A teenager has been seriously injured in a motorbike accident at Oak Flats.
The 18-year-old man was travelling as a pillion passenger when the bike came unstuck on Lake Entrance Road shortly after 1pm Friday.
He was knocked unconscious and has suffered serious head and facial injuries.
NSW Ambulance paramedics have treated him at the scene and are preparing to transport him to Illawarra Regional Airport at Albion Park, where he is expected to be airlifted to a Sydney hospital.
The rider, a 25-year-old man, has suffered less serious injuries and is being transported by road ambulance to Wollongong Hospital.
Police say he will undergo mandatory testing.
The crash occurred on a bend in the southbound lane, which police have closed to allow crash investigators to work.
Meantime, another rider has been seriously injured in a collision with a truck at Jamberoo.
The rider, believed to be a man aged in his 60s, is being treated on Jamberoo Mountain Road.
The crash has caused him serious bleeding and difficulty breathing.
He has suffered an injury to his hand and lower leg, and a possible broken collarbone.
The crash occurred about 1.55pm, near the intersection with Jerrarra Road
A rescue chopper may be deployed.
Update: A rescue chopper has landed at Jamberoo soccer oval.
The male truck driver is not believed to be injured and is assisting police with their inquiries.
Traffic diversions are in place as officers attached to Lake Illawarra Local Area Command establish a crime scene.