As discussed by experts the best alternative fuel as a bridge to cleaner transportation is CNG (Compressed Natural Gas). Not only is CNG a cleaner alternative fuel than oil based natural gas but is found in abundance in the good old USA. Another great thing about using natural gas as an alternative fuel is that it can easily work with gasoline based engines. Add a tank and a few other modifications and you have an alternative fuel vehicle.
Another reason why many experts say Compressed Natural Gas is the preferred alternative fuel for the transportation industry is because the same system for a CNG Car can also be used for another hopeful alternative fuel, hydrogen fuel cells.
Economically CNG Cars also make the most sense. Not only is the alternative fuel Natural Gas in abundance in North America, but it is already widely available to most homes throughout the United States. This alternative fuel is already being pumped into the majority of US homes that use it for heating.