Irish Rail is conducting engineering works.
Engineering work continue on the line between Kildare and Portlaoise tonight.
Irish Rail says the project will mean alterations or delays to some services tonight, and on Friday night.
In some cases, bus transfers are in operation.
The services affected over the next three nights are:
22:10 Heuston to Portlaoise will operate to Kildare only, bus transfers direct from Kildare to Portlaoise, second bus transfer from Kildare to Monasterevin, Portarlington and Portlaoise
20:33 Portlaoise to Heuston will operate in an altered path
21:25 Portlaoise to Heuston is cancelled
22:30 Portlaoise to Heuston will commence from Kildare at 23:05 and will operate in an altered path