We are developing a protection system to eradicate the accidents related to maintenance work. This system is based on the concept that each device autonomously broadcasts its own information such as its location and velocity and controls its behavior using the information shared between all devices. In this paper, after introducing an overview of the protection system, we propose a system configuration and communications protocol to reliably exchange the information about locations and velocities between the devices using broadcast transmissions and a communications network that uses the IP multicast technology to effectively realize the system.

Copyright (c) 2004 Railway Technical Research Institute