Why is there a specific waiting time after a CBTC failure with emergency brake application?

The rationale behind having a specific waiting time after a Communication-Based Train Control (CBTC) failure accompanied by an emergency brake application primarily revolves around the need to allow the Automatic Train Control (ATC) car-borne equipment the opportunity to reset or restart. This process is crucial because, during a failure, the systems responsible for monitoring and controlling the train may enter a state where they cannot function properly. The waiting period is thus designed to avoid immediate action that could lead to further complications or risks. It provides the necessary time for the onboard systems to attempt a recovery, ensuring that the train can resume operations safely and efficiently if conditions permit.

The other options, while relevant to operational safety and procedures, do not address the specific technical needs during a failure scenario related to the restart of onboard systems. The emphasis on system recovery showcases the importance of maintaining operational integrity in train control systems.