Plenty of drivers offer a helpful headlight flash to other motorists to signal an upcoming speed camera - but the gesture could get you in financial trouble.
Though the relatively common practice is regarded as polite among road users, it could land drivers with a hefty fine of up to £1,000.
The signal often warns fellow road users to a speed camera or police ahead - which Chronicle Live reports could be treated as a criminal offence.
This is because drivers who decide to flash in order to alert others of a speed trap executed by police could be in breach of section 89 of the Police Act 1997.
The law states that it is an offence to "wilfully obstruct a constable in the execution of his/her duty."
This means police could then 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 officer is capped at level three on the fine scale, with a maximum penalty of £1,000.
Even flashing your headlights to warn other drivers about speed cameras is against the Highway Code.
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.
