Although the red light is meant to signal approaching trains and is part of a safety system intended to prevent railway accidents, the signalman ironically dies near the red light, and assumedly, partially because of the red light. The story describes this positioning:
“He had struck the light, and had the lamp in his hand. As the engine came out of the tunnel, his back was towards her, and she cut him down.”
The narrator’s skepticism often leads him to believe that he has all of the answers and the firmest grasp on the situation as an objective, unbiased outsider. Ironically, it is this misplaced certainty that leads him to leave the signalman alone, which—in some ways—leads to the man’s death. In this passage, the narrator claims that the signalman understands his duty, but, in reality, the signalman’s sense of duty has been skewed by his guilt over the previous tragedies as a result of his encounters with the ghosts:
Unlock with LitCharts A+Therefore, setting aside all question of reality or unreality between us, I represented to him that whoever thoroughly discharged his duty must do well, and that at least it was his comfort that he understood his duty, though he did not understand these confounding appearances. In this effort I succeeded far better than in the attempt to reason him out of his conviction. He became calm; the occupations incidental to his post as the night advanced began to make larger demands on his attention: and I left him at two in the morning.