It dwarfs the scale and impact of the Port Tunnel.
The €2bn underground Dart through the heart of Dublin city centre will run every three minutes and carry up to 70,000 commuters an hour.
New images showing the scale of what will be one of the biggest ever infrastructure projects in Ireland, due to open in 2015 and comprising two entirely new Dart services, were also released yesterday.
The 5.2km line, an underground tunnel from the Docklands to Heuston station, will increase rail capacity from 33 million passenger journeys annually now to over 100 million.
Dr John Lynch, Iarnrod Eireann and CIE chairman, yesterday described the Dart underground line as "the missing link, not only in our rail infrastructure, but in our transport infrastructure".
"It will be the most critical project under Transport 21 in enabling people to switch from private transport to public transport, and will transform the capacity of the greater Dublin area rail network."
As part of the exciting plans, the northern line Dart services from Balbriggan and Howth will branch off the existing line after Clontarf Road, going underground at Docklands station, where they will connect with the red Luas line.
The Dart interconnector will continue underground to Pearse Station, before connecting with the green Luas and Metro at St Stephen's Green, and proceeding to Heuston. The Dart will go overground to Adamstown and Hazelhatch in Co Kildare.
A second new Dart line will connect Maynooth -- and a massive M3 park and ride at Pace -- to the existing Bray/Greystones Dart line, stopping at Glasnevin and Drumcondra.
Crucially, the new links join all rail modes -- Dart, commuter rail, intecity, Luas and the proposed Metro. A railway order application is being submitted for the project in 2009.
Timetable for underground link
- 2001: Project included in blueprint for integrated greater Dublin transport.
- 2006: Scheme is approved under the massive €34bn Transport 21 package.
- 2007: Public consultation.
- 2008: Detailed site investigations.
- 2008: Iarnrod Eireann will apply for a Railway Order for the project -- equivalent to planning permission.
- 2009: Public hearing into the underground, followed by an inspector's report. The many parts of the project will then be put out to tender.
- 2010: Construction work will begin involving a twin-bore tunnel at 30 metres depth. Some stations will be mined (Christ Church, St Stephen's Green), with others built using 'Cut and cover' methods (Heuston, Docklands).
- 2015: Underground open.
Treacy Hogan Environment Correspondent