What is the primary function of the emergency air brake feature?

The primary function of the emergency air brake feature is to stop the train quickly in the event of an emergency. This system is designed to respond rapidly to critical situations, allowing for a swift and effective braking action to minimize potential accidents or derailments. In contrast to other braking methods that are meant for gradual stops or controlled deceleration, the emergency brake system is intended specifically for urgent scenarios where immediate stopping is essential, ensuring the safety of the train and its occupants.

While the other options address important aspects of train braking systems—such as gradual stops during routine operations or manual overrides—none serve the critical need for a rapid response in emergency situations like the emergency air brake does.