Derbyshire drivers can avoid hefty fines - thanks to a humble 20p piece.
Road safety chiefs are urging motorists to check their tyre tread depths once a month using the coin - boosting safety and preventing fines totalling thousands of pounds.
Mike Ashworth, chairman of Derby and Derbyshire Road Safety Partnership, said: "Your tyres can only keep you safe if they're in good condition - that's why you should check your tread depth every month by taking the 20p test.
"All you need to do is push a 20p coin as far as it will go into the main grooves of your tyre.
"If the outer rim of the coin is still visible, you should get your tyre checked as it may be below the legal limit.
"When taking the test, remember to check at least three locations around each tyre."
The legal minimum tread depth for cars in the UK is 1.6mm throughout a continuous band comprising the central three-quarters of the breadth of the tread and around its entire outer circumference.
For each tyre that is below the legal limit, motorists can be fined up to £2,500 and have three points added to their licence.
Mr Ashworth added: "We're also encouraging motorists to check their tyre pressures regularly.
"It's a simple maintenance job that makes the roads safer as well as making your tyres last longer, reducing your fuel bills and cutting your carbon emissions."
The advice comes during Tyre Safety Month.
For more information about tyre safety, visit www.tyresafe.org