The Limerick Tunnel (Irish: Tollán Luimnigh) is a 675-metre-long (2,215 ft), twin bore road tunnel underneath the River Shannon on the outskirts of Limerick city. The tunnel forms part of the N18 Limerick Southern Ring Road. The tunnel is tolled.
Construction was carried out by a consortium of Strabag, John Sisk & Son Ltd, Lagan Holdings Ltd and Roadbridge Ltd. Traffic and Transportation planning was undertaken by Colin Buchannan and Partners. Dredging work for the tunnel trench was carried out by Dutch company Van Oord. The Austrian EFKON Group commissioned, built and currently operate two toll collection locations, one ten-lane and one six-lane plaza. Both plazas are manned and it is estimated that the two plazas will handle the amount of traffic. The immersion process of floating the tunnel elements out into the Shannon was carried out by another Dutch company, Mergor. A pedestrian open day was held on the 19 June 2010, with official opening to traffic by the Taoiseach, Brian Cowen, on 27 July 2010, two months ahead of schedule.
Total cost of construction was €660 million.