Time-triggered exchange of train route data between train control systems
Markus Montigel · Annual Conference on Computers · 2002
Increased heterogeneity and decentralization of train control systems, often requiring collaboration from many suppliers, calls for a simplification of the involved interfaces. Time-triggered protocols (TTP) are a favorable alternative to event-triggered protocols, which are still used in most vital computer-based applications involving data exchange. To take full advantage of TTPs, the used telegrams should be of fixed length whenever possible. This poses a problem in transmitting state information of ambiguous train routes. To deal with this issue, an algorithm to derive a unique route index is presented in this paper. The proposed approach relies exclusively on geographical track layout data, without the exchange of explicit route tables between collaborating suppliers. As a means of representing track topology data and to introduce the route indexing algorithm, Double Vertex Graphs are used, which, in contrast to ordinary graphs, allow for a correct representation of the topological properties of railway tracks. The indexing scheme proposed has been successfully applied in a pilot project of an ERTMS Level 2 system currently being commissioned by Swiss Federal Railways.