Police have warned motorists that the A29 will be closed southbound from Broadbridge Heath and northbound from just north of Billingshurst from 4.30pm today (Monday December 3).
Heavy lifting equipment is being brought in to clear a broken down HGV lorry and the operation is likely to take several hours.
Police are advising drivers to avoid the A29 north of Billingshurst following the break down of the lorry this afternoon.
Emergency services were called to the incident at around 12pm following reports that a trailer had broken away from the lorry on the roundabout near the Audi garage.
There are no injuries.
A crane has been organised to assist with the breakdown and this may cause the A29 to be closed for several hours.
Drivers are advised to find an alternative route where possible.