People are required by law to wear a face covering on public transport from today.
Those who don't could be hit with a fine of up to €2,500 and six-months in jail.
Drivers can refuse passengers entry or order them to leave if they are not wearing one.
Gardaí could also be called to deal with any issues.
Make sure you have your face covering ready for your journeys by train and on all public transport - face coverings are now mandatory on board.
— Iarnród Éireann #StaySafeSaveLives #HoldFirm (@IrishRail) July 12, 2020
However Dermot O'Leary, General Secretary of the National Bus and Rail Union, says members can't be expected to enforce the rules alone;
"There is confusion now in relation to who is going to be policing this...the frontline transport staff that we represent will not be policing this. In other words we are still confused about who will actually be policing this new law."