The first metro line was conceived as a means of carrying passengers from the city centre to the City Park without the need for surface transport on Andrássy Avenue. The Diet of Hungary approved the metro project in 1870. Construction began in 1894 and was carried out by the German firm Siemens & Halske AG.
This original metro line followed a northeast-southwest route along Andrássy Avenue from Vörösmarty Square, in the centre of the city, to the City Park and Zoo (Széchenyi fürdõ), a distance of 3.7 kilometres (2.3 mi). There were a total of eleven stations on the line, with nine underground and two above-ground; the original terminus at the Zoo has since been supplanted (by Mexikói út station, further to the northeast, in 1973). With trains running every two minutes, the line was then capable of carrying up to 35,000 passengers per day. One of the original Budapest Metro cars has been preserved at the Seashore Trolley Museum. Original carriages can also be seen in the Underground Railway Museum at Deák Ferenc tér station
The line was originally scheduled for completion in 1955, but construction was put on hold for financial and political reasons from 1954 to 1963. Line 2 was built with help of soviet specialists and finally opened with seven stations on April 4 1970. It follows an east-west route, connecting the major Keleti (Eastern) and Déli (Southern) railway stations. It has a joint station with the original line at Deák Ferenc Square.
The first line underwent a thorough refurbishment between 1970 and 1973, which included replacement of its rolling stock and a switch from left-hand drive to right-hand drive for the sake of consistency. In 1973, both lines were extended—the first with one station and the second with four. The lines reached their current lengths of 4.4 kilometres (2.7 mi) and 10.3 kilometres (6.4 mi), respectively. The Budapest Transport Company (BKV) took over operation of the metro that same year.
Planning for Line 3 began in 1963 and construction started in 1970 with help of soviet specialists. The first section, consisting of six stations, opened in 1976. It was extended to the south in 1980 with five additional stations, and to the north in 1981, 1984, and 1990, with nine additional stations. With a length of approximately 16 kilometres (9.9 mi) and a total of 20 stations, it is the longest line in Budapest.
Concurrently with the opening of Line 3, the metro adopted a colour-coding scheme for easier identification. The first line was given the colour yellow, the second line red, and the third, blue. Additionally, green is used to mark the suburban railways (HÉV) in and around Budapest.
In the 1980s and 1990s, Line 1 underwent major reconstruction. Of its 11 stations, eight are original and three were added during reconstruction. The original appearance of the old stations has been preserved, and each station feature displays of historical photographs and information. There is also a Millennium Underground Museum in the Deák Ferenc Square concourse.
Line 4 has a long history, dating back to 1972. In the planning phase, difficulties arose from the medicinal springs (for example, the Gellért Baths) around its planned route. There was a long debate over whether its construction would be safe, what part should be funded by the government and the capital, whether it could be paid for from the Russian state debt towards Hungary, whether the route and length were appropriate, and whether a connector line (see M5 below) would be a better use of funds. When the Line 4 was finished in 2014, its planning and construction spanned 42 years, longer than any other Budapest metro line.
The Metro consists of four lines, each designated by a number and a colour. Line 1 runs northeast from the Pest city center to City Park along Andrássy Avenue. Line 2 runs generally east to west from the transit hub Örs vezér tere on the city's east side, and provides a connection between Keleti railway terminal and Déli railway terminal through the city center. Line 3 runs northwest from the transit hub Kőbánya-Kispest in the city's southeast, along Üllői út to the city center, and then north to the district of Újpest. Line 4 runs southwest to northeast from the transit hub of Budapest Kelenföld railway station in the city's most populous district of Újbuda across the inner city district of Józsefváros to Keleti railway terminal.
Lines 1–3 converge at Deák Ferenc tér in the city centre, which was long the system's only transfer station. This bottleneck has been remedied by the opening of Line 4, which crosses Line 2 and Line 3 at different stations. The Metro forms a partially separate system from the Budapest HÉV commuter rail, though Line 2 of the Metro provides transfers to the termini of two of the four HÉV lines. Integration of the incompatible HÉV system into the Metro is a long-term goal, and forms the basis of the proposed Line 5.Except for short stretches near the depots of each line, the system is mostly underground.
Line 1 runs northeast from the city center on the Pest side under Andrássy út to the Városliget, or City Park. Like Metro 3, it does not serve Buda. Line 1, the oldest of the metro lines operating in Budapest, has been in constant operation since 1896.
Line 2 has undergone major reconstruction, with all of the track and stations completed in 2008.
Line 3 runs in a north-south direction (more exactly, from north-northeast to southeast) through the city and connects several populous microraion with the downtown. It has a transfer station with Line 1 and Line 2 at Deák Ferenc tér, and a transfer station for Line 4 at Kálvin tér. It is the longest line in the Budapest Metro, its daily ridership is estimated at 610,000.
Line 4 connects Kelenföld Station and Keleti Railway Station, and has a length of 7.4 kilometres (4.6 mi). It was completed in March 2014, and comprises ten stations.
The proposal for Purple Line 5 is for a rapid rail system which will include the Budapest-Esztergom heavy railway line. The Csepel and Ráckeve HÉV lines will be connected on the surface, near the National Theatre.
The implementation of latest generation automated fare collection and e-ticket system with NFC compatibility and reusable contactless smart cards for making electronic payments in online and offline systems in Budapest is started in 2014, the project is implemented and operated by the operator of Hong Kong Octopus card jointly with one of the leading European companies of e-ticket and automated fare collection, Scheidt & Bachmann. The deployment of 300 new digital contactless ticket vending machine mainly at the metro stations, will be finished by the end of 2014 in harmonization with the e-ticket system.
Lines run from approximately 4:30AM until 11:30PM every day, though times vary slightly between lines.
The Budapest Metro is completely electrified and standard gauge in operation. Three different types of rolling stock are currently in service: