A Mount Druitt man was travelling south with two passengers, a woman aged in her 30s and an 11 year old boy, when it is believed he had a medical fit and lost control of his white Mitsubishi ASX at about 10.55am near the Figtree exit ramp.

The driver is believed to have hit the guardrail from left lane and then rolled the car a number of times before it has come to a stop on the passenger side.

Wollongong District Police Inspector Mark Walker said it was fortunate no other cars were involved.

"The male has sustained head and facial injuries in the crash," he said. "When NSW Ambulance paramedics were treating him at the scene, he was in and out of consciousness. The driver was airlifted to St George Hospital for further treatment.

"The young boy and the female passenger have sustained minor injuries only. They were taken to Wollongong Hospital by road ambulance.

"In the crash, the dog has been ejected from the car and unfortunately it has been fatally injured."

The dog was believed to be a black poodle cross or a similar breed.

Fire and Rescue NSW crews also attended the scene to free the driver who was trapped by his seatbelt.

"Due to his physical condition at the time, he couldn't get out," Insp Walker said.

"Fire and Rescue NSW cut the roof off the car to get the male out."

The woman and child were able to free themselves.

Insp Walker said investigations into the cause of the crash, which caused significant traffic delays, were ongoing.

"We are not exactly sure how this crash has occurred," he said. "It is possible it has been the result of a medical episode but we are keeping an open mind.

"Police continue to investigate and we will get to the end of it in a short time."

Anyone who witnessed or has dash cam footage of the crash is urged to come forward to Wollongong District Police or Crime Stoppers, 1800 333 000.