Auckland drivers were treated to an odd sight during rush hour on the motorway this week, with a crew of NZTA workers spraying the road to cool it down.
A large truck with a water tank cruised down State Highway 20 from around 4.30pm on Monday, continually spraying water in front of it.
It caused traffic delays and NZTA warned people to drive carefully and take extra caution.
NZTA says it's only done it once before, during a very hot day last January.
"The road surface became quite tacky with bitumen sticking to car tyres and the underside of vehicles," Auckland system manager Andrea Williamson told 1 NEWS.
"We used water trucks to cool the road surface that day and we learnt from the experience.
"That’s why we were out proactively yesterday with water trucks before it became a problem on SH20."
Ms Williamson says it's a "very rare event" due to a particular road surface that was being used.
A thin layer of latex-modified bitumen had been sprayed on the road the night before, filling in cracks on the road surface and helping extend the road's life.
While normally any residue wears off within a week, Ms Williamson says hot weather and slow-moving vehicles can make it sticky.
"Spraying water cools the road surface to prevent this happening… We’ve been using this road treatment for about two years now and it’s only happened once before."
According to MetService, Auckland reached a high of 27.4C on Monday.
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