The Circle Line is one of London's oldest subways, having been started in 1863. Unlike other London lines, it is fairly shallow and close to the surface. It's also notorious for its unreliability. Now the big American architectural firm, NBBJ, has proposed replacing the trains with a system of moving sidewalks. They say that it would actually be faster than the trains because there is no waiting, and would increase capacity. According to the Independent,
It takes about an hour for tube trains to circuit the Circle Line at present. The travelator would reduce that time by several minutes by not stopping at stations. Instead, passengers step onto 'feeder' walkways that move at 3pmh. This would feed into a slow lane, that accelerates to 6mph and 9mph in lit tunnels. The firm said there would also be a 'middle lane', coloured orange, with a top speed of 12mph, and a 15mph red 'fast lane'.
Now variable speed moving sidewalks are a subject I know something about, having tried to patent one when I was seventeen. Handrails are a must or people will be falling all over the place. They are surprisingly hard to design when there are multiple speeds involved. But everything else about the idea makes tremendous sense; the capacities are huge and people can walk on them as they move, increasing their speed and getting some exercise.
I do like the way that they have proposed restaurants and other uses along the way. This could be a lot of fun. According to Designboom,
The design team say that the scheme would result in considerably quicker, more enjoyable and healthier journeys. Intended to promote new ideas for urban mobility, the scheme was developed with a view to inserting an element of fun into traveling on the underground, for tourists and Londoners alike.
There are a number of ways to do variable speed moving walkways; ThyssenKrupp has developed one that runs on linear induction motors and goes from 3 MPH when you get on up to 9 MPH at full speed. I videoed an earlier version at Toronto's Pearson Airport, that can does the 950 feet between terminals in 90 seconds. The handrails are like little carts running on the track, that get closer together as the sidewalk slows.
NBBJ's proposal, with different belts running at different speeds, is less complex and gives the user more options. There are a lot of problems to solve, but it's a great idea. Just hang on.