The man, 18, stopped his Ford Falcon on Billbabourie Road at Gwandalan, in southern Lake Macquarie, to deliver a pizza about 7.45pm.  

After he left his vehicle it is believed it rolled down the street before striking him, police said.

Emergency services attended and the treated the man, but he died at the scene.

Tuggerah Lakes Police District arrived and launched an investigation. 

Inquiries are continuing and police will prepare a report for the coroner. 

Anyone with information about this incident is urged to contact Crime Stoppers on 1800 333 000.