Towing

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Towing is the process of pulling or drawing behind a chain, line, bar or some other form of coupling. Towing is most visibly performed by road vehicles, but anything from waterborne vessels to tractors to people can tow cargo. Troop carrying and cargo carrying gliders were towed behind powered aircraft during WWII and remains a popular means for modern leisure gliders to take off. In the maritime industry in particular, towing is a refined science.

Types of trailers

Almost any SUV, van, minivan, pickup truck, garden tractor or passenger car can be equipped to tow a trailer properly when given the correct equipment.

Most trailers fit into one of five categories:

• Flat bed or open trailers are platforms with no sides or stakes. This type of trailer works well for hauling large or unconventional shaped objects.
• Enclosed trailers are fully covered by four sides and a roof. These types of trailers are generally used for carrying livestock since they protect the contents from weather. People also rent these types of trailers for moving boxes, furniture and other materials.
• Boat trailers are used specifically for pulling boats. These types of trailers are designed for easy loading in and out of the water and are purchased based on the specific type and style of boat they will be hauling.
• Recreational vehicles (RV) are utility vehicles or vans that are often equipped with living facilities. These types of trailers can be attached to the back of most any road vehicle and are commonly used for camping outings or road trips.
• Tank trailers, which are trailers designed to contain liquids such as milk, water or motor fuel.

Towing safety

There are many safety considerations to properly towing a caravan or trailer / travel trailer starting with vehicle towing capacity and ranging through equalizer hitches to properly and legally connecting the safety chains.

According to the United States National Highway Traffic Safety Association, more than 65,000 crashes involving passenger vehicles towing trailers occurred in 2004 in the US, jumping nearly 20 percent from the previous year.

In 2006, Master Lock did their annual study on towing safety to see how many Americans tow their cargo correctly. The study, Towing Troubles included responses from trailer owners across the country and found that while the majority of trailer owners believe they know what they’re doing when it comes to towing, most were lacking the proper education. Master Lock reported that 70 percent of trailer owners did not fully know the correct way to tow their cargo.

An important factor in towing safety is tongue weight, the weight with which the trailer presses down on the tow vehicle's hitch. Insufficient tongue weight can cause the trailer to sway back and forth when towed. Too much tongue weight can cause problems with the tow vehicle.^[1]

Towbar Wiring

Vehicle Specific Towbar Wiring

Out of the thousands of cars on UK roads with towbars fitted, most are likely to have fitted towing electrics which are ‘hidden’ from the car. This electrical installation is commonly called ‘By-pass electrics’. This system is used to protect the car's lighting systems from potential damage if wiring in a trailer should malfunction. It is a tried and tested system in very wide use. Bypass systems are found both in "universal" (non-vehicle-specific) systems and in dedicated and OEM systems.

Since the early 2000s, vehicle technology has moved forward introducing CANbus network systems which allowed the interaction of different systems, and also the detection of a trailer or caravan. In some cases, the manufacturers have not only designed automobiles to sense the presence of a trailer, but they have also created enhanced new features within the systems connected to the network. This actually makes it important that these particular vehicles can "see" the trailer or caravan A few of these new features are for safety and stability, and most are merely convenience things like automatically switching off the rear fog light and parking sensors. The main new safety feature, appearing now on some cars, is the Trailer Stability Program which automatically turns on when detected in the network through the dedicated sensors.

Some of the advanced systems being introduced in certain vehicles, that may make use of detecting the presence of a trailer are: lane change assistant, brake electronics, adaptive cruise control, suspension system (ASS), engine electronics, engine cooling system, parking aids, and reversing camera.

TSP or Trailer Stability Program is one feature which has been added to some vehicles, to help correct the ‘snaking’ action of a trailer. With such advanced technology, some braking systems have even evolved further by being operated electronically, without the need for hydraulics. Braking can become more controlled with faster braking efficiency when towing. Some suspension systems can now detect a trailer and allow for a more level towing adjustment when the load is applied on the towing hitch. ACC (Adaptive Cruise Control) systems are meant to ‘detect’ a trailer in order to create a greater braking distance between vehicles. It might be considered unwise to bypass such vehicles' trailer detection systems as these vehicles may be designed to behave in a different way when a trailer is attached.

Some manufacturers either put a prepared connector in the vehicle which is a preparation on the network (Ford, Volvo) to accept a specially designed towing module, or have designed the trailer to be ‘detected’ through connections directly onto the databus (VAG, BMW). With such connections the vehicle will know when a trailer plug is connected to the socket.

On vehicles that do not have safety features that depend on the vehicle sensing the presence of a trailer, bypass systems, properly installed by expert fitters, are very efficient and cost effective alternatives to expensive OEM and other dedicated kits. All bypass kits will be type approved for use on vehicles (check for the (e) mark). They have the built-in advantage of completely isolating the trailer from the vehicle's lighting system, thus protecting against damage to the car caused by any failure within the trailer's wiring.

Universal By-pass Electrics

This system is used to protect the car's lighting systems from potential damage if wiring in a trailer should malfunction. It is a tried and tested system in very wide use. Bypass systems are found both in "universal" (non vehicle-dedicated) systems and in dedicated and OEM systems. It works by taking a small current signal from the vehicle's lighting harness to trigger a relay and send a direct power supply to the towing socket. It does not communicate with the vehicle and will not activate any safety or convenience systems. It has the built-in advantage of isolating the trailer wiring from that of the towing vehicle and thus protecting the car's wiring from damage should the wiring in a towed trailer malfunction. It is not advised for use in cars that depend on sensing the presence of a trailer to activate towing-related safety features within the car.(See Trailer Stability Programme)

12N, 12S or 13 Pin Sockets

12N is the designation for the older 7-pin lighting socket, used when towing just a trailer or caravan (without the need for charge or fridge functions). In the UK it has all the functions of the rear lights on a vehicle except for reverse. These sockets are not waterproof and suffer from "pin burn-out" when worn.

12S is an additional 7-pin socket mainly used when towing caravans. It consists of a permanent 12v power supply, and usually a switched 12v power supply for the fridge (UK). It also contains a feed for the reverse lights on the caravan.

13 Pin is the new ISO standard (ISO 11446) socket being fitted to all new caravans sold in 2009. It can be wired with the same functions as both the 12N and 12S sockets, or with just the lighting functions including reverse (required on all trailers and caravans from 2010). The socket has been designed to be waterproof, easy to fit/remove (twist operation), the same size as one 12N socket (ideal for detachable towbars as unobtrusive), and with good fitting quality terminals that avoid any pin burnout or voltage failure.

Trailer Stability Program or TSP

Another advance in trailer safety is the development of the Trailer Stability Program, built into some Electronic Stability Control systems in today's motor vehicles. These systems can detect the "snaking" of a trailer or caravan and counteract it by braking individual wheels, reducing engine torque and slowing the vehicle down.

Towing capacity

A Morris C8 towing a 25 pounder

Towing capacity is a measure describing the upper limit to the weight of a trailer a vehicle can tow. In the United States, towing capacity is expressed in pounds, while other countries express the limit in kilograms.

Some countries demand that trucks and buses have the maximum trailer weight and eventually maximum trailer length signed close to the coupling device, while this is rare with smaller cars or pickup trucks.

See also

• Gross combined weight rating
• Gross trailer weight rating
• Gross vehicle weight rating

Types of towing hitches

A tow hitch, tow bar or recovery point is a device attached to the chassis of a vehicle for towing.

It can take the form of a tow-ball to allow swivelling and articulation of a trailer, or a tow pin and jaw with a trailer loop - often used for large or agricultural vehicles where slack in the pivot pin allows the same movements. A further category is the towing pintle used for military vehicles around the world with a hook and locking catch.

See also

• Vehicle recovery
• Tow truck
• Tugboat
• Tow hitch
• Trailer Brake Controller
• Dolly (trailer) - supports the front wheels of a second vehicle
• Predatory towing
• Trailer stability program

References

• National Highway Traffic Safety Association

External links

• Factors affecting towing capacity
• Towing capacity changes
• Extensive searchable database of tow ratings from a camping magazine
• Fitting a Towbar