A safety-related transmission method for a new railway signalling system based on an IP-Network

We have developed a signalling system which controls signal devices through an IP-Network. This system consists of a Logic Controller (LC) and Field Controllers (FCs) connected with optical cable. The LC is a safety-related device located at the signal house. The LC generates the command data, and transmits the data to the FCs through IP-Network. The FC is a safety-related device equipped in each signal device, and controls the device based on the command data from the LC. In the railway signalling system, high level of safety and reliability are required. In this system, the transmission devices and protocol are based on the general technologies. Therefore, we need to assume all kinds of errors on the transmission devices, and the whole system must keep itself in safe status even if the worst error occurs. In order to comply with the IEC62280-1, we have developed a safety transmission protocol. Moreover, this system needs to operate for 20 years without system down. We have defined the target of the failure rate of each device less than 10(-7)/h. We measured the traffic limitation in order to validate the reliability about the transmission between the LC and the FC, and confirmed that the traffic is much less than the traffic limitation of the transmission device. We have evaluated the safety and reliability of this system with prototype system, and put this system into practical use at Ichikawaono station on the Musashino line in February 2007.