Has the United States passed peak car? It's one of the more tantalizing questions that energy and urban-planning nerds are pondering these days. Ever since the recession, Americans have been driving less, getting fewer licenses, and using less gas. But is that just the work of the recession, or something more permanent?

Yet a growing number of planners and transportation wonks believe the wave has crested and that, in the developed world at least, we have reached what they call "peak car." In many places, they note, vehicle miles traveled per person have declined steadily in recent years.

Some believe if we accept the notion of "peak oil", then we should also accept there'll be a moment of "peak car".

"I reckon we're at peak car now," John Cox says.