A 29-year-old Ascot Vale woman has been flown to a Melbourne hospital in a critical condition after being "vacuum sealed" in her car after a collision with a gum tree near Hamilton.
Hamilton police Sergeant Mark Phillips said the woman in a Ford Fiesta went through a bend too quickly on the Hamilton-Dartmoor Road about 9.30am Tuesday, lost control and crashed into a gum tree.
The side of her vehicle struck the tree and flipped up the truck, trapping the woman in the driver's seat as the roof caved in around her.
"It's like she was vacuum sealed. It was uncanny," Sergeant Phillips said.
"The accident happened about 500 metres west of the city boundary.
"She's gone through the bend too quick and the other possibility is that she was distracted by something in her car."
The experienced police officer said the woman was conscious and breathing.
"She was talking to emergency service workers," he said.
"She was trapped for between 30 and 45 minutes while she was cut from the vehicle. It was a pretty good effort.
"Her injuries were not obvious and she was taken to the Hamilton Base Hospital for assessment and treatment."
Sergeant Phillips said the woman's condition deteriorated and she was downgraded to a critical condition due to crush internal injuries before being airlifted to Melbourne hospital.
"She looked like she could have walked away from the accident, but deteriorated, which sometimes happens with those sort of injuries," he said.
"The message to all drivers is slow down and concentrate. Everyone simply has to drive to the road conditions.
"This woman was from Ascot Vale and more than likely unfamiliar with that road.
"She was going too fast around the bend, lost control and there's also the possibility of other distractions in her car.
"Drivers need to concentrate on the road ahead and not what's going on in their vehicles."
It was the fifth serious accident in the south-west during the past 12 days, including fatalities at Woorndoo, Allansford and Noorat.
A Melbourne barrister involved in a cycling accident with a four-wheel-drive on Saturday night at Dennington is still in a life-threatening condition at The Alfred hospital.
He's in an induced coma in the hospital's intensive care unit and his long-term prognosis is not clear.
Have you signed up to The Standard's daily newsletter and breaking news emails? You can register below and make sure you are up to date with everything that's happening in the south-west.