What emergency procedure should be initiated if a train loses its air supply?

When a train loses its air supply, activating the emergency brakes becomes crucial because the braking system relies on compressed air to function properly. In the absence of air pressure, it is vital to quickly engage the emergency brakes to prevent the train from moving uncontrollably or becoming a safety hazard. This action is essential for maintaining safety and ensuring that the train comes to a complete stop in a controlled manner.

In contrast, notifying dispatch, signaling for help, or increasing speed could potentially exacerbate the situation. Dispatch might need to be informed later once the immediate risk is managed, but taking prompt action to secure the train's safety is the priority. Signaling for help may not be effective if the train is still in motion and poses a danger. Trying to accelerate to reach the next station would be inappropriate; increased speed without air supply could lead to catastrophic results. Thus, activating the emergency brakes is the most effective first response to address the loss of air supply in a train.