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本世纪上半叶,有轨电车是世界上各大城市公共交通工具的主角。五十年之后,随着汽车技术的进步,各种燃油汽车日渐风行,有轨电车逐渐被挤出城市居民生活圈外,如今在世界各大城市中已难以再见到有轨电车的身影了。燃油汽车不受固定车轨的限制,的确灵活方便。但它带来的尾气和噪音对环境的危害也日见加深,汽车越多的国家对此感受越深。据统计,目前世界上约有2.5亿辆大小汽车在行驶,其中一半以上集中在各大
The first half of this century, the tram is the protagonist of public transport in major cities in the world. Fifty years later, with the advancement of automobile technology, various types of fuel vehicles are becoming increasingly popular. Trams are gradually being squeezed out of urban residents' lives and it is hard to see the tram in the world's major cities anymore. Fuel cars are not limited by the fixed rail, indeed flexible. However, the harm it brings to the environment and the exhaust gas is also deepening day by day. The more countries with cars, the more they feel about it. According to statistics, there are about 250 million cars in the world at present, of which more than half are concentrated in major