Specialist engineering vehicles include bomb-disposal robots and the modern variants of the Armoured Vehicle Royal Engineers, including the Titan bridge-layer, Trojan combat-engineer vehicle, Terrier Armoured Digger and Python Minefield Breaching System. Day-to-day utility work uses a series of support vehicles, including six-, nine- and fifteen-tonne trucks (often called "Bedfords", after a historic utility vehicle), heavy-equipment transporters (HET), close-support tankers, quad bikes and ambulances. Tactical communication uses the Bowman radio system, and operational or strategic communication is controlled by the Royal Corps of Signals.