I was astonished to learn in a post above that it is possible to derail an Amtrak train by the engineer applying full emergency brakes. This seems like a major design flaw?
Ed
Lock up the brakes on your car at 100mph and see what happens.
I think a more apt, though perhaps less relevant analogy is - lock up the brakes of a tractor-trailer at 100 MPH and see what happens. The risk of derailment stems from the fact that when the engineer dumps the brake pressure, the coaches slam forward into a declerating locomotive.
But wait, you say, the coaches have brakes too, and they are connected to the locomotive. Yes, but it takes a certain amount of time for the decreasing pressure to travel all the way back to the last coach. So the front cars start slowing before the back cars do. Now this all happens very quickly, but the resulting forces in the train can cause it to jump the tracks.
The solution to this is to use electrically controlled pneumatic brakes, in which the signal to brake travels via an electrical wire that spans the length of the train. Since the electrical signal transmits nearly instantly, all the brakes apply uniformly. But ECP brakes are very new technology and only a handful of trains in the US have them - each car needs to be equipped with ECP technology for the system to work. The Amfleets, and all of Amtrak's fleet, were created long before it.
Now it's worth noting that the above described effects are much more pronounced with freight trains, I'm not sure how much an Amtrak train would be affected by them.