Two women have died and a third is in a critical condition in hospital after crash between a car and a bus on one of Western Australia's most notorious stretches of road.

Key points: The accident is the latest in a string of serious crashes on Indian Ocean Drive

The accident is the latest in a string of serious crashes on Indian Ocean Drive Police say it appears the car turned from Pinnacles Drive in front of the bus

Police say it appears the car turned from Pinnacles Drive in front of the bus Millions have been invested in safety upgrades to the road in the past two years

The vehicles collided on Indian Ocean Drive in Nambung, at the turn-off to the world-famous Pinnacles rock formations about 190 kilometres north of Perth, shortly before 2:00pm yesterday.

Police said it appeared the Nissan SUV, with three Chinese tourists onboard, turned from Pinnacles Drive onto Indian Ocean Drive, colliding with the Transwa bus which was carrying 34 passengers.

"The collision caused the Nissan to roll, coming to rest on its roof," a police spokesman said.

It is not yet known what caused the car and bus to collide near the turn-off at the Pinnacles. ( ABC News )

Crews from Police, St John Ambulance and the Department of Fire and Emergency Services were called to the accident.

One of the Chinese woman who was travelling in the car died at the scene, while the other two were flown to Royal Perth Hospital by the RAC rescue helicopter.

One of those women has since died.

Anyone who saw the crash or the car or bus beforehand has been urged to come forward. ( ABC News )

The third woman who was in the car, aged 23, is in a critical but stable condition in hospital.

St John Ambulance officers treated some of the bus passengers at the scene for minor injuries.

'It is a bad intersection': police

WA Police Superintendent Domenic Wood said it was a tragic and horrible crash.

"The driver and front seat passenger were the ones that I've been advised sadly passed away," he told ABC Radio Perth.

"It is a bad intersection … and of course if you're impacted from the side it's always going to be a potentially serious or fatal crash, especially when you're colliding with such a heavy vehicle.

"[The deceased] are Chinese nationals so it's very important for us to now take care of their family next of kin and to make sure that all those appropriate notifications are taking place."

The force of the collision caused the SUV to roll before coming to rest on its roof near the bus. ( ABC News )

Superintendent Wood said a number of bus passengers were treated for shock.

Police said inquiries into the crash were continuing.

They have appealed for anyone who witnessed the crash or has dashcam footage, or who saw either the SUV or the bus before the accident, to contact Crime Stoppers.



Dozens of serious crashes plague highway

Indian Ocean Drive was built to provide a scenic coastal road between Perth and WA's Mid West region, while also taking tourist traffic off the busy freight route of Brand Highway.

There have been string of serious crashes on Indian Ocean Drive since it opened in 2010. ( ABC News: Emily Piesse )

It is popular particularly with international tourists as a route to visit the Pinnacles natural rock formations.

But it has been the scene of dozens of serious crashes since it opened in 2010, a number of which have been fatal.

Three people, including a six-year-old boy, were killed in a head-on collision south of Lancelin in August 2017.

In December last year, another three people including two Chinese tourists died in an accident involving a minibus and two other vehicles.

Sorry, this video has expired Three dead in Indian Ocean Drive crash

The WA Government initiated a safety review of the road in 2017 before those crashes, resulting in $7 million being set aside for improvements.

Part of that funding went towards building four additional passing lanes between Lancelin and the town of Seabird.

Construction started on those lanes in April last year.

The speed limit on Indian Ocean Drive was also lowered from 110 kilometres per hour to 100kph following the review.

Section of road already upgraded: Minister

WA Transport Minister Rita Saffioti said the section of road where the crash happened was upgraded "about 10 years ago".

"We've spent $15 million and we're spending another $24 million [on Indian Ocean Drive] so we've got significant upgrades," she said.

Rita Saffioti says the Government is trying to teach tourists about driving on WA roads. ( ABC News: Eliza Laschon )

"But in relation to where this accident happened, we understand this part of the road had been upgraded.

"It is an awful, tragic accident and I feel for the families involved and the passengers and the driver of the bus too … [the driver] of course did all they could to stop any further injury to the passengers."

The Government last year launched a campaign to market Western Australia as the "Road Trip State", and Ms Saffioti said they were trying to teach tourists how to stay safe when driving around WA.

"We're continually trying to improve education for international visitors using our roads and that's something that's being worked on," she said.

"I'll talk to the Minister for Tourism about the whole issue today but really this is just a tragic accident … my thoughts go out to the families."

Regional Development Minister Alannah MacTiernan said regional tourism was seeing a shift to more people self-driving.

"This is something that really is attracting tourists from overseas into regional areas and I guess we may need to perhaps give a little bit more education to our self driving tourists about how to keep safe on these roads," Ms MacTiernan said.

"Many would probably come from big cities where they may never have driven these sorts of distances …"