Supernatural - Season 2, Episode 16, Roadkill
Molly and her husband are driving along a long deserted highway at night when they come upon a farmer. The next thing Molly knows both the husband and the farmer have disappeared. Things get worse when the Winchesters inform Molly that the farmer is actually a highway ghost who, it seems, appears annually to claim a new victim, who happens to be Molly this time. Molly is actually the driver of the vehicle who killed the farmer and his wife and is dead herself but doesn't know it. Her husband David survived the accident, and when faced with the truth Molly is able to move on.