What does an interlocking refer to in train operations?

An interlocking in train operations refers specifically to a system where signals and switches are controlled in a manner that ensures safe train movements on the tracks. This control is crucial for preventing conflicting train movements and ensuring that trains do not enter areas of track that could lead to accidents. Interlockings can be controlled from a centralized location, often referred to as a control tower or signal cabin, which monitors the positioning of switches and the status of signals.

The design of an interlocking system ensures that only one train can occupy a section of track at a time and that switches are set correctly before a train is permitted to proceed. This is fundamental for maintaining safety in complex rail systems where multiple trains operate simultaneously.

The other options provided do not accurately describe the term "interlocking" in the context of train operations. A route plan for a train operator's shift pertains to scheduling rather than safety control mechanisms. A type of safety protocol for train maintenance relates to upkeep practices but does not define the function of interlockings. Lastly, a communication method for train dispatchers concerns the communication systems used to coordinate train movements but does not encompass the physical and operational safety functions of interlockings.