Really, if you're talking about new cities/neighborhoods, it should be done in parallel. If you wait until things are very dense to actually start planning goo

Really, if you're talking about new cities/neighborhoods, it should be done in parallel. If you wait until things are very dense to actually start planning good transit, that means you'll have many years where it's too dense for just cars and so things are borked, plus by then building tunnels or acquiring right of way will be much more expensive.