Construction work began in March 2001 on the Tallaght to Connolly line, as well as the Sandyford to St. Stephen's Green section of the second line, with Ansaldo of Italy and MVM of Australia getting the contract to build the system.
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Ticket machines accept card payments (by American Express, Laser, MasterCard, or Visa for transactions from €5 upwards and a weekly limit of €150 (upper limit changed from €50 per transaction to €150 per week in January 2012 after upgrading all POS terminals to have a PIN keypad).
The tunnel as proposed by Iarnród Éireann would provide stations at Heuston (linking with the Kildare Line), High Street, St Stephens Green (linking with the Green Luas line and the Airport Metro), Pearse (linking with a DART service from Greystones to Maynooth) and Spencer Dock (continuing on to Drogheda and linking with the Red line Luas).
An extension of the LUAS Green Line is planned to cross the River Liffey, and intersect with the Red Line at the junction between O'Connell Street and Abbey Street and terminate at Broombridge (in Cabra) to interconnect with the Irish Rail Broombridge railway station.