It has long withstood the mad growth of road traffic, struggling as best it could against the weight of trucks and years. Built in 1867 for the Universal Exhibition in Paris, the Port de Roche bridge has linked the towns of Langon and Sainte-Anne-sur-Vilaine between Rennes and Nantes for one hundred and fifty years. The problem is that the work is now tired and needs to rest. During a recent audit, the experts revealed a significant pathology of the metal structure which raises fears of a complete collapse of the famous bridge crossing the Vilaine. To limit the risk, the department of Ille-et-Vilaine had prohibited the crossing to vehicles of more than 20 tons in 2020. The deterioration of the situation even pushed it to lower this ban to 3.5 tonne vehicles. In force since February 11, the decree was first respected… Before being defied several times. “A real danger”, according to the department, which issues a warning.
According to the community, “violations of this new crossing rule are regularly observed”. “This new limitation makes it possible to maintain the condition of the bridge, and to reduce the risk of potential ruin of the structure. As a result, no exemption is granted for passage over the structure, ”recalls the department of Ille-et-Vilaine. The installation of a gate is under study, as well as the possibility of a temporary crossing.
Erected in the 19th century, the Napoleon III bridge initially featured multiple metal arches 25 meters long and 21 meters wide. “It was then dismantled and reused locally to form three spans of 25 meters, founded on masonry supports”, recalls the department which insists on the heritage value of the building. Under study, the complete renovation of the bridge “will only see the light of day in five or ten years”, recognizes the department. Compensation could be granted to professionals and agricultural cooperatives in the sector who have to make major detours to Redon or Guipry-Messac to cross the river.