The final section of the Gayrettepe-Istanbul Airport-Halkalı Metro Line, Türkiye's longest and fastest metro line, was inaugurated with the participation of President Recep Tayyip Erdoğan. With the Halkalı-Arnavutköy section, which entered service at a ceremony held at Kayaşehir Metro Station on June 19, 2026, the total 69-kilometre line was fully completed. The line is equipped with ASELSAN's domestic and national signalling system, COBALT, and will operate with full autonomous driving capability.
A 69 km Giant Line: Integration from Marmaray to High-Speed Rail
Minister of Transport and Infrastructure Abdulkadir Uraloğlu emphasised before the opening that the line would advance Istanbul's transport vision. Stating, "With the Halkalı-Arnavutköy section, we are realising a strong transport integration extending from Marmaray to the high-speed rail line, from urban metro networks to Istanbul Airport," Uraloğlu noted that the entire line is 69 kilometres long and will provide rail system integrity in a wide transport corridor extending to Gebze by working integrated with Marmaray.
The most critical feature of the line is that it offers an uninterrupted rail system connection between the two sides of Istanbul. A passenger departing from Halkalı can reach Gayrettepe via Istanbul Airport in 57 minutes. Airport connections are much shorter: it will take 30 minutes from Halkalı to Istanbul Airport and 27 minutes from Gayrettepe to the airport.
A Revolution in Travel Times
The new line radically reduces travel times between different points in Istanbul. Travel times will be: 50 minutes from Küçükçekmece to Kemerburgaz, 43 minutes from Halkalı to Göktürk, 48 minutes from Başakşehir Metrokent to Kağıthane, and 54 minutes from Halkalı to Kağıthane. Uraloğlu stated, "The maximum travel time of 57 minutes between Halkalı and Gayrettepe will provide great convenience to the daily lives of our citizens in a metropolis like Istanbul."
President Erdoğan announced after the opening that the line would serve free of charge until July 31.
Full Autonomous Driving with ASELSAN COBALT
Another detail that makes the line truly special is its signalling system. ASELSAN General Manager Ahmet Akyol announced that the line is the first metro line equipped with a domestic and national signalling system. "The first metro line we have equipped with a domestic and national signalling system has entered service with full autonomous driving capabilities. The ASELSAN COBALT Metro Signalling System will serve millions with this line," said Akyol, wishing well for the country's fastest and longest driverless metro line.
COBALT is ASELSAN's domestic signalling platform developed for metro and rail systems. Offering full autonomous driving capability, the system allows for driverless metro operation while also optimising service frequency and increasing energy efficiency. This line is the first project where COBALT has been implemented end-to-end on a metro line.
A Permanent Addition to Istanbul's Rail System Map
With the Halkalı-Arnavutköy section entering service, a critical gap in Istanbul's rail system network has been closed. While the line directly connects the north-south axis of the European side, it also elevates the integration of Istanbul Airport with the city centre to the highest level. Minister Uraloğlu stated, "We are offering Türkiye's longest and fastest metro line to the service of our nation, adding another permanent work to Istanbul's transport map."
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