>>1289519>But why not take some branches and convert them to low floor and run them along that new corridor? Essentially establishing two different intertwined systems.That's an interesting idea, but it has a whole lot of problems on its own. On the south side, all lines emerge from the underground in the same place (Rathaus station). It wouldn't be too hard to build a new trunk line from Adenauerplatz via Klosterstraße, Jahnplatz, Willy-Brand-Platz to Hauptbahnhof (central station). But then what? You either have to build new tunnel entrances to two of the four northern branches, or lay track for surface connections. In the second case, geography would only allow access to the northern branch of line 3 (behind Nordpark) and line 2 (behind Beckhausstraße).
And then there is the looming idea of converting the system to standard gauge, which would have to be done at the same time (if ever).