WARNING: GRAPHIC IMAGES

An eyewitness to a shocking Pohuehue crash says the vehicle was driving up the hill “very fast” before it swerved off the road, missing the car in front by “inches”.

Michael Agamalis was driving in the opposite direction down the hill on State Highway 1 with his family when he said the vehicle hit an embankment and flipped.

“There was a lady and a kid, in the car in front of him, and what this guy’s done, he pulled to the left. And I just heard the crunch as the front of his car hit the dirt and we saw him hit and [the car] spiralled like a bullet coming out of a barrel.

 “It launched the car, it got air to the point where its engine went high-rev and that’s all you could hear and then you could just hear the crunching and the rolling of the car.”

He told the Herald there was no smoke, fire or fuel spillage that he could see.

“The front of the car where the front windshield was, was just crumbled in.”

Agamalis, who was driving back to Auckland, said if the vehicle had turned right instead of left he would have been hit “head on”.

“That’s how close we were, like he was on our right side and we saw him.”

He believed the car landed about 70m down the embankment.

The crash caused extensive traffic delays, with cars backed up southbound to Dome Valley, about 14km north of the crash, in Pohuehueon October 24. Photo / Photo / Auckland Rescue Helicopter Trust

“The only way to get him out is through [a] chopper. We saw a lot of fire brigade, and everything like that, a lot of ambulances coming up from the opposite way.”

He told the Herald his ex-partner, who was also in the car, was “distraught” but had to “keep it together” as she was behind the wheel.

 “It was traumatic.”

Agamalis did not know how many people were in the vehicle at the time of the crash.

“When I saw the car, it looked like the roof was caved in - like there was no support to stop that [the roof] from caving in.”

The crash has caused extensive traffic delays, with cars backed up southbound to Dome Valley, about 14km north of the crash, and northbound delays stretch back to the Johnstones Hill Tunnels

Traffic was gridlocked for 15km between Puhoi and Warkworth, with Google maps warning of an hour-plus delay for motorists travelling on this stretch of highway.

State Highway 1 Pohuehue, north of Auckland, was blocked following the crash and police said there would be “extensive delays”.

3 Michael Agamalis was driving in the opposite direction down the hill on State Highway 1 with his family when he said the vehicle hit an embankment and flipped. Photo / Supplied

Police were called to the single-vehicle crash about 12.20pm and one person has reportedly suffered serious injuries.

Traffic management is in place and motorists should expect delays as the southbound lane is blocked and a stop-go system is operating.

NZTA said the road was blocked near the intersection of Schollum Access Rd and Stop/Go traffic management is in place.

"Please follow the indications from emergency services on-site and expect delays."

Police asked motorists to avoid the area if possible and expect delays.

Holidaymakers returning to Auckland from Northland are advised to detour via Woodcocks Rd, West Coast Rd and on to State Highway 16.

A spokesperson said Auckland Westpac Rescue Helicopter assisted a man, believed to be in his 50s, around 12.41pm after his car had plummeted down a 300-metre bank and through Manuka trees just north of Puhoi.

“He was extracted from the vehicle and carried up the hill by fire and emergency with St John also assisting. He was flown to Auckland City Hospital in a critical condition,” the spokesperson said.