The N18 is an important route carrying traffic between Galway and Limerick, the two main population centres of the West and Mid-West of Ireland. The road forms part of the Atlantic Corridor project.
The N18 was originally a single-carriageway road between the two cities, but saw substantial investment in the early 2000s and a gradual upgrade of the route. Those sections which have been improved to motorway standard are now classified as the M18.
The N18 near Shannon Airport. The road ahead is now the M18 and this part of the road is also scheduled to be improved to motorway standard.
Today's all-purpose part of the route starts on the Limerick Southern Bypass at a grade separated junction with the M7 and M20, heading underneath the River Shannon and providing access to the north of Limerick via a spur, before crossing into County Clare. It remains dualled, albeit with a handful of at grade junctions, up to the N19, which provides access to Shannon. From here the road is motorway standard to the M6.
The original road was part of the T11, which the N18 took over the Limerick - Galway section of when National roads were first designated. It started in the centre of Limerick, crossed the Shannon on the Sarsfield Bridge and followed the R587 and R445. From here to the N19, it followed roughly the current route, which has been improved online, then took the R458 through Ennis to Kilcolgan, then the northern part of the N67 towards Oranmore. The road was later extended after it took over the route of the N64 when it was upgraded to National Primary status.
The first upgrade to the road was the Limerick to Shannon Dual Carriageway, providing a suitable motor link to Shannon Airport, which opened in 1975. It was a typical online upgrade of that era, with at-grade turns and properties facing the road. The replacement route beyond the N19 junction was completed in stages between 2002 and 2007, and subsequently upgraded to motorway. The Limerick Southern Bypass phase II opened on 27 July 2010, taking the N18 away from the city centre and bypassing it via the Limerick Tunnel. Shortly afterwards, the M18 was extended as far as Gort. This left the northern section towards Oranmore (and hence Galway) as the N18, which was by then a significantly congested single-carriageway route with two level crossings over the Limerick - Athenry railway. This was resolved when the north section of the M18 to the M6 opened in September 2017.
Irish Statute Book
Roads Act 2007 (Declaration of Motorways) Order 2009 - This instrument converts the following sections of the N18 to motorway:Shannon to Ennis (known as Ballycasey to Dromoland), Ennis Bypass (also known as N18 Dromoland to Crusheen), Gort to Crusheen, Oranmore to Gort