Buses and trains may trump cars on the carbon front, but for true sustainability, why not power public transit with alternative fuels? AC Transit has three hybrid-electric, hydrogen fuel-cell buses up and running in Oakland and surrounding areas, with plans to add 12 next-gen models to its fleet by the end of this year. Each diesel bus that is replaced saves 130 tons of carbon-dioxide emissions annually. Though fleetwide replacement isn't feasible until more cities commit to the technology, Chevron and the Department of Energy have invested in the project to demonstrate the viability of a hydrogen-powered system. And to stir public interest in the ultra-clean rides, the buses are moved among different routes. "Communities have been clamoring for these buses," says AC Transit's Clarence Johnson. "They run quiet and they burn clean, so they are always a welcome sight."