Mexico City Metro overpass collapse

Mexico City Metro overpass collapse
Investigators on site the night of the collapse
Details
Date	3 May 2021; 3 years ago (2021-05-03) 22:22 CDT (UTC-5)
Location	Tezonco–Olivos elevated interstation Tláhuac Avenue, Tláhuac, Mexico City
Coordinates	19°18′18″N 99°03′41″W / 19.3049°N 99.0613°W / 19.3049; -99.0613
Country	Mexico
Line	Line 12
Operator	Sistema de Transporte Colectivo (STC)
Incident type	Railway collapse
Cause	Lack of functional studs and poor welds that led to fatigue in the collapse point
Statistics
Trains	1
Vehicles	1
Crew	1[2]
Deaths	26[1]
Injured	98[1]

On 3 May 2021, at 22:22 CDT (UTC−5), a girder overpass in the borough of Tláhuac carrying Line 12 of the Mexico City Metro collapsed beneath a passing train. The overpass, along with the last two railcars of the train, fell onto Avenida Tláhuac near Olivos station, resulting in 26 fatalities and 98 injuries. It was the deadliest accident in the Metro's history in nearly fifty years.

Before the line opened, it faced technical and structural issues that persisted during its operation, resulting in a partial closure of the elevated section where the accident occurred, lasting from 2014 to 2015. An earthquake in 2017 further damaged the structure; although repairs were completed within a few months, residents reported that problems persisted for years. Originally announced in 2007 as an underground line capable of operating rubber-tired trains due to the instability of the city's soil, the line was scheduled to open in 2010. However, budget and time constraints led to modifications that allowed underground and above-ground operation with steel-wheeled trains. Researchers have identified this design change as a factor in track instability and damage since the line commenced operations. The construction was carried out by Empresas ICA, in partnership with Alstom Mexicana and Grupo Carso, the latter owned by businessman Carlos Slim.

Claudia Sheinbaum, the mayor of the city at the time of the collapse, hired the Norwegian risk management firm Det Norske Veritas (DNV) to investigate the causes of the event. Preliminary findings indicated that the accident was linked to bridge construction deficiencies, including a lack of functional studs and poor-quality welds, fatiguing the collapsed beam. Further investigations concluded that the bridge was designed and built without adhering to quality standards, that both the construction and the line's design changes were inadequately supervised, and that there were insufficient fixing and safety elements. Additionally, it was found that periodic maintenance checks, which could have detected the girder buckling, had not been conducted—a claim contested by the city government.

Carso, the company responsible for constructing the collapsed section, denied any wrongdoing; however, Slim agreed with the Mexican government to repair the section at no cost. In December 2021, the city's attorney general's office filed charges against ten former officials involved in the construction and supervision of the project, including the project director, Enrique Horcasitas. As of October 2024, they were awaiting trial for manslaughter, injury, and property damage.