Teen girl dead after NSW road crash

A teenage girl is dead after being struck while walking on a road south of Sydney.

The girl and a boy, both aged 16, got out of a vehicle on Old Hume Highway at Mittagong about 10.20pm on Friday, police say.

Both were then struck by a second vehicle.

The girl suffered serious head injuries and was flown to Liverpool Hospital, where she died on Saturday.

The boy remains in a stable condition at the same hospital after injuring his legs.

The driver of the second vehicle, a man aged 42, was released from custody after undergoing mandatory tests.

Local police are continuing to investigate the crash.