The A27 has been closed for the past eight hours following a serious collision between the A26 (Southerham roundabout, Lewes) and the A26 Beddingham roundabout.
Emergency services have been at the scene since around 8am, investigating and clearing the scene.
The road has been closed in both directions while they responded to the incident.
Sussex Police have advised motorists to find alternative routes.
Officers have thanked the public for their patience.
More to follow.