|FHWA > Engineering > Pavements > HIF-11-026 > Chapter 4. Single State Selection|
Local Calibration of the MEPDG Using Pavement Management Systems
Chapter 4. Single State Selection
In preparing for discussions with the three States (Mississippi, North Carolina, and Minnesota), the project staff sought to confirm the information used during the initial evaluation of the eight States. It was readily recognized that the study done by Hudson et al. was conducted in 2006, and in the two years since that study many things may have changed. For example, several States have been actively involved in evaluation and implementation studies for the MEPDG. The research team sought to explore the current status of work underway in the State as pertaining to the MEPDG implementation, the availability of information in the pavement management database to support the calibration efforts, and the potential level of support that may exist for testing a proposed framework for the use of available State data in calibrating the MEPDG. Specifically, the following factors were considered:
The meetings in each of the three States were informal, and were completed in about one and a half business days. The format generally included meeting with all interested personnel to introduce the research effort and the people involved. State agency representatives were asked to discuss, in general terms, the status of their MEPDG implementation efforts. Any university studies that may have been conducted, or are currently under way were discussed, to gain an understanding of the objectives, results, and current status of the work. Discussions were held with representatives of Design, Traffic, and Materials to understand the status of implementation preparedness in each of these areas. Discussions were held with representatives of the Pavement Management group, to assess the availability and format of required data, and the level of effort generally required to access this information.
The likelihood of success with the implementation was primarily gauged by the enthusiasm the State exhibited for the effort, and the existence of a plan for continuation of the effort. Project staff listened for indications of support by upper management, and where necessary queried meeting participants as to the degree of support they received for their efforts.
Following are observations and comments from the meetings with the three State highway agencies.
Meetings were held with the Minnesota Department of Transportation (Mn/DOT) on Sept, 2008. State participants in the meeting included Mr. David Janisch (Pavement Management), Jerry Geib (Pavement Design), Matt Oman (Traffic), and Curt Turgeon (Pavement Engineer). On Day 2 we were joined by Ms. Maureen Jensen, who had worked extensively in the evaluation and implementation of the MEPDG prior to moving to another area in the Department.
Discussions generally confirmed the advantages and disadvantages observed from the earlier work. While Mn/DOT was highly committed to the effort previously, they exhausted their implementation budget while finding a number of apparent problems in the software, and at this point are waiting to take further action once the software is in a more stable position. While the Department continues to collect a great deal of distress and roughness data, the format of the data is not consistent with MEPDG predictions, meaning that the effort required to do meaningful comparisons would be fairly high. While there have been increases in the amount of traffic data collected, staffing shortages have prevented the management and manipulation of data needed to produce the required load spectra information or truck weight road groups.
In general, Mn/DOT feels it has a design process in place that provides an acceptable result, with expected life and actual life in close agreement. As a result there is a lack of justification for making a major change. At this point the cost would be great, with little perceived benefit.
Much of the Mn/DOT implementation work was done in concert with Dr. Lev Kazanovich and the University of Minnesota. An attempt was made to meet with Dr. Kazanovich, but unfortunately he was out of the country during the time of our visit.
Meetings were held with the Mississippi Department of Transportation (MSDOT) on October 20-21, 2008. State participants in the meetings included Mr. Bill Barstis (Research), Ms. Cindy Drake (Pavement Management), Mr. Jeff Wages (Construction and Materials), and Mr. Trung Trinh (Traffic). Mr. Roger McWilliams of the Division FHWA office also joined us during the meetings. Discussions with Mississippi DOT personnel confirmed the previous findings, and indicated a great deal of advancement in some areas of implementation readiness in the intervening time period. MSDOT sponsored a series of twelve "support studies" as part of their implementation efforts. About half of these involved materials characterizations, which are nearly complete for typical materials used in the State. In these areas they are building libraries of typical material properties for design use.
The State pavement management system is well populated with time series performance monitoring data, and much of that is in the proper format for comparison with MEPDG predictions. Unfortunately the disadvantages previously noted, including a direct link between sections in the pavement management system and material properties still exist, and Mr. Wages reported a great deal of time and effort have gone into locating construction records and obtaining material properties needed from those records. Therefore, it is still believed that the levels of effort necessary to gather required information will be relatively high. It appears that this may be a fairly common characteristic among most State highway agencies.
One thing that impressed the research team during the meetings with MSDOT was the motivation obvious in the implementation support, and the eagerness to meet and work with the team. Mr. Bill Barstis and Ms. Cindy Drake both expressed a desire to participate in the development of the framework, as they felt it would benefit their, and other, implementation efforts. Mr. Barstis indicated that management had generally been very supportive of the efforts thus far, and he felt that they would continue to be supportive as long as forward progress was being made.
In discussing traffic inputs, the research team found that Mississippi DOT is collecting a great deal of traffic data, and had adequate data management facilities in place. However, they had not begun the process of establishing Truck Weight Road Groups or Truck Traffic Classifications yet. References were provided for States that had done this work, in hopes that they could help Mr. Trinh in developing an approach to complete this effort.
North Carolina Department of Transportation
Meetings were held with the NCDOT on October 28-29, 2008. State participants at the initial meeting were Ms. Judith Corley-Lay and Mr. Neil Mastin. The research team had an opportunity to visit with Mr. Clark Morrison (Pavement Design), Mr. Kent Taylor (Traffic), and Mr. Jack Cowsert (Materials) at a later time. Mr. Jim Phelps of the North Carolina FHWA Division office joined us for all of the discussions. The research team learned that NCDOT has a number of support projects under way, generally through Dr. Richard Kim at North Carolina State University. Projects are under way to develop Dynamic Modulus values for typical NCDOT asphalt mixtures, to investigate traffic data status and needs, and to look at statewide calibration needs. All of these projects indicate a fairly high degree of continued interest in the implementation of the MEPDG. Of specific interest was the statewide calibration study, begun in 2007 and scheduled to be completed in August 2009. This study specifically sought to use pavement management and other data for calibration, and found that many estimations and correlations had to be used due to lack of sufficient information.
One important lesson learned during the meetings was that most of the data stored in the NCDOT pavement management database is referenced by County Route and milepoint, meaning that location referencing may be extremely difficult. This may make information location and retrieval nearly impossible, even before the format inconsistencies are considered. Distress data are not stored in a manner consistent with MEPDG predictions, meaning that it will be very difficult to directly relate the two. Still, NCDOT has completed some studies looking at existing roads and MEPDG predictions, and found that performance predictions are poor. They hope that national studies and model improvements as a part of NCHRP 1-40 studies will improve predictive capabilities.
Discussions revealed that while there have been advancements in the area of material characterization, and a study is under way with Dr. Kim on State calibration, it will be difficult to use available information given the current location referencing method and data format. Still, NCDOT remains committed to the effort, and seems genuinely eager to assist if possible.
The project staff very much appreciated the willingness of DOT staff in all three States to sit and discuss their efforts with the research team. All three of the States exhibited a great deal of interest in the success of this effort. It was clearly obvious that all three States had been deeply involved in the implementation activities for some time, and were well aware of the input needs, and difficulties in developing some of the requirements.
The research team learned something different from each of the State discussions because each of them offered a different perspective on the same problem. Based on our assessment, the NCDOT was recommended and accepted for participation in this study. The NCDOT recommendation was based on the following:
There are several challenges that need to be addressed to successfully test the proposed framework. The challenges identified by the team, and proposed strategies for addressing these challenges, are provided below: