A 3-storey tunnel is envisioned for İstanbul. Two storeys of the tunnel for motor vehicles one in each direction and middle storey for rail transport.

İstanbul already has a Twin-deck tunnel in operation called 'Avrasya Tüneli' (Eurasian Tunnel).  Avrasya Tüneli is the first underwater twin-deck tunnel of the world and it is 5,4 kilometers. Avrasya Tüneli connect the southern shores of the city to each other, the new tunnel will connect central part of Boğaziçi. Avrasya Tüneli is only for motor vehicles.

İstanbul's two sides connected already wıth 3 suspense bridges, one metro tunnel and one motor vehicle tunnel (Avrasya Tüneli). İstanbul is the biggest city in Turkey and new tunnel lighten the traffic. Underground public transport will have 14 stations and carry 1.500.000 passengers each day.

Turkish Tunnel Boring Machine say source

Avrasya Tüneli was bored by Herrenknecht tunnel boring machine. Sources of Ak Parti (AKP) government give information aim of Turkish state departments to use in 3-deck new tunnel a Turkish tunnel boring machine from Turkish company E-BERK. Also prefer a Turkish contractor similar to Gülermak (a tunnel construction expert company), YAPI Merkezi (partner maker of Avrasya Tüneli), Doğuş (tunnel expert), Bayburt. But they say they plan a Buılt-Operate-Transfer method. What happen if project owner decide a foreign TBM company similar to Hitachi Zosen, Herrenknecht or something else? Similar a foreign contractor Astaldi? Too many questions.

Project is vision at this time.