Heavier vehicles, such as semi-trucks and trailers, when in an accident are likely to cause more physical property damage and bodily injury, due to their size and weight. Also, these trucks are on the road all the time, maybe not 24/7 but more hours on the road than a service rated pick-up truck going to one or two job sites a day. This higher amount of use and risk of severe damage and injury leads to higher insurance costs.