Driving with worn tyres can increase stopping distance seven times more than drink-driving, a new academic study has found.

Worn tyres can increase stopping distance seven times more than drink-driving does, according to the study

Worryingly, researchers at Cardiff University also found that even tyres on the legal limit of 1.6mm could increase braking distance by over a third compared to tyres in good condition with 4mm or more of tread.

The study, carried out by the Centre for Automotive Industry Research, found that consuming alcohol increases reaction time by 18% or 120 milliseconds on average. At 70mph, this would lead to an increased stopping distance of 12.4 feet.

However, the difference in stopping distance between tyres in ‘good’ condition and worn condition with just 1.6mm tread is an additional 89ft – up by 36%. But a car with this level of tread is technically legal and would pass an MOT.

Both Professor Peter Wells of the University of Cardiff and Halfords, which commissioned the research, said the study demonstrates that the current legal limit on tread is too low.

Professor Wells stated: “When we began the research, we didn’t know which of the two factors – alcohol or worn tyres – would have the largest impact on stopping distance as the data have never been compared before. To demonstrate that worn tyres increase stopping distance seven times more than alcohol is a significant finding. The research also highlights how dangerous supposedly legal tyres are when it comes to grip levels. In my opinion the current legal limit is too low.”

And the study found that it isn’t just braking distances that are impacted by worn tyres.

The professor continued: “Braking distances are an indicator of general levels of grip. So, if worn tyres increase braking distances by a third, we can reasonably assume that general levels of grip in the tyres are reduced by this amount too. Therefore, worn tyres will also have a significant impact on car control on the road in other situations, such as cornering. This means it is more likely that you’ll lose control of the car in the first place if you have worn tyres.”

Halfords – which conducts over 800,000 MOTs in the UK each year – added that it advises vast numbers of UK motorists that their tyres are dangerously low on tread, but many drive away assuming they must be fine if they’re legal.

Graham Stapleton, CEO of Halfords, added: “The reality is that their safety is already significantly compromised, and this will only increase as they experience more wear. Any tyres that receive a warning are likely to be illegal with just a few thousand more miles of motoring. A tyre with just 1.6mm of tread could be one small lock-up or pothole away from being illegal and this could even happen on the way back from the test centre, but the tyres may not be checked again until their next MOT.
“This study clearly demonstrates that current tread limits are just too low given how much grip is reduced, even when within legal limits.”