Risk evaluation method for improvement of railway signalling systems

Abstract

High-level safety is essential for railway signalling systems, and so various measures are taken to prevent failures susceptible to lead to accidents based on the fail-safe concept, given that the type of accident cause by such a system failure is potentially serious. An International Standard, stipulating levels of reliability, availability, maintainability and safety for railway signalling systems, has recently been introduced. In this kind of system, safety is of utmost importance. However, considering the current requirement for highlevel of availability, this paper presents a case study on a risk evaluation, based on costs per unit of time, which can be used to represent not only safety factors but also availability.