What happens when all the fuel is gone?

Rising gas prices have again shifted the political debate between those calling for more drilling to meet America's fossil fuel dependency and those advocating for investment in alternative energy sources. Many environmentalists are convinced that we are nearing the day when fossil fuels are tapped out, or too expensive or too harmful to extract. A movement called Transition is planning for that future already, and talking about how to create Transition Towns. NHPR's Sam Evans-Brown caught up with a local organizer, appropriately enough, on a bicycle.