In “The Roads Must Roll" Heinlein postulates a set of roofed conveyors, equipped with variable speed strips, that run long distances across the country. A person rides the 'roads' by getting on a slow strip at the edge and transferring (by walking) to strips of increasing speed; the center one rolls at 100 miles an hour. It’s a bold concept, conceived ten years before the rapid development of commercial air traffic and the Interstate highway system.
That's 1959. Herbert George Wells came up with this exact idea a few decades earlier (in "When the Sleeper Wakes").