Buenos Aires
Urban rail

The Buenos Aires Underground (locally known as subte, from "subterráneo" meaning underground or subway), is a high-yield system providing access to various parts of the city. Opened in 1913, it is the oldest underground system in the Southern Hemisphere and oldest in the Spanish-speaking world. The system has six underground lines and one overground line, named by letters (A to E, and H) and there are 107 stations, and 58.8 km (37 mi) of route, including the Premetro line. An expansion program is underway to extend existing lines into the outer neighborhoods and add a new north–south line. Route length is expected to reach 89 km (55 mi) by 2011.

Line A is the oldest one (service opened to public in 1913) and stations kept the "belle-époque" decoration, while the original rolling stock from 1913, affectionately known as Las Brujas were retired from the line in 2013. Daily ridership on weekdays is 1.7 million and on the increase. Fares remain relatively cheap, although the city government raised fares by over 125% in January 2012. A single journey, with unlimited interchanges between lines, costs AR$42, which is roughly US$0.23 as of January 2023.

The most recent expansions to the network were the addition of numerous stations to the network in 2013: San José de Flores and San Pedrito to Line A, Echeverría and Juan Manuel de Rosas to Line B and Hospitales to Line H. Current works include the completion of Line H northwards and addition of three new stations to Line E in the city center. The construction of Line F is due to commence in 2015, while two other lines are planned for construction in the future.

The Buenos Aires commuter rail system has seven lines: Belgrano Norte; Belgrano Sur; Roca; San Martín; Sarmiento; Mitre; and Urquiza. The Buenos Aires commuter network system is very extensive: every day more than 1.3 million people commute to the Argentine capital. These suburban trains operate between 4 am and 1 am. The Buenos Aires commuter rail network also connects the city with long-distance rail services to Rosario and Córdoba, among other metropolitan areas. The city center is home to four principal terminals for both long-distance and local passenger services: Constitucion, Retiro, Federico Lacroze and Once. In addition, Buenos Aires station serves as a minor terminus.

Commuter rail in the city is mostly operated by the state-owned Trenes Argentinos, though the Urquiza Line and Belgrano Norte Line are operated by private companies Metrovías and Ferrovías respectively. All services had been operated by Ferrocarriles Argentinos until the company's privatization in 1993, and were then operated by a series of private companies until the lines were put back under state control following a series of high-profile accidents.

Since 2013, there has been a series of large investments on the network, with all lines (with the exception of the Urquiza Line) receiving new rolling stock, along with widespread infrastructure improvements, track replacement, electrification work, refurbishments of stations and building entirely new stations. Similarly, almost all level crossings have been replaced by underpasses and overpasses in the city, with plans to replace all of them in the near future. One of the most major projects under way is the electrification of the remaining segments of the Roca Line – the most widely used in the network – and also moving the entire section of the Sarmiento Line which runs through the heart of the city's underground to allow for better frequencies on the line and reduce congestion above ground.

There are also three other major projects on the table. The first would elevate a large segment of the San Martín Line which runs through the city center and electrify the line, while the second would see the electrification and extension of the Belgrano Sur Line to Constitucion station in the city center. If these two projects are completed, then the Belgrano Norte Line would be the only diesel line to run through the city. The third and most ambitious is to build a series of tunnels between three of the city's railway terminals with a large underground central station underneath the Obelisk, connecting all the commuter railway lines in a network dubbed the Red de Expresos Regionales.

Buenos Aires had an extensive tram system with over 857 km (533 mi) of track, which was dismantled during the 1960s after the advent of bus transportation, but surface rail transport has made a small comeback in some parts of the city. The PreMetro or Line E2 is a 7.4 km (4.6 mi) light rail line that connects with Underground Line E at Plaza de los Virreyes station and runs to General Savio and Centro Cívico. It is operated by Metrovías. The official inauguration took place on 27 August 1987. A 2 km (1.2 mi) long modern tramway, the Tranvía del Este, opened in 2007 in the Puerto Madero district, initially using two tramcars on temporary loan from Mulhouse, then later a tramcar from Madrid. However, plans to extend the line and acquire a fleet of trams did not come to fruition, and declining patronage led to the line's closure in October 2012. A heritage streetcar maintained by tram fans operates on weekends, near the Primera Junta line A Underground station in the neighborhood of Caballito.
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