New drivers often focus on the test and forget that the car under them has to be roadworthy. Tyres are the only part of a car in contact with the road, and the law sets specific standards for them. This article summarises the Highway Code’s Annex 6 on vehicle maintenance, the government’s THINK! vehicle safety checks page, and a National Highways press release published on GOV.UK on 8 April 2022. The Highway Code applies to England, Scotland and Wales; Northern Ireland is not covered by that version. This is general information, not legal advice.
The legal minimum tread depth
The Highway Code says cars, light vans and light trailers MUST have a tread depth of at least 1.6mm across the central three-quarters of the breadth of the tread and around the entire circumference. The capital letters signal a legal requirement. Different figures apply to other vehicle types: the same Annex says motorcycles, large vehicles and passenger-carrying vehicles MUST have a tread depth of at least 1mm across three-quarters of the breadth of the tread in a continuous band around the entire circumference, and that mopeds should have visible tread.
The measurement applies across the central three-quarters of the tread and all the way round, so a tyre worn in one patch can fall below the limit even if another part looks fine.
Pressure, cuts and other defects
Annex 6 says tyres MUST be correctly inflated to the vehicle manufacturer’s specification for the load being carried, and to refer to the vehicle’s handbook or data. It adds that tyres should also be free from certain cuts and other defects. On checking, it says pressures should be checked weekly, before the journey and when the tyres are cold, because warm or hot tyres can give a misleading reading. It says brakes and steering are adversely affected by under-inflated or over-inflated tyres, and that excessive or uneven wear may be caused by faults in the braking or suspension systems or by wheels that are out of alignment, which should be corrected as soon as possible.
The THINK! page makes a similar point: driving with under-inflated or over-inflated tyres can adversely affect braking distance, steering, fuel efficiency and the lifetime of the tyres.
What the penalty is
THINK! says that anyone stopped by the police and found with illegal tyres could receive a £2,500 fine and 3 penalty points per tyre. The same wording appears in the National Highways press release. The Highway Code adds a general note that some vehicle defects can attract penalty points. Because the figure is stated per tyre, more than one illegal tyre can lead to a larger total. The site’s article on the New Drivers Act explains why penalty points matter especially in the first two years after passing.
It is the driver who has to be sure the tyres are legal. A person who has just bought a first car should not assume that the seller or the garage has checked them; the site’s guide to buying a first car covers the GOV.UK checks for a used vehicle.
Advice beyond the legal minimum
National Highways’ traffic officer said in the 2022 release that although the legal limit for tread depth is 1.6mm, drivers should not let the tread get that low, and described changing the tyre at 2mm in summer and 3mm in winter as good practice that maintains overall tyre performance in all conditions. That is advice from National Highways rather than a legal requirement. The same release advised checking tyre pressure, tread depth and tyre age, including the spare, before a long journey, and looking for cuts or wear over the full width of the tyre and on the sidewall. It also reported research commissioned by National Highways that only one in six drivers check their tyres before setting off on a long journey, and separate figures showing that a fifth of motorway breakdowns are caused by worn or incorrectly inflated tyres. Both figures date from that 2022 announcement.
The Highway Code also covers what to do when something goes wrong: if a tyre bursts while driving, try to keep control of the vehicle, grip the steering wheel firmly and allow it to roll to a stop at the side of the road. With a flat tyre, stop as soon as it is safe, and only change the tyre if that can be done without putting anyone at risk; otherwise call a breakdown service.
Tyre age
Annex 6 includes rules on tyres over 10 years old, but they apply to specific vehicle types: they MUST NOT be used on the front axles of goods vehicles with a maximum gross weight of more than 3.5 tonnes or passenger vehicles with more than 8 passenger seats, and there are further restrictions for minibus-type vehicles. These rules do not apply to an ordinary car, although the National Highways advice to check tyre age applies to all vehicles.
Common questions
Is 1.6mm the same for every vehicle?
No. The Highway Code gives 1.6mm for cars, light vans and light trailers, and 1mm for motorcycles, large vehicles and passenger-carrying vehicles.
Where on the tyre is the tread measured?
Across the central three-quarters of the breadth of the tread and around the entire circumference, according to the Highway Code.
The bottom line
In England, Scotland and Wales the Highway Code requires car tyres to have at least 1.6mm of tread across the central three-quarters of the tread and around the whole circumference, and to be correctly inflated for the load. THINK! says illegal tyres can bring a £2,500 fine and 3 penalty points per tyre. National Highways recommends acting before the legal limit is reached, but that is advice, not law.
Sources
- GOV.UK, “The Highway Code: Annex 6. Vehicle maintenance, safety and security”
- THINK!, “Vehicle safety checks” (think.gov.uk)
- National Highways via GOV.UK, “Motorists urged to check tyres and journeys before setting off this bank holiday”