Over the past two decades, the changing transport demands of agriculture and rural industry and the strategic rail decisions that resulted in the abandonment of many rural rail links have had severe impacts on rural road infrastructure. As larger and heavier trucks haul products over longer distances on rural pavements, the financial ability of the state and local governments to maintain and improve the rural road network has been diminishing. Clearly there is a need to recognize the significance of the agriculture–transport relationship and to determine the impacts on rural roads associated with major agricultural traffic generators to ensure the sustainability of rural road networks. Evidence of the increased truck volumes associated with industrialized agriculture and strategic changes in the rail industry is provided through a case study of the grain industry, with specific emphasis on the production and consumption of corn in Texas. A methodology is suggested to quantify the impacts of increased truck volumes and axle loads on rural pavements that were not designed or built to accommodate more and heavier axle loads. It is believed that a simple methodology to quantify pavement damage can be invaluable to demonstrating rural maintenance needs and to informing rural transport investment decisions.

The natural gas reserve in the Barnett Shale geological formation is one of the largest onshore natural gas reserves in the United States. The development of a natural gas well is a traffic-intensive operation that involves high volumes of truck traffic; saltwater traffic generated during the production phase is a major contributor to truck volume. The effect of traffic related to the natural gas industry on Texas highways is quantified. The oversized and overweight database maintained by the Texas Department of Transportation (DOT) was used to quantify several key characteristics of the rig traffic. In addition, personnel from the Texas DOT's Fort Worth District provided critical information about construction and saltwater traffic, including truck types used, gross vehicular weights, number of trips, and haul distances. Pavement sections were located along the busiest trucking corridors to evaluate damage caused by the truck traffic associated with natural gas development. Results indicated the approximate damage due to rig traffic was 1.6%, to construction traffic was 13%, and to saltwater traffic was 6%, relative to the damage caused by design traffic in terms of rutting. Additional damage caused by the natural gas truck traffic translated into reduced service life for pavements in the region. Results indicated a reduced service life of approximately 5.6%, 29%, and 16% associated with rig, construction, and saltwater traffic, respectively, in terms of rutting.

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The allocation of highway costs is constantly debated among legislatures, highway agencies, and highway users as it directly relates to concerns about equity in terms of cost responsibility and actual user charges. One of the major challenges in highway cost allocation stems from the need to estimate pavement damage by different vehicle classes. Normally, the calculation of damage caused by heavy vehicles to the highway infrastructure utilizes the concept of Equivalent Single Axle Load (ESAL). This concept was empirically established after the American Association of State Highway Officials America (AASHO) Road Test almost half a century ago. Although the ESAL concept is widely used in pavement design, it has a number of shortcomings when applied for the estimation of pavement damage by different vehicle classes. Some of these limitations include: failure to account for specific infrastructure and environmental conditions, disregard of the differences in traffic configurations and composition, and the inability to capture different distress types. This leads to a fairly inaccurate and generic estimation of pavement damage by vehicle class. This paper proposes an innovative and more rational highway cost allocation approach based on the recently completed guide for the "Mechanistic-Empirical Design Guide of New and Rehabilitated Pavement Structures" developed under the National Cooperative Highway Research Program (NCHRP) Project 1-37A. The Guide accounts for all factors that contribute to pavement deterioration, thereby addressing the shortcomings of an ESAL-based analysis listed earlier. Estimates for pavement damage attributable to each vehicle class can thus be accurately simulated. For the purposes of this study, traffic data collected at a weigh-in-motion station in Texas were used to estimate the highway cost shares of different vehicle classes, given different pavement structural capacities.

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