In all three places a trailer must have working lights and its own brakes if it is over 750 kg, and should show the towing car’s registration (Ireland’s RSA exempts trailers under 750 kg; the regulation does not). Fit towing mirrors whenever the trailer is wider than the back of the car. Braked trailers use a breakaway cable; unbraked ones a secondary coupling. In GB, towing without proper mirrors can mean a fine of up to £1,000 and 3 points.
The rules side by side
| Equipment | Great Britain | Northern Ireland | Ireland |
|---|---|---|---|
| Trailer brakes | Required over 750 kg loaded (GOV.UK) | Required over 750 kg (nidirect) | Service brake, handbrake and breakaway brake over 750 kg DGVW (RSA), and on any trailer over half the loaded car (S.I. 190/1963) |
| Breakaway cable or secondary coupling | One or the other, always (GOV.UK) | Same as GB | Breakaway brake on braked trailers; older ones may use a chain or wire rope (RSA) |
| Towing mirrors | If the trailer is wider than the rear of the car; up to £1,000 and 3 points (GOV.UK) | May be needed if wider than the car; up to £1,000 and 3 points (nidirect) | Extension mirrors if the trailer is wider than the car (RSA) |
| Number plate | The towing car’s registration (GOV.UK) | Same as GB | The towing car’s registration; the RSA says under 750 kg is exempt, the regulation does not (S.I. 318/1992) |
| Lights | All working and undamaged (GOV.UK) | Same as GB | Rear, stop, indicator, plate lamps and red reflectors; front white lamps over 1.6 m wide (RSA) |
| Maximum width | 2.55 m (GOV.UK) | 2.55 m (nidirect) | 2.50 m in the 2003 regulations as made (S.I. 5/2003) |
| Maximum length | 7 m behind a car of 3,500 kg MAM or less, not counting the drawbar (GOV.UK calls it the A-frame) | 7 m behind a vehicle up to 3,500 kg | Not covered here |
| Tow bar | Type approved on cars first used from 1 August 1998 (GOV.UK) | Same as GB | Not covered here |
| Annual test | Not covered here | Not covered here | Trailers over 3,500 kg only (CVRT) (RSA) |
Towing mirrors
GOV.UK: "Fit suitable towing mirrors if your trailer or caravan is wider than the rear of your car" (GOV.UK). nidirect is softer, saying "you may need to fit suitable towing mirrors", but carries the same penalty of 3 points and up to £1,000 (nidirect). In Ireland the RSA describes extension mirrors as "towing mirrors to be used when the trailer is wider than the towing vehicle" (RSA). Most caravans and many horseboxes are wider than the car, so in practice you need them.
Number plates
In the UK, "You must display the same number plate on your trailer as on your towing car" (GOV.UK). It is the car’s number, not a separate trailer registration, so swap it when you change cars.
Ireland is less tidy. The RSA FAQ answers "Does my trailer need a number plate fitted?" with "Yes, unless the DGVW is under 750 kg". The regulation it rests on has no such exemption: "a duplicate of the identification mark of the vehicle shall be exhibited on the back of the rearmost trailer" (S.I. 318/1992). Fitting one costs little and settles it.
Brakes, breakaway cables and secondary couplings
A trailer over 750 kg needs its own brakes in all three places. The breakaway cable on a braked trailer pulls the trailer’s brakes on if it comes off the ball; an unbraked trailer uses a secondary coupling instead, a cable or chain that keeps the drawbar off the road. GOV.UK: "You must use a breakaway cable or secondary coupling in case the trailer becomes detached from your car" (GOV.UK).
In Ireland the RSA says "Older trailers that do not have a breakaway cable can have a secondary coupling" (RSA). Its website and its booklet give different dates for which trailers count as older, so check with the trailer maker if yours is under 1,500 kg and has no breakaway cable.
Lights
GOV.UK’s pre-tow checks say to make sure there’s no damage to the lights and that they’re all working (GOV.UK). The RSA lists what an Irish trailer must carry: red rear lamps, red stop lamps, amber indicators, number plate lighting and rear red reflectors, plus white front position lamps if the trailer is over 1.6 m wide (RSA). Check them with someone standing behind the trailer before every trip, and make sure the plug is pushed fully home.
A-frames and dollies
nidirect: "If you attach an A-frame to a car to tow it with a larger vehicle, the car plus the A-frame count as a trailer", and the same for a dolly. "In both cases the usual Safety regulations for trailers apply" (nidirect). So the towed car needs a working brake system if it is over 750 kg, the lights, and the plate. GOV.UK’s towing page uses “A-frame” for the trailer’s own drawbar, "the frame that connects your car to the trailer", which is left out of the 7 m maximum length (GOV.UK). It says nothing there about towing a car on an A-frame in GB, and this guide does not cover that either.
What it costs to get wrong
In GB, using a vehicle in a dangerous condition can mean a fine of up to £2,500, a driving ban and 3 penalty points (GOV.UK). That covers the trailer and its equipment, not just the car.
Questions
- Do I need towing mirrors for a caravan?
- Yes if the caravan is wider than the back of your car, which most are. In GB towing without proper towing mirrors can mean a fine of up to £1,000 and 3 penalty points; nidirect gives the same penalty in Northern Ireland, and the RSA advises extension mirrors in Ireland.
- Does a trailer need its own number plate?
- It needs a plate showing the towing car’s registration, not a registration of its own. In Ireland the RSA says trailers under 750 kg DGVW are exempt, but the regulation itself has no exemption, so fit one.
- Do I need a breakaway cable on an unbraked trailer?
- No, an unbraked trailer has no brakes for a cable to apply. In GB and NI it needs a secondary coupling instead, a cable or chain that keeps the drawbar off the road if the hitch fails.
- Does my tow bar need to be type approved?
- In GB and NI, yes if the car was first used on or after 1 August 1998. A type-approved tow bar has a label with an approval number and the vehicles it is approved for.
- Does a car on an A-frame count as a trailer?
- In Northern Ireland, yes: nidirect says the car plus the A-frame count as a trailer, so the usual trailer safety rules apply.
Sources
- Towing mirrors: GOV.UK, Towing with a car, checked 3 November 2026.
- NI: towing mirrors: nidirect, Towing safety information, checked 3 November 2026.
- Ireland: mirrors when towing: RSA, Road safety advice and driver licensing rules for drawing light trailers (booklet), checked 3 November 2026.
- Trailer number plate: GOV.UK, Towing with a car, checked 3 November 2026.
- Ireland: trailer shows the car’s registration: Vehicle Registration and Taxation Regulations 1992, S.I. No. 318 of 1992, Reg. 9(8), checked 3 November 2026.
- Trailers over 750 kg need brakes: GOV.UK, Towing with a car, checked 3 November 2026.
- NI: trailers over 750 kg need brakes: nidirect, Towing safety information, checked 3 November 2026.
- Ireland: trailers over 750 kg need full brakes: RSA, Braking requirements for light trailers, checked 3 November 2026.
- Ireland: half the laden weight of the towing vehicle: Road Traffic (Construction, Equipment and Use of Vehicles) Regulations 1963, S.I. No. 190 of 1963, checked 3 November 2026.
- Breakaway cable or secondary coupling: GOV.UK, Towing with a car, checked 3 November 2026.
- Trailer lights and indicators: GOV.UK, Tow a trailer with a car: safety checks, checked 3 November 2026.
- Ireland: trailer lights: RSA, Laws on using light trailers, checked 3 November 2026.
- Trailer width and length: GOV.UK, Towing with a car, checked 3 November 2026.
- NI trailer width and length: nidirect, Towing safety information, checked 3 November 2026.
- Ireland: vehicle width: Road Traffic (Construction and Use of Vehicles) Regulations 2003, S.I. No. 5 of 2003, checked 3 November 2026.
- Type-approved tow bars: GOV.UK, Towing with a car, checked 3 November 2026.
- Ireland: roadworthiness tests for heavy trailers: RSA, Laws on using light trailers, checked 3 November 2026.
- NI: a car on an A-frame counts as a trailer: nidirect, Towing safety information, checked 3 November 2026.
- Towing equipment in a dangerous condition: GOV.UK, Towing with a car, checked 3 November 2026.
Guidance, not legal advice. Towsheet is independent and not connected with the DVLA, DVA, RSA or NDLS.