What is the effect of a signal failure under CBTC on ATC operations?

In the context of Communications-Based Train Control (CBTC) systems, if there is a signal failure, the system has protocols to ensure safety and prevent potential accidents. When a signal failure occurs, the typical procedure is to force the signal to display a red aspect. This action effectively halts train movements in the affected area, which is critical for maintaining safety standards and ensuring that trains do not proceed into potentially dangerous situations without clear indications.

Forcing the signal to red ensures that all trains recognize the situation and act accordingly by stopping or holding at the last known signal. This procedure minimizes the risk of collisions or derailments by ensuring that no train can advance past a failed signal without explicit and safe commands. In CBTC systems, maintaining strict safety protocols is paramount, which is why this action is standard practice in the event of any signal failures.

Other scenarios, such as having the train continue as normal or adjusting the signal to yellow, would introduce unnecessary risks and are not in line with safety protocols established for train operations. When a signal fails, prioritizing the safety of all operations by enforcing a stop is the only acceptable response.