Tony Dempsey

Tony Dempsey

Direct Route Construction Joint Venture
Co. Clare


Roughan & O'Donovan completed permanent and temporary works design of this major, multi-span viaduct at the N7/N18 interchange northwest of Limerick City.


Structure B11 on the Limerick Southern Ring Road Phase II (Limerick PPP Scheme) carries N7 mainline traffic over a slip road and tidal creek.

It comprises:

  • Fully integral, twin viaducts, 169.6m and 178.5m in length
  • 6 spans on the south structure and five spans on the north structure
  • In situ cast reinforced concrete boxes with a maximum span/depth ratio of 23
  • Inset, single leaf piers to minimise visual impact
  • Shallow deck cantilevers to enhance the bridge’s slender appearance


The challenge lay in designing a high quality structure that could be constructed economically in complex soft ground conditions; settle well within a rural environment; and service a very busy traffic flow.


Our innovative design provided substantial benefits, in terms of construction and whole life maintenance costs, to our client.

Services provided:

  • Bridge engineering design
  • Geotechnical design
  • Temporary works design
  • Alignment and road works engineering design