Four drivers were injured after a lorry hit another vehicle and then shunted two other cars on the A45 near Stanwick.
The collision happened on the westbound carriageway at about 8.35am yesterday (Thursday).
A white DAF lorry, driven by a 42-year-old man from Norfolk, was approaching the Chowns Mill roundabout when it went into the back of a blue Volvo lorry, which was then pushed forward into two cars.
The DAF driver was taken to Northampton General Hospital and the other drivers were treated for minor injuries.
Witnesses to the collision or anyone with information is asked to call Northamptonshire Police on 101.