In which instance does a superior train take the siding?

A superior train taking the siding is a procedure governed by operational rules to ensure safe and efficient train movement. This action can happen under two specific circumstances: a train order or a signal indication.

When a train order is issued to direct a superior train to take the siding, it typically involves a pre-established agreement or plan between rail operations, ensuring that the superior train can pass another train safely. This is crucial in maintaining the overall scheduling and flow of traffic, especially in busy rail networks where multiple trains may operate on the same tracks.

Similarly, a signal indication may display instructions for a train to take the siding. This signal serves as a visual communication method conveying critical information regarding track occupancy and the need for a superior train to yield to other trains. Signals are a fundamental aspect of railway operation, providing real-time guidance and adherence to safety protocols.

Thus, both the issuance of a train order and appropriate signal indications are valid reasons for a superior train to take the siding, making the combined option the most comprehensive answer.