I think it's been years that I've had this idea in my head, of visually representing the relationship between the various goals I described in my previous post. I've tried it on paper, and it gets very complicated very quickly, so here's the basic cycle:
Quite simply, government priorities are the primary factor in the relative quality of transportation modes (transit, driving, walking, cycling). This in turn influences individual choice of mode, and individual choice influences government priorities. If your ultimate goal is transportation for all, then improving the quality of transit is your best bet. If your ultimate goal is ending global warming, reducing resource waste or building better social structures, however, you need to work on changing choices, and there are more factors involved there.
My apologies for the crude Microsoft Paint diagram. If anyone wants to redo this in a nicer-looking way, or can suggest a free or low-cost program for creating diagrams like this, please let me know.