ALTUS Traffic controller Mark Butler was resealing parts of the Warrego Hwy about 5km west of Dalby when he witnessed a car veer off the road and become airborne.
"I heard a gravelly (sic) noise and turned around to see the car exit the road… and the car went down on an angle into the drain itself and hit the flat part of the drain," he said.
"It became airborne, came down again and landed on the passenger nose of vehicle and rolled three times."
Mr Butler worked with a driver who had pulled over to free the 25-year-old female driver on Monday just before 11am.
"She was trying to get out from under the steering wheel and was trying to stand up," he said.
"I worked with a guy who pulled up in a truck.
"We used a star picket to pry the windscreen off the vehicle and then proceeded to get her out of the vehicle and laid her down in the grass."
Dalby Police Sergeant David Tierney said the woman remained conscious and was taken to Dalby Hospital in a stable condition.
"She's very lucky. She has lower back pain," he said.
Mr Butler said Monday's crash was the fourth he had witnessed over the past 12 months.
"At least this one wasn't a fatal," he said.
Sgt Tierney said the woman had been travelling from Roma to Toowoomba.
"At this stage, whether the crash was caused by inattention or speed, we don't know."
The Warrego Hwy remained open to traffic on Monday.
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