Evaluating the Effects of Heavy Sugarcane Truck Operations on Repair Cost of Low Volume Highways

16.Abstract This study assesses the economic impact of overweight permitted vehicles hauling sugarcane on Louisiana highways. The highway routes being used to haul these commodities were identified, and statistically selected samples were used in the analysis. Approximately 270 control sections on Louisiana highways carry sugarcane are involved in the transport of this commodity. Three different gross vehicle weight (GVW) scenarios were selected for this study including: 80,000 lb., 100,000 lb. and 120,000 lb. The maximum current allowable GVW is 80,000 lb. while the maximum 100,000 lb. GVW is the permitted load for sugarcane trucks and is currently the highest load level permitted by Louisiana laws. The methodology for analyzing the effect of these loads on pavements was taken from the 1986 AASHTO Design Guide and involves determining the overlay thickness required to carry traffic from each GVW scenario for the overlay design period. Differences in the life of an overlay were calculated for different GVW scenarios and overlay thickness and costs were determined for a 20 year analysis period. These costs were developed for samples taken from all the control sections included in the study. These net present worth costs from the samples were expanded to represent the cost for all control sections carrying sugarcane. Results indicate that the damage from each sugarcane truck with a GVW of 100,000 lb. to pavement overlay is at about $2,072/year and to bridge fatigue cost is at about $3,500/year. Therefore, the current sugarcane trucks permit fee of $100 per year is not adequate and should be increased to recover these costs. The legislature should not consider raising the GVW level to 120,000 lb. because the pavement overlay costs increase by two folds (double) and the bridge repair costs become very large. Moreover, the magnitude of the damage caused by the 120,000 lb. GVW for a FHWA Type 9 truck makes the risk of bridge damage and even bridge failure too significant to ignore. The project staff recommends that the legislature keep the GVWs at the current level but increase the permit fees sufficiently to cover the additional pavement and bridge costs or change the configuration of the axle on the trailer from a tandem to a triple, effectively changing the vehicle from a FHWA Type 9 to a Type 10 vehicle. Under these circumstances, the permit fee can be reduced to zero and a tax incentive of $683 can be given to each truck for the conversion. It is recommended to allocate more highway funding for handling the extra damage caused by the increase of truck load limits.