A fatigue related heavy vehicle is: a vehicle with a gross vehicle mass (GVM) of over 12t a combination when the total of the GVM is over 12t buses over 4.5t fitted to carry more than 12 adults (including the driver) a truck, or a combination including a truck, with a GVM of over 12t with a machine or implement attached. Some heavy vehicles are not classed as fatigue-regulated heavy vehicles. These include trams, motor vehicles modified to primarily operate as a machine or implement (plant such as agricultural machinery, bulldozers, tractors, etc.) and motor homes specifically modified for residential purposes (not just built with a sleeper berth).