The Superpave Mix Design System: Anatomy of a Research Program (2012)

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6 CHAPTER 3. PRE-RESEARCH PHASE (1980-1987) This chapter discusses the time period from 1980-1987. During this time, there was growing support for a national research program to address widespread problems with the highway infrastructure, maintenance and operation. Funding support was obtained and the plans for the research program were developed. 3.1 SEEDS OF THE RESEARCH PROGRAM The origins of the SHRP Program reach back to the late 1970s and early 1980s. In the late 1970s, after years of neglect, the nation’s highway system had deteriorated to a publicly perceptible and technically unacceptable level. Recognizing the need for a revitalized highway program, Congress authorized a four-year, $58 billion federal-aid package for highways in 1982. Financing alone, however, would not solve the problem. It was a well-documented fact that needs far exceeded resources. Eventually, it was realized that innovation, through carefully targeted research, was the key to bridging the gap. In the early 1980s, many people seriously believed that something was wrong with asphalt pavements. Bob Farris, Commissioner of the Tennessee DOT at the time and later the FHWA Deputy Administrator, may have been one of the first on a national level to state that asphalt “wasn’t as sticky as it used to be.” Others may have been saying the same thing, but Farris was the first to get the message out to the community. To track the issue, Farris had his inspectors report directly to him about what was happening. This led to interest at the national level, especially at AASHTO. Farris and others realized that asphalt pavements were not performing as they should. The problems went beyond perception and were real, as evidenced by increasing and premature distress. AASHTO’s Frank Francois and other DOT leaders eventually took up the gavel at the national level and went to visit the refiners. Representatives from the refining industry responded that there was nothing wrong with or different in the product. What was really happening, however, was that the number and types of crude oils that were being used to refine asphalt had dramatically changed as a result of the world wide demand and the oil crisis of the 1970s. Other problems were noted with the inexperience of lab technicians and inspectors, along with the workmanship of some paving contractors. The DOT leaders also wanted to know if other products or materials were suffering from poor serviceability. In their review, they found out there were technical problems with other materials as well; rebar quality (corrosion) and alkali-silica reactivity were common problems. The quality and serviceability issues with these materials were brought before the AASHTO Standing Committee on Research (SCOR). SCOR was asked to look at this issue, but did not have sufficient funds at its disposal to conduct any type of large-scale, organized study. The idea of a focused research program was raised, though the actual source is hard to pinpoint. Thomas D. Larson, at the time the Secretary of the Pennsylvania Department of Transportation, and Thomas B. Deen, Executive Director of TRB, had many high level discussions on this issue. Together, they probably deserve credit as the first authors of the idea of a high level research project, in modules or blocks, to deal with these issues and to be responsive directly to the state DOTs. Their initial work led to an outline of a research program.

7 Lester P. (Les) Lamm, the FHWA Executive Director at the time, was very much in support of the idea of a national research effort. Independently, FHWA agreed that there was enough concern that something needed to be done. Ray Barnhart, then FHWA Administrator, was supporting a broader and bolder research program at FHWA at the same time. 3.1.1 Structuring the Research Program The normal practice at the time would have been to advertise and award research, with universities being the primary recipients of either grants or contracts with FHWA. Lamm was concerned that a program as significant as this, if given directly to universities, would be extremely difficult to manage. This was because of a combination of tight federal procurement rules and a “hands-off” university culture. Lamm noted that the universities probably were not going to react positively to very tight schedules and being told in specific detail what the research must accomplish. He suggested that it might be better if AASHTO and TRB looked at a completely different delivery system. Larson and Deen then took it from there and finalized the idea that what was needed was a comprehensive program with multiple emphasis areas, beyond just asphalt. Interestingly, while history will record the program in six different areas (asphalt, concrete, bridges, maintenance cost-effectiveness, snow and ice control, and long-term pavement performance), the real thrust was towards improving asphalt. “To gain widespread support, we needed to address needs in many other areas,” noted Francois. 3.1.2 Funding and Organization Soon questions arose as to how to fund and manage a program of such magnitude. Nothing of this scale had been done in the highway research arena through the traditional organizational structure. The idea that surfaced and eventually was implemented was to make the research program similar to the National Cooperative Highway Research Program (NCHRP) with a take- down per state – on a voluntary basis. Credit for this idea probably goes to Arnie Kupferman from the New York State DOT. He suggested that the contribution be mandatory, with the funds going to FHWA and then over to some element in TRB or AASHTO. AASHTO noted that it had no experience or interest in running a program of this magnitude. That led to discussions at TRB. Could they do something like this? Had they ever done something like this? Did they see it as too controversial? Tom Deen led the examination with the National Academy of Sciences. Eventually, this led to a planning document and framework for a separate entity within NAS. FHWA, through Les Lamm, approved the concept of funding and management of the program, using Federal-aid funds as the source of the program.

8 3.2 SHRP’S COLORFUL PRECURSORS – THE “BLUE” AND “BROWN” BOOKS The Strategic Highway Research Program was originally proposed in TRB Special Report 202, America's Highways: Accelerating the Search for Innovation (2). Published in 1984, the “Blue Book” contained the findings of the Strategic Transportation Research Study (STRS) sponsored by the FHWA and conducted by TRB. The Blue Book documented the need for a concerted research effort to produce major innovations for increasing the productivity and safety of the nation's highway system. It included recommendations for a $150 million, five-year program of research focused on six high-priority areas. Enthusiastically accepting the recommendations, AASHTO and FWHA led the effort to earmark 0.25 percent of Federal-aid highway funds for SHRP in fiscal years 1987 through 1991. Detailed planning for the research program began in March 1985. Seven contract agencies, each supported by an advisory committee of representatives from the highway community, worked for nearly one year to develop the well-defined plans described in the NCHRP Project 20-20 report, Strategic Highway Research Program Research Plans (1), more commonly known as the “Brown Book.” A timeline of key events preceding the onset of SHRP is shown in Figure 1. Relevant highlights from the Blue and Brown Books are contained in the following sections. Figure 1 Timeline of Key Events Preceding the Onset of SHRP 3.2.1 The “Blue Book” The STRS study focused exclusively on public highway facilities and examined transportation research from the vantage point of a “unified industry.” This unified industry encompassed highway construction, maintenance and operating activities performed by federal, state, county, city and other operating units of government as well as toll facilities. The Committee that conducted the study was charged with developing a five-year plan for strategic highway research. Noting that spending on highway research had fallen precipitously from 0.25 percent in 1965 to 0.15 percent in 1982, the obvious question was “Why Jan 1983 Jul 1984 May 1984 Oct 1984 Mar 1985 Sep 1985 Jan 1986 Feb 1986 May 1986 STRS Committee Formed SR 202 "Blue Book" Published AASHTO Approves SR 202 Recommendations Office of SHRP Interim Director Established & SHRP Task Force Formed SHRP Task Force Begins Work (NCHRP 20-20) SHRP Workshop - Dallas, TX SHRP Workshop - TRB SHRP Research Plans Finalized SHRP "Brown Book" Published

9 had a system crucial to the nation’s economy and everyday life not been supported by large- scale, long-term research?” The answer to that question was found in the characteristics of the highway industry, its traditional approach to research, and gaps in technology, specifically asphalt technology. These characteristics are summarized as follows (2):  The highway industry was (and remains) dispersed and diverse. Some 38,000 agencies share responsibility for operation of the nation’s highways, roads and streets. This decentralization of responsibility increased the sensitivity to local needs and issues as well as to regional topographic, climatic and in situ conditions affecting highway design and maintenance. The private sector, with nearly 65,000 firms producing or supplying materials, was fragmented into thousands of small, local buyers and sellers.  The financial commitment to highway research lagged far behind the investment in research in other sectors of the economy. High-technology industries, including computers, pharmaceuticals, and aerospace, spent nearly 40 times as much on research as the highway industry. The highway industry even trailed behind low-technology industries, such as building materials, metals and mining, and food and beverage, which spent more than eight times as much on research.  The complexity of highway construction and maintenance was poorly understood, so research was not considered a high priority. Road-building was familiar and most certainly not glamorous. When budgets were tight, highway research could be easily and indefinitely deferred.  As shown in Figure 2, the nearly $75 million that the United States spent on highway research in 1982 was disbursed through numerous agencies and programs. In addition to the Highway Planning and Research (HP&R, later called State Planning and Research (SPR)), NCHRP and FHWA programs, at least seven other federal agencies conducted highway-related research. 3.2.1.1 Gaps in Asphalt Technology Research should be results-oriented in important areas that need improvement. As noted in the previous section, highway research was highly decentralized among all levels of government and many private organizations. No single agency controlled the majority of highway research spending. Also, road quality, safety and environmental consequences were important considerations. These special features of highway research (the need for large-scale integration, and for safety and environmental considerations) combined with the basic requirements of all good research, led the STRS Committee to identify strategic gaps in asphalt research by answering the following questions (2):

10 Would the research yield big payoffs? Yes. About $10 billion per year were spent for asphalt pavements, which was about 20 percent of the nation's overall expenditures on highways. A $50 million research project would repay its costs in six months if it achieved only a one percent savings in asphalt pavement costs. Had the research area been neglected? Yes. Asphalt generated less than one percent of the annual revenue earned by the US petroleum industry and hence was neglected. Had important issues been slighted because of institutional or organizational barriers? Yes. Low-bid procurement discouraged production of higher quality products. Did the research require effort on a larger scale than could be accommodated by existing programs and institutions? Yes. Crude oil used in asphalt production came from 200 different sources. It was refined by numerous refineries and processes; combined with numerous additives, cutbacks, and emulsifiers; mixed with a wide variety of aggregates; and constructed according to different designs under a wide variety of conditions. Did the research require an integrated effort or national approach? Yes. Part of the failure to see the potential of asphalt research stemmed from the lack of a single clear beneficiary. Until an integrated effort brought together the disparate parts of the process, major fundamental improvements in asphalt would not be found. $39.4 $21.5 $7.3 $1.0 $5.0 Highway Research Spending in 1982 by Major Sponsors ($ Millions) States (HP&R and NCHRP) FHWA Other Federal Agencies Cities and Counties Private, Industry Assn and Other Figure 2 1982 Highway Research Spending (data from SR 202 (2))

11 Select analytical methods for characterizing asphalt cement Select representative asphalt cements Select lab tests of pavement performance Select aggregates for test pavements Identify required full-scale field test pavement sections Conduct analysis of asphalt cements Study methods to control and improve asphalt cement characteristics Develop tests and specs for better asphalt cements Conduct lab tests of pavement performance Monitor and evaluate performance on test sections Design and build test sections Elements and relationships of design for asphalt cement experiments Would the research accommodate changes in national policy? Yes. The Surface Transportation Assistance Act of 1982 increased the funding for most federal highway programs, particularly those that financed resurfacing, rehabilitation, restoration and reconstruction (4-R). These were the areas where the greatest percentages of program funds were spent for pavements, so asphalt would increase in financial importance. Would the research use or respond to technological changes? Yes. In short, the oil embargo of the 1970s stimulated the production of asphalt from different crude oils and through different refining processes. 3.2.1.2 Asphalt Program Objectives and Funding The overall objective of the asphalt research program, as articulated in the Blue Book, was to improve pavement performance through an increased understanding of the chemical and physical properties of asphalt cement in the context of its use in pavement. The research results would be used to develop specifications, tests and construction procedures needed to achieve and control the pavement performance desired. To achieve these objectives, five major steps were envisioned: 1. Define properties of different asphalts, 2. Improve testing and measuring systems, 3. Determine relationships between asphalt cement and pavement performance, 4. Develop improved asphalt binders, and 5. Validate performance in the field. The work flow and relationships among the various experiments as originally conceived are illustrated in Figure 3. Figure 3 Elements and Relationships of Design for Asphalt Cement Experiments (after SR 202 (2))

12 Projected funding for this five-year, ambitious asphalt research program was estimated at $10 million per year and was allocated as shown in Figure 4. 3.2.1.3 Institutional Arrangements The strategic plan presented in the Blue Book was more sharply focused than historical highway research efforts. It concentrated on a few specific goal-oriented areas. The highly focused, product-oriented program would exist for only five years (with the exception of the Long-Term Pavement Performance program). Several alternative institutional arrangements were considered, including the following: an AASHTO task force, the TRB/AASHO Road Test organizational model, a federally chartered agency or special study commission, a modification of NCHRP, an expansion of the Federally Coordinated Program (FCP), the National Bureau of Standards, or an independent research center. 3.2.2 The “Brown Book” The recommendations to initiate a strategic highway research program were approved by AASHTO’s Policy Committee in July 1984. The office of the SHRP Interim Director was established in October 1984 with plans to implement SHRP under the guidance of a special task force. L. Gary Byrd was the interim director, following on from his work with the Blue Book. Under the auspices of the NCHRP, six contractors were selected by the SHRP Task Force in early 1985 to develop the specific research plans in each technical area. In addition, an $4 $2 $3 $1 Asphalt Progam Annual Funding - $10 Million (5-Year Total - $50 Million) Laboratory Physical Tests Field Validation Analyses Figure 4 Annual Funding for Asphalt Research Program (after SR 202 (2))

13 advisory committee appointed by the Task Force was created to assist each contractor. The contractor for the Asphalt area was Fred Finn of Austin Research Engineers. Each committee was composed of approximately 30 people and represented a broad range of research organizations, including public and private institutions, academia, and industry. (See Appendix B for the composition of the SHRP Task Force and Asphalt Advisory Committee.) In September 1985 the preliminary research plans were “previewed” at a National SHRP Workshop held in Dallas, TX. Both US and foreign professionals were invited to the workshop. The second broad introduction of the developing SHRP effort occurred at the January 1986 Annual Meeting of the Transportation Research Board in Washington, DC. At this meeting, detailed presentations and discussions were held along with a specially developed program to increase the foreign technical community's awareness of the SHRP study. The individual research plans were finalized by February 1986 and presented to the SHRP Task Force for approval. They were published in NCHRP Report 20-20, Strategic Highway Research Plans, (1), the “Brown Book,” in May 1986. 3.2.2.1 SHRP Organization and Management SHRP was viewed as two distinct phases of management: a pre-implementation phase that was completed with the publication of the Brown Book and an operational phase that began with the process leading to research contracts. In the operational phase, it was envisioned that there would be nine major organizational units with key responsibilities of each as follows: National Research Council SHRP would be administered as a new operating unit of the National Research Council. SHRP Executive Committee Comprised of approximately l5 executives or professionals from industry, government and the academic community (with AASHTO, FHWA, and TRB representation in ex-officio capacities), the Executive Committee would provide major policy guidance for the entire program and oversight guidance to the technical program. SHRP Executive Management Staff The SHRP executive headquarters would include an Executive Director with two Deputy Directors/Managers, one each for technical operations and administrative matters. This staff would have the responsibility for the day-to-day technical and contract management and monitoring. The SHRP offices were established at 818 Connecticut Avenue NW in Washington, DC, in 1986. Technical Research Area Staff This unit would be the operating arm of SHRP management within each technical area. This staff would be responsible for preparation of proposal requests, negotiation of contracts, and direct technical and financial oversight of the program. Loaned Professionals "Loaned" professional staff would work within the technical research areas, offering technical expertise that may not have been readily available as employed staff and/or the perspective of the ultimate users of SHRP results.

14 Data Management Staff This staff would be responsible for management of all technical data collected within the program. Furthermore, this staff would ensure that the system developed would provide for a permanent data bank for all highway researchers upon the conclusion of SHRP. Information Transfer This staff would be responsible for the transfer of technological advances made in the program through the publication and distribution of all reports. Expert Advisors The advisory groups would be comprised of a small number of key professionals who would assist SHRP technical staff in proposal evaluation and in the periodic review of the research progress. Contractor Project Managers It was anticipated that typical research contracts would be large, multitask technical efforts with funding in excess of $1 million. Also, it was envisioned that the research groups would be teams comprised of several organizations such that the prime contractor would be required to develop a project management team to interact directly with SHRP staff. The contractor project manager would be responsible for technical and financial management of all subcontractor agencies comprising the research "team." The preceding narrative outlined what was envisioned in the Brown Book. With few exceptions, e.g., no Deputy Directors or Data Management Staff, this is the organizational structure presented in Chapter 4, at least conceptually. Elsewhere, “loaned professionals” became “loaned staff” – personnel from highway agencies in the US and abroad. In large measure, the loaned staff members were there to provide insight from the “user-agency” perspective. The “expert advisors” were expanded to include “Expert Task Groups” in addition to the advisory committees. The role of the Expert Task Groups was to assist in the selection of research contractors and provide somewhat loosely organized, ongoing peer review of the research progress. 3.2.2.2 Major Program Considerations Other considerations that were thought to enhance the probability of SHRP’s success included the following:  Broad input: Input from a broad sector – private industry, individual consultants, federal and private research institutes, university researchers and research centers, and consulting engineering companies – was encouraged.  Coordination with non-SHRP research programs: SHRP was intended to supplement existing research efforts, not replace them.  User involvement: SHRP should provide the opportunity for involvement by a variety of interest groups including state highway and transportation agencies, private industry and the international community.

15  Innovation: Several approaches to increase innovation were considered: allocating funds for unsolicited proposals; contracts with incentives; and private industry participation, particularly where new instrumentation, equipment and materials were anticipated.  Data management: A data management system was considered critical to the application and use of the knowledge and information developed in SHRP. Types of data considered included the following: technical data from all research areas; literature and textual information; and business management data. It was envisioned that all technical data that supported major findings and conclusions would be preserved so that they could be validated, referenced and expanded upon by subsequent research. Furthermore, it was envisioned that the data would be easily accessible to all interested and qualified users. A relational database to facilitate efficient input, storage, manipulation and access was the goal. The possibility of user fees to offset data system costs was considered.  Implementation of results: All SHRP research efforts were to devote some portion of project activity to an implementation plan with parallel efforts through the following: • FHWA Office of Implementation; • Executive summary-type reports and publications, furnished at periodic intervals; • Demonstration projects; • Private-sector involvement; • New test methods in AASHTO and ASTM format; • TRB publications and meetings; • Technology transfer programs through local agencies; • SHRP publications; and • National SHRP conferences. The asphalt program was successful in soliciting input from a broad sector of stakeholders. It did not, however, succeed in developing a data management system that “supported major findings and conclusions … so that they could be validated, referenced and expanded upon by subsequent research.” Moreover, the asphalt program data are not “easily accessible to all interested and qualified users,” and there is no “relational database to facilitate … manipulation and access.” 3.2.2.3 Asphalt Projects, Budgets and Schedule Detailed planning for the asphalt research program was led by consultants (based on guidance from the Blue Book) with significant input from the AASHTO SHRP Task Force and Asphalt Advisory Committee. There was considerable emphasis on the chemical and physical properties of asphalt cement, despite the general consensus that chemical properties would not be useful for specification purposes. As expected, there were differences of opinion among members of the Advisory Committee as to research topics and corresponding funding allocations. Following three meetings of the Advisory Committee and the National Workshop in September 1985, the program that emerged included five projects and 25 tasks/subtasks, with funding as shown in Table 1 and Figure 5. In preparing the research plan, the SHRP Task Force, Advisory Committee and consultants identified two ongoing NCHRP projects that would affect the research on asphalt- aggregate mixes: NCHRP Projects 10-26(A), Performance-Related Specifications for Hot-Mix

16 Asphalt, and 9-6(1), Asphalt-Aggregate Mixture Analysis System (AAMAS). The objective of 10- 26(A) was to develop performance-related specifications for hot-mix asphalt concrete. The objective of 9-6(1) was to develop an asphalt-aggregate mixture analysis system (AAMAS). These projects were intended to provide an early start for, and to complement, the planned SHRP research. The objective of each SHRP asphalt project is briefly summarized as follows: Project 1 ─ Asphalt Properties The objective of this project was to develop a better understanding of the chemical compositional factors of asphalt that determine its physical properties and influence durability. Understanding the unique properties of recycled asphalt that influence the performance of asphalt-aggregate systems was also important. Project 2 ─ Performance-Based Testing and Measuring Systems The overall objective of this project was to develop testing and measuring systems to define the chemical and physical properties of binders and the mechanical properties of asphalt-aggregate systems. Ideally, the standardized tests would be developed in AASHTO and ASTM formats. Project 3 ─ Models to Predict Pavement Performance To develop performance-based specifications for asphalt binder and an asphalt-aggregate mix design and analysis system, several steps were necessary: development of performance prediction models using empirical or mechanistic-empirical procedures, calibration of the models to field performance, and evaluation with additional field observation. Project 4 ─ Performance-Based Specifications and an Asphalt-Aggregate Mix Analysis System The end-product of this project would be performance-based specifications for asphalt binder and a comprehensive Asphalt-Aggregate Mix Analysis System (AAMAS). The asphalt- aggregate mix analysis would describe laboratory procedures and requirements for the laboratory evaluation of asphalt binders (virgin, recycled or modified) and aggregate to minimize the occurrence of fatigue cracking, low-temperature cracking and permanent deformation. The performance-based specifications would incorporate the findings of Projects 1, 2 and 3. Project 5 ─ Coordination The objective of the coordination project was to assure that the combined efforts from each project would remain focused on the overall goals of performance-based specifications and the AAMAS.

17 Table 1 Proposed Asphalt Projects, Tasks and Budgets (after SHRP Research Plans (1)) Project 1 – Asphalt Properties $ (Million) 1.1 Asphalt Chemical Composition $ 4.00 1.2 Physical Properties of Asphalt $ 2.50 1.3 Relationships Between Asphalt Chemical and Physical Properties $ 3.50 1.4 Relationships of Asphalt Chemical and Physical Properties to Pavement Performance $ 2.00 1.5 Fundamental Properties of Asphalt-Aggregate Interaction Including Adhesion and Absorption 1.5a Physiochemical Properties of Asphalt at the Asphalt-Aggregate Interface $ 2.50 1.5b Physiochemical Properties of Asphalt Used with Absorptive Aggregates $ 1.50 1.6 Survey of Current Manufacturing Practices $ 1.00 1.7 Asphalt Modification $ 5.00 Subtotal $ 22.00 Project 2 – Performance-Based Testing and Measuring Systems 2.1 Testing and Measuring Systems for Asphalt (with and without asphalt modification) $ 3.50 2.2 Testing and Measuring for Asphalt-Aggregate Systems (with and without asphalt modification) 2.2a Fatigue Cracking of Asphalt-Aggregate Systems $ 2.00 2.2b Permanent Deformation of Asphalt-Aggregate Systems $ 2.50 2.2c Low-Temperature Cracking of Asphalt-Aggregate Systems $ 1.50 2.2d Aging of Asphalt-Aggregate Systems $ 1.00 2.2e Water Sensitivity of Asphalt-Aggregate Systems $ 1.50 2.3 Relationship of Asphalt Chemical and Physical Properties to Asphalt- Aggregate Mixture Properties $ 3.00 Subtotal $ 15.00 Project 3 – Pavement Performance Studies 3.1 Model Development $ 0.50 3.2 Asphalt Performance Studies $ 3.00 3.3 Evaluation Procedures for Prediction Models $ 1.00 Subtotal $ 4.50 Project 4 – Performance-Based Specifications for Asphalt and Asphalt- Aggregate Systems 4.1 Performance-Based Specifications for Asphalt $ 3.00 4.2 Performance-Based Specifications for Asphalt-Aggregate Systems (AAMAS) $ 2.00 Subtotal $ 5.00 Project 5 – Coordination 5.1 Research Project Coordination $ 1.00 5.2 Operate Materials Reference Library $ 1.50 5.3 Experiment Design $ 0.50 5.4 Economic Considerations $ 0.10 5.5 Implementation Packages $ 0.40 Subtotal $ 3.50 Total $ 50.0

18 $22.0 $15.0 $4.5 $5.0 $3.5 Asphalt Program Budget Estimate ($ Millions) Asphalt Properties Performance-Based Testing and Measuring Systems Pavement Performance Studies Performance Based Specs for Asphalt and Asphalt-Aggregate Systems Coordination Figure 5 Asphalt Program Budget Estimate (data from SHRP Research Plans (1))

19 The schedule proposed to accomplish the asphalt program research is shown in Figure 6. YEAR 1 2 3 4 5 1.1 Asphalt Chemical Composition 1.2 Physical Properties of Asphalt 1.3 Relationships between Asphalt Chemical and Physical Properties 1.4 Relationships of Asphalt Chemical and Physical Properties to Pavement Performance 1.5 Fundamental Properties of Asphalt-Aggregate Interaction (Adhesion and Absorption) 1.6 Survey of Current Asphalt Manufacturing Practices 1.7 Asphalt Modification 2.1 Testing and Measuring Systems for Asphalt (with and without modification) 2.2 Testing and Measuring for Asphalt -Aggregate Systems (with and without modification) 2.3 Relationships of Asphalt Chemical and Physical Properties to Asphalt-Aggregate Mix Properties 3.1 Model Development 3.2 Asphalt Performance Studies 3.3. Evaluation Procedures for Prediction Models 4.1 Performance-Based Specifications for Asphalt 4.2 Performance-Based Specifications for AAMAS 5. Coordination Figure 6 Proposed Schedule for Asphalt Research (after SHRP Research Plans (1))