Planning for a fourth U-Bahn expansion phase began in 2001 and concrete ideas were put forth in the 2003 Transport Master Plan.
In 2007, there are plans for the extensions in Vienna, this provided the necessary extensions:
The extended U2 from Aspernstraße to Seestadt Aspern (then time horizon 2013)
The extended U1 from Reumannplatz to Rothneusiedl (then time horizon 2015)
The extended U2 from Karlsplatz to  Gudrunstraße (then time horizon 2019)
Planning for a fourth U-Bahn expansion phase began in 2001 and concrete ideas were put forth in the 2003 Transport Master Plan. In 2007, there are plans for the extensions in Vienna, this provided the necessary extensions:
The extended U2 from Aspernstraße to Seestadt Aspern (then time horizon 2013)
The extended U1 from Reumannplatz to Rothneusiedl (then time horizon 2015)
The extended U2 from Karlsplatz to  Gudrunstraße (then time horizon 2019)
Vienna U-Bahn