Road bed is the subgrade on which are laid the ballast, ties and rails.

路基就是上面铺着道渣，枕轨和钢轨的底基。

youdao

Road bed is the subgrade on which are laid the ballast, ties and rails.

路基就是上面铺着道渣，枕轨和钢轨的底基。

youdao