A Mandurah woman allegedly drove through a stop sign on Sholl Street, causing another car to flip onto its roof.
A police officer at the scene alleged the white hatchback was travelling north on Sholl Street at about 9.40am, before driving through a stop sign, colliding with the other car travelling west on Hackett Street.
The male driver of the green car, presumed to be in his eighties, was treated at the scene for non-life threatening injuries before being taken to Peel Health Campus.
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The driver of the white hatchback was treated for minor injuries at the scene, and was also taken to Peel Health Campus as a precaution.
Emergency services cleaned a coolant spill on the road.
The policeman said they were still investigating the incident and nobody had been charged.
The Department of Fire of Emergency Services, police and St John Ambulance attended the scene.