Traffic simulations using a model of the Marienplatz in Stuttgart

Making urban tangible

forschung leben – the magazine of the University of Stuttgart (Issue March 2022)

One goal of many communities is to better involve local residents in the urban planning process, digital technologies with realistic 3D visualizations can facilitate this. The High Performance Computing Center Stuttgart (HLRS) is supporting such approaches in several research projects.
[Photo: University of Stuttgart/HLRS]

Marienplatz is a central location in the southern district of Stuttgart, where there is a subway station, bus stops and taxi ranks, as well as the terminus of the “Zacke”, Stuttgart's cog railroad. One of the main routes of the cycling network in Baden-Württemberg's state capital also runs through this area. The square is also part of a main pedestrian route in the south of Stuttgart. Weekly markets attract even more people. Marienplatz is a popular meeting place and a vibrant urban center, but this also leads to conflicts between road users, which is felt by pedestrians and cyclists in particular, who are, of course, the most vulnerable road users. The City of Stuttgart wants to reduce the dangers and inconveniences faced by these groups at Marienplatz, to which end it is being transformed into a Real-World Laboratory

Citizen participation 2.0: Traffic simulations using a model of the Marienplatz in Stuttgart

Improving conditions for cyclists and pedestrains

“Choosing a mode of transport not only depends on cost and time, but also on whether a particular form of mobility is perceived as particularly pleasant,” explains Dr. Fabian Dembski, a research associate at the HLRS. “This is heavily influenced by any conflicts experienced along the way and subjectively perceived stress.” So anyone who wishes to promote cycling and walking would do well to reduce such inconveniences.

To this end, the HLRS is coordinating the “Cape Reviso” research project, which is funded by the German Federal Ministry for Digital and Transport, the aim of which is to improve the situation for the most vulnerable road users with the aid of digital technologies and the involvement of social groups. The Karlsruhe Institute of Technology (KIT) and the German Bicycle Club (ADFC) are involved in the project, as are other associated partners such as the City of Stuttgart. In addition to the one in Marienplatz, more Real-World Labs are planned in Stuttgart, Karlsruhe, and Herrenberg. The “Cape Reviso” project was launched in the summer of 2020 and is scheduled to run for three years.

Dr. Fabian Dembski and his team have created a digital twin of the city of Herrenberg

Duration: 1:41 | Source: YouTube

Analyzing the traffic situation with the aid of a digital twin

“We make use of various methods in the project, which we then make freely available to the extent that this is possible,” says Dembski. “Community planners can then use this toolbox and expand as they see fit.” The project participants operate on two levels: First, they use a digital twin of Marienplatz and use sensors and artificial intelligence (AI) to record and analyze the traffic situation. The HLRS had already produced a digital model of Stuttgart in an earlier project, upon which the digital twin of Marienplatz will be based, which will be a virtual representation of the actual square that can be zoomed into from various perspectives. “We will then be able to perform various network analyses to see, for example, exactly which routes cyclists prefer to follow, which will enable us to identify potential danger zones,” Dembski explains.

Finding the best routes: digital twins are designed to help ensure that roads are well designed for all road users

At the same time, volunteers will equip their bikes with distance sensors, which were developed as part of the “Open Bike Sensor” volunteer project. Participants will be able to detect dangerous situations just by pressing a button on the handlebars. This will produce useful information when used in conjunction with distance and GPS data. “We will use a similar approach with pedestrians,” says Dembski. The KIT has developed a stress meter for this purpose. Sensors on the wrist record physiological data such as the pulse and the electrical resistance of the skin. A distance sensor and camera will be carried ina backpack so that the measured physiological data can be associated with external events. “It's clear from the details that collecting data is easier for bicycle traffic than it is for pedestrian traffic,” says Dembski. “The reason we go to such lengths to collect data in the first place is simple: the statistics don’t reflect such events such as near misses.”

Public Involvement

The project participants are also planning to install cameras at Marienplatz which will automatically record bicycle and pedestrian traffic movements. “Because the data is processed directly in the camera units, there is no need for them to store images,” Dembski explains. “They will only store anonymized metadata about road users and their behavior, such as whether someone is walking, riding an e-scooter, or cycling, and whether they are moving, braking, or standing still.” The HLRS team will first have to train the AI algorithm to recognize these things. “We will also be asking the public for their support for this,” Dembski adds. “They can manually link exemplary imaging data with metadata.” The AI algorithm will then automatically analyze the situation at Marienplatz and produce meaningful data over a longer period.

“Thanks to digital technologies, ...we are able to involve the public ... to a much greater degree.”

Dr. Fabian Dembski

“Thanks to all this data, people will then be able to try out the virtual 3D representation of Marienplatz to see how certain traffic control measures would affect the number of conflict situations,” says Dembski. The camera network will also be able to perform similar analyses when these measures are field-tested. “We also plan to set up a large-scale physical model in Marienplatz to give citizens the opportunity to share their visions.” After all, they know the place best, he said. “Thanks to digital technologies,” Dembski explains, “we are able to involve the public in the design of urban spaces to a much greater degree, and in such a vivid manner that everyone will understand.” Rather than presentations and plans, the planned changes are shown in three-dimensional representations, in which the people merge with the scenery.

Out and about in Marienplatz with the skateboard simulator

The green twins project in Estonia and Finland

The HLRS is also involved in another participation project in Tallinn and Helsinki: The EU-funded “Green Twins” project was launched in January 2021 and is scheduled to run until May 2023. Dembski holds a research professorship at the Tallinn University of Technology in Estonia, which is leading the project. The Aalto University is also involved the Finnish side.

Whilst it is true that Tallinn in Estonia and Helsinki in Finland are separated by the Gulf of Finland in the Baltic Sea, the two cities are only 80 kilometers apart and share a very similar climate, fauna, and culture. The aim of the “Green Twins” project is to create a digital twin of the urban green spaces and then to analyze their interrelationships with the built environment in 3D visualizations and simulations, whereby as Dembski explains, referring to application examples, “key issues include plant care, root growth, as well as the urban micro climate. “The HLRS is contributing its knowledge of highly detailed digital twins to this effort.” There are also plans to establish a permanent public participation and collaboration center in the Tallinn city center, where, members of the public will be able to preview future urban planning measures via two large 3D displays. “In this way, the City of Tallinn wants to bring about a permanent improvement in the respective planning processes,” Dembski explains. “The aim is to get the general public, architectural firms, academia, and city government talking to each other.”

Dr. Fabian Dembski, e-mail, phone: +49 711 685 87297


This image shows Andrea Mayer-Grenu

Andrea Mayer-Grenu


Scientific Consultant, Research Publications

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