Cars account for half the oil consumed in the U.S., about half the urban pollution and one fourth the greenhouse gases. They take a similar toll of resources in other industrial nations and in the cities of the developing world. As vehicle use continues to increase in the coming decade, the U.S. and other countries will have to deal with these issues or else face unacceptable economic, health-related and political costs. It is unlikely that oil prices will remain at their current low level or that other nations will accept a large and growing U.S. contribution to global climatic change.
汽车占美国石油消费量的一半，约占城市污染的一半，温室气体的四分之一。其他工业国家和发展中国家的城市也有类似的资源耗损。随着未来十年汽车使用量的持续增加，美国和其他国家将不得不处理这些问题，否则将面临无法接受的经济、健康和政治成本。油价不太可能保持在目前的低水平，其他国家也不太可能接受美国对全球气候变化的巨大且不断增长的贡献。
Policymakers and industry have four options: reduce vehicle use, increase the efficiency and reduce the emissions of conventional gasoline-powered vehicles, switch to less harmful fuels, or find less polluting driving systems. The last of these—in particular the introduction of vehicles powered by electricity—is ultimately the only sustainable option. The other alternatives are attractive in theory but in practice are either impractical or offer only marginal improvements. For example, reduced vehicle use could solve traffic problems and a host of social and environmental problems, but evidence from around the world suggests that it is very difficult to make people give up their cars to any significant extent. In the U.S., mass-transit ridership and carpooling have declined since World War II. Even in Western Europe, with fuel prices averaging more than 4 a gallon) and with easily accessible mass transit and dense populations, cars still account for 80 percent of all passenger travel.
政策制定者和行业有四个选择：减少车辆使用，提高传统汽油动力汽车的效率和减少排放，改用危害较小的燃料，或者寻找污染较小的驾驶系统。最后一项——特别是引入电动汽车——最终是唯一可持续的选择。其他替代方案在理论上很有吸引力，但在实践中要么不切实际，要么只能提供边际改进。例如，减少车辆使用可以解决交通问题以及一系列社会和环境问题，但来自世界各地的证据表明，很难让人们在很大程度上放弃汽车。在美国，公共交通乘客量和拼车自第二次世界大战以来有所下降。即使在燃料价格平均超过每升1美元（约每加仑4美元），公共交通便利，人口稠密的西欧，汽车仍占所有乘客出行的80%。
Improved energy efficiency is also appealing, but automotive fuel economy has barely made any progress in 10 years. Alternative fuels such as natural gas, burned in internal-combustion engines, could be introduced at relatively low cost, but they would lead to only marginal reductions in pollution and greenhouse emissions (especially because oil companies are already spending billions of dollars every year to develop less polluting types of gasoline).
提高能源效率也很有吸引力，但汽车燃油经济性在10年内几乎没有任何进展。在内燃机中燃烧的天然气等替代燃料可以以相对较低的成本引入，但污染和温室气体排放的减少很小（尤其是因为石油公司每年已经花费数十亿美元开发污染较小的汽油）。
