Turkish State Railways (TCDD) started building high-speed rail lines in 2003.

By 2023, the Ministry of Transport and Infrastructure expects Turkey's high-speed rail system to increase to 10,000 kilometres (6,214 mi).

[8] The whole line was electrified, but low radius turns and poor track quality made high-speed rail transport impossible.

Prior to the upgrading of this line in 2006, the railway's market share of Istanbul–Ankara passenger transit was 10%, with a travel time of ~6.5 hours.

[8] The Ankara–Istanbul HST line opened on 25 July 2014, with all trains terminating at Pendik, which is 1 hour by bus from Kadikoy in the eastern suburbs of Istanbul.

[9] The first part of the line to be constructed (Phase 1) was the Ankara–Eskişehir section, specifically between Sincan and İnönü, scheduled to open in 2006.

The second phase was scheduled to open in 2008 and included more difficult terrain which covers the path between İnönü and Köseköy, extending to Gebze close to Istanbul.

[14] The line is operated by the Turkish State Railways, using the TCDD HT65000 six-car train sets constructed by the Construcciones y Auxiliar de Ferrocarriles (CAF) of Spain.

[23][note 2] The new high-speed line is 306 km (190 mi) in length, with a journey time of 1 hour and 15 minutes.

[23] 212 km (132 mi) of new track is constructed via Polatlı and Konya, with a design permitting up to 350 km/h (217 mph) of high-speed rail transport.

[31] A 2019 update predicted service in 2022, 3 years behind schedule due to "geographic difficulties",[32] but the project returned to the prior opening date of 2020 summer.

[34][35] The route study was completed by the end of 2006, and put up for tender in two parts; separated at the 174 km (108 mi) mark from Ankara at Yerköy.

[36] An extension eastwards to Kars from the Ankara – Sivas line is planned (a feasibility study done in 2006[38]), passing through Erzincan and Erzurum.

[40] The 247 km (153 mi) section will start from the current station in Sivas, through Hafik, Zara, Imranli, Refahiye, and end in Erzincan.

[42] The 201 km spur off the Istanbul-Ankara line from Osmaneli to Bandırma through Bursa is under construction and is slated for completion by 2026;[43] the full line will be built for 200 km/h operation and cost 9.5 billion lira, bringing travel times between Ankara and Bursa to 2 hours and 10 minutes.

The double-tracked electrified railway will be built for 215 km/h operation and cost 10.5 billion lira, of which more than half is provided by a European Union grant.

The construction of line is planned in three phases: Number of tunnels: 11 --- Total tunnel length: 8,000 metersNumber of viaducts: 16 --- Total viaduct length: 6,300 metersNumber of bridges: 24 The first high-speed trains to run on Turkish rails were two ETR 500 train sets rented from Trenitalia of Italy and were used for testing the completed part of the high-speed railway network, between Eskişehir and Ankara, on 23 April 2007.

Unlike the traditional white – red – dark blue color scheme used on the TCDD HT65000 high-speed trains, a white – turquoise – grey color scheme has been selected for the livery of TCDD's Velaro TR trains.