İstanbul–Ankara Main Line

Istanbul–Ankara railway İstanbul–Ankara demiryolu
Looking east from Göztepe, İstanbul.
Overview
Type	Heavy rail
System	Turkish State Railways
Locale	Central Anatolia to Marmara Region
Termini	Ankara İstanbul
Services	1 (2 branch lines)
Operation
Opened	31 December 1892
Owner	Turkish State Railways
Operator(s)	TCDD Taşımacılık
Technical
Line length	576.6 km (358.3 mi)
Number of tracks	3 (Istanbul–Izmit) 4 (Izmit-Köseköy) 2 (Köseköy-Geyve) 1 (Geyve–İnönü) 2 (İnönü–Eskişehir) 3 (Eskişehir–Hasanbey) 1 (Hasanbey-Sincan) 4 (Sincan–Ankara)
Track gauge	1,435 mm (4 ft 8 1⁄2 in)
Operating speed	140 km/h (87 mph)

The Istanbul–Ankara railway (Turkish: İstanbul–Ankara demiryolu) is a 576.6 km (358.3 mi) long electrified railway in Turkey. The line connects Turkey's largest city, Istanbul, to the capital and second largest city, Ankara; making it one the busiest railways in the country in terms of passenger and freight rail traffic. The railway runs parallel to the Ankara-Istanbul high-speed railway and in several sections, the railway hosts YHT high-speed trains.

The line begins at Haydarpaşa Terminal in Istanbul and ends at Ankara railway station in Ankara.

Before the opening of the Ankara-Istanbul high-speed railway in 2009, the Istanbul–Ankara railway was the busiest line in Turkey as well as the primary inter-city route, connecting Istanbul with Ankara through five provincial capitals: Izmit, Arifiye (a suburb of Adapazarı), Bilecik, Bozüyük and Eskişehir. In 2008, 65% of all inter-city service used the railway entirely or at one point. The Haydarpaşa suburban and the Ankara suburban operated commuter service along the line in Istanbul and Ankara respectively. Freight rail traffic is heavy on the line as the railway connects to the Port of Haydarpaşa and the Port of Derince as well as other private ports and passes through several important industrial regions in Turkey. In 2015 the railway carried 6.1% of all freight rail traffic in Turkey.

Due to the construction of the Ankara-Istanbul high-speed railway, Marmaray and Başkentray, traffic on the railway declined greatly due to sections being closed down for several years. As of November 2016, the Haydarpaşa-Pendik section is still closed to all traffic as the rehabilitation of the line is still underway. No passenger service is operated between Arifiye and Sincan (not including YHT high-speed trains).