A crash involving a skip hire lorry has reduced the Dronfield bypass to one lane in each direction after the driver was taken ill at the wheel and hit the central reservation.
The incident happened shortly after midday between the Bowshaw roundabout and Sheepbridge industrial estate and has destroyed around 80m of the barrier.
The driver has since been taken to hospital.
Police say the restrictions are likely to remain in place for some time as recovery teams remove the lorry and repair the damaged barrier.
Those intending to use the road this afternoon and evening are advised to find alternative routes if possible.