Complex sentence: "The Roads Must Roll" is a 1940 science fiction short story by Robert A. Heinlein about wide, rapidly moving passenger platforms (like moving sidewalks, but much faster-topping out at 100 mph).
Split into simpler sentences: The Roads Must Roll is a 1940 science fiction short story by Robert A. Heinlein. The story is about wide, rapidly moving passenger platforms (similar to moving sidewalks, but reaching speeds of 100 mph).