Drivers across the UK face fines for a common gesture to other road users.
More than half of motorist on UK roads are unaware that flashing your lights to let other drivers know you are making way could result in a fine.
2,000 drivers were tested on their knowledge of the rules of the road as part of new analysis from findandfundmycar.com.
Other habits that could land drivers in hot water include beeping their horn in anger or pulling over to use their phone with the engine still running.
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Phil Morgan, Head of findandfundmycar.com, said: “While the chances of getting fined for doing any of the offenses are extremely low, they’re still not worth the risk.
"While some of the offences might not be commonly known, nobody wants to risk their safety or have to pay a hefty fine for something that they didn’t know was going to cost them, so it’s best to know these sooner rather than later.
“What may be considered a friendly warning to other drivers can actually have consequences. Speed cameras and police officers are there to keep everyone safe so it’s vital they are respected.”
The RAC added: “Headlight flashes should only be used to warn drivers of your presence on the road.
“Simply put, it’s open to misinterpretation (particularly as it means different things in other countries), so think carefully before you reach for the beams.”