One appliance and crew from Newport Pagnell, one from West Ashland and one from Buckingham attended, along with an officer.
One man was out of his vehicle, uninjured, before they arrived. Two women were out of their vehicles, suffering minor injuries, before they arrived.
The firefighters used hydraulic rescue equipment to release a third woman, injured, who was passed into the care of South Central Ambulance Service.
The firefighters assisted South Central Ambulance Service by providing immediate emergency care and oxygen therapy to those suffering injuries.
Thames Valley Police also attended the incident.