A variant of a previous project for a safety tunnel, the construction of a second Frejus tunnel parallel to the existing structure (at a distance of about 50 m) was approved in two phases, between 2009 and 2012. The new Frejus tunnel project involves construction of a twin-tube tunnel with one lane in each direction. The transformation from safety tunnel to transit tunnel has not affected the location of the project or the dimensions of the section either for excavation or for use.
The adjustments made to the design of the safety tunnel to permit traffic transit are as follows:
→ modification of the ventilation system to ensure the required air flow rate;
→ new GTC for integrated management of the two tunnels from the inspection site;
→ implementation of traffic equipment inside the tunnel;
→ enlargement of the technical stations to house additional equipment;
→ creation of new filter rooms for each shelter alongside the new tunnel;
→ four additional bypasses, taking the total to nine;
→ review and upgrade of vertical signs and horizontal lateral illumination for both tubes.