(more exactly, from north-northeast to southeast) on the Pest side of the river and connects several populous residential areas with the Inner City. It has a transfer station with Line 1 and Line 2 at Deák Ferenc tér, and an interchange with Line 4 at Kálvin tér. It is the longest line in the Budapest Metro, its daily ridership is estimated at 610,000. An automatic train drive system was introduced in 1990. A complete renovation of the line started in 2017. The planned upgrades include renewing the stations, rebuilding the track, safety equipment, ventilation and tunnel insulation. Design works are entirely funded by the European Union under the New Széchenyi Plan. The project also includes the renovation of the rolling stock and a possible extension of the metro line to Káposztásmegyer. As of May 2022, 12 of the 20 stations have been inaugurated. Metro line M4 Line 4 runs southwest–northeast from Kelenföldi pályaudvar in Buda's Kelenföld neighborhood to Keleti Railway Station in Józsefváros. With a length of , it connects to Hungarian State Railways at its termini, to the metro's Line 3 at Kálvin tér, and to Line 2 at Keleti. Line 4 was completed in March 2014 and comprises ten stations. Future expansion Metro line M5 The Purple Line 5 is a proposed north–south railway tunnel to connect the currently separated elements of the suburban rail network, namely the H5, H6 and H7 HÉV-lines, and optionally the Budapest-Esztergom and Budapest-Kunszentmiklós-Tass railway lines. Currently the project does not have mainstream political support, only included in long-term plans. The first phase (planned until 2030) would be the extension and connection of the southern H6 and H7 lines to the Astoria metro station via the Kálvin tér, thus connecting these lines to the metro lines M2 M3 and M4. The second phase would create a connection to the metro line M1 as well at the Oktogon, the M3 at Lehel tér then cross the Danube to the Buda side to connect the H5 HÉV towards Szentendre. General information Tickets and transfer system The usual BKK tickets and passes can be used on all lines. Single tickets can be re-used when changing metro lines. There are plans for an automated fare collection system. A contract for a system was signed in 2014, but terminated in 2018 without completion. In popular culture The internationally acclaimed 2003 Hungarian thriller Kontroll is set and was filmed