Burlington Northern's Assessment of the Economics of High Capacity/ Heavy Axle Load Cars
Date
1990-05
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Publisher
American Railway Engineering Association
Abstract
North American freight cars and trains have been growing heavier for many years. For the most part this has been a response to competitive pressures, the inflexible nature of train crew costs, and the changing mix of traffic. The shift in traffic towards bulk commodities and unit trains (grain, coal, ore, and aggregates) was one manifestation of this change in traffic mix and its consequent movement toward heavier cars. Figure I shows graphically the near doubling of average car capacity since 1929. This trend to heavier cars has been accompanied by considerable research into the costs and benefits of larger cars and heavier trains. In particular, the issue of increasing car size, and consequently increasing axle loads, has been the subject of much examination and discussion. There s also the related issue of increasing the loading of existing cars. This issue was raised in 1986 at the Third International Heavy Haul Railways Conference (I) attended by representatives of Burlington Northern's Research & Development Department. In the opening paper of the conference, representatives of Mt. Newman Mining Co. and BHP Melbourne Research Laboratories stated that heavier axle loads were not only technically feasible but were also economically feasible under the conditions as experienced, tested, and applied in Australian heavy haul operations. This paper emphasized that since existing ore cars were only loaded to about 75% capacity, axle loads could be further increased. Following the First International Heavy Haul Railways Conference in 1978, axle loads were increased by the Australians to 33 tonnes (36.3 tons) and this axle load was adopted as a system wide standard. The successful gain led to adoption of an additional axle load increase to 35 tonnes (38.5 tons). Even higher axle loads appeared economically justifiable; however, the 35 tonnes provided an additional margin of comfort below the 37 tonnes (40.7 tons) level at which the Australian road's studies indicated that major, cost-impacting bridge upgradings would be required. As illustrated in Figure 2, the main point of the Australian findings was that axle loads between 33 and 37 tonnes (36 and 41 tons) were expected to reduce total railway maintenance and replacement costs. Costs were reduced 1-4% by increasing axle loads from 36 to 40 tons but began increasing beyond that point. In many ways, BN's Northern Coal Route is similar to the Mt. Newman Railway. It is composed almost entirely of welded rail, the bulk of it being 132 1b. section. Locomotive-borne lubrication is used and profile grinding of the rail is carried out twice per year. The vast majority of the traffic on the line is unit coal traffic. However, since BN's Northern Coal route is not an isolated captive railway, maintenance standards for both track and structures may be less rigorous. Mixed traffic and bridges of varying age and capacity present problems not encountered by the Australian railways.
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Citation
Newman, R. R., Zarembski, A. M., Resor, R. R., “Burlington Northern's Assessment of the Economics of High Capacity/Heavy Axle Load Cars”, Bulletin of the American Railway Engineering Association, Bulletin 726, Volume 91, May 1990.