Comparisons of Flexible Pavement Designs

Abstract

Flexible pavement designs and performance predictions derived from the empirical 1993 AASHTO pavement design methodology and the mechanistic–empirical NCHRP Project 1–37A approach are compared for a range of locations within the United States, each with its own climate, subgrade, and other material properties and local design preferences. Particular emphasis is devoted to the influence of traffic and reliability levels. The results suggest that relative to the NCHRP Project 1–37A predicted performance, the 1993 AASHTO guide overestimates performance (i.e., underestimates distress) for pavements in warm locations and at high traffic levels. Trends of pavement performance with reliability level were similar for both methodologies. The results suggest that the default design criteria incorporated in the NCHRP Project 1–37A software are broadly consistent with what would be observed historically from pavements designed with the 1993 AASHTO guide.