Fleet Sizing and Empty Freight Car Allocation
Empty freight car allocation problems and fleet sizing problems are highly important topics in the field of railway cargo optimization. Fleet sizing is mainly used in order to find the minimal number of freight cars (with fixed costs) needed to operate the transportation network successfully (e.g. satisfying customer demands). After a consignment is transported to its destination, the unloaded freight cars must be reallocated. This reallocation process is linked to costs depending on the traveled distance.
In this paper we propose a network flow problem on a time-space network, formulated as integer linear program (ILP), for determining the optimal trade-off between the number of freight cars and the costs of empty vehicle allocation. The ILP is tested on a distribution network that is related to a specific part of Rail Cargo Austria’s railway network. Different modifications in the network (changes in cost structure, travel time and demand) are examined and compared to the basic scenario.
KeywordsFleet sizing Empty freight car allocation Distribution network Integer linear programming
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