The Stuttgart-Ulm railway project will improve the railway connection between Stuttgart and Ulm in Germany. Credit:
The Stuttgart 21 is being developed by railway company Deutsche Bahn and is expected to be completed in 2025. Credit: Thomas Niedermüller.
The Wendlingen-Ulm railway line of the project was inaugurated in December 2022. Credit:
The Stuttgart 21 project includes the construction of the Stuttgart main station. Credit: Arnim Kilgus.
The project included the excavation of 51km of tunnels. Credit: Reiner Pfistere/PORR.

The Stuttgart-Ulm railway project, also known as Stuttgart 21 or S21, is an infrastructure project being undertaken by the railway company Deutsche Bahn to improve the railway connection between Stuttgart and Ulm in Germany.

The project is being carried out with an estimated investment of €9.79bn ($11bn). Construction on the project commenced in 2010.

The Wendlingen-Ulm railway line of the project was put into operation in December 2022. The entire project is expected to be completed in 2025.

Stuttgart 21 project background

The Stuttgart 21 project originated in 1994 and aimed at tackling the operational penalties created for the many services routed via the city.

The broad ‘Y’ configuration of tracks south into Stuttgart makes trains on key rail arteries like Menchen-Mannheim/Frankfurt Main retrace some of the route following reversal at Stuttgart Hbf, located at the northern edge of the city’s central zone.

The reversals and complex track work continue to constrain the potential for shorter journey times, even with the many light engine movements of former years obviated by push-pull and multiple-unit operation.

Approval for the Stuttgart 21 was given in July 2007.

Stuttgart-Ulm railway project details

The Stuttgart-Ulm railway project comprises two sub-projects, including Stuttgart 21, aimed at expanding the Stuttgart railway hub and developing the new high-speed Wendlingen-Ulm railway line.

The Stuttgart 21 project will completely reorganise the Stuttgart rail junction by constructing four new stations, 57km of new railway track to accommodate trains with speeds of up to 250km/h, 59km of tunnel tubes, 16 tunnels and culverts and 44 bridges. Construction on the project commenced in February 2010.

Excavation of the tunnels started in December 2013 and was completed in October 2022. The tunnels were excavated using tunnel boring machines as well as conventional construction methods comprising excavators, blasting and chisels.

The Stuttgart 21 project will also create two new districts, Rosenstein and Europa, in the middle of the city, covering an area of 100ha for urban development. Residential and commercial space will cover an area of 50ha in the Rosenstein district, along with a park covering 20ha and green spaces and public squares covering 10ha. The Europa district will span an area of 20ha.

Stuttgart main station details

The Stuttgart main station is the primary component of the railway hub renovation aimed at handling the projected higher number of trains on the Deutsche Bahn network. The new station will also provide connections with the regional transport network without the need for changing trains.

The foundation stone for the station was laid in September 2016. The existing station serving tracks from the north will be replaced by a new station with eight inbound and outbound tracks, set just beneath the surface immediately north of the present concourse.

The station’s roof features a concrete shell design comprising 28 chalice-shaped pillars with large glass domes that provide daylight in the platform hall. Each pillar with a diameter of 32m (105ft) will require up to 350t of steel and 685m³ of concrete.

The new station will provide more capacity, shorter dwell times, less complex approaches, reduced maintenance occupations and fewer conflicting movements.

Wendlingen-Ulm railway line details

The Wendlingen-Ulm railway line reduces the travel time between Stuttgart and Ulm by nearly half and improves regional and local transport in Baden-Wurttemberg.

Construction of the line commenced in 2012 and included the development of a 60km-long railway track, 61km of tunnel tubes, 12 tunnels, 37 bridges and the Merklingen station. A new signalling system was also constructed as part of the project.

The 8,176m-long Albvorland tunnel, the 8,806m-long Bossler tunnel, the 4,847m-long Steinbuhl tunnel and the 5,940m-long Albabstieg tunnel are the four longest tunnels on the new railway line. The project also features a 485m-long and 85m-high bridge known as the Fils Valley Bridge, which is the third-highest railway bridge in Germany.


The S21 project is being carried out with an investment of €9.79bn ($11bn).

The funding partners for the S21 project include Deutsche Bahn, the federal government, including EU funding, Baden-Wurttemberg state and its capital Stuttgart, Stuttgart Airport and the Stuttgart Region Association.

Contractors involved

DB Projekt Stuttgart-Ulm, a project company of Deutsche Bahn, is implementing the project.

Architecture firm ingenhoven architects is the architect for the Stuttgart main station.

The ARGE ATCOST21 consortium, consisting of construction companies PORR Bau, Hinteregger & Sohne Baugesellschaft, Ostu-Stettin Hoch-und Tiefbau and Swietelsky Baugesellschaft, was responsible for the construction of the Filder tunnel.

The Bossler tunnel was constructed by ATA ARGE Tunnel Albaufstieg, PORR Bau, G. Hinteregger & Sohne Baugesellschaft, Ostu-Stettin Hoch-und Tiefbau and Swietelsky Baugesellschaft.

The Albvorland tunnel construction was undertaken by Implenia Construction.

CDM Smith, an engineering and construction company, was contracted to provide building assessment and geotechnical consulting services.

Arup, a professional services company, provided building information modelling (BIM) management and infrastructure design services.

DB Engineering & Consulting, a railway consulting company; MC-Bauchemie, a chemicals manufacturer; SULZLE Stahlpartner, a steel company and gmp Architekten, an architecture firm, are some of the other contractors involved in the project.

Tekla, a BIM software solutions provider; ACO, a water technology company; OESTU STETTIN, a formwork contractor and Herrenknecht, a tunnelling company, are also part of the project.

Project benefits

The S21 will help shift traffic from the road to the railway network, reducing travel times on long-distance and regional routes.

The travel time from Ulm to Stuttgart airport will be reduced from 1.35 hours to 30 minutes and between Rottweil and Stuttgart airport from 2.02 hours to 59 minutes. In addition, the travel time between Stuttgart main station and Stuttgart airport will be reduced from 27 minutes to eight minutes and the Tubingen-Stuttgart airport route from 65 minutes to 35 minutes.

The Stuttgart rail node reorganisation will benefit more than ten million long-distance passengers throughout Germany each year. Furthermore, the project is providing employment opportunities to approximately 6,000 people.