複線

multiple track (e.g. rail) / multilane (e.g. highway) / (math.) complex line

to repeat / to double / to overlap / complex (not simple) / compound / composite / double / diplo- / duplicate / overlapping / to duplicate

thread / string / wire / line / CL:條|条[tiao2],股[gu3],根[gen1] / (after a number) tier (unofficial ranking of a Chinese city)