A rail unloading vehicle is self-propelled and able to travel either over-the-road on conventional roadway tires or along railway tracks on railway wheels. Threading mechanisms for unloading the rails are arranged to retract so they provide a narrow profile for transport over the road. The threading mechanisms have thread boxes with jaws that open to accommodate easy reception of rails, and close to apply rollers to the rails for unloading operations. A special rail clamp has a pair of oppositely pivoting dogs to allow rail manipulation in opposite directions without slippage. A special saw allows safe on-site cutting of rails.