noun
elevated railway; overhead railway
Refers to a railway built on an elevated structure, such as a viaduct or bridge, rather than at ground level or underground.
この街には古い架空鉄道がまだ残っている。
An old elevated railway still remains in this city.
Compound of 架空 (かくう, 'aerial; overhead') and 鉄道 (てつどう, 'railway').