Communication in Safety Systems for Railway Transport Using the Example of Axle Counter

The article shows rules and guidelines used during safety analysis of a communication system. It refers to EN 50159:2010 European standard, which includes guidelines for definition of categories and risks in telecommunication network and defences used to protect the system against hazards. One of the elements of the transmission protocol safety analysis is calculation of the Hazardous Failure Rate (HR). The analysis incorporates mixed systems, i.e. a safety-related transmission system with the standard non safety-related one. The chosen idea (black/grey channel) allows to transfer safe and standard data through the same telecommunication bus. Encapsulation of safety data into the protocol based on Ethernet allows to use the standard telecommunication devices and reduce the required hardware. The article refers to practical solutions used in the UniAC2 axle counting system.