There's an often-missed angle on public transit: total transit time. has to go up with public transit, including trains, That means you're asking everybody taking them to spend possibly alot more time to go anywhere. My wife doesn't mind, but I do.
Money quote: "In NYC, it seems to take roughly 50 minutes to get anywhere by public transit, more like an hour by car, and the car costs more. Thus, in NYC, it makes sense to take transit. In the medium-size city where I live, it takes 20-30 minutes to drive places. Even if we had NYC-level transit, it'd take a lot longer to go that way."
I'm all in favor of public transit - I figured this stuff out by, well, taking alot of every kind of public transit, and it served me well within its limits. I just want to get one of those limits out in public a bit.
Like Paladin, that's made me also feel like transit rail has some realistic low-end density requirements to be of much help.
While I'm at it, notice that having 15-minute busses is alot cheaper than rail, because you already have lanes in place. And it'd prolly be easier to adapt Detroit to changing to. But you still need reasonable density or you just get lots of empty busses.