In the case of a twin-tube tunnel, would the ancillary structures towards the centre and the Clamart station be removed?

The twin-tube solution is a food for thought. It has not been confirmed at this stage: discussions are underway on this subject with the emergency services and the State services.

The twin-tube solution would potentially make it possible to avoid the regulatory obligation to propose a structure for emergency access to the tunnel every 800m (subject to confirmation by the emergency services and the State) since in the event of an incident in one of the two tubes, users could be brought to safety in the healthy tube via connecting branches located every 250m maximum. It would then be possible to remove the ancillary structures located in the Bois de Clamart and between the city centre and the station.

However, if the distance between two stations exceeds 1,600m (for example between "Mairie" and "Gare" if the "Centre" station is removed), a structure with surface emergence remains necessary to ensure ventilation of the tunnel.

It should be noted that an ancillary structure requires less space and is less expensive to build than a station.