For commercial vehicles, the body system is far more than a simple "shell". It serves as the exclusive working space for drivers, and also a key component that safeguards driving safety and improves operational efficiency. The design and structure of the body directly affect vehicle performance and driving comfort. Commercial vehicles for different purposes feature distinct body structures and configurations, and the sector is now constantly upgrading towards lighter, smarter and more comfortable development. Combining core knowledge of commercial vehicles, we will explore the key aspects of the body system in this article.
![福田卡车图]( "福田卡车图")
I. Overview of the Body System
(1) Definition
The definition of a commercial vehicle body varies by vehicle type: the body of a commercial freight vehicle specifically refers to the passenger-carrying part, i.e., the cab; the body of a bus covers both passenger and cargo areas, and can refer to the entire vehicle. In terms of composition, a vehicle body usually includes components such as windows, doors, cab, passenger compartment, engine compartment and luggage compartment. Its shape and structure are not only the physical language of the vehicle, but also directly affect the vehicle's aerodynamic performance, safety performance and driving experience.
(2) Functions
The role of the body system is mainly reflected in four aspects: providing a comfortable working environment for drivers, reducing air resistance during driving, protecting the safety of drivers and passengers, and serving as a mounting carrier for electrical and other devices. On this basis, the body system also needs to perform additional functions, including protecting the safety of occupants, achieving anti-theft through the door lock system, providing resting space for occupants, having storage capacity, regulating indoor temperature, installing electrical instruments, providing audio entertainment, fixing seats, ensuring rearview visibility, meeting basic living needs, supporting mobile phone charging, and adapting to driving in complex weather such as rainy and foggy days.
![驾驶室总成图]( "驾驶室总成图")
II. Body Structural Forms
Commercial vehicle body structures are mainly divided into two types: body-on-frame and unibody. Semi-monocoque bodies, which are essentially frameless load-bearing structures, are usually not classified as an independent category. The two structural types differ significantly in design, performance and applicable scenarios.
(1) Body-on-Frame
A body-on-frame structure is equipped with an independent rigid frame (also known as a chassis frame). The body itself is suspended on the frame through elastic components, and core components such as the engine and suspension are all mounted on the frame. It has prominent advantages: the frame can filter most vibrations through elastic components to improve driving smoothness; in the event of a collision, the frame can absorb most of the impact force, reduce body deformation, protect the safety of drivers and passengers, and reduce in-vehicle noise at the same time; it effectively protects the body when driving on rough roads. However, this structure also has obvious shortcomings: the overall body is heavy with a large self-weight, the vehicle has a high center of gravity, and the stability is poor at high speeds. At present, almost all commercial freight vehicles adopt the body-on-frame structure.
![非承载式]( "非承载式")
(2) Unibody
A unibody structure has no independent rigid frame. By reinforcing the front end, side panels, rear end, floor and other parts, the body and underframe form an integrated rigid space structure that directly bears various driving loads. Its core advantages include: strong bending and torsional rigidity, light self-weight, low body height, low center of gravity, good high-speed driving stability, and a relatively simple assembly process. The disadvantage is that road loads are directly transmitted to the body through the suspension, resulting in high in-vehicle noise and vibration. This type of structure is mainly applied to buses and passenger cars, especially high-end buses. For example, the Mercedes-Benz 0404 coach adopts a vertical and horizontal grid truss structure made of thin steel plate stamping or section steel welding for its underframe, and the space under the seats can be used as a luggage compartment, making full use of space while ensuring structural strength.
![承载式 拷贝]( "承载式 拷贝")
III. Composition of the Body
The entire commercial vehicle body consists of a body-in-white (BIW) and its accessories. The BIW is a welded assembly of body structural parts and cover parts (including doors), while body accessories cover interior and exterior trim parts and various auxiliary equipment. There are significant differences in the bodies of commercial vehicles with different tonnages.
(1) Body-in-White (BIW)
The BIW is the mounting foundation for all body components. Generally, it refers to a rigid space structure composed of main load-bearing elements such as longitudinal beams, cross beams and pillars, as well as the plates connected to them. Its surface is usually laid with sound insulation, heat insulation, anti-vibration, anti-corrosion and sealing materials and coatings.
The BIW of a cab-over commercial freight vehicle is composed of floor, roof panel, front wall panel, rear wall panel, side wall panels, doors and other components, forming a rigid space structure that provides a mounting benchmark for interior and exterior trim parts and accessories. The BIW structure of buses varies by length: the body structure of buses under 6 meters is similar to that of passenger cars, adopting an unibody design, mainly made of welded thin plate stampings, with few frame structures; the body of medium and large buses over 7 meters is composed of a frame and skin. The frame is divided into six major parts: front wall, rear wall, left side, right side, roof and floor. The connection parts of each part are called parting surfaces. The frame bears the overall load, giving full play to material performance.
![白车身]( "白车身")
(2) Body Interior Trim
Body interior trim is a general term for parts that play a decorative and protective role inside the vehicle. Its core development direction is to align with passenger car interior trim with continuously improved refinement, and its design concept and configuration specifications vary by vehicle positioning.
The interior trim of medium and heavy-duty commercial vehicles focuses on habitability, comfort and aesthetics. High-end models are designed in accordance with passenger car concepts, equipped with peach wood grain luxury interior trim, electric window regulators, electric door locks, 10-disc VCD, on-board phone, on-board refrigerator and other configurations to create a "mobile home". The interior trim of light and micro trucks focuses on driver needs, also following the passenger car design concept, providing electric window regulators, electric door locks, reverse image, simulated leather seats and other configurations to improve the driving experience through refined matching.
Differences in interior trim modules are mainly determined by cost factors, and the choice of materials, fabrics and comfort configurations directly affects the texture of the interior trim. Taking the Auman brand as an example, it practices the people-oriented concept, equipped with a soft instrument panel, air suspension shock-absorbing seats, integrated three-point safety belts, a wide and thick sleeper, multi-dimensional storage space, a soft wrapped instrument panel and carpet, combined with convenient cup holders and ashtrays, highlighting the temperament of a high-end brand.
![驾驶室内饰]( "驾驶室内饰")
(3) Body Exterior Trim
Body exterior trim is a general term for parts that play a decorative and protective role outside the vehicle. It not only shapes the vehicle's appearance, but also safeguards driving safety, and is composed of multiple functional modules.
![欧曼外饰 拷贝]( "欧曼外饰 拷贝")
Exterior trim components include external sun visors, front wall accessories, side walls and their accessories, radiator grilles, front bumpers, rearview mirrors, left and right front corner panels, air deflectors, foot pedals, front baffles, mudguards, fenders and so on. Exterior trim design pursues both aerodynamic optimization and protection and visibility guarantee. Components such as air deflectors and side skirts can reduce wind resistance and improve fuel economy; front bumpers are made of high-strength materials, which can protect the body and core components in minor collisions, and engineering vehicles can be equipped with anti-collision guardrails to strengthen protection; large-area rearview mirrors and downward view mirrors can reduce visual blind spots, and LED daytime running lights and fog lights improve driving safety in rainy and foggy weather.
Exterior trim configurations vary by vehicle type. For example, Auman heavy-duty trucks are equipped with high-roof air deflectors, side air deflectors, large-area rearview mirrors (including driver side, passenger side and downward view mirrors), integrated front bumpers, front wheel front and rear mudguards, etc., optimizing aerodynamic performance while expanding the field of vision.
![车身外饰各模块示意图]( "车身外饰各模块示意图")
(4) Body Accessories
Body accessories are auxiliary components that ensure the normal operation of body functions, covering a wide range, including door locks, door hinges, window regulators, seals, windshield wipers, windshield washers, sun visors, rearview mirrors, handrails, cigarette lighters, audio equipment and so on. Some high-end models are also equipped with living equipment such as on-board phones, microwave ovens and small refrigerators. The development trend of core accessories shows obvious upgrading characteristics.
1. Seat System
The seat system has undergone iteration from "mechanical seats → hydraulic seats → airbag seats + multi-directional adjustability", achieving a qualitative leap in function and quality. Fabrics are divided into two types: woven fabric and simulated leather, adapted to high and low-end needs respectively. Both seat cushions and backrests are designed in accordance with ergonomics. Driver seats generally adopt "M" slide rails for front and rear adjustment, and spindle-type recliners for nearly stepless adjustment of the backrest angle. Some seats can be folded and flipped up to facilitate the maintenance of engine compartment components. For example, the seats of Auman heavy-duty trucks adopt air suspension technology, which can automatically adjust the damping strength and adjust the position and angle in multiple dimensions, adapting to the needs of long-distance driving.
![座椅 拷贝]( "座椅 拷贝")
2. Door and Accessories
The door system is upgrading from traditional mechanical control to electric control. Core components include window weatherstrips, exterior door trim panels, inner door trim panels, window glass, manual/electric window regulators, door check straps, central door locks and so on. Weatherstrips can effectively isolate noise, dust and rainwater, improving the airtightness of the carriage; electric window regulators and central door locks optimize operational convenience, adapting to the intelligent needs of modern commercial vehicles. The inner door trim panel mounting bracket, as a core fixing component, ensures the assembly stability and durability of the inner door trim panel.
![车门及其附件]( "车门及其附件")
3. Air Conditioning and Door Lock Systems
The development trend of heating and air conditioning systems is automatic control + independent heating and independent air conditioning. Core components include air conditioning air outlets, switches, pipelines and so on, which can accurately adjust the in-vehicle temperature to adapt to driving needs under different climatic conditions. Door lock systems are developing towards the intelligent direction of remote electronic remote control and mobile phone APP. Driven by new energy commercial vehicles, intelligent application scenarios are continuously expanding. Core components cover door handles, door locks, door lock pull rods and so on, taking into account both anti-theft and operational convenience.
In summary, the commercial vehicle body system is an organic combination of structure, function and design. Various components work together to support the operational needs of commercial vehicles in different scenarios. With the technological upgrading of the industry, the body system is gradually achieving breakthroughs in lightweight, intelligence and comfort, injecting impetus into the high-quality development of the commercial vehicle industry.
IV. Development Trends
Modern commercial vehicle body design centers on four core elements: safety, durability, comfort and efficiency, and a mature technical system has been formed. Many previously predicted development trends and future designs have been implemented to varying degrees in mid-to-high-end models at present, and some cutting-edge technologies are gradually moving from pilot projects to popularization.
In the field of lightweight materials, aluminum alloy cargo compartments have not been fully popularized due to high costs, but carbon fiber materials have achieved breakthroughs. In 2025, China's first carbon fiber lightweight cargo compartment was successfully delivered. Compared with the same type of aluminum alloy cargo compartment, it reduces weight by more than 1.3 tons and has both high strength and corrosion resistance, but it is still in the pilot application stage due to cost constraints. In terms of safety and comfort configurations, airbag shock-absorbing seats and flat floor design have become standard equipment for high-end heavy-duty trucks. Models such as Chenglong H5 large single-bridge trucks adopt a high-roof flat floor structure, combined with wide-body sleeper berths (up to 900-1150mm in some high-end models), greatly improving driving comfort. Intelligent configurations have the fastest implementation speed. 360° visual systems and digital display instruments have been widely applied to intelligent light trucks such as JAC 1 Truck. Some models are also integrated with the Intelligent Connected System 3.0 (ICS 3.0) to realize functions such as vehicle condition monitoring and intelligent navigation. Independent air conditioning and heating systems have a high penetration rate in long-distance heavy-duty trucks, and stereo sound systems have become a regular configuration with the passenger car-oriented upgrading of interior trim.
In the future, the commercial vehicle body system will continue to deepen research and development of lightweight, intelligent and comfortable technologies, and continuously optimize product adaptability, providing more solid support for the high-quality development of the commercial vehicle industry.
![欧曼GTL 拷贝]( "欧曼GTL 拷贝")
