Four passenger trains an hour will use the Phoenix Park tunnel at peak times when it reopens next year.
At the minute commuters terminating at Heuston have to take the luas or bus into town.
The reopening of the tunnel was announced last year as part of a 900 million euro transport plan for Dublin.
Once back in service the tunnel will bring passengers into the heart of the city as well as connecting them to the Dart.
Its anticipated that there will be 4 train services per hour from Kildare/Portlaoise through the tunnel ending in Grand Canal Dock during peak hours.
The service will operate from the spring or summer of next year and will start once a resignalling project is completed.
