An optimization model for Integrated Timed Transfers and its application to regional passenger railway networks

In this paper, a mathematical programming optimization problem is shown to calculate time-tables for a regional railway network under the integrated timed transfers approach, or also the ‘strategic passenger-oriented time tabling’ (SPOT). These types of networks are characterized for containing a subset of critical points or centers, and a set of reference clock times, at which several transit lines may meet for synchronization, allowing for attractive transfer of passengers between lines. In this way, ‘secondary’ origin-destinations may have a more appealing and reduced travel time, making the system behave locally as ‘network-oriented’. Since the model is intended for application to small-to-medium size networks, the corresponding ‘boundary conditions’ marked by: a) freight traffics, b) large distance connections crossing the test area (including high speed train services) and c) regional services originating at the neighbor metropolitan area, are specially taken into account by the model. The model is applied on a test area consisting of two provinces in Catalonia (Spain) affected by these boundary requirements. The application of the model results in a reduction of the internal trip times amongst the cities of the Test Area, while leaving the travel times between external connections with very small increase and, in some cases, with better travel times. A comparison with travel times by car also illustrates the potentiality of impact in environmental questions. Reasonable computational times, with near-optimal solutions, show the viability of the model.