Many drivers would think nothing of flashing their vehicle's headlights in a 'warning' to other motorists a mere matter of good manners.
The signal is usually meant to alert other road users to a speed camera or police ahead.
But drivers may not be aware that the headlight-flashing trick could see you being slapped with a fine yourself.
Chronicle Live has uncovered that even though it is seen as a helpful gesture it could land you in financial trouble.
Motorists can be slapped with fines of up to £1000 for flashing their headlights to warn others.
When it comes to warning other drivers about the speed cameras, the Highway Code states, under rule 110: "Only flash your headlights to let other road users know that you are there.
"Do not flash your headlights to convey any other message or intimidate other road users."
The Department of Transport warns a breach of Rule 110 and 111, which outline the rules of motorists flashing their headlights, could stand up in a court of law as evidence.
It won't lead to a conviction, but, if drivers warn others about a speed trap implemented by police, they could be in breach of section 89 of the Police Act 1997.
Under this law, it states that an offence is something that tries to "willfully obstruct a constable in the execution of his/her duty."
Therefore police could charge anyone who appears to be obstructing their ability to conduct speed checks on other motorists, with this criminal offence.
The maximum fine for obstructing a police office is capped at level three on the fine scale, with a maximum penalty of £1,000.
