Mexico City Metro overpass collapse

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. However, budget and time constraints led to modifications that allowed underground and above-ground operation with steel-wheeled trains. 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 head of government 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 linked the accident to bridge construction deficiencies, including a lack of functional studs and faulty welds, fatiguing the collapsed beam. Researchers have identified the design change as a factor in track instability and damage since the line commenced operations. Further investigations concluded that the bridge had been designed and built without adhering to quality standards, that the line's construction and design changes had been 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 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. As of June 2025, they were awaiting trial for manslaughter, injury, and property damage. The bridge was rebuilt, the sections constructed by Carso were reinforced, and the line underwent general maintenance, fully reopening on 30 January 2024.