Has the final component of the Stuttgart 21 project been confirmed?

The Deutsche Bahn has initiated the approval process for another section of the Pfaffensteigtunnel, a crucial eleven-kilometer underground connection of the Gäubahn towards the airport. However, the funding for this ambitious project remains a subject of debate, with skepticism expressed by rail expert Matthias Gastel (Greens) and the outgoing Bahn CEO Richard Lutz.

Geologically, the route for the Pfaffensteigtunnel is considered unproblematic. The tunnel's inclusion in the budget draft was urged by the interest group Gäub-Neckar-Bodensee-Rail, which represents neighboring communities, and regional associations along the route. The residents of Gäubahn are optimistic that the Bundestag will also pass the inclusion of the tunnel in the budget.

However, the funding agreement may not be possible in 2025 as originally planned. The DB performed the preliminary work out of self-interest to avoid re-planning and returning to a controversial variant that would share S-Bahn tracks to the airport. This variant was met with doubts about its traffic feasibility, protests from residents, lengthy participation processes, and several re-plannings, which delayed this section.

Internal estimates by Deutsche Bahn suggest that at least another billion euros are still needed for the tunnel. This additional cost is not included in the 2026 investment plan, which allocates 1.69 billion euros for the federal government's investments in rail infrastructure, with an additional 270 million euros to be provided by the other S21 project partners.

Despite the financial challenges, the current planning period for the construction of the Pfaffensteigtunnel on the Filderbahn extends until 2028. If the Bundestag approves the financing in autumn 2025, it could lead to the start of construction around 2029 with a completion expected in the mid-2030s. The tunnel is scheduled to be completed by 2032.

It is worth noting that the last unfunded component of the Stuttgart 21 project is now included in the draft of the federal budget 2026. All trains from the direction of Gäu and Lake Constance will have to start and end at the city's outskirts in Stuttgart-Vaihingen for several years, even after the completion of the Pfaffensteigtunnel.

The approval process for the Pfaffensteigtunnel is a significant step towards improving rail infrastructure in the region. However, the funding and cost concerns remain a hurdle that needs to be addressed before the project can move forward. The Bundestag still needs to approve this draft in the fall, and the fate of the Pfaffensteigtunnel hangs in the balance.