地下铁道、轻轨交通、单轨铁路等统称为城市轨道交通。它具有运能大、速度快、噪音小、污染轻、能耗低等优点。因此,从二十世纪以来,世界各国许多大中城市,都在纷纷发展以轨道交通方式为骨干的城市客运交通网络。我国几个大城市,如北京、上海、天津、沈阳、哈尔滨等过去都曾使用过有轨电车,但后来由于技术落后,噪音大、影响交通,安全等原因,逐步拆除,现在只存下大连、长春和 Subway, light rail transit, monorail, etc. collectively referred to as urban rail transit. It has the advantages of large capacity, fast speed, low noise, light pollution and low energy consumption. Therefore, since the twentieth century, many large and medium-sized cities in the world have been developing urban passenger transport networks that rely on rail transit as the backbone. Several major cities in our country, such as Beijing, Shanghai, Tianjin, Shenyang and Harbin, used to use trams in the past. However, they were gradually dismantled due to backward technology, noisy noise, traffic and safety reasons, and now only Dalian Changchun and