First Phase:

Tallaght-O'Connell Street - £130 m

Sandyford-St Stephen's Green - £70 m

Broadstone-Ballymun - £100 m

O'Connell St-Connolly Station - £20 m

Tunnel in city centre - £100 m

Ballymun-Dublin Airport - £50 m

Second Phase:

Spur to Finglas - £10 m

Extension to Cabinteely - £20 m

Extension to Docklands - £40 m

Extension to Swords - £20 m

Total - £560 m

Source: Best estimates by transport experts consulted by The Irish Times