The Ankara–Istanbul high-speed railway (), is a long high-speed railway linking Ankara and Istanbul in Turkey. The railway runs mostly parallel to the Istanbul-Ankara railway and passes through some of Turkey's most urbanized areas. The line hosts high-speed YHT train service with a maximum operating speed of .
Construction of the railway began in 2003, with testing commencing in 2007. On 13 March 2009 the first section of the railway, a section between Ankara and Eskişehir, opened to revenue service, making it the first high-speed railway in Turkey and the Middle East. On 25 July 2014, the railway was opened to Pendik, an eastern suburb of Istanbul, and with the completion of the Marmaray commuter rail project, opened to Söğütlüçeşme in central Istanbul on 19 March 2019.
History
Attempts to construct a high-speed railway between Istanbul and Ankara date back to 1975, when the Turkish government finalized plans to build the Istanbul-Ankara rapid railway (). This railway would diverge off the Istanbul-Ankara railway at Sincan and take a more direct route through the Köroğlu Mountains and re-join the existing railway at Arifiye. This new railway would shorten the route between the two cities by and with a planned maximum speed of , it would drastically reduce travel time from 7.5 to 11 hours to 4.5 hours. The project was put into motion in 1976 when the tender to construct the Ayaş Tunnel was awarded to Nurol. The following year, on 28 March 1977, Deputy Prime Minister Necmettin Erbakan broke ground for the tunnel which would have been Turkey's longest railway tunnel at the time. However political instability, constant changes in government and problems with the construction of the tunnel delayed the project until construction was halted in the aftermath of the 1980 Turkish coup d'état. Following the coup, Turgut Özal was elected Prime Minister and his pro-automobile policies negatively impacted the project further.
The Turkish government mothballed the project in the early 1990s and instead chose to upgrade the existing railway to accommodate speeds of up to . However, due to the sharp curves west of Eskişehir, many sections of the route would only be upgraded to accommodate speeds of to , which would impact overall transit times. A section of track between Eskişehir and İnönü was upgraded and expanded to a double-track line, opening in 1996. Apart from this short stretch of track, no further progress was made until September 1999, when the State Railways finalized plans of the railway between Eskişehir and Esenkent. Since this section of the railway runs through the relatively flat Ankara Plain, it would be upgraded to have a max speed of . On 23 November 2000, the tender was awarded to the consortium ALSİM-ALARKO-OHL at a cost of €437 million. In the months following the agreement, the 2001 Turkish economic crisis hampered construction efforts and thus no progress was made on the railway. Groundbreaking finally began on 8 June 2003 in Ankara. This was done with a large ceremony in which then-Prime Minister Recep Tayyip Erdoğan attended.
Initial construction focused on the upgrading of signalization between Ankara station and Sincan as well as Eskişehir and İnönü. Construction of the new right-of-way began in 2004 on the section between Esenkent and Eskişehir. However, the entire project was again subject to change. The project was revised and improved to increase speeds from to and instead of sharing the tracks with other rail traffic, the route would become a dedicated high-speed railway. This improvement was made official on 5 May 2005, when Erdoğan's cabinet approved the change. This new railway would be constructed separate from the existing one and be extended west of Eskişehir to Istanbul, thus becoming a true high-speed railway.
Project
The railway was divided into two main sections, with seven sections overall. In urban areas, the railway would run adjacent to or share the same right-of-way with the existing Istanbul-Ankara railway; thus these sections would also be upgraded to accommodate higher speeds. Along with upgrading shared portions of the route, the State Railways would integrate the high-speed railway with its urban commuter rail projects in Istanbul and Ankara. This included expanding the right-of-way from two tracks to three tracks in Istanbul and from three tracks to five tracks in Ankara along with rebuilding and modernizing existing stations.
Ankara-Sincan
On the long stretch between Ankara station and Sincan, the high-speed railway shares the same right-of-way as the Istanbul-Ankara railway. Just like in Istanbul, the Turkish State Railways planned to upgrade and expand the entire route, to segregate track between commuter rail and high-speed and intercity rail and integrate it with the Ankara–Istanbul high-speed railway. In 1972, the railway had been expanded to three tracks; two tracks for commuter trains and one track for intercity and freight trains. Since Ankara was planned to be the center of Turkey's high-speed rail network, the existing track layout would not support increased train traffic. So the State Railways planned to expand the railway and rebuild and modernize the route. Between Ankara station and Marşandiz, the existing four tracks would be expanded to six tracks; two for commuter trains, two for high-speed trains and two for inter-city and freight trains. Between Marşandiz and Sincan, the existing three tracks would be expanded to five tracks; two for commuter trains, two for high-speed trains and one for inter-city and freight trains. Plans originally expected construction to begin in 2009 and finish in 2011.
By 2009, no progress had been made on upgrading the railway, except building a temporary platform at Sincan, for high-speed trains. With new high-speed train service between Ankara and Eskişehir beginning in 2009 and between Ankara and Konya in 2011, the existing track capacity could not support the increase of trains. In 2011, the State Railways began to add a fourth track as well as upgrade the existing inter-city track. Commuter rail service was temporarily suspended as high-speed and inter-city trains began to use the south two tracks, while construction progressed. Originally, commuter trains were to be suspended for three months, but this later became two years. During this time, the railway was completely grade separated and a fourth track was added but construction of the full project did not progress very far. With public backlash to the closure, commuter trains were reinstated on 31 July 2013. It wasn't until 2016, when the project was restarted. Commuter train service was again suspended for 24 months. However, high-speed and inter-city rail service would be unaffected by the construction as they used the newly expanded north tracks to enter and exit Ankara. Construction progressed quickly and the Ankara-Sincan section of the route was fully opened on 12 April 2018.
Section 1 (Sincan-Eskişehir)
The first main section of the railway is the long stretch from Sincan, a western suburb of Ankara, to Eskişehir. This portion itself was constructed in three separate sections.
The first section branches off the existing railway at Sincan. From there it uses the right-of-way of the never completed Istanbul-Ankara rapid railway for until turning southwest. Passing through a cut-out, a viaduct and a tunnel, to navigate the hills west of Sincan, it crosses the existing railway at Esenkent, where a junction was built. Construction of this stretch of route begun in 2004 and construction ended in 2009. However, the route did not open to revenue service until 13 March 2010. With a top speed of , the longest bridge on this section spans and the longest tunnel spans .
The second and longest section spans from Esenkent to Eskişehir. Following the junction at Esenkent, the line runs parallel to the existing railway for the whole route. East of Polatlı, the high-speed railway heads around the southern periphery of the town, where a new high-speed railway station was built. This station, accessible via the D.260, is the first railway station in Turkey, exclusively for high-speed rail. West of Polatlı, the railway passes Polatlı junction, where the Polatlı-Konya high-speed railway, opened in 2011, branches south to Konya. Following this junction, the railway crosses the Sakarya River over the Sakarya Viaduct. Crossing the river and the adjacent plains, the Sakarya Viaduct is the third longest bridge in Turkey, spanning . Just east of Eskişehir, the high-speed railway rejoins the conventional one and uses the existing right-of-way to access Eskişehir station.
Construction of this section began in 2004 and was completed in March 2007. The State Railways approved testing on the route on 28 March 2007 and an agreement was made, two days later, with TÜV SÜD Rail Gmbh. A set of Italian ETR 500 Y2 high-speed EMUs were borrowed from the Italian railways to conduct testing on the railway. The EMUs, consisting of four cars and two power cars, began testing on the railway on 25 April 2007. Testing was done with a foreign high-speed train set because the Turkish State Railways' order of their own high-speed train sets were still under construction in Spain. During testing, the ETR 500s set a new Turkish railway speed record, reaching . A few months later, the same trainset broke its own record and set a new one on 14 September 2007, reaching . This remains the highest speed ever reached by a train in Turkey.
This is the first section on which construction began as well as the first section to open to revenue service. High-speed rail service was inaugurated on 13 March 2009, between Ankara and Eskişehir. However, until the 15 km section between Esenkent and Sincan was completed, high-speed trains used the existing railway until Esenkent, limiting speeds to . The entire line opened in full a year later on 13 March 2010.
Section 2 (Eskişehir-Köseköy)
The second main section of the railway is the long stretch from Eskişehir to Köseköy, an eastern suburb of İzmit. This portion of the route was constructed in two separate sections.
Between Eskişehir and İnönü, west, the existing railway was double-tracked in 1996 and was originally planned to be upgraded to allow speeds of . However, when the project was revised to increase speeds to , a new right-of-way (mostly parallel to the existing one) was to be built. Plans were finalized in 2004, but construction did not begin until 2006. On 24 March 2006, a tender was signed with SİGMA İns. ve Turz. İşl. Tic. AŞ and construction began on 3 April. While most of this section was complete by 2012, it did not open until the rest of Section 2 was completed, in 2014.