Play around with maps at the H&T Affordability Site. Not very surprisingly, people who live (for example) in the city of Philadelphia drive less and have lower vehicle carbon emissions per household. Though not surprising, there is a weird tendency to equate environmentalism with being near nature when in fact the enviornmentalist thing to do is LEAVE NATURE ALOOOOONE and live a modestly-sized place in an urban hellhole with decent mass transit.
(via the overhead wire)
Though I live car free in my urban hellhole because I don't need a car and like my urban hellhole, not because of environmental concerns.