What indication will the driver have that the Brake Pipe Mode has been activated?

When the Brake Pipe Mode has been activated, it is indicated by both indicators on all DM Fault Panels flashing. This visual alert ensures that the driver is immediately aware of the mode change, allowing them to respond accordingly. The indicators serve as a clear signal of the system's status, which is crucial for maintaining safety and effective control in operational scenarios.

In the context of this question, other options do not provide the correct or primary means of indicating the activation of Brake Pipe Mode. For instance, changes in the speed gauge, sound alarms, or dashboard lights may occur in different scenarios, but they do not specifically signify that the Brake Pipe Mode is engaged. Tuning into the flashing indicators on the DM Fault Panels is the defined protocol for this specific situation.