Quote:This makes sense. It was probably variety of the D-22-PTE system, and this system was far from controversial. All that was removed were the E features from the locomotives and cars, with the rest of the D-22 system (on the cars) remaining in place. Otherwise how could you stop the train? Removing the E features was a reduction in maintenance expsense thing, and the SP did it to trains 98/99 by the mid-1950s.
That sounds like the most likely scenario. Of course the intended advantage of the electro-pneumatic was simply to provide near instantaneous application through the entire consist, correct? For SP 98/99, I believe this allowed better running times because you wouldn't need to start as far back with a set, saving a little bit of time at each speed reduction.
I'm not familiar with the NP situation, but perhaps someone decided that running hot and counting on a quick set with the electro-pneumatic, which then failed, contributed to the accident. In reality though, you can't really call a failure of the electro-pneumatic a primary cause, if someone was running so hot and diving into a speed restriction such that the extra time to grab the automatic made the difference in causing a wreck.
BTW, the electro-pneumatic brakes on 98/99 was the purpose for one of the three dynamos on the SP 4400's.