Jeff is making an important, but unappreciated point - you can’t just build transit out to exurbs and expect to end up with New Urbanist landscapes. Transportation is one component of density, but the economics also need to work. Dense developments cost more, and developers aren’t going to bear that extra expense in places where home prices aren’t high enough to recover those extra costs. All the pretty drawings in the world won’t change that.
And this is true even if the transit line is fast. Even if you build souped up BRT or express rail, all you’re going to do is generate a suburban park-and-ride market. Now that’s arguably better than having those folks commute on the freeway (and it might help keep commerce in the core) but cities need to be honest with themselves, and recognize that that’s what they are doing. Too many cities think they are creating the next Arlington by slapping BRT on an artery in the outer ring.