Police are seeking information about a crash in Karnup yesterday that left a 25-year-old woman with serious injuries.
The Meadow Springs woman was a passenger in a silver Suzuki Swift that was being driven south along the Kwinana Freeway about 4.50am.
A police spokesman said the driver lost control of the car after taking the Paganoni Road exit.
"It appears the vehicle left the road and rolled down the embankment back towards the south bound lanes of the freeway," he said.
The woman was thrown from the car and was found pinned under the front of the vehicle.
A passerby helped the driver lift the car off the passenger.
She was taken to Royal Perth Hospital by the RAC Rescue helicopter.
Anyone with information is asked to call Crime Stoppers on 1800 333 000.