Western Railroad Discussion > Semaphore Saturday Anyone?

Amtrak # 3 is running on time to the minute just west of Lamy, New Mexico on March 21, 2020.  It is just about to roll over the eastbound ATS inductor connected to semaphore signal 8402.    

Note that this signal is unusual in that it stands all by its lonesome, lacking a sister signal adjacent to it on the other side of the track.    This represents a very early signal installation, originally installed as Opposing Overlap ABS between Domingo and Lamy in 1923.  Opposing Overlap is a system that pre-dated the modern Absolute-Permissive ABS systems we have today.  Santa Fe did not incorporate the Absolute-Permissive system into its new signal installations until 1926.  With the Opposing Overlap system, opposing signals were staggered apart by half-a-mile, thus lacking the familiar side by side, back to back 'flat pair' signalling we are normally used to.    Here, the westbound 8401 signal is just under a half-mile behind the train.  Why staggered like this?   Since Opposing Overlap did not consist of an 'Absolute' signals,  it was technically possible for two trains to be sent toward each other on a collission course. The signals were staggered like this to provide two opposing trains a buffer space to come to a stop, preventing a head-on collission, in the situation where one or both trains could miss seeing an Approach aspect , triggered by the opposing train, by mere seconds.  This means the next signal the train crew would see is a red signal staring them in the face at high-speed.    Of course, Santa Fe later modified this signal system into an Absolute-Permissive system, but the staggered signal locations remained as did the semaphores.  



Edited 1 time(s). Last edit at 03/21/20 20:57 by CompanyNotch.

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Interesting, thanks for the technical history lesson.

Posted from iPhone

CompanyNotch Wrote:

>  Santa Fe did not incorporate the
> Absolute-Permissive system into its new signal
> installations until 1926. 

The Santa Fe was strictly overlap until re-signaling projects during the 1960s. T.S Stevens, Santa Fe's Chief Signal Engineer 1909-1939 (?), preferred overlap to APB during his tenure. The APB that presently graces the line from Rowe to Springer was done sometime in the late 1950s or early 1960s. Along with eliminating sidings and lengthening others, the signals were respaced and wired in the APB scheme.

Also, my notes indicate that Lamy to Domingo had signals installed in 1923 -- 28.5 miles, 55 T-2s; primary battery, polar track relays.

Nevertheless, it's a nothing short of a miracle that semaphores are still in service and your wonderful photo captures it nicely. 

You are right - a typo on my part. This segment was installed in 1923, as was Gise to Fox that same year. Domingo to Hahn occured in 1924. However, I believe Santa Fe began installing APB in 1926 with installations such as Abajo-Isleta. I think these were not staggered installations, but rather flat pairs.

Posted from Android

I see what you mean though, in that even the Flat Pairs when installed would have had number number plates on the siding signals.

Fascinating!  And note the ATS pick-up down by the tracks--bonus photo feature!  We shold have gone with that today, vs. PTC.

Nice!  I've often considered a trip to get those individual blades west of Lamy, but they're so far out in the middle of nowhere!  And it looks like most of them are a good hike off the road, perhaps involving private property, and only 2 trains a day, with no possibility of chasing.  I just can't seem to justify it.

So thanks for sharing this one!

Andy

I remember those lap signals on the Lampassas (Texas) sub.  Always thought them odd since no other road in Texas used them.  Thanks for the explanation.

Thank you all. Andy,you are so correct. They do involve a good hike, especially for one train. I justify it to get the excercise. I wish I would have focused on these back when freights still roamed the line.

I do need to adjust what I said about the staggered signals shown versus traditional back to back flat pairs. I think the difference was that the staggered overlap did not contain the 'tumble-down' design between sidings yo protect movements between sidings. The later Flat Pairs did, thus behaving like an Absolute Permissive system, although technically the siding signals were also permissive as were the intermediates as mentioned above. The Tumble Down protection feature between sidings is what eliminated the need for the staggered signals and 'buffer' space.

coach Wrote:
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> We shold have
> gone with that today, vs. PTC.

Cost wise, it's a bargin, but PTC is better than the ATSF's ATS system could ever be.

CompanyNotch Wrote:
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> However, I believe Santa Fe began installing APB
> in 1926 with installations such as Abajo-Isleta.
> I think these were not staggered installations,
> but rather flat pairs.

This is incorrect as well. Track charts corrected to 1960 show the stretch as being staggard, which was consistent with Santa Fe overlap. This stretch was converted to CTC between Abajo and Isleta in about 1960 and the interlocking was removed at both locations. If you're thinking the stretch is APB because the signals are paired, at what time frame are you speaking about? Throughout the history of railroad signaling, railroads make constant changes to suit new conditions. 

There is no evidence of APB on any ABS installation on the Santa Fe in 1926 or into the 1930s. The 1930 CTC installation between Dodge City and Kinsley, KS  is a form of APB (CTC is more or less APB with controlled absolutes at the siding). APB was introduce by GRS's S.N. Wright in 1911 and was first installed on the TH&B, so it was well known when Stevens was leading the Signal Department of the Santa Fe in the 20s. As far as we know, his positon was the overlap system suited the needs of the ATSF as opposed to APB. During the 20s, some railroads prefered overlap to APB for various reasons (cost not just being one of them).

Also, just because signals are paired in ABS doesn't necessarily mean they are wired in the APB scheme. A perfect example is the SP (Pacific Lines), which always was a an overlap railroad save for isolated stretches (Montalvo to Ventura, CA; Hayden to Ray Jct, AZ) , and the vast majority of its signals were paired.

Thats why I corrected myself in the above post.  You are right, Flat Pair was not Absolute Permissive, but the Flat Pair became the version that I equate with the more modern design Absolute Permissive, in that it included the 'tumble down' feature to protect trains between sidings.  The old staggered overlap did not do this.  Yes, Abajo to Isleta was CTC'd in 1959, the same year that Lamy to Rowe was CTC'd (poor man's CTC).  I stand corrected then that Abajo to Isleta was also staggered, if the maps showed that.  

CompanyNotch Wrote:
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> I stand corrected then that Abajo to Isleta was also
> staggered, if the maps showed that.  

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CompanyNotch Wrote:
-------------------------------------------------------
> Amtrak # 3 is running on time to the minute just
> west of Lamy, New Mexico on March 21, 2020.  It
> is just about to roll over the eastbound ATS
> inductor connected to semaphore signal 8402.  
>  
>
> Note that this signal is unusual in that it stands
> all by its lonesome, lacking a sister signal
> adjacent to it on the other side of the track.  
>  This represents a very early signal
> installation, originally installed as Opposing
> Overlap ABS between Domingo and Lamy in 1923.
>  Opposing Overlap is a system that pre-dated the
> modern Absolute-Permissive ABS systems we have
> today.  Santa Fe did not incorporate the
> Absolute-Permissive system into its new signal
> installations until 1926.  With the Opposing
> Overlap system, opposing signals were staggered
> apart by half-a-mile, thus lacking the familiar
> side by side, back to back 'flat pair' signalling
> we are normally used to.    Here, the westbound
> 8401 signal is just under a half-mile behind the
> train.  Why staggered like this?   Since
> Opposing Overlap did not consist of an 'Absolute'
> signals,  it was technically possible for two
> trains to be sent toward each other on a
> collission course. The signals were staggered like
> this to provide two opposing trains a buffer space
> to come to a stop, preventing a head-on
> collission, in the situation where one or both
> trains could miss seeing an Approach aspect ,
> triggered by the opposing train, by mere seconds.
>  This means the next signal the train crew would
> see is a red signal staring them in the face at
> high-speed.    Of course, Santa Fe later
> modified this signal system into an
> Absolute-Permissive system, but the staggered
> signal locations remained as did the semaphores.
>  

The overlap signals are similar to the Santa Fe Second District of the Los Angeles Division a.k.a the Pasadena Subdivision in later years. The second district Incorporated "staggard" searchlight and color light signals all the way to Los Angeles from San Bernardino approximately 70 miles when the second district was a through route. I think the Pasadena Subdivion is still absolute-permisive at least what is left of it. Interesting.

SantaFeRuss