Land Transport Infrastructures, Ecosystems and Landscapes

Cergy-Pontoise (english)

Projet: Recherche



Rapport final



Road infrastructures, landscapes and ecosystems
Methodological research based on road projects in progress on Cergy-Pontoise civil parish territory : Join for an update and innovative project the provision of knowledge, social demand from stake-holders, impacts assessment and the search for sustainable urban planning.

Responsable scientifique

Ann-Caroll WERQUIN
wthales [at]
Atelier Thalès


Atelier d’environnement Thalès : Ann Caroll Werquin, Alain Demangeon

Cergy-Pontoise, L’agglomération : Luc Raimbault, Joseph Salamon,

Urban-Eco consultancy (Marine Linglart-Lime), Agnès Barbieri.

J. Jonkhof et S. Tjallingii, Ecology and urban planning, (The Netherlands).

Hervé Mineau (PH doctor in Ecology).



With the Research are questioned how renew the making of bypasses and motorways at the cities edges, what are the actual requirements for bringing some change in manufacturing the roads for fast point-to-point connections, and how acquired knowledge relating ecosystems and corridors allowing the movement of plants and animals is valued. Underlain assumption stipulates innovative achievements occurred these last decades contributing, in the field of roads, by their forms to the respect for townspeople environment, ecosystems and landscapes. The diversity of the explored ways, the multiform character of answers and the importance of local features within (even when a national policy is on), the low cognition about these very recent experiments, make the renewal still not being much met in French decision-makers practices delivered on the ground.

Research aims at gathering these examples and skills and introduces them by performing an inventory in numerous countries. It throws into relief items allowing innovation and hybridization between forms of express ways and environments to serve subjacent common aim of sustainable and congenial built-up areas.


Two types of analysis were conducted through inquiries, pictures reports and experts' opinions. On the one hand was deeply studied the Cergy-Pontoise metropolitan district, a large scope of land dealing with motorways projects, delineated with informed analysis in several respects. Authorities of Cergy-Pontoise are directly interested by meaning-making processes touching roads and worked as partner for the Research. The report contains an appraisal of road-projects, seen in their specific impacts and elements of a state of art concerning the Ile-de-Francecontext and bringing to light advances relating some of its express ways. The second and parallel task was about location, identification and description of innovative examples of thoroughfare roads in France and abroad.

Main issues 

Roads call forth new attitudes, carried by question setting on resources and climate, on the « Grenelle de l’Environnement », on the challenge of physical nuisances (noise, pollutions, disruptions) and that of disorder and impoverishment of the neighbouring places not much compatible with a bearable and more compact city. Lifestyle preoccupation nourishes a rather obvious change of paradigm and problems put forward by the townspeople are now receiving proposals to resolve.

But, with regard to the overall results, examples able to link improvements to secure ecosystems, a downside of impacts on urban planning and better respect for landscapes, are few. However all together cases in hand show manners of integrative approaches, a major wealth-driven trend for the built-up areas, reconnection of remnants of habitat, enhancement of habitat corridors and natural processes, meanwhile the road-project remains alike or changes. To turn the motorway-plan or the increase of its capacity fitting with the life of the townspeople and nature, to prevent the reduction of the natural network or ensure the future of a weak territory, cogitation touch the form and all the parameters of the road, thinks of areas of transition, generous compensation and creates a dialogue with landscapes. A significant role is devoted to multiform roads, putting together stretches conceived each one as a local answer to questions.

Interventions are precautionary or of repairing. They add qualities to the neighbourhood, restore the social interplay inherent part of the street and the public promenade functions, consider the passer-by and the cyclist‘s scale, and look at green structures as powerful features. The traffic speed and the capacity lose their priority, the road-profile moves, soil is less consumed and given to the public realm, programs include issues difficult to set up otherwise (examples in Netherlands, Italy, Germany, United States, in Scandinavian countries and in France).Examples from Barcelona (Gran Via, Plaza Cerda) and from the Swiss policy against fragmentation, show that, upon special conditions, injuries resulting from the road presence can be mitigated or even suppressed.

More than other French regions, Ile-de-France contains examples crossing the borders, such as A 14 or, for some of its parts or a certain amount of applied requirements, A86. Cogitation led on Cergy-Pontoise also develops such inventive point of seeing, notably with the plan of the west by-pass, withdrawn to a great extent because considered incompatible with the Green city formulated in the Unitary Development Plan.

Two small segments transform it root and branch, one is accomplished as a small country road and the other will become an "ecoroad", according to a program studied with environmentalists and planed with aldermen and inhabitants. It will put together reduced traffic lanes, a protected wild fauna corridor and noticeable improvements to environmental regeneration. This shift would not have been able to take place without the environmental knowledge gathered these last years by the Cergy-Pontoise District and its taking into account by decision-making authorities.

Practical accompaniment 

In innovative delaminated examples more is done to co-ordinate the work of the vast range of bodies locally involved in the City projects ; urban planners get a stronger role, being even at the head of the road groundwork project. Ecologists consultancies and other experts streamline the debates and course of plan and influence sustainable and updated planning. A more broadly based approach is being investigated, following critical issues on how to deal with infrastructures. Plan is not decelerated out of necessity because it avoids burden of an unwished project blocked on lasting decades. The financial capacity allowed also shows a change of mind. The projects are properly funded, and with their reinforced envelope several latent questions or objectives of future are treated. The road is then becoming, in the outskirts of cities, one of the elements of an improved built-up neighbourhood, almost even the step for upgrading the liveability, in spite of being the disturbing one, the element to be afraid of.

Problems faced 

To put together a set of innovative examples was a heavy task in investigations,leavingfew place to fulfil a great many homogeneousinformation given within the case studies’ statements, inasmuch as it was also important to give some insight on the especially interesting Cergy-Pontoise’s case.Hence, according to the diversity of examples, it seemed preferable to work deliberately out the value of each example, to set quality targets for new roads, introduce items of cogitation, eschew details and letting researchers fine-tune by themselves further inquiries according to their own interest.

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