Irish Rail is reverting to its old morning timetable today.
All routes to and from Connolly station in Dublin will return to the pre-August 26th service patterns.
It follows complaints regarding the revamped timetable, which led to delays on morning services.
It's hoped today's changes will re-balance the timetable to improve punctuality, while accommodating improved frequency on a number of intercity routes.
In a statement online, Irish Rail said it was "to address punctuality issues".
They said: "Iarnród Éireann is to implement a number of significant changes to its timetable from Monday 14th October, following punctuality issues being experienced by customers since a new timetable was implemented on 26th August last."
The most significant changes are to the early morning and mid morning commuter rail and DART services to and from Connolly Station, Belfast, Drogheda and Maynooth.
South East routes are the least effected by the older timetable being reinstated.
There will be some minor changes to departure times on the Dublin to Rosslare train to facilitate the above.
The increased services on the Waterford line, that was implemented on 26th August, will be retained.
Irish Rail say they are sorry for the disruption caused that was a direct result of the new timetable.
"Iarnród Éireann deeply regrets the disruption to our customers’ daily journeys and lives which have resulted from timetable changes since 26th August.
"In accommodating increased services on the Dublin to Belfast route, and managing overall capacity in the city centre area, the changes had a disproportionate negative impact on commuting punctuality and overall journey times, for which we are sorry.
"We recognise the enormous disruption this has caused our customers’ work, education, childcare and other requirements, and how critical the punctuality and reliability of our services are to the daily lives of our commuting customers.
"While changes made on 16th September improved evening punctuality in particular, it is clear that the impact to morning commuting was continuing."
A full list of changes can be found at www.irishrail.ie.
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