London has the oldest subway system in the world: great for tourism, but sometimes not-so-great for commuters. There's all sorts of sensible plans to upgrade the city's public transport, but here's one particularly outside-the-box solution: a 24kph moving footpath, looping 27 kilometres under London. What could go wrong!
Architecture firm NBBJ has come up with the plan, which involves replacing the Circle Line, a loop that runs underneath most of central London, with a set of moving footpaths. There would be three footpaths side-by-side: the slowest 'feeder' lanes on the outside, with the 24kph superhighways in the middle.
There's some logic in the madness: you'd never have to wait for a train, and the maximum capacity of the line would increase to the point where it could maybe handle rush hour.
On the other hand, you'd kill every person with a stroller, large backpack, or wearing high heels; the other subway lines that share track with the Circle line would have some issues; and just imagine how bad the tourists would be on it.