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Use of PMS Data for Performance Monitoring with Superpave as an Example
1. Executive Summary
The objective of this project was to examine how existing pavement management data and materials related data in various state DOTs can be used to evaluate the performance of new materials and concepts and to validate new design methods. In particular, Superpave is used as an ideal example and is carefully examined. This study is not big enough or long enough to evaluate or validate Superpave per se. Rather we examine the process and obtain consensus on what data states would need to collect to adequately evaluate Superpave. Similar studies could be done for any other new design or materials concept such as the 2002 Pavement Design Guide. No evaluation or judgment is made about Superpave, rather the concepts and details of using pavement management and related data are clearly illustrated.
A second objective of the study is to determine what PMS data and other related data and factors the state DOTs collect on a common basis, which could be combined and used for multi-state data analysis. A third objective is to determine what can be done to make data from several state DOTs compatible and usable to others to the point that a common analysis could be made for the broader benefit of all state DOTs and thus the Federal Highway Administration.
The project team assembled to undertake this effort at the request of the FHWA provided the three components critical to the success of the project (i.e. knowledge of pavement management, Superpave materials, and state and AASHTO interaction).
FHWA and the team visited DOTs in Maryland, Indiana, Florida, Arizona and, at a later stage, Washington to discuss the aspects of their active pavement management system and the status of their use and record keeping for Superpave materials.
Very productive meetings were held in all states to cover introductions, outlining the aims and objectives of the project, and general discussions on the DOT organization. Details covered included pavement management systems, data collection methods and monitoring network pavement performance in each state. The main emphasis was on pavement evaluation, Superpave projects, actually constructed, and the requirements for linking materials and construction data with performance data in the PMS database.
One of the main challenges discovered in all the states visited is the absence of a convenient link between essential data on materials characteristics used in each project on the one hand and PMS data including performance data on the other. This is most often caused by the fact that the first group of data (information on design, testing, in-place properties, thickness, and QA data) is commonly stored in flat files, difficult to access and sometimes incomplete. Thus it became clear early in the project that a valid analysis of the performance of Superpave, or any other material or technique for that matter, can only be done when relevant data is available in electronic format. Performance data can only be linked to materials and construction data when use is made of a common locator reference.
The results of phase 1 of the study were presented and discussed during a project review meeting with the FHWA; at that meeting a phase 2 was added to test the concepts with a Pathfinder Study with the Maryland SHA. This additional study served as an example of how a DOT can identify and collect required data on Superpave and how much effort is needed to enter these into one or more electronic databases. As a next step these databases were loaded into a suitable "vehicle" for storage, inspection, linking, analysis and reporting purposes. In this example the "vehicle" used was a web-based system recently developed by the University of Washington.
This report describes the project, and after an introduction covers the following relevant topics:
The report ends with conclusions, findings and recommendations, which are summarized here for executive review
The project results show that it is possible for state DOTs to assemble a database that can be used to evaluate the performance of Superpave and other design- and new materials concepts. The project was not large or long enough to make a thorough evaluation, but it did determine the feasibility of the concept and its applicability among five states.
The many details and variables involved in a new methodology such as Superpave also requires recording data on design, construction, and performance for individual projects in addition to the ordinary PMS data. These details may extend normal pavement management activities in some states, but the results are well worth the effort. As the data are collected over five to ten years, results and updates of performance comparisons will provide substantial benefits and validation of the method. Each year the analysis of the growing database will produce definite results.
The key to linking databases for performance, materials and construction is to have precise and common location identification and date/time information. Only in this way can it be assured that the data are comparable. For example, in the case of multi-lane roadways involving bi-directional interstate highway lanes and frontage roads, the new material may be used in only one or two lanes or in one roadway direction. When the material is first placed, it is clear in everyone's memory, which is which, but four or five years later or after personal changes, when a long-term analysis is needed, this becomes more difficult. Unambiguous locations can be provided by GPS measurements and these are relatively economical and easy to use at the present time. However, they must be tied to traditional location identification information such as project number, mile point, lane, direction, date, etc.
In Washington State the University of Washington (UW) has, in close collaboration with the DOT, developed an approach which stores all relevant data for Superpave contracts on a web-based system. The performance, design and construction data can be organized, downloaded and analyzed with the method. This new development was possible because most of the relevant data on materials and construction in WSDOT were available in electronic format (mostly Excel files), and in addition a major effort was made by UW to link these data to performance measurements from the PMS. This system was modified successfully to store, inspect, analyze and report relationships of Superpave data supplied by Maryland as part of the Pathfinder study.
A major advantage of the website approach is that all data are available to all users as soon as data are entered. With proper equipment for electronic data entry, used in the field, it is possible to monitor construction projects quickly with "real time" QC/QA data which could be beneficial.
The Pathfinder study has shown that the collection of relevant data in materials and construction files, required for linking with performance data, is cumbersome and time consuming. In Maryland it took two man-months to collect data for 7 Superpave projects, and even then not all required data could be obtained.
Ideally all relevant data should be generated in electronic format from the start, but there is also a need for a proper and unbiased definition of required data before they can be used in a linking exercise.
The review of information and data, as well as interaction with five state DOTs visited, suggests that with manpower for data entry it is possible for a state DOT to develop a Superpave evaluation database. More than $100 million has been expended to date to develop the Superpave concept, yet no actual performance results exist. It is now essential to compare real Superpave performance to current asphalt practice in state DOTs to validate the value of Superpave. Each state can use pavement management and related data to evaluate Superpave, but it will be faster and more definitive if several states can work together to set up databases with the required data and combine their efforts to make the necessary performance evaluations. A group of 5 to 20 states with coordination among states can produce a large analysis joint database of lasting value.
Preparation of a good work plan for evaluating new concepts using PMS data and such tools as standard Pavement Evaluation Protocols will be useful for state DOTs to encourage them to set-up appropriate evaluation databases and procedures for any new pavement concept they undertake. Similar methods are applicable in many state DOTs.
The approach examined in this project for Superpave is applicable for other new concepts. Specifically, now is an ideal time to set up a plan showing how several state DOTs can record the proper data to evaluate the new 2002 Pavement Design Guide when it is adopted by AASHTO. It is important to define this plan before the new method goes into effect.
The authors gratefully acknowledge the funding and support of the FHWA, especially the contract representatives Ms. Sonya Hill and Mr. Frank Botelho.
The TRDI contract for this project was administered through Battelle in Columbus, Ohio, acting as the prime for FHWA. We would like to thank Ms. Tami Hannahs and Mr. W. Scott Versluis of Battelle for their interest and support.
We are very grateful for the help from the five state DOTs that participated in the study: Maryland, Florida, Indiana, Arizona and Washington State. The DOT and FHWA representatives of those states were very kind to meet with us individually, to share their knowledge of and experience with PMS and Superpave, and to send us data that we needed for this study.
For the pathfinder study special thanks are due to Messrs. Sam Miller, Larry Michael, Pete Stephanos and several co-workers of Maryland SHA for collecting and formatting the required data, and to Dr. Joe Mahoney and George White of the Civil and Environmental Engineering Department of the University of Washington for making their newly developed web-based system available and for modifying it to accommodate the data from Maryland SHA for the benefit of this study.
The TRDI Project Team included Dr. W. Ronald Hudson, Project leader (pavement management), Prof. Carl L. Monismith (Superpave), Dr. Charles E. Dougan (States/AASHTO), and W. (Pim) Visser, Project Engineer/Coordinator.