What authority is required for a train to move in the opposite direction of the established traffic?

The authority required for a train to move in the opposite direction of the established traffic is conveyed by an interlocking signal indication. Interlocking signals are designed to ensure safe train movements and provide precise authority for actions that may conflict with normal operations, including movements against the normal traffic pattern.

When an interlocking signal displays an indication that permits a train to move in the reverse direction, it indicates that the track is clear and that such movement has been sanctioned in a controlled manner. Therefore, the indication from interlocking signals provides the necessary authority and safety assurance for these atypical movements.

While other options may involve aspects of train operations and signaling, they do not specifically cover the authoritative context needed for trains operating in the reverse direction. Proper adherence to interlocking signal indications is crucial for maintaining safety and preventing potential conflicts with other trains on the system.