Emergency services were called to the Newell Highway following reports a 23-year-old woman had been critically injured after falling from a 4WD about 5.10pm.

The Dubbo woman was treated at the scene by passing motorists until paramedics arrived and she was taken to Peak Hill Hospital, where she died.

Police from Lachlan Local Area Command were alerted and initiated an investigation.

The driver of the 4WD, a 53-year-old man from the Central Coast, has undergone mandatory testing and is assisting investigators with their inquiries.

A report will be prepared for the information of the coroner.