"They glided down an electric staircase, and debouched on the walkway which bordered the north-bound five-mile-an-hour strip. "Have you ever ridden a conveyor strip before?" Gaines inquired. "It's quite simple. Just remember to face against the motion of the strip as you get on...They threaded their way through homeward-bound throngs, passing from strip to strip...After passing through three more wind screens located at the forty, sixty and eighty-mile-an-hour strips, respectively, they finally reached the maximum speed strip, the hundred mile and hour strip, which made the round trip, San Diego to Reno and back, in twelve hours."
Robert Heinlin, "The Roads Must Roll" (1940). Silverberg, Robert, ed. The Science Fiction Hall of Fame, Volume One, 1929-1964, New York: Tom Doherty Associates, 1970.