavement community in processing and checking 

data for highway agency needs and research 

analysis projects.

Documentation

In the service of QC/QA, the LTPP program has 

developed a wide variety of reports, protocols, 

and other documents that are assisting highway 

agencies and researchers alike. Several of these 

have been addressed previously, including the 

Distress Identification Manual for the Long-Term 

Pavement Performance Program and the LTPP 

Manual for Falling Weight Deflectometer Measurements. The FWD calibration centers established 

under the program are a major benefit to the 

highway agencies and industry. 

To capture the entire laboratory testing inputs 

and results as recommended during the peer review 

process, the LTPP program developed its own LTPP 

Laboratory Materials Testing and Handling Guide.122

For most elements, the laboratory protocols were 

modeled on ASTM and AASHTO standards. However, in the conduct of resilient modulus testing for 

both bound and unbound layers, existing protocols 

did not meet LTPP’s data quality standards and 

therefore new protocols (LTPP Protocols P07 and 

P46, respectively) were developed. To supplement 

this development, the LTPP program prepared a 

series of videos to instruct testing laboratory 

personnel not only on how to conduct the test 

procedures, but also on how to ensure that the 

equipment is functioning properly. Initially, an LTPP 

review found a large variability in test results from 

different laboratories, which was partially attributed to problems with laboratory equipment 

electronics. After implementing the startup 

procedures, the variability was greatly reduced.

Seeking to reduce variability is a constant part 

of the LTPP QC/QA process; eliminating variability 

entirely is rarely practical. Therefore, quantifying 

data variability is the subject of many analysis 

activities. A few of these analyses were discussed 

earlier in this chapter, and following is a partial list 

of additional studies:

• Accuracy of Weather Data in the LTPP Database.123

• Use of LTPP Data to Verify the Acceptance 

Limits Developed for Penndot Pavement 

Distress Data.124

• Quantification of Smoothness Index Differences 

Related to LTPP Equipment Type.125

• Profile Data Variability in Pavement Management: Findings and Tools From LTPP.126

• LTPP Data Analysis: Variations in Pavement 

Design Inputs.127

• Preliminary Evaluation and Analysis of LTPP 

Faulting Data.128

Understanding variability, bias, and precision allows 

practitioners to properly incorporate data points 

into their decision processes.

LTPP QC/QA Res

prepared, achievement of the specifications was confirmed, and the final selection of equipment was made 

have become a model for many highway agencies 

planning to acquire similar equipment for their own 

use. As a recent example, procurement for the current 

LTPP profilers involved developing a set of specifications for the vendors and then performing a field 

verification to prove the specifications could be 

met before moving forward with the selection process. Some highway agencies have expressed interest 

in using this model for future major equipment 

purchases.
10: Turning LTPP Data INTOESU

Pavement Design and Management

An original LTPP objective was to acquire data for use 

in evaluating existing design methods and in developing new ones. The LTPP program is the only national 

research program that has collected pavement performance data reflecting different climates and different 

materials, using standard data collection protocols and 

equipment. This consistent manner of collecting longterm pavement performance data and ensuring its 

quality using verified QC/QA practices has had a tremendous impact in advancing new pavement design 

procedures, particularly the development and implementation of the MEPDG. In addition, LTPP data has 

been implemented by State/Province and local agencies in network-level and project-level pavement management systems to predict future performance and 

determine maintenance and rehabilitation needs. 

LTPP CONTRIBUTIONS T

FEDERAL EFFORTS

The LTPP program lends support to various U.S. DOT 

and FHWA programs and initiatives. Data and processes 

developed during the program have been used and 

continue to be used in research efforts of national 

significance. Some examples include:

•	 U.S. DOT Research, Development, and Technology

Strategic Plan, FY 2013–2018.

–	 The LTPP program is named a key priority area

for preserving existing highways and extending 

the life of future highways.129

•	 Highway Performance Monitoring System (HPMS).

–	 LTPP distress definitions provide the basis for

ride, cracking, faulting, and rutting data for the 

HPMS database, which is maintained by FHWA’s 

Office of Highway Policy Information.130

–	 LTPP data enable mapping of HPMS with LTPP

for modeling and performance measures.131

•	 Pavement Health Track (PHT) Analysis Tool—developed by FHWA’s Office of Asset Management to 

calculate remaining service life for highway networks using data from HPMS and State pavement 

management systems.

–	 The LTPP database supplies data that are missing in HPMS and State databases.

–	 LTPP data from 40 sites in 20 States were used in

an experiment to identify any significant differences between MEPDG version 0.8 (PHT Tool)

and DARWin-ME 1.0 pavement performance

predictions and how possible differences may 

impact PHT results.132 

•	 HighwayEconomicsRequirement System (HERS)—

used by FHWA’s Office of Highway Policy Information to develop the highly influential bi-annual report to Congress, “Status of the Nation’s Highways, 

Bridges, and Transit: Conditions & Performance.”

–	 LTPP datawere used to calibrate the HERS pavement deterioration models.

–	 LTPPdataareusedtofillgaps intheHPMSdataset,

which is used in HERS. Regionalized data provide 

specific inputs for different areas of the country.

•	 Long-Term Bridge Performance (LTBP) program—

sponsored by FHWA’s Office of Infrastructure 

Research and Development.

–	 The LTPP program laid the groundwork for

national-scale research programs such as the 

LTBP program.

–	 The LTPP program shares its expertise and

experience in this endeavor.

•	 Climate-related infrastructure research—conducted

in various Federal agencies.

Beyond the benefits themselves, what is remarkable is how widespread—both 

geographically and throughout the public and private sectors—the use of LTPP 

products and data has become. 
220 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

–	 The LTPP program developed procedures for the

use of NASA’s MERRA data to establish virtual 

weather stations at any location in the country, as 

noted above. This capability can yield high-quality 

climate data anywhere in the world in a consistent 

and high-quality format.

SUMMAR

Turning data into results that are of value and use to the 

highway community is an important function in understanding pavement performance. The LTPP program’s 

return on investment, while challenging to fully quantify, 

is already estimated at over $2 billion in savings and will 

continue to grow.133 The many research studies and their 

products conducted under the program are too numerous to mention in this chapter, and their numbers continue to grow as the LTPP program continues to improve 

the functionality of the database and revisit the data with 

advancing knowledge. The program has had a significant 

positive impact on the quality of pavement construction 

and rehabilitation by influencing the AASHTO and 

ASTM standards. It has advanced the capabilities of 

modern pavement monitoring equipment through its 

equipment requirements and new software tools. The 

program continues to develop products needed by highway agencies and distribute the tools and knowledge 

gained through the program. Through these program 

activities, LTPP data can fulfill its potential to improve 

industry practices, pavement engineering studies, the 

quality of pavement research, and, ultimately, the performance and cost-effectiveness of the Nation’s highways.

On the road to achieving the results reported in this 

chapter, the LTPP program encountered many obstacles and problems. As the first pavement performance 

data collection effort of its breadth and depth, the program often faced a steep learning curve, and lessons 

were dearly earned. The next chapter reviews some of 

the lessons learned in the program.

REFERENCE

1.	Guide for Design of Pavement Structures. American 

Association of State Highway and Transportation 

Officials (AASHTO). Washington, DC, 1986.

 2. Each volume of Early Analyses of LTPP General 

Pavement Studies Data carries a second title: Executive 

Summary (SHRP-P-392) by J. B. Rauhut and M. I.

Darter (http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-P-392.pdf ); Data Processing and Evaluation

(SHRP-P-684) by B. M. Killingsworth, A. L. Simpson,

J. B. Rauhut, E. Owusu-Antwi, R. Ahmad, M. I. Darter, 

and O. J. Pendleton (http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-684.pdf ); Sensitivity 

Analyses for Selected Pavement Distresses(SHRP-P-393)

by A. L. Simpson, J. B. Rauhut, P. R. Jordahl, E. 

Owusu-Antwi, M. I. Darter, R. Ahmad, O. J. Pendleton, 

and Y-H Lee (http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-393.pdf ); Evaluation of the AASHTO 

Design Equations and Recommended Improvements

(SHRP-P-394) by J. F. Daleiden, J. B. Rauhut, B.

Killingsworth, E. Owusu-Antwi, M. I. Darter, and R. 

Ahmad (http://onlinepubs.trb.org/onlinepubs/shrp/

SHRP-P-394.pdf ); Lessons Learned and Recommendations for Future Analyses (SHRP-P-680) by J. B. Rauhut,

A. L. Simpson, J. F. Daleiden, M. I. Darter, E. OwusuAntwi, and O. J. Pendleton) (http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-680.pdf ). Published by

Strategic Highway Research Program, National 

Research Council, Washington, DC, 1994.

3.	J. B. Rauhut, A. L. Simpson, J. F. Daleiden, M. I. Darter,

E. Owusu-Antwi, and O. J. Pendleton. Early Analyses of 

LTPP General Pavement Studies Data: Lessons Learned 

and Recommendations for Future Analyses (SHRP-P680). Strategic Highway Research Program, National

Research Council, Washington, DC, 1994. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-680.pdf.

 4. L. D. Evans and A. R. Romine. “Materials and Procedures for the Repair of Joint Seals in Concrete Pavements: Manual of Practice.” Concrete Pavement Repair 

Manuals of Practice (SHRP-H-349). Strategic Highway

Research Program, National Research Council, 

Washington, DC, August 1993. http://onlinepubs.trb.

org/onlinepubs/shrp/SHRP-H-349.pdf.

 5. A. J. Patel, C. A. Good Mojab, and A. R. Romine. 

“Materials and Procedures for Rapid Repair of 

Partial-Depth Spalls in Concrete Pavements: Manual of 

Practice.” Concrete Pavement Repair Manuals of 

Practice (SHRP-H-349). Strategic Highway Research

Program, National Research Council, Washington, DC, 

August 1993. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-H-349.pdf.

6.	K. L. Smith and A. R. Romine. “Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements.” Manuals of Practice (SHRP-H-348).

Strategic Highway Research Program, National 

Research Council, Washington, DC, August 1993.

http://onlinepubs.trb.org/onlinepubs/shrp/SHRPH-348.pdf.
10: Turning LTPP Data INTOESU

	 7.	T. P. Wilson and A. R. Romine. “Materials and Procedures for the Repair of Potholes in Asphalt-Surfaced 

Pavements.” Manuals of Practice (SHRP-H-348).

Strategic Highway Research Program, National 

Research Council, Washington, DC, August 1993.

http://onlinepubs.trb.org/onlinepubs/shrp/SHRPH-348.pdf.

8.	T. P. Wilson, K. L. Smith, and A. R. Romine. LTPP

Pavement Maintenance Materials: PCC Partial-Depth 

Spall Repair Experiment, Final Report (FHWA-RD99-153). Federal Highway Administration, McLean, VA,

October 1999. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/99153/

99153.pdf.

9.	L. D. Evans, M. A. Pozsgay, K. L. Smith, and A. R.

Romine. LTPP Pavement Maintenance Materials: 

SHRP Joint Reseal Experiment, Final Report (FHWARD-99-142). Federal Highway Administration, McLean,

VA, September 1999. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/99142/99142.pdf.

10.	K. L. Smith, M. A. Pozsgay, L. D. Evans, and A. R.

Romine. LTPP Pavement Maintenance Materials: 

SPS-4 Supplemental Joint Seal Experiment, Final Report

(FHWA-RD-99-151). Federal Highway Administration,

McLean, VA, October 1999. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/99151/99151.pdf.

11.	K. L. Smith and A. R. Romine. LTPP Pavement Maintenance Materials: SHRP Crack Treatment Experiment, 

Final Report (FHWA-RD-99-143). Federal Highway

Administration, McLean, VA. September 1999.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/99143/99143.pdf.

12.	T. P. Wilson. Long-Term Monitoring of Pavement 

Maintenance Materials Test Sites (FHWA-RD-98-073).

Federal Highway Administration, McLean, VA, June

1998. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/98073/98073.pdf.

13.	D. A. Morian, S. D. Gibson, and J. A. Epps.

Maintaining Flexible Pavements—The Long-Term 

Pavement Performance Experiment: SPS-3 5-Year Data 

Analysis (FHWA-RD-97-102). Federal Highway

Administration, McLean, VA, March 1998. http://www.

fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/97102/97102.pdf.

14.	D. A. Morian, S. D. Gibson, and J. A. Epps. Concrete 

Pavement Maintenance Performance Review: SPS-4 

5-Year Data Analysis (FHWA-RD-97-155). Federal

Highway Administration, McLean, VA, July 1998.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/97155/97155.pdf.

15.	 “Manuals Provide Information for Pavement

Maintenance and Repair” (Product Brief ) (FHWARD-00-084). Federal Highway Administration,

McLean, VA, April 2000. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/00084/00084.pdf.

16.	E. B. Owusu-Antwi, L. Titus-Glover, and, M. I. Darter.

Design and Construction of PCC Pavements, Volume I: 

Summary of Design Features and Construction Practices 

That Influence Performance of Pavements (FHWARD-98-052). Federal Highway Administration,

McLean, VA, April 1998. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

pccp/98052/98052.pdf.

17.	L. Titus-Glover, E. B. Owusu-Antwi, T. Hoener, and M.

I. Darter. Design and Construction of PCC Pavements, 

Volume II: Design Features and Practices that Influence 

Performance of Pavements (FHWA-RD-98-127). Federal

Highway Administration, McLean, VA, October 1998.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/pccp/98127/98127.pdf.

18.	L. Titus-Glover, E. B. Owusu-Antwi, and M. I. Darter.

Design and Construction of PCC Pavements, Volume III: 

Improved PCC Performance Models (FHWA-RD-98-113).

Federal Highway Administration, McLean, VA, January

1999. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/98113/98113.pdf.

19.	E. O. Lukanen, R. Stubstad, and R. Briggs. Temperature 

Predictions and Adjustment Factors for Asphalt 

Pavement (FHWA-RD-98-085). Federal Highway

Administration, McLean, VA, June 2000. http://www.

fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/98085a/98085a.pdf.

 20. LTPP Guide to Asphalt Temperature Prediction and 

Correction (FHWA-RD-98-085). http://www.fhwa.dot.

gov/publications/research/infrastructure/pavements/

ltpp/fwdcd/.

21.	 J. F. Daleiden, A. Simpson, and J. B. Rauhut. Rehabilitation Performance Trends: Early Observations From 

Long-Term Pavement Performance (LTPP) Specific 

Pavement Studies (SPS) (FHWA-RD-97-099). Federal

Highway Administration, McLean, VA, January 1998.

http://isddc.dot.gov/OLPFiles/FHWA/009678.pdf.

 22. “Study Confirms Relationship Between Fine Aggregates and Rutting,” Focus (FHWA-SA-97-024), June

1997. http://www.fhwa.dot.gov/publications/

focus/97jun/67ruts.cfm.

23.	 “Expert Task Group Defines LTPP Data Analysis

Program,” Focus (FHWA-RD-00-065) December 2000.

http://www.fhwa.dot.gov/publications/focus/00dec/

ltpp.cfm. 
222 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

 24. “Strategic Plan for Long-Term Pavement Performance 

Data Analysis.” Nov. 9, 1999. Web page. http://www.

fhwa.dot.gov/research/tfhrc/programs/infrastructure/

pavements/ltpp/pdf/tablecloth.pdf.

 25. “Thank You for Saying ‘Yes’ When We Called,” LTPP 

Newsletter, vol. 7, no. 1, Winter 2011, p. 2. http://www.

fhwa.dot.gov/publications/ltppnews/11028.pdf.

26.	W. H. Temple. Long-Term Pavement Performance

Committee Letter Report (Letter No. 27), Jan. 20, 2011,

p. 3. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_27.pdf.

27.	W. H. Temple. Long-Term Pavement Performance

Committee Letter Report (Letter No. 29), Mar. 5, 2012,

p. 3. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_29.pdf.

28.	Long-Term Pavement Performance Data Analysis

Program: Strategic Plan Objectives, Analysis Outcomes, 

and Supporting Projects. Web document. Dec. 11, 2013.

http://www.fhwa.dot.gov/research/tfhrc/programs/

infrastructure/pavements/ltpp/pdf/tablecloth_

complete.pdf.

29.	K. Chatti, N. Buch, S. W. Haider, A. S. Pulipaka, R. W.

Lyles, D. Gilliland, and P. Desaraju. LTPP Data Analysis: 

Influence of Design and Construction Features on the 

Response and Performance of New Flexible and Rigid 

Pavements. NCHRP Web-Only Document 74 (Project

20-50 [10/16]). National Cooperative Highway

Research Program, Transportation Research Board of 

the National Academies, Washington, DC, June 2005. 

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_

w74.pdf.

30.	E. T. Harrigan. “Signficance of ‘As-Constructed’ HMA

Air Voids to Pavement Performance from an Analysis of

LTPP Data,” National Cooperative Highway Research 

Program Research Results Digest, No. 269, September

2002. http://onlinepubs.trb.org/onlinepubs/nchrp/

nchrp_rrd_269.pdf.

31.	K. T. Hall and J. A. Crovetti. LTPP Data Analysis: 

Relative Performance of Jointed Plain Concrete 

Pavement with Sealed and Unsealed Joints NCHRP 

Web Document 32 (Project SP20-50[2]). National

Cooperative Highway Research Program, Transportation Research Board of the National Academies, 

Washington, DC, December 2000. http://onlinepubs.

trb.org/onlinepubs/nchrp/nchrp_w32.pdf.

32.	K. T. Hall, C. E. Correa, and A. L. Simpson. LTPP

Data Analysis: Effectiveness of Maintenance and 

Rehabilitation Options (NCHRP Web Document 47

(Project 20-50[3/4])). National Cooperative Highway

Research Program, Transportation Research Board of 

the National Academies, Washington, DC, June 2002. 

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_

w47.pdf.

33.	R. N. Stubstad, S. D. Tayabji, and E. O. Lukanen. LTPP

Data Analysis: Variations in Pavement Design Inputs 

(NCHRP Web Document 48 (Project 20-50[5])).

National Cooperative Highway Research Program, 

Transportation Research Board of the National 

Academies, Washington, DC, June 2002. http://

onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w48.pdf.

34.	E. C. Drumm and R. Meier. LTPP Data Analysis: Daily 

and Seasonal Variations in Insitu Material Properties 

(NCHRP Web Document 60 (Project 20-50[7/12])).

National Cooperative Highway Research Program, 

Transportation Research Board of the National 

Academies, Washington, DC, November 2003. http://

onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w60.pdf.

35.	R. W. Perera and S. D. Kohn. LTPP Data Analysis:

Factors Affecting Pavement Smoothness (NCHRP Web 

Document 40(Project 20-50[8/13])). NationalCooperative

Highway Research Program, Transportation Research 

Board of the National Academies, Washington, DC, 

August 2001. http://onlinepubs.trb.org/onlinepubs/

nchrp/nchrp_w40-a.pdf.

36.	R. N. Stubstad. LTPP Data Analysis: Feasibility of 

Using FWD Deflection Data to Characterize Pavement 

Construction Quality (NCHRP Web Document 52 

(Project 20-50[9])). National Cooperative Highway

Research Program, Transportation Research Board 

of the National Academies, Washington, DC, October 

2002. http://onlinepubs.trb.org/onlinepubs/nchrp/

nchrp_w52.pdf.

37.	D. Zollinger, S. Lee, J. Puccinelli, and N. Jackson.

Long Term Pavement Performance Program Computed 

Parameter: Moisture Content (FHWA-HRT-08-035),

Federal Highway Administration, McLean, VA, 2008.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/08035/08035.pdf.

38.	O. I. Selezneva, Y. J. Jiang, G. Larson, and T. Puzin.

Long Term Pavement Performance Computed Parameter: 

Frost Penetration (FHWA-HRT-08-057). Federal

Highway Administration, McLean, VA, November

2008. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/08057/08057.pdf.

39.	R. Kim, B. Underwood, M. S. Far, N. Jackson, and

J. Puccinelli. LTPP Computed Parameter: Dynamic 

Modulus (FHWA-HRT-10-035). Federal Highway

Administration, McLean, VA, September 2011.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/10035/10035.pdf.

 40. C. Rao, L. Titus-Glover, B. Bhattacharya, M. I. Darter, 

M. Stanley, and H. L. Von Quintus. Estimation of Key 

PCC, Base, Subbase, and Pavement Engineering Properties 

from Routine Tests and Physical Characteristics (FHWAHRT-12-030). Federal Highway Administration,

McLean, VA, August 2012. http://www.fhwa.dot.gov/
10: TURNING LTPP DATA INTO RESULTS 223

publications/research/infrastructure/pavements/

ltpp/12030/12030.pdf.

 41. C. Rao, L. Titus-Glover, B. Bhattacharya, and M. I. 

Darter. User’s Guide: Estimation of Key PCC, Base, 

Subbase, and Pavement Engineering Properties From 

Routine Tests and Physical Characteristics (FHWAHRT-12-031). Federal Highway Administration, 

McLean, VA, August 2012. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/12031/12031.pdf.

 42. R. Carvalho, M. Ayres, H. Shirazi, O. Selezneva, and 

M. Darter. Impact of Design Features on Pavement 

Response and Performance in Rehabilitated Flexible 

and Rigid Pavements (FHWA-HRT-10-066). Federal 

Highway Administration, McLean, VA, October 2011. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/10066/10066.pdf.

43. K. T. Hall, C. E. Correa, A. L. Simpson. LTPP Data 

Analysis: Effectiveness of Maintenance and Rehabilitation Options. NCHRP Web Document 47 (Project 

20-50[3/4]. National Cooperative Highway Research 

Program, Transportation Research Board, National 

Research Council, June 2002. https://www.csuchico.

edu/cp2c/documents/Library/life_extension-nchrp_

sps_sections.pdf.

 44. T. E. Baker. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 28), Aug. 5, 2011, 

pp. 7–9. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_28.pdf.

 45. Variability of Pavement Distress Data From Manual 

Surveys (TechBrief ) (FHWA-RD-00-160), Federal 

Highway Administration, McLean, VA, September 

2000. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/00160/00160.pdf.

 46. G. R. Rada, C. L. Wu, R. K. Bhandari, A. R. Shekharan, 

G. E. Elkins, and J. S. Miller. Study of LTPP Distress 

Data Variability, Volume 1 (FHWA-RD-99-074). 

Federal Highway Administration, McLean, VA, 

September 1999. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/99074/99074.pdf.

 47. J. Puccinelli, S. Karamihas, K. Hall, and K. Senn. 

Performance Evaluation of Arizona’s LTPP SPS-1 

Project:Strategic Study of Flexible Pavement Structural 

Factors (Final Report 396-1). Arizona Department of 

Transportation Research Center, February 2012. http://

ntl.bts.gov/lib/44000/44300/44357/AZ396-1.pdf.

 48. A. Ardani, S. Hussain, and R. LaForce. Evaluation of 

Premature PCC Pavement Longitudinal Cracking in 

Colorado, in Proceedings of the 2003 Mid-Continent 

Transportation Research Symposium, Ames, Iowa, 

August 2003, p. 9. http://www.ctre.iastate.edu/pubs/

midcon2003/ardanicracking.pdf.

 49. H. Yu, K. Smith, M. Darter. Field and Analytical Evaluation of the Effects of Tied PCC Shoulders and Widened 

Slabs on Performance of JPCP (CDOT-DTD-R-95-18). 

Colorado Department of Transportation, Denver, CO, 

October 1995. http://www.codot.gov/programs/

research/pdfs/1995-research-reports/jpcp.pdf.

 50. A. Ardani. Implementation of Proven PCCP Practices in 

Colorado (CDOT-DTD-R-2006-9). Colorado Department 

of Transportation, Denver, CO, April 2006, pp. 10–19, 

19–22. http://www.coloradodot.info/programs/

research/pdfs/2006/pccpimplementation.pdf. 

 51. “New Software Tool Paves the Way for More CostEffective, Durable Roads in Kansas: Kansas Relies on 

LTPPBind Software to Select Superpave Binder PGs” 

(Application Notes) (FHWA-RD-00-019). Federal 

Highway Administration, McLean, VA, November 1999. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/00019/00019.pdf.

 52. “Material Characterization and Seasonal Variation in 

Material Properties” (Jersey DOT’s Tech Brief ) 

(FHWA-NJ-2005-024) New Jersey Department of 

Transportation, February 2006. http://cait.rutgers.edu/

files/FHWA-NJ-2005-024.pdf.

 53. “Use of DataPave Online to Develop IRI Models for 

New Jersey’s Pavement Management System,” LTPP 

Newsletter, vol. 7, no. 2 (Summer 2011), p. 2. http://

www.fhwa.dot.gov/publications/ltppnews/11066.pdf.

 54. “LTPP Findings Pay Off for Pennsylvania: Change in 

Pavement Joint Design Standard Saves Pennsylvania 

Money and Reduces Construction Problems” 

(Application Notes) (FHWA-RD-00-064). Federal 

Highway Administration, McLean, VA, February 2000. 

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/00064/00064.pdf.

 55. T. J. Freeman, D. A. Pinchott, H. Ren, and C. H. 

Spiegelman. Analysis and Treatment Recommendations 

from the Supplemental Maintenance Effectiveness 

Research Program (SMERP) (FHWA/TX-03/4040-3), 

Federal Highway Administration, Washington, DC, 

2003, p. 2. http://tti.tamu.edu/documents/4040-3.pdf.

 56. T. J. Freeman and E. H. Rmeili. Development and 

Construction of the Texas Supplemental Maintenance 

Effectiveness Research Program (SMERP) Experiment 

(TX-93-1981-1F). Texas Transportation Institute/Texas 

Department of Transportation, Austin, TX, October 

1994. http://d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.

edu/documents/1981-1F.pdf. 

 57. T. J. Freeman, D. A. Pinchott, H. Ren, and C. H. 

Spiegelman. Analysis and Treatment Recommendations 

from the Supplemental Maintenance Effectiveness 

Research Program (SMERP) (FHWA/TX-03/4040-3). 

Federal Highway Administration, Washington, DC/
224 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Texas Department of Transportation, Austin, TX, 2003,

p. 67. http://d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.

edu/documents/4040-3.pdf.

58.	 “Analysis of Maintenance Treatments Produces Usage

Guidelines” (Project Summary Report 0-4040-S), 

Texas Transportation Institute, Austin, TX. http://tti.

tamu.edu/documents/0-4040-S.pdf.

59.	 I. M. Syed, T. J. Freeman, and R. E. Smith. “Effectiveness of Highway Maintenance Treatments Used in 

Texas,” in Flexible Pavement Rehabilitation and 

Maintenance (P. S. Kartdhal and M. Stroup-Gardiner, 

eds.). ASTM STP 1348 (SEDL/STP/STP1348-EB/

STP12857S), Philadelphia, PA, 1998, pp. 136–50.

60.	F. Zhou, E. Fernando, and T. Scullion. Development, 

Calibration, and Validation of Performance Prediction 

Models for the Texas M-E Flexible Pavement Design 

System. Federal Highway Administration, Washington, 

DC/Texas Department of Transportation, Austin, TX, 

2010. http://tti.tamu.edu/documents/0-5798-2.pdf.

61.	F. Zhou, S. Hu, and T. Scullion. Development and 

Verification of the Overlay Tester Based Fatigue Cracking 

Prediction Approach (FHWA/TX-07/9-1502-01-8).

Federal Highway Administration, Washington, DC/

Texas Department of Transportation, Austin, TX, 2007.

http://tti.tamu.edu/documents/9-1502-01-8.pdf.

	 62.	A. Banerjee, J. P. Aguiar-Moya, A. de F. Smit, and

J. A. Prozzi. Development of the Texas Flexible Pavements 

Database (FHWA/TX-10/0-5513-2). Texas Department

of Transportation, Austin, TX, 2008, 2010. http://www.

utexas.edu/research/ctr/pdf_reports/0_5513_2.pdf.

63.	NCHRP 01-37A [Completed], Development of the

2002 Guide for the Design of New and Rehabilitated

Pavement Structures: Phase II, Web page. http://

apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?

ProjectID=218.

64.	 “AASHTOWare® Pavement ME Design” Web page.

http://www.aashtoware.org/pavement/pages/default.

aspx.

65.	Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009 (FHWA-RT10-071). Federal Highway Administration, McLean, VA,

2010, p. 12. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/10071/

10071.pdf.

	 66.	 “About the Data Analysis Working Group (DAWG)”

Web page. http://www.trb.org/PolicyStudies/

AbouttheDataAnalysisWorkingGroupDAWG.aspx.

67.	 “International Contest on LTPP Data Analysis”

Web page. http://www.fhwa.dot.gov/research/tfhrc/

programs/infrastructure/pavements/ltpp/index.cfm.

68.	 “2012 ASCE-LTPP International Data Analysis Contest

Award,” LTPP Newsletter, Vol. 9, No. 1, Winter 2013

(FHWA-HRT-13-055), p. 3. https://www.fhwa.dot.gov/

publications/ltppnews/13055.pdf.

69.	U.S. Statutes at Large 112 (1998): 107–509.

Transportation Equity Act for the 21st Century.

70.	LTPP Product Plan (FHWA-RD-01-086). Federal

Highway Administration, McLean, VA, 2001, p. 3.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/01086/01086.pdf.

71.	Long-Term Pavement Performance Program:

 Accomplishments and Benefits 1989–2009 (FHWA-RT10-071). Federal Highway Administration, McLean, VA,

2010. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/10071/10071.pdf.

See also Summary Report (FHWA-HRT-10-072) at

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/10072/10072.pdf.

72.	 “LTPP Pooled Fund Study Update,” LTPP Newsletter, 

vol. 3, no.2 (Spring 2007), pp. 1–3. http://www.fhwa.dot.

gov/publications/ltppnews/07047.pdf.

73.	Rigid Pavement Design Software: A New Tool for

Improved Rigid Pavement Design (Product Brief ) 

(FHWA-RD-99-129). Federal Highway Administration,

McLean, VA, May 1999. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/99129/99129.pdf.

74.	M. Swanlund. “Rigid Pavement Designing Goes

Microsoft Excel,” Research and TechnologyTransporter, 

May 1998. http://www.fhwa.dot.gov/publications/

transporter/98may/index.cfm#pavements.

75.	 “LTPPBind Simplifies Superpave Binder Selection,”

Focus, February 1999. http://www.fhwa.dot.gov/

publications/focus/99feb/ltppbind.cfm.

76.	 “FHWA Pavement Performance Research Saves $50

Million Annually in Highway Construction Costs.” 

Press Release. U.S. Department of Transportation, 

Office of Public Affairs, Oct. 30, 2001. http://www.fhwa.

dot.gov/pressroom/fhwa0135.cfm.

77.	 S. Alavi, T. Merport, T. Wilson, J. Groeger, and A. López.

LTPP Materials Characterization Program: Resilient 

Modulus of Unbound Materials (LTPP Protocol P46)

Laboratory Startup and Quality Control Procedure 

(FHWA-RD-96-176). Federal Highway Administration,

McLean, VA, January 1997. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/96176/96176.pdf.

78.	Long-Term Pavement Performance Protocol P46: 

Resilient Modulus of Unbound Granular Base/Subbase 

Materials and Subgrade Soils. Federal Highway Administration, McLean, VA, August1996. http://www.fhwa.
10: Turning LTPP Data INTOESU

dot.gov/publications/research/infrastructure/pavements/

ltpp/P46/P46.pdf.

79.	J. L. Groeger, G. R. Rada, and A. Lopez. “AASHTO

T307—Background and Discussion,” Resilient Modulus 

Testing for Pavement Components, ASTM STP 1437. 

G. N. Durham, W. A. Marr, and W. L. DeGroff, Eds. 

ASTM International, West Conshohocken, PA, 2003.

80.	Protocol P07: Test Method for Determining the Creep 

Compliance, Resilient Modulus and Strength of Asphalt 

Materials Using the Indirect Tensile Test Device,Version 1.1.

Federal Highway Administration, McLean, VA, August

2001. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/ProtocolP07/

ProtocolP07.pdf.

81.	 “AASHTOWare® Pavement ME Design” Web page.

http://www.aashtoware.org/pavement/pages/default.

aspx.

82.	LTPP Computed Parameter: Dynamic Modulus 

(FHWA-HRT-11-018), Federal Highway Administration, McLean, VA, November 2010. www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/11018/11018.pdf.

83.	Y. J. Jiang, O. I. Selezneva, and G. Mladenovic.

Researcher’s Guide to the Long-Term Pavement Performance Layer Thickness Data (FHWA-RD-03-040).

Federal Highway Administration, McLean, VA, July

2002. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/reports/03040/.

84.	 “Pavement Treatment Effectiveness, 1995 SPS-3 and

SPS-4 Site Evaluations, National Report” (TechBrief; 

FHWA-RD-97-029). Federal Highway Administration,

McLean, VA, June 1997. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/97029/97029.pdf.

85.	D. A. Morian, J. A. Epps, and S. D. Gibson. PavementTreatment Effectiveness, 1995 SPS-3 and SPS-4 Site 

EvaIuations, National Report (FHWA-RD-96-208).

Federal Highway Administration, McLean, VA, May

1997. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/96208/96208.pdf.

86.	D. A. Morian, S. D. Gibson, and J. A. Epps. Maintaining

Flexible Pavements—The Long-Term Pavement 

Performance Experiment: SPS-3 5-Year Data Analysis

(FHWA-RD-97-102). Federal Highway Administration,

McLean, VA, March 1998. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/97102/97102.pdf.

87.	D. A. Morian, S. D. Gibson, and J. A. Epps. Concrete 

Pavement Maintenance Treatment Performance Review: 

SPS-4 5-Year Data Analysis (FHWA-RD-97-155).

Federal Highway Administration, McLean, VA, July

1998. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/97155/97155.pdf.

88.	T. P. Wilson, K. L. Smith, and A. R. Romine. Materials

and Procedures for Rapid Repair of Partial-Depth Spalls 

in Concrete Pavements—Manual of Practice (FHWA-RD99-152). Federal Highway Administration, McLean, VA,

June 1999. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/99152/

99152a.pdf.

89.	T. P. Wilson and A. R. Romine. Materials and Procedures 

for Repair of Potholes in Asphalt-Surfaced Pavements—

Manual of Practice (FHWA-RD-99-168). Federal

Highway Administration, McLean, VA, June 1999.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/99168/99168.pdf.

90.	L. D. Evans, K. L. Smith, and A. R. Romine. Materials and

Procedures for Repair of Joint Seals in Portland Cement 

Concrete Pavements—Manual of Practice (FHWA-RD99-146). Federal Highway Administration, McLean, VA,

June 1999. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/99146/

99146.pdf.

91.	K. L. Smith and A. R. Romine. Materials and Procedures 

for Sealing and Filling Cracks in Asphalt-Surfaced 

Pavements—Manual of Practice (FHWA-RD-99-147).

Federal Highway Administration, Washington, DC, 

June 1999. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/99147/

99147a.pdf.

92.	J. S Miller and W. Y. Bellinger. Distress Identification 

Manual for the Long-Term Pavement Performance 

Program (5th rev. ed.; FHWA-HRT-13-092). Federal

Highway Administration, McLean, VA, May 2014.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/13092/13092.pdf.

93.	LTPP Product List (FHWA-HRT-06-119). Federal

Highway Administration, McLean, VA, 2006.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/06119/06119.pdf.

94.	Falling Weight Deflectometer (FWD) Calibration

Center and Operational Improvements Web page. 

http://www.pooledfund.org/Details/Study/28.

95.	L. H. Irwin, D. P. Orr, and D. Atkins. FWD Calibration 

Center and Operational Improvements: Redevelopment 

of the Calibration Protocol and Equipment (FHWAHRT-07-040). Federal Highway Administration,

McLean, VA. October 2011 http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07040/07040.pdf.

96.	L. H. Irwin, D. P. Orr, and D. Atkins. Final Report: Task 

Order #09-001. Federal Highway Administration, 

McLean, VA, April 2011. http://www.pooledfund.org/

Document/Download/2706.
226 THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

97.	R 32-09, “Calibrating the Load Cell and Deflection

Sensors for a Falling Weight Deflectometer,” Standard 

Specification for Transportation Materials and Methods 

of Sampling and Testing, Part 1B: Specifications. 

Association of State Highway and Transportation 

Officials, Washington, DC, 2009.

98.	AASHTO R 32-11, Standard Recommended Practice for

Calibrating the Load Cell and Deflection Sensors for a 

Falling Weight Deflectometer. American Association 

of State Highway and Transportation Officials, 

Washington, DC, 2011. http://www.techstreet.com/

products/1816111.

99.	Calibrating the Falling Weight Deflectometer Video

Web page. http://www.fhwa.dot.gov/multimedia/

research/infrastructure/calibration/index.cfm. 

100.	Improving the Quality of Pavement Profiler Measurement Web page. http://www.pooledfund.org/Details/

Study/280.

101.	AASHTO M 328-10, Standard Equipment Specification

for Inertial Profiler. American Association of State 

Highway and Transportation Officials, 2010. http://

www.techstreet.com/products/1751146.

102.	AASHTO R 56-10, Standard Practice for Certification

of Inertial Profiling Systems. American Association 

of State and Highway Transportation Officials, 2010.

http://www.techstreet.com/products/1751346.

103.	AASHTO R 57-10, Standard Practice for Operating

Inertial Profiling Systems. American Association of 

State and Highway Transportation Officials, 2010.

http://www.techstreet.com/products/1751366.

104.	AASHTO R 54-10, Standard Practice for Accepting

Pavement Ride Quality When Measured Using Inertial 

Profiling Systems. American Association of State and 

Highway Transportation Officials, 2010. http://www.

techstreet.com/products/1751306.

105.	“ProVAL Produces a Smoother Ride in Ohio,” Focus

(FHWA-HRT-07-015), July 2007, http://www.fhwa.dot.

gov/publications/focus/07jul/02.cfm.

106.	“ProVAL” Web site. http://www.roadprofile.com.

107.	M. E. Hallenbeck, O. I. Selezneva, and R. Quinley.

Verification, Refinement, and Applicability of Long-Term 

Pavement Performance Vehicle Classification Rules

(FHWA-HRT-13-091). Federal Highway Administration, McLean, VA, November 2014. http://www.fhwa.

dot.gov/publications/research/infrastructure/

pavements/ltpp/13091/13091.pdf.

108.	Long-Term Pavement Performance (LTPP) Specific

Pavement Study (SPS) Traffic Data Collection Web 

page. http://www.pooledfund.org/Details/Study/123.

109.	AASHTO M 331-13, Standard Specification for Smoothness of Pavement in Weigh-in-Motion (WIM) Systems. 

American Association of State Highway and Transportation Officials, 2013. http://www.techstreet.com/

products/1864192.

110.	Implementation of ProVAL OWL: A Tech Brief. http://

www.roadprofile.com/download/Implementation-ofOWL.pdf.

111.	 “ProVAL” Web site. http://www.roadprofile.com.

112.	W. H. Temple. Long-Term Pavement Performance

Committee Letter Report (Letter No. 31), Feb. 12, 2013,

pp. 5-6. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_31.pdf.

	113.	O. I. Selezneva and M. Hallenbeck. Long-Term Pavement Performance Pavement Loading User Guide 

(LTPP PLUG) (FHWA-HRT-13-089), Federal Highway

Administration, McLean, VA, October 2013. http://

www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/13089/13089.pdf.

114.	“LTPP–PLUG: Plug Your Traffic Loading Data Gaps.”

Focus (FHWA-HRT-13-013), May 2013. http://www.

fhwa.dot.gov/publications/focus/13may/13may02.cfm.

115.	TPF-5 (013), Effect of Multiple Freeze-Thaw Versus

Deep Frost Penetration on Pavement Performance Web 

page. http://www.pooledfund.org/Details/Study/2.

116.	N. Jackson and J. Puccinelli. Long-Term Pavement 

Performance (LTPP) Data Analysis Support: National 

Pooled Fund Study TPF-5(013): Effects of Multiple Freeze 

Cycles and Deep Frost Penetration on Pavement 

Performance and Cost (FHWA-HRT-06-121), Federal

Highway Administration, McLean, VA, November

2006. http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/06121/06121.pdf.

117.	S. M. Karamihas and K. Senn. Curl and Warp Analysis of 

the LTPP SPS-2 Site in Arizona (FHWA-HRT-12-068).

Federal Highway Administration, McLean, VA,

December 2012. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/12068/12068.pdf.

118.	LTPP 1998 Year in Review (FHWA-RD-99-111) Web

page, 1999. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/98year.cfm.

119.	Key Findings From LTPP Analysis: 1990–1999 

(FHWA-RD-00-085) Web page, 2000. http://www.

fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/key.cfm. 

120.	Key Findings From LTPP Analysis 2000–2003 

(FHWA-HRT-04-032). Federal Highway Administration, McLean, VA. n.d. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/ltpp/

reports/04032/04032.pdf.
10: Turning LTPP Data INTOESU

121.	Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009 (FHWAHRT-10-071). Federal Highway Administration,

McLean, VA, 2010. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/10071/10071.pdf.

122.	Long Term Pavement Performance Project Laboratory 

Materials Testing and Handling Guide (FHWAHRT-07-052), Federal Highway Administration,

McLean, VA, 2007. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/07052/07052.pdf.

123.	C-L Wu, G. R. Rada, A. Lopez, and Y. Fang. “Accuracy

of Weather Data in Long-Term Pavement Performance 

Database.” Transportation Research Record: Journal 

of the Transportation Research Board, vol. 1699,

pp. 151–159. Jan. 24, 2007. http://trb.metapress.com/

content/515x6727v2m8m897/fulltext.pdf.

124.	V. P. K. Ganesan, S. M. Stoffels, J. Arellano, D. Morian.

“Use of LTPP Data to Verify the Acceptance Limits

Developed for Penndot Pavement Distress Data.” 

Improving Pavements With Long-Term Pavement 

Performance: Products for Today and Tomorrow

(FHWA-HRT-06-109), J. Arellano et al., eds. Federal

Highway Administration, McLean, VA, September

2006, pp. 21–38. http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/

ltpp/06109/06109.pdf.

125.	R. W. Perera and S. D. Kohn. Quantification of Smoothness Index Differences Related to Long-Term Pavement 

Performance Equipment Type (FHWA-HRT-05-054). 

Federal Highway Administration, McLean, VA,

September 2005. http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/

ltpp/05054/05054.pdf.

126.	H. Yin, S. M. Stoffels, and C. A. Antle. “Profile Data

Variability in Pavement Management: Findings and

Tools from LTPP.” Airfield and Highway Pavement: 

Meeting Today’s Challenges with Emerging Technologies

(Proceedings of the 2006 Airfield and Highway

Pavements Specialty Conference), Imad L. Al-Qadi, 

ed., pp. 984–95. American Society of Civil Engineers,

Reston, VA, 2006. http://dx.doi.org/10.1061/

40838(191)83.

127.	R. N. Stubstad, S. D. Tayabji, and E. O. Lukanen. LTPP

Data Analysis: Variations in Pavement Design Inputs. 

NCHRP Web Document 48 (Project 20-50[5]):

Contractor’s Final Report. National Cooperative 

Highway Research Program, Transportation Research 

Board, National Research Council, Washington, DC, 

June 2002 (Web document). http://onlinepubs.trb.org/

onlinepubs/nchrp/nchrp_w48.pdf.

128.	O. Selezneva, J. Jiang, and S. D. Tayabji. Preliminary 

Evaluation and Analysis of LTPP Faulting Data—

Final Report (FHWA-RD-00-076). Federal Highway

Administration, McLean, VA, June 2000. http://www.

fhwa.dot.gov/pavement/pub_details.cfm?id=66.

129.	U.S. Department of Transportation Research, 

Development, and Technology Strategic Plan Fiscal 

Year 2013–2018. U.S. Department of Transportation, 

Research and Innovative Technology Administration, 

Washington, DC, September 2013, p. 31. http://www.

rita.dot.gov/rdt/sites/rita.dot.gov.rdt/files/rdt_

strategic_plan_2013.pdf.

130.	“Highway Performance Monitoring System (HPMS)”

Web page. http://www.fhwa.dot.gov/policy

information/hpms.cfm.

131.	Highway Performance Monitoring System Field Manual. 

Federal Highway Administration, Washington, DC, 

March 2014. http://www.fhwa.dot.gov/policy

information/hpms/fieldmanual/HPMS_2014.pdf.

132.	K. O’Toole, M. Alam, and L. Titus-Glover. Enhancement

of the Pavement Health Track (PHT) Analysis Tool, Final 

Report. Federal Highway Administration, Washington, 

DC. September 2013, pp. 5, 15, 27–60. http://www.fhwa.

dot.gov/pavement/healthtrack/pubs/technical/

technical.pdf. 

133.	Long-Term Pavement Performance Program:

 Accomplishments and Benefits 1989–2009 (FHWA-RT10-071). Federal Highway Administration, McLean, VA,

2010, p. 20. http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/10071/10071.

pdf. See also Summary Report (FHWA-HRT-10-072)

at http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/10072/10072.pdf.
228    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Some of the key lessons learned during the LTPP program 

may benefit future managers of the program and others 

who are pursuing long-term research goals. 

© Joseph Sohm/Shutterstock.com
11: LESSONS LEARNED FROM THE LTPP PROGRAM    229

Lessons Learned From the LTPP Program

11

INTRODUCTION

The task of the LTPP program managers has been to 

build and maintain a viable, reliable, and credible longterm research program that can provide highway agencies with the resources they need to better manage 

their aging roadways. These resources include the data 

and tools needed to develop better pavement design 

methods and maintenance and rehabilitation procedures. In the beginning, the LTPP program was not an 

“easy sell.” There were many obstacles as implementation began, and challenges continue to arise along the 

way. Although the problems have sometimes been 

painful to work through, valuable lessons have been 

learned by everyone in the program. 

This chapter highlights some of the most pressing 

issues encountered since the LTPP program was 

authorized by Congress in 1987 and the ways in which 

Through the process of planning the experiments and executing the data collection activities in the LTPP 

program, many lessons have been learned. While the technical research findings are interesting and useful, 

the lessons learned and observations along the way are equally interesting and potentially useful.

these issues have been addressed while keeping in 

mind the goal and objectives established for the program.1,2 This written account presents some of the key 

lessons learned over the years with the hope that 

others planning short- or long-term research programs 

can benefit from these experiences. 

QUESTION ALL ASSUMPTIONS

One of the key elements to any successful program, 

short- or long-term, is preparation. The early LTPP 

program planners and managers provided a solid foundation on which to build the program. Their effort is 

evident not only in the longevity of the program, but 

also in how the program has contributed to the pavement community. The early planners, however, could 

not anticipate every challenge that would need to be 
230    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

“You did then what you knew how to do. 

When you know better, you do better.”

Attributed to Dr. Maya Angelou

Test Site Information Assumptions

When the program started, it was widely believed by 

the organizers that general information about the test 

sites proposed for the General Pavement Study experiments was readily available. Field visits and exploration of candidate project locations, however, showed 

that specific information about material types and 

properties, layer thicknesses, construction dates, traffic, and other test site details was difficult to obtain. 

Furthermore it was discovered that some plan sheets 

were not nearly as accurate as was expected. These 

findings resulted in shuffling sites between experiments or removing them from the program altogether. 

Although a body of knowledge did generally exist, it 

was usually scattered in various offices or divisions 

within the highway agency. The autonomy of many 

highway agency departments and divisions resulted in 

communication and coordination challenges in finding 

the historical data for the LTPP test sites. In some 

agencies, interaction between the district or field offices and the main office was limited, and project records 

were difficult to find. Often they were thought to be in 

transit, when they were actually stored in one place or 

the other, and no one really knew where to look. The 

LTPP program made a concerted effort to collect the 

missing data by working at times in the highway agency office reviewing plan sheets and inventory documents, and completing the necessary forms to include 

the data in the LTPP database. There are still some test 

sites where the historical data remain incomplete 

despite the program working closely with the agencies 

to collect this information.

Traffic Data Assumptions

Collection of climatic, materials, and performance 

time-history data was useful, but of limited impact if 

the progression of pavement condition could not be 

tied to the traffic loading. During planning, some major 

and grossly inaccurate assumptions were made in the 

traffic area.

First, it was assumed that wherever sites were 

selected, historical traffic information would be readily 

available. Second, since highway agencies routinely 

collected traffic data as part of their normal operations, 

addressed by the program's managers, partners, and 

contractor staff. Early assumptions were that selection 

of site locations would be relatively easily accomplished using highway agency information from asbuilt plans and pavement management systems. As 

implementation of the program began, the highway 

research community learned that we did not know 

nearly as much about the state of the pavements existing on the roadways as we thought we knew.

Although the idea of advance planning can be 

applied to each lesson discussed in this chapter, this 

section speaks to the issue of not having adequate 

information on which to proceed with implementation. Specifically, the program found that in some cases 

the basic design, construction, and maintenance information and other test section data needed to populate 

the LTPP database were unavailable or did not accurately reflect the characteristics of the test section. © William Perugini/Shutterstock.com
it was assumed that they would be able to instrument 

the selected test sites to provide monitored data for 

future years. And, third, it was assumed that equipment would be available to accurately collect weigh-inmotion (WIM) data at a reasonable cost. As a result, 

little consideration was given to the need for traffic 

data during the site selection process. No consideration was given to the availability of historical information until after the fact. No consideration was given to 

the utilities and pavement conditions required for 

installation and proper operation of data collection 

equipment. These assumptions created a serious road 

block for the LTPP program until they were resolved 

by the traffic pooled-fund study (chapter 7), initiated 

following the Campaign for Program Improvement 

discussed below.

ESTABLISH CLEAR PRODUCT

development E

Those who managed the LTPP program and those who 

supported the program in its infancy understood that 

several years would be needed to develop data collection protocols, identify and test the data collection 

equipment, and build the database. All of these program activities were essential for the future development of useful and usable tools and products to address 

highway agencies’ needs. The planners also knew that 

many years would need to pass before sufficient data 

were collected to produce any meaningful results. This 

inevitable delay was a problem because results were 

urgently needed by the highway agency partners.

The expectation that products would not be quickly 

available was not communicated to the highway agency partners early on and probably not often enough, 

resulting in misunderstandings and frustration. The 

LTPP program has since improved its communication 

with the highway agency partners by providing frequent program updates through its newsletter and 

Webinars. In addition, the program has performed and 

initiated data analysis studies that have the potential to 

address some of the pressing needs of the agencies, 

such as the study on effectiveness of maintenance and 

rehabilitation options.3

 Many other examples are 

described in the data analysis and product descriptions 

in chapter 10. As monitoring continues on in-service 

pavement structures, more data are collected, and 

more analyses are conducted, additional knowledge, 

tools, and useful products will result to help the entire 

highway community. 

MANAGE FROM THE CENTER TO SUCCEED

The LTPP program requires a centralized management structure to effectively and efficiently perform 

the activities and functions of the program. The benefits from such a structure were first realized when the 

program was managed by the Strategic Highway 

Research Program (SHRP) of the National Research 

Council in the early years, and since then by the Federal Highway Administration (FHWA). Operating such 

a large program also requires collaboration among 

many partners in different types of organizations and 

among different levels of management, which both 

SHRP and FHWA have successfully supported. Direct 

communication and close coordination among multiple parties is only possible through a centralized 

management structure that can provide the funding 

and personnel resources needed to properly carry out 

the program’s many activities. 

Dedicated Funding

Efficient execution of a program such as LTPP 

requires considerable planning and a predictable, 

uninterrupted stream of funding. Given that highway 

bill funding usually lasts for a period of 4 to 5 years, 

and is renegotiated each time, the program has had to 

survive the passage of five highway bills over its more 

than 25 years of existence. With each new highway 

bill, LTPP program staff had to justify the value of the 

program and the logic of continuing its funding. 

Although the program has enjoyed continuous funding, there has been considerable disruption and 

uncertainty as to how much money would be available and when. In response to these situations, the 

program’s managers have learned to adjust its short11: LESSONS LEARNED FROM THE LTPP PROGRAM    231
232    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

and long-term program plans and priorities, which 

are set based on multiple levels of possible funding. 

The reality, however, is that such funding uncertainties have led to missed opportunities in pavement 

performance monitoring and to the delay of critical 

activities such as correcting program weaknesses and 

addressing emerging pavement-engineering needs.

Central management of the LTPP program has 

provided the flexibility to strategically carry out the 

program activities during funding reductions. For any 

long-term research program, it is important to seek 

dedicated and uninterrupted funding.

Dedicated LTPP Program Staff

The program has had the good fortune to have nearly 

the same core staff for much of its 25-plus years, which 

is extraordinary. The program, however, has seen its 

share of changes in leadership and staffing levels, 

resulting in changes in the approach to moving the 

program forward. 

During the years when the LTPP study was part of 

SHRP, the challenge faced by the SHRP-LTPP management was finding the right “home” for the pavement research study where the work would continue 

after the SHRP program ended in 1992. Having a vested 

interest in long-term pavement monitoring well before 

the LTPP program was implemented, FHWA was 

identified as the most logical “home” for the program 

to live out its intended purpose. However, in more 

recent years given the uncertainty of the future of the 

LTPP program, the partners have feared that the program functions—particularly the housing of the database and the core program staff—would be dispersed 

across different offices within FHWA.

The highway agency and industry partners strongly 

voiced their concerns that decentralization of the 

LTPP program could result in neglect, lack of communication, the inability to properly manage critical activities remaining to be done, and a gradual loss of interest 

in the program itself.4 One such example can be shown 

in the transfer of LTPP product development from the 

core staff to another office within FHWA, which has 

left the program staff not knowing the status or delivery of products to the highway community. While 

efforts have been made to correct this problem, it is still 

a concern and not the ideal solution for the program. In 

response to the partners’ concerns, FHWA management has committed to provide the staff required to 

fulfill the LTPP program’s needs. 

The program’s history has shown that having a dedicated program staff provides coherency, close communication, and clear and firm control over priorities. 

Having the support of core staff through this centralized management structure, the LTPP program has 

been able to collect consistent, high-quality data. A 

case in point is the resolution of the Specific Pavement 

Studies (SPS) materials and traffic data gaps as discussed in chapter 7. SPS materials testing and traffic 

data collection were the responsibility of the individual 

highway agencies. The agencies made good faith 

efforts to discharge these responsibilities, but the dispersion of responsibility resulted in problems with 

timeliness, completeness, and consistency in the data 

provided. For this reason, efforts to correct the SPS 

materials and traffic data gaps were managed centrally 

and have successfully resulted in these data gaps being 

filled. Achieving consistent, high-quality data requires 

central management.

Having a dedicated staff to work on the LTPP program has been ideal, as demonstrated in the many 

accomplishments described in this report. The program’s staff, however, has not always been in agreement. 

Each staff person has had the best interest of the program in mind, but misunderstandings, disagreements, 

and frustrations have existed among members of the 

LTPP Team as would occur with any complex operation. In 1997, at an internal LTPP meeting, members of 

the LTPP program staff and its contractor and loaned 

staff discussed and positively resolved this issue by 

agreeing to operate under the “LTPP Norms” (see sidebar). This signed resolution by the parties emphasizes 

the importance of putting differences aside by being 

respectful and staying focused on moving forward. The 

resolution also shows the importance of people with different backgrounds, expertise, and interests coming 

together to work toward the good of the whole program. 

Synergy at its best was demonstrated by this group and 

has since continued within the LTPP program.
11: LESSONS LEARNED FROM THE LTPP PROGRAM    233
234    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

Dedicated Highway Agency Staff

There were a number of meetings at the beginning of 

the program to inform participating highway agencies 

of plans and to solicit their support for activities. Given 

the support of highway agencies through the American 

Association of State Highway Transportation Officials 

(AASHTO) and the Transportation Association of Canada, senior management staff supported the program 

objectives, which trickled down to mid-level managers 

who provided their support as directed. Under SHRPLTPP management, each highway agency was asked to 

provide an LTPP State Coordinator who would serve 

as the liaison between the agency and the LTPP program office. This practice continues under FHWA’s 

leadership.

Over time, agency personnel changed positions or 

left agency employment as a result of career moves and 

retirement. This attrition meant that those who supported the program at the outset were no longer available to encourage continued participation. LTPP 

program resources were continually required to educate those moving into positions of influence, and to 

encourage them to continue support for the program. 

The effect of attrition was especially felt in the solicitation of candidate projects for the SPS experiments. 

Participation in the SPS experiments, which involved 

new construction, was costly, and results were not to 

be realized for many years. Obtaining and maintaining 

enthusiastic support under these circumstances was 

extremely difficult. 

Efforts to support the program were all voluntary, 

with agency staff already committed to performing 

their regular job duties, so it was often difficult for 

them to make time for the tedious and time-consuming 

tasks involved in researching available test sections for 

site selection, locating historical data, or planning construction of SPS projects. The LTPP program had its 

own way of doing things, with specific test protocols, 

design constraints suited to SPS construction, and data 

forms requiring detailed information about discrete 

points on the roadway where very little specific information existed. In order to fully support LTPP program activities, agencies had to make some adjustments 

to their normal operations. These changes were met at 

times with some resistance. As the program matured 

and the expectations of the highway agency were better defined, the LTPP program became a higher priority for the agency staff.

In addition, Federal funds for the program cover 

only part of its real cost, and highway agency staff and 

resources have been needed to assist in meeting the 

LTPP objectives. Some agencies have even allotted 

funding in their budgets to support LTPP program 

activities such as providing traffic control for data collection, materials sampling, or construction activities; 

installing instruments to measure traffic; and performing laboratory materials testing.

REASSESS PERIODICALLY

Since 1987, the LTPP program managers have been 

hard at work establishing the experiments, preparing 

for implementation of the program, identifying and 

collecting the right pavement performance data for 

future data analysis and product development, and 

developing a secure database to store the data. Given 

these and other key program activities, the program 

managers have learned to pause and reflect on the condition of the program and to identify what improvements can be and should be made. Such periodic 

assessments or reviews of the state of the program 

have happened through internal meetings, meetings 

with the program partners through the expert task 

group committee structure, and national meetings. 

This section focuses on the information gathered from 

key national meetings that have helped to make the 

LTPP program what it is.

SHRP Midcourse Assessment Meeting

Denver, Colorado (August 1990)

More than 400 invited representatives of highway agencies, industry, and research organizations gathered in 

Denver, Colorado, August 1–3, 1990, to take a close look 

at SHRP’s progress to date, and to suggest adjustments 

that would maximize the potential for delivery of immediately useful products when SHRP would end in 1992. 

The presentations looked at the strengths and weaknesses of current planning, and sought to gain input that 

would ensure that the LTPP program would remain in 

line with the stated goal and objectives. There was also a 

heightened awareness of international participation, as 
presentations provided input from international perspectives, and data analysis topics provided insight to 

the potential capabilities of the very early SHRP-LTPP 

data. The proceedings from this assessment meeting 

were published as SHRP Report No. 91-514, as a collection of the LTPP papers and presentations.5

 

States Convey Their Needs to LTPP

Interviews at Eight State Highway Agency Offices 

(1995)

The AASHTO Task Force on SHRP Implementation 

provided valuable assistance to the LTPP program by 

making arrangements for the program manager at the 

time to meet with eight senior State officials (at least 

one from each of the AASHTO regions) in order to 

hear their pavement performance needs. The purpose 

of these discussions was to obtain guidance on the 

future direction of the program and to get an understanding of the States’ expectations on the program 

deliverables.

The 1-hour, face-to-face meetings initiated by the 

LTPP program took place in 1995 in Arkansas, California, Kansas, Maryland, New York, Pennsylvania, Texas, 

and Wisconsin. These senior State officials revealed 

that their active participation in the program was 

largely driven by their expectations that the tools and 

knowledge produced by the program would yield 

answers to and address issues such as the ones listed 

below:6

•	 What maintenance treatments are effective? What

do they cost?When should they be used? How much

do they extend the life of the pavement?

•	 What is the best rehabilitation design for a given

road structure? How can we minimize the risk of

our choice? What are the life-cycle costs?

•	 We need better designs, developed from models

that predict with assurance that the newly built or

reconstructed pavements based on these designs 

will last a specified number of years.

•	 We need dramatic improvements in technology, not

incremental changes.

•	 What performance trends are discernable from the

LTPP data?

•	 We need improvements in WIM technology. We

need to measure equivalent single-axle loads more 

accurately. 

These thoughts strongly echo those cited in the “Blue 

Book”7 and “Brown Book,”8 but have a more tangible 

feel. In essence, the States want useful engineering tools 

and an enhanced knowledge base on which to base 

management and engineering decisions—their highpriority needs in terms of answers from the LTPP program. The program fell short of this expectation because 

initially the program was focused on data collection. 

Little effort was put on product development, which has 

had a negative impact on the program’s image. To understand why some pavements provide superior service 

beyond a 20-year design life, monitoring must be 

extended beyond 20 years, but States needed answers 

immediately. This posed a problem then and in some 

ways it still does now. Although many valuable data 

analysis studies have been performed by the LTPP program which have resulted in useful products (that would 

not have otherwise been developed) that have benefited 

the States and the broader highway community, there 

are still unanswered questions posed by the States that 

need resolution.

LTPP National Meeting

Irvine, California (March 1996)

The FHWA assumed stewardship of the LTPP program in 1992, when SHRP ended. Collection, management, and analysis of the data, and planning for 

continued operations moved seamlessly ahead during 

the transition from SHRP to FHWA.9 In recognition of 

the fact that the LTPP program was approaching the 

midpoint of planned pavement monitoring, it was prudent to plan a national meeting where participants 

could learn from those that had made use of the data 

collected to date, and provide input on any needed 

midcourse corrections.

The LTPP National Meeting was held at the TRB 

facilities in Irvine, California, March 26–28, 1996. This 

meeting drew participation from most highway agencies, industry, academic institutions, and FHWA. Presentations provided background information on the 

status of the various aspects of the program, and on 

results of data analyses. Breakout groups discussed 

program needs and high priority objectives.

Throughout the course of the meeting it was recognized that major gaps existed in the LTPP database, 

predominantly in traffic and materials test data. Those 

11: LESSONS LEARNED FROM THE LTPP PROGRAM    235
236    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

in attendance agreed that these critical data gaps must 

be filled if the program was to deliver on its stated 

objectives. It was also recognized that of the pavement 

types being studied, highway agencies were most interested in the result of rehabilitation studies, since the 

bulk of their construction efforts were in maintenance 

and rehabilitation of existing roadways. Concerns were 

expressed about studies focusing on pavement technologies and material types that were no longer used. 

All of these observations and many more provided 

strong feedback to the LTPP program managers, giving 

them much clearer direction as to what they should 

focus their efforts on.

LTPP Program Focus: Assessment and

Corrective Actions

In 1996, as the LTPP program was approaching the 

10-year mark, FHWA decided to embark on an overall 

assessment to review the program goal and objectives, 

and to see in what direction the program was really 

heading. This assessment was accomplished by evaluating the impacts of deviations from the program’s 

plans, the number and types of test sections ultimately 

included for monitoring, data collection deficiencies, 

and resources. The ultimate objective of the assessment was to develop a revised strategic plan that 

focused on high-payoff products that would meet 

agencies’ needs, improve program efficiency, and provide better quality data for product development.10 

The assessment was conducted by a team composed 

of LTPP program and contractor staff, in concert with 

a special peer review subcommittee made up of highway agencies, TRB, and AASHTO representatives. In 

addition, through the TRB advisory mechanism, stakeholders in agencies were contacted to obtain input on 

agency needs as related to the goal and objectives of 

the program established 10 years earlier.

Early on in the assessment it became evident that 

data quantity issues overshadowed other program considerations. Specifically, large data gaps in the LTPP 

database and questions regarding the data were identified, which precluded addressing other issues such as 

data quality and test section coverage. In turn, this issue 

led to concerns about the ability of the LTPP program 

to fully deliver on its intended goal and objectives.

The Campaign for Program Improvement (1997–1999)

As a result of the assessment in which data completeness 

and data improvement were identified as the highest priorities for the LTPP program to address immediately, a 

highly publicized “Campaign for Program Improvement” (often referred to as the Program Improvement 

Campaign) was initiated in 1997 with support from the 

TRB LTPP Committee.11 This 2-year campaign consisted 

of five interrelated tracks of activities:

•	 Operations Backlog.

•	 Test Section Classification.

•	 Monitoring Schemes.

•	 Analysis and Product Development Plan.

•	 Data Studies/Preliminary Analyses.

Special mention to the operations backlog track is 

given here since it was intended to address the gaps and 

questions regarding the data collected but not processed 

and entered into the LTPP database, which was identified as a major program issue during the assessment. 

Preliminary data resolution began in early 1998, and in 

April, when AASHTO passed a resolution seeking the 

agencies’ help in resolving the LTPP data issues, the 

effort began in earnest.12 As a result of the AASHTO resolution, face-to-face meetings similar to the ones held 

with the senior State officials in 1995, were held but this 

time with each individual agency during the summer of 

1998. In all, 60 meetings took place involving more than 

1,200 highway agency and FHWA personnel. These 

meetings led to the development and endorsement of 

agency action plans, and implementation of these plans 

resolved many of the LTPP data issues.

The 2-year Program Improvement Campaign significantly improved the LTPP program's ability to better 

deliver on its goal and objectives through several accomplishments:

•	 Cleared data processing backlog.

•	 Systematically assessed data availability and deficiencies.

•	 Initiated work to resolve deficiencies and obtain

needed data.

•	 Established framework for development ofimprovement quality measures.
•	 Revised monitoring guidelines in response to data

availability and importance of test sections to program priority goals.

•	 Developed a strategic plan for data analysis.

•	 Developed a product development plan linked to

data analysis.

•	 Established clear lines of feedback from analysis to

data collection activities to resolve data anomalies

and errors as they are identified.

•	 Initiated formal data studies.

•	 Rejuvenated highway agency commitment to the

program.

•	 Took actions to develop a plan for management of

ancillary data and data archival at the end of the

program.

The LTPP program learned about its strengths and 

weaknesses as a result of the campaign and this resulted in a fundamental shift in program operations and 

management. The campaign aligned the program with 

modern quality management principles and practices, 

and it brought needed focus to product development 

and data analysis, as identified in the list above. However, despite its many accomplishments and successes, 

it is important to note that at the conclusion of the Program Improvement Campaign, data issues remained to 

be resolved. In particular, large data gaps remained in 

the LTPP database in terms of the SPS traffic and materials data, which necessitated the development and 

implementation of action plans. These action plans are 

discussed in the following section. The LTPP program 

has been proactive in its assessment of itself, and has 

continued to take steps to improve the manner in 

which the program is managed. 

Major Data Resolution Initiatives

Due to budgetary restrictions early in the LTPP program, funding responsibility for traffic and materials 

data collection was assigned to the individual participating highway agencies. Although the highway agencies made a good faith effort to fulfill this responsibility 

at the LTPP test sites, problems of data quality and 

timely monitoring and testing arose. And while highly 

successful, the Program Improvement Campaign, 

which concluded in 1999, did not resolve these two 

major data issues that still existed at the SPS test sites. 

Consequently, in the early 2000s, the program undertook two major data resolution initiatives to address 

the traffic and materials data gap issues.

LTPP SPS Traffic Data Collection Pooled-Fund Study.

Traffic data collection within the LTPP program has 

always been a challenge, in large part because the associated technology has not lived up to the early expectation that it would be economically and technically 

feasible to install reliable WIM equipment at every 

LTPP test site. By the late 1990s it was clear that, as a 

consequence of mistaken assumptions about the availability of traffic data and the WIM equipment as 

described earlier in the chapter, traffic data were 

incomplete relative to original expectations. Complete, 

high-quality traffic data were available for some sites, 

while little or no traffic data were available for others. 

For the majority of LTPP test sites, traffic data availability fell somewhere in between.

Clearly, something had to be done with regard to the 

traffic data, particularly at the SPS projects, and it was. 

In response to the large SPS traffic data gap, the LTPP 

program, with support from the Expert Task Group 

(ETG) on LTPP Traffic Data Collection and Analysis, 

developed and implemented an action plan for closing 

the gap. Specifically, a pooled-fund study between the 

highway agencies and FHWA was initiated in 2001. 

The Long-Term Pavement Performance (LTPP) Specific Pavement Study (SPS) Traffic Data Collection 

Pooled-Fund Study, TPF-5(004), was designed to fill in 

existing data gaps and improve the quality and quantity 

of monitored traffic data for the SPS-1 (structural factors for flexible pavements), -2 (structural factors for 

rigid pavements), -5 (rehabilitation of asphalt concrete), 

-6 (rehabilitation of jointed Portland cement concrete), 

and -8 (environmental effects in the absence of heavy 

loads) projects. FHWA managed the study and oversaw 

the work of two independent contractors to resolve the 

traffic data gap. Although its implementation began 

later than anticipated due to various technical issues, in 

2003 the traffic pooled-fund study began to generate 

the high-quality data needed to close the traffic data 

gap. At least five years of research quality traffic data 

were collected during the study for 28 of the 84 SPS 

projects and are available in the LTPP database.

11: LESSONS LEARNED FROM THE LTPP PROGRAM    237
238  THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP program made a significant financial contribution toward the pooled-fund study, but the bulk of 

the funding came from contributions by the highway 

agencies. A majority of the highway agencies with SPS 

projects (28 of 38) participated in the study, and some 

highway agencies with no SPS projects also contributed, essentially making their funds available for the good 

of all. The traffic pooled-fund study ended in December 

2014, but the LTPP program has committed to continue 

collecting weight and classification data from as many 

of these projects as the budget will allow. As a result of 

this centralized data collection and review effort, a significant portion of the SPS traffic data gap was resolved, 

and the LTPP program is applying the methods from 

this initiative to collect traffic da ta at th e ne w LT PP 

warm-mix asphalt projects. See chapter 7 for more 

information about the traffic pooled-fund study. 

SPS Materials Action Plan. SPS materials data were 

collected by the highway agencies according to materials sampling and testing guidelines developed by the 

LTPP program and site-specific sampling plans adapted by the LTPP regional support contractors working 

closely with each highway agency. The State and Provincial highway agencies took responsibility for sampling and testing the materials from their respective 

SPS projects, with two exceptions: the LTPP program 

performed the resilient modulus testing of unbound 

and hot-mix asphalt materials and the coefficient of 

thermal expansion testing for Portland cement concrete layers. Under this primarily decentralized 

approach, data collection practices were not consistent 

among the highway agencies. This inconsistency was 

in contrast to the materials sampling and testing for the 

General Pavement Studies test sections, where the 

LTPP program performed all of the associated activities with support from the highway agencies.

The program assessment revealed that nearly 48 

percent of the required SPS materials test data were 

missing, which clearly limited the ability of the LTPP 

program to meet its goal and objectives. Starting in 

2002, the program, with support from the ETG on 

LTPP Materials Data Collection and Analysis, began 

taking steps to address the SPS materials data gaps. 

This effort led to the further pursuit of missing materials data from the responsible highway agencies, the 

search for missing data at the LTPP regional support 

contractor offices, and the acceleration of hot-mix 

asphalt and unbound granular resilient modulus testing 

by the LTPP laboratory contractor. An SPS materials 

data resolution action plan was developed to provide 

standard procedures for collecting and testing the samples. This plan, known within the program as the SPS 

Materials Action Plan, was specific to the SPS-1, -2, -5, 

-6 and -8 projects and addressed three major areas:

• Resolution of materials data gaps.

• Aging and new materials testing.

• Collection of materials samples.

A significant reduction in the missing SPS materials

data, from 48 percent to 35 percent, resulted from the 

efforts started in 2002, but large materials data gaps 

still existed and they needed to be addressed. Therefore in 2004 the LTPP program, with the support of 

the Materials ETG, updated the action plan and began 

a concerted effort to resolve the remaining materials 

data gaps. The updated Materials Action Plan, implemented in 2004, called for nearly 10,000 laboratory 

material tests and included nine major tasks.

The quality of the SPS materials test data was also 

investigated to determine the need for repeating tests 

performed by the highway agencies as part of the final 

action plan. Major findings from this investigation 

were that (1) the biggest difficulty in assessing the quality of the SPS materials data is the lack of data; and (2) 

where data are available, the majority met the criteria 

used in the quality review. Accordingly, the decision 

was made that repeat testing was not necessary and 

therefore did not have to be included in the action plan. 

Despite the financial challenges faced by the LTPP 

program, in 2008, the program successfully resolved 

approximately 90 percent of the missing SPS materials 

data issues.13 See chapter 7 for more information about 

the SPS Materials Action Plan.

LTPP SPS Workshop

Newport, Rhode Island (April 2000)

On April 27, 2000, the LTPP program held a workshop 

in Newport, Rhode Island, to discuss the status of the 

program’s SPS-1, -2, -5, and -6 experiments. Nearly 150 

participants were on hand to discuss the progress of 
these experiments, which were designed to explore how 

climate and cumulative traffic loading affect pavements 

of different compositions and cross sections. The LTPP 

contractor staff presented comparative studies on the 

performance of the test sections to date and the highway 

agencies presented their observations and opinions 

from the construction experience. There was active discussion about missing data, including traffic and materials information, and the critical need to obtain this 

information if the experiments were to be successful. 

The workshop provided yet another forum for the 

involvement of stakeholders in the program to voice 

opinions and observations, and to provide input for the 

planning and direction of LTPP program operations.

KEEP PARTNERS INFORMED

As discussed throughout this report, the LTPP program has benefitted from the close collaboration and 

collective efforts from different organizations, and also 

from the individual expertise from many individual 

professionals. Working in partnership with these organizations and professionals has always been integral to 

the program and began well before program implementation. However, during funding cuts that began in 

1998, the partners became concerned that keeping 

them informed was no longer a high priority of the 

program staff. The budget constraints resulted from 

highway legistations passed in 1998 and 2005 (see 

chapter 4).

The budget provided by these legislations was not 

able to meet every need of the LTPP program. So, some 

tough decisions were made by the program based on 

the budget given. One such decision was to not only 

reduce the frequency of meetings with the ETGs and 

the LTPP Committee, but to also reduce the number of 

ETGs from six to two. So, instead of meeting every 6 

months with six ETGs and the LTPP Committee to discuss the status and future work of the program, the 

LTPP Team began meeting annually with two ETGs 

and the LTPP Committee.

This was an uncomfortable time for both the LTPP 

program and the partners. Uncomfortable for the 

program because the managers thought they were 

making the right decisions at the time. Uncomfortable for the ETG and LTPP Committee members 

because they felt they were not being kept informed, 

and they were also frustrated that their input was not 

being sought to help in influencing the direction of 

the program, especially since the program was nearing the end of its planned 20-year data collection 

period. There was uncertainty as to whether or not 

the program would be extended beyond the 20 years 

even though hundreds of test sections still had not 

reached the end of their design life, and the LTPP 

database still needed to be further developed and 

maintained. It was vital that the partners through the 

LTPP Committee structure hear from the LTPP program what was being considered for the future and to 

be part of these discussions. 

As the LTPP Committee voiced their concerns, the 

LTPP program and FHWA’s senior management listened and made changes to correct the lack of communication between the program office and the 

partners.15,16 Since then, the semi-annual frequency of 

the face-to-face meetings has resumed. In addition, the 

LTPP Newsletter was established to keep the program 

partners informed during the time when meetings 

were not possible. The newsletter is still being distributed at regular intervals to hundreds of people across 

highway agencies, researchers, academia, and other 

interested parties.

The LTPP program knows that continued involvement of its stakeholders is vital to its ultimate success. 

Routine coordination and communication with participating highway agencies, for example, are of paramount 

importance—without their support, performance monitoring and other data collection activities on the LTPP

test sections would not be possible.

11: LESSONS LEARNED FROM THE LTPP PROGRAM  239

"There is a need for person to 

person communication, and for user 

involvement in technology transfer. 

The ways in which we do it are 

as important as doing it."

—Lynne Irwin, Cornell University14
DOCUMENT

The LTPP program has developed, written, and published thousands of formal and informal program documents over the years. The references cited in this very 

report show the magnitude and variety of communications produced and used by the program. The program 

staff has learned the importance of having a written 

account of the various decisions made, not only for 

those involved in working directly with the program 

but also for those who may want to learn about how the 

program is managed. To achieve high-quality data consistently throughout the United States and Canada, 

clear direction and guidance are needed by those collecting and processing the LTPP data. Having a written 

account of the program’s activities also provides future 

LTPP program managers and senior FHWA management with insight into the program. The permanent 

record of the program’s data collection procedures, 

calibration activities, and other important documentation used to manage the program will serve as valuable 

resources for the pavement industry for years to come. 

It is very important for any type of research program, 

long- or short-term, to have a plan to document its program along the way. 

PREPARE TO CHANGE WITH TECHNOLOGY

One of the frequent criticisms heard by the LTPP program managers was that the program studied “past” 

technology. The implication was that by the time sections were constructed and their performance had been 

monitored over a long period of time, the use of that 

material or construction technology would have evolved 

to the point where the findings were no longer appropriate to current practices. This potential problem is fundamental with a long-term study of any type. In the LTPP 

program, efforts were made to include a broad enough 

“inference space” of material properties and practices, 

such that results could be reasonably expected to reflect 

behaviors that would be encountered.

Another concern has been change in technology 

over time. Since the program began in 1987, there have 

been amazing advancements in electronics, equipment, and computing technologies. The program had 

to periodically update its pavement performance monitoring equipment and software as equipment became 

obsolete or worn out and as software was no longer 

supported. These changes each required updates in 

other areas and notifications in the resulting data to 

ensure that users were aware of the changes and their 

potential impacts on measurements. For example, the 

program has used four different pieces of equipment 

from three different vendors to collect longitudinal 

profile measurements. Although the end results should 

be the same, different electronic technologies and filtering techniques result in differences in the data. The 

LTPP program has conducted comparison and calibration activities for each equipment upgrade to minimize 

the impacts of such changes and noted the changes in 

the data set where appropriate to do so. In some cases, 

where equipment had not advanced to meet specific 

needs of the program, manufacturers adapted equipment to the program’s specifications. 

Data processing and communications equipment 

and software were another area where continuous 

effort and investment are needed to keep pace with 

change. As the LTPP database is the program’s principal operational tool, its most strategic product, and its 

legacy to future generations of highway researchers 

and practitioners, a paramount program priority has 

been to keep the Information Management System 

secure and current with computing and communications software and hardware. Over 25 years, the program has moved from magnetic tapes and floppy disks 

to centralized data entry and data user access via the 

Internet to keep the data accessible. Equipment and 

software have been upgraded several times. Particular attention is directed to system security, and backups of the entire database are performed routinely 

(see chapter 8). Long-term research efforts must be 

prepared to adapt to a changing technological world.

SUMMARY

Every chapter in this report tells part of the LTPP story. 

In this chapter, it was important to document some of 

the challenges so that others understand that the pro240    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
gram has not done things perfectly or made the right 

decisions all the time; mistakes and adjustments have 

been made. Perhaps others will learn from what has 

been done, and appreciate the effort, hard work, and 

dedication of those who have made the program better 

with each lesson mentioned in this chapter, lessons that 

were not mentioned, and lessons that will come as the 

LTPP program looks forward to future research efforts, 

which are discussed in the final chapter.

REFERENCES

 1. America's Highways: Accelerating the Search for 

Innovation (Special Report 202). Transportation 

Research Board, National Research Council, 

Washington, DC, 1984, p. 80. 

 2. Strategic Highway Program Research Plans, Final 

Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986, 

p. TRA-2-6.

 3. K. T. Hall, C. E. Correa, and A. L. Simpson. LTPP Data 

Analysis: Effectiveness of Maintenance and Rehabilitation Options. NCHRP Web Document 47 (Project 

20-50[3/4]). National Cooperative Highway Research

Program, Transportation Research Board, National 

Research Council, Washington, DC, June 2002. http://

onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w47.pdf.

 4. V. M. Mendez. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 23), Dec. 27, 2007, 

p. 3. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_23.pdf.

 5. Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991. 

http://onlinepubs.trb.org/onlinepubs/shrp/SHRP-91-

514.pdf.

 6. C. Churilla and H. Tahir. “States Convey Their Needs 

to LTPP: A Summary Report on Expectations.” 

American Association of State Highway and Transportation Officials and Federal Highway Administration, 

October 1995. Available from LTPP Customer Support 

Service Center (ltpp@info.gov). 

 7. America's Highways: Accelerating the Search for 

Innovation (Special Report 202). Transportation 

Research Board, National Research Council, 

Washington, DC, 1984.

 8. Strategic Highway Program Research Plans, Final 

Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986.

 9. N. F. Hawks. “LTPP at Year Five.” TR News, No. 158 

(January 1992), pp. 14–17, 32. http://trid.trb.org/

view/1992/C/365970.

 10. LTPP Program Focus: The Assessment Final Summary 

Report. Federal Highway Administration, McLean, VA, 

March 1997. Available from LTPP Customer Support 

Service Center (ltpp@info.gov). 

 11. A. L. Abbott. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 1), Mar. 25, 1997, 

pp. 1–3. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_letter_1.pdf.

 12. “FHWA Works with States and Provinces to Fix Gaps 

in LTPP Data.” Focus, June 1998, pp. 3, 5. http://www.

fhwa.dot.gov/publications/focus/98jun/068ltpp.cfm.

 13. P. N. Schmalzer, R. W. Plett, and G. E. Elkins. LTPP 

Specific Pavement Studies (SPS) Materials Action Plan 

Final Report (FHWA-HRT-10-049). Federal Highway 

Administration, McLean, VA, August 2010. http://www.

fhwa.dot.gov/publications/research/infrastructure/

pavements/ltpp/10049/10049.pdf.

 14. Long-Term Pavement Performance: Proceedings of the 

SHRP Midcourse Assessment Meeting (SHRP-LTPP/

UWP-91-514). Strategic Highway Research Program, 

National Research Council, Washington, DC, April 1991. 

http://onlinepubs.trb.org/onlinepubs/shrp/SHRP-91-

514.pdf.

 15. V. M. Mendez. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 18), Apr. 5, 2005, 

pp. 2–3. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_letter_18.pdf.

 16. M. E. Peters. FHWA Response to Long-Term Pavement 

Performance Committee Letter Report No. 18, May 19, 

2005, p. 1. http://onlinepubs.trb.org/Onlinepubs/sp/

ltpp_letter_18FHWAResponse.pdf.

11: LESSONS LEARNED FROM THE LTPP PROGRAM    241
242    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

The LTPP processes and database can serve as a springboard 

to monitoring the long-term performance of new pavement 

materials and technologies in the future.

© SP-Photo/Shutterstock.com
12: PavinG THE WAY TO THE FUTURE    

Paving the Way to the Future

12

Introductio

More than 25 years after the LTPP program began, 

the benefits and products resulting from the program continue to advance pavement design and 

management worldwide. The LTPP database has 

played a critical role in the development and evaluation of every major pavement design methodology 

developed over the past two decades, including the 

1998 American Association of State Highway and 

Transportation Officials (AASHTO) design procedures, Superpave®, and, most recently, the Mechanistic-Empirical Pavement Design Guide (MEPDG), 

implemented in the AASHTOWare® Pavement ME 

Design software. Beyond overall design procedures, 

the data have supported model development and 

validation for a wide array of pavement performance 

The LTPP program was born in the 20th century, but it has already provided knowledge that is improving 

the design, construction, rehabilitation, and maintenance of pavements that are serving the 21st century. 

The performance data gathered in the LTPP experiments over the past quarter century, and data yet to 

be gathered from the program’s high-performing sections and new experiments, will provide insight into 

designing, constructing, and maintaining pavements that last long into the future. 

predictors and indicators. The program has also 

influenced industry practices and has raised the 

bar for data collection and laboratory analysis standards worldwide. 

Although the LTPP program’s achievements have 

been many, to realize the full potential of the world’s 

most comprehensive pavement performance database 

and capitalize on the investment that has been made to 

date, much work remains to be done. As the national 

focus in transportation systems moves to performance 

standards and measures, as mandated by the Moving 

Ahead for Progress in the 21st Century Act (MAP-21),1 

the program brings to the table data and data-related 

capabilities that are needed to support the understanding of pavement performance measures. 
244    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

“To learn the lessons required to design 

long-life, high-performance pavements, we 

must continue to track the performance of 

the more structurally robust test sections. 

It is their performance that will yield the

requisite knowledge to develop, verify, and 

calibrate designs demanded by 21st century 

highway networks; their performance that 

will teach us how to manage and maintain 

these new pavements. If LTPP stops now, we

will have only learned how to build and 

maintain 20th century pavements better.”

 Transportation Research Board LTPP 

Committee, 20012

The program is committed to a fluid planning process with a 30-year horizon to keep pace with a changing world. Looking to the future, major areas of 

program activity will include the following:

• Securing and enhancing LTPP resources. Provide 

access, functionality, user support, and security 

for the pavement performance data, ancillary 

electronic data, film, and materials specimens 

that the program has collected. Continue to upgrade the database, user interfaces, and user support to keep pace with advances in data analysis 

methods and computing and communications 

technologies.

•	 Collecting pavement performance data. Monitor 

active LTPP test sections through a complete performance cycle. Design, implement, and monitor 

new LTPP experiments as pavement technologies 

change and new materials and technologies are introduced. 

•	 Conducting analyses and developing products. Pursue new insights and understanding by conducting 

research to fulfill the prioritized objectives of the 

Long-Term Pavement Performance Data Analysis 

Program.3

 Building on the results from the research, 

develop products and tools that are aligned with national pavement engineering priorities as outlined 

© hxdyl/Shutterstock.com
12: PavinG THE WAY TO THE FUTURE    

in the LTPP Product Plan4—products and tools that 

pavement engineers and managers can use to design, construct, maintain, and rehabilitate pavements for better performing, longer lasting, and 

more cost-effective highways. 

•	 Contributing to national initiatives. Work with other 

highway data collection initiatives to assure the 

availability, reliability, and validity of data used for 

research into pavement performance measures.

The road ahead for the LTPP program continues to be 

a long one with these future activities paving the way.

SECURING AND EN

RESO

The LTPP program has assembled massive amounts of 

information that are freely available to the pavement 

community (see sidebar). As described in chapter 8, 

researchers can now select and download LTPP performance data and ancillary information via the Internet and can request samples of paving materials from 

the Materials Reference Library. To maintain the usefulness of these resources to highway agencies and 

other pavement researchers, these assets must be 

LTPP Resour

The LTPP program has assembled and made available 

two major bodies of electronic data, the Pavement 

Performance Database and an archive of information 

that supports the performance data known as AIMS—

Ancillary Information Management System. In addition, the program maintains a huge and varied store of 

materials samples in the Materials Reference Library 

in Reno, Nevada. Together, the electronic data and 

physical specimens are a vital resource for future 

pavement research and are available through LTPP’s 

InfoPaveTM Web site, where data can be downloaded, 

or by contacting the LTPP Customer Support Service 

Center (Email: ltppinfo@dot.gov).

• The LTPP Database—The LTPP program’s princ

operational and product-enabling tool. The database is the program’s legacy for current stakeholders and future generations of highway researchers and practitioners seeking to learn how 

and why pavements perform the way they do. Currently containing more than 330 million records of 

data in 14 data modules, 484 data tables, and 

11,906 data fields, the searchable and downloadable database is a complex data warehouse. The 

program recently invested in improvements with 

the end user in mind: simplifying the database 

structure, adding more commonly used computed 

parameters for analysis, improving access, and 

creating a ready-for-analysis data structure. 

• The Ancillary Information Management System

A central, downloadable, electronic archive of raw 

data, information, documents, research reports or 

briefs, and tools that support the LTPP database. 

AIMS includes a collection of more than 1 billion 

raw traffic classification and weight measurement 

records, test section photographs, videos, reports, 

raw data files, construction plans, data collection 

protocols, data processing guides, and other program documentation. 

• Materials Reference Library—The repository fo

material samples from the General Pavement 

Study and Specific Pavement Study test sections 

across the United States and Canada—asphalt cement, Portland cement, natural aggregates, combination materials—as well as more than 12,000 

35-mm film distress records. The facility also contains specimens from the Strategic Highway Research Program and Federal Highway Administration’s (FHWA) Crumb Rubber Modifier Project and 

Accelerated Loading Facility. Materials samples 

are available for evaluation and verification of new 

pavement designs and materials tests. 

• LTPP Documentation—More than 600 documen

related to the LTPP program are housed in a central library at FHWA’s Turner-Fairbank Highway 

Research Center in McLean, Virginia, and are 

available in the LTPP Reference Library, which is 

distributed with the Standard Data Release, and 

at the LTPP InfoPaveTM Web site. 
246    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

properly secured, maintained, and upgraded with 

changing technology to assure continued access.

Providing Security and Maintenance

The LTPP data have been available to all potential 

users since the first public release of data in 1991. 

These data will remain an important resource for 

pavement performance research for many years to 

come. Without adequate investment in security and 

maintenance activities, however, the potential of the 

LTPP database to contribute to advancements in 

pavement engineering could be gradually eroded and 

eventually lost altogether. Ensuring that the database 

and its supporting information remain accessible, yet 

secure, has required the program to take some important steps, which are outlined in chapter 8. The program will continue to maintain the security, 

functionality, and accessibility of the database and to 

upgrade the database software and hardware to keep 

pace with future changes in data storage, security, and 

communications needs and technologies. 

Maintenance of the Materials Reference Library is 

also vital, as it is the repository for materials samples 

from the LTPP test sections and other pavement programs of national significance, and it also provides 

climate-controlled storage conditions for the LTPP 

35-mm film distress records. Many of the materials samples are from projects with performance data, which 

makes the samples especially valuable to researchers. 

The samples have been used to support 32 national 

highway research projects. By continuing to maintain 

the Materials Reference Library, the LTPP program will 

enable researchers to link the results of past, present, 

and future pavement research. Researchers will be able 

to use samples from the test sections, for example, in 

evaluating future test methods, thereby enabling 

updates of the data to reflect new technologies.

Improving the Databa

Refining and improving the LTPP database so that it is 

aligned with users’ needs is critical to achieving the full 

future value of the LTPP program. Additional refinement of the database will make it easier and more 

effective to use. Several planned database improvements, many of which are currently underway, have 

the potential to accomplish this goal:

•	 Create a custom data extraction that is formatted

and contains all data needed for analysis using specified falling weight deflectometer backcalculation

computer programs.

•	 Add a new table that provides a unique index of the

location for all pavement monitoring measurements 

performed on each joint or transverse crack location on Portland cement concrete (PCC) pavements 

and rehabilitated pavement structures.

•	 Create a unified set of pavement distress data that

presents a logical progression of key pavement 

distress types over time, taking into account the different methods the LTPP program has used to 

measure distress, variability inherent in each measurement method, and timing of field pavement 

construction and maintenance activities.

•	 Create a calibration data set that is specific to the

MEPDG and can be used by highway agencies to 

perform pavement performance calibration from 

LTPP test sections located within or near their 

jurisdictions.

•	 Create a performance measure data set to include

distress, profile, faulting, and rutting compatible 

with Highway Performance Monitoring System 

requirements. This data set will support implementation of the performance-based surface transportation program mandated by the current highway 

legislation, MAP-21.

•	 Provide a set of basic time history of pavement performance observations of pavement distress, roughness, friction, and falling weight deflectometer 

measurements that include matching cumulative 

load values, pavement material property characterizations, pavement structure, and climate.

•	 Interpret available data, expand project-level sample data to recommended test-section-specific characterizations, impute needed time-dependent 

properties from other measurements, and provide a 

characterization of the relative estimated error for 

the following material properties:

– Hot-mix asphalt (HMA) volumetric measures.

– HMA resilient and dynamic properties.

– PCC temporal indices.
12: PavinG THE WAY TO THE FUTURE    

– PCC thermal coefficient.

– Resilient modulus of unbound materials.

– Other parameters related to drainage and climate.

Supporting LTPP Data 

Given the complexity of the LTPP database, continuing 

to provide technical support to data users will be crucial to maximizing research results. Researchers 

around the world have successfully used the data to 

address an array of pavement engineering challenges. 

Vital to this success has been the availability of LTPP 

technical support to answer questions, point researchers to the documentation they need to understand the 

data applicable to their problems, and otherwise help 

users navigate and manipulate the database structure 

to select the appropriate data. 

Future user support will take different forms, 

depending on the intended use of the data. The LTPP 

program’s primary customer, highway agencies using 

the LTPP database to address pavement issues of concern to them, will receive support to ensure clear 

understanding of the data being provided and to assist 

them with any problems. Such support may focus on 

generating data sets for selected locations that could 

be used to calibrate the MEPDG for a State or Province’s local conditions. In the future, when national 

pavement performance measures are established, the 

LTPP database is likely to be the prime resource for 

highway agencies’ use. 

For studies of national significance, such as the 

National Cooperative Highway Research Program 

(NCHRP) project that developed the MEPDG, support 

will often entail face-to-face meetings to communicate 

fully the data needs and required formats and to identify the best source of the data within the LTPP database. Custom extractions from the database can then 

be performed to provide the needed data in the appropriate format, followed by ongoing technical support 

to ensure clear understanding of the LTPP data and to 

clarify any issues that may arise. 

Support will also include training for Federal, 

State/Province, and local agencies, as well as members of industry and academia. For example, the 

LTPP program has developed a workshop to familiarize pavement engineering professors with the 

database and engage them in using the data to solve 

real-world pavement analysis problems. For university students working on theses, dissertations, or other research projects, support will include providing 

them with the latest LTPP Standard Data Release, 

recommendations on where to find the needed data 

within the database structure, and clarification of 

data-related questions. 

COLLECTING PAVEMEN

DA

The LTPP program’s pavement performance data collection effort is the largest and most comprehensive ever 

undertaken for in-service highway pavements. The program has monitored 2,509 test sections located throughout the United States and Canada. The test sections that 

are still being monitored include many that are part of 

the program’s rehabilitation and structural factor experiments; long-life, high-performance pavements; and 

sites where traffic monitoring continues. 

Changes in technology will also expand the types 

and quantity of performance-related data that can be 

captured. For example, variations in the quality of construction have a vital impact on pavement performance. As technologies evolve, new tools are becoming 

available to capture more comprehensive data during 

construction, enabling highway agencies to know 

whether pavements are built as planned. Some examples of these technologies are magnetic tomography 

systems for checking dowel bar alignment5

 and fullwidth infrared thermography scanning systems for 

measuring HMA placement temperatures in real time.6

With additional information that these technologies 

can provide, “noise” in the data may be reduced and 

clear trends may appear. As it pursues new experiments, the LTPP program will be examining technologies that can help to identify and separate the many 

variables affecting pavement performance.

LTPP data yet to be collected will contribute valuable new information to pavement performance 

research. The future of LTPP data collection will 

include completion of the original experiments, forensic studies of selected test sections that can shed light 

on specific performance questions, and new experi-
248    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

been completed have been moved to the GPS-6 (asphalt 

concrete (AC) overlay of AC pavements) and -7 (AC 

overlay of PCC pavements) experiments. Some of the 

experiments were designed to complement each other, 

for example, GPS-1 and -2 (AC on granular and bound 

base pavements, respectively) and SPS-1 (structural 

factors for flexible pavements). GPS-9 (unbonded PCC 

overlay of PCC pavements) represents the only available long-term data on composite pavement structures 

and has been given priority due to a request from the 

Strategic Highway Research Program (SHRP) 2. The 

LTPP program will continue monitoring these sections 

to fully answer the critical pavement performance 

questions they were designed to address.

One future opportunity that merits consideration is 

to collect permanent distress records for those test sections that remain in service, as recommended by the 

Transportation Research Board (TRB) LTPP Committee. Table 12.1 outlines the benefits of monitoring active 

test sections throughout their performance lives.

ments designed around emerging technologies, such as 

warm-mix asphalt (WMA) and pavement preservation. 

Completing the Original LTPP Experim

As of 2014, 732 of the original LTPP test sections were 

still being monitored—372 in the General Pavement 

Study (GPS) experiments, and 360 in the Specific Pavement Study (SPS) experiments. To achieve the objectives for each experiment, it is critical that data be 

collected for the remaining sections over a full performance cycle, especially in view of the shortage of test 

sections in some experiments when the designs were 

implemented. 

Some of these active test sections have been constructed or rehabilitated within the past decade, some 

are long-life sections still in good condition, and others 

have been monitored as LTPP test sections both before 

and after rehabilitation. Traffic data also continue to be 

collected on most SPS test sections. Many GPS and SPS 

sections whose performance cycle monitoring has 

Table 12.1. Importance of completing the long-term monitoring of the original LTPP experim

LTPP Experiment  Benefits of Additional Data Col

SPS-1 (structural factors for flexible pavements) Improved ability to derive definitive results, based on comple

SPS-2 (structural factors for rigid pavements) performance histories, concerning the impact of design features on 

long-term pavement performance.

SPS-8 (environmental effects in the absence of Assessment of the effects of loading and environment on pavement 

heavy loads) life, information that is critical for pavement design and performance 

models. This work can begin when sufficient distress (serviceability 

loss) has accumulated on the SPS-8 test sections.

GPS-6 (AC overlay of AC pavements)  Improved design, construction, and maintenance procedures f

GPS-7 (AC overlay of PCC pavements) asphalt concrete overlays, which will result in longer and more

SPS-5 (rehabilitation of AC pavements) economical renewed pavement life.

SPS-6 (rehabilitation of jointed PCC pavements)

SPS-9 (Superpave®)

GPS-1 (AC on granular base pavements) Performance data required to develop, verify, and calibrate designs

GPS-2 (AC on bound base pavements) for long-life, high-performance pavements and to manage and

GPS-3 (jointed plain concrete pavements) maintain those new pavements.

GPS-4 (jointed reinforced concrete pavements)

GPS-5 (continuously reinforced concrete pavements)

GPS-9 (unbonded PCC overlay of PCC pavements)

Permanent distress records (photographs) for Future analysts will have the opportunity to revisit test section 

still-active test sections condition on the basis of objective records. Potential for 

interpretation/reinterpretation of images based on improved 

distress definitions and criteria. 

Note. Adapted from LTPP Beyond FY 2009: What Needs to Be Done?, p. 12.7
12: PAVING THE WAY TO THE FUTURE    249

Conducting Forensic Studies

Another significant source of data for the program are 

forensic studies at selected LTPP test sections when 

they are removed from the study. Close examination of 

these mature sections before they are replaced or rehabilitated can yield new data and analyses that will 

contribute much to the understanding of pavement 

deterioration processes.8 Although forensic evaluations are an important element in the LTPP program, 

funding constraints delayed implementation. As 

described in chapter 7, the program published the 

Framework for LTPP Forensic Investigations in 2004 

and conducted four forensic studies, funded by the 

Federal Highway Administration (FHWA), in 2008. 

Several highway agencies have also conducted forensic 

evaluations of LTPP test sections.

Forensic investigation of LTPP test sections that 

have failed prematurely and sections that have shown 

unexpectedly good performance are of particular value 

in understanding the variables that affect pavement 

performance. With national guidelines in place, the 

foundation has been laid for future forensic investigations of LTPP test sections as well as other pavement 

studies by highway agencies. 

Implementing New LTPP Experiments

Alongside the continued monitoring in the original 

LTPP experiments to achieve the program’s original 

objectives, the program’s leaders and advisors recognize that new technologies have been introduced and 

implemented since the program was planned in 

the mid-1980s. Some examples are Superpave, the 

MEPDG, in-place recycling, and alternative construction materials such as aggregates from waste sources, 

composite materials, precast concrete pavements, 

and nano particles. In addition, the impact of climate 

on infrastructure is of increasing importance. The 

LTPP program is addressing these changing needs in 

its short- and long-range plans.

In the near term, the foundation has been set for a 

new LTPP field experiment to collect short-term and 

long-term research-grade performance data on WMA 
250    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

for a new design guide. More recently, LTPP data and 

data analyses were critical in the development of the 

MEPDG under NCHRP Project 1-37A. LTPP data analysis reports have been published by SHRP, FHWA, and 

NCHRP. States, Provinces, and universities have also 

published hundreds of reports, theses, and dissertations based on the analysis of LTPP data.

FHWA worked with the TRB Expert Task Group on 

LTPP Data Analysis to develop the Strategic Plan for 

LTPP Data Analysis in 1999, as described in chapter 10.10

The plan, which has been expanded and maintained 

with the support of the TRB LTPP Committee, presents a long-term strategy for data analysis that takes 

into account both internal and external analytical 

needs, the current or anticipated data availability, and 

the process for developing major LTPP products. It 

may be useful to repeat here the current plan’s nine 

strategic objective areas:

•	 Traffic characterization and prediction.

•	 Materials characterization.

•	 Determination of environmental effects in pavement design and performance prediction.

•	 Evaluation and use of pavement condition data in

pavement management.

•	 Development of pavement response and performance models applicable to pavement design and

performance prediction. 

•	 Maintenance and rehabilitation strategy selection

and performance prediction. 

•	 Quantification of the performance impact of specific design features.

•	 Analyses supporting and enhancing the use of the

MEPDG.

•	 Comprehensive use of LTPP to improve the management of pavement assets.11

By 2014, under the plan, 76 studies had been completed, 18 studies were ongoing, and 13 were planned. An 

additional 104 problem statements on the plan awaited 

funding. In addition, the program recommends that 

early findings from LTPP data be re-examined to 

determine if the short-term trends were correct. The 

pavements. With support from FHWA management 

and as part of a multiteam effort, this experiment is 

designed to determine whether there is any significant 

difference between the performance of WMA and that 

of HMA. The FHWA is partnering with States and 

Provinces to construct projects in support of this 

national experiment. Test section recruitment and 

selection for the new SPS-10 experiment, Warm-Mix 

Asphalt Overlay of Asphalt Pavements, began in 2014, 

with construction slated for 2014 and 2015.9 

The LTPP WMA experiment will be followed by 

other new field experiments in the years to come. 

There is, for example, a real need today to understand 

pavement preservation and its impact on pavement 

performance. Planning is underway for a pavement 

preservation experiment. Planning activities for a coldin-place recycling experiment will follow next, and 

other current topics of interest—hot-in-place recycling, composite pavements, precast pavements, and 

fast-track pavement construction—are being considered. As technologies evolve and are implemented in 

the field under real conditions, the need to perform 

long-term monitoring will continue. 

CONDUCTING A

DEVELOPING

Data analysis and product development have been 

integral to the LTPP program from its early days. 

Focused analysis has led to many program improvements in data collection practices and interpretation 

over the years and revealed the need for new software 

and engineering tools to improve the uniformity and 

validity of the data being collected. Data analysis and 

product development will take on even greater importance in the future with the maturity of data collection 

and the database itself. 

New Insights and Understanding Th

LTPP Data Analy

Analysis of LTPP data began in 1992 with the evaluation of the then-current version of the AASHTO Guide 

for the Design of Pavement Structures. That analysis 

showed large discrepancies between predicted and 

actual pavement performance, confirming the need 
12: PavinG THE WAY TO THE FUTURE    

The LTPP program has created many products to 

date, but the most significant products are yet to come, 

after the full performance history of the test sections 

has been documented and complete suites of quality 

data are available in the LTPP database. 

POTENTIAL FUTUR

AND BE

With regard to its ultimate potential, the LTPP program has barely started to advance the knowledge of 

researchers and practitioners—yet it already has contributed to saving billions of dollars in construction 

and maintenance costs.12 Pavement engineers and 

designers will rely on the LTPP database, a kind of “virtual highway” to improved pavement performance, for 

decades to come. 

Although it is not possible to envision every possible 

future use and insight, the larger the pool of analysts 

using LTPP data and other ancillary information, the 

greater the chances are that the data will support major 

breakthroughs. Some of the resources that future users 

may investigate to gain better insight into pavement 

performance include the following:

•	 LTPP test sections will be a valuable resource within the States/Provinces, particularly for those looking to support their own performance monitoring 

programs. Comparing LTPP information to similar 

data elements collected within the agency (e.g., 

pavement distress) at the same location will allow 

Long-term monitoring of pavement 

performance continues to be a key need 

nationwide, just as it was in the 1980s 

when the LTPP program began. The LTPP 

processes and database can serve as a 

springboard to monitoring the long-term 

performance of new pavement materials 

and technologies in the future.

LTPP program will support continued data analysis 

that is aligned with the objectives outlined in the plan.

The greatest benefit from the LTPP database will be 

realized by applying the data and then developing products from what is learned through this application. To 

achieve the most immediate impact and capture the full 

value of the data, a coordinated and integrated approach 

to analysis will be accompanied by a similarly coordinated product development program. 

New Tools and Resources for Pav

Researchers, Practitioners, and Manager

Products resulting from the LTPP data have benefited 

highway agencies and other segments of the highway 

community. These products include new methods, 

guidelines, and procedures for standardized pavement 

testing and performance data collection. As more pavement performance data are added to the database from 

the original and new experiments, and if highway legislations continue to be driven by performance and 

asset management imperatives, the LTPP program will 

remain in the forefront of providing the data, resources, and technical expertise needed to develop future 

products for highway agencies and the pavement 

industry. What these new products will be is still to be 

determined. 

Other significant products of the LTPP program will 

continue to be issued. The Standard Data Releases are 

available via the Internet at LTPP’s InfoPaveTM Web site, 

so that users can easily access the wealth of information 

available in the LTPP database. The program’s guidelines 

for data collection and distress rating, such as the Distress 

Identification Manual, will be updated as needed.

Another benefit that will continue into the future is 

the introduction and use of LTPP data in university 

engineering curricula. This curricula application will 

introduce both professors and students to the use of 

database manipulation tools, which is a necessary skill 

that is not currently covered in most engineering programs. As in the past, future undergraduate and graduate students will use the LTPP database and monitoring 

procedures as part of their pavement engineering 

coursework. Many students will be introduced to the 

database and to pavement research through the ASCELTPP International Data Analysis Contest. 
252    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM

an agency to correlate its own data with LTPP, 

thereby expanding the utility of its in-house data.

•	 LTPP test sections will provide national data

needed to calibrate current mechanistic-empirical 

models and the new, improved models that will be 

developed. 

•	 LTPP pavement deterioration trends can be used by

highway agencies that do not have the data or resources to develop their own. These trends are needed 

for efficient pavement design and management.

•	 The results from the traffic data analyses, such as

investigating the effect of different axle configurations and loading sequences on pavement distress 

accumulation, can be used to check the validity of 

MEPDG models and assumptions and to refine future mechanistic-based design procedures. 

•	 Access to materials samples housed at the Materials

Reference Library will provide a critical link between field performance and materials properties 

for new test methods and will support a variety of 

other materials-related research.

•	 Detailed surface roughness profiles and distress maps

can be used to investigate relationships between 

roughness development and distress accumulation. 

•	 Future forensic analysis of LTPP test sections will

provide valuable information. For example, the LTPP 

SPS-1 projects (structural factors for flexible pavements) will serve as an excellent source for studying 

the effect of pavement thickness and the development of top-down versus bottom-up cracking.

•	 Prediction of remaining pavement life will be improved by revisiting the relationships between 

pavement response during falling weight deflectometer testing and future pavement performance, 

and by exploring the use of next-generation embedded self-powered strain sensors to measure 

continuous strain pulses under actual traffic, combined with damage transfer functions. 

In addition, the international community will look to 

the LTPP program in establishing their own long-term 

research programs (most recently, Brazil has requested 

several FHWA visits to discuss how such a program 

can be implemented there), and other domestic programs, such as the Long-Term Bridge Performance 

Program, will benefit from LTPP’s models of data quality standards and coordination necessary to successfully meet their objectives.

Contributing to National Initiati

The LTPP program is one of several programs and initiatives that collect or use highway data in planning and 

policymaking related to different aspects of the Nation’s 

transportation systems. For example, data from the 

LTPP program complement the data of the Highway 

Performance Monitoring System, which is used in highway policymaking. The LTPP program is in a position to 

share knowledge, data, and research facilities with other 

highway data collection initiatives to assure the availability, reliability, and validity of data used for research 

into pavement performance measures. Collaboration at 

this level can maximize budgetary resources and assure 

that the data secured are of the highest quality possible. 

The LTPP program will continue working with the 

highway agencies, AASHTO, and TRB to provide 

research-quality data that meets the present and future 

needs of the pavement community.

LTPP AND A FUT

The LTPP database has enormous potential as the

foundation for improvement in pavement engineering 

and management procedures and practices. Some of 

that potential has already been realized, but additional 

work will be required to take full advantage of the 

investment made in the program. 

For the LTPP program, the road ahead is one of 

opportunity. By continuing to invest in the database 

and the Materials Reference Library and by continuing 

to collect data, conduct data analyses, and develop 
12: PavinG THE WAY TO THE FUTURE    

products, the program will carry forward benefits and 

rewards for a new generation of highway engineers 

and researchers facing new challenges. Building on the 

lessons learned to date is also vital to achieving the 

program’s full potential. While much has been accomplished, the LTPP data still offer the key to even better 

performing pavements tomorrow. Even as the LTPP 

data and products change today’s pavement design and 

management worldwide, the LTPP story continues, 

and the best is yet to be discovered. 

REFERE

1. U.S. Statutes at Large 126 (2012): 405–988. Moving 

Ahead for Progress in the 21st Century Act.

2. Fulfilling the Promise of Better Roads: A Report of the 

TRB Long-Term Pavement Performance Committee. 

Transportation Research Board, The National Academies, Washington, DC, 2001, p. 13. http://onlinepubs.

trb.org/Onlinepubs/sp/ltpp_report_2001.pdf.

3. “Long-Term Pavement Performance Data Analysis 

Program.” Web page, Dec. 11, 2013. http://www.fhwa.

dot.gov/research/tfhrc/programs/infrastructure/

pavements/ltpp/pdf/tablecloth_complete.pdf.

4. LTPP Product Plan (FHWA-RD-01-086). Federal 

Highway Administration, McLean, VA, 2001.

http://www.fhwa.dot.gov/publications/research/

infrastructure/pavements/ltpp/01086/01086.pdf.

5. “Use of Magnetic Tomography Technology to Evaluate 

Dowel Bar Placement” (TechBrief; FHWA-IF-06-002). 

Federal Highway Administration, Washington, DC, 

October 2005. https://www.fhwa.dot.gov/pavement/

pccp/pubs/06002/06002.pdf.

6. M. Stroup-Gardiner and E. R. Brown. National 

Cooperative Highway Research Program Report 441. 

Segregation in Hot-Mix Asphalt Pavements. National 

Academy Press, Washington, DC, 2000, pp. 66–68, 

79–80. http://onlinepubs.trb.org/onlinepubs/nchrp/

nchrp_rpt_441.pdf.

7. LTPP Beyond FY 2009: What Needs to be Done? 

(FHWA-HRT-09-052). Federal Highway Administration, McLean, VA, 2009. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/09052/09052.pdf.

8. “Forensic Evaluations of the Long Term Pavement 

Performance (LTPP) Test Sites.” LTPP Newsletter, vol. 

4, no. 2 (Spring 2008), p. 1. https://www.fhwa.dot.gov/

publications/ltppnews/08060.pdf.

9. “Infrastructure.” FHWA R&T Now, November 2013. 

http://www.fhwa.dot.gov/publications/rtnow/

13novemberrtnow.pdf.

10. “Analysis.” Web page. http://www.fhwa.dot.gov/

research/tfhrc/programs/infrastructure/pavements/

ltpp/analysis.cfm. 

11. “Long-Term Pavement Performance Data Analysis 

Program.” Web page, Dec. 11, 2013. http://www.fhwa.

dot.gov/research/tfhrc/programs/infrastructure/

pavements/ltpp/pdf/tablecloth_complete.pdf.

12. Long-Term Pavement Performance Program: 

Accomplishments and Benefits 1989–2009 (FHWART-10-071). Federal Highway Administration, McLean, 

VA, 2010, pp. 18–20. http://www.fhwa.dot.gov/

publications/research/infrastructure/pavements/

ltpp/10071/10071.pdf. 

Long-Term Pavement Performance Program Team receives FHWA’s Administrator’s

Excellence in Teamwork Award (November 5, 2010). Front Row (left to right): Antonio 

Nieves (LTPP Product Development), Victor Mendez (then FHWA Administrator), Deborah 

Walker (LTPP Team Member), Jane Jiang (LTPP Team Member), Jorge Pagán-Ortiz 

(Director of Office of Infrastructure). Second Row: Michael Moravec (LTPP Product 

Development), Larry Wiser (LTPP Team Member), Aramis López (LTPP Team Leader), Jeff 

Paniati (FHWA Executive Director), Jack Springer (LTPP Team Member), Eric Weaver 

(former LTPP Team Member), Michael Trentacoste (Associate Administrator for Research, 

Development, and Technology).

The picture above shows the LTPP Team members with FHWA management as the team is recognized for its exemplary team 

spirit in the pursuit of excellence in the LTPP program. Past members of the FHWA-LTPP Team (not shown in the picture) who 

have contributed to the program are William Bellinger, Charlie Churilla, John Klemunes, Kris Gupta, Cheryl Richter, Shahed 

Rowshan, Jean Sexton, Monte Symons, and Paul Teng.
© J. D. Talasek/National Academy of Sciences
appendix a: Planning and advisory committees 257

INTRODU

Well before the LTPP program began in 1987 and continuing into the present, the input of stakeholders and 

the guidance of experts in the highway community 

have been critical to the success of the program. This 

appendix documents to the extent possible some of the 

committees and expert task groups (ETGs) that have 

planned the program, guided its implementation, and, 

through a Data Analysis Working Group (see page 

264), helped to promote analysis of LTPP data. 

Between 1987 and 1992, when the LTPP program was 

part of the Strategic Highway Research Program 

(SHRP), an independent agency of the National 

Research Council (NRC), LTPP management was guided by an arrangement among the Federal Highway 

Association (FHWA), American Association of State 

Highway and Transportation Officials (AASHTO), and 

the NRC. The NRC provided formal, external, peer 

review and advisory support for the LTPP program 

through an advisory committee assisted by specialized 

ETGs and subcommittees.1,2 When SHRP ended, in 

1992, NRC continued to provide these advisory functions through SHRP’s sister organization, the Transportation Research Board (TRB), and continues to do so.

Members of the planning and advisory committees 

and ETGs bring expertise in pavement engineering and 

performance monitoring, statistics and data analysis, 

information technology, and other specialized areas associated with the LTPP program’s goal and objectives. The 

members are drawn from highway agency staff, academia, pavement industries, consulting firms, and 

research institutions from across the United States and 

Canada. In addition, committee liaisons from AASHTO, 

Appendix

Planning and Advisory Committee

Supporting the LTPP Prog
258 THE LONG-T

C-SHRP (the Canadian SHRP), FHWA, international 

agencies, and other organizations provide important linkages. These liaisons are included in the membership lists. 

The following sections list, to the extent they are 

available, the approximate dates the committees and 

ETGs served, their scopes, and the individuals who 

have participated during three periods (see sidebar):

•	 SHRP planning and pre-implementation

advisors (circa 1982–86).

•	 Pavement Performance Advisory Committee

(1987–95).

•	 TRB Long-Term Pavement Performance

Committee (1996–present).

The service of some ETGs and many members has 

spanned these timeframes. Members of the advisory 

committees and ETGs during these periods are listed 

below (where known, chairpersons are shown in italics). Please note that these lists are incomplete and 

undoubtedly contain inaccuracies. Although an extensive search has been conducted, records were not always 

accessible. Some committees morphed into others, 

some had very short lifespans, and for some, documentation is no longer available. Any omissions of individuals who have contributed to the program, misattributions, 

or other errors are unintentional and deeply regretted.

SHRP PLNNING AND PREIMPLEMENTA

The Strategic Transportation Research Study: Highways,3

 was one of a series of studies that paved the way 

for implementation of the SHRP-LTPP program. The 

study was sponsored by FHWA and carried out by TRB. 

Additional research planning studies for SHRP were 

sponsored by the National Cooperative Highway 

Research Program and, in the case of the long-term pavement performance program, FHWA. These studies culminated in the publication in 1986 of Strategic Highway 

Research Program Research Plans: Final Report,4 in which 

the foundation for the LTPP program was laid. Following 

are the advisory groups that helped to shape the LTPP 

program through these pre-implementation studies. 

Steering Committee for the Strategic 

Transportation Research Study: Highways

Duane Berentson

Donald W. Collier

Francis B. Francois

Robert N. Hunter

Thomas D. Larson

Harold L. Michael

Thomas D. Moreland

Daniel T. Murphy

William A. Ordway

Richard S. Page

Bruce H. Pauly

Daniel Roos

Joseph L. Schofer

Planning and Pre-implementation Advis

(1982–86)

•	 Steering Committee for the Strategic

Transportation Research Study: Highways

•	 SHRP Task Force

•	 SHRP Advisory Committee, Pavement

Performance

Pavement Performance Advisory Committ

(1987–95)

•	 Deflection Testing and Backcalculation

•	 Equipment Evaluation

•	 Experimental Design and Analysis

•	 Automated Distress Identification

•	 Traffic Data Collection and Analysis

•	 Weigh-in-Motion Equipment and Technology

•	 Environmental Data

TRB Long-Term Pavement Performan

Committee (1996–present)

•	 Automated Distress Identification/Distress

Data Collection and Analysis

•	 Data Analysis

•	 Database Development and Operations

•	 Materials and Falling Weight Deflectometer

Data Collection and Analysis

•	 Product Development and Delivery

•	 State Usage of the LTPP Data

•	 Traffic Data Collection and Analysis

•	 LTPP Special Activities

LTPP advisory groupS/supp

for each tech
appendix a: Planning and advisory committees 259

Strategic Highway Research Program Task For

Ray A. Barnhart

Duane Berentson

Thomas B. Deen

Francis B. Francois

Mark G. Goode

David J. Hensing

Boris Hryhorczuk

Robert N. Hunter

Strategic Highway Research Program Adviso

Committee, Pavement Performan

Richard D. Barksdale

Byron Blaschke 

Tom Christison

Leland Fletcher

Raymond A. Forsyth

Dave Gendell

Wade Gramling

Kevin Heanue

R. G. Hicks

Ronald W. Houska

W. Ronald Hudson

Paul E. Irick

Mike Jaskaniec

W. H. Jorgenrud

Robert Joubert

Roger LeClerc

Richard A. Lill

PAVEMENT PERFO

COMMITTEE (1987–

Scope

The major objective of the Pavement Performance 

Advisory Committee (PPAC), which reported to the 

SHRP Executive Committee,5

 was to review the LTPP 

research plans for conformance with the established 

goal and objectives, for practicality and applicability to 

the technical needs of the operating highway agencies, 

and for engineering technological accuracy and feasibility. In addition, the committee was charged with 

identifying significant highway engineering products 

emerging from the LTPP studies and assisting the 

SHRP Executive Committee in developing priorities 

and recommendations for implementation.

The committee provided programmatic review and 

technical commentary on the program objectives, longrange plans, near-term operational activities, and progress of the LTPP research program; conducted external, 

nongovernmental reviews of research; and identified 

needs for further research projects. Planning and 

implementation of the LTPP program were emphasized, but other pavement performance research was 

also reviewed to identify gaps and overlaps, encourage 

cooperation, and foster the synthesis of further results. 

PPAC served from approximately 1987 to November 

1995, a period that included the 5-year term of SHRP 

and the early years of the program under FHWA’s management.6

 Following are the committee members and 

the ETGs that assisted the committee.

Members

Allan L. Abbott

David Albright

Roger Almond

Richard Barksdale

James L. Brown

Albert J. Bush III

Charles J. Churilla

Robert L. Clevenger

Ronald Collins

Guy Doré

Charles E. Dougan

Ted R. Ferragut

McRaney Fulmer

John P. Hallin

Neil F. Hawks

Newton Jackson

Marlin J. Knutson

Hans Jorgen Ertman Larsen

Rita Leahy

William J. MacCreery

LTPP Benefits Subcommitte

Scope

This subcommittee was created by PPAC to review the 

outcomes that have resulted from the LTPP program 

and how these outcomes can benefit highway agencies 

Lester P. Lamm

Thomas D. Larson

Harold W. Monroney

Thomas D. Moreland

David K. Phillips

Robert J. Reilly

Charley V. Wootan

William N. Lofroos

Joel Marcuson

Brooks Nichols 

Frank P. Nichols, Jr.

Charles A. Pagen

Art Peters

Dale Peterson

Roger Petzold

Randell Riley

Harry A. Smith

Dick Sullivan

Shiraz D. Tayabji

Harry H. Ulery, Jr.

Fred Van Kirk

George B. Way

Thomas D. White

Matthew W. Witczak

Frank R. McCullagh

Kenneth H. McGhee

Raymond K. Moore

Richard D. Morgan

William R. Moyer

David E. Newcomb

Louis M. Papet

Olga Pendleton

Charles A. Pryor, Jr.

Cesar A. V. Queiroz

Rolands L. Rizenbergs

Gary K. Robinson

Frederic R. Ross

Ted M. Scott II

Gary D. Taylor

T. Paul Teng

Marshall R. Thompson

Kenneth R. Wardlaw

Stella White

Marcus Williams
260 THE LONG-T

in the design, construction, and maintenance and rehabilitation of their pavements. 

Members

Allan L. Abbott

Larry Cole

Gary D. Taylor

Expert Task Group on Deflection Testin

and Backcalculation 

Scope

The ETG assisted in developing the SHRP backcalculation program by recommending criteria for the selection of software for use in the program, participating in 

the evaluation of six candidate backcalculation programs, and recommending Poisson’s ratio values for 

use in the backcalculation procedure.7,8

Members

Paul Anderson

Robert C. Briggs 

Albert J. Bush III 

Billy G. Connor 

William Edwards 

John Hallin 

Frank L. Holman, Jr. 

William J. Kenis

Roger M. Larson 

Joe P. Mahoney 

Expert Task Group on Equipment Evaluati

Scope

The ETG provided guidance to SHRP staff on monitoring equipment used to collect pavement performance data for network- and project-level pavement 

management.

Members

Robert C. Briggs

James K. Cable

Gaylord Cumberledge

Harold Dalrymple

Leo DeFrain

Bob Guinn

James P. Hall

Sonya Hill

Expert Task Group on Experimenta

Design and Analys

Scope

The ETG provided guidance to SHRP staff, consultants, and LTPP regional staff in the overall design of 

the experiments in the General Pavement Studies and 

Specific Pavement Studies by evaluating the analysis 

plans and recommending specific changes in the 

experiments. The ETG periodically reviewed the analysis procedures over the course of the studies, together 

with the SHRP Data Analysis Working Group, PPAC, 

SHRP staff, and technical contract staff. 

Members

Paul E. Benson

James L. Brown

Lyle Calvin

Samuel G. Carmer

Judith B. Corley-Lay

Morris de Groot

John P. Hallin

Newton Jackson

Alex Kazakov

Walter P. Kilareski

Expert Task Group on LTPP Autom

Distress Identificatio

Scope

The ETG provided assistance to SHRP in its effort to 

evaluate pavement distress on LTPP test sections and 

to suggest mechanisms for implementation at the State 

level. This ETG played a key role in the development of 

the SHRP Distress Identification Manual, which is one 

of the LTPP program’s most highly used products. 

Members

Janice Arellano

Michael E. Ayers

Carl Bertrand

James K. Cable

Lawrence W. Cole

Gaylord Cumberledge

Jon A. Epps 

Tahar El-Korchi

Roger Green

Wouter Gulden

Kent Hansen

Gary Sharpe

Carl Monismith

Ray Moore

Robert L. Mikulin

Richard J. Nelson

Larry A. Scofield

Ken Stokoe

Richard N. Stubstad 

Marshall R. Thompson 

Per Ullidtz

Jacob Uzan 

Wes Yang

Roger M. Larson

Richard A. Lill

Joe P. Mahoney

Michael Markow

Robert L. Mason

John R. Olds

William D. O. Paterson

James A. Sherwood

Marshall Thompson

Richard M. Weed

Loren Hill

Colleen Kissane

Donald Larsen

Charles Larson

Daris Ormesher

Joy Portera

Richard B. Rogers

Brian Schleppi

Shelley M. Stoffels

James Walls III

Shie-Shin Wu

Rudolph R. Hegmon

P. G. Jordan

Robert McQuiston

Kenneth H. McGhee

Anand Prakash

Gerry Wrong

William A. Young
appendix a: Planning and advisory committees 261

William Lofroos

Bill McCall

George Novenski

Alan Pisarski

Larry Schoenhard

Ronald Tweedie

George Wass

Richard Weed

John Van Berkel

Doug Warpoole

John Wyman

Expert Task Group on LTPP Traffic D

Collection and Analysi

Scope

The ETG provided guidance to SHRP staff, consultants, and LTPP regional staff for the traffic data collection program. The Traffic ETG played an active role in 

the program and was instrumental in several decisions 

regarding traffic and data collection requirements, 

site-specific data collection, database needs, weigh-inmotion requirements, guidelines in traffic variability 

and precisions, equivalent single-axle load calculations, traffic data analysis, and adoption of the FHWA 

vehicle classification system.9,10 

Members 

David Albright

Wiley Cunagin

Curtis Dahlin

Ralph E. Folsum

Jerry J. Hajek

John Hamrick

Andrew Horosko

Bruce Hutchison

Ed Kashuba

Expert Task Group on Weigh-in-Motion

Equipment and Technolog

Scope

The Weigh-in-Motion Equipment and Technology 

ETG was charged with determining the availability, 

uses, cost, and accuracy of equipment to fulfill the 

needs of the LTPP program to measure load on the 

pavement test sections.11

Members

Lloyd Henion

Perry Kent 

Billy M. McCall

Tom Neukam

Expert Task Group on Environmental Da

Scope

The ETG assisted SHRP in the development of the 

climatic database, advising on the establishment of 

on-site weather stations to complement the “virtual” 

weather stations, the retention of both raw and composite climatic data obtained from the Canadian and 

U.S. weather services, data elements to be included, 

and the algorithm for deriving site-specific estimates 

from the climatic data.12,13

Members

Richard L. Berge

Tom Christison

Walter Dabberdt

Barry J. Dempsey

LONG-TERM PAVEMEN

COMMITTEE (1996–pr

The FHWA contracted with TRB for provision of formal peer review regarding LTPP program matters. 

This contract has been renewed periodically and supports the continuation of the advisory committee, 

renamed the Long-Term Pavement Performance Committee (currently referred to as the LTPP Committee 

or LCOM), and its ETGs. The committee is appointed 

by, and acts through, the NRC.

Scope 

The role of the TRB LTPP Committee is to advise 

FHWA and AASHTO on the planning, implementation, and development and delivery of products of the 

LTPP studies. The committee also prepares reports, 

including letter reports, containing its “evaluations and 

suggested mechanisms to enhance the utility to the 

States of the studies’ outcomes.”14

Traditionally, individuals who are actively employed 

by highway agencies in the United States and Canada 

have occupied slightly more than half of the Committee’s membership seats, and one of these State appointees has served as chairperson. Participation in the 

development of the Committee’s advice to FHWA and 

AASHTO on the plans, operations, and accomplishments of the LTPP program affords the States and 

Provinces the opportunity to affect the future of this 

research program in which they are heavily invested. 

Currently, the LTPP Committee is a TRB Policy 

Study Committee that meets regularly to receive 

reports from the LTPP program staff, deliberate, and 

develop recommendations regarding current and 

John Griffith

David W. Phillips

Eugene Rasmusson
262 THE LONG-T

future activities related to the conduct and operation of 

the program. All members are required to comply with 

the conflict of interest and bias disclosure procedures of 

the NRC of the National Academies. Since 1997, the 

committee has submitted its findings to FHWA and 

AASHTO in the form of a formal review letter. The 

review letters are archived and available at the TRB 

Web site.15 At various times, the LTPP Committee has 

formed subcommittees to address specific issues, such 

as the Subcommittee on Program Improvement (March 

1997 to March 1999). The committee also sponsors the 

LTPP State Coordinators’ meetings and semi-annual 

meetings of the TRB Data Analysis Working Group.16

The TRB LTPP Committee has served since August 

1996. In 2006, however, the size of the committee and 

the number of ETGs were trimmed back, reflecting a 

reduction in LTPP activities and TRB funding.17 The 

ETGs are described separately for the periods before 

and after 2006. 

Members 

Allan L. Abbott

Roger Almond

Michael E. Ayers

Thomas E. Baker

Gary S. Carver

Charles J. Churilla

Lawrence W. Cole

R. Ronald Collins

Judith B. Corley-Lay

Dale S. Decker

Charles E. Dougan

Theodore R. Ferragut

Donald H. Freeman

Ralph C. G. Haas

Amir Hanna

Neil F. Hawks

Gary L. Hoffman

John R. Hosang

Patricia S. Hu

Randell H. Iwasaki

Henry G. R. Kerali

Russel W. Lenz

Joseph M. Leonardo

Aramis López

William J. MacCreery

Jim McDonnell

TRB LTPP Committee Expert Task Groups, 

1996–2006

Expert Task Group on LTPP Automated Dist

Identification / Distress Data Collect

and Analysi

Scope 

The ETG on LTPP Automated Distress Identification 

advised FHWA on planning and implementation of the 

collection and processing of 35-mm photographic 

records of pavement distress at LTPP test sections. The 

ETG provided advice intended to help solve operational problems with this activity; enhance the productivity of recording, identifying, and extracting the distress 

data; and assuring that the results addressed high-priority needs of State highway departments. Specific 

areas of activity included (1) programmatic review of 

the automated distress identification project’s objectives, priorities, and work plans; (2) technical assessment 

of ongoing work; (3) project-wide and task-specific 

progress assessment; and (4) recommendations to 

enhance project success. 

The ETG’s members were selected for their expertise with equipment and methods used for automated 

recording of visual images of pavement surfaces and 

extraction from these records of distress data suitable 

for analysis of pavement performance, and for their 

experience in pavement engineering, statistics, and 

data analysis. 

In 1999, at the ETG’s request, the LTPP Committee 

broadened the scope of this ETG and changed its name 

to the ETG on LTPP Distress Data Collection and 

Analysis. Although the ETG would continue to focus 

on automated identification of distress, its charge was 

widened to include “all aspects of collecting, processing, and uploading in the LTPP database data quantifying the type and extent of distress experienced by 

LTPP’s test sections.”18 The ETG served from July 1996 

until November 2005.

Members

Janice Arellano

Michael E. Ayers

William Bellinger

Carl Bertrand

James K. Cable 

Victor M. Mendez

Carl L. Monismith

Raymond K. Moore

Richard D. Morgan

Carol A. Murray

David E. Newcomb

Olga J. Pendleton

Charles A. Pryor, Jr.

Robert Raab

Frederick R. Ross

Robert L. Sack

Larry A. Scofield

Ted M. Scott II

Gary W. Sharpe

Richard K. Smutzer

Monte Symons

A. Haleem Tahir

Gary D. Taylor

William H. Temple

Robert Walters

C. Michael Walton

Kenneth I. Warren

Sarah Wells

Gary C. Whited

James McFarland Yowell

Loren Hill

Colleen A. Kissane

Donald Larsen

Charles Larson

Daris Ormesher
appendix a: Planning and advisory committees 263

Lawrence W. Cole

Gaylord Cumberledge

Tahar El-Korchi

Jon A. Epps

Roger Green

Wouter Gulden

Kent Hansen

Expert Task Group on LTPP Data Ana

Scope

The ETG on LTPP Data Analysis was organized to 

advise FHWA on matters related to the development, 

through analysis of LTPP data, of research products 

that are needed and will be used immediately by State 

highway agencies. Specific areas of activity include 

(1) development and prioritization of data analysis 

objectives; (2) technical assessment of work plans for 

specific analysis projects; (3) technical review and 

advice regarding ongoing analytical efforts; (4) program-wide and project-specific progress assessment; 

(5) participation in periodic assessment and update of 

the LTPP Data Analysis Plan; (6) technical review of 

LTPP data analysis reports; and (7) referral of data 

analysis products to the LTPP Implementation Technical Working Group.19 Members were selected for 

their technical expertise in the analysis of pavement 

performance data and experience in pavement engineering, statistics, and data analysis.

Members

Paul E. Benson

Lawrence Cole

Judith B. Corley-Lay

Guy Doré

Marc Eijbersen

Steve Goodman

Eric Harm

Lynne Irwin

Heikki Jamsa

Andrew M. Johnson

Henry Kerali

Bill Maupin

Karen McClure

Raymond K. Moore

Expert Task Group on LTPP Datab

Development and Operations

Scope 

The ETG provided advice to the LTPP Committee and 

FHWA on (1) the further development of the LTPP 

database including the refinement of existing data 

tables and the addition of new data tables, including 

“computed parameters” tables and tables for data currently stored offline; (2) the further development of 

tools (such as the DataPave software, or Web-enabled 

versions of the database) for improving the accessibility 

of the LTPP data; (3) priorities, plans, and options for 

improving the accessibility of LTPP data not currently 

included in the LTPP database that may be of interest 

and value to users of the LTPP data; (4) plans for longterm maintenance and operation of the LTPP database; 

and (5) storage and dissemination of offline data following the sunset of the LTPP research program. Members 

were familiar with pavement performance data, data 

analysis, information technology, the fundamentals of 

relational databases, and the LTPP database. 

The ETG’s purview included review of planning, 

implementation, and progress of LTPP database activities and advice regarding operational problems. 

Together with the TRB LTPP Committee, its other 

ETGs, and the Subcommittee on LTPP Product Development and Delivery, this ETG oversaw the planning 

and progress of LTPP projects to assure that their outcomes would lead to products addressing the high-priority pavement-related needs of State highway 

departments. The ETG served from October 2002 until 

November 2005.

Members

Roger L. Green

Leonnie Kavanagh

David P. Orr

Robert Raab

Shelley M. Stoffels

Joy F. Portera 

Robert Raab

Richard B. Rogers

Brian Schleppi

Shelley M. Stoffels

James Walls III

Shie-Shin Wu

Deborah Walker

Eric Weaver

John R. Weaver

Benjamin Worel

Michael Murphy

Neville Parker

Linda Pierce

Patricia Polish

Robert Raab

Cheryl A. Richter

Susan L. Tighe

Julie M. Vandenbossche

William Vischer

James Walls

Randy West

Thomas White

Larry Wiser

Wes Yang
264 THE LONG-T

Expert Task Group on LTPP Materials D

Collection and Analysis/Falling Weig

Deflectometer Data Collection and Analy

Scope

The ETG reviewed and advised the TRB LTPP Committee on matters relating to the collection, processing, and 

uploading materials properties data in the LTPP database. Established by the TRB LTPP Committee in 1999 

because of the high level of materials data issues being 

brought to the attention of the Automated Distress Identification ETG, the new ETG addressed materials-related questions such as the robustness of techniques for 

backcalculation of resilient modulus from nondestructive testing, the repeatability of laboratory testing of 

resilient modulus, the precision and bias of resilient 

modulus testing, and the pros and cons of resilient modulus versus dynamic modulus. The scope of this ETG 

later expanded to include the review and analysis of falling weight delectometer data. Thus, the name changed 

to Expert Task Group on Materials and Falling Weight 

Deflectometer Data Collection and Analysis. The ETG 

served from December 1999 until October 2006.

Members

Ahmad Ardani

Thomas Baker

Ramon Bonaquist

Bruce Dietrich

Jon Epps

Michael A. Heitzman

Said Kass

Richard Kim

Mark McDaniel

Expert Task Group on Product Developme

and Deliver

Scope

The ETG provided technical advice to the TRB LTPP 

Committee on matters related to identification of LTPP 

products, the efforts to develop these products, and the 

plans to deliver these products to the State highway 

agencies. The ETG’s advice helped solve operational 

problems encountered in these activities, enhanced the 

productivity of the LTPP program, and assured that the 

program’s results address the high-priority needs of the 

States. Members included several members of the TRB 

LTPP Committee and other individuals who are well 

acquainted with the potential of the LTPP program to 

generate products of value to the highway community, 

including representatives of State transportation departments, transportation technology associations, consulting engineering firms, and universities. The ETG served 

from August 1999 to October 2003.

Members

James K. Cable

Ewa Flom

Antonio Nieves

Michael Moravec

Charles A. Pryor, Jr.

Larry A. Scofield

Expert Task Group on State Usage of

the LTPP D

Scope

The ETG on State Usage of the LTPP Data provided 

advice to the FHWA and AASHTO on the unique 

needs of State departments of transportation (DOT) 

regarding access to and use of data residing in the 

LTPP database. Activities of this committee included 

(1) evaluation of database users’ service procedures, 

(2) evaluation of database user guides and other documentation, (3) evaluation of specific data delivery 

formats to afford ease of use, and (4) appraisal of the 

capacity of State DOTs to use LTPP data in DOTstaffed research and management activities.

Members

Judith Corley-Lay

Andrew Johnson

Ben Worel

Danny Dawood

Gary Sharpe

George Cochran

Guy Doré

Expert Task Group on Traffic Data Collecti

and Analysi

Scope

The ETG advised the TRB LTPP Committee, FHWA, 

and AASHTO on matters related to collection, processing, uploading in the LTPP database, and analysis of 

Rebecca S. McDaniel

Samuel Miller

David Newcomb

Robert Raab

Stephen Shober

Jack Springer

A. Haleem Tahir

Marshall Thompson

A. Haleem Tahir

Gary D. Taylor

Robert Raab

Monte Symons

Bing Wong

Jamshid Armaghani

John Hallin

Linda Pierce

Robert Raab

Shakir Shatnawi

Wes Yang
appendix a: Planning and advisory committees 265

traffic data collected at LTPP test sites in the United 

States and Canada. The ETG provided comments and 

advice intended to help solve operational problems 

encountered in these activities. The work of the ETG 

was to facilitate the accumulation in the LTPP database of high-quality traffic data in quantities sufficient 

to support LTPP analysis projects. These projects are 

designed to produce outcomes that lead to products 

addressing the high-priority pavement-related needs 

of State/Province highway departments. The work of 

the ETG also included reviewing those parts of the 

plans, activities, and progress of the LTPP program’s 

data analysis and product development activities that 

pertain to the use of LTPP traffic data, and reporting its 

findings and suggestions to the TRB LTPP Committee. 

The ETG served from 1992 to 2013.

Members

Allan L. Abbott

David Albright

David Cebon

Wiley Cunagin

Curtis Dahlin

Ralph E. Folsom

Ralph Gillmann

Kris Gupta

Ed Green

Jerry J. Hajek

John Hamrick

Andrew Horosko

Patricia S. Hu

Bruce Hutchinson

Frank Jarema

Steven Jessberger

Ed Kashuba

James Kramer

Catherine T. Lawson

William Lofroos

Bill McCall

TRB LTPP Committee Expert Task Groups, 

2006–2013 

In 2006, as a result of budget constraints imposed on 

the LTPP program, the number of ETGs providing support to the TRB LTPP Committee was reduced to two: 

the TRB ETG on LTPP Traffic Data Collection and 

Analysis continued to provide the same functions as it 

had since 1992, and a multipurpose ETG on LTPP Special Activities was created to encompass many of the 

functions of the ETGs that were discontinued. Thus, 

between 2006 and 2013, the TRB LTPP Committee, 

with the support of the Traffic Data and Special Activities ETGs, provided the formal peer review functions 

for all LTPP-related activities. In 2013, the Traffic Data 

ETG was retired and its remaining responsibilities were 

folded into those of the Special Activities ETG.

Expert Task Group on LTPP Special Activit

Scope

The Special Activities ETG, referred to as LSPEC, 

advises the TRB LTPP Committee on matters related 

to collection, processing, uploading into the LTPP 

database, and analysis of all data, including traffic data 

as of 2013, that have been recorded at or determined 

from samples collected at LTPP test sites. The work of 

the ETG facilitates the accumulation in the LTPP database of high-quality data in quantities sufficient to support LTPP analysis projects. These projects were 

designed to produce outcomes addressing the highpriority, pavement-related needs of State highway 

agencies. The ETG’s scope of work includes reviewing 

the plans, activities, and progress of various aspects of 

the LTPP studies, including materials data collection 

and analysis, distress and profile data collection and 

analysis, data analysis, product development and delivery, and database development and operations. 

Members

James K. Cable

Judith B. Corley-Lay

Tahar El-Korchi

Michael Alan Heitzman

Yan “Jane” Jiang

Andrew M. Johnson

Catherine T. Lawson

Aramis López

Rebecca S. McDaniel

David P. Orr

Expert Task Group on LTPP Traffic D

Collection and Analysis (see 1996–2006

ETG section above; retired in 2013

Anne-Marie McDonnell

Andrew Nichols

George Novenski

Olga Pendleton

Alan Pisarski

Richard Quinley

Robert Raab

Richard L. Reel, Jr.

Richard Rogers

Larry Schoenhard

Larry A. Scofield

Elizabeth Stolz

Ronald Tweedie

John Van Berkel

Deborah Walker

George Wass

John Weaver

Richard Weed

Larry Wiser

Clyde Woodle

Robert Raab

Richard L. Reel, Jr.

Jack Springer

Shelley M. Stoffels

Gary D. Taylor

Susan L. Tighe

Deborah Walker

Larry Wiser

Benjamin James Worel

Wei-Shih Yang
266 THE LONG-T

Created under thePavementPerformance Advisory

Committee in the early 1990s and still supported by

the LTPP Committee, the TRB Data Analysis Working Group (DAWG) provides a continuing forum for

discussion of methods of analysis of pavement performance data. The first DAWG meeting was held in

January 1992 at the Annual TRB Meeting. Presentations at DAWG meetings emphasize the development of techniques for extracting and analyzing

data, results of model building, and development of

transfer functions linking structural response to

distress. The usual DAWG meeting has a minimum

of formality to encourage open discussion and minimize the time between preparation and dissemination of analytical results. DAWG meetings are held

twice each year: immediately preceding the TRB

Annual Meeting in Washington in January, and

approximately at the midyear at another location in

conjunction with a major conference that DAWG

members are likely to attend in large numbers.

Members

Gabriel Assaf

Harold Augustin

Gilbert Baladi

Paul Benson

Allesandra Bianchini

Karim Chatti

Charles Copeland

Brian Cox

Michael Darter

Jerome Daleiden

Gianluca Dell’Acqua

A. G. Dumont

Brian Walter Ferne

William O. Hadley

Amir Hanna

Neil F. Hawks

Heikki Jämsä

Keizo Kamiya

Henry Kerali

Anthony Lawrence

Bojan Leben

Johann Litzka

Kang-Won Wayne Lee

Robert Lytton

James William Maina

Robert Mason

Louay N. Mohammad

Jostein Myre

Athanassios Fotios

Nikolaides

DATA ANALYSIS W

Ahmed Samy Noureldin

Emmanuel Owusu-Antwi

A. Thomas Papagiannakis

William D. O. Paterson

Olga J. Pendleton

John F. Potter

Jorge A. Prozzi

Robert Raab

Brent Rauhut

James Rosenberger

Shahed Rowshan

Luis de Picado Santos

James Sherwood

Gordon Sparks

Mate Sršen

Wynand Jacobus van der

Merwe Steyn

Govert Sweere

Rafiqul Alam Tarefder

Shiraz Tayabji

Paul Teng

Thorkild Thurmann-Moe

Francesca La Torre

Waheed Uddin

Gerhard Van Blerk

Larry Wiser

Haifang Wen

Greg Williams
appendix a: Planning and advisory committees 267

REFE

 1. “TRB Long-Term Pavement Performance (LTPP) 

Committee (B0135).” Web page. https://www.mytrb.

org/CommitteeDetails.aspx?CMTID=4173.

 2. “TRB Committees Related to Pavements Web page. 

http://www.trb.org/Pavements/TRBCommittees.aspx.

 3. America’s Highways: Accelerating the Search for 

Innovation (Special Report 202). Transportation 

Research Board, National Research Council, 

Washington, DC, 1984.

 4. Strategic Highway Program Research Plans, Final 

Report. Transportation Research Board, National 

Research Council, Washington, DC, May 1986. 

 5. Federal Highway Administration’s Commitment to 

the Strategic Highway Research Program: PastPresent-Future. January 1990. Available from LTPP 

Customer Support Service Center (ltppinfo@dot.gov).

 6. Long-Term Pavement Performance Committee. 

Preserving and Maximizing the Utility of the Pavement 

Performance Database. Transportation Research Board, 

Washington, DC, 2009, p. vii. http://onlinepubs.trb.org/

Onlinepubs/sp/ltpp_report_2009.pdf.

 7. PCS/Law Engineering. Layer Moduli Backcalculation 

Procedure: Software Selection (SHRP-P-651). Strategic 

Highway Research Program, National Research 

Council. October 1993. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-651.pdf.

 8. PCSLaw Engineering. SHRP’s Layer Moduli 

Backcalculation Procedure (SHRP-P-655). Strategic 

Highway Research Program, National Research 

Council, Washington, DC, August 1993, pp. 2, 18. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-655.pdf.

 9. W. O. Hadley. SHRP LTPP Overview: Five-Year Report

(SHRP-P-416). Strategic Highway Research Program, 

National Research Council, Washington, DC, June 1994, 

pp. 245–46. http://onlinepubs.trb.org/onlinepubs/

shrp/SHRP-P-416.pdf. 

 10. J. L. German and C. R. Copeland, Jr. SHRP-LTPP 

Traffic Data Collection and Analysis: Five-Year Report

(SHRP-P-386) (W. O. Hadley, Ed.). Strategic Highway 

Research Program, National Research Council, 

Washington, DC, March 1994, pp. 2–4. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-386.pdf. 

 11. J. L. German, C. R. Copeland, Jr., and W. O. Hadley 

(Eds.). SHRP LTPP Traffic Data Collection and Analysis: 

Five-Year Report (SHRP-P-386). Strategic Highway 

Research Program, National Research Council, 

Washington, DC, March 1994, pp. 2–5. http://

onlinepubs.trb.org/onlinepubs/shrp/SHRP-P-386.pdf.

 12. G. R. Rada. SHRP-LTPP Monitoring Data: Five-Year 

Report (SHRP-P-696). Strategic Highway Research 

Program, National Research Council, Washington, DC, 

August 1994, pp. 59–64. http://onlinepubs.trb.org/

onlinepubs/shrp/SHRP-P-696.pdf. 

 13. PCS/LAW Engineering. Development of the LTPP 

Climatic Database (SHRP-P-621). Strategic Highway 

Research Program, National Research Council, 

Washington, DC, January 1993. http://onlinepubs.trb.

org/onlinepubs/shrp/SHRP-P-621.pdf.

 14. “TRB Long-Term Pavement Performance (LTPP) 

Committee (B0135).” Web page. https://www.mytrb.

org/CommitteeDetails.aspx?CMTID=4173.

 15. “TRB Policy Study Letter Reports and Other Brief 

Reports.” Web page. http://www.trb.org/publications/

pubspolicystudiesletterreports.aspx.

 16. Long-Term Pavement Performance Studies Web page. 

http://www.trb.org/LTPPProgram/LTPPProgram.

aspx.

 17. V. M. Mendez. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 22). Dec. 18, 2006, 

p. 1. http://onlinepubs.trb.org/Onlinepubs/sp/ltpp_

letter_22.pdf.

 18. A. L. Abbott. Long-Term Pavement Performance 

Committee Letter Report (Letter No. 5) Apr. 1, 1999, 

p. 4. http://onlinepubs.trb.org/onlinepubs/sp/ltpp_

letter_5.pdf.

 19. C. J. Churilla. “FHWA’s Implementation Plan for SHRP 

Products.” Public Roads, Winter 1994. http://www.

fhwa.dot.gov/publications/publicroads/94winter/

p94wi24.cfm.

appendix B: contract services 269

INTRODU

The LTPP program relies upon technical, scientific, 

and management expertise in the private sector to 

carry out different aspects of its mission. Under the 

program’s leadership, contractors provide the skilled 

personnel needed to implement a research program of 

this magnitude. Contractual relationships with engineering and consulting firms, testing laboratories, and 

equipment manufacturers have been essential in planning the program’s experiments, managing the collection and quality assurance of the data, building the 

program’s Information Management System (IMS), 

conducting analyses, and producing results. 

This appendix lists briefly the key contracts that 

have been instrumental in achieving the program’s 

objectives and acknowledges many of the firms that 

have contributed to the LTPP program. The list is not 

comprehensive, and many equipment, instrumentation, and data analysis contract services used by the 

program may not be described below due to the difficulty of retrieving historical information. Contracts in 

place under the leadership of both the Strategic Highway Research Program (SHRP) between 1987 and 1992 

and the Federal Highway Administration (FHWA) 

from 1992 through the present are listed. More detail on 

the types of activities carried out by some of the contracts listed below is provided in chapter 2.

PEER REVIEW C

During the transition of the LTPP program from SHRP 

to FHWA, a 15-month contract with the National 

Appendix 

Contract Services Acquired to Operate

the LTPP Prog
270 THE LONG-TERM PAV

Research Council, National Academies, continued the 

services of the Pavement Performance Advisory Committee, its supporting expert task groups, and the LTPP 

regional engineers. The contract also assigned responsibility for the international coordination activities 

associated with the Transportation Research Board 

(TRB) annual meeting to FHWA. Later, the services of 

the LTPP regional engineers were included in the 

technical support services contract. After this transitional period, FHWA contracted with TRB to continue 

advisory services to the LTPP program, and the committee was renamed the LTPP Committee. This contract has been modified and renewed periodically. The 

National Research Council has been the primary conduit for peer exchanges among the LTPP Team, its 

senior management, and the program’s stakeholders 

and partners. Appendix A provides a detailed description of the advisory committees and expert task groups. 

TECHNICAL SUPPORT CO

Objective

The original objective for this contract during the 

SHRP management years was to provide the technical 

and management services needed to develop and conduct the LTPP studies and to build and maintain the 

LTPP database. These same services and more have 

been required during the FHWA management years. 

In particular, from 1992 until 2002, the services of the 

LTPP regional engineers were included in the contract. In 1997, the development, refinement, and assessment of traffic data collection activities were added. 

The contract also provided customer support services 

until 2006, when this function was transferred to the 

LTPP Team and its onsite General Administration Support contractor. The technical support contract, however, continues to provide support, as needed, for 

customer-related data requests and information.

SHRP-LTPP Contractor

Texas Research and Development Foundation (prime)/ 

University of Texas Center for Transportation 

Research/Pavement Consultancy Services, Inc. 

FHWA-LTPP Contractors

Pavement Consultancy Services (prime), later acquired by 

LAW Engineering; LAW later acquired by MACTEC 

Engineering and Consulting, Inc.; MACTEC later 

acquired by AMEC Environment & Infrastructure, 

Inc./Science Applications International Corporation/

Soil and Materials Engineers, Inc. 

ReGiOnaL SUppORT COnTRaCTS

Objective

The objective for these contracts during SHRP management and now under FHWA management is to

implement consistent data collection, data processing,

and data quality activities to support the LTPP program objectives for test sections across each of the four

LTPP geographical boundaries: North Atlantic, North

Central, Southern, and Western Regions. The contract

services also require close coordination with the highway agencies to carry out these primary activities.

In each region, an LTPP engineer was assigned to 

oversee the daily operations of the regional staff. These 

regional engineers were employees of SHRP, and later 

FHWA continued their services through a mix of contractual and employment arrangements. Ivan Pecnik 

(North Atlantic Region), Dick Ingberg (North Central 

Region), Homer Wheeler and Morris Reinhardt 

(Southern Region), and Calvin Berge (Western Region) 

all served in this capacity until they retired or the 

regional engineer staffing was ended in 2002.

SHRP-LTPP Contractors

Pavement Management Systems, Ltd. (prime)/ 

Austin Research Engineers, Inc. (LTPP North

Atlantic Region)

Braun Pavement Technology (prime)/Soil and

Materials Engineers (LTPP North Central Region)

Brent Rauhut Engineering, Inc. (LTPP Southern Region)

Austin Research Engineers, Inc. (LTPP Western Region)

Nichols Consulting Engineers, Chtd. (LTPP Western

Region)
appendix B: contract services 271

FHWA-LTPP Contractors

Pavement Management Systems, Ltd., later acquired 

by Stantec (LTPP North Atlantic Region) 

Braun Pavement Technology (prime)/Soil and 

Materials Engineers (LTPP North Central Region) 

ERES Consultants (LTPP North Central Region) 

Stantec (LTPP North Central Region) 

Brent Rauhut Engineering, Inc., later acquired by 

Fugro Consultants; Fugro now Fugro Roadware 

(LTPP Southern Region) 

Nichols Consulting Engineers, Chtd. (LTPP Western 

Region) 

general adminis

SUPPORT CONTR

Objective

To accomplish the program objective, this contract 

provides onsite engineering and technical support 

services to the LTPP program manager at FHWA’s 

Turner-Fairbank Highway Research Center. The services under the contract include technical support 

activities such as teaching the LTPP distress workshops; updating and maintaining the Data Analysis/

Operations Feedback Report activities; maintaining 

the LTPP program documents and files, publications, 

Reference Library, Strategic Plan for LTPP Data Analysis, Web page, and mailing and email distribution lists; 

assisting in drafting and reviewing the LTPP newsletter; working at the LTPP exhibit booth at the TRB 

Annual Meeting and other conferences; and more 

recently, in 2006, handling all data and information 

requests from users sent to the LTPP Customer Support Service Center. This type of contract did not exist 

under SHRP management.

FHWA-LTPP Contractors

EBA Engineering, Inc.

LENDIS Corporation

ECOMPEX

Engineering & Software Consultants, Inc. (ESCINC)

DATA COLLECTIO

CONTRAC

The equipment and instrumentation contracts provide 

the engineering and technical support services needed 

to collect the various types of data at the LTPP test sections. The contract services during the SHRP management years focused on developing, testing, and 

establishing standard protocols for the equipment 

used to collect the pavement data. In the early years of 

the LTPP program, some of the data collection equipment simply did not exist, and the contractors selected 

played a major role in developing the first-generation 

data collection equipment used by the program. The 

LTPP program has raised the bar for collecting quality 

data which has encouraged industry to improve not 

only how they collect the data, but also how they manufacture the equipment used to collect the data. As a 

result, many equipment manufacturers and vendors 

have changed their practices and are continually 

improving their technology, when necessary. With the 

passing of time, technology has improved, providing 

FHWA management more equipment options from 

which to choose. 

The services provided by the many equipment manufacturers and vendors over three decades are too 

numerous to discuss in this appendix, but those relating to major data collection efforts are briefly described.

Photographic Pavement Distress Contra

Objective

The services provided under this contract were to perform periodic surface distress surveys using continuous 35-mm black-and-white photography for the 

purpose of obtaining a permanent historical record of 

the pavement condition over the full length and width 

of the LTPP test sections, and to interpret the distress 

data (type, severity, and quantity) from these photographic records. To achieve this, survey vehicles operated at highway speeds and all surveys were done at 

night under controlled, artificial lighting. The reduction of distress data from the film was done in the office 

using a software and film-handling system, which consisted of a computer, a film transport device with a 

digitizing tablet for viewing and digitizing images from 

the 35-mm films, a printer for preparing reports, and 
272 THE LONG-TERM PAV

an inkjet plotter for producing color distress maps. The 

actual film interpretation was comparable to performing a typical manual distress survey; that is, the type, 

amount, and severity of the distresses existing in the 

test section were observed and recorded.1

Contractor

PASCO USA was the contractor under both SHRP and 

FHWA management. The company later sold their 

North American rights and equipment to Cumberledge, Gramling and Hunt, which was later acquired 

by Applied Research Associates, Inc.

Falling Weight Deflectometer Contract

Objective

The services required under this contract are to provide 

new falling weight deflectometer (FWD) systems or to 

refurbish existing systems to perform structural evaluation of the LTPP test sections, calibration, scheduled 

and unscheduled maintenance and repair; provide 

replacement parts; and provide updated software, training, and technical support to the LTPP regional FWD 

operators. The contract agreements have provided 

either complete overhaul of the FWD units used by the 

LTPP program or complete replacement of the units.

Contractor

Dynatest USA was the contractor under SHRP management and has continued under FHWA management.

Falling Weight Deflectometer Calibration Center

and Operational Improvements Contract

Objective

The objective of this contract was to upgrade the existing FWD calibration system hardware and software to 

take advantage of improvements in technology. These 

upgrades would make calibration sustainable for the 

next decade without a loss of quality while ensuring 

that any new procedures are compatible with all brands 

of FWDs sold in the United States. The contract also 

provided a plan for permanent support of the four 

LTPP calibration centers through the American Association of State Highway and Transportation Officials 

(AASHTO) Materials Reference Laboratory. This contract did not exist under SHRP management.

FHWA-LTPP Contractor

Cornell Local Roads Program, Cornell University

Inertial Road Profiling Contract

Objective

The services required under this contract are to provide noncontact inertial road profiling equipment 

capable of measuring and recording the road surface 

profile in both wheelpaths at normal highway speed, 

perform scheduled and unscheduled maintenance and 

repair, and provide training and technical support to 

the LTPP regional profiler operators. Later, under 

FHWA management, the latest profiler units were also 

equipped to collect pavement macrotexture data and 

ambient and surface temperatures with Global Positioning System coordinates.

SHRP-LTPP Contractor

K. J. Law

FHWA-LTPP Contractors

K. J. Law

International Cybernetics Corporation

Ames Engineering, Inc.

TRAFFIC DATA COLLECTION 

Objective

Traffic data collection contracts awarded by FHWA in 

the early 2000s address the missing traffic data at the 

Specific Pavement Study (SPS) -1 (structural factors for 

flexible pavements), -2 (structural factors for rigid 

pavements), -5 (rehabilitation of asphalt concrete 

pavements), and -6 (rehabilitation of jointed Portland 

cement concrete pavements) projects. Funding limitations restricted the LTPP program from collecting 

quality, monitored traffic data at the SPS-8 (environmental factors in the absence of heavy loads) projects 

which were included in the original data collection 

plan (see chapter 7).

The contractual services provide a central mechanism to ensure that the traffic data collection equipment is routinely calibrated, validated, and, when 

necessary, replaced and that the data collected by the 
appendix B: contract services 273

equipment installed at the SPS sites are uniformly 

checked on a regular basis. These contracts are conducted under two concurrent phases with a separate 

contractor for each phase. The Phase I contractor performs the field calibration and validation activities for 

the traffic data collection equipment, and the Phase II 

contractor installs and maintains the equipment. The 

contracts were initiated under the LTPP SPS Traffic 

Data Collection Pooled-Fund Study, which was an outcome of the LTPP Program Improvement Campaign 

(see chapter 11), and thus did not exist under SHRP 

management.

Weigh-in-Motion Field Calibration and

Validation Contracts 

The services provided under these contracts are to 

verify that the weigh-in-motion (WIM) systems at the 

SPS sites are operating at peak performance and to 

document the reliability of the data being collected. If 

the WIM systems are not meeting the LTPP accuracy 

requirements, the contractor must identify the problems and recommend corrective actions, as well as 

supporting rationales for these actions. 

FHWA-LTPP Contractors

MACTEC Engineering and Consulting, Inc.

Applied Research Associates, Inc.

Installation, Maintenance, and Data Services f

Weigh-in-Motion Systems Contracts

The services provided under these contracts are to 

install and calibrate WIM systems that would provide 

research-quality traffic data (defined to be at least 210 

days a year of data of known calibration, meeting 

LTPP’s accuracy requirements) for 5 or more years at 

SPS sites that either did not have an operational WIM 

system, or that had been recommended by the 

contractor performing the WIM field calibration and 

validation activities to replace the equipment. The 

services also include maintenance of the WIM systems installed and replacement of the systems, if 

necessary. In addition, daily verification checks are 

also part of the contract services. 

FHWA-LTPP Contractor

International Road Dynamics, Inc.

MATERIALS CON

Objective

Materials contracts awarded by SHRP and FHWA cover the collection of materials samples at the LTPP test 

sections and laboratory testing of the collected samples. The contract services are performed either 

regionally or centrally and the laboratory testing 

results are entered into the LTPP database.

Materials Drilling and Sampling Contract

The services provided under these contracts were to 

perform drilling and materials sampling at the LTPP 

test sections and to label with source information, 

package, and ship the collected samples to the appropriate laboratory testing facility. During SHRP management, these services were performed by firms 

within each region rather than through one central 

contract. 

SHRP-LTPP Contractors

Westinghouse Environmental and Geotechnical 

Services

Professional Service Industries, Inc. (LTPP North 

Atlantic Region)

Braun Engineering Testing (LTPP North Central 

Region)

LAW Engineering (prime)/Southwest Labs 

(LTPP Southern Region)

Chen-Northern (LTPP Western Region)

FHWA-LTPP Contractor

Braun Intertec

Materials Reference Library Contracts

The services provided under these contracts are to 

store loose and core forms of highway materials 

(asphalt concrete, Portland cement concrete, natural 

aggregates) from the LTPP test sections and provide a 

climate-controlled room to house 35-mm films that 

contain images of the LTPP test sections. Other pavement research programs have also stored their materials at the Materials Reference Library (MRL). The 

SHRP Asphalt program contract established the MRL 

at a facility in Austin, Texas. This contract ended in 
274 THE LONG-TERM PAV

1993, and the materials were relocated to a facility in 

Reno, Nevada, under FHWA management.

SHRP-LTPP Contractor

University of Texas at Austin

FHWA-LTPP Contractors

Nichols Consulting Engineers, Chtd.

Sierra Transportation Engineers, Inc.

DATA STOAGE 

CONTRACT

Objective

The original objectives for these contracts during the 

SHRP management years were to provide the technical and management services needed to build and 

maintain the IMS and to ensure continuity, stability, 

and access to the LTPP data. Under FHWA management years, the contract services have been expanded 

to include new data elements collected from the LTPP 

test sections and the creation of a Web-based data 

entry portal that allows for real-time loading of data 

from the LTPP regional support contractor offices 

directly to the national LTPP database. In more recent 

years of the LTPP program, a contract independent of 

the IMS contracts was put in place to improve user 

access to the LTPP data and other program information.

Information Management System Contract

The services provided under these contracts have been 

to organize and implement the LTPP IMS, its national 

node in Washington, DC, and the four LTPP regional 

nodes. The specific services include installation of the 

National IMS (NIMS) at the TRB, National Research 

Council, facilities in Washington, DC, and the necessary interfaces between the program and contractor 

offices to allow flexible access to the data for a national 

analysis program; installation of the regional IMS 

(RIMS) nodes at the four regional contractor offices, 

and the necessary interface and quality control subsystems among the regional, LTPP program, and IMS 

contractor offices; and documentation and training to 

allow operation of the RIMS and NIMS by the program 

and contractor staff. Under FHWA, these services have 

been provided from locations in Oak Ridge, TN; Beltsville, MD; and McLean, VA.

SHRP-LTPP Contractor

Science Applications International Corporation

FHWA-LTPP Contractors

Pavement Consultancy Services, later acquired by LAW 

Engineering (prime); LAW later acquired by MACTEC 

Engineering and Consulting, Inc.; MACTEC later 

acquired by AMEC Environment & Infrastructure, 

Inc./Science Applications International Corporation/

Soil and Materials Engineers, Inc.

DataPave Online Contrac

The services provided under this contract were to 

develop a Web-based system to provide continuous 

user access to LTPP data, documents, and related program information. This type of contract did not exist 

under SHRP management. The contract covered the 

development of DataPave Online and its expanded system, Products Online, which included other LTPP 

products (see chapter 10).

FHWA-LTPP Contractor

iENGINEERING Corporation 

Web Interface Portal Contrac

The services provided under this contract have been to 

develop, enhance, maintain, and support an effective 

Web interface program for the LTPP IMS. This Webbased system, known as LTPP InfoPaveTM, provides 

on-demand access to the LTPP database, Ancillary 

Information Management System, and products and 

tools to help maximize understanding and use of the 

data and other program information. This type of contract did not exist under SHRP management.

FHWA-LTPP Contractor

iENGINEERING Corporation 
appendix B: contract services 275

DATA ANALYSIS C

Objective

The LTPP program has contracted with many consultants, researchers, private firms, and universities—too 

many to list in this appendix—to examine the LTPP 

data over its nearly three decades. Details on the contractors that have conducted LTPP data analysis can be 

found by viewing the Strategic Plan for LTPP Data 

Analysis at http://www.fhwa.dot.gov/research/tfhrc/

programs/infrastructure/pavements/ltpp/analysisplan/index7print.cfm. 

The objective for the key data analysis contract during SHRP management was to perform the initial analysis studies for the first five LTPP program objectives. 

The activities for this first data analysis contract 

included the evaluation of existing design methods, 

improved design equations, effects of load and environment on pavement distress and performance, 

effects of specific design features on pavement performance, and evaluation of the design equations in the 

AASHTO Pavement Design Guide2 in light of empirical–mechanistic analysis techniques. In the principal 

data analysis contract, LTPP data were extracted and 

processed to create analytical databases tailored to the 

planned calculations. During this process, data gaps, 

overlaps, and other inconsistencies were identified for 

correction in the LTPP database portion of the IMS. 

Also, preliminary distress-specific pavement performance models were developed and sensitivity analyses 

were conducted to identify those variables having the 

strongest influence on specific distresses. In the secondary, smaller data analysis contract, efforts focused 

on the mechanistic evaluation of the AASHTO flexible 

pavement design equation and led to the identification 

of procedures in the AASHTO Pavement Design Guide 

that were inconsistent with a mechanistic model for 

pavement structures.

FHWA has used the Broad Agency Announcement 

(BAA) contract mechanism twice to award research 

projects involving innovative analysis approaches, 

novel ideas, and new methods of using LTPP data and 

information that will result in a better understanding 

of pavement performance. The primary objective of 

the BAAs was to derive useable and useful interim 

advances, with immediate applications in the areas of 

pavement design, construction, and evaluation practice, through analysis of the LTPP data.

The BAA projects provide the basis for identifying 

and developing products that engineers and managers 

can apply to design more cost-effective and better performing pavements. Four projects were performed 

under the first BAA between 1994 and 1996, and 12 

projects will be performed under the second BAA 

between 2014 and 2016.

SHRP-LTPP Contractor

Brent Rauhut Engineering, Inc. (prime)/ERES 

Consultants

FHWA-LTPP Contractors

AMEC Environment & Infrastructure, Inc.

Applied Research Associates, Inc.

Braun Intertec Corporation

Brent Rauhut Engineering, Inc.

ERES Consultants, Inc.

Fugro Roadware, Inc.

Michigan State University

Nichols Consulting Engineers

Quality Engineering Solutions, Inc.

Soil & Materials Engineers, Inc.

REFER

 1. G. R. Rada, A. L. Simpson, and J. E. Hunt. “Collecting 

and Interpreting Long-Term Pavement Performance 

Photographic Distress Data: Quality Control-Quality 

Assurance Processes.” Transportation Research Record: 

Journal of the Transportation Research Board 1889,

2004, pp. 97–105. http://trb.metapress.com/

content/7n8521p086085726.

 2. AASHTO Interim Guide for Design of Pavement 

Structures. American Association of State Highway and 

Transportation Officials, Washington, DC, 1972, rev. 1981. 

appendix C: equipment, instrumentation, and software 277

INTRODU

The LTPP program has used state-of-the-art equipment and technology to collect high-quality data. In 

many cases, the devices and software used to collect, 

process, and perform quality control/quality assurance 

(QC/QA) on the data have been created by the SHRPLTPP and FHWA-LTPP contractors because the technology either did not exist or did not meet the 

performance needs of the program.

The following sections describe some of the equipment used by the program over the years. In addition, 

this appendix also covers the software used for processing and performing QC checks of the data collected. Please note that the information contained in the 

following pages is not a complete list of the equipment 

or the software used by the program, but this additional information is being provided because it may be of 

value. More complete information about each type of 

data collection equipment and software used to process the data can be found in other documents published by the LTPP program, many of which are 

referenced throughout this report, particularly in 

chapter 6 and chapter 7.

AUTOMATED WEATH

EQUI

The automated weather station (AWS) equipment 

installed at the SPS-1 (structural factors for flexible 

pavements), -2 (structural factors for rigid pavements), 

and -8 (environmental factors in the absence of heavy 

loads) projects included: 

Appendix 

Data Collection Equipment, Instrumentatio

and Software Used in the LTPP Progr
278 THE LONG-TE

•	 UT3 weather tower with a Vaisala HMP 35 RH/

ATP probe (measured air temperature and relative 

humidity).

•	 R. M. Young 05103 wind speed and wind direction

probe.

•	 Licor L1-200x pyranometer (measured solar radiation).

•	 Model 380-L and 385-L (electrically heated)tipping

bucket rain and snow gauges. 

•	 CSI CR10 Datalogger (collected and stored the instrumentation data).

•	 12-volt DC PS 12 LA storage battery.

•	 MSX10 solar panel.

The LTPP regions with SPS projects in freeze zones 

were provided with heated tipping buckets (figure C.1) 

that required 110-volt service to power the heater.

AWS Datalogger and Storage Uni

Software routines for the Campbell Scientific, Inc. 

(CSI)CR10Dataloggerwere developed as aDOS-based

program that was downloaded to the CR10 Dataloggers.1

 This program complemented the field data collection and calibration activities by controlling the 

field data collection functions and providing the file 

format for storage of the instrumentation data. In 

2004, the DOS-based program was updated to work

with CSI’s PC208W program, which was based on

Microsoft Windows®.

In 1997, the installation of modems at each AWS 

location to allow for remote data download became a 

requirement.2 Modems were added to sites that could 

be provided with landline telecommunications at a reasonable cost (figure C.2), and cellular packages were 

added to sites that were not phone-line accessible.

FALLING WEIGHT DEFL

EQUI

Prior to the implementation of the SHRP program, 

very little falling weight deflectometer (FWD) data had

been collected. Since deflection data were to be a key 

data element in the LTPP program, FWD units were

purchased and evaluated for deflection data collection.

The first four FWD units for the LTPP program

were procured from Dynatest® in 1988. The FWDs

were towed by a 1988 GMC diesel van (figure C.3) and

were equipped as follows:

•	 An 8000 series processor.

•	 A laptop computer.

•	 A Dynatest DOS v20 FWD field program.

•	 A load cell.

•	 Two solid load plates (300 mm and 600 mm).

•	 Seven deflection sensors.

•	 Eight 55-lb (25-kg) weights.

•	 A trailer with dual axles.

•	 An enclosed body (a special-order item to allow the

units to travel to numerous locations and remain secure when parked at hotel or airport parking lots).

Five-year maintenance programs were included 

with the procurement, requiring the FWDs to be delivered annually to the manufacturer for service.

Figure C.2. Modem attached to Datalogger for transmitting data via landline to the respective LTPP re

support contractor’s office computer.

Figure C.

Heated tipping 

bucket rain gauge.
appendix C: equipment, instrumentation, and software 279

Since the purchase of the first set of FWD units in

1988, the LTPP program has made a concerted effort to 

maintain the equipment. Driven by budget restrictions,

in some years, the program found it more economical to 

refurbish the units instead of replacing them altogether. 

The manufacturer refurbished the FWD units in the

early years of the LTPP program, but in later years, the 

LTPP regional support contractors were given the 

option to refurbish the units using the expertise of their 

staff or by sending the units to the manufacturer. All 

units, whether new or refurbished, are required to pass 

the reference calibration at one of the regional calibration centers (see chapter 6 for more detail) prior to collecting deflection data at the LTPP test sites. Table C.1 

lists the FWD equipment used in the LTPP program

from 1988 to 2014.

FWD Buffer

The Dynatest DOS v20 FWD field program had the

option of smoothing the FWD load and deflection

peaks, as typically a 2-point peak occurs at the time of 

initial impact and full loading of the buffers. For the 

LTPP program, no smoothing was applied as the desire 

was to provide data in an unadjusted state. The flat buffers that initially came with the FWD units were problematic in that they provided too harsh a contact, 

which resulted in a very uneven peak. To alleviate this, 

Dynatest conducted a rotating knife cut on the buffers

to provide a tapered buffer that would cushion more on 

impact due to the reduced contact area. The first modified buffers had too much of a taper such that their 

warming would cause the weight assembly to bounce 

back into the catch. Two additional versions of the buffers were developed (100 mm and 110 mm) that had a

mild curvature to the bottom. These buffers were used 

for the remainder of the program.

FWD Temperature Issu

The LTPP program developed procedures for cold 

weather testing as part of the Seasonal Monitoring 

Program (see chapter 7). To keep the FWD units operating during the winter months, the LTPP regional 

support contractors added block heaters to keep the 

hydraulic fluid warm so the hydraulics would continue 

to operate. However, the AC current from the heaters 

created a spike in the peaks, which was noticed at the 

time of reference calibration. Procedures were then 

developed to ensure that the heaters were turned off at 

the test site and that testing would be terminated if 

temperatures dropped below 15 °C (5 °F

Pavement temperatures were initially measured 

using the Williamson infrared temperature sensors 

provided with the FWDs. They were problematic in

that they were intermittent in their operation. These 

infrared sensors were replaced with a Raytec infrared 

surface temperature probe. Regional calibration of the 

infrared sensors also determined an issue with the 

consistency of temperature output. After each calibration, the temperature coefficients changed, although 

slightly. It was decided that this change resulted in 

unreasonable differences. The procedures were modified in 2005 to allow the regions to perform calibration

checks, while temperature calibration changes would 

only be performed by the manufacturer.3

Figure C.3. One of the four original FWD van and trailer un
280 THE LONG-TE

Automated Temperature Datalogg

In 2008, the LTPP program developed the automated

temperature data logger (ATDL) and the software used

to determine surface and thermal gradient temperature 

measurements at FWD test locations (figure C.4 and

figureC.5).TheATDLprocesswas developed to replace

the manual method, which used a handheld temperature reader and probe to collect temperature data at the 

time of FWD data collection. The automated process

allows for collecting temperature data at the same time 

each FWD data pointis collected.The previous practice

for collecting this information was at 30-minute and

1-hour intervals. Although the setup was proven to be 

successful and some 16 units were assembled, this method was not implemented by the LTPP regional support 

contractors due to funding reductions that resulted in 

the suspension of FWD data collection at most LTPP

test sites (with the exception of some SPS projects).

FWD Quality Control Too

A60-millisecond (ms) window was used to capture the

loading and response history data. However, there 

were requests from researchers for 100-ms histories.

The LTPP program investigated this request at the 

time of the Dyna25 implementation and, based on the

added time required to store the histories, decided to 

continue with the 60-ms histories. The Dynatest program produced output files in the *.FWD format with

the history data embedded in the binary file. So, the 

LTPP program developed a field QC software tool—

FWDScan—to ensure that the FWD data met the minimum requirements (number of drops and repeatability) 

before sending the data to the office.4,5

The LTPP program began to migrate the FWD data

from U.S. customary units to the International System

of Units (SI) in 1999. The FWD setup was modified to

output in SI units.

Table C.1. Falling weight deflectometer equipment used in the LTPP prog

Year  Equipme

1988  Purchased 4 FWDs, equippe

Laptop computer—8000 series processor

  Dynates® DO v20 FWD fiel

Load cell

7 deflection sensors

8 weights, 55-lb (25-kg) each 

5-year maintenance contract requiring annual service at manufacturer

1988 GMC diesel vans and dual-axle trailers with enclosed bodies

1995  Refurbished 4 LTPP regional FWDs and purchased 

9000 series processor

5-year maintenance contract for annual service at LTPP regional office or manufactur

 Purchased 8 Ford diesel v

2000  Upgraded

9 deflection sensors 

  Dyna25 operating sys

  Database modified and output file formats created for read (*.F25) and historic (*.H25) 

  Training in Dyna25 for reg

 Replace FWD

2002  Refurbishe

2005  Upgrade FWD software 

Changed file format to Microsoft® Acces

2006  Disposed of  FWD in each region (transferred to other FHWA operations and the Nationa

for Asphalt Technology in Auburn,

2013–2014 Refurbished

 Purchased 4 diesel Chevrolet 2013 Express 3500 passenger v

 Upgrade FWD software to new CP-15 

(1)  The additional FWDs were needed to meet the demands of the Seasonal Monitoring Program and the addition f many SPS
appendix C: equipment, instrumentation, and software 281

PROFILING 

In 1989, SHRP purchased three DNC 690 Profilometers from K. J. Law to collect longitudinal profile data. 

The profilers used a Champion motor home chassis 

with Ford underpinning with dual rear wheels. These 

Profilometers used:

•	 Two incandescent sensors (centrally mounted and

shrouded).

•	 Two accelerometers.

•	 A distance measuring instrument.

•	 Photocell initiation.

A fourth Profilometer, mounted in a Ford E350 van

chassis, was obtained from FHWA and delivered to 

the LTPP North Central Regional Coordination Office

Contractor. This van had the same profiling system but 

was mounted in a smaller unit. The data collection and 

computing were handled by a PDP 1184 with disk drive

and tape backup. Profile elevations were sampled at 

1-inch (25-mm) intervals, averaged over 12 inches (305

mm), and reported at 6-inch (152-mm) intervals.

As the technology for profiling equipment improved, 

the LTPP program upgraded its units. New units were

subsequently purchased in 1996 and then again in 2002.

Starting in 1996 with the purchase of the K. J. Law 

T6600 Profilometers, SI units have been used for collecting and storing the profile data. In 2013, the LTPP

program took delivery of four new, state-of-the-art 

inertial profiling units manufactured by Ames Engineering that meet LTPP’s stringent acceptance criteria. 

The competitively procured profilers replaced LTPP 

profilers that were in service since 2002 and collectively logged more than 1.2 million miles (1.9 million km). 

Table C.2 lists the profiling equipment used in the LTPP 

program since delivery of the first profilers in 1989.

Data Filterin

Sample datawere collected and stored at1-inch (25-mm)

intervals with the conversion to the K. J. Law T6600

Profilometer. A 12-inch (305-mm) running average

was being applied to the 1-inch (25-mm) data output

at 6-inch (152-mm) intervals. In discussion with

K. J. Law, no filtering was to be applied to the 1-inch 

(25-mm) data. It was later discovered that a running

average was applied on the 1-inch (25-mm) data. Since

data were additionally being filtered by the LTPP 

regional support contractors, the profiles were being 

double-filtered. Researchers using these data should be 

aware that this was never rectified, and this double filtering is still present in the data in the LTPP database.

Capabilities and Acceptance Testing

of Latest Units

Capabilities

The latest LTPP profilers (purchased in 2013) were

specified and manufactured so the results from the testFigure C.4. Automated Temperature Datalogger 

temperature probes attached.

Figure C.5. Automated Temperature Datalogger s

in the field. The Datalogger is powered by a 12-volt S

battery. The solar panel charges the battery to sustain 

12 volts during data collection.
282 THE LONG-TE

ing regimen closely match legacy LTPP data collection 

parameters. The new units not only collect longitudinal 

profile data, but have added capabilities. Pavement macrotexture measurements are a new data collection element, and all of the data, including ambient and surface 

temperature, are now referenced with Global Positioning System coordinates. The cockpit of the vehicle has 

been designed to minimize driver distractions and provide ease of access to all controls and testing switches. 

As compared to the old LTPP profilers that used 2002-

era computer technology, the new system’s hardware 

requirements are minimized, resulting in a very low 

computer rack footprint. System software has been 

designed through a collaborative manufacturer/LTPP 

program process to be user-friendly and intuitive.

Acceptance Testing

The new LTPP profilers were procured and accepted 

for service using a very strict procedure. This procedure 

could be leveraged by other agencies that are procuring 

inertial profilers to check the ability of the equipment to 

collect consistent, accurate profile and macrotexture 

data. The acceptance procedure, conducted in February 

2013, consisted of the following checks:

Table C.2. Profiling equipment used in the LTPP pro

Year  Equipme

1989  Purchased 3 K. J. Law DNC 690 Profilo

  EC PDP 1184 computer processor with disk drive and

2 incandescent sensors, centrally mounted and shrouded

2 accelerometers

  Distance-measuring instrum

  Photocell initiat

  Elevations sampled at 1-in. (25-mm) intervals, averaged over 12 in. (305 mm), and reported 

 6-in. (152-mm) intervals

3 mounted in Champion motor home chassis with Ford underpinning, dual rear wheel

1 mounted in a Ford E350 van (DNC 690 Profilometer obtained fr

Video cameras added after delivery in some regions

1996  Purchased 4 K. J. Law T6600 Profilome

  IBM-compatible computer, integrated MS-DOS®/Windo

3 infrared sensors

 Mounted in Ford E350 extended 

Change from U.S. customary units t SI un

2002  Purchased 4 International Cybernetics Corporaton MDR 4086L3 P

3 laser/accelerometer sensors

Vertical and horizontal photocell

  Distance-measuring instrument integrated with speedometer pic

  Air temperature pr

 Mounted in Ford E350 

2003  Updated calibration oscillation integrated into process

2013  Purchased 4 Ames Engineering, Inc. Pro

3 laser/accelerometer sensors

2 texture sensors

Vertical and horizontal photocell

  Wheel-mounted quadrature optical encoder distance-measuring instrum

  Air temperature sen

  Pavement temperature sen

Global Positioning System (GPS) Wide Area Augmentation System (WAAS ) enable

 Mounted in Ford E150 
appendix C: equipment, instrumentation, and software 283

•	 Static Sensor Test: Researchers evaluated the precision and bias of the profile and texture height sensors in the static mode.

•	 Bounce Test: Researchers checked whether the accelerometers were cancelling out vehicle motion, 

and as an overall test on the integrity of the profiling 

system.

•	 Test on Distance Measuring Instrument (DMI): Researchers evaluated the precision and bias of the 

DMI.

•	 Profile Initiation Test: Researchers evaluated the

ability of the vertical and horizontal photocell to initiate data collection.

•	 Ability of Devices to Detect Profile Features: Researchers investigated the ability of the profiler to 

correctly detect profile features.

•	 Repeatability of Profile Data: Researchers analyzed

the ability of the devices to collect repeatable profile 

data.

•	 Repeatability of International Roughness Index

(IRI) Values: Researchers compared IRI values

computed from the profile data collected by the devices to determine the ability of the devices to obtain repeatable IRI values.

•	 Cross Correlation Analysis—IRI Repeatability of

Profile Data: Researchers performed this check to

evaluate the repeatability of IRI values along the 

section.

•	 Comparison of IRI Values with Reference Device

IRI: Researchers performed this check to compare 

the IRI values obtained by the test devices with IRI 

values computed from the data collected by a reference device.

•	 Cross Correlation Analysis—IRI Accuracy of Profile Data: Researchers performed this check to evaluate the accuracy of IRI values along the section 

compared to IRI from data collected by the reference device.

•	 Waveband Analysis of Profile Data: Researchers

performed this check to compare the spectral distribution of the profile data collected by the test devices with data collected by a reference device.

•	 Evaluation of Accuracy of Texture Laser in the Dynamic Mode: Researchers evaluated the accuracy of 

the texture lasers in the dynamic mode by utilizing 

the texture laser evaluation tool provided by the 

manufacturer.

•	 Evaluation of Data Collected by the Texture Lasers:

Researchers compared mean profile depth (MPD)

values computed from macrotexture data collected 

by texture lasers to MPD values obtained from a reference device.

To conduct the acceptance testing, several reference test sections were established near College 

Station, Texas. These sections consisted of two asphalt 

concrete, two Portland cement concrete, and one chip 

seal surface. The sections were selected to obtain a 

range of roughness and MPD values. The results were

analyzed and it was found that all four profilers met the

stated requirements. Following acceptance testing and 

analysis of the data, a week-long training exercise held 

in April 2013 for the LTPP regional support contractors paved the way for the LTPP program to incorporate the new devices into production mode for data 

collection.

SEASONAL MONITORIN

EQUI

The instrumentation and data collection equipment

used as part of the seasonal monitoring program (SMP) 

included:

•	 Tektronics 1502B cable testers.

•	 PS12LA power supply with charging regulators.

•	 Solar panels.

•	 CSI CR10 Dataloggers and multiplexers.

•	 TE525 and TE525MM tipping bucket rain gauges.

•	 CSI 107 air temperature probes.

•	 MRC 15 thermistor probes (soil gradient temperature probes) from Measurement Research Corporation (MRC).

•	 330-mm surface probe containing three thermistors.

•	 CRREL resistivity probe from the U.S. Army Corps

of Engineers’ Cold Regions Research and Engineering Laboratory (CRREL).

•	 FHWA time domain reflectometer (TDR) moisture

probes.

•	 Equipment cabinets and electronics.
284 THE LONG-TE

Equipment Challenge

Thermistor and Resistivity Probes

Thermocouple and resistivity probes were assembled 

in Albany, New York, at the State highway agency. The

agency had experience with the thermistor probes, and 

information on the resistivity probe was provided by 

CRREL.Thermistor probes were considered but decided against based on problems CRREL had using this

technology in Vermont and New Hampshire. At this

time, thermistor probes manufactured by MRC were in 

their infancy and little was known regarding their performance. A Troxler moisture probe was loaned from 

the vendor who was working with New York on the use

of this device. The LTPP program purchased a precision Hewlett-Packard multi-meter for the thermocouple and resistivity probe data collection and an Omega

channel selector to multiplex through the various thermocouples. An oscillator (developed from plans provided by CRREL) was assembled for resistivity probe

data collection. Some other methods were considered 

for frost/thaw determination, but time limitation eliminated these from the initial installation.

A function generator and multiplexer developed by 

FHWA’s Turner-Fairbank Highway Research Center 

replaced the initial manual 2-pt and 4-pt resistivity

multiplexers. The instrumentation for measuring air 

and pavement temperature and precipitation was connected to a CR10 Datalogger and mounted in a cabinet

at the site location.

The MRC surface thermistor probes that were contained in the 330-mm stainless steel probe had a high

failure rate. It was suspected this was due to the flexing of this probe under traffic loading (since they were 

placed in the surface layer in the wheelpath). Replacement probes, which contained three “piglet” style 

mini probes, were installed to replace the failed probes 

for Phase II SMP sites (figure C.6). Each probe was

placed independently within the surface layer at a

defined depth.6

Time Domain Reflectometer

TDR probes were used to obtain the moisture content

in unbound base and subgrade materials. The TDR

technique is based on the measurement of the travel 

time of an electromagnetic wave induced into a waveguide, in this application, a moisture probe. The 

apparent length is the length between the beginning 

and end points on the waveform, which correspond 

to the beginning and end of the metal tube portion 

of the moisture probe. This apparent length of 

the probe can be used to calculate the dielectric constant of the material surrounding the probe. The 

dielectric constant is an input to the calculation of 

moisture content.

The LTPP program evaluated TDR probes of various configurations (2-prong, 3-prong, short and long

probes, straight or curved probes, with or without baluns, etc.) using SonotubesTM with various soils and 

moisture levels to select the type of probe and using the 

Topp, Roth, and Paterson analytic procedures.

Problems were encountered with TDR activation

when using the CR10X Dataloggers. Support was

sought from CSI, but this issue was never resolved. It 

was never determined if the issue was a problem with 

the CR10X Datalogger or if the program was too complicated for the CR10X processor. CSI had indicated

that they had problems with the crystal in some of the 

CR10X Dataloggers, but the ones they delivered to

FHWA for the SMP Phase II program were not part of 

this group. The solution was to regularly check the 

Datalogger outputs and reload the program if the TDR

system went idle. This resulted in some of the early 

data sets being incomplete.

Figure C.6. “Piglet” style mini-probes installed

replace failed thermistor probes in PhaseII of 

Seasonal Monitoring Program
appendix C: equipment, instrumentation, and software 285

Equipment Improvements in SMP Ph

The continuous moisture and frost/thaw data collection in SMP Phase II was accomplished by integrating 

a Tektronics cable tester and an ERB20 resistivity multiplexer (manufactured by ABF, Inc.) with the existing

onsite instrumentation at select sites and in the mobile 

units. The ERB20 multiplexer, which replaced the

CRREL multiplexer, recorded the input voltage, which

allowed for the mathematical interpretation of the

automated resistivity data. 

In addition to the Tektronics cable tester and ABF

multiplexer, the Dataloggers were upgraded to the CSI

CR10X-2M along with CSI multiplexers, cabinet, and

remote telecommunication capabilities. The software, 

OnsPlus, incorporated an “Agency Machine” to initiate

the TDR system based on the level and intensity of

rainfall, and initiated the resistivity system based on 

below-freezing gradient temperatures from the MRC 

temperature probe. To extend the period between site 

visits, CSI SM-192 data storage modules were added. 

The SM-192 storage modules had 5-volt lithium batteries that provided reserve power to the memory chip to 

help prevent data loss.7

REFER

1. CR10 Operator’s Manual, Campbell Scientific 

Incorporation, November	1992.

2. Directive AWS-9,	“Remote	Collection of	AWS	Data,”	

Nov.	17,	1997.	Federal	Highway	Administration,	

McLean,	VA.	http://ltpp.org.phtemp.com/dirs/AWS/

AWS-09.pdf.

3. E. O.	Lukanen, R.	N.	Stubstad,	and	M.	L.	Clevenson.	

Study of LTPP Pavement Temperatures (FHWA-RD2-071). Federal Highway Administration, McLean, VA,	

March 2005.	http://www.fhwa.dot.gov/publications/

research/infrastructure/pavements/ltpp/02071/

02071.pdf.	

4. LTPP FWD Data Collection Software Manual, Version 

1.0.	Federal	Highway	Administration,	McLean,	VA,	

April	1,	2005.	Available	from	LTPP	Customer	Support	

Service Center (ltppinfo@dot.gov).

5. FWDCONVERT User’s Manual, Version 1.0. Federal 

Highway	Administration,	McLean,	VA,	April	1,	2005.	

Available from LTPP Customer Support Service Center

(ltppinfo@dot.gov).

6. Pilot Installation of TP101-PSP Pavement Temperature 

Sensor at LTPP Site 360801, Hamlin,	NY,	October	11,	

2001.	Available	from	LTPP	Customer	Support	Service	

Center (ltppinfo@dot.gov).

7. Directive SM-36,	“Upgrade	of CR10	Procedure	

Manager	Software	to	Version	5.02,”	Apr.	10,	2000.	

Federal	Highway	Administration,	McLean,	VA.	http://

ltpp.org.phtemp.com/dirs/SMP/SM-36.pdf.	
©American Concrete Pavement Association, www.acpa.org
Index

Page numbers followed by b, f, or t refer to sidebar text, 

figures, or tables, respectively.

A

AASHO. See American Association of State Highway Officials.

AASHTO. See American Association of State Highway and 

Transportation Officials

AASHTOWare Pavement ME Design, 39, 208, 243

Abbott, Allan L., 259, 260, 262, 265

Abukhater, Basel, 27f, 30f

Accelerated Pavement Testing, 6, 63–64

Administration and management, LTPP

centralized structure of, 231, 232

challenges, 10, 30

communication and coordination practices in, 26–30, 

239–240

of data collection and storage, 19–20, 23, 24, 133, 232

under FHWA, 12, 19–26, 21f, 22f, 231, 232

highway agency staff, 234

key milestones in, 12b

lessons learned from LTPP program, 231–234

norms of operation, 232, 233f

in origins of LTPP program, 7

program performance reviews, 234–239

regional offices, 12, 13f

role of peer review groups in, 17–18, 25–26

under SHRP, 12–18, 14f, 40, 231, 232, 257

staff stability, 232

in transitional period (1991 to 1992), 12, 18–19, 19f, 20b, 32b

Advisory Committee. See Pavement Performance Advisory 

Committee

Albright, David, 259, 261, 265

Almond, Roger, 259, 262

AMEC Environment & Infrastructure, Inc., 270, 274, 275

American Association of State Highway Officials (AASHO), 

2, 102, 157, 159

American Association of State Highway and Transportation 

Officials (AASHTO), 25, 27, 121, 183, 218b, 234

activities of, 37

design guide, 250

design procedures, 243

equipment calibration standards, 89, 217

in establishment of Strategic Transportation Research 

Study, 4

financial support to LTPP program from, 37, 46, 53

as LTPP partner, 35, 37, 38f

in LTPP product development, 205, 211, 212, 235

in LTPP program performance reviews, 235, 236

Materials Reference Laboratory, 92

materials testing standards, 126, 177

in origins of LTPP program, 3, 6, 37, 257

pavement profiler standards, 212

INDEX    287
pavement smoothness specification, 213

Task Force on Strategic Highway Research Program, 6

in transition of LTPP program from SHRP, 18

American Association of State Highway Officials, 2, 102, 

157, 159

American Automobile Association, 41

American Concrete Pavement Association, 41

American Society of Civil Engineers, 41, 204

American Society of Testing and Materials, 99, 104, 218b, 220

American Trucking Association, 41

America’s Highways, Accelerating the Search for Innovation, 4

Ames Engineering, Inc., 100, 100f, 101f, 272, 281

Ancillary Information Management System

current content of, 132, 147t, 245b

Data Entry Portal, 139–141

data storage, 136, 147–148

location of, 141

objective of, 147, 245b

online access, 154

origins and evolution of, 134

Anderson, Paul, 260

Anderson, Virgil, 64f

Andrei, Radu, 19f

Angelou, Maya, 230b

Annual meetings, LTPP program, 27

Applied Research Associates, Inc., 272, 273, 275

ARAN survey vehicle, 7

Ardani, Ahmad, 192f, 264

Arellano, Janice, 260, 262

Arizona Department of Transportation, 72b, 200, 214

Armaghani, Jamshid, 264

Asphalt

SHRP research program, 5b, 12–13, 32

thickness measurement, 83–84

Asphalt concrete pavement

General Pavement Studies of, 66–68, 74t

Specific Pavement Studies of, 71–72, 74t

Asphalt Institute, The, 41

Asphalt Recycling and Reclaiming Association, 41

Asphalt Research Consortium, 88

Assaf, Gabriel, 266

Association of Asphalt Paving Technologists, 41

ASTM International, 99, 104, 218b, 220

Augustin, Harold, 266

Austin Research Engineers, Inc., 270

Automated vehicle classification, 174

Automated weather stations, 80–82, 80f, 81f, 144, 167, 172, 

173, 177, 277–278

Average annual daily traffic, 106–107

Ayers, Michael E., 192f, 260, 262

B

Baker, Cindy, 19f

Baker, Thomas E., 192f, 262, 264

Baladi, Gil, 192f, 266

Baltimore FHWA Resource Center, 96

Barksdale, Richard D., 259

Barnhart, Ray A., 259

Barrett, Marsha, 19f

Basin tests, 89

Bellinger, William, 19f, 30f, 255b, 262

Benkelman Beam, 7

Benson, Paul E., 260, 263, 266

Berentson, Duane, 258, 259

Berge, Calvin, 19f, 270

Berge, Richard L., 261

Bertrand, Carl, 260, 262

Bianchini, Allesandra, 266

Binder selection, 200, 208

Blaschke, Byron, 259

Block, Edgardo, 27f

“Blue Book.” See Strategic Transportation Research Study

Bonaquist, Ramon, 264

Braun Engineering Testing, 273

Braun Pavement Technology, 270, 271

Brent Rauhut Engineering, Inc., 270, 271, 275

Briggs, Robert C., 260

Broad Agency Announcement, 191, 199, 275

Brosseau, Kathy, 19f

Brown, James L., 259, 260

“Brown Book.” See Strategic Highway Research Program 

Research Plans, Final Report (1986)

Browser program, 135, 136f

Buchbinder, Brenda, 19f

Bush, Albert J., III, 259, 260

C

Cable, James K., 260, 262, 264, 265

California LTPP National Meeting (1996), 27, 235–236

Calvin, Lyle, 260

Campaign for Program Improvement, 236–237

Campbell Scientific, Inc., 118, 278, 284, 285

Canada, in origins of LTPP program, 3

Canadian Climate Center, 82

Canadian Strategic Highway Research Program, 35, 37–39, 

46–47, 257–258

Carmer, Samuel G., 260

Carr, Bill, 19f

Carver, Gary S., 262

Cebon, David, 122f, 265

288    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Cement

SHRP research program, 5b, 13

testing responsibilities, 17

Center for Experimental Research and Studies of Building 

and Construction (France), 7

Central Traffic Database, 148, 157

Chandran, Ravi, 27f

Chatti, Karim, 192f, 266

Chen-Northern, 273

Chloride corrosion, 5b

Christison, Tom, 259, 261

Churilla, Charles J., 33f, 192f, 255b, 259, 262

Cimini, Gabe, 30f

Clark, Tommy, 30f 

Clevenger, Robert L., 259

Climate

data collection from weather stations, 80–83, 80f, 81f, 82f

data collection quality control, 175

data storage, 144, 150, 150f

LTPP data collection program, 1, 77, 212

SHRP research objectives, 5b

See also Frost/thaw effects; Seasonal Monitoring Program; 

Weather stations

Cochran, George, 264

Cold Regions Research and Engineering Laboratory, 283, 284

Cole, Lawrence W., 260, 262, 263

Collier, Donald W., 258

Collins, Ronald, 259, 262

Colorado Department of Transportation, 200

Colorado Mid-Course Assessment Meeting (1990), 27, 234–235

Communication and coordination

accomplishments of LTPP program, 26

feedback mechanisms, 182–183, 215–216

with international community, 42, 252

lessons learned from LTPP program experience, 239–240

LTPP Norms of, 232, 233f

mechanisms for, 27–30

Webinars, 28–29, 29b, 216

See also Data dissemination

Computed parameters, 83, 145–147, 198

Concrete and Aggregates Association, 41

Concrete bridge component protection, 5b, 13

Concrete Pavement Evaluation System, 4

Connecticut Department of Transportation, 27f

Connor, Billy G., 260

Contract services

communication among LTPP program partners, 27, 28, 

29–30

for data analysis, 275

for data collection equipment, 271–272

for data storage and dissemination, 274

under FHWA, 20–25, 22f

key milestones in LTPP management, 12b

for materials collection and testing, 89, 273–274

onsite support, 271

for pavement-related data collection, 78–79, 89, 93–94

peer review, 269–270

in pre-implementation of LTPP program, 5–6, 13

scope of, 269

under SHRP, 17

for technical support, 270

for traffic data collection, 272–273

in transition period, 18

See also Regional contracts; Regional support contractors; 

Technical assistance contractor; Technical support 

services contractor

Copeland, Charles, 266

Corley-Lay, Judith, 192f, 260, 262, 263, 264, 265

Cornell University, 92, 272

Cox, Brian, 19f, 266

Crack sealing and filling, 191, 209, 210

Crumb Rubber Modifier Project, 88

Cumberledge, Gaylord, 260, 263

Cumberledge, Gramling and Hunt, 93, 272

Cunagin, Wiley, 265

Curl and warp, 214

Curvimeter, 7

D

Dabberdt, Walter, 261

Dahlin, Curtis, 265

Daleiden, Jerome, 30f, 266

Dalrymple, Harold, 260

Darter, Michael, 266

Data analysis

accomplishments of LTPP program, 189

contracts, 275

Expert Task Group, 263

under FHWA Broad Agency Announcement, 191

future plans for, 250–251

goals of Program Improvement Campaign, 236–237

highway agency studies, 199–203

International Data Analysis Contest, 204, 204f

key findings from, 216

key milestones of LTPP program, 189–190b

Mechanistic-Empirical Pavement Design Guide, 203

objectives of, 189–190, 216–217, 244–245, 250

in product development, 204, 231

to reduce variability in test results, 218b

under SHRP, 190–191

INDEX    289
strategic plan, 191–199, 193f, 194f, 195–197f, 199t, 250

tablecloth, 194

Transportation Research Board Data Analysis 

WorkGroup, 28, 203, 250, 257, 266

Data Analysis/Operations Feedback Report, 176, 180, 182, 183f

Database, LTPP

accomplishments of, 131, 159, 183–184, 189, 217, 243

backup procedures, 158, 158t

climate data, 150, 150f

computed parameters in, 145–147

current content of, 132–133, 159, 245b

custom extractions from, 153

data dissemination rules and procedures, 134–135, 134f, 

136–137, 136f

data dissemination tools, 215

Data Entry Portal, 139–141

data sources for, 133

effects of budget cuts on development of, 56

estimated spending on, 47–48

evolution of technology for, 240

evolution under FHWA, 135–141

evolution under SHRP, 133–135, 134f

Expert Task Group on development and operations of, 263

falling weight deflectometer data, 148–149, 148f

future opportunities for use of, 252–253

goals of Program Improvement Campaign, 236–237

growth in volume of, 148–151

higher order data checks, 178–180

information management system. See Information 

Management System

international contest to promote use of, 41

key milestones in development of, 132b

Level E data, 24, 134–135, 136, 137, 148, 175–176

longitudinal profile data, 149, 149f

major components, 132. See also specific component

management responsibilities, 19–20, 23, 24, 133, 176

modules, 79, 79t. See also specific module

objectives, 7–8, 54–55, 131, 215, 244

ongoing and projected improvements to, 245b, 246–247

as online system, 139–141

pavement distress data in, 149–150, 150f

pavement performance data in, 144–147

pilot study, 3–4, 5

process flow, 136f, 138f, 140f

quality assurance audits, 177–178

quality control checks and reviews, 175–176

recent evolution of, 139–141

records management, 134

security, 157–158, 159, 246

Software Performance Report, 144

Standard Data Release, 137, 153

test section construction number in, 136

transverse profile data, 150, 150f

user support, 247

See also Data collection; Data dissemination

Data collection

accomplishments of LTPP program in, 108, 114, 219, 

220, 243

attention to ambient conditions in, 170–171

beginnings of LTPP, 89b

categories, 77, 79f

challenges, 76, 108

database modules, 79, 79t. See also specific module

data elements and types in, 79

on dynamic load response, 83

effects of budget cuts on, 52–53, 55

equipment, 168t, 217–218

equipment contracts, 271–272

estimated spending on, 47–48

federal programs and initiatives benefiting from LTPP, 

219–220, 252

forensic studies, 127–128

forms, 165

goals of Program Improvement Campaign, 236–237

ground penetration radar measurements, 83–84

inventory of experimental sections, 84–85

key milestones in, 78f

library resources, 156–157

in Long-Term Pavement Monitoring Study, 4

LTPP program objectives for, 7–8, 11, 77–78, 80, 244

in LTPP under SHRP, 15–16

on maintenance and rehabilitation, 85–87

materials, 87–89

participants in, 78–79

pavement performance, 247–250

practices before LTPP, 3, 4

product development and, 235

qualifications of personnel for, 167–168

regional approach, 12

role of regional coordination office contractors in, 16

role of regional support contractors in, 23–24, 133, 135, 170

role of technical assistance contractors in, 20–23

special programs and data sets, 79, 115, 116b. See also

specific program or data set

standards and guidelines, 164–165, 166t

at weather stations, 80–83, 80f, 81f, 82f

See also Database, LTPP; Data dissemination; 

Monitoring data module; Quality assurance/quality 

control; Traffic data collection

Data Dictionary, 215

290    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Data dissemination

contracts, 274

cost of access, 153

Federal policy and guidelines for, 151–152

key milestones in LTPP program, 132b

from LTPP database, 136–137

LTPP library access, 156–157

LTPP program communication and coordination practices, 

26–30

LTPP program objectives for, 1, 151

major releases of LTPP data, 152t, 153

online access, 139–141, 154–155, 157, 215

quality control policy in, 153, 176

role of Customer Support Service Center, 155–156

under SHRP, 134–135, 134f, 136f

Standard Data Release, 137, 153, 215, 251

tools for, 154–155, 215

Datalogger, CSI, 118, 278, 283, 284

Data Operations Analysis Feedback Report, 135

DataPave, 154, 215, 274

Data Quality Act, 151, 152, 153f

Data studies, 178, 179–180

Data User’s Guide, 23

Dawood, Danny, 192f, 264

Decker, Dale S., 262

Deen, Thomas B., 259

Deflection equipment and testing

calibration standards, 89

data storage, 145

equipment comparison studies, 6–7

evolution of, in LTPP program, 89

Expert Task Group, 260

management responsibilities, 21, 24

objectives of LTPP program, 89

See also Falling weight deflectometer

DeFrain, Leo, 260

de Groot, Morris, 260

Dell’Acqua, Gianluca, 266

Dempsey, Barry J., 261

Department of Transportation, U.S., 151–152, 219

Design, pavement

contributions of LTPP program to, 243

LTPP product development for, 207–210

practices prior to LTPP, 2

research goals of LTPP, 1, 7

Dietrich, Bruce, 264

Dipstick® measurements, 99, 100–101, 101f, 104–105

Distress Identification Guides, 210, 211f

Distress Identification Manual, 94, 96, 210, 217, 251, 260

Distress Identification Manual for the Long-Term Pavement 

Performance Program, 165, 166

Distress surveys

accreditation of raters for, 167

comparison of technologies for, 6–7

consolidation studies of data from, 180

data analysis studies, 200

data collection equipment contracts, 271–272

data collection manual, 210

data storage, 145, 149–150, 150f, 246

Expert Task Group on Automated Distress Identification, 

260, 262–263

Film Motion Analyzer, 95, 95f

management responsibilities, 16, 20–21

manual, 95–97, 217

maps, 94, 94f

office reviews of, 97–98

photographic, 17, 93–95, 271–272

purpose of, 93

quality control and assurance checks in, 95, 172–173, 177

time-series review of, 179

variability studies of data from, 180, 199

Distress Viewer and Analysis software, 98, 98f, 179, 179f

Distress Viewer and Analyzer, 95

Donahue, John, 192f

Doré, Guy, 259, 263, 264

Dougan, Charles E., 259, 262

Drainage, 98, 145

Dumont, A. G., 266

Dynaflect, 7

Dynamic cone penetrometer, 88

Dynamic load response, 83, 144

Dynamic Load Response Program, 51

Dynamic modulus, 198, 208–209

Dynatest, 7, 91, 92, 93, 272, 278, 279

E

EBA Engineering, Inc., 271

ECOMPEX, 271

Edwards, William, 260

Effects of Multiple Freeze Cycles and Deep Frost 

Penetration on Pavement Performance, 214

Eijberson, Marc, 263

Elkins, Gary, 30f, 192f

El-Korchi, Tahar, 192f, 260, 263, 265

Engineering & Software Consultants, Inc., 271

Environmental data

Expert Task Group, 261

LTPP products for collection of, 214

See also Climate; Seasonal Monitoring Program; 

INDEX    291
Weather stations

Environment Canada, 175

Epps, Jon, 192f, 260, 263, 264

Equipment

contracts, 271–272

distress survey, 6–7

Expert Task Group, 260

management responsibilities, 17, 24

needs of LTPP program, 277

quality control and quality assurance program, 168–170

in Seasonal Monitoring Program, 283–285

traffic data collection, 107–108

See also Automated weather stations; Falling weight 

deflectometer(s); Profiling equipment

ERES Consultants, 271, 275

Esch, David, 19f

Evaluation of Pavement Deflection Measuring Equipment, 7

Expansive soils, 116

Experiments, pavement

accomplishments of LTPP program in, 75

benefits of ongoing data collection, 248t

current state of original, 248

data storage, 145

development of, in LTPP program, 63–64

Expert Task Group on design and analysis, 260

future of, 249–250

key milestones in design of, 64b

objectives of, 1, 63

significance of, in LTPP program, 63

See also General Pavement Studies; Test sections; 

Test sites; Specific Pavement Studies

Expert Task Group(s)

on Automated Distress Identification, 262–263

on Database Development and Operations, 263

on Deflection Testing and Backcalculation, 260

on Distress and Profile Data Collection and Analysis, 

262–263

on environmental data, 261

on Equipment Evaluation, 260

on Experimental Design and Analysis, 260

on Falling Weight Deflectometer Data Collection and 

Analysis, 264

on LTPP Automated Distress Identification, 260

on LTPP Data Analysis, 191–192, 263

on Materials Data Collection and Analysis, 264

membership and scope of, 17–18, 25–26, 257–258

on Product Development and Delivery, 264

reduction in number of, 239

role of, 17, 165

on Special Activities, 36f, 265

on State Usage of LTPP Data, 264

technical areas supported by, 258t

on Traffic Data Collection and Analysis, 237, 264–265, 265

on traffic data collection and analysis, 261

on weigh-in-motion technology, 261

F

Falling weight deflectometer(s), 90f

automated temperature data logger, 280, 281f

buffers, 279

calibration centers, 17, 92, 272

calibration program, 169, 211

calibration schedule, 92–93

calibration standards, 217

database, 148–149, 148f

data collection procedures and equipment, 16, 90–91

data studies, 180

equipment comparison, 6–7

equipment contracts, 272

equipment maintenance, 91, 279

equipment purchases, 278, 280t

error-checking, 171–172

Expert Task Group on data collection and analysis, 264

manuals, 93

meetings, 93

purpose of, 89

quality assurance audits of test data, 177

quality control checks, 91, 173, 280

temperature effects, 116, 279

User Group, 28

Federal-Aid Highway Program, 4, 48, 56

Federal Highway Administration (FHWA), 27, 35, 96

in data analysis program, 191, 192, 194, 198, 199

in development of LTPP research program, 70, 80

financial support for LTPP from, 45–46

Information Quality Initiative, 152

in LTPP management, 11, 12, 17, 19–26, 21f, 22f, 29, 41, 231, 

232, 257

LTPP program performance assessments, 236–238

materials research in, 63

moisture probe developed by, 118

Office of Highway Planning, 4

Office of Infrastructure Research and Development, 19

Office of Pavement Technology, 205

Office of Research and Development, 4

in origins of Long-Term Pavement Monitoring Study, 3, 4, 5

in origins of LTPP, 3, 6, 8, 258

Pavement Condition Monitoring Methods and 

292    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Equipment Study, 6–7

publication standards, 181

staff loaned to SHRP and LTPP, 15

transition of LTPP from SHRP to, 5–6, 18–19, 269–270

Ferne, Brian Walter, 266

Ferragut, Ted R., 259, 262

FHWA. See Federal Highway Administration

Financing

for data analysis, 194, 198, 198t

for data dissemination, 153

distribution of LTPP spending, 47–48

estimated costs of infrastructure replacement and 

rehabilitation, 2

Federal-Aid Highway Program, 56

federal investment in LTPP to date, 45, 46t, 58

fluctuations in LTPP funding levels, 12, 48–56, 48f, 58, 

231–232

for forensic studies, 127

highway agency contributions to, 234

highway spending, 2

initial LTPP price tag, 2

lessons learned from LTPP program, 231–232

LTPP program’s return on investment, 1–2, 44, 219–220

for product development, 205

SHRP, 4, 11, 46, 48

sources of LTPP’s, 45–47, 47t, 48f

of Specific Pavement Studies, 73

support from AASHTO to LTPP program, 37, 46, 53

Traffic Data Collection Pooled-Fund Study, 122, 238

Fletcher, Leland, 259

Flexible pavements, 203

Flom, Ewa, 264

Folsom, Ralph, 265

Forensic studies, 127–128, 249, 252

Forsyth, Raymond A., 259

Framework for LTPP Forensic Investigations, 127

Francois, Francis B., 258, 259

Franta, Daniel, 204f

Freeman, Donald H., 262

Friction studies, 89, 99, 145

Frost/thaw effects, 116, 117, 120, 121, 214, 285

Fugro Consultants, 271

Fugro Roadware, 271, 275

Fulmer, McRaney, 259

Future challenges and opportunities

collecting pavement performance data, 247–250

database maintenance and improvement, 245–247

development of pavement performance standards and 

measures, 243

forensic studies, 249

LTPP objectives, 244–245

FWDCheck, 91

FWDScan, 91

G

Gardner, Mark, 30f, 192f

Gendell, Dave, 259

General Pavement Studies, 6, 64–65

benefits of ongoing data collection, 248t

current state of original experiments, 248

data collection in, 79

design criteria, 65b

evolution of, 66–68, 67t

experiments, 8, 8t, 65–66, 74t

inventory data, 84–85

lack of historical data for early, 230

limitations of, 65

management structure and responsibilities for, 15, 49

materials sampling in, 87–89

purpose of, 63, 64

research matrices, 65, 66f

sampling template, 68, 69f

Specific Pavement Studies and, 69

test sections, 65b, 68–69, 74f

traffic data, 106

German, John, 64f

GERPHO survey vehicle, 7

Gillmann, Ralph, 265

Global positioning technology, 85

Goode, Mark G., 259

Goodman, Steve, 263

Gramling, Wade, 259

Green, Ed, 265

Green, Roger, 260, 263

Griffith, John, 261

Groeger, Jonathan, 30f, 192f

Ground penetrating radar, 17, 83–84, 145

Guide for Mechanistic-Empirical Design of New and 

Rehabilitated Pavement Structures, 189

Guide for the Design of New and Rehabilitated Pavement 

Structures, 203, 207

Guide for the Design of Pavement Structures, 250

Guide to LTPP Profiler Comparison Resource, 101

Guide to LTPP Traffic Data Collection and Processing,

107–108

Guinn, Bob, 260

Gulden, Wouter, 260, 263

Gupta, Kris, 19f, 255b, 265

INDEX    293
H

Haas, Ralph, 36f, 64f, 192f, 262

Hadley, William O., 266

Hager, Guy, 19f

Hajek, Jerry, 192f, 265

Hall, James P., 260

Hallin, John P., 259, 260, 264

Hamrick, John, 265

Hanna, Amir, 19f, 192f, 262, 266

Hansen, Kent, 260, 263

Harley, Thomas, 27f

Harm, Eric, 263

Harrigan, Ed, 19f

Harriott, Don, 19f

Hawks, Neil, 19f, 20f, 32b, 192f, 255b, 259, 262, 266

Heanue, Kevin, 259

Hegmon, Rudolph R., 260

Heitzman, Mike, 192f, 264, 265

Henion, Lloyd, 261

Hensing, David J., 259

Hibbs, John, 19f

Hicks, R. G., 259

Higher order data checks, 178–180

Highway Economics Requirement System, 219

Highway Performance Monitoring System, 219, 246, 252

Highway Research and Development Program, 56, 57b

Hill, Loren, 260, 262

Hill, Sonya, 260

Hoffman, Gary, 26f, 262

Holman, Frank K., Jr., 260

Horosko, Andrew, 265

Hosang, John R., 262

Hot-mix asphalt pavements, 127, 128, 170–171, 191, 246

Houska, Ronald W., 259

Hryhorczuk, Boris, 259

Hu, Pat, 26f, 122f, 262, 265

Hudson, W. Ronald, 259

Hunter, Robert N., 258, 259

Hutchinson, Bruce, 265

I

ICC Profiler, 100, 100f

iENGINEERING Corporation, 274

Improved Methods and Equipment to Conduct Pavement 

Distress Surveys, 7

Indirect tensile strength, 151f

Industry groups, 35, 41

Inertial profiler, 99–101

InfoPave Website, 105, 148, 154–155, 155f, 156f, 215, 274

Information Management System, 22, 23, 30, 41

backup procedures, 158, 158t

components, 132

contracts, 17, 20, 274

development of, 133–141

hardware and software, 141–144, 142t, 143f

Infrared scanning, 247

Ingberg, Dick, 19f, 270

Innovative Materials Development and Testing, 191

Innovative Pavement Research and Deployment Program, 46

Interim Guide for Design of Pavement Structures, 40

Intermodal Surface Transportation Efficiency Act, 18, 19, 45, 

46, 50–51, 50b, 50t

International Cybernetics Corporation, 272

International Data Analysis Contest, 204, 204f

International Grooving and Grinding Association, 41

International Road Dynamics, Inc., 273

International Road Federation, 42

International Roughness Index, 100, 172

Inventory data, 84–85, 105–106, 145

Irick, Paul E., 259

Irwin, Lynne, 192f, 239b, 263

Iwasaki, Randy, 26f, 262

J

Jackson, Newt, 192f, 259, 260

Jackson-Grove, Amy, 27f

Jämsä, Heikki, 263, 266

Jarema, Frank, 265

Jaskaniec, Mike, 259

Jessberger, Steve, 192f, 265

Jiang, Jane, 30f, 192f, 255b, 265

Johnson, Andy, 192f, 263, 264, 265

Johnson, Cindy, 19f

Jones, Harry, 19f

Jordan, P. G., 260

Jorgenrud, W. H., 259

Joubert, Robert, 259

K

K. J. Law, 272, 281

Kamiya, Keizo, 19f, 266

Kansas Department of Transportation, 200

Kashuba, Ed, 265

Kass, Said, 264

Kavanagh, Leonnie, 263

Kazakov, Alex, 260

Kelley, Bob, 19f

Kenis, William J., 260

294    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Kent, Perry, 261

Kerali, Henry G. R., 262, 263, 266

Kilareski, Walter P., 260

Kim, Richard, 264

Kissane, Colleen, 260, 262

Klemunes, John, 255b

Knutson, Marlin J., 259

Kramer, James, 122f, 265

Kuab FWD, 7

Kulash, Damian, 19f

L

Laboratory Materials Testing and Handling Guide, 218b

Laboratory Testing Guidelines, 87

Lamm, Lester P., 259

Lamond, Joe, 19f

Larsen, Donald, 260, 262

Larsen, Hans Jorgen Ertman, 259

Larson, Charles, 260, 262

Larson, Roger M., 260

Larson, Thomas D., 258, 259

Laser Road Surface Tester, 7

La Torre, Francesca, 266

LAW Engineering, 270, 273, 274

Lawrence, Anthony, 266

Lawson, Catherine T., 36f, 265

Laylor, Marty, 19f

Leahy, Rita, 19f, 259

Leben, Bojan, 266

LeClerc, Roger, 259

Lee, Kang-Won Wayne, 266

LENDIS Corporation, 271

Lenz, Russel W., 262

Leonardo, Joseph M., 262

Lessons Learned and Recommendations for Future 

Analyses, 190

Lill, Richard A., 259, 260

Little, Vondell, 19f

Litzka, Johann, 266

Load transfer tests, 89

Loaned staff program, 13, 14f, 15, 15b, 20, 39, 42, 46

Lofroos, William N., 259, 265

Longitudinal profile data, 99–102, 145, 149, 149f

Long-Term Bridge Performance program, 219, 252

Long-Term Pavement Monitoring Study, 5, 8

Data Collection Guide, 4

objectives of, 3–4

origins of, 3

Long-Term Pavement Monitoring Workshop, 4, 6

Long-Term Pavement Performance Committee, 25–26, 

258, 258t

current activities and organization, 261–262

Expert Task Groups, 261–265

purpose, 261

Long-Term Pavement Performance Data Analysis Program, 

244

Long-Term Pavement Performance Maintenance & 

Rehabilitation Data Collection Guide, 86

Long-Term Pavement Performance Manual for Profile 

Measurements and Processing, 165

Long-Term Pavement Performance program

costs, 2

Customer Support Service Center, 124, 133, 155–156, 181, 

215–216

distribution of spending, 47–48

documentation of activities of, 240, 245b

federal investment in, to date, 45, 46t

funding sources, 45–47, 47t, 48f

future challenges and opportunities, 243–253

goals and objectives, 1, 7–8, 229

key findings from, 216

legislative authorization, 19, 45, 46t, 47t, 48–56

lessons learned from, 229–241

management. See Administration and management, LTPP

origins and evolution. See Origins and evolution of LTPP

partnerships. See Partnerships, LTPP

periodic performance assessments, 234–239

products. See Products, LTPP

return on investment in, 1–2, 44

significance of, 1

sources of success, 11, 26, 29, 35, 75

Long-Term Pavement Performance Project Laboratory 

Materials Testing and Handling Guide, 87

López, Aramis, 19f, 26f, 27f, 30f, 33f, 192f, 255b, 262, 265

LTPPBind, 200, 208

LTPP Data Analysis: Influence of Design and Construction 

Features on the Response and Performance of New 

Flexible and Rigid Pavements, 83

LTPP Guide to Asphalt Temperature Prediction and 

Correction, 191

LTPP Information Management System User Guide, 145

LTPP Manual for Falling Weight Deflectometer 

Measurements, 165

LTPP Manual for Profile Measurements and Processing, 165

LTPP Optimal Weigh-in-Motion Locator software, 213–214

LTPP Pavement Analysis Forum (2010), 27, 40

LTPP Pavement Loading User Guide, 214

LTPPStar, 209

INDEX    295
LTPP Traffic Analysis Software, 124, 125f, 174

Lytton, Bob, 192f, 266

M

MacCreary, William J., 259, 262

MACTEC Engineering and Consulting, Inc., 270, 273, 274

Magnetic tomography, 247

Mahoney, Joe P., 260

Maina, James William, 266

Maintenance and rehabilitation of pavements

data analysis, 202

data collection, 85–87

data storage, 145

General Pavement Studies of, 66–68, 69

LTPP products for, 209–210

management responsibilities, 16

planned studies, 250

practices prior to LTPP, 3

research goals of LTPP, 1, 7

research objectives of SHRP, 5b

SHRP data analysis projects for, 191

Specific Pavement Studies of, 73, 74

Manual for Profile Measurement: Operational Field 

Guidelines, 102

Marcuson, Joel, 259

Markow, Michael, 260

Mason, Robert L., 260, 266

Materials

contracts for collection and testing of, 273–274

data storage, 150–151, 151f

Expert Task Group on data collection and analysis, 264

in LTPP data collection program, 77

research goals of LTPP, 1, 7

sample and data collection, 87–89

sampling and testing, 24

SHRP research objectives, 5b

testing contracts, 24

Materials Action Plan, 30, 78, 125–127, 238

accomplishments of, 128

laboratories, 126

origins of, 125

procedures, 125–126

purpose of, 115, 125

Materials Reference Laboratory, 92, 211, 272

Materials Reference Library, 17, 18–19, 88, 95, 128, 245b, 246, 

252, 273–274

Materials Sampling and Testing Guidelines, 87

Mathis, Amelia, 192f

Maupin, Bill, 263

McCall, Billy M., 261, 265

McClure, Karen, 263

McCullagh, Frank R., 259

McDaniel, Mark, 264

McDaniel, Rebecca, 36f, 192f, 264, 265

McDonnell, Anne-Marie, 27f, 122f, 265

McDonnell, Jim, 262

McGhee, Kenneth H., 259, 260

McNeil, Lisa, 19f

McQuiston, Robert, 260

Measurement Research Corporation, 283

Mechanistic-Empirical Pavement Design Guide, 79, 124, 194, 

202, 203, 219, 243, 246, 250

Meetings, 27–30

budget cuts and, 239

falling weight deflectometer operator, 93

LTPP program performance assessments, 234–239

Pavement Analysis Forum, 192–194, 192f

Transportation Research Board Data Analysis Work 

Group, 203

Mendez, Victor M., 255b, 262

Mergenmeier, Andy, 192f

Merwe Steyn, Wynand Jacobus van der, 266

Meyer, Frank, 27f, 30f, 192f

Michael, Harold L., 258

Michigan Transportation Research Institute, 102

Mikulin, Robert L., 260

Miller, Samuel, 264

Minnesota Department of Transportation, 200–202

MnROAD, 100, 101, 170f, 201–203

MOBILFIELD software, 120

Modern Era-Retrospective Analysis for Research and 

Applications, 82, 212, 219–220

Mohammad, Louay N., 266

Monismith, Carl, 192f, 260, 262

Monitoring data module, 145

data categories, 89

deflection studies, 89–93

distress surveys, 93–98

drainage studies, 98

friction tests, 99

longitudinal profile data, 99–102

origins and evolution of, 89

rutting data, 102

transverse profile data, 103–105

Monroney, Harold W., 259

Moore, Ray, 192f, 259, 260, 262, 263

Moravec, Michael, 255b, 264

Moreland, Thomas D., 258

296    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Morgan, Richard D., 259, 262

Moving Ahead for Progress in the 21st Century, 45, 56, 57b, 

57t, 243

Moyer, William R., 259

Murphy, Daniel T., 258

Murphy, Michael, 263

Murray, Carol A., 262

Myre, Jostein, 266

N

Narsiah, Juliet, 19f

National Academy of Sciences, 11, 17

National Aeronautics and Space Administration, 82, 147, 212

National Asphalt Pavement Association, 41

National Center for Asphalt Technology, 88

National Climatic Data Center, 82, 175

National Cooperative Highway Research Program, 37, 194, 

198t, 258

National Research Council, 11, 12, 17, 25, 30, 35, 40, 257, 

269–270

National Stone, Sand, and Gravel Association, 41

Nelson, Richard J., 260

Neukam, Tom, 261

Newcomb, David E., 259, 262, 264

New Jersey Department of Transportation, 202

New York State Department of Transportation, 117

Nichols, Andrew, 122f, 265

Nichols, Brooks, 259

Nichols, Frank P., Jr., 259

Nichols Consulting Engineers, Chtd., 270, 271, 274

Nieves, Antonio, 255b, 264

Nikolaides, Athanassios Fotios, 266

North American Travel Monitoring Exhibition and 

Conference, 28

North Dakota Local Technical Assistance Program Center, 96

Noureldin, Ahmed Samy, 266

Novenski, George, 265

O

Office of Highway Planning, 3, 4

Olds, John R., 260

Online access to LTPP data, 139–141, 215

ONSFIELD software, 120

Onsite support contracts, 271

Operational Problem Report process, 165, 182

Ordway, William A., 258

Origins and evolution of LTPP, 1–2

challenges in, 229–231

events and circumstances leading to, 2–3, 8

expectations for rapid product development in, 231

initial funding, 2, 46

lack of historical data for early research, 230–231

leaders in, 32–33f

legislative actions in, 3

major preliminary studies and pilot programs, 3–5, 6–7, 8

milestones, 2

organizational structure and operations, 7, 12–26

original Advisory Committee, 6

participation in, 3, 8, 257, 258

research plans, 6, 8

transition planning and execution, 5–6, 18–19

Ormesher, Daris, 260, 262

Orr, David, 192f, 263, 265

Ostrom, Barbara, 36f

Overlay

data analysis studies, 202–203

data collection, 86, 89

General Pavement Studies of, 66–68

Specific Pavement Studies of, 70f, 73

Owusu-Antwi, Emmanuel, 266

P

Pacific Aerial Survey Company, 93–95

Pagán-Ortiz, Jorge, 26f, 255b

Page, Richard S., 258

Pagen, Charles A., 259

Pan-American Institute of Highways, 42

Paniati, Jeff, 255b

Papagiannakis, A. Thomas, 266

Papet, Louis M., 259

Parker, Neville, 263

Parker-Smith, Carliss, 19f

Partnerships, LTPP

benefits of, 34, 35, 42

future prospects for, 252

with international community, 42, 252

primary partners, 34, 35, 37–42. See also specific organization

with private sector stakeholders, 41

scope of, 34, 35, 257–258

PASCO ROADRECON survey vehicle, 7, 93, 94, 94f, 103–104, 

103f

PASCO USA, 272

Paterson, William D. O., 260, 266

Pavement Condition Monitoring Methods and Equipment 

Study, 3, 6–7, 8

Pavement Consultancy Services, Inc., 270, 274

Pavement Distress Analysis System, 95, 149–150, 150f

Pavement Health Track Analysis Tool, 219

Pavement Management Systems, Ltd., 270, 271

INDEX    297
Pavement Performance Advisory Committee (Advisory 

Committee), 17–18, 18, 25, 63, 66, 258, 258t, 259–261

Pavement Performance Database, 132, 245b

Pecnik, Ivan, 19f, 270

Peer review groups, 17–18, 25–26, 181, 269–270

Pendleton, Olga, 259, 262, 265, 266

Pennsylvania Department of Transportation, 92, 202

Pensok, Ed, 64b

Personnel, qualifications for data collection, 167–168

Peters, Art, 259

Peters, Mary E., 59

Peterson, Dale, 259

Petzold, Roger, 259

Phillips, David K., 259

Phillips, David W., 261

Phoenix FWD, 7

Photographic distress surveys, 17, 93–95, 271–272

Photographic transverse profile studies, 103

Pierce, Linda, 263, 264

Pisarski, Alan, 265

Pitz, Miriam, 30f

Planning and advisory committees, 257–258, 258t

Planning and Pre-Implementation Advisors, 258, 258t

Polish, Patricia, 263

Portera, Joy, 260, 262

Portland cement concrete, 170–171, 246–247

General and Specific Pavement Studies, 8t, 74t, 83, 238

joint openings, 116

SHRP testing program, 17, 191, 210

transverse profiles, 105

Pothole repair, 191, 209, 210

Potter, John F., 266

Prakash, Anand, 260

Preserving and Maximizing the Utility of the Pavement 

Performance Database, 46–47

Products, LTPP

data collection and, 235

defined, 132

expectations for rapid development of, in early program, 

231, 235

Expert Task Group on development and delivery of, 264

funding for development of, 205

future opportunities for development of, 251

goals of future development, 244–245

goals of 1996 program assessment, 236

for maintenance and rehabilitation, 209–210

for new and reconstructed pavements, 207–209

organizational structure of LTPP program and 

development of, 232

pavement management system tools and techniques, 

210–212

plan development, 205–207

program accomplishments, 189, 204–205, 206f, 251

program objectives, 204, 205, 207, 209, 210, 212

for study of environmental effects, 214

for traffic loading studies, 212–214

See also Database, LTPP

Professional Service Industries, Inc., 273

Profile data, 16

longitudinal, 99–102

management responsibilities, 21

transverse, 103–105

Profiling equipment, 99f, 100f, 101f, 168, 169b, 171

acceptance testing, 282–283

capabilities, 281–282

data filtering, 281

equipment comparisons, 100–101, 170

equipment contracts, 272

LTPP program purchases, 281, 282t

quality control, 101–102, 180

standards, 212

Program Assessment (1996), 26, 66–68, 84, 236–238

Program directives, 30

Program Improvement Campaign, 236–237

Program Improvement Subcommittee, 26

ProQual, 101–102, 104, 172, 173

ProVAL, 102, 212

ProXport, 102

Prozzi, Jorge A., 266

Pryor, Charles A., Jr., 259, 262, 264

Public access to LTPP data, 134–135, 136–137

Publications, 29

documentation of LTPP activities and products, 240, 245b

falling weight deflectometer manuals, 93

FHWA standards, 181

LTPP library of, 156–157

Puccinelli, Jason, 30f

Purdue University, 92

Q

Quality assurance/quality control

accomplishments of LTPP program, 183–184, 217–218

after data collection, 173–175

database audits, 177–178

database checks and reviews, 175–176

in database process, 135, 136f, 139

before data collection, 164–170

in data collection, 77, 79, 81–82, 83, 170–173

in data release procedures, 134–135, 136–137, 153

298    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
in distress surveys, 95

equipment requirements for, 168–170

evolution of program requirements for, 163–164

in falling weight deflectometer operations, 91, 280

feedback processes in, 182–183

higher order data checks, 178–180

key milestones in LTPP program, 164b

in longitudinal profile studies, 101–102

in Materials Action Plan, 126

objectives, 163, 216, 218b

peer review activities in, 181

personnel requirements for, 167–168

resources, 218b

role of regional support contractors in, 24

role of technical assistance contractor in, 16, 20–23

in Seasonal Monitoring Program, 120

standards adopted by LTPP for, 183, 212

Queiroz, Cesar A. V., 259

Quinley, Richard, 122f, 265

R

Raab, Robert, 19f, 26f, 36f, 192f, 262, 263, 264, 265, 266

Rasmusson, Eugene, 261

Rauhut, Brent, 266

Reel, Rick, 36f, 122f, 192f, 265

Regional contracts, 12, 13, 16–17

Regional coordination office contractors, 7, 18, 20

in LTPP data collection program, 133

in pavement studies, 68, 74

responsibilities, 16–17

Regional offices, 12, 13f

Regional support contractors, 7, 270–271

contract issuance, 23

data collection role of, 78–79, 133, 134f, 135, 170

in LTPP research programs, 68, 84–85, 95, 105–106

meetings, 27, 29–30

oversight, 19

quality assurance audits of, 177–178

responsibilities of, 23–24, 74, 90

in traffic data collection, 107

training of, for data collection, 167, 168

Rehabilitation. See Maintenance and rehabilitation 

of pavements

Rehabilitation Act, 181

Reilly, Robert J., 259

Reinhardt, Morris, 270

Research

accomplishments of LTPP program, 189

contracts, 24–25

coordination meetings, 27

documentation of procedures and findings, 240

evolution of SHRP program of, 12–13

initial LTPP plans for, 6

LTPP objectives, 1, 11

LTPP partners in, 37–39, 41

major studies in preparation for LTPP, 3–5, 6–7, 8

provisions of Transportation Equity Act for the 21st 

Century for, 51b

rationale, 58, 59

role of regional coordination office contractors in, 16–17

role of technical assistance contractor in, 15–16, 21, 23

SHRP objectives, 4, 5b, 6

in U.S. prior to LTPP, 2–3, 4

See also Experiments, pavement

Researcher’s Guide to the Long-Term Pavement 

Performance Thickness Data, 209

Resilient modulus, 151, 151f, 173

data studies, 180

testing responsibility, 238

test procedures, 208, 218b

Revenue Aligned Budget Authority, 46

Rhode Island LTPP Specific Pavement Study Workshop 

(2000), 27, 238–239

Richter, Cheryl, 19f, 192f, 255b, 263

Rigid pavement design, 207

Riley, Randell, 259

Rizenbergs, Rolands L., 259

Road and Transportation Association of Canada, 3

Road Profiler User Group, 28

Road Rater, 7

Roads and Transportation Association of Canada, 37

Roadway Express, Inc., 41

Robinson, Gary K., 259

Rodeos, equipment, 100–101, 170, 170f

Rodriguez, Luis, 192f

Rogers, Richard, 122f, 260, 263, 265

Roos, Daniel, 258

Rosenberger, James, 266

Ross, Frederic R., 259, 262

Rowshan, Shahed, 19f, 255b, 266

Rutting data, 102, 145, 191

S

Sack, Robert L., 262

Safe, Accountable, Flexible, Efficient Transportation Equity 

Act: A Legacy for Users, 26, 45, 46, 53–56, 53b, 54t, 239

Santos, Luis de Picado, 266

Schleppi, Brian, 192f, 260, 263

Schoenhard, Larry, 265

Schofer, Joseph L., 258

INDEX    299
Science Applications International Corporation, 270, 274

Scofield, Larry, 122f, 260, 262, 264, 265

Scott, Ted M., II, 259, 262*

Seasonal Monitoring Program, 24, 30, 51, 52, 169

accomplishments of, 116, 121, 128

CD-ROM, 214

data interpretation, 120–121

data storage, 145

equipment calibration, 169, 170

equipment used in, 283–285

geographic distribution of instrumented sites in, 116f, 117

monitoring equipment, 117, 117f, 118, 118f, 119f, 120f

monitoring schedule, 119

objectives of, 105

origins of, 116

Phase II monitoring, 119–120

Phase I monitoring, 119

pilot programs, 117–118

purpose of, 115–116, 214

qualifications of personnel for, 167

quality assurance audits of data from, 177

quality control software for, 120, 172

scope of, 117, 119

training sessions, 120

Selezneva, Olga, 26f, 36f, 192f

Senn, Kevin, 30f, 192f

Sexton, Jean, 255b

Shah, Shashikant, 19f

Sharpe, Gary, 260, 262, 264

Shatnawi, Shakir, 264

Sheriff, Margie, 19f

Sherwood, James A., 260, 266

Shober, Stephen, 264

SHRP. See Strategic Highway Research Program

SHRPBind, 200, 208

SHRP-LTPP Overview: Five-Year Report, 64

Sidekick® software, 102

Sierra Transportation Engineers, Inc., 274

Sivaneswaran, Nadarajah, 192f

Slab width, 200

SLIC, 91

Smith, Harry A., 259

Smith, Karen, 19f

SMPCheck, 120

Smutzer, Richard K., 262

Software Performance Reports, 176, 182–183

Soil and Materials Engineering, Inc., 270, 271, 274

Southwest Labs, 273

Sparks, Gordon, 266

Specific Pavement Studies, 6, 37

benefits of ongoing data collection, 248t

cost of, 73

current state of original experiments, 248

data collection in, 79, 232

data storage, 145

design criteria, 65b

drainage data collection in, 98

dynamic load response data collection in, 83

evolution of experimental designs in, 70–71, 71t

experiments, 8, 8t, 70, 71t, 74t

future prospects for, 74

General Pavement Studies and, 69

ground penetrating radar measurements in, 83–84

inventory data, 84–85, 105–106

management structure and responsibilities for, 16

materials sampling in, 87–89, 238

purpose of, 63, 69

research design matrices, 70, 70f

role of LTPP State Coordinators in, 234

Superpave® mix project, 71–72

supplemental sections, 65b, 72, 72b

test sections, 65b, 72–74, 73f, 74f

traffic data collection in, 213, 237

weather data collection in, 80

See also Traffic Data Collection Pooled-Fund Study

Springer, Jack, 27f, 30f, 192f, 255b, 264, 265

Sršen, Mate, 266

Stantec, 271

“Stars” report. See Strategic Transportation Research Study

Startup procedures, 169, 208

State and provincial highway agencies, 1, 46, 47

contributions to LTPP program, 20, 34f, 39–40

data analysis studies, 199–203

financial support to LTPP program from, 234

LTPP program communication with, 27, 28

SHRP and, 3

staff commitment to LTPP program, 234

See also American Association of State Highway and 

Transportation Officials

State Coordinators, LTPP, 40

Stoffels, Shelley, 192f, 260, 263, 265

Stokoe, Ken, 260

Stolz, Elizabeth, 122f, 265

Strategic Highway Research Program Research Plans, 70

Strategic Highway Research Program Research Plans, Final 

Report (1986) (“Brown Book”), 6, 6f, 40, 48, 70

Strategic Highway Research Program (SHRP), 32b

Advisory Committee, 259

Canadian participation in, 37–39

300  THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM *Revised on 5/18/2017
data analysis efforts, 190–191

database development under, 133–135, 134f

funding, 4, 11, 46, 48

legislative authorization, 5, 49b

LTPP management under, 12, 13–18, 14f, 40, 231, 232, 257

LTPP origins in, 2, 5, 6, 8, 11

LTPP transition from, 18–19, 269–270

management structure and responsibilities, 13

Midcourse Assessment Meeting, 234–235

national workshops, 6

origins of, 2, 3, 4–6

planning studies, 258

profilometer purchases, 281

regional support contracts, 270

research program, 4, 5b, 6, 12–13, 63–64, 66, 68, 70, 71

Task Force, 259

technical support contracts, 270

Strategic Pavement Design Initiative, 70

Strategic Plan for Data Analysis, 181, 250

Strategic Transportation Research Study (“Stars” report), 3, 

4–5, 7, 41, 258

Stubstad, Richard N., 260

Study of Long-Term Pavement Performance (LTPP): 

Pavement Deflections, 91

Subcommittee for Product Development and Delivery, 26

Subcommittee on Experimental Design, 63

Subsurface measurements, 90, 116, 117, 118, 118f, 120, 121, 198, 284

Sullivan, Dick, 259

Superpave® mix, 71–72, 243

Surface Transportation and Uniform Relocation Assistance 

Act (1987), 5, 12, 45, 46, 48–50, 49b, 49t

Surface Transportation Assistance Act (1978), 3

SurPRO, 100

Sweere, Govert, 266

Symons, Monte, 19f, 33f, 255b, 262, 264

T

Tahir, A. Haleem, 262, 264

Tarefder, Rafiqul Alam, 266

Tarpgaard, Sarah, 30f

Tayabji, Shiraz D., 259, 266

Taylor, Gary, 36f, 259, 260, 262, 264, 265

Technical assistance contractor, 7, 19–20, 68

role of, 12, 15–16, 20–23

Technical support services contractor, 7, 13f, 19–20, 23, 270

data collection role of, 78–79, 133, 157, 176

meetings, 29–30

quality control program, 178

Technology transfer, 17

Tektronics cable tester, 117, 283, 285

Temple, William, 26f, 262

Teng, Paul, 19f, 20f, 32b, 255b, 259, 266

Test sections

asphalt thickness measurement of, 83–84

benefits of ongoing data collection, 248, 248t

current state of original LTPP experiments, 248

distress surveys, 93–98

dynamic load response data collection in, 83

forensic studies, 127, 249

future uses of, 251–252

for General and Special Pavement Studies, 65b, 68–69, 

72–74, 72b, 73f, 74f

geographic distribution, 74f

inventory data, 84–85

length, 65b

in LTPP approach, 1

LTPP database records, 136

LTPP partners in research on, 37, 38f, 39

management responsibilities, 16, 24

pavement performance data collection, 247–248

in Seasonal Monitoring Program, 117

testing and storage, 88

traffic data collection, 106, 107, 121

Traffic Data Collection Pooled-Fund Study, 122–123, 123f

Test sites

for General Pavement Studies, 68, 74f

geographic distribution, 74f

lack of historical data for early LTPP research, 230

location data, 85

management responsibilities, 16, 17

marking of, for pavement studies, 69f

online data access, 154

for Specific Pavement Studies, 73–74, 74f

weather and climate data collection at, 80–83

Texas Department of Transportation, 28, 28b, 202–203

Texas Research and Development Foundation, 270

Thermographic scanning, 247

Thickness, pavement, 209

Thirumalai, K. T., 19f f

Thompson, Marshall R., 259, 260, 264

Thump-offs, 90, 90f, 92, 170

Thurmann-Moe, Thorkild, 266

Tighe, Susan, 192f, 263, 265

Time domain reflectometer, 117, 146, 284

Time-series checks, 179

Torrey, Ray, 19f

Traffic data collection

challenges in, 107, 237

contracts, 17, 272–273

equipment, 107–108, 237

evolution of, 107, 108, 237

INDEX    301
Expert Task Group, 261, 264–265

future prospects for, 252

historical data, 106

inaccurate assumptions about, in early LTPP research, 

230–231

LTPP products for, 212–214

management responsibilities, 20, 21, 23

monitored data, 106–107

quality control checks, 175

rationale for, 77

responsibility for, 107, 232

storage, 145, 148

transmittal forms, 106f, 108f

types of data in, 106–107

See also Traffic Data Collection Pooled-Fund Study

Traffic Data Collection Pooled-Fund Study, 78, 115, 121–125, 

128, 207, 212–214, 213f, 237–238

Traffic loading

data sources in use prior to LTPP, 2

goals of LTPP, 1

LTPP products for study of, 212–214

Traffic Monitoring Guide, 107, 175, 175f

Training of personnel for data collection, 167–168

Transportation Association of Canada, 37, 234

Transportation Equity Act for the 21st Century, 45, 46, 

51–53, 51b, 52t, 205

Transportation Pooled-Fund Study, 92

Transportation Research Board, 32b, 108, 199, 270

Data Analysis Working Group, 28, 203, 250, 257, 266

in development of LTPP product plan, 205

Expert Task Group on LTPP Data Analysis, 191–192, 263

on future of LTPP, 244b

LTPP Committee, 236, 261–262, 265

as LTPP partner, 35, 40

National Cooperative Highway Research Program, 5

operation of LTPP database by, 133

in origins of LTPP, 3, 4

in origins of SHRP, 5–6

peer review of LTPP programs by, 25–26

in transition of LTPP from SHRP, 18

Transport Canada, 37

Transverse profile data, 103–105, 145, 150, 150f

Trentacoste, Michael, 255b

Turner-Fairbank Highway Research Center, 19, 21f, 56, 137, 

138f, 140f, 141, 181, 245b, 284

Tweedie, Ronald, 265

U

Uddin, Waheed, 266

Ulery, Harry H., Jr., 259

Ullidtz, Per, 260

Undersealing, 86

University of Texas at Austin, 274

University of Texas Center for Transportation Research, 270

U.S. Army Corps of Engineers, 117

USAID, 42

User groups, 35, 41

Uzan, Jacob, 260

V

Van Berkel, John, 261, 265

Van Blerk, Gerhard, 266

Vandenbossche, Julie, 192f, 263

Van Kirk, Fred, 259

Vehicle classification, 214

Virtual weather stations, 82–83, 82f

Vischer, William, 263

Von Quintus, Harold, 19f

W

Walker, Deborah, 30f, 36f, 192f, 255b, 263, 265

Walls, James, 260, 263

Walters, Robert, 262

Walton, C. Michael, 204f, 262

Wardlaw, Kenneth R., 259

Warm-mix asphalt, 8, 19, 27, 64, 74, 84, 216, 249–250

Warpoole, Doug, 261

Warren, Kenneth I., 262

Wass, George, 265

Way, George B., 259

Weather stations, 80–83, 80f, 81f, 82f, 144, 167, 172, 173, 177, 

277–278. See also Seasonal Monitoring Program

Weaver, Eric, 192f, 255b, 263

Weaver, John R., 263, 265

Webinars, 28–29, 29b, 216

Weed, Richard M., 260, 265

Weigh-in-motion data, 107, 121, 122, 122t, 124–125, 174, 212, 

213–214, 237

Expert Task Group, 261

system contracts, 273

Wells, Sarah, 262

Wen, Haifang, 266

West, Randy, 263

Western Research Institute, 88

Westinghouse Environmental and Geotechnical Services, 273

WesTrack, 88

Wheeler, Homer, 19f, 270

White, Stella, 19f, 259

White, Thomas D., 259, 263

White, Tom, 192f

302    THE LONG-TERM PAVEMENT PERFORMANCE PROGRAM
Whited, Gary C., 262

Williams, Greg, 266

Williams, Marcus, 259

Wiser, Larry, 26f, 30f, 192f, 255b, 263, 265, 266

Witczak, Matthew W., 259

Wolf, Dean, 36f

Wong, Bing, 264

Woodle, Clyde, 265

Wootan, Charley V., 259

Worel, Ben, 192f, 263, 264, 265

Work zone safety, 13

World Bank, 42

World Road Association–PIARC, 42

Wrong, Gerry, 260

Wu, Shie-Shin, 192f, 260, 263

Wyman, John, 261

Y

Yang, Wei-Shih, 265

Yang, Wes, 192f, 260, 263, 264

Young, William A., 260

Yourcheff, Jack, 19f

Yowell, James McFarland, 262

Yu, Tom, 192f

INDEX    303
© American Concrete Pavement Association, www.acpa.org
Acronyms

AADT average annual daily traffic 

AASHO American Association of State Highway 

Officials

AASHTO American Association of State Highway 

and Transportation Officials

AC asphalt concrete

ADEP AIMS Data Entry Portal

AIMS Ancillary Information Management System

AMRL AASHTO Materials Reference Laboratory

APT accelerated pavement testing

ASCE American Society of Civil Engineers

ASCII American Standard Code for Information 

Exchange

ASTM ASTM International, formerly American 

Society for Testing and Materials

ATB asphalt-treated base

ATDL automated temperature data logger

AVC automatic vehicle classification

AWS automated weather stations

BAA Broad Agency Announcement

CCC Canadian Climate Center

CDOT Colorado Department of Transportation

COPES Concrete Pavement Evaluation System

CRCP continuously reinforced concrete pavement

CRREL Cold Regions Research and Engineering 

Laboratory

C-SHRP Canadian Strategic Highway Research 

Program

CSI Campbell Scientific, Inc.

CSSC Customer Support Service Center

CTB cement-treated base

CTDB Central Traffic Database 

CTDOT Connecticut Department of Transportation

CTE coefficient of thermal expansion

DAOFR Data Analysis/Operations Feedback Report

DAWG Data Analysis Working Group

DCP dynamic cone penetrometer 

DIM Distress Identification Manual

DiVA Distress Viewer and Analysis

DLR dynamic load response

DMI Distance Measuring Instrument

DOT Department of Transportation

ESAL equivalent single-axle load

ETG expert task group

FALCON Focus Area Leadership and Coordination

FHWA Federal Highway Administration

FWD falling weight deflectometer

FWDUG FWD User Group

GOE General Operating Expenses 

GPR ground penetrating radar 

GPS General Pavement Study

GPSr Global Positioning System receiver

acronyms    305
HERS Highway Economics Requirement System

HMA hot-mix asphalt

HPMS Highway Performance Monitoring System

ICC International Cybernetics Corporation

IDIQ indefinite delivery/indefinite quantity

IMS Information Management System

IPRD Innovative Pavement Research and 

Deployment Program

IRI International Roughness Index

ISO International Organization for 

Standardization

ISTEA Intermodal Surface Transportation 

Efficiency Act of 1991

JCP jointed concrete pavement 

JPCP jointed plain concrete pavement

JRCP jointed reinforced concrete pavement

KDOT Kansas Department of Transportation

LCOM LTPP Committee

LDEP LTPP Data Entry Portal

LSPEC LTPP Special Activities Committee

LTAS LTPP Traffic Analysis Software

LTBP Long-Term Bridge Program

LTM Long-Term Pavement Monitoring

LTPP Long-Term Pavement Performance Program

LTPP-PLUG LTPP Pavement Loading User Guide

MAP-21 Moving Ahead for Progress in the 21st 

Century Act

MEPDG Mechanistic-Empirical Pavement 

 Design Guide

MERRA Modern Era–Retrospective Analysis for 

Research and Applications

MPD mean profile depth

MRC Measurement Research Corporation

MRL Materials Reference Library

MS-DOS® Microsoft Disk Operating System

NASA National Aeronautics and Space 

Administration

NCDC National Climatic Data Center

NCHRP National Cooperative Highway 

Research Program

NDT nondestructive deflection testing

NHI National Highway Institute

NIMS National Information Management System

NOAA National Oceanic and Atmospheric

Administration 

NRC National Research Council

NYSDOT New York State Department of 

Transportation

OPR Operational Problem Report 

OWL Optimal WIM Site Locator software

PADIAS PAvement DIstress Analysis System

PCC Portland cement concrete

PennDOT Pennsylvania Department of Transportation

PG performance grade

PHT Performance Health Track

PLUG Pavement Loading User Guide

PPAC Pavement Performance Advisory Committee

PPCP precast prestressed concrete pavement

PPDB Pavement Performance Database

QC/QA quality control/quality assurance 

RABA Revenue Aligned Budget Authority

RAC rubberized asphalt concrete

RAP recycled asphalt pavement

RCOC regional coordination office contractor

RDBMS relational database management system

RIMS Regional Information Management System 

RSC regional support contractor

RTAC Roads and Transportation Association of 

Canada

SAFETEA-LU Safe, Accountable, Flexible, Efficient 

Transportation Equity Act: A Legacy 

for Users

SCOR AASHTO’s Standing Committee on Research 

SDR Standard Data Release

SHRP Strategic Highway Research Program

SI International System of Units

SMERP Supplemental Maintenance Effectiveness 

Research Program

SMP Seasonal Monitoring Program

SOM Subcommittee on Materials

SPR Software Performance Report

SPS Specific Pavement Study

STAA Surface Transportation Assistance Act of 1982

STRS Strategic Transportation Research Study 

STURAA Surface Transportation and Uniform 

Relocation Assistance Act of 1987 

TAC technical assistance contract/contractor

TEA-21 Transportation Equity Act for the 21st 

Century

TDR time domain reflectometer

TFHRC Turner-Fairbank Highway Research Center

TRB Transportation Research Board

TSSC technical services support contract/ 

contractor

TxDOT Texas Department of Transportaion

VMS® Virtual Memory System

WAAS Wide Area Augmentation System

WIM weigh-in-motion

WMA warm-mix asphalt

306    THE LONG-TERM PAVEMENT 
Publication No. FHWA-HRT-15-049

HRDI-30/09-15(700)E

Cover image: © MaxyM/Shutterstock.com