Dublin could have a new six-line metro system in place by 2025.
That is according to the CEO of Metro Dublin, Jed van der Poll.
He says Dublin could introduce six new lines at a fraction of the cost that could save the commuter almost three weeks a year in travel time.
The lines would run from Ashbourne, Swords, Donaghmede, Rathfarnham, Blanchardstown and Adamstown.
These radial lines would then link up in a central loop to run under the city.
This would see 19 major hubs connect with DART, Luas, mainline rail and bus routes.
Mr van der Poll told Newstalk Breakfast: "It's going to cost €9bn and its going to be paid by private financing.
"What gives me the confidence to give a figure that is approximately a third of what would normally be considered for a scheme of this type is a guy called Professor Manuel Melis Maynar.
"He is the architect of Metro Madrid and he did this in Madrid: he built 120 kilometres of metro in just seven years and at a fraction of the price that, say, London Underground paid for the Jubilee Line".
The proposed Metro Dublin line (in red) | Image: metrodublin.ie
On the funding, he said: "Because it's a third of the cost, the capital sum is so much lower and that can be funded by private investment.
"We would be looking for half of that funding - so approximately 4.5 billion - from the European Investment Bank (EIB).
"That has extremely low interest rates, and it's why the EIB was set up - just for this type of infrastructure project in Europe".
The architect of the project is civil engineer Cormac Rabbitt, who originally put forward the plan for Metro Dublin.
"We've met with (Transport) Minister Shane Ross, we've introduce him to Prof Melis.
"And what is interesting about Prof Melis is the World Bank wrote a paper on what he did - and they called his achievements superb and from which the whole world could learn.
"And what we would like is for Shane Ross to go to Madrid and see how it can be done.
"He was a very positive response. I was warned that Shane Ross is a very straight-forward man and if he thinks it's a non-runner he'll tell you straight to his face.
"He gave us 45 minutes Of his time, we were very pleased."
Mr van der Poll says Minister Ross is currently examining the data.
Dublin Metro is also in discussions with An Bord Pleanála about the project.
Under previously announced plans, the emerging route of one line between Swords and Sandyford is to cost approximately €3bn.