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oai:drops-oai.dagstuhl.de:3699 2024-03-06T10:29:03Z ddc:004 open_access

Optimal Freight Train Classification using Column Generation Bohlin, Markus Dahms, Florian Flier, Holger Gestrelius, Sara Column generation integer programming scheduling shunting classification marshalling transportation railways We consider planning of freight train classification at hump yards using integer programming. The problem involves the formation of departing freight trains from arriving trains subject to scheduling and capacity constraints. To increase yard capacity, we allow the temporary storage of early freight cars on specific mixed-usage tracks. The problem has previously been modeled using a direct integer programming model, but this approach did not yield lower bounds of sufficient quality to prove optimality. In this paper, we formulate a new extended integer programming model and design a column generation approach based on branch-and-price to solve problem instances of industrial size. We evaluate the method on historical data from the Hallsberg hump yard in Sweden, and compare the results with previous approaches. The new method managed to find optimal solutions in all of the 192 problem instances tried. Furthermore, no instance took more than 13 minutes to solve to optimality using fairly standard computer hardware. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Markus Bohlin and Florian Dahms and Holger Flier and Sara Gestrelius 2012 Is Part Of OASIcs, Volume 25, 12th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (2012) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/OASIcs.ATMOS.2012.10 urn:nbn:de:0030-drops-36997 https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2012.10 eng https://creativecommons.org/licenses/by-nc-nd/3.0/legalcode