The Narrator's Skepticism (Situational Irony)
After the signalman discloses his experience of being haunted, the narrator is skeptical. He suspects the signalman is turning coincidences into hallucinations and might be mentally ill. But in an instance of situational irony, when the narrator returns to the rail cutting at the end of the story, he learns that the signalman died in precisely the way the specter predicted. Because the signalman's hallucinations proved prophetic, the narrator cannot know whether it is yet another coincidence or evidence of the power of supernatural forces.
Decoding Signals (Situational Irony)
Though the signalman works diligently and carefully at his job of decoding telegraph messages and passing signals down the train line, when the spectral figure visits to warn of impending harm, the signalman is unable to decode the specter's ambiguous messages. The struggle to interpret the imminent harm causes the signalman to grow sallow and haunted. Ultimately, he loses his life on the train tracks, having been unable to understand that the messages were predicting his own death.
