People should be cycling or walking short journeys and only using public transport for longer ones.
That's the view of Rail Users Ireland, following comments from Minister Eamon Ryan that introducing free public transport would cause an influx in usage.
There are fears that too many 'unnecessary' journeys would be taken.
Mark Gleeson from Rail Users Ireland says a move to free travel is not guaranteed to be successful.
"There's a bit of a conundrum that needs to be solved if we do free travel", he said.
"Luxembourg was the first city kind of in Europe to move ahead with this and they still have chronic traffic problems", he said.
"It's been tried elsewhere, but the clear evidence that we've seen that's in the EY report that the NTA commissioned is unless pre-transport is matched with significant upscaling up capacity and frequency, you're not really going to get a huge amount of benefit at all."
'Walk or cycle'
When it comes to public transport, Mr Gleeson says too many people would use it unnecessarily just because it is free and convenient, when they could walk or cycle to their destination instead.
"Imagine you're walking to the shops ten minutes and you see a bus coming and it's free, well of course you're going to hop on", Mr Gleeson said.
"There is an aspect of convenience that people would want to use the service more to kind of get value for it."
"We want to get people to make short journeys on foot or by bicycle and long journeys by public transport."
A congestion charge is also being considered for Dublin.
Outside of the major cities, Ireland’s public transport system is "bare bones", according to Mr Gleeson.
It's thought that this is another thing stopping the government from making it free.
"We don't really have a public transport system you can rely upon", he said.
"You can't make it free without providing capacity, but if you provide the capacity up front without making it free, the trains and public transport won't be busy."
"In the context of Dublin, you'd need the full DART close project, you'd need the full metrolink project.
"In Cork, you'd need electrification of Cork-Cobh-Middleton and up towards Mallow."
Main image shows Heuston station, Dublin. Picture by: RollingNews.ie