Public transportation is leading the way in green vehicles, says the American Public Transportation Association. As of two years ago, 35.6% of all the public transit buses in the United States were alternatively powered – 18.6% used natural gas, 8.8% were hybrids, and 7.9% of public transit buses used biodiesel. Propane is a new, emerging fuel, APTA said, and CNG buses play a very important role.