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38 Performance Measures Implementation This project identified pavement performance measures that consider the effects of preser- vation treatments on performance, service life, and LCC, and developed a guide document to facilitate use of these measures. Findings and observations made based on the work performed are summarized. Individual distress, composite indexes, and cost-based measures were identified to evaluate the effectiveness of preservation treatments. These included individual distresses (roughness, cracking, and rutting for asphalt pavements and roughness, cracking, and faulting for concrete pavements) and many composite indexes supplied by agencies. A framework for using perfor- mance measures to evaluate the effects of preservation treatments was identified, validated, and tested using both LTPP data and data provided by state highway agencies. It was found that: ⢠Individual pavement condition measures are capable of capturing the effects of preservation treatments on pavement performance. ⢠Composite index measures capture the immediate effect of preservation, but did not sup- port the development of models for capturing long-term changes in performance. Because composite indexes are composed of many distresses, and each distress is affected differently by preservation, most composite indexes are not expected to capture these changes in perfor- mance. However, because composite indexes may capture effects of preservation in some cases, they should be evaluated on a case-by-case basis. ⢠The data required to support the use of performance measures does exist, but often in several sources (e.g., highway agencies, LTTP database, and literature). The use of performance measures that capture the effect of preservation can enhance the state of practice of pavement management. Because performance measures are integral to several decision processes within pavement management (e.g., treatment selection or project prioritization), measures that adequately capture these effects were recommended as part of this research. The guide includes recommended performance measures and the process for using these mea- sures to assess the effects of preservation treatments on pavement performance, and hence service life and LCC. The guide also provides a step-by-step procedure to identify alternate pavement performance measures in assessing the effects and use of preservation treatments on pavement performance. The guide provides a process for selecting performance measures, developing models, and implementing the measure or models into the agency decision process. However, this process can be improved by: C H A P T E R 5 Summary, Conclusions and Recommendations for Future Research
Summary, Conclusions and Recommendations for Future Research 39 ⢠Continually improving data availability and quality. ⢠Improving the models used for estimating both the initial condition jump and long-term effect on performance. ⢠Improving the process for using the measures in the decision processes. Recommendations for Future Research The following recommendations for future research were developed as a result of this project: ⢠A study of the different types and sources of variability in network-level pavement condition measurements to provide guidance on how to identify and account for each type of error in statistical analyses. Each of the performance measures evaluated in this project was signifi- cantly affected by measurement errors, and a better understanding of these errors will lead to more robust performance measures. ⢠An effort to standardize cracking, rutting, and faulting measurement procedures to facilitate the sharing and comparison of data between various agencies. ⢠Studies to demonstrate the calculation of the condition jump and changes in performance for a wide range of treatments, possibly considering other performance measures (e.g., friction). ⢠A study to develop guidance on how the performance measures recommended in this research could be implemented into a broader performance management framework. ⢠A study to develop a methodology using the findings of this research for determining the best time to apply specific preservation treatments on a given pavement.
