The 18km-long proposed light-rail system in Dublin, Ireland, will cost €2.5bn ($3.47bn), rather than the original estimate of €3.7bn ($5.13bn).
The Metro North project will connect Swords to Dublin city centre and will serve destinations including Mater hospital, DCU, Ballymun and Dublin Airport.
To date, the Railway Procurement Agency has spent €175m ($242.9m) on land acquisition, pre-construction works and planning.
The metro system, which is awaiting final approval from the Irish planning board, could cost about €138m ($191.59m) per kilometre, according to independent.ie.
The project is expected to generate over €1bn ($1.3bn), while a final cost-benefit case has to be worked once the board decision is made.
The European Investment Bank has approved €500m ($694m) funding for the project, and subject to the necessary approvals being granted, work will start by the year's end or early 2011.