[Ez2BRepub]

The speed is the answer Well, yes. Once we knew the speed it eliminated bombs, derailing by external means, debris - a host of other externals. The thing that now needs to be determined is how that (speed) occurred - intentional, accidental, or catastrophic failure of equipment...

The two questions that come to my mind when I think about it being mechanical failure.

1) Why did he not call this out over the radio to dispatch/other trains to let them know of a possible runaway train? He seemed to have plenty of time to do so before the crash

2) If it was a system failure that caused it to speed up on its own, why did he not hit the emergency brakes when he first noticed it happening? We know they worked, since he hit them at the curve.

[NoCmpromiz]

two questions that come to my mind when I think about it being mechanical failure.

Yes, those are good questions, and the absence of that response you mention fuels the speculations of operator inattention/intentional activity/incompetence/whatever.

But we can't prove that yet...

[mellow velo]

Those were my thoughts as I was reading the several posts above yours. If it was an electronic failure that caused the train to accelerate, in the 45 (or 60 seconds) prior to the crash, there certainly would've been a few "Oh, sh!t"s or even "mayday"s (do they still say that?) uttered over the airwaves.

If not, then it would seem like the engineer calmly accelerated with intent to do harm, not unlike how that French co-pilot calmly descended that Germanwings Airbus into the Alps a few months back.