The air ambulance has landed at Boongate in Peterborough following a collision.
Emergency services were called to the scene at about 1.30pm today (Tuesday).
There are long delays in the area, and the air ambulance has just landed to treat a man.
A Cambridgeshire police spokesman said the driver had suffered a 'medical episode' at the wheel, and had been taken to Peterborough City Hospital.
The police spokesman said he had no information on the man's condition.
Motorists are advised to avoid the area.