The bottom of Bulli Pass was closed on Saturday morning after a three-car accident.
Police blocked that section of the pass on the Princes Highway southbound about 11am.
Four people were involved in the accident.
A 20-year-old woman was taken to Wollongong Hospital with a possible head injury.
She was unconscious at the scene and was in a serious but stable condition.
Emergency services remained on the scene and motorists were advised to use Mt Ousley Rd.