noun
maintenance train; railway maintenance vehicle
A railway vehicle used for track inspection, repair, or other maintenance work.
夜間、保守車両が線路の点検を行っている。
At night, a maintenance train is inspecting the tracks.
保線車両 is a more specific term for track maintenance vehicles, while 保守車両 can refer to a broader range of railway maintenance vehicles.
Compound of 保守 (maintenance) and 車両 (vehicle, rolling stock).