Two of those will run to Dublin and one back to Athlone.
Extra train services will run to cope with demand from Offaly fans travelling to Sunday's All-Ireland U-20 football final.
They will operate from Athlone to Heuston at 9:50am and 10:05am on the day of the game.
Irish Rail is also running an additional return service at 5:30pm that evening from Dublin.
The company's spokesperson Barry Kenny says fans need to book ahead:
Sunday 15th August (Roscommon v Offaly, Croke Park)
09.50hrs Athlone to Heuston
10.05hrs Athlone to Heuston
17.30hrs Heuston to Athlone
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