The orange coloured device on a boom is the welding head suspended between the main and trailing units. It may be raised, lowered, and swivelled left or right. Massive hydraulic actuators grip the rail, stretch it, then hold it while being welded. The entire rail welding unit is blocking the grade crossing. Normally this wouldn't be done but it was a lightly used gravel road and they needed access for a fuel truck to refuel. When a vehicle arrived and wanted to cross the track, rather than move the whole unit, the welding head was swung out of the way and the vehicle passed through the gap between the main unit and trailing unit.