Almost three quarters of all cars are being driven with underinflated tyres, according to the results of the biggest-ever tyre safety survey.
The survey for tyre safety organisation TyreSafe also showed that 25% of these vehicles have a tyre that is either illegal (having a tread depth of less than 1.6mm) or badly worn.
Severely deflated tyres can badly affect a car's handling and lead to a potential accident.
Government statistics have shown that underinflated or defective tyres are responsible for more than a third of all road crashes resulting in injury.
Underinflated tyres can also cost you money because they create increased fuel consumption and can also increase carbon dioxide emissions - up to 5.5 million tons a year, in fact.
90% of motorists don't know their car's tyre pressures, so look in your car's handbook if you're not sure.
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