In Grenoble, the widening of the A480 wants to break the lock of traffic jams (and the brake on attractiveness)

It was the construction site of the last decades for the Grenoble Y, which will have given rise to sometimes stormy discussions between supporters of a ring road remaining with 2 lanes but congested at rush hour, and defenders of an enlargement to 3 lanes of the ‘A480. Because it is ultimately this road infrastructure, inherited from the 1968 Olympic Games, which had made Grenoble one of the most congested cities in France.

From now on, it is the whole face of a road development in two parts which is about to be completely transformed, with the delivery, mid-July, of the first portion of the widening to three lanes of the A480, included on the southern part between the Martyrs diffuser and the Rondeau interchange. The northern part of this widening, which includes crossing the Isère viaduct to the Martyrs distributor, with the connection to the A480, will be finalized in the autumn.

And the first trial by fire of this long-standing project took place at the beginning of September, even though an increase in traffic was expected on the occasion of the start of the school year. “The first feedback we have from traffic has been quite good since the opening of the first section.“, confirmed at the start of the school year Olivier Ehrsam, president of the Territorial Commission of the Grenoble CCI.

With a stated objective by the end of the works: to be able to ensure a journey time of 12 minutes between Saint-Egrève and Pont-de-Claix, where the average (very scalable depending on congestion) was set at 35 minutes .

“It was even considered an almost impossible goal to achieve”

“This is one of the most important projects that the metropolis has seen in recent decades, and which was even considered an almost impossible objective to achieve, because it had already been several decades since the road infrastructures of Grenoble had become obsolete and unsuitable.The subject had mobilized business leaders in a very strong way, with a major campaign Stop traffic jams during the previous mandate“, remembers the PS president of Grenoble Alpes Métropole, Christophe Ferrari.

“One of the objectives of this project was to see how to generate less traffic inside the heart of the city, with the idea that the A480 could once again play its role by once again becoming this structuring axis which makes it possible to calm traffic on the other axes”, displays Nicolas Orset, director of operations in the infrastructure department of APRR-AREA.

The one recalls that “this multi-faceted file, which was thought up in 2016, has even become a reference within the group of what can be done in terms of urban development, in order to combine the issues of mobility and transition today energy”.

Because with traffic estimated at nearly 100,000 vehicles per day, the A480 was the epicenter of road congestion, linking the city of Grenoble to traffic from Lyon and Valence. Firstlyand on the other to the historic Rondeau interchange, serving the entire south of the conurbation (in the direction of Gap and Chambéry).

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Despite strong reluctance mentioned from the start of the project concerning the possibility of making it “a car vacuum cleaner” while breaking “the lock of Grenoble traffic jams”, this project had finally been the subject in November 2016, of a memorandum of understanding between the State, the local authorities (Grenoble Alpes Métropole and the Department of Isère) and the motorway operator AREA. “This project was designed not to increase transit traffic“, recalls Christophe Ferrari.

Two envelopes of 300 million and 100 million euros

A project which actually comprises two parts, since the tripling of the A480 lanes, carried out with a commitment not to widen the motorway right-of-way itself, is 100% financed by the company AREA (which obtained in parallel an extension of its concession on the A480 until 2036 to finance the works, estimated at 300 million euros). While the facelift of the Rondeau interchange (100 million euros in total) will be supported by local authorities (State, Grenoble-Alpes-Métropole, Department of Isère, Auvergne-Rhône-Alpes Region) with an inscription the State-Region plan contract (CPER) 2015-2020.

Faced with the opposition of groups of citizens, defenders of the environment as well as the unfavorable opinion of the mayor EELV Eric Piolle (who had already considered “that using a huge effort of public money for road improvements everywhere in France, it was not what we wanted”editor’s note), seeing in this enlargement a call for air to accommodate even more traffic and therefore pollution, the file had also had to show a white leg, or rather a green leg.

In particular, the site had to multiply the eco-commitments: creation of two footbridges dedicated to cycles and pedestrians, speed limit to 70 km/h on the main portion, installation of higher acoustic screens over a length of 6 km, replanting of 50,000 trees, creation of wastewater retention basins so that they are not returned to the Drac, etc…

On the calendar side, the work had started in the spring of 2019, following the public inquiry launched in July 2018 and will be spread over three years for the widening of the A480, led by AREA. At the same time, work to redevelop the Rondeau strategic interchange has begun, under State supervision. this timewith commissioning scheduled for mid-2024.

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An element that weighed on the attractiveness of Grenoble

“This project involves several challenges, starting with the development of the territory in an area which was completely saturated in terms of mobility and which weighed on the attractiveness and competitiveness of the Grenoble basin, even though this metropolis remains very dynamic from an economic point of view”, observes Nicolas Orset.

With its 49 municipalities and 450,000 inhabitants, the Grenoble metropolitan area is the 2th French research center but also as a mini-silicon Valley with a large number of key players in the microelectronics sector (STMicroelectronics, Soitec, Aledia, Lynred, etc.) and more broadly in new technologies (Verkor, Schneider Electric, HRS, Air liquid, etc.).

On this occasion, a new exit was notably created in the very heart of the Grenoble scientific peninsula, so that the some 20,000 employees of the district (which notably includes the CEA, but also many companies in the new technologies sector such as STMicroelectronics as well as that the new head office of Crédit Agricole Sud Rhône-Alpes) can benefit from new direct access to the A480, making it possible to free up the central avenue des Martyrs.

“This project will give us additional attractiveness, particularly in the southern branch of the Grenoble conurbation, by allowing both to better connect the different points of the metropolis, but also to participate in the development of new areas of attractiveness located in the south of the conurbation,” said Christophe Ferrari.

Same expectation on the side of the CCI of Grenoble, where Olivier Ehrsam, president of the Commission of the territory of the CCI of Grenoble, notes that many Grenoble companies “were unable to recruit because of the mobility lock. If you had to go from Saint-Egrève to Seyssins and spend 50 minutes in the car in the morning for a journey that is only 13 kilometers long, it became complicated. We also had companies that no longer wanted to set up in the Grenoble area, for lack of available or accessible land, and which migrated to Bourgoin-Jallieu or Chambéry…

Not to mention “business leaders who no longer even came to Grenoble” according to him, and “preferred to meet employees of large companies in the Grenoble area in a lounge at Lyon-Saint Exupéry airport…”

The next steps

It now remains for this project to pass several fire tests: the delivery, first of all of its complete system, including the complex Rondeau interchange, the facelift of which will be the responsibility of the local authorities, and which will have to fluidify and absorb the flows coming from four different directions.


Also with feedback to be carried out on the evolution of traffic:

“The modeling that was done 10 years ago on the occasion of the North ring road project, since buried (and which assessed several scenarios including that of a simple widening of the A480 without North ring road, editor’s note) estimated that we would reach 150,000 vehicles per day …”, recalls Emmanuel Colin de Verdière, president of the ADTC Grenoble association.

The association, which claims a thousand members, opposed this project, considering that it was not one of the priorities: “for 300 million euros, we could have done much more for public transport and soft mobility“, valorize Emmanuel Colin de Verdiere.

On the side of the CCI, which firmly supports the file, we slip however that on the traffic side, “everything will also depend on post-covid practices, because it is difficult to know precisely what the state of play has been since the health crisis, while a large part of companies still offer teleworking devices”added Olivier Ehrsam.

On the side of AREA, it is specified that a first quantified assessment, and in particular of road congestion, is expected for the end of October.

The setting to music of the next stages of the Grenoble ZFE could also influence the evolution of future traffic over the next few years, even if the A480 is at this stage excluded from the perimeter, where the Crit’air sticker will be compulsory.

For its part, the Metropolis of Grenoble is also betting, through its public transport union (SMMAG), on the continued development of public transport on the scale of the next mandate, which includes in particular a project for a future cable car linking the at one end of the Grenoble Y, from the town of Fontaine to Saint-Martin le Vinoux, via the Presqu’île. And more broadly, in the long term, its Grenoble RER project at 1 billion euros, the financing of which has not yet been completed but which aims to redevelop a network of daily trains every 15 minutes, by 2035.