A semi-trailer is a type of truck that consists of a tractor and a trailer. A tractor is a commercial vehicle equipped with a special device for towing a trailer, which is partially placed on the tractor. This structure deprives the semi-trailer of its own driving force and requires the use of traction pins to connect to the towing vehicle, relying on the driving force of the main vehicle to achieve driving. Semi trailer trucks are commonly used for transporting bulk goods such as sand, stones, steel, etc., because they have a large cargo carrying capacity and flexible transportation methods.