地铁 metro/underground railway/subway

城市轨道交通 urban rail transit/mass transit

设计使用年限 designed lifetime

运营概念 operation concept

旅行速度 operation speed

限界 gauge

正线 main line

辅助线 assistant line

联络线 connecting line

试车线 testing line

轨道结构 track structure

轨距 gauge of track