现在,世界上已经出现的低噪声、无废气排放的交通工具有:有轨电车(包括地铁)、无轨电车、电瓶车和缆车;正在研制的有氢气汽车、太阳能汽车等。预计,以下几种将是未来城市的主要交通工具: 一是地铁和新型的无轨电车。它们将承担大部分客运量。二是以电力为能源的小客车、轿车和市内货车等新型电动汽车。这类电动汽车既具有先进的汽油车、柴油车所具备的工作性能,又具备生产成本低、易普及、耗能小等优点。这类汽车要解决的关键性问题是 Nowadays, the low-noise, non-emission vehicles that have emerged in the world are: trams (including metro), trolley buses, battery cars and cable cars; and hydrogen vehicles and solar cars under development are being developed. It is expected that the following will be the main vehicles for the cities in the future: First, the subway and the new trolleybus. They will carry most of the passenger traffic. Second, electric vehicles for energy-based passenger cars and sedans and other new electric vehicles within the city. Such electric vehicles not only have advanced petrol cars, diesel vehicles have the working performance, but also with low production costs, easy to popularize, the advantages of small energy consumption. The key issue to be solved by such cars is