Abstract: There is described a hi-rail device for mounting on a vehicle, comprising a linkage between an axle assembly for holding wheels and a mounting assembly. The linkage, pivotally connected to an upper pivot connection thereof, is foldable and unfoldable to translate the axle assembly relative to the upper pivot connection. An active suspension between the linkage and the mounting assembly is provided and comprises a suspension body to swivel about the mounting assembly, actuated by a spring proximally urging on the suspension body to provide the swivel. The suspension body comprising the upper connection to the linkage, which can move along with the suspension body to provide active suspension. Also, a locking pin, extending through the linkage, can be locked in a slot using a hydraulic cylinder, distinct from a hydraulic cylinder for deployment, and which comprises a spring for default locking not involving hydraulic power.