The wisdom of spending €1 billion to build an "interconnector" rail tunnel linking Heuston Station with Pearse Station and Connolly Station/Spencer Dock has been seriously questioned by the recently formed railway lobby group, Platform 11.
A more practical and immediate solution to integrating rail transport in Dublin in the short term would be to use an existing rail route through the Phoenix Park tunnel which currently has no passenger services, according to the group.
Platform 11 says Dublin already has a perfectly good and operational double-track rail line that runs from Heuston to Connolly stations just waiting to be used.
"It is perhaps the best-kept secret in the history of urban rail transport anywhere in Europe."
It claims that such a service could be operational within a year. In effect, it would mean that passengers on the south-western suburban routes could travel to Connolly - and ultimately Spencer Dock - rather than Heuston.
Platform 11 has drawn up its own proposals for a "cross-city shuttle" between Heuston Station and a planned new station at Spencer Dock.
It claims that the existing line from Heuston Station to Connolly Station via Cabra, Glasnevin and Drumcondra is grossly under-used and could be developed at a fraction of the cost.
At present the line is used by freight trains and for moving stock to depots for maintenance purposes.
"It is a situation that would be unheard of in any other European city, let alone a gridlocked capital notorious for its lack of public rail transport," according to the group.
"Our transport planners seem obsessed with grandiose and massively expensive tunnelling concepts that will take years to complete, while part of the solution to Dublin's congestion problem is staring us in the face."
According to Platform 11 steering group member, Mr Derek Wheeler, it is not opposed to the "interconnector" idea in principle and would be supportive of any investment to enhance public transport.
However, past experience pointed to cost overruns and longer timescales than planned.
"CIÉ had plans for a rapid rail system as far back as 1973, little of which has been implemented apart from the DART," he notes.
In the Strategic Rail Review, published last week, consultants Booz Allen Hamilton contend that the Phoenix Park tunnel route "offers no real opportunities for passenger services".
"Passengers who currently alight at Heuston are unlikely to be attracted by an extra 15- minute trip to Spencer Dock Station, particularly when the Luas system service is operating from Heuston Station to Connolly Station," it says.
But Mr Wheeler points out that the use of the Phoenix Park route would mean more options and more capacity - and with the Luas, the cost of having an interconnector tunnel as well would have to be questioned.
He feels that the "interconnector" option is being "done at the expense of the regions". Rather than spending €1 billion on this project, the same money could progress a number of new schemes highlighted in the SRR.
Mr Wheeler instanced such schemes as Galway-Limerick-Cork (€290 million), an enhanced Cork suburban service (€124 million), Limerick-Shannon-Ennis (€117 million), Athlone-Mullingar (€154 million), Derry-Letterkenny (€151 million), and Navan-Drogheda (€110 million).