The A2 Belfast to Bangor carriageway in Co Down is likely to remain closed for several hours this evening following a serious crash.
The road has been closed in both directions at Ballyrobert, near the Ballygilbert Church.
The Air Ambulance was deployed to the scene, police have confirmed.
TrafficWatch NI has said diversions are in place through Craigantlet and Crawfordsburn, and both subject to long delays.
Motorists should seek alternative routes.