[frobozz]

Platform overcrowding is also an issue, and passengers are often held back in the ticket hall or outside, because of how dangerous it would be to put more people on an open platform.

With platform-side doors, you don't need to stand behind the yellow line.

It isn't just one-unders, but the fact that the train can't safely move off when there are passengers right up against the train.

[iaskwhy]

Canary Wharf station has platform-side doors but it still closes the entry at ticket hall level every now and then. One advantage for me is the line formed in front of the platform doors which allows me to wait in front of it for the next train and find a free seat every day.

[davedx]

I remember being blown away by the platform side doors for the shinkansen bullet train in Japan: the incredible precision with which the train doors align with the platform doors.

[lmm]

Where was that? Most shinkansen platforms I've been on were in the open air.

(Also, London has had platform edge doors for a while already - only on half of one line, but still)

[davedx]

Not sure... one of the Tokyo stations I think. It was still an open air platform, but had doors on the edge of the platform around man-height that aligned with the train doors.