thumb|268px|The route of the A1 in red from [[Belfast city centre (County Antrim) to the border at Carrickcarnan (County Louth)]]
The A1 is a major route in Northern Ireland. It runs from Belfast via Lisburn and Banbridge to the border with the Republic of Ireland south of Newry, from where the road continues to Dublin, becoming the N1 road and M1 motorway. Between Sprucefield and Carrickcarnan the road forms part of the European route E01.
Recent developments
The A1 is a dual carriageway south from Sprucefield but some junctions remain relatively low specification as they necessitate right-turning movements across the central reservation. The busier junctions have been improved by the provision of bridges or underpasses.
A flyover was constructed at the busy Rathfriland Road junction in Banbridge and an underpass at the very dangerous Hillsborough road junction in Dromore was completed in June 2005.
Improved junctions at Banbridge and Hillsborough opened in September 2009,