A truck is a vehicle usually used for transporting bulk goods, materials, or equipment. When the gasoline engine-driven trucks came into fashion, these were called "motor trucks" and the Heavy Goods Vehicle (HGV)). Heavy trucks are the largest trucks allowed on the road. They are mostly used for long-haul purposes, often in semi-trailer or B-double configuration. Road damage and wear increase very rapidly with the axle weight. In many countries with good roads a 6-axle truck may have a maximum weight over 50 tonnes (50,000 kg).