Deutsche Bahn has begun preparatory work for the excavation of the 11 km Pfaffensteig tunnel, which is part of the expansion and modernization of the Stuttgart–Zurich international rail link.
North of Stuttgart Airport and the A8 motorway, DB is carrying out earthworks on the central site designated for the construction site.
As part of the preparatory work currently underway, the topsoil and subsoil will first be removed from an area of approximately three hectares. Subsequently, access roads to this area will be built, preparations will be made for the construction of a sound-absorbing panel, and high-capacity drilling equipment will be brought in. The work currently underway is intended to enable the excavation of the launch shaft for the mechanized drilling of the tunnel. From this shaft, the two galleries will be excavated using two tunnel boring machines.
Within the framework of the Partnershipsmodell Schiene railway partnership model, the design of the Pfaffensteig tunnel was completed in record time. With the construction of the Pfaffensteig tunnel and the application of this partnership model, a major railway infrastructure project is being implemented for the first time in all relevant phases of execution together with future contractors as alliance partners.
The project planning is divided into sections. The building permit granted at the end of 2025 for the PFA1 approval section covers the 10.8 km long section of the Pfaffensteig tunnel that is being constructed using mining methods. PFA2 follows the approximately 300-meter section built in open cut, followed by the above-ground railway sections to the Goldberg S-Bahn station, located between Böblingen and Sindelfingen. The documentation for the approval of the second section of the project was submitted to the Federal Railway Authority (EBA) in April 2025.
The Pfaffensteig Tunnel connects the Gäubahn to Stuttgart 21
The modernization of the Gäubahn line, including the construction of the Pfaffensteig Tunnel, is included as a priority project in the Federal Railway Infrastructure Requirements Plan. Thus, the Pfaffensteig Tunnel, as part of the Federal Railway Expansion Act, is considered to be of “major public interest.” Consequently, the federal government has commissioned Deutsche Bahn to build the tunnel.
The construction of the Pfaffensteig Tunnel will connect the Gäubahn line to the airport and, subsequently, to the future Stuttgart Hauptbahnhof central station.
The tunnel thus also fulfills an essential component of the financing agreement concluded between the Stuttgart 21 project partners.
The tunnel forms the basis for implementing the “Deutschlandtakt” concept on the Gäubahn line and will reduce travel time between Stuttgart and Zurich by approximately 15 minutes. Many passengers will also benefit from the reduction in travel time between Böblingen and the airport from 22 minutes today to around 7 minutes in the future. In addition, passengers on the Gäubahn will be able to make quick transfers at the airport to high-speed connections to Ulm and Munich.
Recently, the federal government and DB concluded the financing agreement for the Pfaffensteig tunnel, worth EUR 1.7 billion, and in December 2025, the Eisenbahn-Bundesamt (EBA) granted the building permit for most of the project.
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