A car drove into a ditch on the A23 this lunchtime.
Police were preparing to close both carriageways of the road after the accident just after 1pm.
It is not known if anyone was seriously injured. Firefighters were called to free the occupants of the car.
The crash happened just north of the junction with the A27 at Patcham, Brighton.
One lane was closed northbound while emergency services began to deal with the accident but at 2pm police were considering a complete closure.
Police, firefighters from Brighton and Worthing, two ambulances and the Sussex Police and Ambulance helicopter were called to the scene.
The Highways Agency predicted the road would be clear again by 3pm.
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