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Reply to "NS Derailment in PA"

Redshirt214 posted:

So, in terms of operations at restricted speed, are trains operating too slowly for PTC to kick in?

No, that's not the issue in play here. The problem in this situation is that even if the PTC system was active and working, it could not know where the REAR of the preceding train is. The system has to rely on the ENGINEER (remember him?) to comply with RESTRICTED SPEED operating rules.

What exactly is "Restricted Speed?" It is a speed not to exceed 15 or 20 mph (depending on the railroad) that will allow an engineer to stop his train within half the range of vision. How far is that? It depends. I have run trains in fog where the visibility was only about 400 feet. That required me to run at walking speed in order to be able to stop within half the range of my vision.

The same holds true on a curve. If you are running a long straight stretch of track under restricted speed and you can see a mile ahead of you, then 15 or 20 mph is fine. But when you get to a curve that is lined with trees on both sides of the track, what  do you do? You may only be able to see 5 or 10 car lengths ahead of you in the curve. If you can only see 5 car lengths ahead of you, you have to be able to stop in 2-1/2 car lengths! 15 mph in that situation ain't gonna cut it. 2 or 3 mph would be about right for 5 cars visibility ahead.

...My understanding is that PTC is supposed to activate the breaks if a signal is past at red.

The train did not pass a RED signal. It passed a RESTRICTING signal. There is a difference. The brakes (not "breaks") would not automatically apply when passing a Restricting signal because the Restricting aspect does not require you to stop.

Last edited by Rich Melvin

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