DC drive units have a minimum continuous speed. Go slower than that, you not only stall, but you melt the traction motors too. In addition, the SD45s derated to 3000 hp at 10 mph. Best bet - put enough power on the train to keep it moving at 12 mph+ even if a unit (or two, or three ...) goes down. Another problem is that beginning about the Super Series era, DC locomotives will now derate themselves once the traction motors get too warm. You may hit the hill at the bottom going fast enough, but once the motors heat up ....

AC drive units do not have a real minimum speed, so burning them up is not an issue. 2 mph or 2 mph - they will still try to pull.

Also, the trains are getting HUGE. 10,000 tons is nothing, 16,000 is not unusual. If anything goes down, there isn't a helper crew or rear end crew to resolve any issues. A DPU failure can lead to a situation where the train can't safely continue without exceeding the dynamic limits of keeping the train intact and upright on the rail.

This really stinks of modern management.


1. All accidents are preventable. (Translation - It must be an employee's fault. The only acceptable accident rate is zero, but realisticaly - sometimes it just happens.)

2. We can ignore the rules of physics. (If gravity, friction and velocity prevail, see rule 1.)

3. If the train stalls, what did the train crew do wrong?

4. And how many qualified MOP's are available?

5. "Unstoppable" - Can we sue this as a management training film?

:-)