The Jack Lynch Tunnel, described as the most challenging civil engineering project in the history of the state, is unveiled on May 21, 1999 by Taoiseach Bertie Ahern at the entrance of the tunnel in Mahon, County Cork.
The Jack Lynch Tunnel is an immersed tube tunnel and an integral part of the N40 southern ring road of Cork. It is named after former Taoiseach Jack Lynch, a native of Cork. Construction involves the excavation of a large casting basin where the tunnel elements or pieces are constructed. After construction of elements is complete, the casting basin is filled with water and joined to the adjacent River Lee, each element is floated out and sunk into position into a carefully dredged river bed.
The tunnel takes the road under the River Lee. North of the tunnel, the ring-road joins the M8 motorway to Dublin and N8 road to the city centre, with the N25 road commencing east to Waterford. The tunnel is completed in May 1999, and carries nearly 40,000 vehicles per day as of 2005. This number rises further as the N40 ring-road’s upgrades progress, with the opening of the Kinsale Road Roundabout flyover in 2006 and subsequent upgrades to the Sarsfield Road and Bandon Road Roundabouts. Traffic in 2015 is 63,000 vehicles a day up from 59,000 in 2013.
The tunnel has two cells, each with two traffic lanes and two footpaths, and a central bore for use in an emergency only. Pedestrians and cyclists are expressly forbidden from using the tunnel. The exclusion of cyclists has been somewhat controversial as the feeder road is a dual-carriageway and so is open to cyclists, but the by-law is applied because of space limitations and the obvious danger of cyclists in an enclosed tunnel.