A CareFlight trauma doctor is assisting ambulance paramedics treat a man trapped in his car at Parramatta.
The head-on crash happened shortly after 1pm on Gasworks Bridge and has blocked Macarthur Street.
Police, Fire-Rescue, Ambulance and CareFlight were called to the scene.
CareFlight landed on the grounds of the nearby Macarthur Girls High School to allow the crew doctor to team with paramedics.
On release and stabilisation the man is expected to be taken under continuing treatment by the CareFlight doctor and ambulance paramedics, in a road ambulance, to Westmead Hospital.
More to come.