Four crashes on the same stretch of a rural Waitakere road over the past week - one resulting in serious injuries - have prompted a warning to motorists to beware of a treacherously slippery surface.
The city council says 10 accidents on a bend in Candia Rd, between Swanson and Henderson Valley, have been reported in the five years to December, and in four of them people were seriously injured.
But concerned residents say four or five times as many must not have been reported.
The past week's most serious crash happened on Wednesday, when a Henderson teacher on her way to work lost control of her car, which rolled and was struck by an oncoming vehicle.
She was taken to Auckland City Hospital with serious injuries.
Near the Henderson Valley spot early on Friday, police found a car that had hit a tree. The driver was missing.
"In the past 12 months we have attended three there. We don't know how many other minor-injury or non-injury accidents there have been," said Sergeant Stu Kearns, of the Waitemata police serious crash investigation unit.
"Each time, we have brought council engineers down to the scene and discussed with them what can be done about the road. The bend causing problems is a moderate one in a 70km/h area, and the council has put up a 30km/h advisory and slippery-when-wet signs."
Mr Kearns said a contributing factor to crashes was a slippery surface caused by a combination of the weather and the road.
Over summer dry periods, the bitumen melted and came up to the surface layer of stone chips in an action known as "flushing". It became slippery in last week's rain.
Residents Michael Pepper and Marguerite and David Crickmer called for traffic-calming measures to slow drivers coming into the bend after a long straight.
"It has become busy with people using it as a bypass of congested city streets between Swanson and Glen Eden," said Mr Crickmer.
"It should be 50km/h when there are horses, walkers and joggers and no footpath."
Waitakere City Council traffic safety spokeswoman Kitch Cuthbert said staff were to visit the winding, downhill 500m section at the weekend to clean the road surface and replace markers.
The road is on the council's "black spot" list for investigation, which could result in rebuilding and resurfacing to give a solid foundation for traffic.
About 5000 vehicles a day use Candia Rd, and over five years it has been the scene of 54 crashes along its length, most of them in wet weather.