I'd assume it's so that if something's left leaning against the button, the doors no longer unexpectedly open at the next station. For an extreme example, if an ill-mannered family got on the train, piled up a mountain of suitcases leaning against the doors and resting on the button: the train pulls into Tottenham Hale, and the luggage could spill out over the platform while the owners are obliviously half a train carriage away.
Workarounds to this could be to have there be a maximum time the button can be held before it is considered unintentional - say 20 seconds. Or to only open the doors when automatically released if the button has been held for less time than that. (These may be the same logic but just applied inverse.)
In either case, I think if we have luggage piled up by doors that also serve as emergency exits, and could be opened manually by someone outside that then has that luggage fall on them, the problem is probably not the function of the buttons.
Have you done train toilet doors yet? You definitely should. The number of hapless inexpert travellers (often tourists) caught in the act is a national scandal!
I suspect the change is more to do with the technology than with accessibility.
On older trains the tech is much simpler - simple button closes the circuit, if doors are powered - which is controlled by a master switch - then they open or close. On some old trains (I believe the venerable ex-508 carriages within class 455s?) this could even mean that letting go of the open button too early would see the doors close again!
On newer trains the buttons will be part of a digital control system, where a button press sends a request to a controller, which makes the decision in software as to what action needs to be taken. This allows for, among other things, more sophisticated selective door opening (SDO) so that, for example, individual sets of doors with a carriage can be kept closed at specific stations, rather than the whole carriage having to be locked out.
Anyway, in my view, the best solution is the one you mentioned on the trams - on approach to a station, a button press should show some kind of green flashing response to indicate that the door will open automatically as soon as the train has stopped. But this isn't as simple as it sounds - you do want to limit this capability to just station approaches, particularly for longer distance trains with longer times between stations. Otherwise there are risks from accidental/unwanted presses.
And I was also always a "holder", not a "waiter" (nor a frustrating "tapper") and I miss being able to reliably hold the button on newer trains.
I'd assume it's so that if something's left leaning against the button, the doors no longer unexpectedly open at the next station. For an extreme example, if an ill-mannered family got on the train, piled up a mountain of suitcases leaning against the doors and resting on the button: the train pulls into Tottenham Hale, and the luggage could spill out over the platform while the owners are obliviously half a train carriage away.
Workarounds to this could be to have there be a maximum time the button can be held before it is considered unintentional - say 20 seconds. Or to only open the doors when automatically released if the button has been held for less time than that. (These may be the same logic but just applied inverse.)
In either case, I think if we have luggage piled up by doors that also serve as emergency exits, and could be opened manually by someone outside that then has that luggage fall on them, the problem is probably not the function of the buttons.
Have you done train toilet doors yet? You definitely should. The number of hapless inexpert travellers (often tourists) caught in the act is a national scandal!
I plan to at some point!
I suspect the change is more to do with the technology than with accessibility.
On older trains the tech is much simpler - simple button closes the circuit, if doors are powered - which is controlled by a master switch - then they open or close. On some old trains (I believe the venerable ex-508 carriages within class 455s?) this could even mean that letting go of the open button too early would see the doors close again!
On newer trains the buttons will be part of a digital control system, where a button press sends a request to a controller, which makes the decision in software as to what action needs to be taken. This allows for, among other things, more sophisticated selective door opening (SDO) so that, for example, individual sets of doors with a carriage can be kept closed at specific stations, rather than the whole carriage having to be locked out.
Anyway, in my view, the best solution is the one you mentioned on the trams - on approach to a station, a button press should show some kind of green flashing response to indicate that the door will open automatically as soon as the train has stopped. But this isn't as simple as it sounds - you do want to limit this capability to just station approaches, particularly for longer distance trains with longer times between stations. Otherwise there are risks from accidental/unwanted presses.
And I was also always a "holder", not a "waiter" (nor a frustrating "tapper") and I miss being able to reliably hold the button on newer trains.