When should a conductor signal for a brake application during a CBTC system failure?

The correct approach in this scenario is to signal for a brake application immediately upon realizing the failure of the Centralized Bus Train Control (CBTC) system. This is critical for several reasons.

Firstly, the CBTC system is designed to manage train operations and ensure safety through continuous communication and control. A failure in this system poses a potential risk of uncontrolled movement, which could lead to dangerous situations such as collisions or derailments. By signaling for a brake application without delay, the conductor plays a pivotal role in safeguarding passengers and the train itself.

Additionally, immediate action minimizes the time the train may operate under unsafe conditions, thereby enhancing overall safety. Promptly signaling for brakes enables the conductor to bring the train to a controlled stop, allowing for necessary evaluations and repairs to be made.

While other options may seem situationally relevant, they do not prioritize the immediate safety and operational integrity that signaling for a brake application provides in the event of a CBTC failure.