UP/BNSF Crossing Incident Collapses Highway Bridge

[nkalanaga]

draskouasshat:  Thank you.  I'll also add, from the operating side, that there is a specific rule that says that an improperly displayed signal, or a signal not displayed where it should be, is to be considered the most restrictive indication possible on that signal.  In most cases, that would be an absolute STOP.  So, unless the signal failure caused a CLEAR or APPROACH, even a failure should stop the train, not cause a collision.  The system, and the rules, are designed to be failsafe and foolproof, but nothing is perfect.

[C855B]

NTSB preliminary report issued today: http://www.ntsb.gov/investigations/2013/scott_city_mo/Chaffee_MO_10-Day_Preliminary%20Report_20130607.pdf

Short version - the UP train ran the red.

[Specter3]

49mph and only 11 cars derailed? That seems to be a low number given the velocity. Maybe a lot of empties on UP.

 How many preceeding signals would be in some sort of restricted form given that there was a stop at the crossing?

[nkalanaga]

There should be at least one, showing "Approach", and might be more.  At a small interlocking like this one I doubt that they'd have an "Advance Approach", but they might.

And, unless the rules have changed, or there was a signal malfunction and the crew didn't get the Approach indication, 49 MPH was too fast.  From the 1967 "Consolidated Code of Operating Rules", which the UP used:

Approach:  "Proceed prepared to stop before any part of train or engine passes the next signal.  Trains exceeding 40 MPH must immediately reduce to that speed."

In the same book, the NP, SP&S, and CB&Q have their own signals sections, and don't specify a maximum speed for passing an "Approach" indication.  They just say "Proceed prepared to stop before any part of train or engine passes the next signal."

The Frisco and MP didn't use this book, so I have no idea what their rules would have been in 1967.

[jagged ben]

I think that "Approach" these days is 30mph.   

(It was in 1988.   http://www.lundsten.dk/us_signaling/aspects_up1988/index.html)

[draskouasshat]

There should be at least one, showing "Approach", and might be more.  At a small interlocking like this one I doubt that they'd have an "Advance Approach", but they might.

And, unless the rules have changed, or there was a signal malfunction and the crew didn't get the Approach indication, 49 MPH was too fast.  From the 1967 "Consolidated Code of Operating Rules", which the UP used:

Approach:  "Proceed prepared to stop before any part of train or engine passes the next signal.  Trains exceeding 40 MPH must immediately reduce to that speed."

In the same book, the NP, SP&S, and CB&Q have their own signals sections, and don't specify a maximum speed for passing an "Approach" indication.  They just say "Proceed prepared to stop before any part of train or engine passes the next signal."

The Frisco and MP didn't use this book, so I have no idea what their rules would have been in 1967.

The size of the interlocker has absolutely no baring what so ever on how the approach signals are. If its signaled territory, it depends on many variables like train size, train weight, train speed, braking distance, curves, bridges and all sorts of crap. The number of signals showing a need to slow a train could be up to 3 blocks back. IE green, then a flashing yellow, then a yellow, and then red at the interlocking. If its dark territory, it might only be a distant signal that always displays yellow. Or you could have an extra holding signal in there if theres a town or crossings, it gets even more complicated. Theres alot more to a signal system than people have any clue about. A GCOR rule book also has nothing to do with how a signal system works, it only tells you what to do for a certain signal.

[C855B]

Yes. ^^^. Without firsthand knowledge of the location, guessing aspects is going to be a crapshoot. The signal placements are slightly unusual, with a signal controlling a siding exit about 1000' from the signal at the diamond. This could be a case of non-usual aspects up to and including a Restricting at the westbound (east-facing) signal at that siding exit. Otherwise, this is non-challenging railroading - no grades or curves of consequence, in a rural area.

But more directly addressing Spectre3's question, my edu-guess is after looking at placements there would have been at least two signals before the Stop that were likely to have been displaying something other than Clear.

We mere mortals will have to wait for the full report.

[nkalanaga]

draskouasshat:  All true, which is why I hedged my comments.  The best I could give for an answer was the minimum standards, and the definition of "Approach".

Incidentally, my old rulebook does have the flashing yellow "Advance Approach" you mentioned, although I've never actually seen one.  The only interlocking I had much contact with was the Pasco NP/SP&S junction, which had either yard trackage or a drawbridge on all approaches, so train speeds were limited to start with.

The NP, and BN in the 70s, had an interesting signal setup on the north (Spokane) approach.  The mainline first met the hump leads, then ran the length of the Pasco yard, before finally reaching the junction/passenger station/engine terminal.  The remote signal was just east (north) of Glade Crossing, and until sometime after 1978, was simply a pair of plain semaphore signals.  The eastbound signal was a standard ABS signal, but the westbound signal was manually controlled by the retarder operator at the Pasco yard.  It was always set for stop, and was an absolute signal, meaning "stop and sit there until told to move".  Westbound trains would call the tower by radio, as they passed the preceding "Approach" indication, and ask to have the signal cleared.  The main reason was to prevent through trains from colliding with yard movements, without requiring them to slow to restricted speed within yard limits.  If the main was clear, the operator would clear the signal, before the train reached it, and the train wouldn't have to slow until they approached the actual junction/station area.  If there was yard activity fouling the main, the train would have to stop, then proceed under yard rules.  The NP apparently didn't use "Advance Approach" on block signals, at least in eastern Washington, so there was none at Glade.

It also had an unintended use.  The track was on a curve, cutting through a large pile of sand just north of the crossing, with no visibility.  The crossing had lights, but on the infrequent occasions that it rained enough to soak the ties, they often shorted out and stuck on.  One could look at the signal and, if it showed stop, or if the eastbound signal was clear, be reasonably sure it was safe to cross the track.  They've now replaced the semaphores and removed the sand, so one can see the trains but not read the signals.