I left this comment hanging for some reason, but here it goes. >Why do you worry about energy usage? It's not just CO2, but energy in general. If it never bec

I left this comment hanging for some reason, but here it goes. >Why do you worry about energy usage? It's not just CO2, but energy in general. If it never becomes arbitrarily cheap, it will always be a constraint. Also vehicle production, since steel might become a scarce commodity. >the effect of various kinds of traffic on the shape of living Definitely. This century of individual transportation has had cheap energy and vehicle production on its side. Besides, ubiquitous pavement and city planning have been forced into fitting the idea that it is a good thing.