alt Hacker NewsThe main low-hanging fruit is just removing surface parking lots in American downtowns and stopping the development and expansion of highways through the same. If you did nothing else that would have a significant positive impact. For almost all communities those surface parking lots are economic extracts from the community. They're woefully underpriced for tax purposes too.
Maybe the parking lots, but if you know anything about the major Japanese cities with satisfyingly good train systems then you'll also know they have a lot of expressways running through them.