Cost of Pavement Damage Due to Heavier Loads on Louisiana Highways: Preliminary Assessment

A preliminary assessment is made of the impact of increasing the gross vehicle weight (GVW) from current legal limits to 100,000 lb (45 400 kg) on vehicles hauling sugarcane, rice, timber, and cotton. Sections of road were chosen in each area of Louisiana where commodities are produced, the amount of each commodity hauled was estimated, and the effects of increasing the GVW were evaluated for each section using pavement design models. Design data were secured from the Louisiana Department of Transportation and Development computer database and project files to determine the pavement design parameters and traffic estimates for each road. The number of vehicles hauling the 1998 harvest payload was estimated, a projected increase in the production of each commodity was estimated on the basis of government statistics, and rehabilitations were designed with the use of the 1986 AASHTO Design Guide for a 20-year analysis period. Present worth (PW) was calculated for each GVW scenario for each roadway. Comparisons of PW between the weight scenarios showed that increases in GVW have more effect on state and U.S. highways than they do on Interstate highways. Any increase in GVW over current limits increases the cost of overlays and decreases the length of time before an overlay is required. The cost increase due to increasing the GVW is substantial. Fee structures should be modified by the legislature so that these costs are paid for either through the current registration and overweight permit fee structure or through some new tax, such as a ton-mile tax.