Short-term planning
Every day there are minor modifications of the timetable due to some extra trains (charter trains, extra trains for e.g. sport events) or speed limitations on some parts of the infrastructure due to track maintenance. In general, these minor modifications have no influence on the rolling stock and crew schedules. However, almost every weekend there are large parts of the networks outside service due to large maintenance projects or construction works on the extension of the network. For instance, currently (i.e. 2005), due to the quadrupling of the line Amsterdam - Utrecht about 5 weekends a year no train traffic is possible on this heavily used line. In such cases, the timetable is usually modified locally. However, such local modifications of the timetable may destroy rolling stock and crew schedules on a global level. The rolling
stock circulation and the crew schedules need to be repaired then as well. Since — to the best of our knowledge — these problems have not been studied in the literature so far, we will only give a short problem description here. Finally, we discuss in this section another short-term planning problem, which is the maintenance circulation of rolling stock.