For a digital platform of the sustainable city

This article includes some proposals from the book "Inventing sustainable cities" (Ed. Dunod, 2022), in which we review the horizons of sustainable cities and the conditions to be met to build them in a broader and more efficient way.

For those involved in urban design, the sustainable city presents several difficulties. Its multiple dimensions mean that a large number of heterogeneous data must be taken into account, relating to the contexts in which a project is inserted, its carbon footprint and the building itself. The other difficulty relates to the fact that the sustainable city is seen as a system. As each project generates externalities on its environment, it is important to anticipate them and measure them ex-post. In order to respond to these difficulties, software and the algorithms that underlie it are essential tools for integrating more parameters into the project, and for playing with these parameters in order to reach an optimum. All the actors in the sustainable city have already adopted these tools, to the point that some people are now celebrating the advent of algorithmic urbanism.

However, this increase in skills has been rapid and empirical. The questions concerning the availability and governance of data, and the methods of use of software in relation to local authorities, have not yet been clearly resolved. This would be necessary, however, to ensure that the sustainable city is built and managed efficiently, under transparent and homogeneous conditions.

Open data to establish a clear and exhaustive diagnosis

Some French cities are creating the conditions for open data sharing and exploitation. The city of Rennes was one of the first in France to commit to an open data approach in 2010. Today, its Rennes Métropole en Accès Libre platform references an impressive amount of data, rendered in a simple or advanced way, depending on the use one wishes to make of it. It also publishes Baro'métropole, which is a control panel that allows all citizens to follow key indicators on mobility, housing, the environment, employment and solidarity. This tool shows a great concern for transparency, but also the capacity of sustainable cities to involve citizens in their evolution in a precise and transparent way.

In parallel with these actions, the city has set up a metropolitan public data service. Designed as a laboratory for experimentation, it is intended to use data to develop new digital applications. In addition to working to create digital public services, this structure guarantees the availability and interoperability of data. It also guarantees that personal data is processed in accordance with the law. Finally, with the help of Dassault, the Metropolis has developed the 3DExperience platform, which aims to virtualize the city, including all relevant data, to create a sort of virtual sandbox for simulating, planning and managing the city. In this way, the city can simulate the impact of a project on mobility, the appearance of heat islands or even rainwater management.

Other cities are pioneers, such as Saint-Étienne, which operates a digital platform for urban public data. Its ambition is to facilitate the daily use of the people of Saint Etienne and improve their quality of life in the city. This platform is an open, scalable and replicable urban management tool that, on demand, analyzes, produces and makes available to users a variety of urban data on quality of life, mobility, public services, infrastructure, etc.

Rennes and Saint-Étienne are very comprehensive examples of how the sustainable city will manage its data: openly, responsibly, with the opportunity to link it to interoperable digital public services, and by ensuring that it supports informed public policy through modeling tools. It is interesting to note the extent to which the cities - in these examples - have evolved both their organization (with the creation of separate departments), their working methods (with the creation of experimental digital services within it), and finally their skills to manage subjects that a priori relate to areas far removed from the public service, but which ultimately directly determine the definition and implementation of public policies.

Such an approach would benefit from being extended and systematized elsewhere. However, not all local authorities have the financial or technical resources or the human resources to implement such systems. To address this problem, pioneering cities are working through Open Data France to create tools to manage data in a standardized way (local or national) and to return it in the form of a platform. Dataclic - that's its name - is available to cities wishing to set up such a platform.

Outline and modalities of a digital platform for the sustainable city

In its making, the sustainable city relies on at least two guiding principles: the modeling of desirable development scenarios, which serves to transform the city; and the constant measurement (upstream, during construction and downstream) of the data inherent to sustainability (environment, health, sobriety, resilience).

Modeling is made possible by increasingly sophisticated software, which - by dynamically integrating a large amount of data - makes it possible to anticipate an equally large number of externalities. These software programs make it possible to analyze and quantify the life cycle of a building, to identify the different scenarios for redeveloping a heat island, or to strengthen biodiversity in a neighborhood by taking into account the different webs. Some, even more powerful, propose to simulate the functioning of entire neighborhoods, as was the case, for example, in the Lumières Pleyel neighborhood in Saint-Denis. The challenge for École des Ponts ParisTech was to assess the environmental impacts of mobility practices and to draw the consequences in terms of development to improve the environmental performance of the neighborhood.

This software is transforming urban planning. But this revolution has several limitations. On the one hand, the software market remains opaque and fragmented. Cities therefore do not have a global vision of the software available to enable their service providers to work efficiently, or at least they only have an overview through occasional calls for tender. Secondly, these applications are rarely compatible with each other, even though thinking about the sustainable city implies thinking in terms of systems and therefore linking data and applications. Finally, these applications are private and their algorithms are rarely intelligible to administrations that are unable to understand how they work, let alone correct any bias and make them evolve.

Solving these problems requires the implementation of several projects.

• The opening and standardization of data: data relating to the public space must remain public and be standardized, to facilitate both their aggregation, processing and restitution by the authorities. Open Data France makes this possible, through tools that are already available. It remains to extend and systematize the approach, by creating in each city departments responsible for data processing. Without access to exhaustive and accurate data, the city will remain blind and will not have the necessary indicators to move in the right direction.
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• Encourage software interoperability by promoting standards in terms of protocols and formats to allow different applications to interact and formulate more coherent simulations. This compatibility is the sine qua non that allows the design of coherent projects, in a context that is understood in its entirety. It could, in the same way as the quality of the input data and the transparency of the algorithms used, be a condition for obtaining a label awarded by the Ministry of Energy Transition or other ministries depending on the field of application of the software.
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• The creation and promotion of open source applications, in the form of commons, designed and maintained by research laboratories. Such applications would include open algorithms, which cities could capitalize on as projects arise. These applications would be subsidized by ADEME, which already contributes to the production of commons, particularly in the area of resilience.

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This approach to producing common ground would benefit from being extended to methodologies along the lines of what Energie Sprong prescribes for energy renovations or Ready2Services for intelligent buildings. These methodologies help to massify sectoral approaches and to train personnel involved in the transformation of their profession through concrete projects. As Sébastien Delpont rightly points out, they enable us to move from a "project culture", where everything is made to measure, to a "product culture" with customizable off-the-shelf solutions.

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• Make the software market more transparent, through the creation of an app store to move towards a clearer market and allow cities to solicit the relevant players from the start. Such an app store could be the subject of a prototype, designed by BetaGouv in conjunction with the Ministry of Territorial Cohesion.
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• To enable local authorities to manage an archive of digital twins and, more generally, to facilitate the use of modelled files at all scales of the city. As Laurent Vigneau points out, "the dynamic digital twin organizes the intervention of future actors from an initial reasoning that conceptualizes the entire life cycle of the urban object. It allows us to move from life cycle analysis to life cycle management, itself organized on the basis of initial objectives and strategies that can be found at any time. (...) It allows us to monitor performance in terms of carbon footprint, resources, circular economy, permeability, biodiversity and heat. It is therefore easy to understand how crucial the archiving of these files is. Applied to biodiversity, such a database would, for example, make available all available files from design offices or landscape architects on blue, green or black grids, to enable new projects to preserve or enhance biodiversity.

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These proposals imply that cities must take on new functions and acquire new skills. The NGO C40, which brings together a hundred international metropolises, believes that each city must strengthen its skills and resources in terms of data governance and information systems to be able to effectively manage its sustainability strategy.

Of course, these initiatives present a significant cost of change in terms of organization and skills. They also represent significant investments. The Digital Transformation of Local Authorities fund allocated in 2021 as part of France Relance could help local authorities to transform themselves. Axis 2 of this program is precisely dedicated to the conduct of large-scale projects at the level of a metropolitan area, region or department, but it is feared that with no less than 75 projects aided, for average aid of 180,000 euros, this scattering strategy struggles to take the measure of the challenges. It poses at least three problems: it assumes that a project conceived as a local prototype can potentially be taken up at the national level, even though neither its functionalities nor its technical architecture have been designed to be replicated on a larger scale. It also implies that communities can either assume the responsibility of designing these applications or delegate it to third parties who have no interest in producing commons, and do not have the overall vision to ensure that they will be suitable for several communities. Finally, this strategy aims to develop projects on an ad hoc basis, even though it is necessary to smooth out these budgets over time. The challenge is not only to design applications, but to create businesses and organizations around them, and to make them evolve in parallel.

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Complete book available here (in french): Inventing Sustainable Cities: Ideas and Tools to Meet Today's Challenges (Matthieu Chéreau & Maxime Guillaud)