Delays

The Budapest city government delayed the opening of the line 17 times. Gábor Demszky, the liberal mayor of Budapest from 1990 to 2010, originally promised in 1998 that the first section of the line would be open by 2003. However, Viktor Orbán's first government (1998-2002) withheld funds necessary for starting the construction. The project restarted in 2003 under the socialist-liberal national government. In 2004, as construction still hadn't begun, Demszky amended the opening date to 2008. The construction works finally started in 2006; in that year the scheduled opening was changed to 2009. It was again changed - in April 2007 - to 2010; and in October 2007 to 2011.^[7]

In 2008, Gusztáv Klados, the line's project manager, announced that the opening would be further delayed until the end of 2011.^[14] In 2009, he stated the opening would be delayed until 2012.^[15] Later that year, Klados further delayed the opening until 2012,^[16] and one year later, in 2010, István Tarlós, Demszky's Fidesz successor as mayor, pushed the likely opening back to as late as 2015.^[17]

In 2011, deputy mayor Gyula Hutiray reaffirmed the 2015 completion date.^[18] Tarlós later clarified that a 2013 or 2014 opening were not outside the realm of possibility.^[19][20]

The line was opened by Prime Minister Viktor Orbán on 28 March 2014, one week before the parliamentary elections that saw his party, Fidesz, reelected to a second supermajority. Orbán made several references to his government's extensive infrastructure projects during the ceremony. Unlike the transport facilities that were the infrastructure projects of the socialists, the projects started by Orbán's government were mainly cultural facilities.^[21]

Costs

Construction of the line cost 1.5 billion Euros, or 1.5% of Hungary's annual GDP, of which 600 million came from European Union funds.^[21] According to estimates the first section of the M4 will have cost approximately 452 billion HUF to build alongside an annual operating cost of 6 billion HUF, which is fourfold the operating costs of the M2 and M3 combined. These funds, critics claim, would have been better invested in other large-scale transportation projects such as the connection of M2 to the Gödöllő HÉV or the construction of new tram lines.^[8] Rumors that the M4 would be the most expensive metro line ever built, however, have been rebuffed by contractors.^[22]

Route

Critics have noted that the route served by Line 4 was already extensively served by a variety of tram (19, 47, 49) and bus (7, 7A, 7E, 173E) lines. The line has also been criticized for densely placed stations, some, such as Móricz Zsigmond körtér and Újbuda-központ, within a few hundred meters of one another.^[8] On the other hand, the city government has conducted research showing that the new line will reduce travel times on a heavily used transit corridor, because travel in the subway is not slowed by the traffic jams on the surface.^[23]

Unfunded extensions

Despite long-term plans, which included the eventual extension to Rákospalota, future extensions to the M4 are uncertain. Tarlós's Fidesz city government eliminated funding for the second phase of the line after taking over from Demszky's government, and the European Union has refused to provide additional funds.^[4] Some critics claim that without the extensions the current state of the line amounts to "several hundred-million forints thrown out the window."^[4]

Operation

Driverless trains have been in operation since the opening,^[24] but until January 2016 all trains ran with on-board driver supervision. Since January 2016 the driver cabs have been removed and there is no on-board supervision.