I have seen a passenger sleeping on the floor in the unoccupied wheelchair space. I suppose the conductor would know whether anyone will be boarding for the handicapped seat during the night.- If you have a row of seats to yourself, it would theoretically be possible to sleep on the floor between rows of seats. However, you would need to be smaller in stature. Your car attendants may or may not allow it; to be honest I've never seen anyone try it before. I can say, though, that the attendants will not allow you to sleep on the floor in the aisle or in the handicap-accessible area.