Integrated traffic planning: Line planning and timetabling revisited In the first part of the talk, an overview on line planning and timetabling is provided. Given an existing public transportation network with its stops (or stations) and direct connections, the first step in the strategic planning of a transport system is to define lines and their frequencies. A line is a path in the public transportation network along which regular service is offered. We discuss various optimization models minimizing either the costs of the lines or maximizing the convenience of the passengers. If the lines have been found, the next step is to design a timetable. There are two different models: Periodic timetables which are repeated on e.g. an hourly basis and aperiodic timetables. The usual aim is to minimize the traveling time for the passengers. Integer programming formulations will be provided for both problem types and algorithmic approaches for finding timetables will be shown. Looking at these two problems sequentially is the usual procedure in traffic planning. However, the following important issues are neglected: - Delays or disturbances are not taken into account in the planning phase. This calls for robust line plans and robust timetables, and good strategies on how to deal with delays in the operational phase. - A challenging problem concerns the route choice of the passengers. In many papers it is assumed that it is already known how the passengers travel, i.e. a passenger's weight is assumed to be known for every edge or activity in the system. This is an unrealistic assumption since the route choice of the passengers depends on the lines, the timetable, and on the delay management strategy. We will discuss how the passengers' decisions may be integrated into the optimization process. - An integration of the subsequent planning steps line planning and timetabling can provide better solutions than the sequential process. An integrated evaluation can be done using our toolbox LinTim. We further discuss how an integrative planning can be realized.
