A cyclist has been airlifted to hospital in a critical condition after an accident on the Princes Highway at Dunmore Tuesday morning.
A 45-year-old woman suffered serious head injuries, abrasions to her face and pelvis and was unconscious, a NSW Ambulance spokesman said.
An ambulance helicopter and four road crews were called to the incident which occurred about 8.40am near Shellharbour Road.
Lake Illawarra police duty officer Acting Inspector Peter Northey said a group of cyclists - from a social biking group - were riding in a pack southbound on the highway.
Insp Northey said the cyclists were "riding safely" in the designated bike lane at the time of the accident.
"There was a rock or a piece of debris in the bike lane [and] a female aged about 45 years ... has collided with the debris and has fallen down to the ground," he said.
The woman landed on her face and sustained significant facial injuries and a head injury.
"She was deemed unconscious at the time," he said.
Police and paramedics were quickly on the scene.
The woman has been airlifted from the scene to St George Hospital in a critical condition.
Insp Northey said an initial report suggesting a car was involved was incorrect.
"It was quite simply [a cyclist] riding down the freeway, doing the right thing, [there were] no vehicles involved at all," he said.
The Princes Highway reopened just before 10am after closing earlier to allow the ambulance helicopter to land.