a single vault technology initially developed for the Kharkiv Metro, it too became common elsewhere in the Soviet Union. Another station on this stretch was left unfinished because of the lack of need for it and remained derelict for thirty years. The station was completed and inaugurated in August 2014 under the name Spartak. Because the line is the busiest on the system, there are significant problems that overstretch its capabilities. In particular is the station Vykhino, which was built with too small a capacity to handle the congestion, making it the busiest on the system. In 2004 a severe reconstruction increased the area of the platforms and gave the station a desirable facelift. Nonetheless, that was insufficient to solve the problem, and in 2013 the line was extended to the south-eastern districts of Moscow outside the Ring Road with the opening of Zhulebino and Lermontovsky Prospekt stations. By September 2015, the line has reached a neighboring city of Kotelniki with the construction of an eponymous metro station there. The Kotelniki station opened on 21 September 2015 and became the new terminus of the southeastern radius. Timeline Name changes Stations Rolling stock The line is served by two depots, Planernoe (№ 6) and Vykhino (№ 11). Respectively 36 and 34 eight carriage trains are assigned to them. Most of the trains are Ezh3 and Em-508T models which were received new from 1974, currently all of the trains were modernized between 2003 and 2011 extending the service life by another 15 years. From 2012 to 2017, the line was also served by 10 81-717/714 trains, which were transferred here from other lines. As of 2019 the line is only served by Ezh and 81-765/766/767 trains. Subway car types used on the line over the years: Recent developments and future plans Southern radius After the opening of the Kotelniki station, there are no further development plans extending beyond 2020 horizon. Northern radius Extension of Arbatsko–Pokrovskaya line (Line 3) allowed easier access to the Metro system to the passengers from Strogino and Mitino districts, diverting them from the northern stretch of the Tagansko–Krasnopresnenskaya line. However, this relief was not very significant, mostly due to Arbatsko-Pokrovskaya line being relatively slow. It takes 30 minutes to reach the Koltsevaya line from Mitino station, while the older Tushinskaya-Barrikadnaya route takes 20. In addition, it does not offer convenient transfers to Kaluzhsko–Rizhskaya line and Kalininskaya line, as