How to Build a Metro-Sized Moving Walkway

International architecture firm NBBJ recently unveiled a radical new concept for the London Underground’s Circle Line: a three-lane moving walkway. Commuters at each station would enter the slow lane at 3 miles per hour and then gradually pick up the pace by stepping into the adjacent lanes, at 6 and 9 mph. All three lanes would accelerate between stations, reaching a top walking speed of 15 mph in the outermost lane, before dialing back to slower boarding speeds at the next platform.

As imagined, this travelator (the British term for “moving walkway”) would replace the Circle Line’s entire 17-mile loop. NBBJ claims it would actually reduce travel times on the congested railway, since the sidewalk wouldn’t have to stop periodically like a train does.