I probably came across this at Ian Visits blog. This manner of moving people never caught on and I am not really sure why. The same principle is used to get trains up and down steep hills, called a cog railway or rack and pinion but in reverse as the fixed part is on the track and the moving part within the train.
The spacing of the spiral adjusts the speed of the train, so at the station the spiral would be finer than when speed was required away from the station.
It is worth reading the blurb below the clip if you want an explanation of why there are so many exotic people in the London footage. Open the clip in You Tube to do so. Astonishingly, it was so easy, even women could manage to use the train. At 1.04 you can see a bloke having a bit of a muck around. At 1.15 on you can see the spiral in operation.