Analysis of Data on Heavier Truck Weights

Abstract

Knowledge of truck axle weights and distribution is critical for assessing the damaging effects of loading on pavements. A study was initiated in Wisconsin to investigate the impact of a new law that allows vehicle combinations up to 98,000 lb on six axles to transport raw forest products during the spring thaw suspension period. Analysis of truck weight data collected at two logging industrial facilities was done to determine whether certain logging trucks were more damaging than others. The data collected included truck axle weight and spacing from platform scales at two logging industrial facilities, plus scale operators' monthly supplied log truck reports covering the period of December 2011 to May 2012. Analysis revealed that a considerable proportion of trucks were overloaded at the two facilities, with overload averaging 31% and 24% in winter and 25% and 33% in spring. The magnitude of the overload, however, averaged less than 5% of the 98,000-lb limit permitted under the law for gross vehicle weight. FHWA Class 9 loaded trucks produced a higher damage factor compared with that of Class 10 loaded trucks. In addition, Class 9 loaded trucks resulted in a lower average relative log carrying efficiency of 15,400 lb per equivalent single-axle load compared with 22,000 lb per equivalent single-axle load for Class 10 loaded trucks. Better truck configuration choices can benefit both the industry and the highway agency by allowing the industry to haul more logs while inflicting less damage to the pavement.