Many options exist to power light-duty vehicles, which include cars, SUVs, and small trucks. Most vehicles are now powered by the combustion of gasoline, and diesel fuel is becoming increasingly common. As the transportation industry moves toward using cleaner fuels, natural gas is receiving serious consideration. Natural gas as well as biofuels and electricity from batteries or fuel cells serve the goals of improving energy efficiency, reducing or eliminating greenhouse gas emissions, reducing the cost of operating vehicles, and diversifying the available energy sources.