Trunk Line
On 3 July 2019, Deutsche Bahn announced the new "2. Stammstrecke — Die Optimierungen" (Second Trunk Line Optimisation). The State of Bavaria and the Munich city council want the first U9 station to be built at the Hauptbahnhof at the same time as the reconstruction of the Hauptbahnhof main building and the construction of the second S-Bahn trunk line. The design revision relocates the U9 platforms from the west end of the regional and long-distance platforms to the middle of the main Hauptbahnhof building below ground. The relocation places the U9 station directly above the second trunk line station in a cross arrangement. This improves the passenger flow between two current U-Bahn lines (U4/U5 and U1/U2/U7/U8), one current S-Bahn trunk line, and the above-ground level.