In the planning process of railway companies, we
propose to integrate important decisions of network
planning, line planning, and vehicle scheduling into
the task of periodic timetabling. From such an integration, we
expect to achieve an additional potential for optimization.
Models for periodic timetabling are commonly based on
the Periodic Event Scheduling Problem (PESP).
We show that, for our purpose of this integration,
the PESP has to be extended
by only two features, namely a
linear objective function and a symmetry requirement.
These extensions of the PESP do not really
impose new types of constraints, because practitioners
have already required them even when only
planning timetables autonomously without interaction with
other planning steps.
