The western bypass of Montpellier is moving forward… so are the arguments against the project

Une 2×8 voies saturée aux États-Unis, l’exemple des universitaires pour décrire “le trafic induit et la loi de Zahavi”. L.T.

The prefect of Hérault has received the request for a public environmental inquiry, the last act before the start of work on the Com Ouest de Montpellier. But the debate is far from over. Illustration.

Will 2025 mark the final administrative stage before the launch of the Montpellier Western Bypass project? ? Twenty years after the first phase of consultation, the Prefect of Hérault, François-Xavier Lauch, indicated that he had received “the environmental authorization application file submitted by Vinci at the end of 2024”.

If it is validated by the National Council for the Protection of Nature and the Environmental Authority, the State representative will be able to officially authorize the work, “I hope at the end of the year”, he added. The work, which would begin in 2026, would then last three years. It would therefore be in 2029 that we would be able to travel on the 6 km transformed into 2×2 lanes, between the A709 in Saint-Jean-de-Védas and the A750 in Juvignac, passing through Montpellier. “This will help relieve congestion on certain axes of the metropolis”, assures the prefect of Hérault.

“A bygone culture”

Case closed ? Not so obvious. First, because the Toulouse administrative court of appeal – at the centre of all attention on the future of the A69 Toulouse-Castres – must still examine the appeal filed by the Autre Com collective against the declaration of public utility. And these opponents are far from giving up, continuing to sharpen their weapons against this project that they consider “of a past culture”.

Mathias Reymond and François Mirabel are not part of it and yet, these academics provided them with arguments, this week on the occasion of a conference organized at the Faculty of Economics of Montpellier on the theme “Should we still build roads ?” “The Com Ouest project of Montpellier illustrates this dilemma: respond to immediate needs while increasing our dependence on cars or fully commit to a sustainable transition”, asked Guilhem Vern, who initiated this debate. To ask the question in this way is to answer it in its own right, and the introduction by Mathias Reymond, lecturer in economics and specialist in transport economics, was along these lines.

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Induced traffic, urban sprawl

This first showed a photo of an American highway, a totally saturated 2×8 lane. “It was first a 2×2 lane, but faced with its congestion, it was decided to make it a 2×3 lane. Then a 2×4 lane… and so on up to 2×8 lanes, always with the same effect very quickly”, described the specialist. “In the short term, it's true, there is a reduction in congestion, and therefore in travel time, but in the medium and longer term, we see negative effects everywhere, starting with urban sprawl. It's Zahavi's law: when travel speed increases thanks to smoother routes, people will live further away. There is also induced traffic that is created: widening a road attracts latent demand from other routes, and therefore congestion, too, on adjacent routes”, summarized Mathias Reymond, after having recounted the history of an all-road policy, “the legacy of Pompidou who believed that the city had to be adapted to the car”.

A strategy of sobriety

This paradigm has changed, however, as his colleague François Mirabel, also a specialist in transport economics, pointed out. “From now on, we are aiming for 2050, the objective of zero net emissions (of CO2, Editor's note), zero net artificialization… A strategy of sobriety that is based on both a technological lever, that is to say for the transport of vehicles that emit less CO2, and a behavioral, societal lever. All the scenarios are based on these two bets […] The infrastructure orientation council, in 2022, thus noted that the urban bypasses, even if they meet strong local expectations, must be reexamined in view of the search for sobriety”, he relayed.

However, in the process, Hugo Arnichand, co-delegate of Shifters Languedoc-Roussillon, dismantled the climate impact study of the Com Ouest, “in which the induced traffic was not taken into account. In fact, Vinci, considering that the work would bring a time saving of 3%, presented a project that would reduce CO2 emissions. Our study rather estimates an increase of 250,000 to 450,000 tonnes of CO2 equivalent”, he argued. Among other things…

“The true face of Com”

A godsend for Céline Scornavacca, representative of the Autrecom collective, who was then able to outline her angles of attack: “urban sprawl, which we have already seen to the north of Montpellier with the A750, has not been taken into account; the planned park and ride facilities are undersized compared to the induced traffic that the Com will generate; over 1 km, the project does not provide for 4 lanes but 10, with those for local traffic or buses; Vinci is talking about a light renovation of a road that already exists, but the change in semantics around this project shows that its aim is not to relieve local traffic but to create, by creating new, impactful engineering structures, the missing link between two motorways to create a new axis (towards the A75) and thus relieve congestion in the Rhône Valley”, she listed, asking decision-makers “to reveal the true face of Com”.

The debate is far from over. The A69 has also demonstrated that it can continue even when the work has begun.

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