Two killed, two critically injured in Western Australian highway crash

Two people have been killed and two others are in a critical condition after a serious crash in Western Australia's Gascoyne region.

Emergency services were called to the scene of a two-vehicle collision south of the Overlander Roadhouse near Shark Bay at about 11:30am.

"Two vehicles, one of which was towing a caravan, collided, causing the caravan to roll," a WA Police spokesperson said.

"Two people have died as a result of the crash.

"A 12-year-old passenger sustained critical injuries and is being airlifted to Perth for medical treatment."

The child and surviving adult were receiving treatment for critical injuries from two doctors and a nurse aboard an emergency jet, according to RFDS.

They were taken from the crash site to Shark Bay Airport, about 830km north of Perth, for the evacuation.

The child will be transferred to Perth Children's Hospital and the adult to Royal Perth Hospital upon arrival at Jandakot Airport.

The North West Coastal Highway has been closed by WA Police and motorists are being asked to avoid the area.

Officers from the Major Crash Investigation Section are investigating the circumstances surrounding the crash.

'A lot of confusion'

Dozens of cars, caravans, and road trains have stopped at the Overlander Roadhouse, with the arterial highway currently at its busiest for the region's winter tourist period.

James Capener was driving from the Pilbara to Perth with his family when he was turned around by police.

"There's still a lot of people arriving now with boats and trailers and more trucks," he told the ABC.

Mr Capener said the nearest caravan park was already fully booked and most vehicles were pulling over along the side of the road.

"There is a lot of confusion … it went from that five hour [delay] to that 24 hours really quick," he said.

Mr Capener said his thoughts were with the victims.

"We were about 300 metres away from it," he said.

"And you think, if you were half an hour earlier or 20 minutes, or you didn't stop at the roadhouse before, you could be involved in that.

"You do feel for the people that are involved in the families, and our prayers go out to them."

According to the Road Safety Commission, there have been 131 fatalities on WA roads, compared to 123 this time last year.