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Legal Requirements for trailers

from Western Towing –

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


In the case of light trailers, that is less than 3500kg 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. Alternatively, the vehicle manufacturer may provide a maximum gross train weight (the laden weight of the trailer plus the laden weight of the towing vehicle). 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 or 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 Road Vehicles (Construction and Use) Regulations 1986.


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 2.3 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.


Braking requirements are prescribed in Regulations 15 and 16 of The Road Vehicles (Construction & Use) Regulations 1986 as amended and essentially require a trailer with a maximum design laden weight of more 750 kg to be braked and allow an inertia (overrun) type braking system to 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 a 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 and this is normally achieved by a breakaway cable attached to the parking brake mechanism – the trailer becomes detached from the towing vehicle.


The requirements for trailer lighting can be found in The Road Vehicles Lighting Regulations 1989 as amended. A copy can be obtained from The Stationery Office, or see below.


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 updated form. One of the volumes will contain both the Construction and Use and Lighting Regulations.

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 that 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.


For Driving Licence enquiries contact:
DVLA on 0870 240 0009

For Tachograph requirement enquiries contact:
VOSA on 0870 606 0440

For guidance on tachograph and drivers’ hours rules please see Rules on Drivers’ hours and tachographs (Adobe PDF – 2MB).

Fact sheet issued by

DTLR Vehicle Standards and Engineering Branch VSE 4, Telephone 020 7944 2078.


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