城市轨道交通(Urban Rail Transit,URT)具有运量大、速度快、时间准、污染少、交通事故少等独特优势。由于大城市普遍存在交通拥堵、环境污染和土地资源短缺等问题,因此,大力发展URT已经成为各大城市解决这些矛盾和问题的有效途径。然而,URT是一个带有较强公益性的 Urban Rail Transit (URT) has the unique advantages of large capacity, fast speed, accurate time, less pollution and fewer traffic accidents. Due to the prevalence of traffic congestion, environmental pollution and shortage of land resources in major cities, the vigorous development of URT has become an effective way to solve these contradictions and problems in major cities. However, URT is one with a strong public interest