Development and Implementation of Axle Load Spectra for Overweight Truck Traffic for a Mechanistic-Empirical Pavement Performance Evaluation

Abstract

Oversize-overweight (OSOW) permit vehicles often operate using heavier axle loads than typical truck traffic, in addition to their higher gross vehicle weights. Heavy vehicles are a special concern to pavement engineers due to their correspondingly higher likelihood of causing pavement deterioration. Using a six-year database of single-trip overweight (OW) permits issued in Wisconsin and the results of an extensive route mapping effort, axle load spectra (ALS) were calculated for OW permit vehicles for selected state highway segments. Baseline traffic parameters from the Wisconsin Department of Transportation (WisDOT) corresponding to the selected segments were disaggregated, and the OW ALS were meshed with baseline traffic to create combined ALS. The comparative results of Mechanistic-Empirical Pavement Design Guide (MEPDG) analyses on segments of interest using baseline ALS versus meshed ALS allowed for the estimation of differential pavement damage resulting from the OW permit vehicles. For example, the average per-vehicle deterioration rate from OW trucks on State Trunk Highway 11 ranged from 1.09 to 6.69 times the baseline rate for different types of pavement deterioration. This methodology can be applied to any roadway in order to estimate the pavement effects caused by the addition of vehicles to baseline traffic.