"It is unbelievably surprising they weren't critically injured.
"It was a very solid vehicle, like a Volvo SUV and it was really well-built - it had all the safety features.
"That's probably what saved any further injuries - the airbags had all gone off."
It is understood the pair had been Napier-bound but police could not confirm where they were from.
Acting Sergeant Tony Matheson said the pair were assessed by ambulance but "were not deemed to be critically injured".
"At this stage, it doesn't look like they're going to be going to hospital," he said.
"From what I understand, a car towing a caravan northbound a few hundred metres north of the Mount Bruce summit got into some difficulties with the caravan.
"Witnesses are saying it started fishtailing and eventually it's got worse and the caravan and the car were dragged off the side of the road to where they are now.
"The caravan is on top of the car."
Masterton Fire Service, the Eketahuna Fire Brigade, and Masterton police attended the crash.