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Marmaray: Istanbul "cross Bosphorus" tunnel

Even though Istanbul is famous for being the city linking Europe and Asia, a direct rail crossing still does not exist and trains have to board a train ferry to go across. The inefficiency of the current system is easy to see: A train ferry's capacity is about 400 tons (or 5 fully loaded Habis wagons), currently a standard TCDD freight train limit is between 900 to 1600 tons. Therefore, it takes 3 or 4 (possibly more) ferry journeys to transport a single standard freight train across the bosphorus, easily taking several hours - a classic bottleneck.

Projects to built such a link were perhaps as numerous as the cross Channel projects, however nothing materialized. Finally, as the century closed, a serious project could be put together and now the tunnel under the Bosphorus is one of the most ambitious civil engineering project currently in Europe.

Marmaray, the brand name of the cross Bosphorus tunnel, has been given a definitive push thanks to Japanese funding. A loan agreement signed in Ankara on 19 August 1999 released US$ 117 m from a total funding US$866m provided by the Japan's Overseas Economic Co-operation Fund. This money allowed design and project tendering phase to proceed along with some preliminary works.

The whole Marmaray project, costed at a total of US$1·6bn includes a 13,3 km Bosphorus crossing and the upgrade of 63 km of suburb line to create a 76,3 km high capacity line between Gebze and Halkalı. The Bosphorus crossing will be done by a 1387m earthquake-proof immersed twin tube, assembled from 18 sections. This tube will be accessed by bored tunnels from Yenikapı on the European side and Sögütlüçesme on the Anatolian side. Intermediate stations will be done at Sirkeci and Üsküdar. An interchange station with Istanbul metro and light rail will be built at Yenikapı.

The upgrade of the suburb lines requires the laying of a third track along most of the way to increase the line capacity up to 75,000 passengers/h in each direction. Signaling must also be modernized to allow 2 minutes headway service. The 41 stations along the line will be refurbished and the platform lengthened to 180m.

Civil work started in May 2004 an the undersea tubes were actually completed in 2008. However work got delayed by major archeology discoveries, an event to be expected in a city of 2700 years. In particular, the engineers discovered what is now called the port of Theodosius. It is a complete port, dating from the 4th century, that was backfilled over the years. The most interresting was the 40 or so vessels that were discovered inside the port, some in very good shape. It is now expected that the project will be completed by the end of 2013.

TCDD indicates that 544 EMU cars are needed at the opening, possibly rising to 672 cars in 2015/2018.

Please visit the excellent website, specifically done for this highly visible project.

See also Marmaray (in Turkish) and Marmaray (in Turkish and English)

See in particular the pictures to understand the difficulty of digging in Istanbul, a city built on top the remains of several ancient cities.