More fun historical facts for @bashful, @dmpalmer , @Scott_K, ect…
At the turn of the century Paris had a version of the slidewalk with different speed bands.
This shows up later as a plot device in the The Roads Must Roll by Robert Heinlein and SF furniture for a chase sequence in the The Caves of Steel by Issac Asimov.
Apparently there was a proposal in Atlanta to build something closer to the fully developed slidewalks from the Golden Age of science fiction…
I suspect thermodynamics would render any such mass transit system impractical given the inefficiency of continuously moving such colossal platforms, but it’s such a fun idea. 
