That's according to the National Bus and Rail Union
From Monday, fines of up to 2,500 euro and or six months in jail will be imposed, with some exemptions.
The law allows a driver or inspector inform Gardai of any rule breaches, and allows them stop a person without a mask from boarding.
However, General-Secretary of the National Bus and Rail Union, Dermot O'Leary, says members will be relying on Gardaí:
