Wrong Track.
Wrong Track is a short story from Sex & Violence.
Plot
Wrong Track is the second story, which picks up soon after. Eddie is riding the train. His internal monologue explains that he had a flat tire. Delia hits on him, and they make love near the back of the train.
When they're done, she snaps his neck and throws him off the train. Leaving the rear of the train, the Colonel waits for her. "Delia-- do you plan to make love to each and every one of them?" he asks. Her response is "Only the ones I like."