Trailer (vehicle)

A trailer is an unpowered vehicle towed by a powered vehicle. It is commonly used for the transport of goods and materials.

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.

Baset trailer
Utility trailer

United States

Scania (4-series) with EU-trailer. 25.25 meters
A truck pulling a semi-trailer using a trailer dolly

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, 13-foot-6-inch (4.11 m) high, 53-foot (16 m) long 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 of trailers

Acp tzero DSC00467
ACP Backtracking genset trailer

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, pulled by a drawbar and riding on a single set of axles. 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 their ilk 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.

Travel trailer

Custom camper
A custom-made popup camper trailer

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.


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 57 ft 0 in (17.37 m) on interstate highways (unless a special permit is granted), although it is possible to link two smaller trailers together to a maximum length of 63 ft 0 in (19.20 m).

Semi-trailers vary considerably in design, ranging from open-topped grain haulers through Tautliners to normal-looking but refrigerated 13 ft 6 in (4.11 m) x 53 ft 0 in (16.15 m) 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.

Full trailer

Fruehauf truck Trailer
Full trailer with steered axle

A full trailer is a term used in the United States 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. A commercial freight trailer is 96 or 102 in (2.44 or 2.59 m) wide and 35 or 40 ft (10.67 or 12.19 m) long. 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. This style of trailer is also popular for use with farm tractors.

Close-coupled trailer

Czech Artic
A close-coupled trailer

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 trailer

Interior of an enclosed motorcycle trailer

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 creates additional safety hazards for motorcyclists.

Livestock trailer

A horse trailer

There is a number of different styles of trailers used to haul livestock such as cattle and horses. 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 or even an SUV; to large semi-trailers that can haul a significant number of animals.

Boat trailer

Hitching a trailer

Drawbar trailer coupling
Trailer-hitch on a large vehicle

A trailer hitch, fifth-wheel coupling or other type of tow hitch is needed to draw a trailer with a car, truck or other traction engine.

Ball and socket

A trailer coupler is used to secure the trailer to the towing vehicle. The trailer coupler attaches to the trailer ball. This forms a ball and socket connection to allow for relative movement between the towing vehicle and trailer while towing over uneven road surfaces. The trailer ball is mounted to the rear bumper or to a draw bar, which may be removable. The draw bar is secured to the trailer hitch by inserting it into the hitch receiver and pinning it. The three most common types of couplers are straight couplers, A-frame couplers, and adjustable couplers. Bumper-pull hitches and draw bars can exert tremendous leverage on the tow vehicle making it harder to recover from a swerving situation.

Fifth wheel and gooseneck

A gooseneck trailer attached to a pickup truck
Dually pickup truck tandem axle.jpeg
Tandem axle dually pickup truck with gooseneck trailer

These are available for loads between 10,000 and 30,000 pounds (4.5 and 13.6 t).[1][2] Both the hitches are better than a receiver hitch and allow a more efficient and central attachment of a large trailer to the tow vehicle. These hitch types are designed for pickup truck bed. They are able to haul large loads without disrupting the stability of the vehicle. Traditional hitches are connected to the vehicle back but these are attached to the truck bed, which make them better for making sharp turns and cutting tight corners.[3] Both styles have trailers attach to a coupler mounted above the axle within the bed of the tow vehicle such as a flat deck or pickup truck. A fifth-wheel coupling is also referred to as a kingpin hitch and is a smaller version of the semi-trailer "fifth wheel". Though a fifth wheel and a gooseneck trailer look much the same, their method for coupling is different. A fifth wheel uses a large horseshoe-shaped coupling device mounted a foot or more above the bed of the tow vehicle. A gooseneck couples to a standard 2 516-inch (59 mm) ball mounted on the bed of the tow vehicle. The operational difference between the two is the range of movement in the hitch. The gooseneck is very maneuverable and can tilt in all directions, while the fifth wheel is intended for level roads and limited tilt side to side. Gooseneck mounts are often used for agricultural and industrial trailers. Fifth-wheel mounts are often used for recreational trailers. Standard bumper-hitch trailers typically allow a 10% or 15% hitch load while a fifth wheel and gooseneck can handle 20% or 25% weight transfer.

Trailer jack

The basic function of a trailer jack is to lift the trailer to a height that allows the trailer to be hitched or unhitched to and from the towing vehicle. Trailer jacks are also used for leveling the trailer during storage. The most common types of trailer jacks are A-frame jacks, swivel jacks, and drop-leg jacks. Some trailers, such as horse trailers, have a built-in jack at the tongue for this purpose.

Electrical components

Many older cars took the feeds for the trailer's lights directly from the towing vehicles rear light circuits. As bulb-check systems were introduced in the 1990s "by-pass relays" were introduced. These took a small signal from the rear lights to switch a relay which in turn powered the trailer's lights with its own power feed. Many towing electrical installations, including vehicle-specific kits incorporate some form of bypass relays.

In the US, trailer lights usually have a shared light for brake and turn indicators. If such a trailer is to be connected to a car with separate lamps for turn indicator and brake a trailer light converter is needed.

Nowadays some vehicles are being fitted with CANbus networks, and some of these use the CANbus to connect the tow bar electrics to various safety systems and controls. For vehicles that use the CANbus to activate towing-related safety systems, a wiring kit that can interact appropriately must be used. Without such a towbar wiring kit the vehicle cannot detect the presence of a trailer and can therefore not activate safety features such as trailer stability program which can electronically control a snaking trailer or caravan.

By-pass systems are very cost effective but may not be appropriate on cars with interactive safety features.


MidiTrain img 0828a
Bus trailer
Bus and trailer in Saskatchewan, Canada

Larger trailers are usually fitted with brakes. These can be either electrically operated, air operated, or overrun brakes.


Trailer stability can be defined as the tendency of a trailer to dissipate side-to-side motion. The initial motion may be caused by aerodynamic forces, such as from a cross wind or a passing vehicle. One common criterion for stability is the center of mass location with respect to the wheels, which can usually be detected by tongue weight. If the center of mass of the trailer is behind its wheels, therefore having a negative tongue weight, the trailer will likely be unstable. Another parameter which is less commonly a factor is the trailer moment of inertia. Even if the center of mass is forward of the wheels, a trailer with a long load, and thus large moment of inertia, may be unstable.[4]

Some vehicles are equipped with a Trailer Stability Program that may be able to compensate for improper loading.

See also

List of types of trailers


  1. ^ "Gooseneck Trailer Hitch Information and Review |". Retrieved 2017-07-22.
  2. ^ " Is For Sale". Retrieved 2017-07-22.
  3. ^ Carlos Perry. "Gooseneck vs 5th Wheel Hitch For Towing Fifth Wheel Trailer".
  4. ^ Karnopp, Dean (2004). Vehicle Stability. CRC Press. p. 93. Retrieved 2008-11-29.

External links

Bicycle trailer

A bicycle trailer is a motorless wheeled frame with a hitch system for transporting cargo by bicycle. It can greatly increase a bike's cargo capacity, allowing point-to-point haulage of objects up to 4 cubic yards (3 cubic metres) in volume that weigh as much as half a ton.

British Rail Class 127

The British Rail Class 127 diesel multiple units were built by BR Derby in 1959. Thirty 4-car units were built, formed of two outer driving motor vehicles, sandwiching two intermediate trailers which were classified class 186. The technical description of such as 4-car unit was DMBS + TSL + TS + DMBS.

British Rail Class 314

British Rail Class 314 alternating current (AC) electric multiple units (EMU) were built by BREL York works in 1979. They were the third variety of British Rail's then-standard 1972 design for suburban EMUs, which eventually encompassed 755 vehicles and five classes (Class 313/314/315/507/508). Able to operate from 25 kV overhead line only, the fleet works inner-suburban services on the Strathclyde rail network in Scotland. The class can run to a top speed of 70 mph (113 km/h).

British Rail Class 320

The British Rail Class 320 is an alternating current (AC) electric multiple-unit (EMU) train found on the Strathclyde rail network in Central Scotland. They are mainly used on the North Clyde Line and the Argyle Line, but they can also be seen on Glasgow Central to Lanark services as well as Cathcart Circle services along with Class 318s, Class 380s, and Class 385s.

British Rail Class 424

The British Rail Class 424 "Networker Classic" was a prototype electric multiple unit (EMU) built in 1997 by Adtranz at Derby Litchurch Lane Works from a Class 421 driving trailer vehicle.

British Rail Class 769

The Class 769 Flex is a type of bi or tri-mode multiple unit (BMU/TMU) which is currently being converted by Brush Traction. The train is a conversion of the existing Class 319 electric multiple unit (EMU), a conventional vehicle type which had become surplus to requirements during the 2010s.The conversion process was carried out by a partnership between the rolling stock leasing company Porterbrook and train manufacturer Wabtec Brush. The conversion principally involves the addition of a pair of MAN diesel engines under each driving trailer vehicle, the output of which is fed into ABB-provided alternators to power the existing electric traction systems. According to Porterbrook, the Class 769’s performance under diesel power is either equal or superior to that of a Class 150 Sprinter diesel multiple unit (DMU), and that the switchover between EMU and DMU modes can be carried out while the train is in motion.

Buddha Statue of Hyderabad

The Buddha Statue of Hyderabad is a monolith located in India. It is the world's tallest monolith of Gautama Buddha, erected on Gibraltar Rock in the middle of Hussain Sagar.


Camper may refer to:

A person who engages in recreational camping

A trailer (vehicle) used for camping, see travel trailer, popup camper


Camping (gaming), a tactic in video gaming.

Driving licence in Japan

In Japan, a driving licence (運転免許, Unten menkyo) is required when operating a car, motorcycle or moped on public roads. Driving licences are issued by the prefectural governments' public safety commissions and are overseen on a nationwide basis by the National Police Agency.

Horse trailer

A horse trailer or horse van (also called a horse float in Australia and New Zealand or horsebox in the British Isles) is used to transport horses. There are many different designs, ranging in size from small units capable of holding two or three horses, able to be pulled by a pickup truck or even a SUV; to gooseneck designs that carry six to eight horses, usually pulled by 1-ton dually-style pickups. There are also large semi-trailers that can haul a significant number of animals. In the UK, a horsebox may also refer to a motorised vehicle adapted to carry horses (generally known as a horse van in North America or Australasia), or a railway vehicle specifically designed to carry horses.

The least expensive type of trailer is the stock trailer, a trailer designed for cattle that is enclosed on the bottom, but has slits at roughly the eye level of the animals to allow ventilation. Trailers designed specifically for horses are more elaborate. Because horses are usually hauled for the purpose of competition or work, where they must arrive 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.

Jockey wheel

The term jockey wheel predominantly refers to a wheel-based mechanical system used for steering or guidance. It is either

a guide wheel - usually operating as a pair - which is used to move, retain, locate and (usually) add tension to a chain, rope or cable which is then fed into the groove of another wheel, toothed wheel, cog or sprocket;

a (frequently) retractable, smaller, height-adjustable wheel located on the front of a Trailer_(vehicle) or Caravan_(towed_trailer) for the low-speed manoeuvring or manual steering of said trailer-based unit when decoupled from the powered vehicle to which it was attached.

Liquid hydrogen trailer

A liquid hydrogen trailer is a trailer designed to carry cryogenic liquid hydrogen (LH2) on roads being pulled by a powered vehicle. The largest such vehicles are similar to railroad tanktainers which are also designed to carry liquefied loads. Liquid hydrogen trailers tend to be large; they are insulated. Some are semi-trailers.

Pusher trailer

A pusher trailer is a device attached to the rear of a vehicle or bike that provides force to assist the vehicle.

RENFE Class 490

The RENFE Class 490, also known as the ETR 490, is an electric multiple unit constructed by Alstom and Fiat Ferroviaria and operated by Spanish rail company Renfe Operadora on its Alaris long-distance services. Since the introduction of the Alaris service, only ETR 490 units have been used for this service. Therefore, these trainsets are often known as Alaris themselves. The units were the first actively tilting units to go into regular service in Spain.Unlike other members of the Pendolino rail family, the ETR 490 trainset is composed of only three cars: two motors vehicles, with driving cabs, and a trailer vehicle in the centre. Its motor system is similar to that of an electric multiple unit because its pantograph is not located on a locomotive. The motor cars on either end of the train contain a pair of motor bogies, with one asynchronous motors per bogie. Static and other converters are also located underneath the motor cars.

The central passenger car is divided into two spaces: half is passenger seating while the other part is a bar and restaurant. A section of this car is also dedicated to people with mobility and accessibility impairments. The dimensions of the ETR 490 are reduced compared to its Italian model. These dimensions favour aerodynamic stability and speed. The cars are also built out of lighter materials that allow the train to move faster and put less stress on the tracks. The power consumption of the Alaris trainset is considerably less than the Italian ETR 460, almost reduced by one third.The tilting mechanism of the ETR 490 is quite similar to that of the second and third generation Pendolino series, controlled by gyroscopes, devices measuring oscillation, and speedometres. The tilt is limited to eight degrees when fully activated when compared to a horizontal surface. Disk brakes control pneumatic and rheostatic braking.

Speed limits in India

Speed limits in India vary by state and vehicle type. In April 2018, the Union Ministry of Road Transport and Highways fixed the maximum speed limit on expressways at 120 km/h, for national highways at 100 km/h, and for urban roads at 70 km/h for M1 category of vehicles. The M1 category includes most passenger vehicles that have less than 8 seats. State and local governments in India may fix lower speed limits than those prescribed by the Union Ministry.

Tow hitch

A tow hitch (or tow bar) is a device attached to the chassis of a vehicle for towing, or a towbar to an aircraft nose gear. It can take the form of a tow ball to allow swiveling and articulation of a trailer, or a tow pin, or a tow hook with a trailer loop, often used for large or agricultural vehicles where slack in the pivot pin allows similar movements. Another category is the towing pintle used on military vehicles worldwide.

Truck classification

Truck classifications are typically based upon the maximum loaded weight of the truck, typically using the gross vehicle weight rating (GVWR) and sometimes also the gross trailer weight rating (GTWR), and can vary among jurisdictions.

Utility trailer

Utility Trailer may refer to:

Trailer (vehicle), an unpowered vehicle pulled by a powered vehicle

Utility Trailer Manufacturing Company, an American semi-trailer manufacturer


This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.