The Mont Blanc Tunnel will be entirely shut to traffic for around fifteen weeks, from 5.00 pm on Monday 1 September 2025 until 5.00 pm on Friday 12 December 2025. The closure was announced on 19 May 2025 by the binational operator Tmb-Geie, which explained that the extended interruption is necessary to carry out the second trial worksite for restoring the tunnel vault. Following the 2024 intervention, the new project will involve 254 metres of the tunnel ceiling, located just upstream and downstream of a section already renovated last year. The works will include the complete demolition and reconstruction of this segment, using the same techniques tested in the previous operation.
The nature of the works requires the removal of all safety devices fixed to the tunnel ceiling, such as fans, cameras and temperature sensors. This makes it impossible to arrange partial closures or limit traffic during specific hours, meaning the tunnel must remain entirely closed for the full duration of the project. It is a delicate and complex operation, forming part of a wider plan to modernise the infrastructure, which was inaugurated over sixty years ago, and which involves a total investment of 50 million euros.
The chosen timeframe is no coincidence. Autumn sees the lowest flow of light vehicles, which accounted for 75% of the tunnel’s total traffic in 2024. Targeting this period should help limit the negative impact on tourism and the economies of the affected regions. Despite the announced schedule, the Tmb-Geie consortium has pledged to reopen the tunnel earlier if the progress of works allows. Italian and French authorities will be kept constantly informed about the site’s developments.
During the closure, most industrial vehicles will be rerouted through the Frejus Tunnel, which is expected to absorb around 90% of commercial traffic. Light vehicles, on the other hand, will be able to redistribute across the Grand Saint Bernard, Frejus itself, and the main Alpine passes, such as the Little Saint Bernard or the Montgenèvre, depending on the origin and destination of the journey.
To reduce inconvenience for regular users, any 10 or 20-trip subscriptions still valid on 1 September 2025 will be automatically extended by four months, with no need for holders to make a request. All information regarding the works, alternative routes and traffic conditions will be available in real time on the website tunnelmb.net and through the official Tmb Mobility app.
