一、现状与必要性目前,随着国内城市化进程的不断深化,城市交通拥挤状况越来越严重,不仅影响居民的出行,更进而影响到了整个城市的正常运作秩序。城市轨道交通拥有大运量、安全快速、节能省地等优点,近年来受到各大城市的重视。目 I. Current Situation and Necessity Nowadays, with the continuous deepening of urbanization in China, the urban traffic congestion is getting worse and worse, which not only affects residents’ travel, but also affects the normal operation order of the entire city. Urban rail transit has a large capacity, safe and fast, energy saving and other advantages, in recent years by the major cities of attention. Head