Dynamics


Project:   Determination of the Optimal Equipment Type for Movement
                of Intermodal Containers

Client:    Burlington Northern Railroad

In 1987, Burlington Northern Railroad faced rapid growth in the movement of ocean containers between the port of Seattle, Washington and the railroad’s terminal in Chicago. Additional equipment was needed to handle the traffic. Possible equipment choices included: conventional, single-level 89-foot flat cars, bulkhead double-stack cars with 33-ton axle loads, "IBC" double-stack cars with 33- or 39-ton axle loads, and "stand-alone" (non-articulated) double-stack cars with 27-ton axle loads

Factors affecting car choice included:

The weight distribution of the containers to be moved

Capacity of bridges and track to handle increased axle loads

Available clearances in tunnels and under bridges, and the cost of increasing them

The volume of containers to be moved

Length of crossing loops on the line (limit on train length)

Cost and tare weight of each equipment type

In a multidimensional analysis, computer simulation was used to develop maximum train size, motive power requirements, running times, and fuel consumption. Direct movement costs were calculated, comprising fuel, crew cost, equipment ownership and maintenance cost, and track maintenance cost. A Monte Carlo simulation based on a sample of container weights was carried out to determine the range of axle loads that might be expected. Costs were reduced to a charge per container, and the least-cost equipment type was identified.

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