What procedure is necessary to take an interlocking or CP signal out of service?

Taking an interlocking or CP signal out of service involves specific procedures to ensure safety and communication with train operations. Using a Bulletin Order or Form D line 7 is correct because this officially documents the action of taking the signal out of service. It communicates critical information about signal status and any associated restrictions or conditions that train crews must be aware of, thus maintaining safety protocols across the rail system.

The other options involve important aspects of rail operation and safety but are not the correct procedures specifically for taking a signal out of service. For instance, having a signal operator present relates to signaling operations but does not substitute for the formal documentation required by a Bulletin Order or Form D. Notification of all train crews is crucial for safe operations, but without the official documentation of the signal’s status change, train crews would lack the necessary authoritative notice. Finally, ensuring all trains stop at the signal might be a safety precaution, but it does not fulfill the procedural or regulatory requirements necessary for taking a signal out of service.