It's Tuesday afternoon between 4 and 6 p.m. in Nuremberg. People have finished work and are starting their journeys home through the northern Bavarian city, which is home to around 550,000 citizens. The result: traffic jams. The A73 city freeway is blocked, and crowds are packing into the subway. It's a situation that repeats itself just about every afternoon. However, this could change in the future... if Nuremberg manages to duplicate itself. Only in virtual terms, of course – by creating a digital twin of the city! This digital representation would show traffic flows, buildings, green areas and much more. There's enormous potential in the simultaneous recording and mapping of movements of people, vehicles and goods: If you record such data across an entire city, you can understand, simulate and steer the corresponding flows. This might reveal how great an obstacle a particular construction site actually is, for instance. And traffic is just one aspect of the potential: Registering photovoltaic systems makes it possible to steer the urban energy transition, and usage data enables the selective planning of entire districts.
Every subway passenger is a data donor
For this purpose, the city of Nuremberg took part in the EU-funded “twi.N City” project, which aims to develop a city model based on geodata. The hope is that it will be possible to use the data to draw conclusions about visits to downtown Nuremberg and how attractive the area is. The city's transport operator, VAG, was also involved. The subway in Nuremberg has long been relying on extensive data collection and use, particularly since a driverless, fully automated subway system was put into operation in 2008 – long before the term “digital twin” was used in reference to cities. “Integration is everywhere,” says Andreas May, who was involved as a project leader in the implementation of the driverless subway and is now the head of rail operations at VAG. For him, purely driving-related operations are also just part of the potential to use the data at hand. Every passenger in the subway is a data donor. During their journeys through the city, people generate movement data that provides details about the traffic flows in the entire city.
In the twi.N City project, the VAG data was supplemented with information about parking garage occupancy and the weather. This has created a comprehensive picture of the current activity in the city. That includes Adlerstraße in the city center, which is a street that runs between two counting points installed at subway stations. A dashboard shows that an average of 39,797 people pass through the area around Adlerstraße every day, and they typically spend a considerable amount of time there. At the same time, the occupancy of the nearby parking garages indicates how many people travel to the city center by car. Adlerstraße is a pilot project for showing how data can be recorded and collated in order to derive subsequent measures to make the area more attractive.
Nuremberg is just one of several cities that have taken on the challenge of creating an urban digital twin. At present, there are several initiatives underway across Germany; the funding project TwinBy, for example, is planning to produce 18 urban digital twins in Bavaria alone by March 2024. The concept of digital twins actually emerged quite a few years ago thanks to the growing possibilities afforded by digitalization and data collection. A digital twin is intended to be a representation of a structure that exists in the physical world. This makes it possible to run simulations of various adjustments, and it also reveals dependencies between various organizations at a glance.
Avoiding redundant data storage whenever possible
In this process, there are all sorts of obstacles to overcome because, in the past, data in cities was often stored in insular solutions. Utility companies rarely collaborated with urban planning departments, for instance. One major challenge is the lack of the necessary interfaces. This is why the Bavarian State Ministry for Digital Affairs has worked with the Technical University of Munich within the TwinBy project to produce a guide that municipalities can use as orientation. The document's 80-plus pages describe the process using the concept of Smart Data District Infrastructure (SDDI). The aim of SDDI is to link platforms together using open, standardized interfaces. This is meant to improve interoperability between the various stakeholders and prevent any redundant data storage. After all, creating a digital twin is a difficult undertaking that needs support. Municipalities therefore often work together with external service providers from the field of data collection. The digital twin acts as a foundation for a cross-sector data structure and as an application-oriented link that connects existing models, data, sensors and their use in complex planning scenarios.
Benefits for smaller towns, too
It's not just major cities that can benefit from guidelines such as the one provided by TwinBy. This past spring, a digital twin was also presented in Forchheim, a district town with 34,000 inhabitants about 30 kilometers north of Nuremberg. Its twin is now freely accessible to its citizens. The town worked with RIWA GmbH, a service provider that deals in digital geodata collection. The digital twin now shows users its tree register, parking lots, playgrounds, vacant buildings and more. Even approved construction plans are stored in it. “We've been tasked with creating an organized data infrastructure that also incorporates all the relevant authorities,” explains Matthias Hoffmann, who is responsible for Forchheim's digital twin. Like Nuremberg, Forchheim faced the challenge of having several different data silos that didn't allow for any interchange. The digital twin now provides exactly that: All sorts of authorities – from the parks and gardens department to municipal management – can access the platform and exchange their data.