RoadSafe

TREAD DEPTH

Treading carefully

As research shows significant increases in stopping distances in the wet when tyre tread depth is below 3.5mm, the Tyre Industry Council is alerting drivers to the danger

Stopping distances increase when braking with tyres with a tread depth below 3.5mm

“The Forum is another platform to increase public awareness that motorists can contribute to saving their own and the lives of other road users”

A major education campaign has been launched by the Tyre Industry Council after car braking tests revealed significant increases in stopping distances on wet roads when tyre tread depth dropped below 3.5mm. Now the Tyre Industry Council (TIC), a not-for-profit, non-commercial body, funded by tyre manufacturers and the majority of UK tyre retailers, is calling for motorists not to wait until tread depth reaches the 1.6mm legal minimum across the central three-quarters of the breadth of the tyre and around the entire circumference before they replace tyres.

However, the organisation has fallen short of calling for the legal minimum tyre tread depth to be increased to 3mm, although it says that fleets and private motorists should use the measure in promoting safer motoring and corporate responsibility. Nevertheless, in the light of the independent tests commissioned by the British Rubber Manufacturers’ Association and carried out at the Motor Industry Research Association, the Royal Society for the Prevention of Accidents (RoSPA) has agreed to adopt 3mm of tread depth as its recommended level for tyre changes. In addition, RoadSafe director Adrian Walsh is chairing and managing a new Tyre Safety Forum, where interested parties, including the tyre industry, road safety campaigners and the police, can share an understanding of the role of tyres in road safety and co-ordinate and communicate initiatives and actions, as well as carry out lobbying and public awareness programmes.

Mr Walsh says: “In the context of driving in the wet, the Forum is another platform to promote road safety and increase public awareness that motorists can contribute to saving their own and the lives of other road users.” The tests involved measuring the stopping distance and cornering performance of five sets of tyres of different tread depths fitted to an ABS-equipped Volkswagen Golf 2.0 TDi driven on two different wet test surfaces.

The braking test results revealed that significant increases in stopping distances in the wet began to appear below 3.5mm. Compared with the reference tyre with tread at 6.7mm, stopping distance increased by 30% with 3mm of remaining tread and by more than 50% with only 1mm of tread – below the UK legal minimum. At 70mph in dry conditions, the stopping distance of a car fitted with a new tyre with 8mm of tread is calculated to be almost 100 metres; with 3mm of tread remaining a car’s stopping distance increases to 150 metres; with 1.6mm of tread remaining a car’s stopping distance is 200 metres – double that of a vehicle with a new tyre – and with just 1mm of a tread, a car’s stopping distance is 250 metres.

Wet conditions cause problems for cars with defective tyres

“It is unfair to suggest that the tyre industry is recommending tyres are changed at 3mm for purely commercial reasons”

Latest TIC figures show that 11% of cars and vans on UK roads have at least one defective tyre and a further 11% of vehicles checked had at least one tyre below 2mm. Kevin Clinton, RoSPA’s head of road safety, says the organisation was recommending that motorists changed their tyres at 3mm because the research produced compelling scientific findings that stopping distances increased markedly when tyre tread depth dropped below 3.5mm. And, defending the tyre industry against accusations of profiteering, with the UK minimum legal tyre tread depth being 1.6mm, Mr Clinton says: “The tyre industry has already compromised by basing its education and awareness campaign on 3mm and not 3.5mm. “The tests have provided a good scientific basis for improving road safety and in this case it is unfair to suggest that the tyre industry is recommending tyres are changed at 3mm for purely commercial reasons.”

The TIC recommends that motorists check the tread depth and pressures on their tyres frequently, at least once a month. A spokesman adds: “The research reinforces our view that drivers should consider replacing tyres well before they reach the minimum legal tread depth. With 300,000 road accidents taking place each year, if motorists replace worn tyres sooner, stopping distances can be dramatically reduced, road accidents prevented and lives can be saved.” The organisation operates a roadside tyre check programme with the support and assistance of UK police. A TIC spokesman says: “These checks have been highly effective in reducing the number of illegal and defective tyres on the UK’s roads. Overall, the percentage of dangerous tyres on UK roads has fallen dramatically, from 17% six years ago, to 11% today.” The current fine for driving on illegal tyres is £2,500 per tyre and three points on a driving licence.

Copies of the full MIRA report – An investigation into the Effects of Tyre Tread Depth on Wet Road Braking and Cornering Performance (MIRA-1002250) – can be obtained free of charge from the BRMA at: 6 Bath Place, Rivington Street, London EC2A 3JE - Tel: 020 7457 5040

RoadSafe calls for care

The RoadSafe organisation is calling on fleet managers to “tread carefully” this summer following independent research undertaken by MIRA (formerly the Motor Industry Research Association), which reveals that braking performance deteriorates in wet conditions when tyre tread depth drops below 3mm. Although the legal tread depth limit is 1.6mm, a threshold set by motoring experts some 13 years ago, RoadSafe says that there is now compelling evidence that motorists should check and change their tyres at 3mm.

Road accidents where wet conditions are a contributory factor are on the increase, the road safety partnership says. “A disproportionately high number of road accidents occur in the wet. Let’s not forget last summer was one of the wettest on record,” says RoadSafe’s chairman Adrian Walsh. “It’s a well known fact that in wet conditions braking distances substantially increase. A third (33%) of all road accidents already occur during the summer months. “With heavy downpours and flash floods becoming a permanent fixture of an English summer [in 2004 average summer rainfall increased to 314.9mm], there is every possibility this figure could rise over successive years.”

<<back to contents page