Automatic safety analysis of of computer-based railway signalling system

Ensuring safety in railway signalling system is always considered as significant as a guarantee of the safe and efficient operation of the whole railway. In fact, safety analysis of the signalling system with distributed computer technique is becoming extraordinarily difficult because of the frequent and complex interaction between components and the various backup modes. The dominant approaches are subjective, difficult to be reused, not well structured, thus leaving the safety analysis process time-consuming and error-prone. This paper develops a hierarchical methodology for safety analysis based on the failure propagation model and state-transition model. Unlike traditional safety analyses, the proposed approach demonstrates more accurate representation of practical failure behaviour in computer-based signalling system. Dynamic properties, system structure and failures in component level are separately modelled in different layers, and connected with synthesis laws. The analysis can be easily refined as the system design progresses and automatically produces safety-related information to help engineer in making design decisions. The preliminary design of Communication Based Train Control (CBTC) system for Yizhuang Line in Beijing is used to demonstrate the approach.