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3 BACKGROUND In 2008, AASHTO published the Mechanistic-Empirical Pavement Design Guide: A Manual of Practice (MEPDG) and in 2011 released the first version of the accompany- ing software, AASHTOWare Pavement ME DesignTM (for- merly MEPDG v1.100). The MEPDG and AASHTOWare Pavement ME DesignTM software are based on mechanistic- empirical (ME) principles and, as such, are a significant departure from the previous empirically based AASHTO pavement design procedures. Moving from previous empir- ically based to ME-based design procedures provides a number of advantages, including the evaluation of a broader range of vehicle loadings, material properties, and climatic effects; improved characterization of the existing pavement layers; and improved reliability of pavement performance predictions. However, implementation of the MEPDG may require an increase in the amount of time required to develop the design and evaluate the results, an increase in the needed data (e.g., traffic, materials, and calibration and verification to local conditions), and personnel knowledge and expe- rience in ME pavement design procedures. In addition, implementation of the MEPDG may require assistance from agency groups or divisions in the areas of materials, geo- technical, pavement design, pavement management, traffic, and construction. Highway agencies have taken different approaches in the adoption and implementation of the MEPDG, which is not surprising given the complexity of the MEPDG, as well as the unique knowledge, experience, requirements, resources, and policies of each agency. Given the current maturity of the MEPDG and the continuing implementation efforts being made by many highway agencies, it is of interest to document what highway agencies are doing in terms of implementa- tion, what strategies or approaches have worked well, and why some agencies have elected not to adopt the MEPDG at this time. STUDY OBJECTIVE The objective of this synthesis is to document the strat- egies and lessons learned from highway agencies in the implementation of the MEPDG, as well as the reasons why some agencies have not or may not proceed with implementation. METHODOLOGY This synthesis report was prepared using information from a literature review, a survey of highway agencies, three agency case examples, and follow-up questions on highway agency implementation of the MEPDG. A literature search was conducted to review relevant doc- uments, research findings, and agency practices related to the implementation of the MEPDG. The literature search was conducted by accessing the Transportation Research Informa- tion Service (TRIS) database, the TRB Research in Progress (RIP) database, and relevant AASHTO, NCHRP, and FHWA documents. The literature review provided an extensive list of research documents associated with the MEPDG performance prediction models, material and traffic characterization, and climate impacts. In contrast, comparatively few documents are available that summarize the MEPDG implementation practices of highway agencies. An agency questionnaire (Appendix A) was developed that focused on the practices, policies, and procedures that have been successfully used by highway agencies for implement- ing the MEPDG. In addition, the questionnaire requested information related to: ⢠Reasons an agency has postponed or has yet to implement the MEPDG; ⢠Organizational structure and the steps that were required to work within this structure for successful implementation; ⢠Identification of implementation reports and on-going or proposed studies; ⢠Lessons learned that can be used to help other agencies in the implementation process; and ⢠Development of training programs and implementation guides. Questionnaires were distributed (January 2013) to the pavement design engineers of the U.S. state highway agencies, Puerto Rico, District of Columbia, and Canadian provinces and territories. Fifty-seven [48 U.S. (92%) and nine Canadian (69%)] highway transportation agencies provided responses to the agency survey. Responses to the questionnaire have been summarized (Appendix B) and used during the development of this syn- thesis report. chapter one INTRODUCTION
4 REPORT STRUCTURE This synthesis report includes six chapters. This current chap- ter provides the background, objectives, and approaches used in the development of the synthesis. Chapter two presents a brief overview of the MEPDG and the accompanying AASHTOWare Pavement ME Design⢠software; chap- ter three summarizes the findings of the agency survey; chapter four provides a list of common elements of agency implementation plans; chapter five summarizes three agency case examples on the implementation of the MEPDG; and chapter six presents report conclusions.
