One appliance and crew from Amersham attended.
Two women and one boy, injured, and a third woman, uninjured, were all out of their cars when the firefighters arrived. They provided immediate emergency care before passing them into the care of South Central Ambulance Service.
The firefighters used an environmental pack to mop up spilt vehicle fluids. They also removed vehicle debris from the road.
The road was closed while they worked at the scene.
Thames Valley Police also attended.
