The previous route continued south through Kilgowan, the intersection with the N78 to Athy, Ballitore, the R747, Timolin, Moone and through Castledermot in County Kildare.
This then joins with another 18.5 km (11.5 mi) stretch of motorway, opened 29 May 2008 bypassing Carlow, meeting the R448 at a junction near Powerstown.
While these plans were later altered to High Quality Dual Carriageway, in July 2008 the road was reclassified as a motorway once more.
An EIS was published and a CPO issued in February 2005 for the 64 km (40 mi) southern section of the upgraded route, from Powerstown to Waterford.
The southern section of route differs more from the former N9 alignment than most of the national road upgrade projects in recent years.
As part of the project, the new M9 joins at a roundabout just off the Granagh Interchange which then allows access to Waterford City or the bypass to Rosslare/Cork.