Now that trains run the entire length of the trans-Bosphorus Marmaray regional rail line through Istanbul, Turkey is turning its infrastructure attention to a second tunnel under the strait, this time carrying a metro line from Asia to Europe. Turkey’s Ministry of Transport and Infrastructure plans to build a three-deck tube beneath the Bosphorus that carries road traffic on its upper two decks and the metro line on its bottom one. The 4.3 kilometres tunnel would run between Burhaniye and Mecidiyeköy.
The tunnel will be the central link in a 30.2 kilometres line running between İncirli on the European, side of Istanbul and Söğütlüçeşme on the Asian side. The line will have 11 stations in Europe and four in Asia. The Asian stations include interchanges with the Marmaray line, metro line M4 and future metro line M5.
The line would have a projected capacity of 1·5 million passengers a day. The ministry’s Directorate of Infrastructure Investment has conducted test drilling at seven sites along the planned route and says that the first tenders could be launched later in 2019.