The new underground railway station and high-speed rail lines in Germany's southwestern hub Stuttgart will not open in December 2026 as previously planned, Germany's Deutsche Bahn said on Wednesday.

It's the latest of a series of delays to a major project also beset by vast cost overruns which has been under construction for 15 years now.

Amid various German media reports on the delay, Deutsche Bahn published a brief press statement noting how it had recently warned of "deadline risks" for Stuttgart 21's opening, tied specifically to the so-called Stuttgart Digital Node (or DKS to use its German-language acronym) aspect of the project.

This is a plan for a digitized signaling and safety system in the area, with Japanese company Hitachi a key partner, eliminating old-fashioned light signals altogether. 

It said that these risks had intensified during the development and approval phase of the project with the contractor and led to a delay. The company did not commit to a new opening target or other details, but pledged to provide more information as soon as possible.

"In the spirit of maximal transparency we will inform as soon new developments emerge," Deutsche Bahn wrote. "The deadline risks have intensified to an extent that was not previously foreseeable and are now being evaluated with the Supervisory Board. Please have understanding that we don't wish to preempt that discussion." 

Stuttgart 21 under construction since 2010

Stuttgart 21 has been one of a series of major German public construction projects in recent decades that became emblematic of budget overruns, delays and controversy. 

Conceived and first presented to the public as an idea in 1994, it was contentious even before the foundation stones were laid. 

Construction only began in 2010, amid fierce disagreements on the plans, their implementation, and their environmental credentials. These culminated in violent clashes between protesters and police in September 2010.

The issue was credited as a core campaign point for the Greens, who perhaps counterintuitively opposed the rail modernization plans, in the state of Baden-Württemberg's 2011 elections, when Winfried Kretschmann became the party's first state premier anywhere in Germany. He still holds the position. 

The Greens even held a referendum proposing abandoning the project, in a manner not entirely dissimilar to the UK's recently discontinued HS2 rail line, but roughly 59% of participants voted in favor of continuing.

The project's initial budget in the planning phase was €2.6 billion (roughly $3 billion at current exchange rates), rising to €4.2 billion by the start of construction, and sitting at an estimated €11.3 billion as of May this year.

Various reasons given for delays, gradual opening phase expected

The original planned opening date was 2019.

Several delays followed, most recently Wednesday's, and German media reports suggested that a new date at some point in 2027 was likely to emerge when Deutsche Bahn commented further — at least for a partial launch.

The rail company had previously anticipated that long-distance high-speed trains, and some local services, would be the first to relocate to the new underground main rail station, with other local services following later. 

The project also incorporates the construction of several other train stations in the Stuttgart area, such as a new long-distance hub at the city airport, as well as dozens of kilometers of new tracks, tunnels and bridges. 

The company has cited several reasons for the various delays, including lawsuits against the project, changed standards on issues like fire safety, geological complications encountered underground in Stuttgart, and challenging permit processes and changing laws on environmental issues like species protection. 

Edited by: Wesley Rahn