Vienna Subway Expansion: Tunnel Boring Machine "Debohra" Reaches Its Destination at Augustinplatz

Technical Dimensions Underground

The 127-meter-long boring machine handles all work steps in one pass: excavating the tunnel and installing the tunnel lining. For the tunnel shell, 2,850 rings made up of around 17,000 individual concrete segments were installed. In total, around 150,000 cubic meters of earth were excavated – equivalent to about 60 Olympic swimming pools.

Thirty-five meters below Augustinplatz, the machine with its seven-meter-diameter cutting wheel towers at the center of the construction site. "Das war eine technische Meisterleistung und es war die komplexeste Bauphase", summarized Gudrun Senk, technical managing director of Wiener Linien.

City councillor for transport Uli Sima (SPÖ) pointed out that construction was continued "trotz budgetär angespannter Zeiten". "Es fehlt an allen Enden", she said with a view to the city's strained budget situation.

Costs and Postponements

The costs for the subway construction are contractually split equally between the City of Vienna and the federal government: 2.1 billion euros were earmarked for the first expansion stage. Due to delays and high inflation, additional costs of 300 million euros were added, as Wiener Linien calculated.

For budgetary reasons, the start of construction for the U5 extension was postponed by one year to 2028 last year, and the start of construction for the U2 from Matzleinsdorfer Platz by two years to 2030. Originally, the U5 was supposed to have begun operations by the end of this year.

The opening of the first construction stage remains scheduled for 2030, as Senk confirmed on Friday. The completion of the second construction stage is targeted for "Mitte der 2030er-Jahre"; the city does not give a specific date.

Route of the New Lines

The new U5 line takes over the previous U2 route between Karlsplatz and Rathaus and then continues in the first expansion stage to Frankhplatz. The provisional terminus is also the only new U5 station.

In the future, the U2 will run from Rathaus via Neubaugasse (transfer to the U3), Pilgramgasse (transfer to the U4), and Reinprechtsdorfer Straße to Matzleinsdorfer Platz (transfer to the S-Bahn). In the second expansion stage, the U2 is to be extended to Wienerberg, and the U5 from Frankhplatz toward Hernals.

The originally planned temporary dual routing with the U2 has been cancelled. According to Wiener Linien, this saves between 18 and 20 million euros in operating costs.

Environmental Balance and Capacities

"Wir freuen uns besonders, ‚Debohra' an ihrem Ziel beim Augustinplatz begrüßen zu dürfen", said Wiener Linien chief Alexandra Reinagl. The machine will now be dismantled and returned to the manufacturer in individual parts.

More than 800 people are deployed daily for the expansion. "U2xU5 zeigt, wie technische Kompetenz, Innovation und Nachhaltigkeit ineinandergreifen", explained Monika Unterholzner, deputy general director of Wiener Stadtwerke.

Thanks to the underground construction method, around 20,000 truck trips and 75 tons of CO2 were saved. Some of the excavated material is not deposited but is reused as Vienna clay for brick production. The shift in transport is expected to save up to 75,000 tons of CO2 per year.

The city's largest infrastructure project is intended to noticeably relieve heavily used lines such as the U3, the U6, tram line 43, and bus line 13A. Additional capacity for up to 300 million passengers per year is being created annually.

"Die Investitionen in den Ausbau der U2 zum Wienerberg und in den Neubau der U5 nach Hernals zeigen: Wien setzt konsequent auf leistungsfähige Öffis als Rückgrat der städtischen Mobilität – und als Antwort auf Wachstum, Klimaziele und steigenden Bedarf", Ludwig stated.