[Symbiote]

I think everyone will agree the curved platforms on the London Underground are a problem. So far, no engineer has found a suitable solution.

I'd hesitate to call it a "design flaw" though, bearing in mind the design for these stations was from the 1880s-1910s. There were much different requirements then: far fewer passengers were expected, all of them able-bodied and most of them locals. It's clearly a compromise, as it allowed the station to be where it was wanted rather than on a straighter section of track.

I don't know what alternative there is to escalators — lots and lots of lifts?