①Over the past forty years，cars have become less polluting. Many people now drive electric cars（e﹣cars）. And there are fewer emissions（排放）from cars. However，cities such as London and Los Angeles are still fighting air pollution. Using cleaner cars is a good step，but is this enough？
②A survey shows that more than 40 percent of the cars only have one person inside. But a car trip takes a lot of electricity（电）. In the U. S，more than 60 percent of electricity still comes from fossil fuels（化石燃料）. So if all of us were to use e﹣cars，the emissions would only be cut down by 25 percent.
③And there are other things to be worried about. Roads and other systems for cars need a lot of space. About 24 percent of London's land（土地）has been used to build these systems. In many U. S. cities，this number can be as high as 40 percent. The World Health Organization advises cities to create at least 9 m' of green space for each person. However，in many fast﹣growing cities around the world，each gets less than 2 m' because they have to use more land for roads and parking.
④So，using cleaner cars is not enough to make our cities better. In fact，cities need much fewer cars. People should have different ways to get around. Studies show that people will get out of their cars if they have more and better ways to choose. Only then will our cities become faster and greener.
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