There are long delays on the A1(M) southbound after a collision near Peterborough.
The collision happened at about 8.50am between junction 16 and 17.
A Cambridgeshire police spokesman said one car ended up in the central reservation, while the other ended in a ditch on the side of the road.
The police spokesman said both drivers were being assessed by the ambulance service.
The cars are currently being recovered, and delays are expected while emergency services continue to work at the scene.