Trailers are primarily divided into two categories: semi-trailers and full trailers. The most noticeable difference lies in the presence of front wheels. Semi-trailers lack front wheels, with the tractor (truck head) bearing part of the weight, while full trailers have wheels at both ends and can support themselves independently.

In Japan, semi-trailers are the most widely used type. These trailers rely on tractors for power and connect to them via a fifth wheel coupling to form a complete unit. Full trailers are more commonly found in specific areas such as ports and docks where flexible maneuvering is required.

Semi-trailers are currently the most prevalent type in the logistics industry. Their defining characteristic is that they lack independent power and must rely on tractors to move. The axles of semi-trailers are typically located at the rear, with the front connected to the tractor via a fifth wheel. When disconnected from the tractor, semi-trailers cannot stand independently and require support devices (landing gear) to maintain balance.

Single-axle semi-trailers have only one drive axle. Their primary advantages include smooth acceleration and stable driving performance, making them particularly suitable for long-distance transportation. With relatively shorter bodies, single-axle semi-trailers offer better maneuverability and can adapt to complex road conditions. Additionally, they exert less pressure on the tractor's fifth wheel, making them ideal for cargo that doesn't require heavy front-end loading.

Tandem-axle semi-trailers feature two drive axles, providing greater load capacity compared to their single-axle counterparts. While slightly less maneuverable, they offer superior stability on challenging road surfaces such as ice, snow, or gravel. For cargo requiring significant front-end loading, tandem-axle semi-trailers are the more reliable choice.

Unlike semi-trailers, full trailers have axles at both ends and can independently support cargo. This means full trailers can be pulled by tractors or function as independent trucks. Furthermore, full trailers allow for additional cargo loading on the tractor itself, increasing overall transport capacity.

Regarding length restrictions, the combined length of semi-trailers with tractors must not exceed 18 meters, while full trailers have a maximum length limit of 21 meters. This gives full trailers an advantage when transporting oversized cargo.

Beyond the two basic types of semi-trailers and full trailers, various specialized trailers have been developed to accommodate different cargo types and transportation requirements. These specialized trailers feature custom designs in structure and functionality to ensure cargo safety and transport efficiency.

Open platform trailers refer to those without enclosed structures on their cargo beds. These trailers offer excellent versatility for transporting goods of various shapes and sizes. Common types include:

• Container Trailers: Bridges between land and sea transport, primarily used for shipping containers. They require specialized lifting equipment and twist locks to secure containers.
• Flatbed Trailers: The most common type, featuring flat platforms ideal for transporting lumber, steel, and similar goods. Often equipped with stanchions to prevent cargo shifting.
• Heavy Equipment Trailers: Designed with low platforms for easy loading of construction machinery like excavators. Available in 8-wheel and 16-wheel configurations based on load capacity.

Enclosed trailers feature covered cargo areas for goods requiring environmental protection, such as powders and liquids. Main types include:

• Bulk Cargo Trailers: Designed for transporting powdered materials like cement and flour, available in pneumatic discharge and self-dumping configurations.
• Tank Trailers: Specialized for liquid transport including gasoline and edible oils, featuring separate tank and chassis components.

For specific transportation requirements, specialized trailer designs include:

• Pole Trailers: Designed for extra-long items like rails and bridge components, using the cargo itself as part of the vehicle structure.
• Car Carriers: Featuring multi-level platforms for efficient vehicle transport, typically accommodating 5-6 cars within legal length limits.

Trailers are indispensable components of modern logistics. Choosing the appropriate type requires careful consideration of cargo characteristics, weight, dimensions, transportation distance, and road conditions. Since both tractors and trailers represent significant investments with long lead times, thorough research and planning are essential to ensure the selected equipment meets current and future transportation needs.