Istanbul Tunnel: unique three-storey project under the Bosphorus 

In Istanbul, an ambitious project - the Great Istanbul Underwater Tunnel is being prepared for implementation. It will be the world’s first three-story underwater tunnel that will connect the European and Asian parts of the city.

Design features 
The tunnel, 6.5 km long, will pass at a depth of 110 m below sea level. It will consist of three levels: two for road traffic and one for rail transport. So the tunnel can simultaneously serve both cars and subway trains.

Major plans 
Construction of the tunnel began in 2016, and completion of the project is scheduled for 2028. The main goal is to improve transport links between parts of the city, reducing travel time. For example, the journey time from Hasdal to Camlik will be reduced from 40 to 14 minutes. 

Integration and benefit 
The tunnel will link three main airports in Istanbul - Atatürk, Sabiha Gökček and a new airport on the European side. In addition, nine urban metro lines will be integrated into the project, which will significantly increase its transport capacity.

Financial side 
The cost of building a tunnel will be $3.5 billion. The project is financed on the basis of concession - «construction-operation-transfer» models. The research and design work cost 35 million Turkish liras. 

Future prospects 
The tunnel is designed for a capacity of up to 6.5 million passengers and up to 120 thousand vehicles per day. It will be an important element of Istanbul’s transport infrastructure, solving many problems of mobility in the city and improving its investment attractiveness.