[zimpenfish]

It's not just that - it's the delay whilst people hold the doors, get their bags/umbrellas/coats/legs stuck in them, etc. With the (over)tight scheduling of the timetable, one train being delayed by a minute can cause a knock-on for a considerable time.

I guess (though I don't use the tube, I can't verify) that the platform-side doors help control this kind of behaviour.

(There was a link going round a year or two ago about (IIRC) New York improving service reliability by reducing the flow and introducing slack into the timetable but I can't currently find it. Lots of academic research into this topic though.)

[RossM]

One of the side effects is that it allows people to queue in the right spot (rather than guessing and lining the platform) which helps even out the number of people trying to get in one set of doors. Adding a bit of predictability helps streamline things.

[Danieru]

You see this behavior in the Tokyo metro system. Even better the doors are numbered so people will learn which car is closest to the exit they need. This provides a clean stream of passengers heading to the nearest exit.

[zimpenfish]

I guess if you also annotate the platform with "queue here" lanes (I've a vague memory that some Jubilee stations have this?) then you can try and keep the queues from blocking people leaving the train.

[buttscicles]

There are white squares on certain Hammersmith & City and Circle and line platforms that line up with where the doors stop, people don't seem to know this though.