Plans for Dublin’s long-delayed MetroLink are due to be announced later this morning.
Cabinet was last night told that the multi-billion Euro project is not expected to be operational until 2034.
More than €250m has already been spent on the project, which is expected to cost about €9.5bn by the time it is completed, making it the largest rail investment the country has made since the 19th century.
It was originally proposed in 2005 and at the time, was expected to cost €3bn.
The 19km line will stretch from Charlemont near Ranelagh to the north side of Swords.
Yesterday Transport Minister Eamon Ryan got Cabinet approval for the project, with Transport Infrastructure Ireland now set to submit a planning application to An Bord Pleanála.
The plan will be launched at an event later this morning.
According to the Department of Transport, construction will begin in 2025, with the first trains to start running by 2034 at the latest.
Additional reporting Michael Staines.