A semi-trailer is a trailer whose axles are placed behind the center of gravity of the vehicle (when the vehicle is evenly loaded) and equipped with a coupling device that can transmit horizontal and vertical forces to the tractor. Semi-trailers are generally three-axle semi-trailers, and their types are divided into 11-meter warehouse semi-trailers, 13-meter warehouse semi-trailers, low-bed semi-trailers, etc. It is a heavy-duty transportation vehicle connected to the front of the semi-trailer through a traction pin.
