If the cause was excessive speed - then why didn't the speed control system slow it down? Alertors by themselves don't prevent an engineer from doing something wrong, and don't always keep you awake.

A couple observations based on the TV coverage - How did the engine stay upright and substantially intact? What might have been the head passenger car basically disintegrated, and if I saw right the cars is actually twisted 180 degrees as the trucks appear to be on opposite sides of the wrecked car. One of the disadvantages of overhead cantenary is the car apparently tangled with the cantenary support structure which may explain in part how the car has so much damage. I'm thinking this was a high speed wreck exceeding the claimed 50 mph limit.

The news and witnesses continue to show the general ignorance of modern railroading. I've heard black boxes at each end of the train, can't differentiate between the engineer and conductor and cars made out of aluminum. They are obsessing over the need for seatbelts and flying luggage, and are claiming the train cars were torn apart - yet all but one car seems to be substantially intact and the survivability supports that.

Don't forget that I believe it was probably engineer only in the cab, and passenger trains are expected to operate on the edge as far as acceleration and deceleration. One could debate if the tightlock couplers were a hindrance or a help - do you try to keep the train intact and drag other cars over, or do you have the couplers disengage and let each car absorb its own energy with the chance of telescoping?