If brakes go into emergency from an unknown cause, what should the train operator do?

When brakes go into emergency from an unknown cause, the most appropriate action for the train operator is to lap the brake handle. Lapping the brake handle is a technique that allows the operator to maintain control over the braking system while investigating the situation. By lapping the brake handle, the operator prevents the brakes from fully releasing, which could lead to undesired movement of the train, while also allowing for a preliminary assessment of the emergency condition.

This method can provide necessary information on whether the situation can be resolved quickly or if further actions are required, such as additional emergency procedures. It essentially creates a balance between maintaining control and evaluating the cause of the emergency braking situation.

In contrast, other options would not effectively manage the emergency situation. Releasing the brake valve could lead to the train moving unexpectedly, creating safety hazards. Increasing the throttle is counterproductive during an emergency, as it would exacerbate the situation rather than address it. Activating the emergency brake can sometimes be redundant since the train is already in an emergency braking condition, and doing so may not yield additional benefits while potentially leading to complications. Thus, lapping the brake handle allows the train operator to properly assess and manage the emergency effectively.