It's being claimed DART Underground is 'vital' to future-proof Dublin's public transport network.
Plans to develop a rail line beneath the streets of the capital have long been talked about, but never funded.
Brian Caulfield from the School of Engineering at Trinity College Dublin believes it needs to be prioritised.
He explained that "the infrastructure we are using for the DART from Connolly to Bray is Victorian infrastructure".
"So by introducing DART Underground it would alleviate this congestion, is perhaps a more priority project than others", he said.
It comes as Irish Rail continues to work to fix "teething problems" with its higher frequency DART service.
The trains now run every ten minutes on weekdays from just before 7am until 8pm.
However, passengers getting used to the changes have been complaining of packed carriages and delays.
The company says it expects to have all issues ironed out in the next "week or two".
Brian Caulfield has dismissed suggestions Irish Rail needs to overhaul its entire network.
