When is it permissible to operate a hand brake?

Operating a hand brake is permissible when all crew members are positioned safely, as safety is the highest priority on rail operations. This ensures that everyone is clear of the moving parts and potential hazards associated with the operation of the hand brake. Having crew members positioned safely minimizes the risk of injury or accidents during this procedure, allowing for a safe and controlled use of the hand brake.

Other options do not emphasize the importance of crew safety or context, leading to unsafe practices. Authorizing use without ensuring safety could lead to accidents, and using the brake at any time or on uneven surfaces could create operational risks. Thus, ensuring all crew members are in a safe position is the correct protocol for operating a hand brake.