About the research
The Mechanistic-Empirical Pavement Design Guide (MEPDG) and its accompanying software AASHTOWare Pavement ME Design (PMED) represent major improvements over their predecessors, particularly in their comprehensive coverage of the impact of design inputs on pavement performance.
Since PMED’s release, numerous updates have been made to the software. Some of the most recent enhancements include the addition of Modern Era Retrospective Analysis for Research and Applications (MERRA) climate data (satellite-based data provided by NASA), a reflective cracking model for overlay performance prediction, and a tool to design bonded concrete overlays on asphalt (BCOA), renamed in PMED as short-jointed plain concrete pavement (SJPCP) over asphalt concrete (AC).
A comprehensive evaluation of all the new PMED tools was performed and is presented in this study. The results demonstrate that these updates’ significant impact on the distresses predicted by the software compared to predictions using previous versions warrants recalibration. Evaluation of PMED’s nationally calibrated models was performed for flexible, rigid, and asphalt concrete over jointed plain concrete pavements for different representative geographical locations, ages, and traffic levels across Iowa. Locally calibrated models were developed for Iowa-specific conditions by determining an appropriate new set of calibration coefficients for use in the PMED software. During this process, multiple advanced optimization approaches were tested, and experiences and recommendations from the entire local calibration process are discussed. Additional analysis was performed to determine recommended layer thicknesses for varying reliability levels using the locally calibrated models.
The overall findings from this study will serve as a useful reference and guide for implementing PMED for Iowa pavement design practices. Other states that plan to test and implement PMED for their state design practices will also benefit from this study’s complete description of the set of local calibration steps required by PMED.