New rail tunnels beneath Dublin moved a step closer this week when Irish Rail began seeking firms to design, construct and operate the system.
The company has published a notice asking for submissions from firms interested in taking on the €2.5bn project.
The proposed twin tunnels will route DART trains underground from the Docklands to Inchicore. They will be 7.6km long and will run 24 metres below the surface for much of its east-west route.
A planning application will be made next month for the proposed public-private partnership project. It is planned to begin DART services through the tunnels in 2016.
More than 7,000 construction jobs may be created during the project along with many more in supply services.
The DART underground is an integral part of the Government's 10-year transport plan which also includes the provision of a Metro rail service in the city and an extension of the LUAS tram service. The new networks would be linked to Intercity rail services. The current DART north-south coastal route would be split in two in the city centre.
The underground DART service would consist of two rail lines operating in side-by-side tunnels. The tunnels would have 20 trains running in each direction every hour carrying a total of 64,000 passengers.
The new DART line will run from Docklands to Heuston Station and Inchicore via St Stephen's Green.
Irish Rail has already begun public consultation on the line and proposed stations.
Trains will run every six minutes along the underground line, with stations at Inchicore, Heuston, Christchurch, St Stephen's Green, Pearse Street and Docklands.
The increased frequency will see the number of passengers carried on the Greater Dublin rail network triple from about 33m journeys in 2008 to 100m journeys. Construction is due to begin next year.
The new system will require northside DART passengers heading south to change at Pearse Street to access stations from Grand Canal Dock to Greystones. And their trains will no longer stop at Connolly or Tara Street.
Southside passengers heading north will have to change at Pearse Street to reach any stations from Clontarf.