What does one red lantern on the right-hand side of the track signify?

One red lantern on the right-hand side of the track signifies a stop signal for the train operator. In railway operations, a red signal is universally recognized as an indication that the train must halt in order to ensure safety. This is critical for maintaining control and preventing accidents, particularly in situations where there may be hazards, obstructions, or other operational concerns ahead on the track.

While the other options represent important instructions in their own contexts, they do not convey the immediate and unequivocal command to stop that a red signal indicates. Understanding this signal is essential for train operators to ensure safety in their operations, following protocols in accordance with railway regulations and signaling systems.