Two children travelling in the station wagon were injured.
Sergeant Bruce Terry, of Cromwell, said the station wagon collided with the rear of the bus as it slowed for a car turning right into a rest stop near Old Faithfull Rd about 1.20pm.
A St John spokesman said the two children were treated at the scene for cuts and abrasions.
Sgt Terry said there were no passengers on the bus. The family were ``local'', but he declined to say exactly where they were from.
Drivers needed to take extra care at this time of year due to the high volume of holiday traffic, he said.