What automatic action occurs when a train exceeds 12 mph in Release mode?

When a train exceeds 12 mph in Release mode, the system is designed to ensure safety and operational efficiency by applying the service brakes until the speed reduces to 9 mph. This automatic action is crucial because Release mode is typically a state in train operation where the brakes are intentionally disengaged to allow the train to move forward. By having a threshold in place—where exceeding 12 mph results in the application of service brakes—it helps prevent potential unsafe conditions that could arise from excessive speed under these operational criteria.

Applying the service brakes effectively slows the train down to a safer speed, maintaining operational control and preventing risk associated with high-speed movement in a mode that does not support such velocity. This mechanism ensures that the train operates within predefined safety limits, thereby promoting a secure environment for both the train and its passengers.