What is the consequence of failing to acknowledge a mode change in a timely manner?

Failing to acknowledge a mode change in a timely manner has significant safety implications in train operations. When a mode change occurs, the system often expects the engineer to confirm and respond to the change appropriately. If this acknowledgment does not take place, the system is designed to assume that the engineer may not be aware of the new operating conditions.

As a precautionary measure, the train will apply the service brakes to halt the train safely. This action prevents potential hazards that might occur due to the train operating in an improper mode or at inappropriate speeds, thereby enhancing safety for both passengers and infrastructure.

The other options do not align with the operational protocols in place for handling mode changes. For instance, allowing the train to resume normal operation or continue in its current mode without acknowledgment could lead to dangerous situations. Triggering an alarm is part of the alert system but does not directly prevent critical operational risks like an uncontrolled movement of the train.