城市轨道交通是城市公共交通的骨干。它具有节能、省地、运量大、全天候、无污染（或少污染）又安全等特点，属绿色环保交通体系，符合可持续发展的原则，特别适应于大中城市。城市轨道交通种类繁多，按照用途可分为城市铁路、市郊铁路、地下铁道、轻轨交通、城市有轨电车、独轨交通、磁悬浮线路、机场联络铁路、新交通系统等。
Urban rail transit is an all-encompassing term for various types of local rail systems serving urban or older suburban areas. The vast majority of modern urban rail vehicles run on electricity. The set of urban rail systems can be roughly subdivided into four categories, which sometimes overlap, causing some systems or lines to have aspects of each。
From Wikipedia