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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Optimal Timing of Pavement Preventive Maintenance Treatment Applications. Washington, DC: The National Academies Press. doi: 10.17226/13772.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Optimal Timing of Pavement Preventive Maintenance Treatment Applications. Washington, DC: The National Academies Press. doi: 10.17226/13772.
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Page 6
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Optimal Timing of Pavement Preventive Maintenance Treatment Applications. Washington, DC: The National Academies Press. doi: 10.17226/13772.
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Page 6

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4CHAPTER 1 INTRODUCTION PROBLEM STATEMENT In many state highway organizations recognition of the importance of maintenance and particularly preventive main- tenance is rapidly changing. During the decades of Interstate expansion (from the 1960s through the 1970s), SHAs were organized around construction. By the 1980s, the majority of the Interstate system was constructed and emphasis gradually shifted toward rehabilitation activities. In recent years, how- ever, increased emphasis was placed on pavement preserva- tion and preventive maintenance concepts and programs (1). Many factors contributed to this changing paradigm. Prob- ably the single largest factor was the realization that available funding levels—and doing business in the usual way—did not result in pavements that perform at the level of service demanded by the traveling public. The analyses of perfor- mance data in pavement management systems have helped to prove that point, as agencies could see the impact of allocat- ing the limited available funds to pavement projects on a worst-first basis (i.e., funding and treatments are provided for pavements in the worst condition) (2). The result, in most cases, has been a gradual decline in the number of miles an agency could treat each year and a decrease in the overall condition of the pavement network. The inability to provide an acceptable level of service to the public has been confirmed through public surveys. National studies and statewide surveys have consistently shown a desire for longer lasting, safer roads, with fewer disruptions from continual road work (3, 4, 5). For example, the results from a survey in Arizona have shown that the public would even be willing to pay higher taxes to meet improved levels of maintenance service, and spend more money now to save money on maintenance in the long term (6); public opinion surveys in Washington State revealed similar findings (4). As it has become evident that rehabilitating pavements when they are near failure is not a cost-effective pavement management technique, the need for a better approach to optimize pavement condition and minimize the associated costs was recognized. The concept of “preventive mainte- nance,” which refers to the application of one or more treat- ments to a pavement to retard or delay the development of pavement deterioration, subsequently emerged. There are several difficulties associated with moving away from the worst-first approach used by most highway agencies. In addition to funding and institutional issues, there are the not-so-insignificant problems of determining what treatment to apply to a pavement, when in the life of the pavement to apply this treatment, and what measurable improvement is obtained by the application of this treatment in comparison with other alternatives, including doing nothing. Although all are critical issues, the first step is the acceptance that pre- ventive maintenance is an effective approach in preserving the agency’s pavement investment. When applied to the right pavement at the right time, proper preventive maintenance treatments are a cost-effective means of obtaining the desired life and performance of the pave- ment. Treatments applied too soon add little benefit and treat- ments applied too late are ineffective, failing to prolong the life of the pavement. Considering the annual magnitude of highway investments, the potential savings from following a cost-effective approach to meeting an agency’s performance objectives for pavements are significant. Unfortunately, little guidance is available about timing of the application of pavement maintenance treatments. Agen- cies at both the state and national levels have conducted research on whether preventive maintenance is an appropri- ate pavement preservation strategy; however, the wide range of chosen treatment timings has raised questions about the effectiveness of preventive maintenance. For example, some agencies have applied preventive maintenance treatments at the end of a pavement’s life because funds were not available for the required rehabilitation. Preventive treatments are effec- tive when applied to relatively young pavements in good con- dition. However, the poor performance of treatments applied at inappropriate timings could lead to the erroneous conclu- sion that preventive maintenance does not work. Fortunately, many agencies believe preventive maintenance works and have developed schedules to apply preventive maintenance treatments, although they do not claim to have identified the “optimal” timing for treatment applications. Such examples illustrate the importance of determining the window of time in which preventive maintenance treatments perform as they are intended. This project is based on the premise that preventive main- tenance is effective and there is a “best” time to perform it— an idea that is easy to accept. All pavements begin to deteri- orate as they are exposed to traffic and environmental forces. For bituminous-surfaced (flexible) pavements, this deteri-

5oration occurs in the form of rutting, cracking, loss of surface texture, increased roughness, and other deterioration. In concrete-surfaced (rigid) pavements, the initial deterioration may take the form of cracking, loss of surface texture, increased roughness, and the intrusion of water and incom- pressibles into joints and cracks. The concept of preventive maintenance stipulates that these deterioration modes can be anticipated and at least partially mitigated before they occur, thereby providing the following long-term benefits: • A higher level of service resulting from improved pave- ment performance, reduced user costs, and increased safety; • Delayed need for rehabilitation; and • Life-cycle cost savings OBJECTIVE AND SCOPE OF RESEARCH The objective of this research was to develop a methodol- ogy for determining the optimal timing for the application of preventive maintenance treatments to flexible and rigid pave- ments to realize the greatest increase in performance at the least cost. The methodology was to consider the variety of treatments that are used and the different ways of monitoring pavement performance. It should be useful both to agencies that already have a preventive maintenance program and to those considering the implementation of such a program. This research addresses a gap in preventive maintenance programs that has been recognized by highway agencies. In response to a November 2000 survey of SHAs, 12 respon- dents (out of 34) identified data collection and management and 6 identified improved models and guidance on project selection as the most important needs for their preventive maintenance program (7). The comments provided with the responses pointed out the lack of research that specifically correlates maintenance treatments to the extension of pave- ment life cycle, the lack of information on how often preven- tive maintenance treatments should be applied, the necessity to articulate definite cost savings and benefits, and the reliance on experience for determining appropriate preventive main- tenance treatment timing. RESEARCH APPROACH The project objective was accomplished by completing the following six tasks. Task 1. Collect and review information on the timing, selection, and performance of preventive maintenance treatments of flexible and rigid pavements. Highway agen- cies in North America, South Africa, and New Zealand were queried about their preventive maintenance experiences, par- ticularly as they relate to treatment timing and project selec- tion. Agencies reported that they consider a range of factors in their decision process, including environment, material type, surface thickness, pavement deterioration (type, sever- ity, and extent), past and projected traffic, performance his- tory, maintenance history, treatment costs and available bud- gets, and expected future performance. In some cases, the analysis is performed as part of the agency’s pavement man- agement process. However, there was no apparent rigorous analytical process for timing or selecting preventive main- tenance treatments. A brief summary of the results of this data collection effort is found in Appendix A (not published herein). Task 2. Identify appropriate preventive maintenance treatments for ranges of climatic conditions, traffic lev- els, and pre-treatment pavement conditions. Many factors were found to be important for identifying appropriate pre- ventive maintenance treatments although ultimately the deci- sion is based on “local” factors. General guidance is available on the conditions in which various treatments are appropriate. As described in Chapter 2, this guidance can be adapted by agencies to meet their needs. Task 3. Recommend and describe a methodology that considers the cost-effectiveness and performance of main- tenance treatments. The optimal timing methodology is described in Chapter 3. The process that led to its adoption is described in Appendix B (not published herein). Task 4. Create a user-friendly analysis tool to facilitate use of the methodology for the variety of pavement main- tenance situations encountered by highway agencies. The optimal timing methodology, designated OPTime, is a Visual Basic Application-driven Microsoft® Excel workbook pro- vided on a CD-ROM. OPTime can be used to estimate the optimal time to apply a specific preventive maintenance treatment. Although OPTime does not use a true optimiza- tion strategy (i.e., all possible treatment application times and alternative treatments are not analyzed), it provides a simple analysis method that can be used to choose the most effec- tive treatment timing from a set of user-chosen timing sce- narios (i.e., a preventive maintenance treatment applied at many different user-chosen pavement ages). A User’s Guide, found in Appendix C, http://trb.org/news/blurb_detail.asp?id =4306 offers specific instruction on the use of the tool. Task 5. Demonstrate the applicability of the methodology and the suitability of the implementation tool using data from a limited number of projects or other means. The Ari- zona, Kansas, Michigan, and North Carolina DOTs all pro- vided data and other resources to support the effort to evaluate the methodology using the analysis tool. Since the availability and type of data greatly differed between agencies, the col- lected data were also used to test the flexibility of the analy- sis tool. The results of this effort are discussed in Chapter 3. Task 6. Develop a plan, for use by highway agencies, to col- lect the data needed to support the proposed methodology.

The preventive maintenance optimal timing methodology is based on analyzing an agency’s performance data gathered from applying treatments to pavements at different times. Because many agencies do not have such data, a plan was developed to assist these agencies in establishing test sections and collecting such data. The plan is found in Appendix D. ORGANIZATION OF THE REPORT This report consists of four chapters. This chapter pro- vides the introduction and research approach, describes the 6 problem statement and research objective, and outlines the scope of the study. Chapter 2 describes the findings of the lit- erature search and the preventive maintenance treatments, applicable to bituminous and concrete-surfaced pavements. Chapter 3 describes the methodology recommended for ana- lyzing preventive maintenance data and identifying appro- priate treatments and timing for specific situations. It also demonstrates the applicability of this methodology using data obtained from SHAs. Chapter 4 summarizes the significant conclusions of the project and presents suggestions for future research.

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TRB's National Cooperative Highway Research Program (NCHRP) Report 523: Optimal Timing of Pavement Preventive Maintenance Treatment Applications describes a methodology for determining the optimal timing for the application of preventive maintenance treatments to flexible and rigid pavements. NCHRP Report 523 also presents the methodology in the form of a macro-driven Microsoft Excel Visual Basic Application--designated OPTime.

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