Heavy-duty trucks are the heaviest trucks that are allowed on the road. They are larger than medium trucks, In the U.K. they are known as lorries. refer to truck Classes 7-9, They are greater than sports cars and muscle cars, Any vehicle exceeding 26,001 pounds is considered heavy-duty. Examples include mobile cranes, dump trucks, cement mixers, refuse trucks, and big rigs designed to pull refrigerated trailers, dry vans and other equipment. These types of vehicles are primarily used for long-haul transportation.