The new mega project in Istanbul, the "Three-level Big Istanbul Tunnel," will be first three-level tunnel in the world and will consist of both the metro line and dual motorway. The fast metro line will enable 40-minute travel from İncirli to Söğütlüçeşme and a 14-minute journey by car from Hasdal crossroads to the Ümraniye Çamlık crossroad. The tunnel, which is estimated to cost $3.5 billion, was introduced by Prime Minister Ahmet Davutoğlu and the Transportation, Maritime and Communication Minister Lütfi Elvan. The project is included in the 2023 Transportation Projection in order to find a solution to Istanbul's busy traffic. This project combined the "fast metro tunnel project," which will start from Bakırköy-İncirli in E-5 axis and reach Söğütlüçeşme, similar to the Marmaray and the "highway tunnel" with 2x2 lines similar to the Eurasia Tunnel located on the TEM highway axis in order to decrease the traffic on the Fatih Sultan Mehmet Bridge, the second bridge on the Bosporus. Instead of separate tunnels, one tunnel will be built for both metro and dual highway Bosporus crossing. The tunnel will enable faster and cheaper transportation between the two sides of Istanbul. It will integrate nine different urban train systems with a fast metro track, which is used approximately by 6.5 million passengers on a daily basis. It will also enable easier and faster connections to ring roads; thus connecting all main arterial roads."Istanbul is a city which shapes history, it deserves the best, including mega-projects" Davutoğlu said, while presenting the new project in an event organized by the Ministry of Transportation. "The three-level mega project will be the signal flare of the Turkish Republic, the fourth global state in Istanbul after three empires," he told in a publicity meeting for the "Grand Istanbul Tunnel" at Istanbul Congress Center.Speaking at the opening of the publicity meeting, Transportation, Maritime and Communications Minister Lütfi Elvan said the mega project is the product of around 10 months of intense work where they analyzed Istanbul's route profile and the demands of the passengers. Elvan emphasized that the tunnel will the raise the role of railway system in public transportation. The minister said the sub-sea tunnel will be constructed with a "build-operate-transfer model" -- a form public-private-partnership scheme -- so "the state will not pay a single penny."The tunnel will integrate local metro lines of Istanbul including Başakşehir-Bağcılar-Bakırköy Metro, Yenikapı-Aksaray-Airport Metro, Kabataş-Bağcılar Tram, Topkapı-Sultançifliği Light Metro, Mahmutbey-Mecidiyeköy Metro, Yenikapı-Hacıosman Metro (Taksim Metro), Üsküdar-Ümraniye-Çekmeköy-Sancaktepe Metro, Kadıköy-Kartal Metro, Marmaray, Istanbul's first sub-sea tunnel train under Bosporus, and Suburban train lines.In highways, it will connect the 3rd Airport, currently under construction, and Yavuz Sultan Selim Bridge, the third bridge on Bosporus which is also under contruction, connection to North Marmara Highway, TEM and D100 (E-5) Highway.The diameter of the tunnel will be 16.8 meters and will be built 110 meters from the sea surface. The depth of the sea where it crosses the Bosporus will be 60-65 meters and the length of the part that will contain both the metro and the highway shall be 6.5 kilometers.There will be 14 stops on the 31 kilometer fast metro track between İncirli and Söğütlüçeşme. The metro section with a 1.5 million passenger capacity and 75,000 passenger capacity in one direction will be integrated with nine other rail systems and is expected to be used by 6.5 million passengers.The highway section of the project will cover the distance between TEM Higway Hasdal Crossroad and Ümraniye Çamlık Crossroad and will be around 16,150 meters. The section before the three-level tunnel on the European side will be 5.6 kilometers, the three-level section is 6.5 kilometers and the part after the three-level section on the Anatolian side will be 4.5 kilometers long. It will enable travelling from Hasdal to Çamlık in 14 minutes and the highway has a capacity of 120,000 vehicles on a daily basis. The number of lanes will be 2 by 2. All details have been planned for a safe journey of Istanbul's residents in the Three-level Big Istanbul Tunnel Project. In order for cars that have broken down to stop without affecting the traffic, there will be stop areas every 500 meters. With cameras installed at these points, quick help will be provided. Further there will be stairs and gateways between the levels for emergency situations every 240 meters. Further, horizontal and perpendicular fans will provide adequate ventilation, there will be an automatic air quality monitoring and detection system along with cameras and intercom systems, fire sensing and extinguishing systems, inner tunnel announce system, smart lighting system that regulates the brightness according to the weather outside and various precautions for quick intervention of the personnel in cases of emergencies. All materials used in the construction will be made out of non-combustible material and the general structure will be earthquake resistant.The fast metro section's rail system will be built by using state-of-the-art equipment and shall include an automatic signaling system that can be used both with or without a driver. Further, trains will be equipped with computer systems that will detect any delays in the previous trains and adjust the acceleration and deceleration accordingly. There will be digital dynamic road maps on the doors showing which station is next and further, the trains shall be 25 percent faster than the current metros. The environment-friendly project's metro section will have 175,000 tons of carbon dioxide emission a year and ensure 54 million liters less consumption of fuel oil. The highway section will increase the capacity of Fatih Sultan Mehmet Bridge by 50 percent. The project will not intersect with residential areas and support TEM axis, will not create visual pollution and ruin the skyline of the city.

Istanbul's first sub-sea tunnel project, Marmaray, opened on October 29, 2013. The second, the Eurasia Tunnel ("Avrasya Tüp Tüneli" in Turkish) is on its way: the double-deck tunnel will cross the Bosphorous strait undersea, connecting Kazlıçeşme district on the European side of Istanbul with Göztepe district on the Asian side through a 14.6 km (9.1 miles) route. It is due to open in 2016.