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Published: 2004

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The 1993 American Association of State Highway and Transportation Officials (AASHTO) Guide for Design of Pavement Structures is a mere modification of the empirical methods found in its earlier versions that are based on regression equations relating simple material and traffic inputs. Although the various editions of the AASHTO design guide have served well for several decades, they contain too many limitations to be continued as the nation's primary pavement design procedures. The Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure, on the other hand, provides the tools for evaluating the effect of variations in input data on pavement performance. The design method in the MEPDG is mechanistic because it uses stresses and strains in a pavement system calculated from the pavement response model to predict the performance of the pavement. The empirical nature of the design method stems from the fact that the pavement performance predicted from laboratory-developed performance models is adjusted based on the observed performance from the field to reflect the differences between predicted and actual field performance. The performance models used in the MEPDG are calibrated using limited national databases and, thus, it is necessary to calibrate these models for local highway agencies implementation by taking into account local materials, traffic information, and environmental conditions. Two distress models, permanent deformation and bottom-up fatigue cracking (hereafter referred to as alligator cracking), were employed for this effort. Fifty-three pavement sections were selected for the calibration and validation process: 30 long-term pavement performance (LTPP) pavements, which include 16 new flexible pavement sections and 14 rehabilitated sections, and 23 North Carolina Department of Transportation (NCDOT) sections. All the necessary data were obtained from the LTPP and the NCDOT databases. To provide reasonable values in cases where data were missing, MEP.