Cofiroute's 10.4m internal diameter tunnel allows for two road decks for cars and light vehicles, each 2.55m high.
There is space for an adult to stand with room above for electronic surveillance cameras and lighting. Each deck has two full car lanes and an emergency vehicle lane/hard shoulder.
Above or below are ducts for transverse ventilation, independent for each deck.
Vertical ventilation shafts, which also act as escape routes, are spaced every 1,200m.
Traffic will be monitored by automatic TV and slow vehicle detectors every 100m and 'red cable' fire temperature sensors. Lane allocation lights will be sited every 200m and verbal warning display boards every 400m.
Passengers can escape at refuges connecting to the other deck every 200m.
Lorries and trucks will run in the separate, full height West Tunnel, routed further out of Paris. But this has been held up by the government to allow consideration of its safety provisions.