Optimizing regular symmetric timetables: a method to reach the best modal split for railway

A regular timetable is a collection of events that repeat themselves every specific time span. This even structure, whenever applied at a whole network, leads to several benefits both for users and the company, although some issues are introduced, especially about dimensioning the service. It is therefore fundamental to properly consider the interaction between the transport demand and supply, to create an effective network timetable. In this paper, a specific cycle base to solve the Cycle Periodicity Formulation (CPF) of a symmetric timetable is proposed. This is combined with a modal choice model, adding the possibility to disable stops along lines for further increasing the transportation demand acquired by the railway system. The problem is modeled as a Mixed-Integer Linear Program (MILP) and solved through a state of the art MILP solver (CPLEX). Computational results regard a case study about a railway network in a northern Italy region.