Efficient loading of intermodal container trains

Abstract

Efficient loading and unloading of trains is crucial if rail transport is to compete with road transport. The cost of rail transport can be reduced by improving the placement of containers on trains so that the number of wagons required is minimised and so that the train can be operated safely and efficiently. The cost of terminal operations, and the delays experienced by customers' trucks, can be reduced by improving the procedures used to load and unload trains.

We divided the problem into three subtasks. The first task is to develop a load plan for a train based on the expected mix of containers. An ideal plan specifies positions on the train for various container types in a way that minimises the number of wagons required while meeting a number of packing, safety and aerodynamic constraints. The second task is truck dispatching - when a truck arrives at the terminal, where should it be sent? This problem is not straightforward because trucks arrive randomly and loading and unloading occur simultaneously, and so the ideal position for a container may not yet be available. The third task is to dispatch the stackers that transfer containers between trains and trucks in such a way that truck waiting time is minimised.

The train planning problem can be formulated as an integer programming problem, but it can also be solved using the OASIS software already owned by National Rail Corporation. Train plans can be made more flexible by using container classes rather than specific container details.

The study group suggested several truck dispatch schemes, but did not have sufficient data to evaluate the schemes.