Introduction of Heavy Axle Loads by the North American Rail Industry
The Association of American Railroads (AAR) initiated the Heavy Axle Load (HAL) Research Program in 1988 in order to “provide guidance to the North American railroad industry about whether to increase axle loads and to determine the most economic payload consistent with safety” (Kalay and Martland 2001). The research demonstrated the technical feasibility and economic desirability of increasing axle loads and the ability of technology to mitigate the adverse effects of heavier loads. In 1991, the industry decided to accept cars with 286,000 lb. gross vehicle weight (286k GVW) in interchange service. Since then, more than 90% of all bulk equipment acquired has been rated for 286k GVW. By 2010, nearly 100% of coal traffic and 30% of general freight moved in 286k loads.
Technological improvements resulting from the HAL research program have been critical in enabling the industry to reduce costs of 286k operations. Stronger materials, better designs, and improved maintenance techniques reduced life cycle costs for rail and other track components. Bridge costs did not increase as much as expected, because of technological developments and better understanding of their ability to withstand HAL loads.
Net benefits of HAL operations to railroads, suppliers, and their customers were approximately $6 billion between 1994 and 2010. Annual net benefits exceeded $600 million in 2010. Benefits included reductions in equipment expense, more efficient operations, and increases in line capacity. Given the technological advances in railroad engineering over the past 20 years, further increases in GVW or loading density should now be considered.
by Carl D. Martland