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36 If actual data are not available, or if the user is concerned about the adequacy of specific mathematical relationships Analysis Type Selection (i.e., choosing equation types and coefficients), the simple analysis method is used to compare many "what if" timing Simple Detailed scenarios. Performance relationships are more easily defined by choosing a starting condition level, a condition versus age Selection and Definition of Condition point for the curve to pass through, and the expected exten- Indicators sion of life at the benefit cutoff value. Essentially, the condi- tion indicator versus age relationships are defined visually rather than through a specific mathematical relationship. Selection of Preventive Maintenance Treatment Flexibility in Defining Pavement Performance Definition of Application Ages (Timing Scenarios) Because there is no universal goal for a preventive mainte- nance program, potential users of the optimal timing method- ology may approach the problem in unique manners. The Simplified Definition of "Do- Detailed Definition of "Do- agency may seek improved friction, reduced roughness, better Nothing" Performance Curves Nothing" Performance Curves overall pavement condition, or reduced user delay costs, for example. The analytical tool allows the evaluation of optimal timing in terms of any desired condition or criteria. In addition Simplified Definition of Post PM Detailed Definition of Post PM Treatment Performance Treatment Performance to the typical condition indicators associated with both HMA Relationships Relationships and portland cement concrete (PCC) pavements, two user- definable fields are provided to customize the analysis. The units associated with all condition indicators (both standard Definition of Costs and user definable) are also completely customizable. Cost Type Options Definition of Benefit Ranking Factors Four different cost types may be included in the analysis-- treatment costs, work zone user delay costs, rehabilitation costs, and routine maintenance costs; the user decides which Conduct Analysis of these costs to include in the analysis. This flexibility allows a user to conduct typical, as well as specialized, analysis. A Figure 12. Outline of the data flow through the typical analysis primarily consists of determining an optimal methodology. timing scenario based only on treatment costs. An example of a specialized analysis is one in which the user wants to choose the optimal timing of a treatment while only consid- easily conduct hypothetical "what if" scenarios in the ering user costs (i.e., all the other cost types, including the absence of actual data. cost of the treatment, are ignored). While such an approach Select condition indicators to be included--The meth- would be considered unconventional, the analysis method odology allows the user to select the one or more condi- permits such investigations. tion indicators that will be tracked/predicted over time. The influence of the selected condition indicators' ben- Analysis Setup efit and costs will be estimated to determine optimal preventive maintenance timing. The determination of the optimal timing requires many Define the preventive maintenance treatment to be different inputs during the analysis setup phase. The general analyzed--The methodology requires that the user spec- steps required to setup an analysis are presented in Figure 12. ify a particular preventive maintenance treatment to be Brief descriptions of each step are included below. analyzed. The methodology only analyzes one treatment at a time (i.e., it does not compare preventive mainte- Analysis type selection--OPTime includes a choice of nance treatments). two distinct analysis types. The detailed analysis is pri- Define all timing scenarios that will be investigated-- marily used to analyze actual historical performance The methodology evaluates treatment timings that are data; the simple analysis approach is generally used to specified by the user (i.e., all possible treatment timings