Rail passengers are facing travel disruption throughout the weekend.
DART and Commuter services are suspended between Connolly and Dun Laoghaire for both today and tomorrow.
Crews are replacing the overhead wires which run above the DART line.
Meanwhile, services into and out of Heuston are also being affected by rail upgrades.
Irish Rail Spokesperson Jane Cregan said, "We have line improvement works taking place between Portlaoise and Thurles".
"We would recommend anybody travelling with us today to check IrishRail.ie before travelling as there may be a change to the departure time or arrival time of your service".