An 11-month-old baby girl has died after a single-car crash that blocked State Highway 1 north of Wellington.
The baby was flown to Wellington Hospital in a critical condition but died early yesterday evening, hospital spokesman Lindsay Davis said.
The baby's mother was still in a serious condition in intensive care while the father, who was ''absolutely gutted'', had been discharged, Davis said.
The accident blocked the northbound lane of SH1 near Raumati South for more than an hour yesterday afternoon.
The Serious Crash Unit was investigating the crash, police said.
The infant's death came as holidaymakers battled highway congestion as they headed to holiday spots for New Year's celebrations.
Worst affected yesterday was traffic travelling north from Auckland heading to the Bay of Islands, while the accident north of Wellington also caused severe disruption.
Traffic on State Highway 1 from Orewa to Warkworth, and then through Warkworth, was at a standstill from shortly before noon yesterday through to the mid-afternoon as thousands of cars headed north.
The New Zealand Transport Agency warned of "long delays" for holidaymakers, firstly due to the large volume of vehicles heading north.
Traffic was then brought to a halt shortly after noon following a three-car collision in the Dome Valley north of Warkworth.
One woman was airlifted to hospital in a serious condition, with several other people having minor injuries.
SH1 was reduced to a single lane for traffic both ways and motorists were told to delay their trip or use the alternative route of SH16.
A series of other crashes yesterday caused delays in Auckland and South Canterbury.
One person suffered serious injuries after a car rolled on the Southwestern Motorway near Mangere, South Auckland, early yesterday morning. Three other people suffered minor injuries.
The crash blocked the motorway until the debris could be cleared.
Several hours later another motorist was injured after their car rolled near the entrance to Middlemore Hospital.
In the South Island, a person was airlifted to Christchurch Hospital with serious injuries after a two-car crash near Geraldine, South Canterbury, just after 11am. A short time later, a cyclist suffered serious head injuries after being hit from behind by a car in Canterbury.
A police spokesman said the crash happened on State Highway 1, near the intersection of Grays Rd, near Amberley, about 12.45pm.
A Westpac Rescue Helicopter spokesman said they took a 59-year-old cyclist to Christchurch Hospital.
It appeared the man was hit from behind by the car, causing him to fly about 10 metres through the air, the spokesman said.
It was understood the man and his partner, who are from the North Island, were doing a cycle tour of the South Island.
Meanwhile, a motorist in the Hawke's Bay had a hair-raising experience after his car crashed into the back of a hairdressing salon in Havelock North about 12.30pm.
The driver, who suffered minor injuries, appeared to be the sole occupant of the car and no one in the salon was known to have been injured, police said.
The holiday road toll - which covers from 4pm on Christmas Eve to 6am on January 3 - last night remained at just one fatality.
Sandy Paul Waenga Brown, 21, died in the Far North on Christmas Day after the ute he was a passenger in rolled near Te Kao, on SH1.
Six people died and a further 70 suffered serious injuries on NZ roads during the 2012-13 Christmas period. The dead were made up o three drivers, two passengers and one pedestrian.
* An earlier version of this story incorrectly reported the baby girl's age as being 18-months. The article has been corrected.
- Sunday Star Times