I may be a lone voice of dissent, but I don't like centre platforms. Yes, they're cheaper, but that doesn't automatically make them better. I don't agree with the idea that centre platforms have better circulation since when both directions' trains are accessed from the same platform, you're going to have more complex circulation patterns and conflicts. It is simpler to navigate, sure, but crowd control is inferior.
I don't like not having a wall on one side of the platform. This is important when it gets crowded. If it is crowded both ways and there's no wall to take refuge, the risk is greater of someone falling to track level with centre platforms. Centre platforms are also notrious for being narrow around stairways, a situation side platforms are quite good at avoiding. Side platforms also don't require columns along them (since the columns typically end up between the two tracks). This leaves centre platforms with less area than side platforms, and are lower in capacity because both directions share the same elevator, escalators, and stairs (even though they're wider, they're not twice as wide).
I think that, if the subway can be kept shallow enough, that ramps be put in instead of elevators and escalators. That keeps maintenance costs waaay down. It requires the subway to be shallow though, a key clause.
Also, I think that, if following certain streets, some parts in the west part of the core may be forced to stack the two directions one on top of the other due to space constraints (some streets get smaller as they head west).
). Of course, it's cheaper because only one elevator is needed, which will also mean lower maintenance costs.
