The General Secretary of the National Bus and Rail Union feels it's only a matter of time before a bus driver is seriously injured in an assault.
In the last number of months, seven Bus Éireann drivers have been assaulted by members of the public and it has led to a number of the drivers going on sick leave, he alleged.
Dermot O'Leary of the NBRU described an aggressive incident which happened recently in County Kildare.
"We've had another incident very, very recently in Kilcullen where a driver was assaulted because the passenger didn't have enough money to pay for his fare and the driver said he couldn't carry him unless he paid a fare," he said.
"On that particular occasion, a number of passengers intervened and the man had to be restrained.
"Duck tape had to be used until the gardaí came."