Line M4 Keleti pályaudvar — Kelenföld vasútállomás	7.3 km, 10 stations
The first plans to begin the constructions of M4 were started in the early 1970s. In these plans this metro line would have run between Rákospalota residential district (lakótelep) and the industrial zone Budafok. In 1997, tram lines 44 and 67 along Thököly út were abandoned due to the M4 plans. There were plans to abandon also tram lines 41, 47 and 49, but only after the completion of the metro line. The TBMs for M4 were eventually launched in 2006. Some trivia: - There is a connecting tunnel between lines 2 and 3, but line 4 isn't connected to any other metro line. - At Keleti pályaudvar, the station of line 4 isn't connected to line 2 via an underground passage, but just via the (partly open) mezzanine level. - At Kálvin tér, there is a transfer tunnel for passengers below the line 3 station, although line 4 is above the M3 station. - At Fövám tér, tram line 2 stops underground within the mezzanine of the metro station, but there was also a subsurface stop there before > photos.
History
28 March 2014: Keleti pályaudvar — Kelenföld vasútállomás
Stations

Keleti pályaudvar

II. János Pál pápa tér