A Safety-Security Assessment Approach for Communication-Based Train Control (CBTC) Systems Based on the Extended Fault Tree

摘要

Due to the wide application of computer, communication and control technologies in urban rail transit systems, amount of security threat are introduced, which can increase the security risks. Based on the safety- critical features of urban rail transits systems, lots of redundancy, fault-tolerant architectures are adopted, and fail-safe principles are also embedded into the operation mechanisms of the urban rail transit signalling systems. As a result, determining effects of security risks on safety of signalling systems is an urgent task. In the paper, based on the similarities and differences between the propagation principles of security risks and safety risks, the extended fault tree is proposed to perform the safety-security assessment for urban rail transit signalling systems, where security events could be taken as one kind of hazard of fault tree describing the evolution of safety risks. Considering some critical socenarios of signalling systems, the proposed approach demonstrates that security risks could significantly affect the operation efficiency of signalling systems due to the fail-safe designs while safety can be guaranteed based on the same fail-safe designs.