A man's head is believed to have gone through a car windscreen in a West Wollongong crash at 1.15pm on Monday.
Paramedics responded to the two-car crash on the M1 Princes Motorway at the Robsons Road on-ramp following reports of a 35-year-old man had suffered head injuries.
The man has been taken to hospital.
The on-ramp is now open after being closed earlier.
A person at the scene said it appeared a white van has crashed into the back of a silver sedan.
Northbound traffic is being affected, and motorists have been advised to exercise caution.