A woman in her 30s, who was driving the car, a teenage girl, a young girl and a young boy were all in the blue Volkswagen when it collided with a tree and ended up in a ditch.
The car had suffered significant damage after leaving the main carriageway, travelling approximately 15ft down an embankment and colliding with a tree.
A spokesman for the ambulance service said: “There were four patients, one of whom, a young boy, was trapped in the vehicle. “The fact he was properly fastened into a car seat appears to have helped him avoid more serious injuries in the collision.”
The teenage girl was treated for a suspected broken arm, while another young girl was treated for very minor injuries.
The driver also received treatment for minor injuries. All four were taken to Heartlands Hospital.
It is not known what caused the crash.