Effects of Heavy Truck Operations on Repair Costs of Low-Volume Highways

The economic impact of overweight permitted vehicles hauling sugar cane on Louisiana highways is evaluated. The highway routes that are used to haul this commodity are identified and statistical samples are selected and analyzed. Two different vehicle types and three different gross vehicle weights are chosen including 100,000-lb. and 120,000-lb. AASHTO design guidelines are used to determine the effects of heavy loads on pavements and bridges. The approach requires the overlay thickness needed to carry traffic from each gross vehicle weight for the design period and costs based on 20-year period. The state bridges are evaluated to satisfy regulations for the loading requirements and a fatigue cost is estimated for each safe crossing of a bridge. Results indicate that the damage from each FHWA Type 9, with a gross vehicle weight of 100,000-lb sugar cane load, to pavement and the bridge fatigue cost is at bout $5,500/year. Therefore, the current sugar cane trucks permit fee of $100 per vehicle per year is not adequate to recover these costs. It is recommended that the current 100,000-lb. gross vehicle weights be maintained, but the permit fees are increased, or the vehicle type is changed from a FHWA-Type-9 to a Type-10 vehicle. Under the second alternative, the permit fee can be reduced to zero and a tax incentive of $683 can be given to each truck for the conversion. Also, it is necessary to increase the highway funds to handle the extra damage caused by the increase of truck load limits.