"Cars will not define cities of the future"

"The age of the highway city is over, we can't afford it, and it's not desirable," said Peter Calthorpe, speaking at Fortune's Brainstorm Green conference in Laguna Niguel, California. Calthorpe argues that as more of the world moves into urban environments -- he says there will be 3.5 billion people living in developing world cities by 2025 -- they will want fun, livable urban places. Cities can be all those things, he says, without being designed with cars in mind.