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