Police are advising motorists that the A1 has been closed in both directions following a single vehicle road traffic collision at Sheepbridge, between Banbridge and Newry.
The male driver of the car has been taken to hospital where his condition is described as “serious”.
Police are investigating the circumstances of the collision.
“Diversions are in place and motorists are advised to avoid the area and seek alternative routes for their journey if possible,” a PSNI spokesperson said.
There are no further details at this time.