Mexico City Metro Line 12

1985 plan for the Mexico City Metro with the earlier project for Line 12.

In the eighties, the Comisión de Vialidad y Transporte Urbano (COVITUR), an organization of the Departamento del Distrito Federal, presented a plan for the Mexico City Metro based on several studies and reports related to the rapid growth of the city and its demand for public transportation. On the so called Programa Maestro del Metro (Metro Master Plan), COVITUR considered a metro line that would run on the southern part of Mexico City from west to east, the line was designated as Line 12.[7]

This line would run from Álvaro Obregón to the west to Constitución de 1917 in Iztapalapa to the east. It would have seventeen stations and a length of 18.97 km and it would connect with Lines 2, 4, 3, 7 and 13, another planned line.[7]

By the 1990s no Line 12 was built. But in 1996, the Sistema de Transporte Colectivo published its plan for the next 25 years, the Plan Maestro del Metro y Trenes Ligero (Metro and Light Rail Master Plan). This document considered the new demand for public transport as well as the urban expansion towards the suburbs and the State of Mexico. Line 12 again appeared in the plan, with some changes, but the route was almost the same.[8]

The 1996 Line 12 project would start in Santa Lucía in Álvaro Obregón and end at a station called Francisco del Paso in Iztacalco. The idea was that both Line 8 and Line 12 would share Francisco del Paso as a transfer station; then, the stretch of Line 8 going from this new station to Constitución de 1917 would be transferred to Line 12, while Line 8 would have a new expansion from Francisco del Paso to the south in Tlalpan. Therefore, Line 12 would have almost the same route that in the 1985 plan, from Álvaro Obregón to Constitución de 1917.[8] None of these projects materialized and Line 12 was not mentioned again until the new century.

In December 2006, the possible construction of a new metro line to satisfy the demand for public transportation in the south of Mexico City was announced, taking in consideration Line 12's original plans. Mexico City's government announced a query among its citizens to choose between two routes. The line would go from Mixcoac to Iztapalapa; from there, there were two choices: Iztapalapa–Acoxpa or Iztapalapa–Tláhuac.[9]

The winning route was Iztapalapa–Tláhuac. Back then, Tláhuac, one of the easternmost Mexico City boroughs, did not have metro service. The new route followed almost the same plan for 1985's Line 11 from Culhuacán to Periférico Oriente (almost all station's name changed); except from the fact that this line was projected to end in Iztapalapa and not in Tláhuac.[7]

On 8 August 2007 the project was officially presented as Línea 12: línea dorada, la línea del Bicentenario (Line 12: Golden Line, the Bicentennial Line) and, thus, its chosen distinctive color was golden.[10]

Construction of the elevated viaduct stretch of Line 12 on Avenida Tláhuac

Construction of the first leg of the line, Tláhuac–Atlalilco, started on 23 September 2008.[11] The second stretch of the line, from Atlalilco to Mixcoac was finished on April 2012.

The line was inaugurated on 30 October 2012 by Marcelo Ebrard, Head of Government of the Federal District from 2006 to 2012 and Felipe Calderón, President of Mexico from 2006 to 2012.[12]

In an unprecedented event in the history of Mexico City Metro, Line 12 had to be shut down temporarily in the stretch Tláhuac–Atlalilco due to severe faults in its infrastructure. This section is the one that corresponds to the elevated stretch of the line.[13]

The technical and structural faults of the elevated stretch caused the trains to run on the verge of derailment, due to wear on the rails that provoked slopes and damage to the tires of the trains, putting six out of the 30 trains out of service.[13]

The stretch was closed between 12 March 2014 and 29 November 2015, when the section going from Tezonco to Tláhuac was officially reopened by Miguel Ángel Mancera, Head of Government of the Federal District from 2012 to 2018.[14][15] Previously, on October 27, 2015, the stretch Periférico Oriente–Culhuacán, resumed the service, but all trains stopped at Periférico Oriente station till the service on the whole line was reestablished.[16]

On 19 September 2017 a 7.1 magnitude earthquake hit Mexico City and other zones of Central Mexico, affecting Line 12 with electrical power shortages and the derailing of a train between the Nopalera and Zapotitlán stations.[17] Due to this, and potential damages to the line's infrastructure, service in the Tláhuac–Culhuacán section of the line was suspended.[18]

After evaluations, it was determined that the line had visible damages in the tracks and structural faults.[19] Therefore, the stretch from Olivos to Tláhuac was closed for repairs. Service in all the closed stations was resumed on 30 October 2017.[20]

Construction works of the western expansion of Line 12

In 2017 an expansion for Line 12 was announced. Construction started on 29 November 2017.[21][22] The extension was expected to be completed by 2020, but works were delayed, thus, being projected to open by 2021.[23]

This project will extend the line from Mixcoac to Observatorio, where it will connect with Line 1 and it will have three new stations and a length of 3.5 km. The two new stations are Valentín Campa and Álvaro Obregón, both situated in the Álvaro Obregón municipality. The totality of the extension is being constructed underground.

The original 1985 and 1996 plans for Line 12 considered the line going westward from Mixcoac with two new stations, as in the undergoing expansion. Nevertheless, the connection with Line 1 at Observatorio was not planned in the projects.[7][8]