noun
double track; two-track line
Refers to a railway line with two sets of tracks, allowing trains to run in both directions simultaneously.
この区間は複線化の工事が進んでいる。
Construction to double-track this section is underway.
複線のため、列車のすれ違いがスムーズだ。
Because it's a double-track line, trains can pass each other smoothly.