Requirements regarding trailers used on the road are given in the Road Vehicles (Construction and Use) Regulations 1986, as amended (C&U) and the Road Vehicles Lighting Regulations 1989, as amended (RVLR). The following is a summary of the main requirements.

1. Weight
In the case of light trailers, that are less than 3500kg in maximum laden weight, there is not any specified relationship in UK law between the weight of the towing vehicle and the weight of the trailer.

For M1 category vehicles (motor vehicles used for the carriage of passengers and comprising not more than eight seats in addition to the driver’s seat) the maximum permissible trailer weight is quoted by the vehicle manufacturer. If this is exceeded it is possible that the Courts or Insurance Companies may take the view that this constitutes a danger.

The maximum laden weight of a trailer, which may be towed by a light goods vehicle depends on both:

• The stated gross train weight of the towing vehicle (GTW) and
• The vehicle manufacturer’s recommended maximum permissible trailer weight.

Neither the maximum permissible trailer weight nor the maximum gross train weight (the laden weight of the trailer plus the laden weight of the towing vehicle) should be exceeded.

It is possible that the stated gross train weight is less than the sum of the stated maximum permissible laden weight of the towing vehicle and the stated maximum permissible laden trailer weight. In this case the towing vehicle and the trailer must be loaded such that each does not exceed its individual maximum limit and the sum of both does not exceed the maximum gross train weight.

It is not a requirement to display a notice of the unladen weight of the trailer or the towing vehicle, unless the towing vehicle is either a motor tractor or a locomotive, as defined in the C&U.

2. Dimensions
If the towing vehicle has a permissible gross weight in excess of 3.5 tonnes the maximum width and length of the trailer are 2.55 metres and 12 metres respectively. If, however, the gross weight of the towing vehicle is 3.5 tonnes or less, then the maximum permissible width and length are 2.55 metres and 7 metres respectively. In both cases, the overall length of the towing vehicle and trailer must not exceed either 18m or 18.75m depending on the type of towing vehicle.

The definition in C&U of the overall length of a trailer makes it clear that the coupling device and draw-bar are not included in the length dimension. In the case of a caravan, where a protective box is mounted on to the front, which is supported on the draw-bar for the purpose of storage gas tanks, for example, this box is included in the overall length.

These requirements also apply to visiting vehicles. Under Regulation 4(4) Item 2 of C&U, we permit a vehicle to be brought into Great Britian by a person resident abroad, provided that the vehicle complies in every respect with the requirements relating to motor vehicles or trailers contained in:

• Article 21 and paragraph (1) of article 22 of the Convention on Road Traffic concluded at Geneva on September 19, 1949 and Part I,
• Part II (so far as it relates to direction indicators and stoplamps) and Part III of Annex 6 to that Convention; or
• Paragraphs I, III and VIII of article 3 of the International Convention relative to Motor Traffic concluded at Paris on April 24, 1926.

Therefore we provide visiting vehicles an exemption from the construction, equipment and maintenance of vehicle requirements specified in Part II of C&U but not from the requirements for Regulations 7, 8, and 10, which relate to length, width and height respectively.

There is significant harmonisation of regulation within the European Union and freedom of movement across boarders. European Council Directive 96/53/EC, Annex I, states the maximum authorised dimensions for certain road vehicles circulating within the Community. However Annex I relate to large passenger carrying vehicles, large goods vehicles and trailers with a weight of over 3500 kg. There are no specific requirements for light vehicles.

Article 3(2) permits Member States to restrict vehicles, not covered by Annex I, put into circulation in their own territory to be in conformity with their own national requirements.

The UK is permitted to refuse to admit vehicles into the UK if the dimensions exceed limits fixed by the domestic legislation, Annex 1 (1).

3. Brakes
Braking requirements are prescribed in Regulations 15 and 16 of The Road Vehicles (Construction &Use) Regulations 1986 as amended.

• A trailer with a maximum design laden weight of more than 750 kg must be braked.
• An inertia (overrun) type braking system may be used up to a maximum permissible laden weight of 3500kg.
• It is not permitted to use an unbraked trailer, the laden weight of which exceeds 50% of the kerbside weight of the towing vehicle.
• For trailers up to 1500kg laden weight, it is permitted to use secondary coupling, which in the event of separation (NOT failure) of the main coupling, will retain the trailer attached to the towing vehicle, prevent the nose of the trailer from touching the ground and provide some residual steering of the trailer.
• Above 1500 kg laden weight, the trailer must be fitted with a device to stop the trailer automatically in the event of separation (NOT failure) of the main coupling. This is normally achieved by a breakaway cable attached to the parking brake mechanism where the trailer becomes detached from the towing vehicle.

4. Lights
The requirements for trailer lighting can be found in The Road Vehicles Lighting Regulations 1989 as amended (SI No.1796). A copy can be obtained from The Stationery Office, or see Section 6 below.

5. Coupling devices (Tow Bars)
Any coupling device fitted to a passenger carrying vehicle with up to eight seats plus the driver that:

• a) has European Whole Vehicle Type Approval (ECWVTA) and
• b) that the manufacturer has authorised to tow a trailer and
• c) is first registered on or after 1 August 1998

must be type approved in accordance with EU Directive 94/20/EC. (Regulation 86B of the Road Vehicles (Construction and Use) Regulations 1986, as amended)

Modification to the coupling in any way, for example, by the addition of other devices that alter the position of the centre of a coupling ball, will render the approval invalid unless the coupling device manufacturer has taken this into account during approval of the device. You will need to consult the manufacturer for advice.

A vehicle that has ECWVTA will have a Vehicle Identification Number plate (VIN plate) bearing the vehicle manufacturer’s name, chassis number and an approval number including the letter “e” in a small rectangle.

If the manufacturer has not authorised the towing of a trailer by declaration during the type approval process, it is not permitted to fit a coupling device or tow a trailer.

6. Legislation
The Regulations referred to above may be obtained through the Stationery Office under the references, SI 1986 No.1078 for the Construction and Use Regulations and SI 1989 No. 1796 for the Lighting Regulations. However, there have been many amendments to these base Regulations and it is important to obtain all of these in order to have the current situation.

As an alternative, you may find it easier to visit a good, city based, reference library where there may be a copy of The Encyclopaedia of Road Traffic Law and Practice, published by Sweet and Maxwell. This publication tracks the amendments to legislation and presents them in an up-dated form. One of the volumes will contain both the Construction and Use and Lighting Regulations.

The RVLR amendments together with amendments to C&U from 1988 can be found as Statutory Instruments on the following web site: www.opsi.gov.uk.

7. Other considerations
The above information relates to basic construction requirements and some aspects of the use of trailers. In addition it is recommended that you check whether you have the appropriate Driving Licence entitlement and whether the vehicle or combination of vehicles requires a tachograph to record driver’s hours. The latter will apply to most vehicles and combinations of vehicles above 3500kg gross weight, where used for commercial purposes.

Vehicle towing Frequently asked Questions (applicable in the UK)