Commuters have vented their frustration on social media after sealing road works near Masterton appeared to unravel in 32C-degree heat yesterday, with southbound cars carrying sticky stones as far as Featherston.
NZTA, which is carrying out the works, says the process of car movement to embed stones is "challenging" in hot weather but it should be overcome by today.
Northbound motorists to Masterton endured 20-minute delays in the morning getting past road works near the Juken NZ processing plant and Cornwall Rd.
Pippa Cain posted she was late dropping her children at school and "heading home after 3 will be a nightmare".
But as the day heated up, cars lifted stonework, which scattered and accumulated in piles on the footpath of the Waingawa Bridge and into Masterton.
Nataha Hopkins posted that it was "bloody ridiculous -- I'll be surprised if it [the road] has any stones left at the end of the day".
Sam Ann said his car was still spitting out loose stones by the time he got to Carterton.
"These ones are bigger than normal too."
Tash Knofflock said her car was still rattling with stones by the time she got to Greytown, while Anita Wilson said her wheel arches still had stones in it as far as Featherston.
Ginny Myers said she suffered a crack in her windscreen from a loose stone.
Aroha Geange posted she had melted tar and stones under her car. "Ridiculous!" she said.
NZTA operations manager Marc Owen said they are monitoring the situation with CCTV and a road crew is using a water cart to cool things.
"It's a bit of a challenge in heat, very delicate, but it will settle down.
"Once it cools down tonight, they will sweep up.
"We have extra stone as well."
The road was sealed overnight, but it takes 24 hours for the chips to roll over and lock in.
"The traffic movement is part of the process," he said, explaining they adjust car movement to lock in the stones.
They could use a roller but "there's nothing as effective as cars".