8. Current limitations of CBTC systems

8.1 Non-resiliant CBTCs

Given the extremely high availability requirements placed on urban signalling systems, the subsystems that make up the CBTC architecture are all redundant (i.e. no single failure can halt operation). Total equipment failure is extremely rare. However, the exceptional occurrence of such an event (double failure, for example) completely interrupts service. It is difficult to restart the system. The stoppage may also be due to an external cause (fire, power failure, flood, etc.). As CBTC systems are increasingly designed for driverless operation, the question of rapid service resumption will become increasingly important. In 2021, there are no constructive measures in place to provide a satisfactory response to this concern. The following options are being considered:...