BACKGROUND: The AASHTOWare Pavement ME Design (formerly DARWin-ME) and the AASHTO Mechanistic-Empirical Pavement Design Guide Manual of Practice (MEPDG) provide a methodology for the analysis and performance prediction of pavements and overlays. Although the performance of flexible and rigid pavements is known to be closely related to properties of the subgrade and underlying layers (i.e., base and/or subbase), some recent research studies indicated that the performance predicted by this methodology shows a low sensitivity to the properties of underlying layers and does not always reflect the extent of the anticipated effect. There is a need to evaluate the procedures contained in the Pavement ME Design and identify or develop enhancements to ensure that the procedures appropriately account for the influence of subgrade and unbound layers on the performance of flexible and rigid pavements. These enhancements could be incorporated into the Pavement ME Design procedures to allow an improved analysis and design of flexible and rigid pavements.

OBJECTIVE: The objective of this research is to propose enhancements, as needed, to the Pavement ME Design procedures to better reflect the influence of subgrade and unbound layers (properties and thicknesses) on the performance of flexible and rigid pavements. These enhancements may include modifications of the models contained in the Pavement ME Design and/or the development of new models. The research shall address all types of flexible and rigid pavements included in Pavement ME Design.

STATUS: The research is complete. The contractor's final report is available as NCHRP Web-Only Document 264; link below.