A mother, 38, and her 13-year-old son were in critical condition after a semi-trailer ploughed into the back of their motor home. They are now in stable condition, according to a spokeswoman from the Canberra Hospital. 

Police allege a semi-trailer collided with the back of a Mitsubishi mobile home. As a result, the motor home rolled and hit a tree, and the teen boy was thrown from the vehicle.

The 13-year-old boy suffered serious head injuries in the accident.

The family was travelling south on the Hume Highway from their home in Newcastle when the incident occurred at Yarra, near Run O Waters about 11pm. 

The other family members, an 11-year-old boy and a man, were treated by NSW Ambulance Paramedics for injuries.

The driver of the truck, a 43-year-old man, was arrested and taken to Goulburn Hospital for mandatory blood and urine testing. He was then charged at Goulburn police station with two counts of dangerous driving occasioning grievous bodily harm, two counts of cause bodily harm by misconduct of a motor vehicle and negligent driving occasioning grievous bodily harm.

He was granted conditional bail and will appear in Goulburn Local Court on February 17.

A crime scene has been established at the scene and will be examined by forensic officers. 

One southbound land of the Hume Highway was closed following the crash but has now been reopened.

Police are urging anyone with information in relation to this incident to call Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page: https://nsw.crimestoppers.com.au/ 

For further information on traffic disruptions on the Hume Highway, visit www.livetraffic.com