Traffic Characteristics and Their Impact on Pavement Performance for the Implementation of the Mechanistic-Empirical Pavement Design Guide in Idaho

Abstract

This study addresses the development of traffic characteristics to facilitate the implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG) in Idaho. Classification and weight data collected at 25 weigh-in-motion (WIM) sites were procured from Idaho Transportation Department (ITD). Among these 25 sites, only 12 sites were found to have complete and accurate data. Site-specific axle load spectra (ALS), monthly adjustment factors (MAF), vehicle class distribution factors (VCD), and number of axles per truck type were developed. Predicted distresses and International Roughness Index (IRI) based on a typical pavement section and traffic data obtained at the investigated WIM sites (level 1) were compared to predicted distresses/IRI using statewide/national (level 3) default traffic inputs. This comparison revealed that ALS, VCD, and MAF input level have significant impact on longitudinal cracking. Statewide ALS yielded high differences in alligator cracking predictions while MAF and VCD yielded only moderate differences compared to site-specific ALS. Very low prediction differences occurred in rutting when statewide/national default ALS, MAF, and VCD were used as opposed to site-specific data. The level of input of the investigated traffic parameters did not affect IRI. Finally, it was found that statewide/national number of axles per truck can be used instead of site-specific values without sacrificing accuracy of pavement performance predictions.