Over 230 million journeys were taken on Ireland's public transport services last year.
According to new figures from the NTA, the number of trips taken has increased by almost 31 million since 2013.
All Public Service Obligation (PSO) operators have experienced an increase in that three-year period with Dublin Bus increasing from 112m to 125m; Bus Éireann 29m to 32m; Iarnród Éireann 37m to 43m; Luas 31m to 34m.
In addition, LocalLink, the rural transport programme increased passenger numbers from 1.74m to 1.79m between those years.
Anne Graham, CEO of the National Transport Authority said: “The figures we are publishing today are an indication that there is a clear demand for an efficient and reliable public transport service. Particularly so when the public transport alternative is environmentally friendly and offers value for money.
“It is also remarkable that we have been able to accommodate this increase in passenger numbers with virtually no increase in PSO operating capacity as measured by seat kilometres nor in the number of licensed commercial bus operators.
“In other words, transport operators across the State have managed to sweat their fleet assets to the greatest possible extent to provide services for the greatest possible number of people.
“But there’s only so much that can be done within the current constraints and we are now at the point where we need significant investment to address the burgeoning problem of congestion."