With the prospect of defining the qualities, philosophy and design method common to the 68 public spaces of the stations of the new Grand Paris Express Metro, this study, carried out by a multidisciplinary team led by TVK, is an opportunity to conduct research on the public space in Greater Paris. Nearly 20% of the Île-de-France's ground surface area is public space. This shared ground is a repository for both past history and future civilization issues. It constitutes an essential common good, a support for travel and meeting in the metropolis.

Its development must be built on a common culture, which articulates a reflection on the ground with a reflection on time. Thinking each new project in these two dimensions, spatial and temporal, will guarantee the inalienable character of public space as well as its capacity to respond to the social and ecological challenges of tomorrow.

The ground as a project

The ground is not only a surface area, to be looked at solely in plan view. It constitutes a thickness, spread between depth and the sky and composed of several interacting layers: the subsoil, the surface and the atmosphere. It forms a global environment in which human uses and activities take place, the nature and quality of which it conditions.

Therefore, the issue is that of considering its design conception as an architectural project in its own right: an act of drawing and mastery, which combines and moulds different elements – networks, materials, vegetation, climate, etc – supporting a stronger habitability. Let us contribute to making it a comfortable environment, propitious to human activities, by paying specific attention to its materiality, its robustness, the quality and the simplicity of its implementation.

Time as a resource

Progression, successive reinterventions, forecasts, anticipations, assumptions, acceleration effects or, on the contrary, slowed paces: the time of the public space project is complex, infrequently homogeneous or linear. The temporalities of public space also go along those of ecology and climate. Locating it in a perspective of sustainability implies taking into account the rhythms of the living and natural cycles.

In order for the public space to be in touch with the evolution of the territory, we propose to consider time not as a constraint but on the contrary as the main material of a reflection on the ground: the time which precedes the project, the one which succeeds it, but also the one which composes it. A more progressive approach will thus be adopted, by incorporating actions into the project design that could precede or accompany the building site. These actions are not "temporary" but an integral part of a gradual transformation of the site.

Continuity, evolvability, availability

There is no single solution to the diversity of situations and the extent of development schedules, but rather values to be shared. Guiding the design conception of the 68 public spaces hinges on the formulation of three major ambitions for future public spaces: their continuity, evolvability and availability.

The continuity relies upon on the recognition and amplification of everything that pre-exists and surrounds the project, which is an opportunity to produce or consolidate the links between the urban designs (existing, current or future) and their contexts. The establishing of continuity in the urban landscapes does not mean their standardisation but the enhancement of their sequencing, thresholds and concatenations.

Public space is the long-term repository of the city, and its sustainability is directly linked to its evolvability. This implies the designing of projects that will have to adapt to changes and the unforeseeable. Evolvability is based on the dissociation of the permanent and the temporary: the ground must be able to last while admitting that its facilities may change.

The availability relies on the fundamental vocation of public space: ensuring equal access to the city and to urban resources. It involves making places open, welcoming and manifest to everyone, without this meaning that everything is allowed, and hinges on the capacity of spaces to create a coexistence of uses and functions.

These three major ambitions guide 40 design principles for public space projects. Proposals and objectives more than pre-established recipes, these principles invite the sharing of a project-approach, and their implementation is left to the discretion of the designers and project owners.

The result of a three-year study carried out by a multidisciplinary team led by TVK, the book Places du Grand Paris is a guide to the design of public spaces in Greater Paris which aspires to contribute to the construction of a common culture of public spaces. It was developed for the attention of the project owners and designers of the public spaces of the 68 future stations of the Grand Paris Express, in order to support them in the monitoring, programming, design and management of their public spaces. This common culture relies on the conviction that public space must be conceived in its multiple dimensions, both in the thickness of its ground and in the depth of its temporalities.

To communicate in an open and inclusive way the elements of this culture, the work articulates practical as well as theoretical statements, around a varied iconographic corpus (drawings, photographs, models, documents, maps) conveying public space as an imaginary and evolving field of experimentation.