by which time rail travel was already on a steep decline.

Noted eco-grump James Howard Kunstler, in his book The Geography of Nowhere, makes a case that this was mostly a created decline, that (particularly in places like Detroit where they had a major presence anyway) the auto companies bought up public transportation utilities and deliberately ran them into the ground so as to create more of a market for cars in the lower income brackets. He lays out facts and figures for their role, but (it occurs to me) they may simply have accelerated a process that was already underway. I still consider it a violation of the separation of business and state, though. ^_^