The 24.5km line, which connects Mixcoac with Tláhuac, opened on October 30 2012, but the 11 stations were closed in March 2014 following the discovery of serious track defects which nearly caused the derailment of a train.
The rehabilitation work carried out by the Ministry of Works and Services (SOBSE) was divided into two phases. The first phase involved the replacement of ballast on straight sections and curves with a radius exceeding 550m and the installation of nylon devices to reduce vibration. In the second phase curves with a radius of less than 550m were rehabilitated, and all track elements were replaced in 16 curves. The repairs were certified by Systra and TÜV Rheinland.
According to the comptroller of the Federal District of Mexico City, Mr Eduardo Rovelo, inquiries into the poor construction of the track have led to the implication of 46 people, 12 of whom now face legal proceedings.
Five of the closed stations were reopened a month ago with the remaining six being reopened on November 29 by Mexico City's mayor Mr Migeul Angel Mancera who said: "we will give a guarantee that this will line not be closed again, and the maintenance will be thorough and comprehensive." The mayor has awarded a three-year contract worth Pesos 150m ($US 9m) to maintain Line 12.
A 3.9km extension to Line 12 is currently under construction from Mixcoac west to an interchange with Line 1 at Observatorio.