Irish Rail has started a major crackdown on fare evasion with ticket inspectors and senior managers taking to station platforms to track down offenders.
As many as one in every 16 passengers using Iarnrod Eireann services is travelling without a ticket, it has been revealed.
Chief executive David Franks said that one recent blitz on the Dublin commuter network saw inspectors issue 108 penalty notices to people intending to travel, but without a ticket.
Some 75pc of the €100 penalty fares were paid, he said, adding that the company planned to raise €1.5m in additional funds this year by clamping down on fare evasion.
But the true extent of the problem could be far bigger than first believed, he admitted.
"We convinced ourselves we had 1pc of revenue at risk," he said. "Our checks are demonstrating it's 6pc, but it could be higher."
The company raised €157.9m in passenger fares last year, up €1.3m on 2011.
Ten more blitzes are planned over the coming weeks across the commuter, Dart and inter-city network.