Property developers and landowners will fund half the estimated cost of €300 million to extend the Luas Green Line from Sandyford to Cherrywood, via Leopardstown, according to Frank Allen, chief executive of the Railway Procurement Agency (RPA).
"No rail scheme anywhere in Europe has captured that level [of private-sector support]," he told The Irish Times. "We've done deals with most of the developers on transferring land along the 7.5km route at a deep discount, and they've made some financial contributions as well.
"This is for real - we have money in the bank," Mr Allen said, adding that a levy scheme by Dún Laoghaire-Rathdown County Council "takes care of the 'free rider' problem" - a reference to landowners along the extended line who would make windfall gains from enhanced property values.
However, he said the line - approved last August - was "in jeopardy" because of a High Court legal challenge by the owners of a listed Georgian house due to be demolished to make way for it. This case may be heard before the end of January, and the RPA was "confident" of winning it.
About half the estimated €80 million cost of the proposed 3.5km spur from Belgard on the Tallaght Red Line to Citywest is also being funded by developers - although in this case a consortium led by Brendan Hickey, of Davy Hickey Properties, will actually build the line, including its four stops.
"We don't even have to think about land costs [along the route] because they will transfer it in its entirety to us, on the basis that we will put in the electrics, telecoms and trams and provide a level of service. We will be submitting an application for the line to An Bord Pleanála in January," Mr Allen said.
He conceded that trams on the Sandyford line were already overcrowded during morning peak periods and that the extension to Cherrywood could make this worse."We increased capacity last September, running a four-minute service at peak periods, and that's made a big difference. But clearly there is a problem between 8.15am and 8.45am. We will increase the frequency even more and we're also looking at increasing the length of trams to 50 metres."
He also conceded that journey times on the Red Line between Tallaght and Connolly Station were often taking up to 48 minutes - five minutes longer than originally envisaged - mainly because of congestion on-street, hold-ups at traffic lights and motorists indulging in "red light running".
At certain junctions, particularly in the city centre, motorists were still "ignoring red lights" and there had been several accidents that put trams out of commission for months.
Asked whether Luas gets sufficient priority at junctions, Mr Allen said: "I'm not picking a fight with Dublin City Council, but its roads department still sees the movement of cars in the city as having priority, which I don't share, so we will continue encouraging them to to give trams more priority."