A teenage girl is dead and her brother fighting for life in a Sydney hospital after a car hit a tree in Port Kembla on Monday.

Georja Balfour, 15 from Port Kembla, was the front-seat passenger in a Holden Commodore that crashed on a sweeping bend of Flinders Street, where it becomes Old Port Road, about 12.45am.

James Balfour, Georja's 19-year-old brother who was driving, sustained life-threatening injuries and was airlifted to St George Hospital by the NSW Ambulance Rescue helicopter in a critical condition. 

A 17-year-old boy from Primbee, who was in the back seat, was treated for minor injuries and airlifted to the same hospital in a serious condition. 

Initial police investigations suggest speed may have been a factor in the crash.

‘‘They were negotiating a sweeping right-hand bend, they’ve lost control of the vehicle, slid across the roadway ... mounted the footpath and impacted heavily with a large tree,’’ Detective Inspector Glen Broadhead, from Lake Illawarra police, said.

‘‘As a result of the impact, the tree has intruded significantly into the occupant [area] of the car. 

‘‘We’re looking at speed being a significant factor for the car losing control.’’

The teenager’s death - the 10th in three horror days on NSW roads, has prompted a warning from police for drivers to accept greater responsibility for their actions.

NSW Police Traffic and Highway Patrol Command Assistant Commissioner John Hartley said the deaths, which included two in the Illawarra and Shoalhaven, were the result of nine fatal crashes.

A 94-year-old Berry woman, who was hit by a car while crossing the northbound lanes of the Princes Highway in Nowra on Friday, succumbed to her injuries in hospital on Saturday morning.

‘‘Speed, fatigue, drink or drug driving, failing to use controlled crossing areas, being unlicensed, not wearing helmets, using defective vehicles, are all key elements in these crashes, which are costing lives,’’ Assistant Commissioner Hartley said. 

‘‘There are 10 families this morning [Monday] that are suffering the pain of losing a loved one on our roads. When you consider friends, workmates, emergency services and hospital workers, the number of those directly and indirectly affected by road trauma in just three days is significant.’’

Do you know more about this accident? Contact cos@illawarramercury.com.au