The second phase involved the expansion of the U3 and U6 lines (about 61 km (37.9 mi)).
The groundbreaking ceremony for this phase took place on 7 September 1983 on Pottendsdorfer Street at the Philadelphia Bridge and after six years, the central section of the U6 between Philadelphia Bridge and Heligenstadt/Friedensbrücke went into operation.

After completion of the basic network, the Vienna subway system was extended in 1989 to the line U6 with the route Heiligenstadt-Philadelphiabrücke (10.6 kilometers).
For the belt line, the last remaining line of the light rail, had been modernized and converted to legal traffic.
In order to preserve the valuable building fabric, the line was not rebuilt for operation with the underground railcars of the other lines; tram or metro-like trains with overhead power lines were used.
Northern line endpoint was now only Heiligenstadt; the alternative northern terminus of the last light rail line, Friedensbrücke (U4), was not approached.
1995 followed the first extension of this line in the south: from Philadelphiabrücke (now station Meidling) to Siebenhirten including the elevated railway line of the former express tram line 64 over a length of 5.2 km.
In 1996, the U6 was extended in the north to Floridsdorf and the previous terminus Heiligenstadt (U4) is no longer approached.
The two remaining, abandoned links of the former light rail are like much of the U6 listed building and are now partly used as a bike path.

In 1991, the completely newly built line U3 between Erdberg and Volkstheater was opened, which crosses the first district after the U1 as a second line.
The western terminus Ottakring was reached in 1998, the southeastern end of the U3 is since the year 2000 in the station Simmering.
The total length of the network increased with these construction measures of the second stage to 61 kilometers.
The second phase involved the expansion of the U3 and U6 lines (about 61 km (37.9 mi)). The groundbreaking ceremony for this phase took place on 7 September 1983 on Pottendsdorfer Street at the Philadelphia Bridge and after six years, the central section of the U6 between Philadelphia Bridge and Heligenstadt/Friedensbrücke went into operation.
After completion of the basic network, the Vienna subway system was extended in 1989 to the line U6 with the route Heiligenstadt-Philadelphiabrücke (10.6 kilometers). For the belt line, the last remaining line of the light rail, had been modernized and converted to legal traffic. In order to preserve the valuable building fabric, the line was not rebuilt for operation with the underground railcars of the other lines; tram or metro-like trains with overhead power lines were used. Northern line endpoint was now only Heiligenstadt; the alternative northern terminus of the last light rail line, Friedensbrücke (U4), was not approached. 1995 followed the first extension of this line in the south: from Philadelphiabrücke (now station Meidling) to Siebenhirten including the elevated railway line of the former express tram line 64 over a length of 5.2 km. In 1996, the U6 was extended in the north to Floridsdorf and the previous terminus Heiligenstadt (U4) is no longer approached. The two remaining, abandoned links of the former light rail are like much of the U6 listed building and are now partly used as a bike path.
In 1991, the completely newly built line U3 between Erdberg and Volkstheater was opened, which crosses the first district after the U1 as a second line. The western terminus Ottakring was reached in 1998, the southeastern end of the U3 is since the year 2000 in the station Simmering. The total length of the network increased with these construction measures of the second stage to 61 kilometers.
Vienna U-Bahn