Under what condition can cars with defective air brakes be tagged?

Cars with defective air brakes can be tagged only when they are moving to repair facilities. This condition is important because it allows for the safe movement of defective cars to a location where they can be properly inspected and repaired. Tagging a car indicates that it is not fit for regular service, ensuring that crew members are aware of its condition while it is being transported.

In operational scenarios, moving defective cars directly to repair facilities minimizes the risks associated with operational failures due to air brake issues. It keeps the trains safe and maintains system efficiency by ensuring defective cars are dealt with promptly and in designated areas equipped for repairs.

Other conditions, such as cutting the brakes out during a journey or inspecting cars at terminals, do not provide a clear mechanism for ensuring safety while allowing for movement. Furthermore, stating they cannot be tagged at any time overlooks the critical procedure and protocol necessary to manage defective equipment effectively.