The A27 Brighton bypass has been blocked by two accidents and a breakdown on the eastbound side of the road.
Traffic tailbacks have been reported from the Ashcombe roundabout by Kingston village on the edge of Lewes back to the A23 turn-off at Patcham.
One lane has been blocked by a crash near the roundabout while another crash, involving two vehicles near Falmer, has added to the rush-hour delays.
And a car has broken down near Sussex University, compounding the situation.
There were also reports of delays for drivers heading along the A27 to Brighton and Hove from the east.
