The incident involved two cars and a van and happened near Horns Cross at around 8 am this morning [25 January].
The driver of one of the vehicles has been seriously injured and the other two drivers are not believed to have sustained any injuries.
The road remains closed between Acre Road and the Hoops Inn junction and is expected to be shut for some time. Drivers are advised to avoid the area for the time being.
Any witnesses to the collision are asked to contact police on firstname.lastname@example.org or call 101 quoting log 83 of 25 January.