NZTA also warned traffic delays were expected from December 24 to December 30 on SH1 northbound through Puhoi, Warkworth and Wellsford.
Traffic north of Wellington was also reported to be heavy, with congestion on SH1 between Peka Peka and Ōtaki.
To add to the misfortune, forecasters have warned of wild weather and heavy rain throughout the north.
Bad weather is likely to complicate driving conditions as heavy rain falls across part of Auckland and thunderstorm warnings are in place for parts of the country.
A severe weather watch is also in force the Bay of Plenty and Rotorua, which could mean heavy rain at times, and possible isolated thunderstorms are on the way.
The MetService said the watch included the Waikato, Coromandel Peninsula and northern Gisborne, Northland and Auckland, including Great Barrier Island.
Yesterday, police urged New Zealanders to take care on the roads after a horror 24 hours.
Four people died in separate crashes from Friday night to Saturday afternoon.
Superintendent Steve Greally, national manager road policing, described the deaths as a "truly horrific start to the holiday season".
"Police are extremely saddened by the four deaths that have occurred on our roads over the last 24 hours," Greally said.
"We cannot imagine how this will impact the families of those involved at what is supposed to be a happy time of year. Our hearts go out to them.
"The last thing police want to do is turn up on a loved one's doorstep in the days before Christmas and tell them someone is dead."
Greally said motorists had to realise they needed to take on the responsibility that came with being on the road.
"This means giving driving your full attention, always wearing your seatbelt, and not driving drunk, drugged, or fatigued," he said.
"With more people on the roads over the holiday season, and with bad weather forecast for a number of regions in the coming days, it's also crucial that you drive to the conditions.
"We want everyone to make it where they're going safely, and to be around to spend the holidays with their loved ones."
A Chinese international died after a crash near Mount Cook yesterday afternoon in which five others were injured.
Police said in a statement the man was 62-year-old Ying Han of Shanghai, China. The crash happened on Mount Cook Rd north of Twizel.
Emergency services were called to the serious crash about 2.10pm. The road was closed for several hours and diversions put in place.
The Serious Crash Unit is investigating.
South Island emergency services also responded to a two-vehicle crash in Clutha which left a person trapped yesterday afternoon.
Lakeside Rd, Lovells Flat, was closed as emergency services attended the incident after being notified about 2.40pm.
Those incidents follow three fatal crashes elsewhere in the country in the previous 24 hours.
One person died in a crash on Banks Peninsula yesterday afternoon.
A police spokesperson said the sole occupant of a car died in the noon crash in Okuti Valley, 50km southeast of Christchurch.
"A car went over a bank on Bossu Rd ... the sole occupant of the car has been confirmed deceased," the spokesperson said.
The Serious Crash Unit was investigating.
Another person died in a single-vehicle crash shortly before 4.30am yesterday on Te Puna Rd, near Tauranga. A second person was critically injured in the crash. Police confirmed the deceased to be 21-year-old Tarandeep Deol, of Tauranga.
A man died in a single-vehicle crash on Christchurch's Southern Motorway just before 9pm on Friday. The man, who died at the scene, was the only occupant of the vehicle, police said.
