Line 4 of the Madrid Metro was opened on 23 March 1944 between Goya and Argüelles. In 1958, the line took up a branch of line 2 from Goya to Diego de León, which originally opened on 17 September 1932. In the 1970s, the line was extended in two stages: from Diego de León to Alfonso XII (1973) and from Alfonso XIII to Esperanza (1979). On 1 April 1998, the line was extended from Esperanza to Mar de Cristal, to provide interchange with the new Line 8. Later that year on 15 December, the line was extended to Parque de Santa María. On 11 April 2007, an extension from Parque de Santa María to Pinar de Chamartin opened. At Pinar de Chamartin, interchange with Line 1 can be made and from spring 2007, interchange with Metro Ligero 1 (ML1) is available too. At Pinar de Chamartin, an island platform is used for departures, and a side platform for arrivals. Line 4 uses four-car trains of class 3400 since 2007.