The Dublin Tunnel (Irish: Tollán Bhaile Átha Cliath), originally and still commonly known as the Port Tunnel, is a road traffic tunnel in Dublin, Ireland, that forms part of the M50 motorway.
The twin tunnels form a two-lane dual carriageway connecting Dublin Port, which lies to the east of central Dublin, and the M50 motorway at junction 2, close to Dublin Airport. The tunnels are in length and total project length of . It had a final cost of approximately €752 million.
The tunnel was officially opened on 20 December 2006; it was initially only open to HGVs. It was opened to all traffic on 28 January 2007.
Purpose
Traffic congestion in central Dublin became severe at the end of the 20th century, with thousands of heavy goods vehicles (HGVs) travelling to and from Dublin port via the city centre. The tunnel relieves surface road congestion in Dublin city centre by diverting HGVs from Dublin Port directly onto the motorway network. This has positive knock-on effects for bus users, pedestrians and cyclists travelling along the city quays, including better air quality and safer travel.
To discourage commuters from using the tunnel, vehicles other than HGVs are heavily tolled at peak times. HGVs travelling north and west benefit from the expected six-minute journey time through the tunnel. A tunnel was chosen as it was decided that a surface relief road was not feasible.
Dublin Bus routes 142, 33x and 41x use the tunnel to get to the port area of the city from the northern suburbs.
Longer distance buses from Belfast, Derry and Letterkenny also use the route.
Port tunnel project
The tunnel was first suggested in the 1990s after a number of transportation and engineering studies and was included in the Dublin City Development Plan 1999 – 2005. The project was approved following a public inquiry in 1999.
The tunnel formed part of the National Development Plan and funds were provided under the plan to the National Roads Authority by the Department of Transport. The contract was managed by Dublin City Council and supervised by Brown & Root, a unit of Halliburton. The main contractor was a Japanese-British-Irish consortium Nishimatsu Mowlem Irishenco (NMI), appointed in 2000.
The tender price for the construction of the tunnel was €457 million. The final project cost was brought to €752 million by land acquisition, design, insurance, legal and other services, plus supervision by Brown & Root.
Construction commenced in June 2001 and the tunnel was originally due to open in 2005 after an elapsed time of 43 months. It eventually opened in December 2006, giving an elapsed time of 66 months.
One reason for the project extension was to allay residents' noise concerns. Under some areas such as Griffith Avenue and the Cloisters, boring was restricted to 16 hours per day. Under Annadale Crescent, it was reduced to 13 hours.
Tunnel specifications
Length: – total project
Bores: 2
Bore width: 11.77 m (38 ft 7.82 inches) Lane width (two per bore): 3.65 m (11 ft 11.70 inches) Shoulder width (two per bore): 1 m (3 ft 3.37 inches) Bore height: 4.9 m (16 ft 0.91 inches) Operating height: 4.65 m (15 ft 3.07 inches) Lowest point: -30 m (−98 ft 5.10 inches) at Marino
It is the fourth longest urban motorway tunnel in Europe after Madrid M-30, Blanka tunnel complex in Prague and Södra länken in Stockholm, Sweden. When non-urban road tunnels are included, the Dublin Port Tunnel is shorter than some other European tunnels, such as the Lærdal Tunnel () in Norway (24.5 km), the Gotthard Road Tunnel in Switzerland (17 km), the Mont Blanc Tunnel between France and Italy (11.6 km) and the Western Scheldt Tunnel () in The Netherlands (6.6 km).
Tunnel design
The tunnel was built in five sections including a pipe-jacked section under the Dublin-Belfast railway line.
Cut and cover
The "cut and cover" sections at both ends featured excavations as deep as 12 m into which horseshoe-shaped sections of reinforced concrete were cast in-situ and backfilled. The southern section, at Fairview, is 500 m long while the northern cut and cover channel from Whitehall Church to Shantalla extends over 1500 m. This work was undertaken by the Mowlem and Irishenco units of the consortium.