Face coverings will be compulsory on public transport from today as capacity will increase from 20% to about 50%.
National Transport Authority chief Anne Graham said people are being asked to do the right thing.
She added: “This is an important part of efforts to build confidence in public transport as more people return to work over the coming weeks and months.
“At this stage, our focus and that of the operators is on education, awareness and giving our customers every encouragement to wear a face covering.”
Meanwhile face mask rules should be loosened for people with respiratory diseases, the Asthma Society of Ireland said.
It wants the exemptions for face coverings for people with the condition.
Chief Sarah O’Connor said: “For asthma and COPD patients, the feeling of struggling to catch a breath is very familiar and one they strive every day to avoid.”
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