Deutsche Bahn Launches 11 km Pfaffensteig Tunnel in Germany

Pfaffensteig Tunnel Construction Initiated

Deutsche Bahn (DB) has commenced preparatory work for the 11 km Pfaffensteig tunnel near Stuttgart, Germany, following the grant of a building permit in December 2025 by the Eisenbahn-Bundesamt (EBA). The project is supported by a EUR 1.7 billion financing agreement concluded between the German federal government and DB. This tunnel is a core component of the modernization of the Stuttgart–Zurich international rail corridor.

Project Execution and Phasing

Initial construction activities are concentrated on a three-hectare site located north of Stuttgart Airport and the A8 motorway. Current earthworks involve the removal of topsoil and subsoil to prepare for the excavation of the main launch shaft. Following this, access roads will be constructed, and provisions will be made for a sound-absorbing panel. High-capacity drilling equipment is being mobilized to the site for these preparatory stages.

From the completed launch shaft, two tunnel boring machines (TBMs) will excavate the two parallel galleries of the tunnel. The project’s planning and approval process is divided into two primary sections. The Planning Approval Section 1 (PFA1), for which the building permit was granted at the end of 2025, covers the 10.8 km main section to be constructed using mining methods. The subsequent Planning Approval Section 2 (PFA2) includes an approximately 300-meter section built using open-cut methods and the connecting above-ground railway sections to the Goldberg S-Bahn station, situated between Böblingen and Sindelfingen. Documentation for PFA2 approval was submitted to the EBA in April 2025.

The project employs a partnership model, structured as an alliance with future construction contractors. This collaborative approach was utilized during the design phase to accelerate planning and will extend through all execution phases to manage the complexities of a large-scale infrastructure build.

Strategic Framework and Market Impact

The Pfaffensteig Tunnel is a priority project within Germany’s Federal Railway Infrastructure Requirements Plan and is legally defined as being of “major public interest” under the Federal Railway Expansion Act. This designation mandated the federal government to commission DB for its construction. The tunnel’s primary strategic function is to connect the Gäubahn line directly to Stuttgart Airport and the future Stuttgart Hauptbahnhof, resolving a long-standing network bottleneck. This integration is a critical prerequisite for implementing the national “Deutschlandtakt” integrated timetable on this corridor, which depends on precisely timed connections at key hubs.

The new connection fulfills a key requirement of the financing agreement for the broader Stuttgart 21 project, of which this tunnel is a component. For passengers and operators, the project will yield quantifiable reductions in journey times. Travel time between Stuttgart and Zurich will decrease by approximately 15 minutes. Commuters will see a more pronounced benefit on the route between Böblingen and Stuttgart Airport, with travel time falling from 22 minutes to approximately 7 minutes.

The direct airport link will also enhance network connectivity, allowing passengers on the Gäubahn to make efficient transfers to high-speed services toward Ulm and Munich. The project’s alliance-based delivery model is strategically relevant as German rail infrastructure authorities seek methods to de-risk and accelerate complex projects by integrating contractor expertise earlier in the lifecycle.

Next Steps

With preparatory work underway, the next operational milestone is the commencement of excavation for the TBM launch shaft. The project’s progression also depends on the successful completion of the regulatory approval process for the PFA2 section by the Federal Railway Authority.