Motorists faced long delays on the A1(M) after a collision near the Huntingdon junction shut the southbound carriageway.
The crash happened at 8.30am and involved a four vehicles, one of which was a lorry.
Two lanes initially reopened but long delays remained. The carriageway reopened fully at 12.40pm.
The delays were made worse as extensive roadworks are taking place on the same stretch of road. Queues stretched back to the Norman Cross junction.
The Magpas air ambulance attended the scene. Magpas Doctor Leigh Bissett and Paramedic Dan Cody assessed a woman in her 20s who was trapped inside her vehicle, and who had sustained multiple minor injuries.
She was freed by fire crews and taken to Hinchingbrooke Hospital.
An East of England Ambulance Service spokesman added that there were two patients being treated who have been taken to Hinchingbrooke Hospital for further treatment.
Police said extensive investigative work has now been completed.