During the Iron Age, roads were built across bogs using timber. These roads were known as tóchar and the name still survives in some place names. As these ancient roads fell into disuse, they disappeared into the bog and thus the original timbers were preserved to modern times. For many years the primary communication routes for long distance were by sea and inland waterways as well as by road. Now with continuous investment in roads and in particular the long distance primary routes, sea transport is kept as short as possible because land transport is far quicker and more comfortable. Investment in the National Primary routes and National Secondary routes is channelled through the National Roads Authority, with the local County Council or Corporation still playing a major role in design, land purchase and construction.


The Scheme cost IR£24million and included the following elements:

  • 16.5 km of National Primary Route

  • 1.5 km of National Secondary Route

  • 10.0 km of new and improved access and county roads
  • Some of the main statistics for the
    project are as follows:

  • Excavation of 1,500,000 cubic metres of boulder clay

  • Excavation of 330,000 cubic metres of rock

  • Excavation of 150,000 cubic metres of soft ground and replacement with rock. The soft ground was up to 11 m deep in places

  • Dealing with 130 separate land
  • This project, considered as an important contribution to the infrastructure of Connacht and the North West, was carried out between 1995 and 1998. This new road, which is partly in Counties Roscommon and Sligo and runs west of Lough Key and Lough Arrow, replaces the old N4, which involved a torturous ascent and descent over the Curlew Mountains. Roscommon County Council were responsible for project management of the scheme, which was undertaken in part by direct labour and in part by contract.

    An Environmental Impact Statement was carried out for the project. This was not required by legislation but was undertaken because of the sensitivity of the landscape through which the road traversed.
    Measures undertaken to reduce the visual impact of the new road included the soiling of rock embankments, which otherwise would have been evident from 5 km away.


    Oranmore Bypass to the Quincentennial Bridge and was constructed in a number of phases between 1983 and 1996. Approximately 1.0 km of Phase 1 and 0.7 km of Phase 2 of the road was founded on weak alluvial soils located in the Terryland River basin. The depths of soft ground varied up to 11 metres and consisted of peat, calcareous marl, organic clay and inorganic silty clay. The methodology used to construct the road in these conditions included:

    • Placement of geotextile fabric on the undisturbed ground surface
    • Placement of free draining layer of crushed limestone
    • Construction of embankment to a surcharge height of 0.5 to 1.0 m above the finished road level in order to accelerate settlement during the construction period
    • The maximum recorded settlement was 3.3 m
    • Placement of vertical band drains on a 1.4 m square grid over the entire embankment area in order to accelerate pore pressure dissipation in the various soil layers
    • Installation of a comprehensive instrumentation system to measure pore water pressure, vertical
      settlement and lateral movement

    The above methods, to deal with the weak soils, were first applied in Ireland on the Galway Eastern Approach Road and the Athlone Relief Road

    The bitumen pavements, which are used on almost all Irish roads, consist of a mixture of aggregate, filler, bitumen and additives. There has been considerable research in additives over the years in order to produce a variety of materials to match different requirements. Chemoran, based in Oranmore and a member of the Cold Chon Group of companies, has been producing specialised chemical products for the roads industry since the late 1940's. It now exports to some 56 countries in five continents.

    The materials developed and manufactured at the Oranmore plant include adhesive agents to improve the adhesion between bitumen and stone and various additives used in the manufacture of many types of cationic bituminous road emulsions. A research laboratory has been established in conjunction with NUI, Galway. It is an example of how new products are developed through collaboration between the private sector and third level institutions and involving scientists and engineers.l institutions and involving scientists and engineers.

    In the year 2000, design teams are in place for a number of significant roads projects in the West of Ireland and the National Development Plan, 1999 includes for major expenditure on roads over the first decade of the new millennium. Implementation of this roads programme will improve connectivity between the West and the rest of country and presents opportunities for engineers in the design and construction stages.