One factor left out of the discussion is that the train was about 30 minutes late.

Also, there should be an inward facing camera on the loco.

In the photo of the curve, the sign says "T-30, P-30". "P" is for passenger. What is "T"?

Where does that 30 mph zone begin?

The T is for Talgo in this case, P being for other types of Passenger car.
They are obviously both the same limit at this point, but can vary elsewhere on the route.

I took this photo at Vader, WA, in June this year which shows the different speeds for Talgo (65), Passenger (55) & Freight (50)......

CNN has already solved it, says the train was "going too fast"

PTC would have prevented this derailment. Speed caused it.

With PTC, the engineer inputs information off his paperwork (track bulletins, train orders, or whatever you call it...) and the onboard system is then programmed to know the limits of the trains authority, any slow orders (whether they be temporary, or permanent like this curve would be) and would also be able to tell from indications in lineside signalling if there was a train close ahead of them.

PTC is evidently very costly, and not all railroads are wont to spend the money to install it. UP was loudly complaining that they needed an extension of the length of time they had to comply with installing it system wide.

There have been numerous problems with the implementation of PTC, most notably the ever-increasing lag time between the demanded implementation date(s) and the ability of the technical providers to develop and perfect it. People in the industry I've talked to have described the whole process as "like trying to nail jelly to the wall."

Meanwhile, the best estimates I have seen with regards to return on investment in PTC indicate that the costs of the industry-wide implementation are running about ten times the anticipated return on investment in prevented crashes, damages, etc. This, of course, neatly side-steps the perpetual "But if it saves just one life, isn't it worth it??" emotional rationalization.

In this specific case, however, we appear to have a case of PTC having already been installed but not active at the time of the accident. IF that is the case, someone's "gotta lotta 'splainin' to do!!" as Ricky Ricardo was wont to say...........

UPDATE:

Does anyone know for sure if the train was being pushed or pulled?

In the photo posted on the previous page, there does appear to be some damage to the tops of the rails just next to the backwards-facing trackside sign - within the curve.

If you think that was a mistake, I have a bridge to sell you.



ATS is effective, at a small fraction of the cost of PTC.



PTC has been a bad idea from day one. Although it possible on paper, I believe it will become the next ACI: a massive investment in a failed technology. The railroads spent over $600 million in today's money on the ACI system, difference this time is the government mandate!

EDITED TO ADD:
It should be noted that existing ATS installations (NEC) are acceptable under the PTC mandate, but new ones are not! For whatever reason, it was decided to force the railroads to use billion-dollar technology when million-dollar technology is more than adequate.

CD

In regards to the argument as to whether or not PTC offers any value to enforcing speed compliance, I'm just going to leave this one right here:

https://www.ntsb.gov/investigations/AccidentReports/Pages/DCA17FR008-preliminary.aspx

they will have to do an accurate simulation on this, you can trace the ended up cars positions and run that backwards and you will find the start of the accident point.
The moment the lead engine derailed it slowed and this started the pushing of the rear cars.
Anybody have Trainz handy?

Lots of Monday morning quarterbacking going on, I think I will wait to see what the NTSB has to say.

My thoughts, too.

The level of ignorance displayed in the popular news media and in YouTube comments is astounding. Even those who equate the Mayor's comments [about grade crossing safety concerns] with this accident [a derailment far from any grade crossing] shows that.

I have seen at least three media reports, one from a railroad-focused source and not mass media, stating that the front-end SC44 Charger (that ended up on the roadway) was the sole motive power, and that the P42 was in idle just "along for the ride," so to speak.