Trailer

A trailer refers to a non-motorised transport vehicle towed by a motor vehicle, which must be paired with a prime mover or another motorised unit to form a complete transport combination, serving as an essential vehicle category in road freight. The deployment of trailers significantly boosts road haulage economics, with articulated vehicle combinations recognised as the most straightforward and effective solution for maximising transport productivity.

Basic Characteristics

Trailers have no built-in propulsion, carry payload independently, and rely entirely on a lead vehicle for tractive effort. A motor vehicle (such as a lorry, prime mover, or forklift) can be coupled with one or more trailers; the powered unit is known as the "towing vehicle", while the unpowered trailing unit is the "trailer".

Based on their coupling configuration with the towing unit, trailers are primarily divided into two key categories: full trailers and semi-trailers. A full trailer is towed by a lead vehicle and supports its entire gross weight on its own axles; a semi-trailer is coupled to a prime mover, which carries a substantial portion of the trailer's total load.

Main Classifications

A full trailer carries its entire payload on its own chassis and connects to the lead vehicle solely via a drawbar and towing hitch, meaning the towing vehicle bears none of the trailer's vertical load and only delivers tractive force. A full trailer is fully self-supporting when decoupled. Key advantages include hassle-free drop-and-hook capabilities and low manufacturing costs; however, its high-speed braking stability is compromised, making it susceptible to fishtailing. Under China's "Measures for the Administration of Expressway Traffic" implemented in 1995, full trailers are prohibited from entering expressways; consequently, full trailers are now predominantly used for short-haul yard operations within ports, factories, and freight terminals.

A semi-trailer features axles positioned behind the vehicle's centre of gravity and couples to the prime mover's fifth wheel via a kingpin, with the prime mover bearing a proportion of the trailer's total weight. A semi-trailer cannot stand independently and relies on retractable landing gear for support when unhitched. Owing to its operational versatility and high payload capacity, the semi-trailer is ideally suited for long-distance trunk routes and high-grade highways, establishing itself as the primary backbone of commercial road transport. Compared to conventional rigid lorries, semi-trailer transport can boost operational efficiency by 30% to 50%, reduce operating costs by 30% to 40%, and cut fuel consumption by 20% to 30%.

A centre-axle trailer carries most of its weight on its centrally mounted axle group, transferring only a minimal vertical load to the towing vehicle, which manages traction and steering. Free of a steering turntable and featuring a rigid drawbar, it is far easier to reverse than a conventional drawbar full trailer and is widely utilised in car carriers and caravans.

Semi-trailers come in a diverse range of body configurations, including dropside semi-trailers, stake/caged semi-trailers, box/van semi-trailers, container skeletal semi-trailers, tanker semi-trailers, tipper semi-trailers, low-loader semi-trailers, and specialised heavy-haulage semi-trailers.

Applications and Value

Articulated semi-trailer combinations serve as the core workhorse for long-haul trunk logistics; their chassis couples securely to the prime mover via a kingpin, while the landing gear supports the semi-trailer during coupling and uncoupling procedures. The drop-and-hook transport model—where a prime mover drops its trailer at the destination and immediately hooks up a preloaded trailer to continue operations—minimises turnaround downtime and ensures continuous fleet utilisation. These efficiency and cost advantages cement the trailer's indispensable position in modern logistics while driving the continuous optimisation of China's freight transport organisation.