Efficient Circulation of Railway Rolling Stock

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