The National Bus and Rail Unions say the uptake of wearing face masks on public transport is as low as 30 percent in some parts of the country.
The latest Department of Health figures shows 41 percent say they're wearing them.
It comes ahead of new laws which make it compulsory to wear a face-covering on public transport from Monday.
Fines of up to €2,500 and or six months in jail will be imposed for failing to observe news laws on wearing face masks on public transport.
They allow a driver or inspector to inform gardai of any rule breaches.
Taoiseach Micheal Martin said the National Transport Authority will also have the authority and capacity to stop people boarding if they're not wearing a mask.
Children under 13 and people with special needs will be exempt.
General Secretary of the NBRU Dermot O'Leary says people are still not getting the message about wearing face masks.
"It has improved over the last number of weeks but we're still not at the stage where it's at 100 percent. In Dublin, it's been as low as 30 or 40 percent. it's a bit higher in rural areas of the country, but it's still not at the levels you'd expect it to be from a compulsory point of view."
