A woman driving to work told the Herald she saw a car driving on the wrong side of the motorway.
"My co-worker was also coming to work at this time and saw far more than me - [he] was trying to signal the driver to turn around."
The woman said her colleague had seen the car get onto the motorway via the Petone entrance before it "sped off".
"[My colleague] was trying to alert oncoming drivers by flashing high beams and hazard lights."
The woman got off the motorway at the Aotea off-ramp and did not see another vehicle.
"The crash seems to have happened just after that," she said.
"It would've been just before 4.30am as that is when I started work."
The woman said her colleague suspected there was a possibility the driver going down the wrong side of the motorway had become confused about where they were going.