The journey time from Dublin and Belfast will be cut to only two hours with tomorrow's opening of a new dual carriageway between Dundalk and Newry.
The ribbon will be cut on the 14 kilometre-long A1/N1 dual carriageway by Minister for Foreign Affairs Dermot Ahern and Northern Ireland Regional Development Minister Conor Murphy.
The opening of the route is the result of a high level cross-Border partnership between the National Roads Authority, Louth County Council and the Northern Ireland Roads Service.
The €154 million project will link the A1 at Cloghoge in Co Armagh to the N1 at Dundalk.
Some 4.6km of the scheme is north of the Border and the remaining 9.4km is in the Republic.
The section of the scheme south of the Border has a designated speed limit of 120km.
The Irish and British Governments funded the project with assistance by the European Union from the Trans-European Transport Networks Budget.