Calibration of Flexible Pavement in Mechanistic–Empirical Pavement Design Guide for Washington State

The Mechanistic–Empirical Pavement Design Guide (MEPDG) is proposed as an advanced pavement design tool that integrates up-to-date pavement practices. Since MEPDG was released in 2004, the Washington State Department of Transportation (WSDOT) has continuously worked on calibrating and evaluating the program with regard to implementation for state and local agencies. This paper presents WSDOT's latest efforts on calibrating the flexible pavement portion of MEPDG with data obtained from the Washington State Pavement Management System. It describes preparation of required input data and provides detailed descriptions of input values, as they may apply to states with similar conditions. The calibration process is described, and results and potential implications are discussed. Major observations and general issues encountered in the calibration process are emphasized. An implementation plan is being prepared that may replace the 1993 AASHTO Design Guide with MEPDG in Washington State. This study provides valuable conclusions for national applications: ( a) the flexible pavement distress models were calibrated successfully, ( b) WSDOT flexible pavements require local calibration different from the defaults, and ( c) a software bug does not allow calibration of the roughness model. By making a few improvements and resolving software bugs, MEPDG software can be used as an advanced tool to design flexible pavements and predict future pavement performance.