Amtrak derailment, Sept. 25, 2021, near Joplin, Montana, US

[Astronuc]

AP News - Bent track a factor in Montana Amtrak crash that killed 3
https://apnews.com/article/national...na-accidents-1cb90e5e3c13c55dd5b94a8f39675dbe

HELENA, Mont. (AP) — Investigators probing a fatal 2021 Amtrak derailment in Montana disclosed Tuesday that the railroad track was bent along a curve near the accident site, and the problem got worse as freight trains traveled over the area before the crash.

Details on the bent track were included in hundreds of pages of investigative documents released by the National Transportation Safety Board. The three passengers who died and two who were seriously injured were in, or had just been in, an observation car that ended up on its side, the investigation found.

NTSB opens docket
https://www.ntsb.gov/news/press-releases/Pages/NR20230221.aspx

NTSB investigation report (Ongoing investigation)
https://www.ntsb.gov/investigations/Pages/RRD21MR017.aspx

In-cab camera/video caught a slight distortion in the track ahead of the lead locomotive.
https://www.trains.com/trn/news-rev...track-defect-before-fatal-montana-derailment/

Edit/update: In the trains.com article:

Another document, by the investigation’s human performance group, reports that neither crew of the preceding freight trains “noticed the misalignment or detected any unusual train movements while operating over the track defect.” The Amtrak engineer did also not see the misalignment, the report notes, while investigators, “who watched the video and were focused primarily on detecting the track deviation, were able to first see the misalignment only a couple seconds before the trains had traveled over it.”

In an interview conducted by investigators two day after the derailment, the train’s engineer said he had just sounded his horn for a private grade crossing, checked a signal, and checked his speed. “Once I did that, I looked back up,” he said. “I felt a big jerk to the right and then another jerk to the left, and then another jerk to the right. And then the accordion action started. Then the train went into emergency.”

It's hard to see the misalignment, especially if one is moving about 110 ft/s (34.4 m/s) or more. Very likely, the freight locomotives wouldn't feel it since they travel at much lower speed (~60 mph, or 88 ft/s or 16.7 ms/) or slower. It's also hard to see if the track gauge is changed (increased) as well.

 

[jedishrfu]

I guess sabotage is ruled out. Somehow the track got bent and continued use put it more and more out of alignment until the accident.