Legal requirements for towing trailers

There is a legal requirement to ensure as far as possible, that trailers (and accessories) have been built, maintained, and are loaded and towed, in such a way as to ensure that no possible danger is caused to any person (driver, passenger, other road user or anyone else). 

This goes beyond just requiring drivers to comply with the letter of the law. Failure to comply with this 'duty of care' can not only result in a fine but also leaves you wide open to a civil claim made by any injured parties. 

The correct weight on the hitch

There should be about 50 to 100kgs of download on the hitch when it is attached to the vehicle. On a single axle trailer this is achieved by moving the load back and forward. It is more complicated on tandem wheeled trailers where the tow bar height is also critical.

The trailer must be towed level so the weight is carried evenly on both axles. Where the tow hitch on the vehicle is too low (often the case when the car is loaded with gear and passengers), the hitch can actually exert an upward lift and thereby so reduce the down force on the rear wheels of the vehicle that they will have only marginal grip to resist jack knifing. 


There are only two legal requirements for weights and loads: One is that you must not exceed the Gross Train Weight (GTW) that is shown on the manufacturer's ID plate under the bonnet and the other is that you mustn't exceed the trailer's 'Maximum Gross Weight'.


Technically, when towing a boat, all aft of the rear hull support on the trailer is an 'overhang' - not just the mast that sticks out beyond the transom. A red flag or streamer should be attached to the end of the mast. If this total overhang is more than two metres, an 'end marker board' should be substituted for the flag.


The regulations vary slightly depending on the age of the trailer and the width of the towing vehicle. Standard requirements:

The trailer board needs two red rear lamps, two stop lamps, number plate and light, two red reflectors, two amber indicators, one rear red fog lamp, two white forward facing reflectors.

In addition, if the trailer is more than 2.1 meters wide, it also needs white forward facing lamps on the trailer board or mudguards. The lighting board must be wide enough so the outer edge of the rear lights is within 150mm of the outer edge of the boat. This lighting board should be positioned within one metre of the end of the total overhang (which is often the mast), or otherwise the end of the overhang would have to be lit with an addition reflector and red lamp. The lighting board should not be more than 1.5 metres off the ground. The trailer also requires at least two amber reflectors down each side.


The same regulations as car tyres now apply to trailers, viz tread depth, etc. In addition, you cannot mix radial and crossplys at all on a tandem wheeled trailer.


Trailers built since 1983 must have overrun brakes on every wheel, worked from a coupling that is damped and matched with the brake linkage. The brake efficiency must be 45%. In addition, there must always be a working parking brake capable of holding the laden trailer on an 18% gradient (nearly 1 in 5 ). All trailers must have a break-away cable that will stop the trailer automatically if it becomes uncoupled.


Speed limits are 60mph on motorways and dual carriageways, and 50mph on other roads. You cannot use the outside lane on a three (or four) lane motorway.


Insurance cover for your boat when trailing is provided by a combination of your vehicle and boat policy. Liability for damage caused by the boat / trailer combination when attached to the towing vehicle (or after it has become accidentally detached), should be covered under the third party liability section of the vehicle policy. 

Tow hitch strength 

Check that the tow hitch and mounting on your vehicle is rated high enough for your intended load.

Driving licence

For those of people with licences issued before July 1, 1996, there is no change to the regulations. Drivers with licences issued after that date should seek advice from the DVLA: 01792 772151

Last updated: 19 December 2023 08:27:36

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