Construction has begun on the A412 highway in Haute-Savoie, a region in the southeastern part of France, with local opponents trying to block the project. On September 7, 2026, the first construction vehicles arrived at the site of the future highway, which will connect the towns of Machilly and Thonon-les-Bains. This 16.5 km route is part of a larger infrastructure plan called the "Chablais highway." The project, estimated to cost over 300 million euros, is being managed by Amedea, a company under the Eiffage group. Work includes clearing land and cutting down trees, which has already started. Activists from the StopA412 group have attempted to block access to a forest path in a peaceful protest, aiming to slow down the construction. The A412 highway is expected to be completed by 2029. However, opponents argue that the project is unnecessary and environmentally harmful. They criticize the decision to build a highway that would essentially double the capacity of an existing railway line, the Léman Express. The highway's construction will cover 177 hectares, including areas that are crucial habitats for species like the beaver and the poppy. Environmental groups have raised concerns about the impact on the region's wetlands and biodiversity. They argue that the highway would create a "scar" on the landscape and increase traffic and urbanization in an already densely developed area. Environmental authorities have also expressed concerns about the project. The National Council for the Protection of Nature has issued an unfavorable opinion, and the Environmental Authority has pointed out that the highway will emit 286,000 tons of CO2 equivalent over the next 20 years. This level of emissions is seen as inconsistent with national goals to reduce greenhouse gas emissions. Local associations have filed legal challenges against the project, arguing that the environmental risks are too great and that the construction should be halted until these issues are resolved. Despite these concerns, the prefectural decree authorizing the construction includes environmental commitments from the project's concessionaire. These include measures to manage noise, water, and other local impacts, as well as plans to compensate for the environmental damage by protecting more than 300 hectares of land elsewhere. However, opponents remain skeptical, arguing that these measures do not adequately address the scale of the project's environmental impact. They continue to call for the project to be reconsidered in light of the ecological and climate concerns it raises.