With transport accounting for more than 30% of U.S. carbon dioxide emissions, one of the best ways to reduce them is by riding something many of us haven't tried since the ninth grade: a bus. Public transit saves an estimated 1.4 billion gal. of gas annually, which translates into about 14 million tons of CO2, according to the American Public Transportation Association.

Unfortunately, 88% of all trips in the U.S. are by car. Partly, that's because public transportation is more readily available in big urban areas. One promising alternative is bus rapid transit (BRT), which features extra-long carriers running in dedicated lanes. Buses emit more carbon than trains, but that can be minimized by using hybrid or compressed-natural-gas engines. A study last year by the Breakthrough Technologies Institute found that a BRT system in a medium-size U.S. city could cut emissions by as much as 654,000 tons over 20 years.

Thanks to high gas prices, miles driven per motorist dropped in 2005 for the first time since 1980, according to the Pew Research Center. The U.S. is ready to change. We're just waiting for the bus.