根据联合国环境规划署最近的一次报告，如果汽车数量保持现在的增长速度，到2025年，汽车总数将超过10亿辆。现在，机动车每年排放9亿公吨的二氧化碳，约占二氧化碳总排放量的15%。更多的车辆将意味着更严重的全球变暖。同样，到2025年，世界三分之二的人口将在城

According to a recent report by the UNEP, if car numbers keep increasing at the present rate, there will be more than a billion on the road by 2025. Today, motor vehicles put out 900 million tones of carbon dioxide a year--about 15 percent of our total output. More vehicles will mean more global warming. Also by 2025, two-thirds of the world’s people will live in cities, so traffic jams and pollution will loom large in most people’s lives.