Rail Users Ireland has criticised Irish Rail for its handling of disruption on on the Dart line yesterday.
Dart trains on the southside were stopped a for third time last night because of another signal fault.
The line between Connolly Station and Lansdowne Road was closed from 9.30pm until the end of the day's timetable.
It follows two previous stoppages earlier in the day because of technical problems with the signal system.
Irish Rail said the fault has now been fully repaired, and no further disruption is expected today.
Mark Gleeson from Rail Users Ireland was caught up in the disruption at Connolly Station.
He says passengers were badly let down last night.
"The displays as you entered the station clearly showed there were delays, but it didn't show any cancellations," he said.
"It wasn't until I got to the barrier line where I was actually blocked by staff who said 'Where are you going?' and I said 'Dún Laoghaire' and he said "Oh no, there's nothing south to Dún Laoghaire' and I said 'The display behind you says there is' and the usual kind of 'that's not my problem' conversation ensued."
"It had been ongoing at that point for several hours, so why [wasn't] the chalkboard wasn't put out in the middle of the floor to tell passengers what to do? It's just completely unacceptable," he said.