The Irish Cabinet has approved a preliminary business case from the National Transport Authority to submit a planning application for the metro line to An board Pleanála in September.
The project, which has a tentativecost ofmore than 9.5 billion euros, will be the largest investment in railway infrastructure in the country this century.
Under the plan, the metro line would consist of a fully segregated railway, much of which would be underground, from Swords in the north to Charlemont in Dublin.
It will serve Dublin, Ballymont and Glasnevin airports.
The project will start in 2025 and be completed between 2031 and 2034.
Cabinet has been informed that it is too early to determine the exactcost , but reliable estimates of thecost, which have been stress-tested,put the final figure above 9.5 billion euros.
