The stopping position of the TTC subway train (the counterclockwise / westward movement) stops at highly variable positioning at TTC Union station.
I walked down the platform and found that the number of constricted doors varies by as much as 2. There is an ideal train stopping position that has 2 fewer constricted doors.
Perhaps TTC could optimize precision berth stopping position to speed up passenger embarkation/disembarkation. At peak, there's a bottleneck that actually adds 5 seconds to boarding depending on exact train stopping position.
Unconstricted stopping position
Constricted stopping position (there's a second simultaneous blockage down the platform too)
Same standing position, same pillar, different position for same open door (7th set of doors from eastmost end of train)! There are other mini-blockages down the platform too, that increase/decrease in number, so there's an optimized stopping position at Union (eastward-moving trains, from Yonge towards University) that has 2 fewer blocked doors (total).
Two consecutive trains, minutes apart -- but stopped several meters different. These are offpeak photos, but the TTC train empties/fills noticeably faster (on average) at certain berth positions than others -- this actually can matter at peak period once the trains are made to run at sub-2-minute headways.
Often passengers wait in the cubby depressions (walls) between the pillars, or just around the pillars, blocking disembarking passengers, noticeably slowing passengers down. Blocking fewer doors overall speeds up the whole-station passenger flow slightly, saving 5-10 seconds at certain stopping positions -- not insignificant in the future era of sub-2-minute headways.
Also here's a generic diagram (non-TTC) that demonstrates train-positioning "Geometry Theory" (three door version). This still even applies to any subway system whose has stations with constricted stopping positions, and any number of doors (2, 3, 4) or coaches, it demonstrate the Geometry 101 concept.
(Above is generic non-TTC diagram, but demonstrates the Geometry 101 concept of stopping-position optimization)
There's a lot of jiggle room (about 5 meters worth). Perhaps the automatic train control system can be precisely adjusted for optimal "fastest-peak-passenger-flow" train stopping position at TTC Union station.
It is amazing how much the train stopping position varies at Union station -- the ATC system can in theory be programmed to aim to stop at a very precise default berth position -- that optimizes for slightly faster commuter flows (disembarkers easily getting around embarkers -- versus constrictions preventing such).
