Efficient Circulation of Railway Rolling Stock

Railway rolling stock (locomotives, carriages, and train units) is oneof the most significant cost sources for operatorsof passenger trains,both public and private. Rolling stock costsare due to materialacquisition, power supply, and material maintenance. The efficientcirculation of rolling stock material is therefore one of theobjectives pursued. In this paper we focus on the circulation of trainunits on a single line. In order to utilize the train units on thisline in an efficient way, they are added to or removed from the trainsin certain stations, according to the passengers' seat demand. Sinceadding and removing train units has to respect specific rules, it isimportant to know the exact order of the train units in the trains.This aspect strongly increases the complexity of the rolling stockcirculation problem. In this paper we present aninteger programmingapproach to solve this problem. We also apply this approach to a reallife case study based on the 2001-2002 timetable of NS Reizigers, themajor Dutch operator of passenger trains