Police end debate on flashing headlights to warn of speed camera

You've probably found yourself in a scenario where an approaching driver has abruptly flashed their headlights at you. Instinctively you understand what it signifies: there's likely a speed camera, van or other police presence further along the road. You might consider your fellow motorist has done you a favour by alerting you. In reality, they've exposed themselves to the risk of prosecution and a £1,000 fine. This isn't merely a theoretical possibility either — motorists have faced prosecution for flashing their lights to alert others.

But will police really punish you for trying to warn your fellow drivers? Their actions give an emphatic answer, reports Wales Online . Highway Code Rule 110 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." Additionally, Rule 112 of the Highway Code cautions that your horn should only be used "only while your vehicle is moving and you need to warn other road users of your presence" and states: "Never sound your horn aggressively."

There isn't a specific criminal offence of "flashing headlights to warn others". Nevertheless, police in England and Wales would bring charges under Section 89 of the Police Act 1996 , which makes it an offence to "wilfully obstruct a constable in the execution of his duty." Since officers are actively attempting to catch speeding motorists, alerting drivers so they momentarily reduce their speed is legally regarded as interfering with police duties.

The maximum penalty for this offence is one month's imprisonment or a £1,000 fine. According to sentencing guidelines, sanctions could range from a fine and imprisonment to a conditional discharge or community order. It's important to note that police take this matter seriously. Evidence of this emerged, surprisingly, in the weekly newsletter of a local primary school from earlier in 2026. In the newsletter, the school cautioned that "several people are warning other motorists" about the presence of a Cheshire Police speed van that had recently been positioned to monitor traffic speed outside the school.

The school stated police were warning that this behaviour breached both Highway Code Rule 110 and Section 89 of the Police Act 1996 and that they "could charge anyone who appears to be obstructing their ability to conduct speed checks on other motorists by warning them", noting: "The maximum fine for obstructing a police officer is a penalty of £1,000." Furthermore, the Crown Prosecution Service (CPS) in its official guidance on Public Justice Offences lists "giving a warning to other motorists of a police speed trap ahead" as an example of an action that would constitute resisting or wilfully obstructing a constable in the execution of their duty.

In a 2005 case, DPP v Glendinning, a lorry driver was observed flashing his headlights at oncoming motorists after spotting a speed camera van on a dual carriageway. Officers witnessed this, concluded he was intentionally alerting drivers and charged him with obstructing police. The driver was initially convicted, though this ruling was overturned at the High Court, where judges said there needed to be evidence of actual obstruction, not just the possibility that obstruction may have occurred.

In this particular instance, the High Court determined there was no evidence that approaching vehicles were speeding, that drivers had altered their behaviour as a result of being flashed, or that police enforcement operations had been genuinely disrupted. Nevertheless, the prosecution leaves no doubt that police will take motorists to court for flashing their headlights to alert others to speed cameras ahead.