Platform edge doors are certainly NOT a bad idea BUT are they the first 'idea' we should be spending $$$ on? I suggest there are other more pressing needs though I see no reason why we always talk about doors as being an all-or-nothing situation. They are, surely, much more useful at busy stations where being pushed or falling on the tracks is sometimes a real possibility due to crowding. Why not a demo project of one or two stations??
There are a dozen or so stations that are associated with a lot of what I mentioned above.
They would yield the greatest return.
But you want ATC in place, so that means Line 2 Stations would have to wait.
Sheppard was built w/these doors in mind and I imagine the stations on the TYSSE were as well, so they should be low-cost re-fits.
At Yonge-Bloor I think they should be tied into the 1.5B reno set to occur, where the cost would hardly be a rounding error on that budget.
Though in the case of Y-B I strongly favour extending air conditioning to the platform levels at the same time. I had a friend who was heading home via subway late the other night and reported that Y-B, was overcrowded and in the heat people were feeling feint. Makes sense to me in stations low-ceilings and less capacity that experience crowding to add A/C.
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In terms of R.O.I, I think the investment in strategic stations would yields a fare bit of additional service, with no additional trains, a fairly worthwhile investment.
That does go down when you get to less beneficial stations, though it there are advantages in finishing entire lines in one go.