"The car went too far out on the edge."
"It caught the gravel on the side of the road and started to hang out and slide."
He said as the car gained grip it looked like the driver attempted to correct the "tailspin" but slid across the center line into the path of an oncoming truck and trailer.
"It came back on to the road just as the truck came over the over bridge at Erua."
"[The car] really didn't have anywhere to go after that."
The truck impacted the left hand side of the vehicle.
"They were hit square on."
"It went straight underneath the front of the truck."
The vehicle was shunted back between 30 to 40 metres before coming to a stop.
The car was folded in on itself. He said the occupants would have died instantly.
"The car was absolutely destroyed."
"If he had been a split second slower he would have gone over the bank and been knocked around a little bit, but he probably would have survived."
Although he did not have a close look at the state of the truck and trailer involved in the crash, the front underside and grill did appear damaged.
New Zealand Fire Service Area Manager Gary Ward stated the trucks driver was uninjured.
The police forensic services will inspect the remains of the car to determine the cause of the crash.
State Highway 4 was closed between State Highway 49 and State Highway 47 from 9.20am until 1.45pm yesterday.