|Marmaray, the world's deepest immersed tube tunnel|
|Start||Fatih, Istanbul, Turkey|
|End||Üsküdar, Istanbul, Turkey|
|No. of stations||41|
|Work begun||May 9, 2004|
|Opened||October 29, 2013 (target)|
|Length||1.8 km (1.1 mi)|
|Line length||76.3 km (47.4 mi)|
|No. of tracks||2 single track tunnels
3 track on surface with
additional passing loops
|Track gauge||1,435 mm (4 ft 8 1⁄2 in)|
|Electrified||25 kV, 50 Hz AC|
|Operating speed||45 km/h (28 mph)|
Marmaray is a rail transport project in Istanbul. It consists of the construction of an undersea rail tunnel under the Bosphorus strait as well as the modernization of suburban rail lines along the Sea of Marmara from Halkalı on the European side to Gebze on the Asian side. The procurement of new rolling stock for suburban passenger traffic is also part of the project. Construction started in 2004, with an initial target opening date of April 2009. After multiple delays, the projected opening date (as of March 2013) is October 29, 2013.
The project 
The project includes a 13.6 kilometres (8.5 mi) Bosphorus crossing, the upgrade of 63 kilometres (39 mi) of suburban train lines to create a 76.3 km high-capacity line between Gebze and Halkalı and the provision of 440 rail cars.
The Bosphorus (Istanbul Strait) will be crossed by a 1.4 kilometres (0.87 mi)-long earthquake-proofed immersed tube, assembled from 11 sections, eight are 135 metres (443 ft), two are 98.5 metres (323 ft) and one element is 110 metres (360 ft) long. The elements are weighing up to 18,000 tons. The sections will be placed down to 60 metres (197 ft) below sea level: 55 metres (180 ft) of water and 4.6 metres (15 ft) of earth. This underwater tube will be accessed by bored tunnels from Kazlıçeşme on the European side and Ayrılıkçeşme on the Asian side of Istanbul. When completed, it will be the world's deepest undersea immersed tube tunnel.
New underground stations will be built at Yenikapı, Sirkeci, and Üsküdar. 37 other above-ground stations along the line will be rebuilt or refurbished. The station at Yenikapi will connect with Istanbul Metro and Istanbul LRT. The above-ground suburban lines will be upgraded to three tracks, two for commuter and one for long-distance/high-speed passenger trains (bi-directional). The tunnel section allows for two, bi-directional tracks to be used by commuter and long-distance trains. During off-peak hours, freight trains may also cross the tunnel. The capacity for the suburban lines is planned for 75,000 passengers per hour in each direction. Signaling must also be modernized to allow trains to be as close as two minutes apart. The predicted travel time from Gebze to Halkalı is 104 minutes.
Construction of the Marmaray project started in May 2004. The Marmaray tunnel was completed on the 23rd of September 2008, with a formal ceremony to mark completion of the tunnel on October 13. Completion of the entire project has been repeatedly delayed, and as of December 2009, was expected to occur in October 2013. By 29th of October, the first stage of Marmaray project will end which covers the underground connection between Europe and Asia. Passangers will be able to travel between Yenikapı and Ayrılıkçeşme. The second stage is the renewal of current railway on ground, between Gebze and Ayrılıkçeşme on Asian side and between Yenikapı and Halkalı on European side. A third line will added which will provide the metro and trains will move separately.
After completion, the usage of rail transportation in Istanbul is predicted to rise from 3.6% to 27.7%.
Rolling stock 
|Number under construction||80|
5/10 cars per train
34 trains with 10 cars20 trains with 5 cars
|Operator||Turkish State Railways|
|Floor height||1300 mm|
|Platform height||??? mm|
|Electric system(s)||Overhead line|
|Current collection method||Pantograph|
|Track gauge||Standard gauge|
Hyundai Rotem announced on November 11, 2008, that it had signed a €580m contract to supply the rolling stock for the Marmaray cross-Bosporus tunnel project in Istanbul. The Korean firm had competition from shortlisted bidders Alstom, CAF and a consortium of Bombardier, Siemens and Nurol for the 440-vehicle contract which was placed by the Ministry of Transport's General Directorate of Railways, Harbours & Airports.
The 22 m long stainless steel cars will be formed into 10 and five-car EMUs. Some production will be carried out locally by Eurotem, Hyundai Rotem's joint venture with Turkish rolling stock manufacturer TÜVASAŞ. The cars will arrive in three batches, the first 160 cars by 2011, the last by June 2014.
The project is currently four years behind schedule, largely due to the discovery of a Byzantine-era archaeological find on the proposed site of the European tunnel terminal in 2005. The excavations produced evidence of the city's largest harbour, the 4th-century Harbour of Eleutherios (later known as the Harbour of Theodosius). There, archaeologists uncovered traces of the city wall of Constantine the Great, and the remains of several ships, including what appears to be the only ancient or early medieval galley ever discovered, preventing the project from proceeding at full speed. In addition, the excavation has uncovered the oldest evidence of settlement in Istanbul, with artifacts, including amphorae, pottery fragments, shells, pieces of bone, horse skulls, and nine human skulls found in a bag, dating back to 6000 BCE.
The suburban rail upgrade section of the project, known originally as CR1, faltered and is undergoing a re-tendering process due to attract bids in early 2011. The original CR1 consortium (AMD Rail Consortium) consisted of Japan's Marubeni, Turkey's Dogus Insaat and France's Alstom.
Tunnel construction is only about 18 kilometres (11 mi) from the active North Anatolian Fault, worrying engineers and seismologists. "Since AD 342, it has seen large earthquakes that each claimed more than 10,000 lives." Scientific calculations to estimate the probability that at some time in the next 30 years the area will suffer an earthquake of strength 7.0 or more produced an outcome of 77 percent. The waterlogged, silty soil on which the tunnel is being constructed has been known to liquefy during an earthquake; to solve this problem, engineers are injecting industrial grout down to 24 metres (79 ft) below the seabed to keep it stable. The walls of the tunnel will be made of waterproof concrete coated with a steel shell, each independently watertight. The tunnel is made to flex and bend similar to the way tall buildings are constructed to react if an earthquake hits. Floodgates at the joints of the tunnel are able to close and isolate water in the event of the walls' failure.
Steen Lykke, project manager for Avrasyaconsult, the international consortium that's overseeing the construction, sums it up saying, "I can't think of any challenge this project lacks".
The Japan International Cooperation Agency (JICA) and the European Investment Bank have provided major financing for the project. As of April 2006, JICA had lent 111 billion yen and EIB 1.05 billion euro. The total cost of the project is expected to be approximately 2.5 billion US dollars. As of late 2009, costs were expected to increase by approximately 500 million US dollars due to the archaeological delays.
The Marmaray project has been criticized many times throughout the years by newspapers, politicians and mostly railway workers and railway enthusiasts. The criticism is due to the fact that the Marmaray project includes decommissioning the port of Haydarpaşa as well as closing İstanbul's two main railway terminals: Haydarpaşa Terminal and Sirkeci Terminal, which are historically important as railway stations. The tracks will be removed and the buildings will be turned into hotels, which has brought an uproar of rage in Turkey's railway community. Other criticisms are because of the demolition or replacement of other historically significant railway stations and railway bridges, such as Göztepe railway station. Also, it is planned to have all intercity trains terminate at Gebze and Halkalı and have passengers transfer to local commuter trains, which would make trains much more crowded and very uncomfortable for passengers with heavy luggage.
Marmaray in numbers 
- Overall length: 76.3 km (47.4 mi)
- Tunnel section: 13.6 km (8.5 mi)
- Immersed tube: 1,387 m (4,551 ft)
- Deepest point: 60.46 m (198.4 ft)
- Minimum curve radius: 300 m (980 ft)
- Maximum gradient: %1.8
- Surface stations: 38
- Underground stations: 3
- Interchanges: 4
- Inter-city stations: 8
- Platform length: 225 m (738 ft)
- Average station spacing: 1.9 km (1.2 mi)
- Design speed: 100 km/h (62 mph)
- Minimum headway: 120 sec
- Passengers per hour and direction: 75,000
See also 
- Rails under the Bosporus, Railway Gazette International 2009-02-23
- Smith, Julian. "The Big Dig" Wired Magazine. Sept. 2007: pages 154–61.
- Facts and figures, web page at the Marmaray web site. Accessed on-line September 24, 2007.
- Travel time and alignment, web page at the Marmaray web site. Accessed on line, 24 September 2007.
- Istanbul Metro and LRT, web page at the Marmaray web site. Accessed on-line September 24, 2007.
- Istanbul, web page at urbanrail.net. Accessed on line September 24, 2007.
- Final tubes sunk on Bosphorus Tunnel, International Railway Journal, November 2008.
- Marmaray completion delayed to 2013, cost increases by $500 mln, Today Zaman 2009-12-19
- Contracts February 2010, Railway Gazette International 2010-02-09
- Marmaray train contract signed, Railway Gazette International 2008-11-14
- Tunnel links continents, uncovers ancient history CNN
- Rose, Mark; Aydingün, Sengül. "Under Istanbul". Archaeology.org. Archaeological Institute of America. Retrieved 2008-10-27.; Nautical archaeology takes a leap forward, The Times, 31 December 2007
- Haydarpasa's protection in danger, kentvedemiryolu.com
- Andlauer, Anne. "La gare de Haydarpaşa est-elle en danger ?". LePetitJournal. Retrieved 11 November 2012.
- Marmaray project's negative effects on Istanbul, kentvedemiryolu.com
- Marmaray project official website
- Overview of the Marmary history, justification, and construction process with pictures
- Marmaray Project:
- L. C. F. Ingerslev, 2005, "Considerations and strategies behind the design and construction requirements of the Istanbul Strait immersed tunnel," Tunnelling and Underground Space Technology 20: 604-08.
- Steen Lykke and Hüseyin Belkaya, 2005, "The project and its management," Tunnelling and Underground Space Technology 20: 600-03.
- Steen Lykke and Frits van de Kerk, 2005, "Marine operations, the Bosphorus Crossing," Tunnelling and Underground Space Technology 20: 609-11.
- Hideki Sakaeda, 2005, "Tunnels and stations in BC contract," Tunnelling and Underground Space Technology 20: 612-16.
- Ahmet Gokce, Fumio Koyama, Masahiko Tsuchiya, Turgut Gencoglu, 2009, "The challenges involved in concrete works of Marmaray immersed tunnel with service life beyond 100 years," Tunnelling and Underground Space Technology 24: 592-601.
- Istanbul Technical University Marmaray Laboratory web site.
- Tunnelbuilder technical description.
- (Turkish) Marmaray BC1 project and surveying works
- BBC article on the project.