Firefighters and police are currently working to free a woman trapped in her car on the A5 in Northamptonshire after her vehicle left the road.
The BMW car is currently in a ditch on the major route close to Towcester Racecourse, having crashed around 4.30pm, Northamptonshire Police says.
Tailbacks are being reported in both directions between Tove roundabout and the Brackley Road junction.
Motorists are also being warned that a race meeting at Towcester Racecourse is due to finish at 5.30pm, which is likely to increase congestion further.
Those attending the racecourse are being advised to leave via Stoke Bruerne Road.