Safety requirements about railway signaling system utilizing network and its implementation

Many signaling equipments (e.g. signal, level crossing) are installed along the railroad-track, and these are working in cooperation with each other referring to other signaling equipment conditions. In today´s railway signaling system, those conditions are transmitted using signal cables. On the other hand, signal cables are part of the signal control circuit. Owing to this installation of signaling system itself, especially installation of signal cable, we have some problems in our signaling system. The problems are: high cost for construction; much maintenance work is needed; and it has a long restoration time when it has failed. To solve these problems we propose a networking of signaling equipment. The benefits of networking is simplifying the system by separating the transmission means of the condition from the control logic, improving flexibility by sharing control conditions, and realizing remote maintenance and test by remote connection. In this paper, we introduce the network system, which controls railway signaling equipment and applications utilizing this network. Then we define the requirements for securing safety and reliability of this system, and describe techniques for realizing the requirements.