The "terrifying moment, resulting in devastation" happened as he and his family were travelling west from Katherine to Kununurra.

"We were following another caravan, while travelling at approx 95-100km/h, when a 200 series Sahara with full 'van began to overtake us," Kane Gray, a member of Caravan & Camping Australia, wrote.

"I immediately said to my wife that it wasn't great idea. We were following another 'van, and we were approaching a bridge. We've seen plenty of hairy moments on the roads during this trip that have ended fine, most of them being extremely close calls.

"As he passed us, he seemed to accelerate more, causing the 'van to start to sway. I saw what was happening and began slowing.

"The 'van sway increased more and more, and it appeared like he tried to accelerate out of it.

"His 'van only missed the 'van in front of us by millimetres (honestly don't know how it didn't clip the 'van).

"At this stage, the sway was too much and he lost complete control, flicking back in front of the car/'van in front of us, jackknifing and spinning out. The 'van and car flipped over a guard rail and landed upside down. Another 20m further, he would have flipped over the bridge.

"My young girls were literally screaming, and everyone was obviously panicked.

"I pulled up and my wife attempted calling triple 0, but with no reception needed to flag down a passing car and send them back for reception.

"But the other car had pulled up, the couple traumatised and extremely upset.

"I ran down to the scene, engine still running, certain I was going to find bodies.

"I was calling out, without any response.

"Huge white smoke started to come out of the grass and initially I retreated, thinking the car was on fire.

"The engine cut out and the smoke dissipated ... I'm now thinking it was white smoke from the diesel engine being on its side.

"With that, a foot came through the windscreen and a couple in their mid-late 60s climbed out.

"She seemed to be ok, although definitely in shock. He had a few deep cuts on his hands and legs.

"By now, a couple of motorists had pulled up and started to assist, most continued on pretty quickly.

"A passing truck driver had a satellite phone and started calling for help. My wife helped him with the details and stayed with the lady, reassuring her, as she was in quite a lot of shock.

"The 'van and car were now a complete mess, and frankly we're all stunned they walked out of it, although the extent of their injuries is not yet known.

"The 'van wheel had snapped all together, leaving deep gouges in the road.

"We waited for over an hour with them. A passing by emergency nurse then stopped and checked out the couple whilst waiting for help.

"We helped salvage what we could of their personal items, and with the truck driver and nurse willing to stay until emergency services arrived, we decided to continued on our journey as it would soon be getting dark, and with more than 4hrs to go, it was the safest option for us.

"Fair to say, we travelled the rest of the way to Kununurra at a very slow drive.

"My wife spoke with the truck driver late last night. Services arrived and both of the occupants were in Katherine Hospital being assessed for internal injuries.

"Timely reminder that things can, and often do, go wrong on the road quite quickly.

"The kids were great. My son was a huge help, assisting with the occupants and cleaning debris off the road while also keeping his sisters safe.

"Please feel free to share this around, and I encourage to do so. Driving with a 'van is more dangerous than some people realise.

"Arriving somewhere later, or missing out on a campsite/attraction/moment, is far better than not arriving at all.

"Stay safe everyone."