The dual carriageway continues north, intersecting with the N69 road, before crossing under the River Shannon using the Limerick Tunnel, this section of the route forms phase II of the Limerick Southern Ring Road and is tolled between junctions 2-4.

North of the River Shannon the N18 continues as dual-carriageway bypassing Cratloe, Sixmilebridge and Bunratty.

The road passed alongside Bunratty Castle before the completion of the neighbouring dual-carriageway section in the late 1980s/early 1990s.

The N18 continues north of the N19 junction where motorway regulations are enforced and the N18 route is designated as the M18 bypassing the towns of Newmarket-on-Fergus, Ennis and Gort.

DirectRoute (Tuam) Ltd., a consortium consisting of Marguerite Fund, InfraRed Capital Partners, Sisk Group, Lagan Construction Group, Roadbridge and Strabag[3] began construction of the scheme in 2015 and was officially opened on 27 September 2017.

The remaining single carriageway sections from Gort to Claregalway have been upgraded to motorway standard and were officially opened on 27 September 2017.