Transportation regime shift

Transportation-wise, road/rail isn't either/or but rather an "and/also". Past a certain point, a central place can no longer boost/sustain its accessibility with cars alone and has to add rail. But that shift doesn't happen everywhere at once, and when you've got a regional governance structure, it takes a long time before it reaches a supporting political plurality. At first, the shift in the transportation regime only affects the most central areas, but over time it ripples outward.