The police did not know why the vehicle had been parked on the side of the highway, he said.
Maungatapu Rd resident Brett Jobson said he had heard the loud bang and thought it sounded like the thud of cars coming together.
"You could tell it was a car crash straight away," he said.
Timothy Way said he received a call from his mother shortly after the crash.
"She said she'd had an accident. She sounded pretty shocked and pretty freaked out."
North-bound traffic was limited to one lane and south-bound traffic was diverted on to the overbridge and through Maungatapu as the two vehicles were removed and police worked to clear the area.