Cargo Trailer

A trailer is an unpowered vehicle towed by a powered vehicle. It is commonly used for the transport of goods and materials. There are two general categories of trailers: the full trailer and the semitrailer. A full trailer is a type of trailer whose entire weight is supported by its own wheels, with no weight transferred to the towing vehicle. In contrast, a semi-trailer is designed so that a portion of its weight is carried by its own wheels, while the remaining weight is borne by the towing vehicle.

Sometimes recreational vehicles, travel trailers, or mobile homes with limited living facilities where people can camp or stay have been referred to as trailers. In earlier days, many such vehicles were towable trailers.

Trailers have been used for thousands of years, predating the invention of the automobile. Before the advent of the wheel, early humans employed the concept of trailering by using drag sleds to transport goods. While the two wheel war chariot is one of the earliest and simplest forms of a semi-trailer, Alexander Winston has been credited with inventing the modern semitrailer in Cleveland, Ohio.

United States

In the United States, the term is sometimes used interchangeably with travel trailer and mobile home, varieties of trailers, and manufactured housing designed for human habitation. Their origins lay in utility trailers built in a similar fashion to horse-drawn wagons. A trailer park is an area where mobile homes are placed for habitation.

In the United States trailers ranging in size from single-axle dollies to 6-axle, , semi-trailers are commonplace. The latter, when towed as part of a tractor-trailer or "18-wheeler", carries a large percentage of the freight that travels over land in North America.

Types

Some trailers are made for personal (or small business) use with practically any powered vehicle having an appropriate hitch, but some trailers are part of large trucks called semi-trailer trucks for transportation of cargo.

Enclosed toy trailers and motorcycle trailers can be towed by commonly accessible pickup truck or van, which generally require no special permit beyond a regular driver's license. Specialized trailers like open-air motorcycle trailers, bicycle trailers are much smaller, accessible to small automobiles, as are some simple trailers, have a drawbar and ride on a single axle. Other trailers, such as utility trailers and travel trailers or campers come in single and multiple axle varieties, to allow for varying sizes of tow vehicles.

There also exist highly specialized trailers, such as genset trailers, pusher trailers and other types that are also used to power the towing vehicle. Others are custom-built to hold entire kitchens and other specialized equipment used by carnival vendors. There are also trailers for hauling boats.

Trackless train

Utility

A utility trailer is a general purpose trailer designed to by towed by a light vehicle and to carry light, compact loads of up to a few metric tonnes. It typically has short metal sides (either rigid or folding) to constrain the load, and may have cage sides, and a rear folding gate or ramps. Utility trailers do not have a roof. Utility trailers have one axle set comprising one, two or three axles.
If it does not have sides then it is usually called a flatbed or flat-deck trailer.
If it has rails rather than sides, with ramps at the rear, it is usually called an open car transporter, auto-transporter, or a plant trailer, as they are designed to transport vehicles and mobile plant.
If it has fully rigid sides and a roof with a rear door, creating a weatherproof compartment, this is usually called a furniture trailer, cargo trailer, box van trailer or box trailer.

Fixed Plant

A Fixed Plant Trailer is a special purpose trailer built to carry units which usually are immobile such as large generators & pumps

Bicycle

A bicycle trailer is a motor less wheeled frame with a hitch system for transporting cargo by bicycle.

Construction

Construction trailers are mobile structures (trailers) used to accommodate temporary offices, dining facilities and storage of building materials during construction projects. The trailers may be equipped with radios for communication.

Travel

Popular campers use lightweight trailers, aerodynamic trailers that can be towed by a small car, such as the BMW Air Camper. They are built to be lower than the tow vehicle, minimizing drag.

Others range from two-axle campers that can be pulled by most mid-sized pickups to trailers that are as long as the host country's law allows for drivers without special permits. Larger campers tend to be fully integrated recreational vehicles, which often are used to tow single-axle dolly trailers to allow the users to bring small cars on their travels.

Teardrop

Semi

A semi-trailer is a trailer without a front axle. A large proportion of its weight is supported either by a road tractor or by a detachable front axle assembly known as a dolly. A semi-trailer is normally equipped with legs, called "landing gear", which can be lowered to support it when it is uncoupled. In the United States, a single trailer cannot exceed a length of on interstate highways (unless a special permit is granted), although it is possible to link two smaller trailers together to a maximum length of .

Semi-trailers vary considerably in design, ranging from open-topped grain haulers through Tautliners to normal-looking but refrigerated x enclosures ("reefers"). Many semi-trailers are part of semi-trailer trucks. Other types of semi-trailers include dry vans, flatbeds and chassis.

Many commercial organizations choose to rent or lease semi-trailer equipment rather than own their own semi-trailers, to free up capital and to keep trailer debt from appearing on their balance sheet.

File:Tank truckタンクローリー9274341.jpg, Semi tank trailer in Japan
File:SinoTruk HOWO Iran.jpg, SinoTruk HOWO with flatbed trailer
File:LKW Kipper DSCF6469 (crop).jpg, LKW Kipper dump trailer
File:Sainsburys lorry refrigerated trailer.jpg, Sainsburys lorry refrigerated trailer
File:Truck.car.transporter.arp.750pix.jpg, A car carrier trailer
Image:Scania (4-series) with EU-trailer. 25.25 meters.jpg, A truck pulling a semi-trailer using a trailer Dolly
File:India auto-rickshaw tuk tuk adapted for logistics July 2007.jpg, Indian auto-rickshaw adapted with ''trailer''

Full

A full trailer is a term used in the United States and New Zealand for a freight trailer supported by front and rear axles and pulled by a drawbar. In Europe this is known as an ''A-frame drawbar trailer'', and in Australia it is known as a ''dog trailer''. Commercial freight trailers are produced to length and width specifications defined by the country of operation. In America this is wide and long. In New Zealand, the maximum width is while the maximum length is , giving a 22-pallet capacity.

As per AIS 053, full trailer is a towed vehicle having at least two axles, and equipped with a towing device which can move vertically in relation to the trailer and controls the direction of the front axle(s), but which transmits no significant static load to the towing vehicle. Common types of full trailers are flat deck, hardside/box, curtainside or bathtub tipper style with axle configurations up to two at the drawbar end and three at the rear of the trailer.

This style of trailer is also popular for use with farm tractors.

Close-coupled

A close-coupled trailer is fitted with a rigid towbar which projects from its front and hooks onto a hook on the tractor. It does not pivot as a drawbar does.

Motorcycle

A motorcycle trailer may be a trailer designed to haul motorcycles behind an automobile or truck. Such trailers may be open or enclosed, ranging in size from trailers capable of carrying several motorcycles or only one. They may be designed specifically to carry motorcycles, with ramps and tie-downs, or may be a utility trailer adapted permanently or occasionally to haul one or more motorcycles.

Another type of motorcycle trailer is a wheeled frame with a hitch system designed for transporting cargo by motorcycle. Motorcycle trailers are often narrow and styled to match the appearance of the motorcycle they are intended to be towed behind. There are two-wheeled versions and single-wheeled versions. Single-wheeled trailers, such as the Unigo or Pav 40/41, are designed to allow the bike to have all the normal flexibility of a motorcycle, usually using a universal joint to enable the trailer to lean and turn with the motorcycle. No motorcycle manufacturer recommends that its motorcycles be used to tow a trailer because it results in additional safety hazards for motorcyclists.

Livestock

There are a number of different styles of trailers used to haul livestock such as cattle, horses, sheep and pigs. The most common is the stock trailer, a trailer that is enclosed on the bottom, but has openings at approximately the eye level of the animals to allow ventilation. The horse trailer is a more elaborate form of stock trailer. Because horses are usually hauled for the purpose of competition or work, where they must be in peak physical condition, horse trailers are designed for the comfort and safety of the animals. They usually have adjustable vents and windows as well as suspension designed to provide a smooth ride and less stress on the animals. In addition, horse trailers have internal partitions that assist the animal in staying upright during travel and protect horses from injuring each other in transit. Larger horse trailers may incorporate additional storage areas for horse tack and may even include elaborate living quarters with sleeping areas, bathroom and cooking facilities, and other comforts.

Both stock trailers and horse trailers range in size from small units capable of holding one to three animals, able to be pulled by a pickup truck, SUV or even a quad bike; to large semi-trailers that can haul a significant number of animals.

Boat

Roll trailer

Baggage trailer

Baggage trailers are used for the transportation of loose baggage, oversized bags, mail bags, loose cargo carton boxes, etc. between the aircraft and the terminal or sorting facility. Dollies for loose baggage are fitted with a brake system which blocks the wheels from moving when the connecting rod is not attached to a tug. Most dollies for loose baggage are completely enclosed except for the sides which use plastic curtains to protect items from weather. In the US, these dollies are called baggage carts, but in Europe ''baggage cart'' means passenger baggage trolleys.

Hydraulic modular trailer

A hydraulic modular trailer (HMT) is a special platform trailer unit which feature swing axles, hydraulic suspension, independently steerable axles, two or more axle rows, compatible to join two or more units longitudinally and laterally and uses power pack unit (PPU) to steer and adjust height. These trailer units are used to transport oversized load, which are difficult to disassemble and are overweight. These trailers are manufactured using high tensile steel, which makes it  possible to bear the weight of the load with the help of one or more ballast tractors which push and pull these units via drawbar or gooseneck together making a heavy hauler unit.

Typical loads include oil rig modules, bridge sections, buildings, ship sections, and industrial machinery such as generators and turbines. There is a limited number of manufacturers who produce these heavy-duty trailers because the market share of oversized loads is very thin when we talk about transportation industry. There are self powered units of hydraulic modular trailer which are called SPMT which are used when the ballast tractors can not be applied.

Bus trailer

A bus trailer is for transporting passengers hauled by a tractor unit similar like that of a truck. These trailers have become obsolete due to the issue of the communication between the driver and the conductor and traffic jams.

File:Camel bus in Havana.jpg, Camel bus in Havana

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