The post has received dozens of replies, some comical and some offering warnings.

“Last time I did that, I got followed to the dairy [by the other motorist] and got asked ‘What’s your problem?’,” said one respondent.

Other drivers said they flashed their headlights to slow speeding motorists, even if there wasn’t a police officer in sight.

Another claimed to have flashed his lights, only to discover it was an undercover police car.

There is no law that superficially states the practice is illegal.

But there are some clauses in the Land Transport Act and Summary Offences Act – such as endangering safety or avoiding detection – that might still trip up motorists.

“While there is no law against flashing your headlights at oncoming traffic, police discourage this, as it may blind drivers or obstruct their vision,” says a police spokeswoman.

“Every second on the road counts and one split moment can result in an accident.”

AA spokesman Dylan Thomsen said the AA did not condone the practice – it would prefer lights were flashed for true hazards only.

“The AA wants all drivers to be aware and adhere to the road rules, this means no one is speeding in the first place.”

The organisation seemed to back up the social media post.

“It’s not something that can be easily measured to know for sure but, anecdotally, flashing lights appears to be less common now than it was in the past. That’s likely to vary in different places and at different times though,” said Thomsen.

The organisation believed that road safety would be enhanced if it was used more rarely, for true hazards.

“…a driver may have recently gone past a broken-down vehicle on the road or some other hazard, or it could be farmers moving livestock or another unexpected situation.

“If flashing lights is rarely done then they could do it to oncoming traffic to help alert them that they are approaching a hazard and to be extra cautious and ready to react.”

New Zealand’s road toll for 2024 stood at 245 as of Wednesday morning. With just over a month to go until the end of the year, the country is on track for its lowest annual road toll since 2013. Last year, 341 people died on New Zealand roads.

Thomsen said a “bigger influence” on road safety was a high police presence.

“If people see police regularly and frequently when they are driving it will make many more people focused and careful about their behaviour.

“The police have put in a big effort over the last year to increase enforcement, particularly around drunk driving and speeding, and the AA thinks this is one of the reasons that New Zealand is on track to have our lowest road toll in a decade.”

Ironically, the original social media comment was posted on a Facebook page set up to warn motorists about the location of checkpoints and other police patrols. The page has almost 100,000 followers.

Perhaps that’s the modern-day version of the flashing headlights.

Editor-at-Large Shayne Currie is one of New Zealand’s most experienced senior journalists and media leaders. He has held executive and senior editorial roles at NZME including Managing Editor, NZ Herald Editor and Herald on Sunday Editor.