It seems to have already been covered, but to put it simply...whether a train is being pulled or pushed by a heavy locomotive, all it takes is one car to derail and dig into the dirt to cause a catastrophic wreck, and any cars trailing behind that one derailed car will pile up on top of the first one, even if the brakes apply in emergency. All the emergency brakes do is squeeze the wheels a bit tighter than a regular brake application. Then, since the wheels are being slowed down on the steel rails, it will still take a little while for the cars to be brought to a stop. A car still on rails with an emergency application will take a lot longer to slow down than a car that is off the rails digging into the dirt. Look at any freight derailment on main track. It almost always results in jackknifed cars piled up on top of eachother. And, I don't recall ever seeing a freight train being led by a freight car with the engines on the back, other than switching movements.
This video shows a train where the first few cars were derailed by a tornado. Once the first few cars derailed, the brakepipe had to separate initiating an emergency brake application trainline, but yet the rest of the train keeps coming and the cars pile up. https://www.youtube.com/watch?v=LYubpuIe3cw" onclick="window.open(this.href);return false;
This video shows a train where the first few cars were derailed by a tornado. Once the first few cars derailed, the brakepipe had to separate initiating an emergency brake application trainline, but yet the rest of the train keeps coming and the cars pile up. https://www.youtube.com/watch?v=LYubpuIe3cw" onclick="window.open(this.href);return false;
