Comparison of Pavement Design Using AASHTO 1993 and NCHRP Mechanistic-Empirical Pavement Design Guides

The new Mechanistic-Empirical Pavement Design Guide (MEPDG) provides methodologies for mechanistic-empirical pavement design as opposed to the empirical methodology used in the 1993 American Association of State Highway and Transportation Officials (AASHTO) pavement design guide. The objective of this study was to compare the pavement designs obtained using the 1993 AASHTO and the new MEPDG methods for typical Portland Cement Concrete (PCC) and Asphalt Concrete (AC) pavements in Kansas. Five in-service Jointed Plain Concrete Pavement (JPCP) projects were reanalyzed as equivalent JPCP and AC projects using both approaches at the same reliability level. The results show that the new MEPDG analysis yielded thinner AC sections for all projects than those obtained from the 1993 AASHTO design guide analysis. Four of the PCC sections, designed using the 1993 AASHTO design guide, were thicker than the sections obtained with MEPDG. The MEPDG analysis resulted in the same PCC slab thickness for the fifth project. Almost all AC pavements failed in the reliability criterion associated with top-down longitudinal cracking. For PCC pavements, failure happened in two distress categories — transverse cracking, and mean joint faulting. Achieving target reliability in the PCC analysis was also an issue.