A new underground Dart service linking Heuston Station to the Docklands which is scheduled to cast €2bn is set to go ahead -- despite the fact the two destinations are already linked by a fully functioning but little used railway known as "The Ghost Line". .

The existing high speed railway travels from Heuston through the Phoenix Park tunnel before surfacing again and travelling through Cabra, Phibsboro, Drumcondra and onto Connolly Station and on to the Docklands

The neglected rail link is fully functioning and occasionally carries freight and is used to shunt locomotives between Dublin's two main railway stations.

Now a rail user lobby group have questioned the vast amount of money which is earmarked for a new tunnel under the city when the old Victorian railway line could be used to service some of the city's most densely populated areas.

"They are wasting an incredible asset and instead ploughing vast sums of money into a new inter-connector tunnel," said Derek Wheeler of Rail Users Ireland. "The rail lines have been there for over one hundred years and have carried passenger trains in the past and are begging to be used again. It is a rapid rail service that can be up and running within a year. The whole system is just about ready to go."

In the past, the Phoenix Park tunnel was portrayed as an unsuitable, crumbling and leaky vestige of Victorian engineering. But in reality the tunnel was engineered to the highest standards and is vast and cavernous. Approximately 757 yards in length, it was built to accommodate two wide gauge 9 foot 10 inch trains travelling in either direction.

"Transit time to either Connolly or the North Wall from Heuston would be about 10 to 12 minutes and the Phoenix Park route would have the benefit of servicing a lot of densely populated areas," said Wheeler.

"Currently, the lines through the Phoenix Park are fully signalled to passenger standards, with signal spacing adequate to support trains at approximately five minute intervals in both directions." However, Iarnrod Eireann insists that the Phoenix Park route is a non runner and would only add to the congestion at Connolly Station:

"The Phoenix Park tunnel is currently used for freight services and special train services, particularly during the GAA season," said spokesperson, Barry Kenny. "Using the park tunnel would result in cancellations of other services. Connolly station is at full capacity at peak times, and using the park tunnel in this way would not generate any additional commuter capacity in the greater Dublin area. Kildare services could not serve Heuston without an additional platform and track work being provided there, and could not serve docklands without track modifications at a multi-million euro cost."

Three years ago, Iarnrod Eireann had an entirely different view. On February 25 2004, Joe Maher, the then chief executive of the company told the Dail Transport Committee: "We certainly intend to use the park tunnel in the short-term to bring trains from the Kildare/Newbridge area into Spencer Dock because there is demand for that."

Meanwhile, Transport 21's proposed inter-connector tunnel which would extend the Dart service to Heuston and onwards to Park West, Adamstown and Hazelhatch is being hailed as a panacea to all the city's public transport needs. In 2003, it was estimated that the new inter-connector would cost €1.3bn. However, the cost of major infrastructure projects have a history of spiralling out of control, and some critics have suggested that the new tunnel could eventually end up costing €2bn.