Paramedics took two adults, three toddlers and a teenager to John Hunter Hospital after a caravan rolled on the New England Highway in Liddell, south of Muswellbrook, on Wednesday afternoon.
Singleton police said a car towing a caravan was travelling towards Muswellbrook when the caravan rolled on a bridge over Bayswater Creek, causing the car to crash into the bridge's railing.
"The caravan rolled down the road. It detached from the car and rolled. It was a very large caravan," Sargent Rod Cillero of Singleton police said.
"The car hit the railing on the side of the road," he said.
Sargent Cillero said the six passengers in the car were taken to John Hunter Hospital due to the severity of the incident.
"It was basically for check ups. They were all okay," he said.
Sargent Cillero said a family of six were in the car: a set of one-year-old twins, a boy and a girl, a three-year-old boy, a 16-year-old girl, their mother and grandmother.
NSW Ambulance Inspector Joel de'Zuna said all passengers had escaped from the car by the time paramedics arrived.
"Fortunately, they mostly had minor injuries, with abrasions and bruising," Mr de'Zuna said.
The teenage girl was reported to have lacerations to the head and the driver a possible shoulder injury.
All six passengers were in a stable condition.
The New England Highway had been closed in both directions at Lemington Road. The highway reopened at 5.15pm.
Police are investigating the incident.