Increasing the capacity and gross weight of North American freight cars above the current 263,000-pound car (33-ton axle loads) is one way to improve the productivity of rail freight operations. An increase in expenditures on track and bridge maintenance is normally essential if axle load increases are to provide promised benefits. If each train can carry more net tons of bulk commodity safely, then productivity savings will be achieved by reducing the number of train crews required to haul a given tonnage. If the ratio of net-to-gross tons can be increased, additional savings can be achieved in fuel, track costs, and equipment costs. With fewer trains to move any given tonnage, there will be an improvement in capacity and a reduction in meet-pass delays.

Over the past 15 years, Transportation Technology Center, Inc. (TTCI), a subsidiary of the Association of American Railroads (AAR), has devoted extensive research efforts to safety, technical, and economic issues related to increasing axle loads. Much of the research has been based upon the five phases of the Heavy Axle Load (HAL) test program. More than 1,200 million gross tons (MGT) of HAL traffic was accumulated at the Facility for Accelerated Service Testing (FAST) located at the Federal Railroad Administration’s (FRA) Transportation Technology Center near Pueblo, Colorado. AAR and the FRA jointly fund the HAL program with significant cooperation from railroads and suppliers.

Results show that, in general, heavier axle loads will increase track and facility costs, but decrease operating and equipment costs. Since track costs are much smaller than combined operating and equipment costs, HAL operations can be economically beneficial even if the percentage increase in track costs is far greater than the percentage decrease in operating plus equipment costs. However, it should be emphasized again that in situations where track and bridges need upgrading for heavier axle loads, investment in track and bridges needs to be made first in order to realize the operating benefits from HAL operations. Total track costs were predicted to rise 5 to 10 percent under 286,000-pound cars (36-ton axle loads) and 15 to 18 percent under 315,000-pound cars (39-ton axle loads). Bridge costs, which were included as their own separate category, were predicted to rise faster than track costs. While the predicted increases for bridges were extremely high, bridge costs were only 10 to 15 percent of track costs in the base case, so they did not dominate the analysis.

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