There have been a string of incidents where Z-nails have punctured tyres along state highways in the lower North Island, says an online traffic site moderator.

More than a dozen motorists had a long trip home on Monday night when their tyres were punctured by nails strewn across the Pioneer Highway (State Highway 56), south of Palmerston North.

The road was busy as nearly 15,000 speedway fans were headed home from the sold out Superstock Teams Championship Finals in nearby Robertson Prestige International Speedway.

Rhys Murrihy says he was driving back from the event just after 10pm when he noticed some cars parked up on the side of the road.

"We passed a couple going through then we heard bang, bang, pop. There was another guy just ahead of us, he pulled over with a flat tyre and one of the other guys came past and said there was another 10 [cars] just up by the Challenge service station just up the road," says Rhys.

The manager of Palmerston North tyre firm Tremaine Tyres and Wheels came to his rescue, bringing a spare wheel which helped him get back to Palmerston North, Rhys says. It would be nearly 3am before he made it home with two new tyres and $600 out of pocket.

He found two Z-nails - a double ended nail bent at two right angles - embedded in each of his front tyres, he says.

"It pretty much wrecked one tyre through the sidewall and the other tyre, that went through the middle so that could be repaired but since only had one spare, we had two flat tyres, so we were stuck on the side of the highway with nowhere to go."

Motorist Rhys Murrihy says his trip home on Monday night ended up taking five hours and costing $600 after Z-nails punctured both of his front tyres. Photo: Supplied / Rhys Murrihy.

Other motorists posting about the incident on social media also reported finding the distinctive building product in their tyres.

Kelly Fox, who runs the Traffic Updates - Horowhenua Kāpiti Wellington Facebook page, says she started seeing posts about punctures in the Longburn area just after the speedway event finished up.

"I look at my phone and there were three pending posts on the traffic page and [they] all said the same thing 'is anyone else having trouble with something puncturing tyres just south of Longburn?'," says Kelly.

"Instantly people started saying 'yip I've just run over Z-nails' or 'my daughters got a Z-nail in her tyre' and so [we] pretty quickly worked out that someone or something had dumped some Z-nails across the highway."

She estimated at least 20 vehicles had been affected by the nails. She says there had been three similar incidents all taking place in close proximity in the past year.

"A couple of months ago, it happened on SH3 at Awahuri, and last year it happened just south of Sanson on State Highway 1, it actually also happened on the Ōtaki Expressway not long after that opened up as well. They had to close the whole southbound lanes to cleanup all the Z-nails," says Kelly.

"That was deliberate you can just tell. It's not like someone lost a box off the back of a truck or something, they were spread far and wide."

The number of cars affected by the nails on a state highway at night meant the situation could have easily had tragic consequences, Kelly says.

"It could cause a crash, could cause a head-on [collision], people going off the road, all sorts of things. We all do stupid things when we're young or whatever but that's just got a lot of potential for a lot of danger. It's just really uncool."

The incident was a good reminder for motorists to make sure their spare tyre was in good condition, she said. Although, like Murrihy, other motorists had reported more than one puncture.

"It's just a message to hammer home you know, pun intented. Basically to make sure that you've got at least one spare tyre that's good to go and you've got your jack and that sort of thing. You never know what might happen, especially on a dark country road," says Kelly.

Motorist Jenni Prentice says she counted at least 11 cars on the side of the road as she drove past Longburn.

She says she tried to call the incident in to police's 555 number but gave up after 10 minutes on hold.

Central DCC senior sergeant Jeff Veale says police were not aware of the incidents and were not seeking anyone in connection to the punctures.

Bill Hickman/RNZ