The City Council would need to convince motorists that public transport will be able to meet their needs before cars can be banned from the city on a full time basis.
The National Bus and Rail Union says investment would be needed for park and ride facilities and additoional buses before any proposal to pedestrianise the entire city could be considered.
The Oireachtas Climate Action Committee are looking at ways to cut carbon emissions in half by 2030 and say more people would use public transport if it was free of charge.
Speaking to RedFM News, Dermot O'Leary from the NBRU says he agrees with the idea of banning cars, but that it would need significant investment.
"The structure has to be right around park and ride, for example, and Bus Rapid Transit. You would encourage people and you could justify banning traffic from the city then.
"Until such time as that structure is ready, the push back quite rightly from would come.
"If you can convince people that everything is in place, for you to use public transport to get from A to B, then we believe it would be a good idea."
