Irish Rail is warning it will have to stop Dart services again today to finish repairs on the signalling system.
Dart services on the southside were shut down between Pearse and Dún Laoghaire.
They're now running again with a 10-minute delay.
It was the second time today part of the signalling system on the line has broken down.
An intercity service to Rosslare which uses the same rail line has also been delayed.
Irish Rail says Dublin Bus is accepting rail tickets.
Services suspended between Pearse and Dun Laoghaire due to recurrence of earlier signal fault. Working to resolve issue.
Dublin Bus will accept rail tickets.
10.25hrs Connolly to Rosslare Eurosport delayed— Iarnród Éireann (@IrishRail) August 4, 2019