Accurate 50's era ATSF and SP signals?

[C855B]

If you're saying (and can confirm) that the bottom head is an SA then all the single-color discussion is moot. It's really hard to tell from the photo alone. I originally suggested that it was atypical to have a Type D in one position and an SA in the other. In thinking about it, however... it is perfectly logical that this was originally a single-head three-color on a short mast, and there was a later change where a lower head was needed but there was not enough room for a three-color head. So to save the cost of installing a new mast or changing out a perfectly good top head, a searchlight was used in the lower position, to heck with the difference.

Also, bear in mind that the photo above which started this discussion is from 60 years ago. I don't have a 1950's rulebook in front of me, but practice then and what you're familiar with now are very likely apples and oranges... things such as color-over-dark aspects, for instance.

[arbomambo]

For sure, this arrangement is/was 'atypical' ; going through lots of vintage pics...I don't see any other instances with this set-up...what's also strange is that this signal doesn't seem to protect a switch...these were double track mains with a substantial seperation with right-hand running (the train is heading west towards Topock; you can see the eastboung track behind it on a higher level)...I don't know of any switches off this trackage, then or now, within the next 5 or 6 miles, but I could be mistaken.
Respectfully,
Bruce

[jagged ben]

A two headed approach signal can be a whole block before the signal that's right in front of the switch.  It's doubtful that the block would be 5 or 6 miles, but it might have been.  It also doesn't seem totally implausible that there might have been a siding (or even a spur) in this area in the 1950's that is now long gone.

FWIW, here's some approach signals on a totally different railroad...
http://www.carrtracks.com/cateh349sp9335.htm

These are not directly in front of a switch, they are both one block ahead of the signal that's in front of the switch.  Note that the lower heads do not appear to have the same SA housing as the upper ones, and that the lower head appears to be dark.  The lower heads were upgraded to the same full searchlight style as the upper ones sometime in the 80's.  Granted, it's a different railroad, but these signals are part of the reason I don't think it's impossible that the bottom light was a single color only.  In any case, there's probably no way to deduce it for sure lacking specific knowledge from an old ATSF hand.

[C855B]

Heh. I remember those signals (I lived in the area then). Lower head was a fixed green - not an SA, in other words - so if you were lined into Walong (or Woodford), it would be a yellow-over-green. Otherwise, it would be dark. This oddity was needed to avoid the need for abrupt changes in throttle/DB settings in difficult terrain, because normally this intermediate signal would show yellow if the siding signal was red-over-whatever, the yellow (alone) signifying preparation for a probable full stop at the "A" signal controlling the siding entrance.

Which brings a point I thought about this morning. Practice which allows a lower head to be dark, such as that SP example, usually has a small target or no target.

[cv_acr]

I tend to think that the bottom signal in that picture might not be an SA, but a fixed aspect.

I would tend to think that as well. Mixing different types of signals on one pole would certainly be a first. But for three-light signals if a particular head will never display certain colours there's no reason to include those lamps on the signal. For example, where I usually do my railfanning is at the end of a double track segment on CN, and the signals are the newer three-light style. The route through the switch can only be taken at medium speed, so the top and bottom heads of the signal only have a single red light, and the middle head has all three red/yellow/green lamps. The top and bottom heads are never anything but red, so there's no reason to have additional lamps.

You need an ATSF rulebook from the appropriate time period or someone more familiar with ATSF practices to figure out the possible indications and the reason for the lower lamp that can only display one colour on the signal shown.

The SP searchlights shown above look like a pretty similar idea, but again you really need to check ATSF sources as the rulebook may not be the same.

[cv_acr]

I don't have a 1950's rulebook in front of me, but practice then and what you're familiar with now are very likely apples and oranges... things such as color-over-dark aspects, for instance.

Exactly. For example the Canadian rules I'm very familiar with do not have a single rule that includes an unlit signal head in any aspects. But I've definitely seen other examples given on websites showing signal rules from various US railroads where dark/unlit heads are a legitimate possibility.

There's a lot of variation here between railroads, and over time.

Another thing that doesn't exist anywhere in Canadian rules? That whole thing about a number plate or lack thereof being the distinguishing feature between signal displaying a "Stop" and "Stop and Proceed" indication. Very important to know what rules you're looking at.

[cv_acr]

Santa Fe was the only big western road to use flashing green frequently, but it was and still is much more common on the east coast.

Generally the flashing green is only seen on "speed signal" systems where the high, middle and lower signal heads represent the "fast", "medium" or "slow" speed of the routes.  A normal green on a "medium" signal head must be taken at at medium speed, but a flashing green represents that this route can be taken at the "fast" speed.

Or to be a bit more specific and use the official correct speed terms:
LIMITED (45 mph)
MEDIUM (30 mph)
SLOW (15 mph)

[Dupesy]

You'll never see flashing green in the top position on any US railroad.  It will always be below another signal head.

Actually, this signal is used in Cab Signal territory.  NORAC rule 281A, Cab Speed.  "Proceed in accordance with cab signal indication.  Reduce speed to not exceeding 60 MPH if Cab Speed cab signal is displayed without a signal speed, or if cab signals are not operative."

[jagged ben]

Heh. I remember those signals (I lived in the area then). Lower head was a fixed green - not an SA, in other words - so if you were lined into Walong (or Woodford), it would be a yellow-over-green. Otherwise, it would be dark.

Huh!   Interesting.  I assumed that the indication would be yellow over yellow not yellow over green (although both appear in the SP 1996 timetable as "approach diverging").   We've been modeling them on our club layout as yellow over yellow.  You telling me we should change it to yellow over green?    Nice to have someone confirm who actually saw them and remembers back then.

Did it only show the green if the next signal was red-over-green?  Or did it also show green it if the next signal was red-over-yellow?

[C855B]

Yellow-over-green was proper in either case, as it was a "distant" aspect corresponding to the indication on the next lower head. So the only instance where a lower head in this situation would need to be yellow would be if the next signal was red-over-red, and in this case that was covered by yellow-over-dark.

This was actually a smart bit of signaling. The RR between the east end of Woodford and west end of Walong was/is a grueling bit of track. Eastbounds would labor uphill in run 8 around some pretty tight curves, and you did NOT want to throttle back if you didn't have to. This was a knuckle-busting, drawbar-yanking slog. So by communicating that you were lined into the siding at Walong and did not have to stop until the east siding switch, it was possible to keep things moving and get your train in the clear. If it was a simple yellow on the intermediate and you throttled back in anticipation of a red-over-... well, something at the west switch, there was a good chance you might not get your train moving again, or break something when you throttled back up to get into the siding. Nothing like pulling a drawbar on the wrong end of a car... saw it happen a couple of times there. That's why there were setout tracks at both Walong and Woodford.

[draskouasshat]

You need an ATSF rulebook from the appropriate time period or someone more familiar with ATSF practices to figure out the possible indications and the reason for the lower lamp that can only display one colour on the signal shown.

I guess noone noticed my signature about who i work for and in what department. Granted i dont know EVERYTHING, i do know quite a bit about what i have worked on. As far as i know, speed signals werent commonly used on the transcon as others have thought this example was. Like C855B said, its most likely a searchlight that was added later to make this an approach or holding signal due to grades for braking distance or uphill runs. Another example like on cajon was the lower head basically displaying a yellow at all times. Signals on the uphill climbs were mostly dual heads and the top head displayed the immediate blocks occupancy and the lower displaying a yellow at all times. Hell, this could be a lunar on the bottom head. Until you know the track setup and a background of how the santa fe signal system works, speculation is all you have.

[C855B]

>I guess noone noticed my signature about who i work for and in what department.

Yes, we did. How many years you got?

[jagged ben]

draskouasshat,

I noticed your sig, too, but then I also am aware of some ATSF rulebooks from a few years ago...
http://www.railroadsignals.us/rulebooks/atsf89/index.htm

I never said in this thread that ATSF used a speed signaling system, but the "Approach Limited" and "Advance Approach" aspects make the Santa Fe system a bit of a hybrid I would say.

I agree with you that it's hard to say anything for sure about the photo without knowing the track arrangement. 

[jagged ben]

One more contribution to this thread:  an ATSF signal aspect table from 1959 that I just found.  Probably more relevant to the original question than a lot of what else we've discussed.

http://www.flickr.com/photos/mark_vogel/7522284256/

Some radical differences from what we know today.  It would also seem to suggest that back during that period the lower light would more likely have been yellow than anything else.


Oh, and to C855B:  thanks for the additional comments.  I'll work on getting our club's approach signals changed.   

[draskouasshat]

8 years but im lucky enough to work on both the transcon and topeka sub so i see the oldest signal system and the latest and greatest. Im now a signal foreman and on the road working in tulsa now on the avard sub putting PTC into service.