Disruption was caused due to a mechanical fault on a train.
Irish Rail will review how significant delays on a midlands service were handled.
A mechanical fault on a train led to major disruption between Portlaoise and Heuston Station.
It resulted in some services delayed for a number of hours, while at one stage, passengers on a train to Cork were transferred using ramps to a Galway train.
Irish Rail's Barry Kenny has apologised to passengers impacted: