A semi-trailer is a type of trailer with its axles positioned behind the vehicle's center of gravity (when uniformly loaded) and equipped with a coupling device capable of transmitting both horizontal and vertical forces to the towing vehicle. Typically featuring three axles, semi-trailers come in various configurations-such as 11-meter and 13-meter stake-side models and low-bed trailers-and serve as heavy-duty transport vehicles connected to a tractor unit via a kingpin.
Compared to rigid trucks, semi-trailers offer superior overall economic benefits for road transport. They can increase transport efficiency by 30–50%, reduce costs by 30–40%, and lower fuel consumption by 20–30%. Furthermore, the use of semi-trailers helps advance the organizational structure of the country's logistics sector.
