The nameless protagonist was struck by a car and killed just prior to the start of the movie.
The events of the movie are what his consciousness perceives as his brain fires off neurons randomly during the final seconds of his life.
- During one of the movie's many interminable monologues, the monologuer discusses the phenomenon of dreams that seem long and complex to the dreamer, but which only take up thirty seconds of time in the real world. (This editor also recalls, but can't be totally sure of, someone expounding upon the theory that brain activity can persist a short while after death.)
- The scene near the beginning of the film, where the protagonist rides in a boat-car, gets out, then gets hit by another car, is the protagonists' brain trying to process the events of his death. The fantastic elements of this scene, such as the boat-car and the note reading "look up", are fabrications of his dying brain.
- Not to natter here, I just rewatched this on Netflix, and I think I found the detail that negates this. In the train scene, the livery on the train isn't Am Trak - if you look closely, Wiley's train says it is a Dream Trak.
The nameless protagonist is just dreaming
The scene at the end is of him finally waking up, not dying.
- Ah, but he floats away again, suggesting that the dream continues. Yet this need not mean that he is dead. According to The Other Wiki, Bertrand Russell said that he experienced "about a hundred" false awakenings when he was anesthetized, and the same such repetition may be occurring here.