A New Approach to Shortest Route Finding in a Railway Network with Two Track Gauges and Gauge Changeovers

Abstract

The Spanish railway network is a complex one, due to the existence of standard gauge (1,435 mm), Iberian gauge (1,668 mm), and dual gauge (with three rails) subnetworks, as well as connections between the two first subnetworks (at the so-called gauge changeovers), usable by dual gauge trains. Two of the authors developed a package for shortest route finding, and consumes, costs, and emissions calculations in the Spanish railway network (within the frame of two research projects funded by the Fundación de los Ferrocarriles Españoles–Spanish Railways Foundation). Nevertheless, the approach required from a curious specific algorithm to be developed ad hoc. In this paper, a much simpler approach to shortest route finding in such a network, which merges the three subnetworks into two and considers the gauge changeovers as connections between the two new subnetworks, is detailed. This approach allows to use any standard shortest route algorithm. It has been implemented in the computer algebra system Maple and is applied in this paper both to small specific cases and to the whole Spanish railway network.