The changes will affect selected Saturdays throughout the year
There will be some major disruptions to services at Irish Rail this weekend due to engineering works taking place.
Passengers using services to and from Heuston Station, and all connecting services, are advised to re-check times before travelling.
DART services are not operating north of Connolly Station in Dublin - but normal services will resume on Bank Holiday Monday.
Anyone traveling tomorrow to the 1916 commemorative event outside the GPO in Dublin are being advised to bear these changes in mind when planning their journey.
Iarnród Éireann say the annual investment of €10m will lead to higher reliability, smoother running of trains and deliver consistent 160kph speeds.
The programme of line improvement works is focusing on the section between Hazelhatch and Thurles.
There will be service changes on selected Saturdays throughout the year.
However works will not take place during the peak tourism and sporting season of August, or on Saturdays of other major events - i.e. sports and concerts.
Affected routes include Cork, Limerick, Tralee, Galway, Westport, Waterford, Portlaoise and Kildare.
Also on affected Saturdays, first class facilities will not be available.
Irish Rail have outlined full details of the changes for the affected days on its website.
The company has apologised for any inconvenience caused by the arrangements.
They have put together a video to explain the operations being carried out: