Line 4 has had different types of rolling stock throughout the years.
29 August 1981: from Martín Carrera to Candelaria. Thirty-one more stations would be built according to the plan: ten southbound and 21 northbound, adding a total of 34.87 km to Line 4. In this document, there is an extension planned for Line 4 that would expand the line northward from Martín Carrera towards Tepexpan and southward from Santa Anita to the southern part of the Periférico. In 2018, the STC again presented a plan projected to 2030. As with the 1985 plan, this extension was never built. This new section would have six new stations and a length of 6.1 km. In 1996, the Sistema de Transporte Colectivo (STC) on its master plan for Mexico City Metro considered building an expansion for Line 4 this time, it would be expanded northbound from Martín Carrera to Ecatepec in the State of Mexico. In 1985, according to a plan presented by the Comisión de Vialidad y Transporte Urbano (COVITUR), Line 4 was projected to be expanded southbound from Santa Anita towards Culhuacán, the stretch would have a length of 9.22 km and seven new stations. Transfer to Line 6 at Martín Carrera would open in 1986, to Line 9 at Jamaica in 1987, to Line 8 at Santa Anita in 1995 and to Line B at Morelos in 1999. Upon completion of the line, it had only two transfer stations: Candelaria with Line 1 and Consulado with Line 5. The second stage of the line was opened for service on, with four new stations, going from Candelaria to Santa Anita. The total cost of Line 4's first stage was 6,900 million pesos. Lines 9, B and 12 would later also have elevated sections. Line 4 was the first line to feature an elevated section, built over Avenida H. The first stretch of Line 4 was inaugurated on 29 August 1981, from Martín Carrera station to Candelaria station. Also, trains in Line 4 have been shortened from its original configuration of nine cars to only six. A side effect of this is having long passageways with connecting lines, generally unused or empty sections in stations, closed passageways and other features, all due to its low ridership. The line is also characterized by its above-ground architecture, having all of its station facilities elevated or in massive buildings present in both sides of the street. However, it is also the line with the fewest passengers in the entire system, having only 29,013,032 passengers throughout 2019. With only ten stations, its short length is countervailed with its high connectivity, having transfer with other metro lines in six stations: Line 6 at Martín Carrera, Line 5 at Consulado, Line B at Morelos, Line 1 at Candelaria, Line 9 at Jamaica and Line 8 at Santa Anita. It was built above the former Inguarán Avenue (now Congreso de la Unión) in viaduct solution, this makes it the only line without an underground section. For more guidance, see Wikipedia:Translation. You should also add the template to the talk page. A model attribution edit summary is Content in this edit is translated from the existing Spanish Wikipedia article at ] see its history for attribution. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. If possible, verify the text with references provided in the foreign-language article. Do not translate text that appears unreliable or low-quality. Consider adding a topic to this template: there are already 4,924 articles in the main category, and specifying |topic= will aid in categorization. Machine translation like DeepL or Google Translate is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia.