The Long-Term Pavement Performance Program

PART I. BUILDING AND MANAGING THE LTPP PROGRAM

Credit: © apiguide/Shutterstock.com. 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.

CHAPTER 1. ORIGINS OF THE LTPP PROGRAM

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.

Introduction

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 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-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.

The Need To Understand Pavement Performance

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 2000s^6,7,8 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 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 research-quality 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 Pavement Monitoring Idea

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 Study

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 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 Study

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 the Strategic Transportation Research Study, TRB Special Report 202 (1984) or "Stars" report, which identified high-priority areas for a national highway research program.

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 Momentum Until SHRP-LTPP Begins

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 contractor 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 Long-Term 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 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 Methods and Equipment Study

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 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

FIGURE 1.2. The 1986 Strategic Highway Research Program Research Plans, known as the “Brown Book.”

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 Activities

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 PAVEMENT PERFORMANCE GOAL AND OBJECTIVES

The goal established for the SHRP-LTPP studies was “to increase pavement life by the investigation of long-term 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 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.

Summary

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 experiments.

References

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-LTPP-OG-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.