Calibration of the MEPDG Transfer Functions in Georgia

The Georgia Department of Transportation (GDOT) currently uses the empirical 1972 American Association of State Highway and Transportation Officials (AASHTO) Interim Guide for Design of Pavement Structures as their standard pavement design procedure. However, GDOT plans to transition to the Mechanistic Empirical Pavement Design Guide (MEPDG) for designing new and rehabilitated highway pavements. As a part of the transitioning process, GDOT has sponsored an implementation project. One part of the implementation project is to verify the MEPDG global distress transfer functions and calibrate these functions to local conditions, if determined to be necessary. The Georgia Long-Term Pavement Performance (LTPP) and non-LTPP roadway segments were used for this verification-calibration process. As noted above, one objective of the implementation project was to verify or confirm that the MEPDG transfer functions and global calibration coefficients derived from National Cooperative Highway Research Program (NCHRP) project 1-40D reasonably predict distresses and smoothness in Georgia. The Task 2 interim report focused on using the Georgia LTPP test sections to confirm the applicability of the global calibration coefficients. The Task 2 interim report concluded some of the transfer functions exhibited significant bias between the measured and predicted distress and require local calibration. This report documents the local calibration of the transfer functions using LTPP and non-LTPP roadway segments. The calibration process follows the procedure presented in the 2010 AASHTO MEPDG Local Calibration Guide. Local calibration coefficients were derived to remove that bias for the rutting, fatigue cracking, and thermal cracking transfer functions of flexible pavements, and the faulting and fatigue cracking transfer functions of rigid pavements. The global coefficients of the smoothness degradation regression equation for flexible and rigid pavements were also checked for their applicability to Georgia conditions.