National Academies Press: OpenBook

Optimal Timing of Pavement Preventive Maintenance Treatment Applications (2004)

Chapter: Chapter 4 - Conclusions and Suggested Research

« Previous: Chapter 3 - Research Results
Page 62
Suggested Citation:"Chapter 4 - Conclusions and Suggested Research." 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 62
Page 63
Suggested Citation:"Chapter 4 - Conclusions and Suggested Research." 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 63

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62 CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH Reported highway agency experience and observations of practice show that there is a clear need for guidance on the selection, timing, and measurement of effectiveness of pave- ment preventive maintenance treatments. In many cases, such guidance can be developed from an agency’s available data if preventive maintenance treatments have been used. Other- wise, a significant investment of time and resources will be needed to collect the required data. For agencies interested in implementing or improving preventive maintenance prac- tices, perhaps the single most significant change would come from using preventive treatments at the optimal time. In this project, “optimal timing,” as it relates to preventive maintenance is defined as the time at which the greatest improvement in performance (over doing nothing) is realized at the lowest cost. As suggested by the highway agency exam- ples in Chapter 3, identifying optimal timing requires a sys- tematic approach to preventive maintenance that includes the following actions: • Identify specific objectives of the preventive mainte- nance program. • Select preventive maintenance treatments and define guidelines on their appropriate use. • Define the typical performance of pavements when no treatment is applied (the do-nothing option) as well as the expected performance for different treatments. • Identify and track appropriate measures of performance for different treatments. • Analyze data and calculate the optimal timing for spe- cific preventive maintenance treatments. Each of these actions is discussed in more detail as follows. PREVENTIVE MAINTENANCE PROGRAM OBJECTIVES Program objectives identify what the agency expects to accomplish with a preventive maintenance program and how to impact specific measures of performance. Potential objec- tives could address, for example, deteriorating pavement con- ditions, unsafe surface conditions, and frequent user com- plaints. Appropriate performance measures would include pavement distresses, friction, and roughness or ride. TREATMENT SELECTION Identifying preventive maintenance treatments that can help to accomplish the established objectives is an important step. The characteristics of available treatments should be considered and compared with identified needs or objectives. Information about preventive maintenance treatments pro- vided in Chapter 2 could serve as a starting point. Research, materials, construction, and maintenance staff of SHAs, indus- try representatives, and local contractors can contribute to developing lists of appropriate preventive maintenance treat- ments. Because each treatment provides unique benefits or can be placed subject to different constraints, it is good prac- tice to develop meaningful guidelines on the local or regional use of these treatments, including information on project selection, construction, quality control/quality assurance, and troubleshooting. TREATMENT PERFORMANCE AND DO-NOTHING PAVEMENT PERFORMANCE The performance of a preventive maintenance treatment is measured as the change in pavement performance over the do-nothing condition as measured by performance measures of interest. This performance is predominantly influenced by the condition of the pavement on which the treatment is being applied. To accurately estimate the most cost-effective treat- ment application time, both the current condition of the pave- ment and how that condition changes with the application of preventive maintenance must be known. This knowledge is acquired either by analyzing existing data or by construct- ing and monitoring test sections. A methodology to perform this analysis that considers both changes in performance and the associated costs is described in Chapter 3. To mea- sure the improvement in performance, a do-nothing perfor- mance trend is used to represent how the pavement behaves without any treatment. Do-nothing trends are actually required for each measure of performance that is considered. To esti- mate the optimal timing, performance and cost data that reflect the effects of applying the treatment at different times are analyzed. An agency may already have access to such data, but the lit- erature search and visits to agencies actively using preventive maintenance treatments suggest that only a few agencies either

63 applied preventive maintenance treatments or monitored sub- sequent performance in a manner that generated the needed data. In the absence of such data and if the implementation of an optimal timing approach is desired, test sections must be constructed and monitored over time. Guidelines for construct- ing and monitoring test sections are presented in Appendix D. APPROPRIATE MEASURES OF PERFORMANCE The process of identifying and tracking appropriate mea- sures of performance is a key component of the optimal tim- ing analysis. An appropriate measure is one that reflects the benefit of using the treatment; preferably it relates to the iden- tified program objectives (e.g., if customer satisfaction is a preventive maintenance program objective, then pavement roughness could be used as a performance measure). In mon- itoring treatment performance, it is also important to recog- nize that a treatment can “last” much longer than it provides a benefit. Ultimately treatment performance (or true treat- ment “life”) is determined by the time at which the treated pavement’s performance reverts to the do-nothing condition, or when it reaches a defined threshold. DATA ANALYSIS AND SELECTION OF OPTIMAL TIMING Whether preventive maintenance treatment performance data come from existing databases or test sections, the proper analysis of the data identifies the optimal time to apply such treatments. The optimal timing methodology described in Chapter 3 and Appendix C is incorporated in OPTime. (Appendix C is available to users by accessing the NCHRP website: http://trb.org/news/blurb_detail.asp?id=4306). The output of the analyses is presented in tables and charts to help to understand the findings and identify the sensitivity of the treatment’s performance to different treatment application timings. SUGGESTIONS FOR ADDITIONAL RESEARCH For agencies that intend to implement or improve their preventive maintenance practices, there is a need for research efforts to develop guidance on issues related to optimal tim- ing, including the following: • Relating measured material properties to pavement per- formance—While many agencies focus on conventional distress indicators to identify the optimal time to apply preventive maintenance, other meaningful performance measures that reflect the benefits of applying preventive maintenance might be used. Examples of these measures are asphalt viscosity, surface texture, and pavement mois- ture content or infiltration. • Planning and monitoring test sections—Agencies are strongly encouraged to construct preventive maintenance test sections using treatments of local interest placed at different times to generate optimal timing data; monitor- ing the performance over a long enough time is necessary to generate differences in performance. • Enhancing the optimal timing methodology—When more time-series performance data for pavements receiving preventive maintenance treatments at different times become available either from agency databases or from experimental sections, the optimal timing methodology should be further evaluated and enhanced. • Developing a guide on optimal timing—When sufficient results are available from agencies across the country, a guide could be developed to assist agencies which have neither the performance experience nor the means to construct and monitor test sections to identify optimal timing based on the experiences of others. • Programming a more robust, stand-alone software tool— The tool could expand on the methodology developed in this project to facilitate more comprehensive analy- ses by including the following: – Ability to analyze preventive maintenance strategies (i.e., more than one preventive maintenance treat- ment application) rather than the application of one treatment, – Use of a true optimization method in which all possi- ble treatment strategy timings are analyzed, and – Ability to include multiple treatment types to help esti- mate the most effective treatment type and its associ- ated optimal timing. • Conducting training workshops—Training on the appli- cation of the methodology and the use of the analysis tool will facilitate its use. Such training could be offered on a regional basis or to individual highway agencies. In the latter option, an agency’s pavement performance data could be used to demonstrate the applicability of these data to the optimal timing methodology or the need for other types of data.

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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.

OPTime User’s Guide

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