[editor-surveyor]

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Oh yea! - That critical 2 MPH made the difference!

[Paladin2]

"The train was going 81.1 mph moments before the derailment, according to transitdocs.com, a website that maps Amtrak train locations and speeds using data from the railroad's train tracker app."

Those speeds are only updated to the web on ~4 minute interval.

Looking at the TV coverage, the track has been recently upgraded compared to satellite pics from map websites. I note that the track is aligned so the curve continues across the bridge (The bridge was originally setup with 2 tracks/). With appropriate banking both could allow significant speed. It also looks like the Loco down on I-5 is a power unit.