A leading windscreen repair firm says its workload has more than doubled in Whangārei and the North Shore since roadworks began in the north this season.
Smith and Smith's operations director Andre May said the company usually fixed about 100 cracked windscreens per week.
But in early November that suddenly shot up to more than 250 per week and he's had to fly extra staff up from the South Island to cope with demand.
Mr May said from time to time there was a spike in demand in the north usually related to roadworks on the Brynderwyn Hills but this year's spike was different.
"We have seen it before but never, never to this level. This is the sharpest we've ever seen it in terms of the speed and amount of the damage in such a short time."
Mr May said there's now about a two-week wait for windscreen repairs at Smith and Smith in Northland and some north Auckland branches.
Another company, Movus is reporting similar demand in Whangārei .
The Transport Agency is advising motorists to drive slowly through roadworks between Whangārei and Auckland and stay two car-lengths behind other vehicles.
But one Whangārei man who's been waiting 10 days for a new windscreen said that wouldn't have helped him.
Max Bognuda said a stone thrown by a car coming towards him made a sizeable hole in his windscreen that's developed into a large crack.
His warrant of fitness is due but he can't get one until the screen is replaced, he said.
"It's the time of year when everyone's travelling and vehicles are going to be driving around illegally because you can't get a screen and you can't get a warrant," he said.
Mr Bognuda, who's a retired architect, said the structure of roads in the north was unstable at the best of times, and road-workers should be watering the unsealed portions to reduce the risk of flying stones.
A Kerikeri man has told RNZ that extensive roadworks in the Far North were also wreaking havoc for motorists.
Chris Boyce said it was impossible to get windscreens fixed anywhere in the district until after New Year.
"My windscreen has failed my WOF and I will not be able to get it fixed until 21 January in Kerikeri. Novus and Smith & Smith in Whangārei are not answering or returning calls," Mr Boyce said.
Northland Regional Transport Committee chairperson John Bain said roadworks were a fact of life in summer - and there were plenty around this year.
"It's unavoidable - they have to fix the roads when the weather's good," he said.
"I've had about 25 broken windscreens in my time and usually they've come from a car coming towards me.
"But if everyone just stuck to the 30km/h speed limit through road works and resists the urge to speed up when you're getting towards the end, we wouldn't have a problem," he said.