7. 液化或压缩天然气

    使用液化或压缩天然气的天然气汽车的续航里程和汽油车相仿，但燃烧更清洁。美国环保部（the Energy Department）估计，目前全美在用天然气汽车共有112,000辆。它们大多数是中型或重型卡车，但本田汽车（Honda）1998年就已经推出了天然气版的思域（Civic）。它比汽油版速度慢，行驶里程有限，加注网络也不完善，同时还要贵上好几千美元。有利于它推广的地方在于，这种燃料更便宜，在国内生产，排放也更低。

    7. Liquefied and compressed natural gas

    Natural gas vehicles, operating on either liquefied or compressed gas, produce mileage similar to gasoline but burn more cleanly. The Energy Department estimates that some 112,000 vehicles powered by natural gas are currently in operation. Most are medium and heavy-duty trucks, but Honda (HMC) has offered a natural gas Civic (above) since 1998. It is slower than a gasoline one, has a limited range and refueling network, and costs thousands of dollars more. In its favor are cheaper prices for a fuel that is produced domestically and lower emissions.