Emergency services were called to the intersection of Stewart Street and Durham Street in Bathurst at about 8.30pm overnight.
They found a man, believed to be aged in his late 30s to early 40s, with serious head injuries.
He was treated at the scene before he was airlifted to hospital in a critical condition.
Police believe the man fell from the front passenger side of a white ute, which failed to stop and continued travelling west along Stewart Street.
Stewart and Durham Street both form part of the Great Western Highway.
Specialist police are on the way to the scene.
Traffic diversions are expected to remain in place for a considerable amount of time.