The R639 road is one of Ireland'sregional roads. Once designated the N8national primary road, it was reclassified in stages as the R639 following the progressive opening of sections of the M8 motorway, which rendered the single carriageway N8 redundant as a national primary road. By-passed sections of the old N8 were generally reclassified as R639 as soon as a new section of M8 opened, thereby increasing the length of the R639. With the completion of the M8 on 28 May 2010, the R639 now stretches from Durrow, County Laois to Cork, running through counties Laois, Kilkenny, Tipperary, Limerick and Cork.
In the 17th, 18th and early to mid-19th centuries - and probably earlier still - horse-drawn Dublin-Cork traffic travelled via Kilcullen, Carlow, Kilkenny, Clonmel, Ardfinnan, Clogheen, Ballyporeen, Kilworth, Fermoy and Rathcormac. Much of the R639/N8 route was built to connect the midlands to southern Tipperary and north County Cork as part of the Irish turnpikeroad-building drive of the mid-18th century. However, some sections are considerably older, such as the segment between Cork and Fermoy, and that between Cashel and Cahir; the construction of these particular stretches cannot as yet be dated, though they were in place prior to 1714. The R639/N8 between Fermoy and Cahir via Mitchelstown was built sometime after 1811, while the R639 between Cashel and Urlingford was built around 1739. At the same time, the route from Urlingford to Maryboro was substantially improved. In 1782 an unnamed English tourist in Ireland, known to historians as "X.Z.", gave a brief description of the route between Cashel and Urlingford: "From Cashel we rode fifteen miles of a bad road, through a bleak country to Urlingford, when we enter Leinster province. The country now becomes more populous, better improved, and the roads much more agreeable for travelling."
20th and 21st centuries
Some time after 1811 the gaps in the R639 between Fermoy and Cahir were filled, but the traditional Cork to Dublin route, known for much of the 20th century as the T6, continued to run from Cork to Cahir, and from there to Dublin via Clonmel, Kilkenny and Carlow. The R639/N8 corridor did not become the official Dublin to Cork road until 1974, though several Esso road atlases considered it to be the preferred route for motorists travelling between the two cities from at least the early 1960s. From this time until the gradual opening of the various M8 motorway segments beginning with the Fermoy Bypass in 2006, the route was known as the "N8". The N8 was improved at various times during the 1970s through to the early years of the 21st century. One of the first improvements entailed a realignment of the road so that it bypassed the village of Glanmire for 6 km to the east. This dual carriageway bypass, referred to in official documentation as the "Glanmire Bypass", opened in April 1992 after a construction period of almost 7 years. When this happened, the former T6/N8 through Glanmire was renumbered, for the first time, as the "R639". The next major incident in the modern history of the R639 occurred in 1991, when a new 4 km single-carriageway bypass to the south-west of Cahir in County Tipperary opened to traffic. This bypass became a part of the N8 for the next 18 years. With the completion of the M8 motorway through South Tipperary in July 2008 however, the 1991 N8 Cahir Bypass was renumbered as part of the N24 - while simultaneously becoming the R639. Other improvement projects carried out on the road during the 1970s, 80s and 90s involved periodic widening and resurfacing. In spring 2001, attention was turned to Watergrasshill in County Cork. For many years regarded as a serious bottleneck on the N8, a wide median 7 km dual carriageway bypass was constructed and opened to traffic in September 2003 as the N8, with the former road through Watergrasshill becoming the R639. In 2004 the N8 through Cashel in County Tipperary was realigned with a narrow-median dual carriageway bypass to the east of that town. Again, the former N8 through Cashel was redesignated a regional road, and renumbered the R639. In October 2007 the section of N8 between Cashel and Cahir was bypassed by an early-opening segment of the M8 motorway, and became the most recent addition to the R639 route. This, in turn, was followed in July 2008 by the section between Cahir and Kilbehenny; on 8 December 2008 by the length of road from Cashel to 2 km south of Cullahill in County Laois; on 25 May 2009, by the section between Mitchelstown and Fermoy; and on 28 May 2010 by the length between Durrow and Cullahill.
