THE Stuttgart Digital Nodes (DKS) project will reach a major milestone in spring 2024 when testing of ETCS commences on sections of the city’s railway network. Teams from German Rail (DB) and the project’s major suppliers, Alstom for the vehicles and Thales for infrastructure, are working on what is described as a trailblazer of the Digital Rail for Germany (DSD) programme to rollout ETCS nationwide.

Under the DKS project, 125km of railway infrastructure will be equipped with ETCS. This includes the 60km of new railway under construction as part of the Stuttgart 21 project to construct a new main station in the city as well as 65km of connecting lines. Crucially most of the existing Class B signalling infrastructure will be removed, requiring all trains to operate solely using ETCS, a first for a major German node, and which is potentially a major breakthrough for unlocking the wider potential of the technology.
Introduction of ETCS was proposed in 2005 as the Stuttgart 21 project was taking shape. Yet the decision to introduce it as the sole signalling system was one that took a lot of soul-searching within DB and much persuasion by its proponents.

ETCS was initially discussed in terms of interoperability benefits and supporting speeds of over 160km/h, working in conjunction with the Class B system. However, ETCS emerged as the preferred solution in discussions about how to solve quality of service issues in the central core of the Stuttgart S-Bahn, which by 2015, with ridership soaring, was suffering from reliability issues and in effect becoming a victim of its own success.

With pressure set to increase further with the addition of a new main station and new tunnels that will connect with the core section, the logic of replacing the interlockings with the same technology appeared misguided. Proponents pointed to ETCS’s capability to reduce the cost of dense, performance-optimised block sections due to the use of significantly less equipment than conventional Class B systems. Around two years of discussions culminated with the launch of a feasibility study to explore the potential of using ETCS in Stuttgart in 2017.

ETCS was initially discussed in terms of interoperability benefits and supporting speeds of over 160km/h, working in conjunction with the Class B system.

DB, the greater Stuttgart region and the state of Baden-Württemberg combined to fund the €1m study, which was completed in late 2018. It concluded that it was not only possible to use ETCS on the heavily-used core section, but that headways could be reduced by 20% even with the most cautious assumption of relatively flat braking curves and slow interlockings.

The study was the foundation of subsequent work performed by DB within the framework of the DSD package to optimise the system by modifying block distances, reducing system delays and optimising ETCS braking. This would increase capacity by 35%, with the potential to reach 50% on the core S-Bahn section, enabling a switch to a 10-minute interval service and an increase to 36 trains per hour instead of 24, offering a real step-change in performance, according to the teams at DB working on the project. In practice, this translates specifically to 30m-long block sections, the shortest ever implemented in Germany.

DB and the German Federal Ministry for Transport and Digital Infrastructure (BMDV) formally announced the allocation of €462.5m of funding towards phases 1 and 2 of DKS in August 2020. This agreement includes funds originally allocated to the control command and signalling element of Stuttgart 21, funded by DB, the federal government, the state of Baden-Württemberg and the region of Stuttgart.

The initial work is split across two packages. Package 1 comprises installing ETCS in the core of the S-Bahn network, while package 2 predominately covers the new Stuttgart 21 infrastructure for long-distance and regional trains. ETCS without Class B will be installed in the core section while ETCS with Class B will be installed in two adjacent areas to support testing as well as continued operation of freight trains, which may not be operated with locomotives equipped with ETCS. Delivery of package 3, which comprises the rest of the remaining two DB Network districts of Stuttgart and Plochingen is envisaged to be completed by 2030, at which point ETCS will be installed on more than 500km of infrastructure, or about 1.5% of the entire DB network.

Map showing the rollout plan for phases 1 and 2 of the Stuttgart Digital Nodes project.

Thales was subsequently awarded a €127m contract to deliver the infrastructure component of packages 1 and 2 in November 2020. Work based on the final signalling design devised by DB involves installation of ETCS Level 2, preliminary work for the implementation of trackside systems for automatic operation at GoA2, interfaces to a future Capacity and Traffic Management System (CTMS), an operating control centre, more than 6000 electronic balises and 1300 axle-counters, and around 650 point machines.

Alstom is tasked with retrofitting 118 regional trains from various manufacturers with ETCS and ATO under a €130m contract awarded by the Baden-Württemberg State Institute for Rail Vehicles (SFBW) in July 2021. It is also equipping 215 class 423 and 430 S-Bahn trains under a €130m contract with DB Regio. In addition, Alstom won a €2.5bn contract from SFBW to supply 130 Coradia Stream High Capacity double-deck EMUs in May 2022, all of which will be fitted with equipment supporting ETCS levels 2 and 3 as well as GoA2. The trains are due to enter service in 2025. Overall, the federal government has allocated €482m to support vehicle retrofits as part of DSD. Funding has also been secured from the European Union, the state of Baden-Württemberg and the region of Stuttgart.

Alstom commenced the retrofit of the S-Bahn fleets in March 2022, followed by regional trains in April 2022. Installation of hardware on some prototype retrofit vehicles was successfully completed in late 2022, with Alstom now performing integration tests. Thales, meanwhile, is about to install the first ETCS balises with around 10% of the cabling work already completed. Indeed, DB says the amount of additional cabling required when installing ETCS alongside Class B was one of the surprising elements of the project. It has required several line closures for weeks at a time, and often at short notice, to meet the January 2024 deadline for the first part of the new interlocking, with the resulting public criticism of the scheme offering further justification to use ETCS only.

In addition, work is continuing on the control and interlocking centre in Waiblingen while DB staff are working on operational improvements, including “digital” orders/commands for fallback operation, which will be tested from December 2024.

Intensive testing

The objective is to start intensive testing of the first interlocking in spring 2024. DB reports that significant cabling work and the installation of new lineside signals is still required, but says that work is on course to meet this objective.

The start of the first commercial services using ETCS without Class B are planned for January 2025 on the Stuttgart Airport Line, an 11km mostly double-track branch line from Stuttgart-Rohr to the airport and Bernhausen in Filderstadt. Only four trains per hour per direction operate on this line, making it an ideal location for initial tests with only minimal disruption if things did go wrong. It will also provide a chance for all drivers and engineers to become even more familiar with the system before the entry into operation of ETCS without Class B on the core of the network in September 2025, at which point around 1000 trains will run without Class B through the core of the system every day. This will take place before the official opening of Stuttgart 21 in December 2025 when an additional 700 trains will operate through the station every day.

Offering a high-level of redundancy “by more or less doubling everything” to ensure a back-up system is always available is central to the project’s pursuit of reliability, while teams on the project are adopting a philosophy of “test, test, test.”

They explain that this approach offers the best possible chance of buy-in for everyone from project teams right up to senior management. It also will maximise the time available to deal with the inevitable teething problems. And while there is an acceptance that something will emerge that the project teams will not have thought of, DB believes that the comprehensive and long-term approach to planning adopted within the project will serve this process well and give it the best chance of success.

Indeed, a long-term strategy that embraces systems thinking, which encourages potentially disparate teams to talk to and work with one another to find optimal solutions, has been central to how the Stuttgart team has approached the project since work began seven years ago. DB says an emphasis on being transparent to promote a culture of trust between all parties is contributing significantly to its overall success. It is also laying the groundwork for the straightforward adoption of new or future technologies, which will help to improve performance.

The vehicle retrofit is a good example of how this approach has been applied in practice. Around 90% of project costs comprise the installation of ETCS-related equipment on the vehicle. The remaining 10% is for items that will support upcoming technologies such as FRMCS, ATO at GoA2, ETCS Level 3, and optimised braking curves. This is significantly less intrusive than installing these technologies from scratch in future years, which would require another mass retrofit programme costing many millions of euros.

Similarly, the infrastructure work has included laying the groundwork for a future upgrade to GoA2 operation, which will unlock further capacity benefits, as well as the introduction of other technologies once ETCS is stable. This includes FRMCS with DB actively working on the successor to GSM-R and the introduction of the CTMS after 2025.

DB has consulted with other railways going through their own ETCS rollout programmes, including Danish infrastructure manager Banedanmark.

CTMS will take into account parameters such as the actual train length, the speed of the train running ahead, and pantograph positions when setting a route, improving block division in stations and reducing headways. DB’s goal is to ultimately run a train on each of the new Stuttgart main station’s eight platform tracks every five minutes on average, with capacity for almost 100 trains per hour, compared with 35 at present, although operation of 50 is more likely. A five-minute headway would offer a one-minute buffer when considering the three-minute dwell time and one minute between the departure of one train and the arrival of the next.

Expectations placed on the contractors delivering the project have also changed with this systems-based approach to project management. The tender process for the infrastructure component moved away from putting all of the emphasis on price, instead weighting it towards solving system delays, which DB says incentivised bidders to deliver “something better than what was on the shelf.” This has translated into performance that some colleagues did not think was possible at the start of the project.

An illustration of the ETCS-related equipment being installed in DKS.

Crucially, DB has been open to looking outside to develop its approach to the project. Swiss Federal Railways’ (SBB) “planning pyramid” concept has proven especially influential in DB’s prioritisation of work on the Stuttgart resignalling project and the decision to pursue only ETCS. At the top of the pyramid is large-scale infrastructure, actions that should only be taken when really necessary, with components such as GoA2, ATO and fast interlockings in the middle, and dynamic timetabling and tailored rolling stock at the bottom.

Likewise, DB has consulted with other railways going through their own ETCS rollout programmes, including Danish infrastructure manager Banedanmark, which has acted as role model for the project by providing a framework for eliminating lineside signals for shunting.

Phase 3

Work is steadily getting underway on the next phase of DKS. The German government announced in December that it was increasing the funding available for the ETCS rollout programme from around €1.7bn to around €2.7bn. DB confirmed that it had received approval to further finance the planning of several projects in the starter package for DSD, including phase 3 of DKS, which will receive €83m to support planning activities.

In addition, the Rhine-Alpine freight corridor, the principal route from the Dutch North Sea ports to Italy, will receive support, as will the Scandinavian- Mediterranean corridor, which runs between Denmark and Austria and will receive €307m. Overall, DB is aiming to equip 4500km of track with ETCS by 2030.
DKS is offering a framework for a successful network-wide rollout of ETCS under the wider DSD programme. Yet the Stuttgart team’s approach to the project - embracing system thinking throughout - appears, for the moment at least, to be the exception rather than the rule within DB.

While some colleagues working on the Hamburg S-Bahn ATO project, as well as others in Cologne and Frankfurt, are reported as being very engaged, the general approach to delivering digitalisation and DSD is said to be lacking the dynamism required for a successful outcome. Siloed working remains predominant. There is a real fear among some in Stuttgart that DB could still go down the route of operating ETCS alongside Class B, thereby not realising its full benefits.

Another major concern is the issue of who will fund the vast national vehicle retrofit programme under DSD. More than 30,000 vehicles will need to be equipped with ETCS equipment at a cost of around €10bn over 10 years. The federal government has the scale to support this requirement. Yet there is a fear that with many budgetary demands, it might not have the appetite for such vast expenditure.

Both the government and DB are talking the talk on ETCS. But sooner rather than later they need to walk the walk as well. This is why members of the Stuttgart team are calling for a clearly defined strategy, that adopts systems-based thinking that will help to eliminate inefficiencies while offering a clear timeline for delivery. They believe that DKS provides a strong foundation for such an approach. The project is certainly making encouraging progress. Hopefully this success prompts further action of the type required.

Significant additional infrastructure needed to complement Stuttgart 21 project

THE German state of Baden Württemberg has published the results of a review into the provision of station capacity in Stuttgart following the completion of the new underground Stuttgart main station being built as part of the Stuttgart 21 project.

The review was commissioned by the state government, a coalition of the conservative CDU party and the Green Party, under their official coalition agreement. The Green Party has long supported constructing an additional new terminus station using part of the existing station site, and crucially the approach tracks, which are scheduled for removal once the new main station opens.

The review has found that the additional terminus station is not required, but only in the context of several major, and in many cases unfunded and currently only conceptual new sections of railway being built before 2030-2040.

The proposed infrastructure interventions, which together add substantial new capacity in the Stuttgart region, and which are considered necessary by 2030, are:

• Building the planned Wendlinger Curve as double rather than single track, allowing connections from towns such as Tübingen to the new Stuttgart Airport high-speed line and station to continue to the new Stuttgart main station. This curve is already partly complete as a single track connected to the eastbound track of the new high-speed line, and adding the extra track is considered relatively simple.
• The 11km Pfaffensteig tunnel connecting the Singen - Horb - Stuttgart Gaubahn line to the new Stuttgart Airport mainline station, and via it to the Ulm - Stuttgart high-speed line, which is already being planned with possible construction from 2026 to allow completion and opening in 2032. The twin-bore tunnel would be used by long-distance Zürich - Stuttgart and regional trains.
• Retaining the existing Stuttgart - Singen line in the Stuttgart suburbs and introducing new local services. This line, known as the Panorama Bahn, is only used by non-stop services. A new transport interchange based around the existing Stuttgart North S-Bahn station, which will be served by the new Panorama Bahn services, is planned and will increase overall network resilience.
• The addition of two new high-speed approach tracks in the northern suburbs of Stuttgart linking the existing high-speed line to Mannheim and Karlsruhe via a rebuilt station at Feuerbach with the new underground network of lines serving the new Stuttgart main station.

This last project had been identified as necessary to deliver the full Deutschland Takt regular-interval timetable but is currently unfunded and not in the planning process, as are most of the other 115 more minor infrastructure enhancements identified by the report, which are costed at €3.9bn. Baden Württemberg expects the federal government via DB Network to meet this funding requirement.

State minister of transport, Mr Winfried Hermann, who previously advocated building a new regional terminus station in addition to the planned through main station, appears to have changed his mind. He told media that the targeted doubling of demand in all public transport will lead to more than tripling the number of regional trains in the Stuttgart hub compared with 2010. He says that both new infrastructure, including the rollout of ETCS, and the new fleet of Coradia Stream trains ordered by the state from Alstom in May 2022 were key to meeting this demand.

“This will achieve the goal that the state was striving for with an underground supplementary station, reached in a different way,” he says. “I have been convinced that this is an exemplary case in which digitisation can replace infrastructure expansion.”