There have been routes and trackways in Ireland connecting settlements and facilitating trade since ancient times and the country now has an extensive network of public roads connecting all parts of the island.
Early history The first routes in Ireland were prehistoric trackways, some of which were later developed into roads suited for wheeled vehicles. Many of Ireland's minor roads "may well have had their origin in pre-existing paths and trackways aligned in direct response to the physical environment". Traces of these evolved roads which developed over very long periods, frequently from tracks of the prehistoric period, are still evident. The routes of such roads usually followed the natural landscape, following the tops of ridges and crossing rivers and streams at fording points.
There is almost no evidence that large roads were constructed in Ireland during the Stone Age. However, a very large oval henge enclosure, thought to date from 2500 BC (the Neolithic period) may possibly have had an ancient roadway associated with it. The henge was discovered at the Hill of Tara archaeological complex in geophysical surveys carried out between 1999 and 2001. It is unlikely that any roadway from this period would have been used as a transport route. Excavations carried out at Edercloon, County Longford in advance of road construction discovered a dense "network of wooden trackways and platforms, which were constructed from the Neolithic ( 4000- 2200BC) to the early medieval period ( AD 400–790)."
Wheeled vehicles with solid wooden disc-wheels were introduced into northern Europe around 2000 BC. An example of a disc-wheel, from the Netherlands, was found next to a wooden trackway: "it appears from this evidence that the introduction of disc-wheeled carts into…northern Europe required the invention of roadbuilding about 2000 B.C." An Early Bronze Age trackway, from shortly after 2000 BC, was found at Ballykillen Bog, near Edenderry, County Offaly in the 19th century. It may have been designed to carry disc-wheeled vehicles. A section of a wooden trackway, three feet (approx. 1 metre) wide and 1 km long was surveyed at Corlona Bog in County Leitrim in the 1950s. The trackway was dated by radiocarbon dating to approximately 1500 BC but its narrow width makes it unlikely that it was used by wheeled vehicles. Similar wooden trackways and roads are known from all over Ireland from the Late Bronze Age. One example from Ballyalbanagh, County Antrim was wide and made from oak beams and planks: "its width suggests provision for cart or wagon transport."
Archaeological excavations have found some roads built with stone in the Irish Iron Age. Ireland was never part of the Roman Empire and, therefore, Roman roads were not built in Ireland. However, a 22-kilometre long Iron Age road with a stone surface, part of a defensive complex, has been excavated in Munster: this, along with similar excavations, demonstrates that "Roman methods of road construction were known in Ireland." Generally, most surfaced tracks from this period were made with wood and were designed to facilitate travel through (or to) bogs. Togher () roads, a type of causeway built through bogs, were found in many areas of the country.
Although law-tracts in Early Medieval Ireland described several different types of road, and Irish annals referred to a network of major highways, there is no evidence to suggest that Ireland ever had a network of roads as well developed as those found in the Roman Empire or other ancient societies. The road network remained underdeveloped throughout the Late Medieval and much of the Early Modern periods: it was not until the 18th century that an extensive system of roads suitable for long-distance travel was developed. Newly built roads were relatively wide and straight. Many still form the backbone of the current major roads network. The development of roads continued throughout the early 19th century until the arrival of the railways which became the dominant form of land transport from the 1840s–1850s onwards. The development of the internal combustion engine and of motorised vehicles led to increases in traffic on roads, which were developed and improved as a result. Ireland's roads have continued to develop and improve up to the present day. Various development programmes have successively increased the number of motorways and dual carriageways within the national roads network while other roads have had their surfaces and signposting improved.
Roads in medieval Ireland Five great roads
According to an entry in the Annals of the Four Masters for AD 123, there were five principal highways () leading to Tara () in Early Medieval Ireland. The entry in the Annals claims that these routes were 'discovered' at the birth of Conn of the Hundred Battles: The night of Conn's birth were discovered five principal roads leading to Teamhair, which were never observed till then. These are their names: Slighe Asail, Slighe Midhluachra, Slighe Cualann, Slighe Mhór, Slighe Dala. Slighe Mhór is that called Eiscir Riada, i.e. the division line of Ireland into two parts, between Conn and Eoghan Mór.
In reality, "the ancient road system (such as it was – there cannot have been a developed national system) fanned out not from Tara but from Dublin.".
The Slighe Assail went due west towards Lough Owel in County Westmeath, then to Cruachain. The Slighe Midluachra went towards Slane, through the Moyry Pass north of Dundalk, round the base of Slieve Fuaid, near Newtownhamilton in County Armagh, to Emain Macha, ending at Dunseverick on the north coast of County Antrim. The Slighe Cualann ran south-east through Dublin, crossing the River Liffey via a hurdle-bridge, then went south "through the old district of Cualann, which it first entered a little north of Dublin, and from which it took its name". The Slighe Dala ran towards and through Ossory in County Kilkenny. The Slighe Mhór ('Great Highway') joined the Esker Riada near Clonard, County Meath. It then, more-or-less, followed the Esker Riada to County Galway.
Unlike Roman roads, these routes were not clearly physically defined:
It is important to remember that unlike, for example, Roman roads, these medieval routes were not essentially physical entities—thin strips of land with physical boundaries; rather they were rights of way, sometimes with legal and traditional status. Routes tended to follow the line of least resistance, twisting and turning to avoid poorly drained areas and land that was easily overlooked. Where there was a hill to climb or a difficult area to pass through, multiple tracks would develop, the traveller taking the easiest route. Routes may also have varied seasonally as changing weather affected the condition of the pathway.
Early medieval road terminology An early medieval Irish law tract, Quoting produced the first written details of different categories of roads that existed in Pre-Christian Pagan Ireland. It set out five types of road:
the 'highway', slige, on which two carpait/carpenta [chariots] could pass without one having to give way to the other, the 'local road', rout [or ród], on which at least one carpat/carpentum and two riders can pass side by side as a regional main road, the 'connecting road', lámraite, a minor road connecting two major roads, the 'side road', tógraite, leading to a forest or a river, which private persons could rent, for which they then could extract tolls from people driving cattle on them, and finally the 'cow road', bóthar, which still had to be as wide as two cows, one standing parallel and one normal to the road.
Conair and cai were general terms, given in Cormac's Glossary, for any type of road and "thirty-seven ancient roads [were] mentioned with the general name bealach", meaning 'pass'. Cásan was a term used for a path and a ceis was a path made of wattles.
The word bóthar is now the most commonly used term for road in modern Irish: its diminutive form, bóithrín, (or boreen in English) is used as a term for very narrow, rural roads.
Pre-Norman bridges were not built of stone: bridges were made of timber, sometimes supported by natural rock or on artificial piers. Toirdelbach Ua Briain was said to have built a wooden bridge across the Shannon at Killaloe in 1071. Geoffrey Keating's History of Ireland notes the building of bridges among the achievements of Toirdelbach Ua Conchobair (1088–1156): "This Toirrdhealbhach built three chief bridges in Connaught, to wit, the bridge of Ath Luain and the bridge of Ath Crochdha on the Sionainn and the bridge of Dun Leoghdha on the Succa." Some "bridges were constructed of strong hurdles supported on piles". A bridge of this type gave Dublin its Irish name: Baile Átha Cliath, 'Town of the Hurdled Ford'.
Esker Riada
The Esker Riada () is a system of ridges, or eskers, that stretches across the narrowest point of Ireland, between Dublin and Galway.
Because the slightly higher ground of the Esker Riada provided a route through the bogs of the Irish midlands it has, since ancient times, formed a highway joining the east and west of Ireland: its ancient Irish name was An tSlighe Mhór meaning 'The Great Highway'. The route of the present Dublin-Kinnegad-Galway road (N4, M4, N6, M6) very approximately follows the route of the Esker Riada.
The Esker Riada also formed an ancient division of Ireland between Leath Cuinn ('Conn's Half') to the north, and Leath Mogha ('Mogha's Half') to the south.
Late medieval roads Roads were not the most important transport routes in later medieval Ireland: most long-distance travel between towns was undertaken by sea or via inland waterways. Road conditions were difficult, often dangerous, and long-distance travel by road was generally slow and uncomfortable. Giraldus Cambrensis gives an indication of the slowness of travel in 12th century Ireland, which he also describes as a "truly a desert land [i.e. sparsely populated], without roads, but well watered."
...Ireland extends from the Brandane mountains to the island of Columba, called Thorach, the length of eight good Irish days' journey, which is forty miles to the day; and from Dublin to St. Patrick's hills and the sea of Connaught it is four such days' journey in breadth.
Travel by sea was faster than by land and it was easier to transport goods in bulk by ship than by road; one estimate reckons that a ship could travel per day whereas an overland traveller might cover a distance of only .
Most tracks were not suitable for wheeled vehicles and pack animals were used to transport goods. Some attempts to improve routes were made in the Tudor period: "efforts were made to free main rivers of weirs that blocked transport, and military considerations accelerated road- and bridge-building, yet methods were somewhat unscientific and planning was haphazard." Despite these efforts, overland travel remained slow. In 1558, it took Thomas Radclyffe, 3rd Earl of Sussex and Lord Deputy of Ireland, two days to travel about sixty miles ( 100 km) from Limerick to Galway.
17th to 19th century roads
17th century In 1614, the Irish Parliament passed the (11, 12 & 13 Jas. 1. c. 7 (I)) which required local parishes to maintain roads within their boundaries which served market towns. The act did not regulate the construction of new roads or bridges although it did encourage improvements to existing roads and the construction of new ones, especially roads linking market towns in the Ulster Plantation area. The organisation of road maintenance on a parochial basis is partly responsible for the large numbers of minor roads found throughout Ireland. The (10 Chas. 1 Sess. 2. c. 26 (I)) allowed for the levying of a tax "to ensure the repair, maintenance or reconstruction of bridges, fords or causeways." This formed the basis of the presentment system which was the main system for organising the construction and repair of roads and bridges in Ireland from 1634 to 1898.