POLICE CAN FINE DRIVERS WHO FLASH HEADLIGHTS TO WARN OF SPEED CAMERAS

Drivers who flash their headlights to warn oncoming traffic of a speed camera, police van or checkpoint risk prosecution and a fine of up to £1,000 under a law covering England and Wales. There is no specific criminal offence of flashing headlights to warn other drivers. Instead, police can bring a prosecution under Section 89 of the Police Act 1996. That law makes it an offence to "wilfully obstruct a constable in the execution of his duty."

Because officers are trying to catch speeding motorists, warning them so they slow down is treated in law as interference with police carrying out their duties. The maximum penalty is a month's imprisonment or a £1,000 fine. Rule 110 of the Highway Code states: "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." Rule 112 adds that a horn should be used "only while your vehicle is moving and you need to warn other road users of your presence." It also warns: "Never sound your horn aggressively."

Drivers have previously been prosecuted on this basis. Sentencing guidelines for the offence allow for penalties ranging from a fine and imprisonment to a conditional discharge or a community order. Evidence that police treat the offence seriously emerged in the weekly newsletter of a local primary school earlier in 2026. Many drivers who flash their lights to warn oncoming traffic believe they are doing a favour, rather than breaking the law themselves.