Development of Traffic Inputs for New Mechanistic–Empirical Pavement Design Guide

Vehicle classification and axle load data are required for the structural design of new and rehabilitated flexible and rigid pavements with the new Mechanistic–Empirical Pavement Design Guide (MEPDG) developed under NCHRP Project 1–37A. The axle load spectra are determined from traffic data collected at weigh-in-motion (WIM) stations, and vehicle count and class data are recorded by vehicle classification stations. Some preliminary results are presented for an extensive traffic data-processing effort conducted to develop traffic inputs required by the MEPDG to design pavements in New York State. The data collected by classification and WIM sites from 2004 to 2009 were processed with the TrafLoad software developed in NCHRP Project 1–39. The discussion focuses on the variability of the major traffic input variables required by the MEPDG, as obtained from data collected in New York State, and on the differences between the data obtained from individual stations, state average values, and the default values recommended by the MEPDG, where applicable. The effect of variability of the major traffic input variables on the performance predicted by the MEPDG for a typical flexible pavement structure is also discussed.