On 14 November 2015, a TGV train derailed in Eckwersheim, Alsace, France, while performing commissioning trials on the second phase of the LGV Est high-speed rail line, which was scheduled to open for commercial service five months later.

According to investigators, late braking, which led to the train entering the curve at excessive speed, was the immediate cause of the accident.

The scheduled opening of the second phase of the LGV Est for commercial service was delayed three months, from 3 April 2016 to 3 July 2016.

[12] The final weld of rails on the second phase occurred in March 2015, marking the completion of the line, although some work remained.

[13] At the time of the derailment, the line was scheduled to open for commercial service on 3 April 2016, following commissioning trials and training for operators.

[9]: 6–7  As the track begins a long, right-hand curve into the flying junction, it is on a raised embankment 5–8 m (16–26 ft) high[9]: 10  and bridges the Marne–Rhine Canal.

[9]: 10, 15  Violent transverse movements at the rear of the lead power car caused it to separate from the rest of the train.

[9]: 22 [15][17] At 15:05, the train disappeared from the approach zone for the Vendenheim junction on the display being monitored by staff at the signalling control center.

[9]: 7  At 15:10, the control center initiated emergency procedures for the loss of a train and closed the non-high-speed rail lines that pass through the Vendenheim junction.

[9]: 17  At approximately the same time, one of the companies involved in the construction of the line received a call from an employee aboard the train, who informed them of the derailment.

[19] The French Minister of Ecology, Sustainable Development and Energy, Ségolène Royal, and the Secretary of State for Transport, Alain Vidalies, travelled to the site shortly after the crash.

[21] The derailment resulted in 11 deaths, which included four employees of SNCF, five technicians from Systra, the engineering firm responsible for the tests, and two guests.

[5] Among the dead was the director of the LGV Est line for SNCF Réseau, which owns France's railroad infrastructure.

[1] SNCF began disciplinary proceedings and take punitive measures against employees responsible for, among other things, the "reckless presence" of children on the test train, presence of seven people in the cab, the lack of rigor in creating lists of those onboard and controlling access to the train, and "without doubt" the human errors in the cab.

The following day, a memorial service was held in the church in Mundolsheim, which was attended by SNCF President Guillaume Pepy.

[30] The scheduled opening of the second phase of the LGV Est for commercial service was delayed by three months, from 3 April to 3 July 2016.