In the commercial vehicle transportation sector, the terms "cargo vehicle" and "towing vehicle" are often used interchangeably in everyday language. However, from the perspective of construction vehicles or transportation engineering, their concepts, load characteristics, and driving risk control requirements are distinct:
Cargo vehicle: refers to a freight vehicle with the inherent cargo-carrying capacity (whole vehicle type), not including those that are coupled or towed by other vehicles or trailers (such as ordinary trucks or construction trucks).
Towing vehicle or towing combination: refers to tractor-trailers, semi-trailers, tractor-trailer trains, locomotive-drawn trains, etc., with a specific division of labor between cargo carrying and towing: the towing head is responsible for driving and steering, while the trailer bears the cargo load.
China's "Safety Technical Conditions for Operating Trucks" separately regulates "cargo vehicles" (excluding towing combinations) and "towing vehicles (including semi-trailer tractors and trailers)." These two types differ significantly in terms of power distribution, braking configuration, linkage structure, steering response, and crosswind stability, resulting in significantly different driving precautions on different roads and operating conditions. This article will review the common risk factors and fundamental principles for both cargo vehicles and tractor trucks, and then provide operational and safety recommendations for both cargo vehicles and tractor trucks under typical road and operating conditions.
1.1 Cargo Vehicles
Based on gross mass, they are categorized as micro (≤1.8 tons), light (1.8-6 tons), medium (6-14 tons), and heavy (>14 tons). Vehicles ≥6 meters in length and ≥4,500 kg in gross mass require a yellow license plate, while vehicles less than 6 meters in length and less than 4,500 kg in gross mass may enter the city with a blue license plate.
The cargo box structure must be tailored to the characteristics of the cargo: sealed vans are rainproof and dustproof and suitable for precision instruments; flatbed and high-sided trucks facilitate bulk loading and unloading; and flatbed trucks are suitable for heavy equipment.
1.2 Tow Vehicles
Trailers are connected to trailers via a saddle or hook and are categorized as semi-trailers (where the front of the vehicle bears part of the trailer's weight) and full-trailers (which only provide traction). Semi-trailer tractors are suitable for long-distance logistics, while full-trailer tractors are more commonly used for heavy, short-distance transport, such as in mining and construction.
Before discussing specific scenarios, it is important to clarify the safety principles and risk factors that apply to both trucks and tractor combinations. This will serve as the basis for the operational recommendations that follow:
2.1 Blind Spots and Vision Management
Large vehicles have larger blind spots than ordinary cars, often with blind spots to the sides, rear, and near sides. Drivers should regularly check their rearview mirrors (recommended every 8–10 seconds) and scan the road ahead (for example, approximately 15 seconds for trucks).
2.2 Braking Distance and Lane Change Buffer
Heavy vehicles have significant inertia, so braking requires a long distance, especially on slippery or downhill roads. This distance can be significantly increased. Anticipate the situation and maintain adequate distance between vehicles.
2.3 Load Control and Cargo Securing
Improperly secured cargo and a shifted center of gravity can lead to rollover when turning, head-on collisions during braking, and stability risks associated with cargo movement on bumpy roads. Appropriate strapping, locks, barriers, or airbag cushions should be used.
2.4 Extreme Weather, Low Visibility, and Road Adhesion Variations
Rain, fog, haze, ice, snow, road water, sand, and dust can affect tire adhesion and visibility. Reduce speed and avoid aggressive maneuvers. US regulations require commercial vehicles to "exercise extreme caution" in hazardous conditions.
2.5 Preliminary Inspection and Routine Maintenance
This includes tire pressure and wear, brake system, fluid condition, lights and signals, steering system, and joints (tractor pins, locking pins, connecting rods, sliphocks, etc.). It is recommended to perform inspections before and after each trip and keep records.
2.6 Compliance with Regulations and Qualifications
Towing combinations often involve more stringent regulations: restrictions on the number of towed trailers, maximum load capacity, signal and brake compliance requirements, and driver towing qualifications. Chinese regulations stipulate that trucks, semi-trailer tractors, and tractors are only allowed to tow one trailer; the trailer's signaling, braking, coupling, and safety devices must comply with national standards.
The following provides specific precautions for trucks (without trailers) on various typical roads and operating conditions.
3.1 Expressways and Intercity Trunk Roads
Maintaining a Stable Speed and Distance
On expressways, trucks should also avoid drastic speed fluctuations. They should maintain a steady speed and avoid sudden acceleration and braking. Due to inertia, maintain a safe distance from the vehicle ahead.
Curve Control and Overtaking Prediction
Slow down before entering a curve. Especially for heavily loaded vehicles, avoid shifting gears or accelerating mid-curve. Never drive alongside other vehicles on a curve to avoid being forced to make a sudden lane change.
When overtaking, ensure sufficient distance ahead and return quickly after overtaking. Avoid occupying the oncoming lane for extended periods.
Crosswind Stability
Strong crosswinds at high speeds can significantly impact lightly loaded or unladen trucks. Reduce speed appropriately and avoid driving parallel to the wind. If necessary, drive close to the center of the road or in a sheltered area.
Bridges and Overpasses
Pay special attention to vehicle height, whether the load exceeds the weight limit, bridge span, and the smoothness of the road surface at the bridge junction. Trucks that are too tall may collide with the top of the truck; also allow for sufficient clearance when loading cargo.
3.2 National, Provincial, Class I, and Class II Highways
Differences in Road Surface Quality
Class II and lower roads may contain potholes, damage, collapsed shoulders, accumulated water, and gravel. Trucks should avoid potholes or slow down when driving over them to prevent impact, cargo displacement, or tire damage.
Narrow Roads and Meeting Vehicles
On narrow roads in mountainous areas or rural areas, control your speed and drive close to yield points to avoid oncoming traffic. Keep the vehicle in the center of the road, leaving ample clearance.
Intersections and Turning Radius
Where road facilities are less than standard highway standards, intersection turning radii are smaller. Loaded vehicles should slow down in advance and observe oncoming vehicles, pedestrians, and non-motorized vehicles. When turning, avoid running the front of the vehicle over the side of the road or the rear of the vehicle into obstacles.
Slopes and Climbing Sections
When going uphill, select the appropriate gear to maintain power output and prevent shift failures. When going downhill, use engine braking or low gear for auxiliary braking to avoid prolonged braking, which may cause the brakes to overheat and fail.
3.3 Urban Roads, Industrial Areas, and Construction Zones
Low-Speed Driving and Frequent Stopping and Starting
City roads and industrial parks often require frequent starting and stopping. Avoid abrupt starts to prevent rearward impact of the cargo and tire slippage. Before starting, release the clutch and slowly release the accelerator. When stopping, downshift and decelerate before applying the brakes.
Construction Areas and Temporary Roads
Construction areas often have uneven surfaces, loose soil, gravel, potholes, accumulated water, and sand and gravel. Vehicles should slow down and control their driving posture when passing through poor road conditions to avoid excessive turbulence. On soft surfaces (such as mud or wet sand), avoid sudden turns, acceleration, or deceleration to prevent wheel slippage and vehicle sinking.
Special Facilities and Height and Weight Restrictions
Some factory areas or entrances to bridge tunnels, tunnels, and overpasses may have height or weight restrictions. Trucks should understand their routes in advance and avoid restricted passages or plan their routes accordingly.
3.4 Weather and Extreme Operating Conditions
Rainy and Slippery Conditions
After rain, road adhesion decreases. Trucks should slow down when passing through flooded areas and avoid sudden braking or lane changes. Slow down before entering curves. If encountering deep water, proceed with caution depending on the depth.
Fog, Haze, and Low Visibility
In low visibility, turn on fog lights and hazard warning lights, maintain a low speed, and avoid forced overtaking or lane changes.
Icy, Snowy, and Frozen Roads
Icy and snowy roads are extremely slippery. Trucks should significantly reduce speed, avoid sudden braking and steering, and, if necessary, pause until road conditions improve.
High Temperatures, Melting Road Surfaces, and Plasticization
On hot roads (especially asphalt sections), when temperatures are extremely high, the road surface may undergo slight plastic deformation, causing heavy vehicle tires to sink or slip. Avoid sudden steering and braking in high temperatures.
Towing combinations (such as semi-trailer combinations, tractor-trailer trains, and locomotive-drawn trains) are more complex than single-body trucks and present more operational risks. These are detailed below.
4.1 Inspection and Stability of Towing Connection Structures
Hook, Pin, Lock, Safety Pin
Before departure, thoroughly inspect the connecting components between the towing head and trailer (hook, pin, lock, safety pin, chain, or drawbar) for tightness, looseness, wear, or cracks. Any damage must be repaired or replaced immediately. During connection, ensure the pin is securely installed, the lock is in place, the safety pin is inserted, and electrical wiring, brake lines, and lighting cables are properly connected.
Constant Velocity Axles, Kingpin Bushings, and Flexible Connectors
For trailers with steering or flexible connections, ensure they withstand steering forces, torque constraints, and wear during cornering to prevent steering jams or binding.
Brake Synchronization, Pipeline Interfaces, and Electrical Wiring
The trailer's air brake (or hydraulic brake) system must be compatible with the towing vehicle, with tight, leak-free interfaces. Electrical connections must ensure reliable operation of the lights, brake lights, turn signals, and alarm system. The trailer's brake controller parameters must be adjusted appropriately for the load weight.
Turning Radius and Risk of "Upside-Down"
When turning, turning, or reversing, the trailer's rear trajectory should be estimated to avoid crossing the line, hitting the curb, or entering a restricted area.
4.2 Combinations on Highways and Main Roads
Acceleration and Lane Change Margin
Combinations are heavy and accelerate slowly, requiring a longer distance for merging or changing lanes to avoid sudden lane changes. Lane traffic should be monitored in advance and overtaking windows established.
Lateral Stability and Wind Load Influence
Semi-trailer or trailer combinations are more susceptible to crosswinds, turbulence, and oncoming vehicles at high speeds. Appropriate speed reduction should be employed to minimize overtaking time and avoid crossing or paralleling larger vehicles.
Rear-end collisions and braking of the preceding vehicle
The trailer and tractor may have a buffer or spring connection. In the event of an emergency brake, the trailer could exert an impact load on the tractor. The driver should maintain smooth braking force and avoid harsh braking.
Bridges, elevated roads, and passageways with weight and height restrictions
Combination vehicles are more likely to encounter height or weight restrictions on passageways. Plan your route in advance to avoid tunnels or bridges with height restrictions. Some bridges have weight restrictions to prevent structural damage; combination vehicles exceeding the weight limit will be restricted.
4.3 Combination vehicles on national highways, provincial highways, and lower-grade roads
Potholes, shoulders, and uneven surfaces
Combination vehicles have a larger span and reach, making them more sensitive to uneven road conditions. Slow down and drive slowly when navigating uneven sections to avoid structural stress from the trailer's "jumping."
Meeting and overtaking on narrow roads
Combination vehicles are wide and have a large turning radius, leaving minimal room for passing and overtaking. Pull over to the side of the road when approaching oncoming traffic; be extremely cautious when overtaking to avoid conflicts with vehicles in the opposite lane.
Slope Climbing and Braking Downhill
When driving uphill, a combination vehicle may experience uneven power distribution, causing the trailer to spin or stall. When driving downhill, it is especially important to use low gear and alternate between engine braking and braking to prevent prolonged braking that could cause the brakes to overheat and fail.
Reversing, Turning, and U-Turn Maneuvers
Reversing or turning a combination vehicle in a narrow space requires significant driving skill. Operate slowly and in steps. It is recommended that an assistant provide guidance or use a reversing camera system.
4.4 Combination Vehicles in Urban Roads, Factories, and Construction Zones
Low-Speed Maneuvering and Steering Control
When operating at low speeds in urban areas or on construction sites, combination vehicles must be operated very gently when starting, turning, and stopping to prevent the trailer from tilting or swaying. This is especially important when controlling vehicle body sway around turns and intersections.
Access Restrictions in Construction Areas
Construction sites or construction areas may have temporary supports, steel beams, trusses, temporary bridge decks, and other structures. Combined vehicles must maintain height and width clearances. Roadbed settlement and uneven slabs can also cause the trailer's bottom to hit the ground or skid.
Short-Distance Multi-Point Unloading and Transfer
Construction sites often have unloading, storage, and transfer areas. Combined vehicles should approach the site with caution to avoid crossing the road shoulder or dipping into the ground. Prioritize smooth surfaces and plan a well-planned unloading route.
4.5 Operation of Combined Vehicles in High-Risk Weather and Working Conditions
Rain, Fog, and Slippery Conditions
When operating a combined vehicle in rain or fog, the trailer and tractor's grip may be out of sync, making it prone to inconsistent braking, loss of control, and trailer drift. Reduce speed, maintain a safe distance between vehicles, and avoid abrupt maneuvers.
Ice and Snow, and Icy Roads
On icy and snowy roads, combined vehicles are particularly susceptible to skidding, trailer skidding, and loss of control and rollover. Strictly control speed, use snow chains, and avoid driving in controlled areas if possible.
Strong Winds, Gusts, and Crosswinds
Combination vehicles have large longitudinal and lateral areas and a strong windward surface. In strong winds, they are easily swept by the wind, causing them to shift or overturn. Slow down, close the vehicle width, or temporarily avoid them on windy roads.
Muddy and Soft Roads
Combination vehicles are heavily loaded and prone to getting stuck, tire slippage, and trailer dragging on muddy or soft roads. Avoid such roads if possible or use four-wheel drive or traction assistance.
To help readers quickly grasp the key points, here is a brief comparative summary and risk prioritization reminder:
|
Risk Type/Scenario |
Challenges for cargo vehicles |
Challenges for traction combinations |
Risk priority (high/medium/low) |
|
Blind spots/limited vision |
middle |
High (the visibility behind the trailer is worse) |
high |
|
Braking distance/brake failure |
high |
High (trailer brake coupling risk) |
high |
|
Connecting structure (pin, hook, locking pin) |
none |
high |
high |
|
Crosswind/wind load effects |
middle |
high |
high |
|
Cornering/turning stability |
middle |
High (trailer deviation, hook angle) |
high |
|
Hill climbing/descending braking |
middle |
high |
Medium-High |
|
Road bumps/potholes |
middle |
High (large span, structural stress) |
middle |
|
Extreme weather (snow/rain/fog) |
high |
Very high |
high |
|
Complex construction/site environment |
middle |
Higher |
middle |
|
Regulations/Qualifications/Compliance |
middle |
high |
Medium-High |
As can be seen from the table above, the challenges faced by traction combinations in terms of connection safety, structural coupling, crosswind stability, trailer control, and brake synchronization are significantly more severe than those faced by single-cargo trucks. Therefore, when designing operating procedures or training, these "combination-specific" risk points should be given greater emphasis.
To truly reduce risks, relying solely on driver experience is insufficient. A systematic approach must be implemented through systems, training, and technical support:
6.1 Operating Procedures and Inspection Systems
Develop a pre-departure checklist (including towing connectors, electrical and brake wiring, trailer status, lights, tires, load distribution, etc.).
Establish a routine maintenance system to regularly inspect and replace key parts (pins, locks, elastic connectors, brakes, bearings, etc.).
Route Planning System: Designate prohibited routes and alternative routes for height and weight restrictions, bridges, and tunnels.
6.2 Driving Training and Simulation Training
Provide specialized training for combination vehicle drivers on towing operations, reversing techniques, and emergency handling in extreme operating conditions.
Use simulators, on-site practical training, and mentoring to strengthen their ability to handle special operating conditions (such as ice and snow, crosswinds, sudden braking, and loss of control during cornering).
6.3 Technical Support and Intelligent Assistance
Equipped with onboard stability control systems (such as roll warning, trailer deviation warning, and brake coupling correction).
Use GPS and route planning systems to pre-mark routes with height and weight restrictions, as well as construction zones, to prevent combination vehicles from entering unsuitable sections of road.
Leverage onboard monitoring, driving recorders, and remote warning systems to monitor vehicle status (temperature, bearings, tire pressure, etc.) in real time.
6.4 Performance and Safety Assessment
Establish a safety performance assessment mechanism that incorporates safe driving, number of violations, and accident rates into driver and fleet performance evaluations.
Establish an accident and emergency review system to promptly analyze lessons learned and revise operating procedures and training content.
6.5 Emergency Plans and Support Mechanisms
Develop emergency plans for scenarios such as extreme weather, sudden road damage, vehicle breakdowns, and trailer detachment.
Establish rapid rescue routes, maintenance networks, and spare parts inventories to ensure rapid response in emergencies.
Daily Inspection Items: Brake line airtightness, saddle pin wear, tire cracks, and air pressure.
Emergency Tools: Triangular reflectors (placed 150 meters behind the vehicle in case of a malfunction), spare trailer cables (for sudden lighting system failure).
Technology Evolution Tips: New-generation tractors now integrate EBS and ESC systems, significantly reducing rollover rates in corners; lightweight truck designs increase legal load capacity.
By matching vehicle characteristics with operating requirements and incorporating intelligent safety features, transport efficiency and driving safety can be maximized.
The operational safety of trucks and tractor combinations under various road conditions and operating conditions is a key concern in transportation and highway engineering management. Factors ranging from wind loads, brake coupling, trailer connection structure, uneven roads, extreme weather conditions, intersections, and construction zones can all contribute to serious accidents. Later, when writing the actual column, you can incorporate local road characteristics, typical accident cases, vehicle specifications, and other information, and insert charts or photos to enhance the persuasiveness.
If you have any questions about the operation of trucks and tractors on different roads and working conditions, or if you are interested in purchasing trucks, tractors, and their accessories, please contact us.
