Guidelines for Informing Decisionmaking to Affect Pavement Performance Measures: Final Report

CHAPTER 5. Summary, Challenges, and Recommendations

Summary

The objective of these guidelines is to provide information and guidance to highway agencies on the following key pavement decisionmaking issues:

• Method to identify which condition metric is driving the performance measure.
• Temporal effects on performance measures.
• Effects of M&R treatments on performance measures.

The goal of the guidelines was to show agencies what needs to happen to move the overall condition from poor to fair to good. In meeting this goal, the guidelines will enable highway agencies to address critical questions, such as the following:

• What are the drivers of the performance measures?
• What are the effects of M&R treatments on condition metrics and overall condition?
• How can performance measures be improved from poor to fair, poor to good, and fair to good?

These guidelines have presented step-by-step approaches for the following:

• Developing performance measure drivers.
• Calculating the effects of M&R treatments.
• Combining the above findings to develop a list of M&R treatments that affect the condition.

Examples illustrating each of the above approaches were provided. These examples addressed all three pavement types—AC, JPCC, and CRCP. The guidelines also introduced important issues that should be considered by highway agencies, including measurement errors and temporal changes.

The examples and calculations presented were based on data from the LTPP dataset and developed for the purpose of the research study that led to these guidelines.⁽⁴⁾ The LTPP database is available through LTPP InfoPave™ (https://infopave.fhwa.dot.gov/). These guidelines present examples that represent a starting point for agencies that could be used as default input if needed. However, agencies are encouraged to follow the processes in the guidelines using their own data to draw more representative conclusions for their agency. Once an agency has completed the steps presented in these guidelines, the next logical step to consider is to integrate the findings within the agency’s PMS.

Challenges and Recommendations

An important consideration is the challenges agencies may face when integrating the performance measures within their practices. This section presents some of these challenges.

• Different data sources. The performance measures to assess pavement condition are to be based on HPMS data. Although State DOTs are required to submit HPMS data annually, the HPMS data submittal does not always match the data that an agency maintains in its PMS. In addition, the pavement segments in an agency’s PMS are also likely different from that of the HPMS submittal. This presents a challenge, as agencies could potentially be faced with managing targets and goals based on two different datasets. If agencies integrate the performance measures into their PMS for monitoring and consideration, there could be differences from those reported to FHWA using the HPMS data due to the different data source. It is not known at this time the potential difference this may cause, but agencies need to be aware of the possible challenge. It is recommended that agencies assess whether they will face this challenge. If there are differences between the data sources, an agency should evaluate the potential effects and develop a plan to mitigate these effects. In addition, the Final Rule requires that the pavement condition metrics be collected annually for the full extent of the IHS and biennially for non-interstate NHS pavements.⁽³⁾ Agencies may not currently be collecting PMS data at this frequency, which may also cause a difference in the performance measures determined using PMS data and HPMS data. This is another aspect that agencies will need to consider and reconcile between the HPMS and PMS datasets.
  
  
• Change in optimization goals. Agencies have various optimization goals for their PMS and treatment selection. For example, the objective of treatment selection for an agency may be to minimize agency cost while simultaneously maximizing the extension to pavement life. Agencies may have secondary goals or rules used in their optimization such as meeting friction thresholds for safety. Agencies should now also consider how to incorporate the performance measures within their optimization and how they plan to meet the targets. Agencies will need to decide the best method for accomplishing this. Some examples include the following:
  
  
  • Adjusting their optimization objective function to meet the performance measure targets.
    
    
  • Adding a secondary goal or rule to follow during optimization that considers the performance measure targets.
    
    
  • Adding a check of how the optimization recommendations affect the performance measures.

  Agencies will need to decide how the performance measures will affect their decisionmaking process. As a minimum, it is recommended that agencies consider how PMS outcomes (i.e., recommended M&R and project prioritization) affect the performance measures and determine whether the performance measures should be incorporated into the decisionmaking process.

• Updating models within the PMS to consider the performance measures. A key component of the PMS are the predictive models for the effect of various types of treatments and deterioration models. The data in these guidelines have shown that factors that affect treatment effectiveness include metric groupings and metric conditions. In order for agencies to incorporate the performance measures within the decisionmaking process, models used within the PMS would need to be updated or developed based on the performance measures and these factors to predict the effect of treatments on the performance measures. Advanced systems may be able to incorporate the performance measures within the forecasting models to predict the effects of delaying treatment changes in metric condition combination and effectiveness of treatments at different times. Work in this area has recently been or is currently being done under the National Cooperative Highway Research Program (NCHRP) Project 14-33, “Pavement Performance Measures That Consider the Contributions of Preservations Treatments,” and Project 14-38, “Guide for Timing of Asphalt-Surface Pavements Preservation,” which could be a good resource for addressing the challenge in question.^(6,7) The former project was completed in the spring of 2017 and will be published as NCHRP Report No. 858, Quantifying the Effects of Preservation Treatments on Pavement Performance, while the latter project should be completed by the summer of 2018.

Agencies are required to meet the performance measures or face loss of flexibility for spending National Highway Performance Program funds until the minimum required condition levels are exceeded. Therefore, it is critical that agencies understand what metrics drive the performance measures and how performance measures are affected by M&R treatments and, based on that information, determine how the performance measures will be incorporated into their decisionmaking process. As a minimum, it is recommended that agencies add the performance measures to the output of the PMS and treatment selection optimization to monitor the values of the performance measures. It is also recommended that agencies perform similar analyses as those described in these guidelines and develop a list of potential M&R treatments that affect the performance measures or a treatment matrix. Furthermore, and to the extent possible, it is recommended that agencies incorporate these suggestions based on a long-term view of the overall health of their networks.