Three people, including a young child, were injured after the car they were travelling in hit a hedgerow while swerving to avoid another vehicle.
Police are appealing for information after the incident at around 6.20pm on Thursday September 1 between Hartwell and Haddenham.
A black Volkswagen Golf was travelling towards Haddenham, when a vehicle travelling in the opposite direction, which police say may have been a Vauxhall people carrier, moved on to the other side of the road causing the driver of the Golf to swerve.
The Golf then left the road and hit a hedgerow.
The driver of the Golf, a 28-year-old man, and two passengers, a 28-year-old woman and a five-year-old boy all sustained whiplash and bruising.
They were treated at Stoke Mandeville hospital and have since been discharged.
Investigating officer PC Andrew Martin said: “If you witnessed the collision and can help us identify the vehicle involved please contact me via the Thames Valley Police enquiry centre on 101.”
Alternatively, contact Crimestoppers anonymously on 0800 555 111.