About 6:30pm a woman was driving her Toyota Landcruiser 4WD west on the Mid Western Highway with her two children onboard when she pulled over to the side of the road, police said in a statement.

As she was slowing down her 16-year-old son fell out of the vehicle and landed heavily on the road.

Paramedics attended the scene and the boy was taken to Bathurst Hospital before being airlifted to The Children’s Hospital at Westmead where he underwent surgery and remains in a critical condition.

His mother, aged 49, was not injured during the incident but underwent mandatory blood and urine tests at Bathurst Hospital.

Police established a crime scene on the southern side of the highway, which was examined by specialist forensic officers.

Detectives from Chifley Local Area Command are continuing their investigations into the incident and have seized the 4WD for examination.