Ben Huijs was in the back of a car heading into Wellington when he heard his friend say there was a car coming the wrong way.
Next minute the car in the right lane swerved in front of them to avoid the oncoming car.
He said it almost caused them to crash into the barrier.
Huijs said they soon passed a car that was sitting on the motorway facing the wrong way, looking "pretty smashed up".
They saw about three or four other cars parked up on the side of the road, some of which appeared to be dented.
Driver Fleur Koorey said she had her kids in the car with her as she drove home from Porirua, when she saw the car ahead of her braking.
Koorey was in the passing lane when she suddenly saw the white car heading toward her.
"I had to quickly swerve into the other lane to avoid hitting it basically, so yeah, slowed right down and yeah, it was a bit freaky," she said.
"I looked in my rear-view mirror and it was still going.
"It just happened so quickly."
Koorey was "stumped" as to how it ended up going the wrong direction, but said she'd once seen a car heading the wrong way down a nearby ramp at Grenada, so wondered if the driver could have done the same thing.
She was unsure how fast the car was going, but said she was doing 100km/h herself.
"The old adrenaline kicked in and stuff," she said.
Stephen Riden also witnessed the car going the wrong way.
"I was in the inner lane overtaking another car on a series of curves past Tawa, heading towards Wellington," he said.
"The white car was moving along the inner barrier but not at high speed."
Riden had to brake and move half out of his lane to avoid the car.
"It was a surprise to say the least."
Police said today they have still not had any luck finding the driver of the vehicle.
Anyone who saw the car or has information that may assist police in locating it is asked to email Constable Martin Kelly at mkaj73@police.govt.nz
