Quantifying the Effects of Preservation Treatments on Pavement Performance (2018)

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34 Overview The information provided in Chapter 3 has demonstrated the appropriateness of recom- mended performance measures. Developing a guide on these measures will facilitate imple- mentation and help highway agencies assess the effects of preservation treatments on pavement performance, service life, and LCC. This information will support the pavement management decision-making process and allow highway agencies to address critical questions such as: • Does application of preservation treatments contribute to improved pavement performance of segments of the network and/or of the overall network? • How does application of preservation treatments affect the life of a given pavement segment, and how does this contribute to the overall serviceability of a pavement network? Do these treatments contribute to delaying application of more costly rehabilitation treatments by maintaining the level of service above a threshold value that triggers rehabilitation thereby? • Is application of preservation at a given point in time and/or given pavement condition cost effective and do they contribute to lower LCC for the network? Answers to these questions will help highway agencies better assess the effects of preservation treatments and their role in maintaining the level of service of the pavement network and con- sider their contributions to pavement performance and service life when developing treatment strategies for networks of pavements. Also, incorporating these measures into PMS and/or other agency tools will provide a means for selecting the right preservation treatment and applying it at the right time, therefore better optimizing the allocation of resources. The guide developed in this project builds on the information and findings presented in this report, including: • Information gathered during the literature review and from the survey questionnaire and follow-up telephone interviews. • Findings from the testing and validation of performance measures using data provided by DOTs and data from the LTPP database. • Detailed information provided by several state highway agencies (Georgia, Idaho, Maryland, Ohio, Texas, Utah, Virginia, and Washington). The development of the guidelines began with the formulation of case studies in order to identify the aspects of the implementation that should be covered in the guide. The case studies helped show the importance of data variability and the need for thorough data analyses. The guide consists of the following chapters: 1. Introduction – provides background information, guide objective, overview of performance measures and the implementation process, and organization of the guide. C H A P T E R 4 Guide Development

Guide Development 35 2. Performance Measures – details how performance measures can be used to assess the effects of preservation treatments in support of management decision-making processes. The chap- ter also includes criteria for selecting performance measures, the recommended performance measures, and the steps required to implement alternate performance measures. 3. Data Requirements – summarizes the data requirements for using the performance measures. The chapter also includes minimum and desirable data requirements, guidance on how to obtain those data, and resolve data issues (e.g., quality and completeness). 4. Implementation Process – provides a step-by-step procedure for estimating the effect of pres- ervation treatments on pavement performance, service life, and LCC, and to integrate those effects into the existing processes in support of pavement decision-making. 5. Summary – provides a summary of the procedures discussed in the guide and notes on the importance of data quality and its influence on decisions. The guide also includes a list of cited references and an appendix of example case studies that demonstrate how to define the effects of preservation treatments on the initial and long-term condition of pavements, and how to implement performance measures within highway agen- cies’ processes. Implementation Process The approach for implementing the performance measures by highway agencies to assess the effect of preservation treatments on pavement performance, and hence service life and LCC, requires the following three steps: 1. Selecting the recommended pavement performance measures or other performance mea- sures to quantify the effects of preservation treatments. 2. Assessing the effects of preservation treatments on pavement performance using the selected measures. 3. Incorporating pavement performance measures into highway agency’s PMS and/or other processes. A flowchart summarizing this approach is shown in Figure 24. The guide provides a step-by- step procedure for developing pavement preservation effects models and implementing them into a highway agencies’ pavement management practices. Data Requirements The findings of the testing and validation effort discussed in Chapter 4 highlighted the need for addressing minimum data requirements and other desirable data for refining or stratifica- tion. The guide details the minimum data requirements for estimating the immediate condition jump and long-term performance of pavement performance measures for each preservation treatment. These data include: • For each pavement segment, pavement condition data or other information needed to define performance measure immediately prior to and immediately after application of treatment. • For each pavement segment, pavement condition data over time or other information needed to define performance measure after application of treatment. • Data to support at least one method that can be used to assess the performance of preserved segment relative to a non-preserved control segment (or a control segment with similar char- acteristics as the preserved segments, but to which no preservation treatment has been applied). Other desirable data for refinement or stratification of immediate condition jump and long- term performance of pavement performance measures include: traffic data (volumes and load

36 Quantifying the Effects of Preservation Treatments on Pavement Performance Figure 24. General approach to implementation of pavement preservation performance measures.

Guide Development 37 spectra, ESALs, etc.), pavement structure data (layer types and thicknesses, material properties, construction history, construction quality, etc.), subgrade soil (material type and properties, depth to bedrock, etc.), and environmental conditions (ambient and subsurface moisture and temperature, conditions during construction, etc.). The guide discusses what can be done if these data are not available and how to obtain the data required for implementation of pavement performance measures. Another important step for implementation is resolving data issues. The guide suggests that high- way agencies should assess the quality and completeness of available data and provides guidance on how to determine whether available data is of sufficient quality to inform the required steps in the guide. The guide notes the effect of data quality on the pavement performance measures, discusses data quality needs, and presents a procedure to improve data quality. Implementation of Performance Measures The guide discusses the process for implementing the performance measures and provides guidance on how to use these measures to assess the effectiveness of preservation. The imple- mentation process covers: • Approach to calculating the changes in both condition and performance following preservation. • Use of measures to assess the effectiveness of preservation. • Other considerations (e.g., enhancements of data and models). The steps for calculating the initial change in condition resulting from the application of a preservation treatment include: 1. Identifying the condition measurements just prior to and immediately following the applica- tion of preservation for several sites. 2. Calculating the difference between two data points for each site to check if the change in pave- ment condition reflects a positive value. 3. Performing a regression by which the independent variable is the condition before the applica- tion of preservation, and the dependent variable is the calculated difference. Other independent variables should be considered if data are available. The steps for evaluating changes in performance resulting from the application of a preserva- tion treatment include: 1. Identifying the condition measurements over time that describe the performance following the application of a preservation treatment. 2. Calculating the rate of deterioration or expected performance for the treatment and control segments. 3. Comparing the performance of the treatment to that of control segments in absolute or rela- tive terms. Implementation of the performance measures helps assess the effectiveness of pavement pres- ervation and determine whether the application of preservation treatments influences perfor- mance, service life, and LCC of a given pavement, or the overall pavement network. The guide presents approaches for estimating these influences. Implementation of the performance mea- sures also can be used to support pavement management decision-making. The guide concludes with a summary and other considerations to facilitate implementation, such as periodic training for personnel responsible for performance assessment and decision support systems.