The NZ Herald reported the group were spotted driving in Titirangi towards Glen Eden recently. A large fridge was perched on the roof of a two-door Nissan and to keep it in place, one man stood on the boot holding it down as another drove.
The bizarre move was captured on camera by a passenger in a vehicle behind the Nissan and posted on Facebook and Twitter.
Police are now keen to speak to the "brains" behind the operation.
"The consequences of injury to this person and other road users as well as potential damage to other vehicles is obvious," said the Waitakere police area commander, Inspector Scott Webb.
He said he would speak with staff after the long weekend to see if the matter had been reported and, if not, they would chase up the driver.
Road safety group Brake was unimpressed. "This behaviour is dangerous and totally irresponsible," said director Caroline Perry.
"They are not only putting themselves at risk, but also other road users, particularly more vulnerable users like pedestrians and cyclists. If something went wrong there could have been devastating consequences."
The photo follows several other high-profile incidents involving people riding inappropriately on the outside of cars.
In August, a video was posted on Facebook and Instagram showing a man "car surfing" on top of a taxi as it drove over the Auckland Harbour Bridge.
Waitemata road policing manager Inspector Mark Fergus said the prank was idiotic and reckless and was also being investigated by police.
"This sort of road use not only puts the 'pranksters' at risk of serious harm or death, but it also puts the safety of innocent road users in jeopardy, and the law-abiding public should not have to share the roads with people who choose to behave in this way," he said at the time.
The bridge footage was posted less than two weeks after two men handed themselves in to Tauranga police over another filmed alleged car-surfing incident.
Footage showed a 24-year-old going through a roundabout, around bends and travelling over a small hill while clinging on to a moving vehicle. He and the camera person later went to the police station.
By Anna Leask of the NZ Herald
