Traffic Characterization for a Mechanistic-Empirical Pavement Design

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Traffic Characterization for a Mechanistic-Empirical Pavement Design

J. A. Prozzi / F. Hong

The recently developed guide for the Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures (M-E Design Guide) will change the way in which pavements are designed by replacing the traditional empirical design approach proposed in the AASHTO 1993 Guide for the Design of Pavement Structures with a mechanistic-empirical based approach. One of the most significant changes offered in the M-E Design Guide is the difference in the method used to account for highway traffic loading. Traffic volume and traffic loads, the two most important aspects required to characterize traffic for pavement design, are treated separately and independently. Traffic loading is accounted for by using the axle load spectrum of each axle type of each vehicle class. For the most accurate design cases, project specific weigh-in-motion (WIM) data should be used with appropriate growth factors, projected to the length of the analysis period. At present, the network of WIM systems in Texas consists of approximately twenty WIM stations, the majority of which are located on interstate facilities. Increased WIM density and sampling frequency are necessary to accommodate the current requirements of the M-E Design Guide. Currently, the Texas Department of Transportation (TxDOT) uses a statewide average to generate load data for most highways. The goal of this research study was to assess and address the implications of the axle load spectra approach proposed by the M-E Design Guide.