The roofs of two key Brussels tunnels located on Avenue Louise will be reinforced this summer to guarantee the safety of road users, which will result in capacity in the tunnels being limited until 2027.
The Bailli and Vleurgat tunnels connecting the centre of the city to Bois de la Cambre in the southeast of the city are the only ones in the region that were built using a specific technique, namely a particularly thin roof plate, of which the stability is ensured by the tension of prestressing cables.
Analyses, diagnoses and stability studies carried out since 2017 revealed that several of the roofs' cables were showing signs of corrosion. The latest inspections in 2022 showed that the condition of the roofs is worsening, Brussels Mobility announced on Thursday.
"Without action, this means a potential medium-term risk to road user safety, with the possibility of a sudden rupture of part of the roof," Brussels Mobility noted in a statement, adding that it does not want to take any risk.
"We will therefore reinforce the tunnel roof from the inside this summer by installing struts" which will reinforce the roof from the inside. The disadvantage of this solution is that the tunnel's capacity will be limited. "Unfortunately, there is no other option that is quick and easy to implement."
What will the impact be?
Some 17,600 cars pass through the tunnels towards the centre on a daily basis, while some 16,500 drivers use it in the direction of Bois de la Cambre. In the morning rush hour, the use peaks with 1,550 vehicles per hour towards the centre, while during the evening rush hour, some 1,500 vehicles per hour drive through the tunnel in the direction of Bois de la Cambre.
The works will be carried out in July and August, when the tunnels are slightly less busy, and will be phased and spread over several weeks to maintain appropriate traffic capacity in each direction of travel.
During the first phase, which will last for one month, the roof of the tunnel shaft towards Bois de la Cambre will be reinforced. In the tunnel shaft towards the centre, the structure will be adapted to provide one lane in each direction, with one going towards the centre and the other towards Bois de la Cambre.
The second phase will see the same happen to the roof in the tunnel shaft in the other direction. Traffic toward Brussels' green lung will once again be possible in the tunnel shaft in this direction, but its capacity will remain limited to a single lane. Meanwhile, traffic towards the centre will be diverted above ground via a layout of a temporary road on the parking lane next to the tunnels.
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After this, the capacity in both directions will be limited to one lane. Numerous measures will be taken to maximise the flow of local traffic (cars, cyclists, pedestrians) in the zone and guarantee the safety of all road users.
Brussels Mobility stressed this reinforcement with struts is an interim solution, and that it is starting the procedure for the complete renovation of the tunnels so that a full renovation can start in 2027.