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Local Calibration of the MEPDG Using Pavement Management Systems
Chapter 3. Three State Selection Results
Using the selection criteria and scoring matrix outlined in Chapter 2, the research team individually evaluated and scored all eight state highway agencies, which included Florida, Kansas, Minnesota, Mississippi, New Mexico, North Carolina, Pennsylvania, and Washington (FHWA 2006a; FHWA 2006b). After completing the individual evaluations, the research team discussed the findings and developed an approach to reach consensus on the state rankings. Following is a summary of the resulting scoring deliberations and comments with regard to perceived strengths and weaknesses of the eight states evaluated.
The evaluation of the individual ratings conducted by each research team member began with an in-depth review and discussion of each rater’s interpretation of the exercise to provide some standardization or "calibration" of the rating technique. Interestingly, all three raters judged Mississippi, Minnesota, North Carolina, and Florida to be among the most suitable states in accordance with the accepted criteria. While the rankings of these four states differed among raters, each agreed that the differences in scores between the top four states were not substantial. In other words, all raters found the difference between the highest and the fourth highest scores to be small. Kansas, Washington, New Mexico, and Pennsylvania on the other hand, scored significantly lower than the top four states. A detailed comparison of each rater’s approach revealed that the largest single factor contributing to the lower ratings for these four states was the level of commitment to the implementation of the MEPDG. According to the information provided in the Hudson, et al. report, these four states had incomplete plans for implementing the MEPDG or had no implementation plans at all. Since the relative weight assigned to this evaluation category was the highest of all four included in the criteria, the incomplete plans for implementation had a strong negative impact on the state’s aggregate score. Results of the scores reached by consensus are presented in table 3. Note that the scoring weights assigned to each category to emphasize its relevant importance are included near the top of the table.
Upon reaching consensus with regard to the scores of all eight agencies, the three states with scores that most closely approximate the median score for the entire group were selected for inclusion in this study. This selection approach was developed with the intent of selecting state highway agencies that are representative of typical agencies nationwide rather than state highway agencies that have previously committed excessive resources to calibration activities. However, the pronounced distinction in scores between the top four and bottom four states, which is largely attributed to differences in the levels of commitment to implementation, poses an unanticipated dilemma. That is, those states that are fully committed to implementation will maximize the likelihood of the project’s success. For this reason, the research team recommended that the top four states be considered further for participation in the calibration of the MEPDG models that conducted during this study and that the bottom four states be eliminated from further consideration. However, as the research team moved forward with the selection of a single state to work with, the degree to which the agency’s pavement management data is representative of information found in other states was taken into consideration.
Following are comments pertaining to perceived strengths and weaknesses of the four highest-scoring states highway agencies.
Strengths – Mn/DOT (Department of Transportation) enjoys a mature and highly developed pavement management system. Their plans for implementation are advanced and are being led by the DOT in consort with the University of Minnesota. Their commitment to the effort appears to be very high. Mn/DOT uses digital inspection vehicles to collect distress data annually. They also have detailed, readily accessible construction history information in their Transportation Information System database.
Weaknesses – IT work that would be required to support the calibration effort is judged to be fairly high. Mn/DOT does not yet have experience with traffic spectra data. Records of maintenance work not performed under contract are not available.
Strengths – Mississippi is one of the 14 lead states for implementing the new pavement design guide. The pavement management database is well-developed and contains very detailed information since the database also contains research results. MSDOT has retained the services of a private consultant to advance calibration and implementation on behalf of the DOT. Their approach to implementation is aggressive, and their level of commitment to the effort is judged to be very high.
Weaknesses – Essential data to support calibration (materials, traffic, construction, etc.) is not consistently available at Levels 1 or 2. Many of the input data required in the MEPDG are not yet available in electronic format. Actual pavement layer thickness information is rather scarce. They lack a formal connection between their maintenance operations and their pavement management system.
Strengths – The North Carolina Department of Transportation (NCDOT) has recently enhanced its pavement management system with new software, and they have a contract in place with NC State University to assist with calibration and implementation of the MEPDG. Their pavement management program is well organized, well staffed, and their pavement management system is highly evolved. NCDOT has a fairly comprehensive weigh-in-motion program. Their commitment to the implementation effort appears to be high.
Weaknesses – Essential data to support calibration (materials, traffic, construction, etc.) is not consistently available at Levels 1 or 2. Traffic data are not currently stored in the pavement management system. Maintenance activities are generally not recorded. IT work that would be required to support the calibration effort is judged to be high. The extent of the effort that would be required to acquire additional data for calibration is judged to be fairly high.
Strengths – FDOT is working with the Texas Transportation Institute to advance their MEPDG implementation effort. There appears to be good cooperation between the relevant databases as much of their data is web-based. Their degree of commitment to the effort appears to be fairly high.
Weaknesses – IT work that would be required to support the calibration effort is judged to be very extensive. They do not have an organized deflection testing program. Distress data collection activities are not automated. The amount of the effort that would be required to acquire additional data for calibration is judged to be high.
The selection criteria helped the research team identify four state highway agencies that would each be a viable candidate for demonstrating the calibration procedures that was developed under this project. However, the project scope requires the recommendation of only three state highway agencies; each of which would be visited for further discussion. The research team recommended advancement of this MEPDG local calibration project by including the Mississippi, Minnesota and North Carolina Departments of Transportation for the next phases of work with the intent of selecting one of the three to support eventual calibration.
These three states were recommended because they exhibited the highest levels of commitment to the calibration and implementation efforts, and therefore, they are assumed to be most likely to dedicate the time and resources necessary to successfully complete this project. While none of these state highway agencies has all elements in place to locally calibrate the MEPDG at the highest level, they all have reasonably strong pavement management programs and are actively working to resolve their respective pavement management issues (e.g., data integration, software upgrades, data collection improvements). Importantly, the types of issues that Minnesota, Mississippi, and North Carolina are dealing with are shared by many state DOT’s throughout the pavement management community nationwide.
In keeping with the goal of selecting a representative agency that is likely to generate maximum potential benefits, the manner in which Minnesota, Mississippi, and North Carolina resolve their pavement design and management issues should be of great interest and utility to typical highway agencies nationwide as they move forward with MEPDG implementation using their pavement management tools.