Signaling System Rules

Automatic Block Territory

1. Automatic Block Signals (ABS) was the first type of automatic signaling that SP used on all mainlines. In overview, trains in ABS territory operated in full accordance with Timetable and Rulebook instructions, just as if no automatic signals were present. Timetable and train orders were the rule of the day. When the signals were originally installed they provided train crews with basic track "block" occupancy information in both directions of travel (reverse direction is "information only", as viewed by conductor at rear of train).
   

1. At places along the Coast Route (and possibly elsewhere) around the 1950s some sidings were guarded by a single pair of signals (one facing each direction) at each end of the double track. See http://tinyurl.com/y9h5y8b for a diagram about this. The switches were manually operated, weren't spring switches and this was not in CTC territory.
   

2. Kenneth Soward
   

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4. The signals know which way the switches were aligned. Each switch in Automatic Block Territory (ABS) had a U5 Switch Circuit Controller on it. If the switch was opened more than 1/4" from main line direction all signals governing movement over that switch would go to red.
   

5. Dennis Drury
   

6. Former Signal Maintainer
   

7. SP Coast and Western Divisions
   

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9. For an explanation of SP's ABS Signaling see:
   

10.                                                                                 http://www.lundsten.dk/us_signaling/abs_st_sp/index.html
    

11. Charlie Morrill
    

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13. While this site is good overall, there are errors in it. What is being described as ABS in one part is actually Automatic Permissive Block, or APB. This is the section where all opposing signals drop between sidings.
    

14. Dennis Drury
    

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Semaphores  (as explained by Dennis Drury, Former SP signalman)

1. It was necessary to do a complete signal upgrade with CTC. With CTC, the dispatcher only controls the absolute signals, which would, of necessity, require replacements to get red over green, etc. The intermediate signals simply provide safety indications as to the track ahead, not authorization to occupy the track.
   

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3. The advantage of a colorlight over a searchlight is a separate bulb for each aspect, and the inherent redundancies in such a design. But a blown green "bulb" in a colorlight still displays a "dark" aspect, which is the most restrictive of any aspect possible.
   

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5. Semaphores were used to provide signal indications for diverging  routes. The 1956 SP Book of Rules cover both searchlights and semaphores and clearly shows signals for diverging routes. For semaphores, the diverging route signals were two position (lowered - proceed on diverging route & horizontal - do not proceed on  diverging route) and two colors (i.e., green - proceed on diverging route, red - do not proceed on diverging route). The 1943 SP Book of Rules shows the same thing. Obviously, searchlight signals did the same thing but with lights only.
   

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7. Since the existing semaphore intermediate signals needed modifications to provide the additional approach aspect, it made fiscal sense to the SP to do a total retrofit at that time. Plus the lower maintenance and higher visibility provided by the searchlight made good sense for the retrofit.
   

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9. A semaphore-type signal could provide a diverging route indication. You need three semaphore blades to provide this. Three bladed signals were used on SP Lines at the entrance into a CTC controlled siding.
   

Rule 282

1. For Rule 282, using a two bladed semaphore for a diverging route indication is a double home signal that you can see used at interlockings. The double bladed signal that I have been referring to in my previous posts is a combination of a home and distant semaphore signal that was most commonly seen on mainline applications throughout the Western Lines. For the home over distant semaphore signal to be diverging you must add another semaphore home signal or searchlight below the double blades to get the diverging route aspect as shown in Rule 282 adjacent to the aspect that you refer to.
   

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3. Multiple photographs of two-bladed semaphores on the SP -- intermediate signals and signals controlling entry to passing sidings. OBVIOUSLY these have the ability to give a diverging route indication without the assistance of a third blade! A red over green plus the position of the blades is what the 1950's-1960 rule books show.
   

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5. It takes two lower quadrant semaphore blades to provide a "yellow" aspect. The upper "home" signal semaphore has two red and one green lenses. The lower or "distant" signal has one green and two yellow lenses. The intermediate signals are single blade "home" signals that could generate a "stop" red aspect and a "proceed" green aspect, that is it. The distant lower semaphore blade provided the "proceed at medium speed" or "yellow" aspect in combination with the upper blade.
   

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7. -Green or proceed: both arms lower quadrant, green over green lenses
   

8. -Yellow or proceed at medium speed:  upper arm lower quadrant, lower arm horizontal, green over yellow lenses
   

9. -Red or stop: both arms horizontal, red over yellow lenses
   

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11. Those are the three aspects possible with a two blade semaphore.
    

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13. The single blade home signal (red with blunt end and white stripe) can provide only two aspects, green and red. There is a third lens on the spectacle but that is the way they were used. Logic from the block ahead of the signal controlled this blade.
    

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15. To clarify the proper terminology, the "aspect" is the color the signal displays, and the "indication" is the railroad rule which is dictated by the "aspect". A green "aspect" has a proceed "indication".
    

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17. The distant blade lower signal (yellow with arrow trimmed end and black stripe) operated from logic gained from the block following the block ahead.
    

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19. If you look on my website photo SP32 shows a "proceed at medium speed" aspect.  SP39 shows "proceed" and "stop" aspects side by side with two, double blade signals.  SP31 shows an intermediate signal pair with "proceed" and "stop" aspects.
    

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21. The upper quadrant signals on the Cotton Belt could show 3 aspects on 1 signal with aspects at the 90, 45 and 0 degree positions. The lower quadrant signals used on the SP, could be positioned at only the lower quadrant and horizontal positions.  This enabled the most restrictive aspect to be generated if the coil was de-energized for any reason, such as malicious shunting or a broken rail. The semaphore was counter-weighted as such.
    

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23. Quite often the installation of CTC corresponded with a general signal respacing. As trains became heavier and faster, stopping distances increased. Since the distance between signals is calculated based on stopping distance it made sense to do the respacing when the signal gangs were in the area. Go wander around the railroad and you can sometimes see old Style B foundations where signals were removed.
    

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25. Interestingly, some of the definitions themselves refer to specific rule numbers as examples.  Let me try to describe the pictures in the 1943 rule book (and, indeed, the same pictures are in the 1960 rule book).
    

Rule 281-Proceed

1. : one yellow blade; one red blade; two blades, the upper red and the lower yellow; a green target; and drawf signals of one red blade, or one red over one yellow blade, or of one green target.
   

Rule 281A-Proceed Except on Diverging Route

1. : One long red blade in the clear position over one short red blade in the stop position; one red blade in the clear position over one yellow blade in the clear position over one short red blade in the stop position; one red blade in the clear position over one yellow blade in the clear position over a dark light signal; a green target over a dark light signal.
   

Rule 281B-Proceed on Diverging Route

1. : One long red blade in the stop position over one short red blade in the clear position; one red blade in the stop position over one yellow blade in the stop position over one short red blade in the clear position; one red blade in the stop position over one yellow blade in the stop position over a green light signal; red target over green light signal.
   

Rule 281C-Proceed, next signal indicates "Proceed on diverging route."

1. Yellow target over a green light signal.
   

Rule 281D-Proceed prepared to stop at next home signal

1. : one red blade in the clear position over one yellow blade in the stop position; one red blade in the clear position over one yellow blade in the stop position over one short red blade in the stop position; one red blade in the clear position over one yellow blade in the stop position over a dark light signal; a yellow target; a yellow target over a dark light signal;  a dwarf red semaphore blade in the clear position over a yellow blade in the stop position; a dwarf yellow target signal.
   

Rule 282-Proceed with caution

1. :  a single yellow blade in the stop position; a yellow target with a number plate bearing the prefix D.
   

Rule 282A-Proceed on diverging route with caution

1. : A red blade in the stop position over a yellow light signal; a red blade in the stop position over a yellow blade in the stop position over a yellow light signal; a red target over a yellow light signal.
   

Rule 290-Stop: A red blade in the stop position

1. ; a red blade in the stop position over a yellow blade in the stop position; a red blade in the stop position over a short red blade in the stop position; a red blade in the stop position over a yellow blade in the stop position over a short red blade in the stop position; a red target; a red target over a red light signal; a dwarf red blade in the stop position; a dwarf red blade in the stop position over a dwarf yellow blade in the stop position; a dwarf red target.
   

1. Now, as to definitions, the following is from the same book:  Block Signal-A fixed signal at the entrance of a block, or within a block, to govern trains entering and using that block (this seems to me to cover the question of "intermediate" signals); Interlocking Signals-the fixed signals at an interlocking; Home Signal-A fixed signal at the entrance of a route or block to govern trains entering that route or block; Approach Signal-A fixed signal used in connection with one or more home signals to govern the approach thereto (for example, see rule 281D); Distant Signal-A fixed signal in approach of a home signal to govern the  approach thereto, and for other caution purposes (for example, see rule 282); Absolute Signal-A home signal governing the movement of trains without the use of train orders and without superiority of trains; Dwarf Signal-A low fixed signal; Grade Signal-An automatic block signal designated by a disc bearing the letter "G" on the signal mast below arm or light; Light Signal-A fixed signal displaying indications by means of colored lights only.
   

2. Dennis Drury
   

3. Former SP signalman
   

References

1. Rule book images -  Semaphores
   

2. The entire 1960 Rule book is on the site at:           http://espee.railfan.net/sp_rules-regs_1960/
   

3. On the page at the link above is a search engine that you can use to find a particular rule.
   

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5. Typing in 281 will get the page that includes the color image of the  blade positions - so it should hopefully work for other rules that have images for them.
   

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7. And there it is, rule 283, on the left: two-blade semaphore, red over green.
   

8.                           http://espee.railfan.net/sp_rules-regs_1960/rules-092.html
   

9. Carsten Lundsten's well done SP signaling website http://www.lundsten.dk/us_signaling/abs_st_sp/index.html
   

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11. Mainline Modeler magazine ran a nice two-part article (complete with plans) on semaphore signals in 1980, written by Paul Lubliner. The semaphore articles are about the GRS upper quad semaphores as used on the GN and NP rather than the US&S Style B lower quad as used on the SP and UP.