Write to your city representatives to request that your community upgrade their diesel buses to fleets of electric or biodiesel buses. This will reduce the CO2 emissions generated, reduce dependence on imported oil dependency, and in the case of biodiesel engines actually run cleaner and more efficient than petrochemical diesel. Even diesel buses are worth getting on. We calculated that buses only need to carry 3-8 people to break even with a car on CO2 emissions.