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Trackside signal heads and what they mean..?

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Trackside signal heads and what they mean..?
Posted by irishRR on Monday, December 31, 2018 9:27 PM

Hello. I am trying not to replicate any threads here, but I am installing trackside signals on my layout. I have some cantilever signals, some line side signals, some with single heads and some with dual heads stacked vertically. I am looking for information on what these mean. What does the top set of signals indicate vs the lower set. I understand the lights, but I guess it is the placement and positioning of these signal heads I am looking for. Anyone have some good prototype information links? I'm looking to have these signals indicate occupancy and train detection. I'm not going to wire them to indicate turnout positions. I appreciate any help. Happy new year! Cheers!

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Posted by mbinsewi on Monday, December 31, 2018 10:05 PM

You need to search and "bone up" on railroads signals.  The top light is for the section of track right after the signal, and the bottom light COULD be for the next "block", or the siding right after the signal.

There is just so much info out there.

Here's a link to prototype signals from Trains magazine.

http://trn.trains.com/railroads/abcs-of-railroading/2006/05/railroad-signals

Mike.

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Posted by 7j43k on Tuesday, January 01, 2019 12:28 AM

There is much to learn.  And it is mostly fun.  

Usually, in the west, two head signals (one above the other) are placed at the point end of a switch for a signaled siding.  The top signal is for the main line, the bottom for the siding.  They basically indicate the switch position and how to deal with it.  They will be overidden by more restrictive occupancy signaling.

Anyway, besides the one Mike mentioned, you will benefit by reading:

https://www.railroadsignals.us/basics/basics1.htm

and

https://www.railroadsignals.us

 

It takes awhile to soak it all up, though.  If you keep at it, you'll get it.

 

Ed

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Posted by wjstix on Tuesday, January 01, 2019 1:17 AM

It will help narrow it all down if you have some specific time and/or railroad in mind. Some railroads have had their own way of doing things, and signalling has changed over time as technology has advanced. The signals you might see in recent years on a railroad with Centralized Traffic Control (CTC) wouldn't necessarily mean the same thing as on a railroad in 1940 using Automatic Block Signalling (ABS).

However, generally, one-head signals are mostly used for block signals - red means the block of track ahead is occupied, yellow means the next block is clear but the one after is occupied, and green means the next two blocks are clear. Two- or three-head signals are normally some type of 'interlocking' - a place where two rail lines join into one (or vice-versa) or one railroad crosses another. 

So as Ed talked about above, say you're on a single track main that has a branchline going off of it. As you approach the turnout, you might see a two-head signal with green-over-red, meaning your train will continue on the mainline. Red-over-green means you're going onto the branchline. 

But again, it can all be different depending on the railroad and the era. 

Stix
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Posted by dehusman on Tuesday, January 01, 2019 8:20 AM

There have been several articles on signals a couple years ago in RMC.  A rule book, timetable or special instructions for you railroad will have information on what the signals mean.

I would say to read the whole signal aspect and that whole aspect means what it means.  There are certain cases when you can say that one head is the main and the other is the siding or one head is nex block and the other head is the block after that.  But there are lots of indications where that doesn't make sense.  When we taught actual train crews we told them to read the whole signal and it means what it means.

There are two general types of signalling, route and speed.  Route signalling refer to "diverging" routes (diverging approach) and state a speed and speed signaling just state a speed (approach medium).  In many cases the signals are very similar in similar situations, but that's where picking a rule book comes in handy.

Mast signals vs. cantilever signals vs. signal bridges is mostly a matter of railroad preference, available real estate and the number of tracks.

The number of heads generally refers to the number of aspects (signal color combinations) that have to be displayed.  More modern signals tend to have fewer heads than signals installed in the 1920's-1950's.

Also be willing to "compromise" on the signal arrangements.  Because model railroaders compress things and end up with a lot of funky switch arrangements, often the answer to, "how would the railroad do this?", the real answer is they wouldn't.

The twist to this is that as I type this answer, the box next to the entry box on the screen lists the users on line.  The avatar for "tstage" is right next to the box and it includes a drawing with a signal in it.  The irony is that if that was an actual signal, it would have been immediately pulled out of service for being defective.

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Posted by dehusman on Tuesday, January 01, 2019 8:47 AM

wjstix
However, generally, one-head signals are mostly used for block signals - red means the block of track ahead is occupied, yellow means the next block is clear but the one after is occupied, and green means the next two blocks are clear.

Yellow means to reduce speed and prepare to stop at the next signal.  As a train crew you can't assume the block is "occupied".  There might not be a train for 100 miles and the next signal could be red/stop.

It could be there is a train ahead.  It could be there is an opposing train.  It could be teh dispatcher hasn't lined the next signal.  It could be the dispatcher is holding your train until the yard switches up a track.  There could be a broken bond wire.  There could be a broken signal wire.  It could b a "line wrap" (a strong wind blew the line wires around where they got tangled.)   It could be a broken rail.  It could be a maintenance crew.  It could be a test.  Lots of stuff it could be, only one meaning the crew has to worry about, reduce speed to 30 and prepare to stop at the next signal.

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Posted by 7j43k on Tuesday, January 01, 2019 10:08 AM

dehusman

There are two general types of signalling, route and speed.  Route signalling refer to "diverging" routes (diverging approach) and state a speed and speed signaling just state a speed (approach medium).  In many cases the signals are very similar in similar situations, but that's where picking a rule book comes in handy.

 

 

Route signaling tends to be used by western railroads.  Speed by eastern.

Rule books can be helpful for specific railroads.  I've got a copy of "The Consolidated Code of Operating Rules".  It was used by most/many western railroads.  In it are pictures of signal aspects, and their meanings.  Most are the same, but there are also individual railroad exceptions.

I expect there might be very special and specific signal rules in an employee timetable, but nothing comes to mind.  In a 1950 SP&S employee timetable, there is nothing about signal aspects, but they do show the whistle signals to use to request routing through some interlockings.  

 

Ed

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Posted by dehusman on Tuesday, January 01, 2019 10:59 AM

7j43k
I've got a copy of "The Consolidated Code of Operating Rules". It was used by most/many western railroads.

It was used by the roads that eventually became the BN (MILW, GN, DSSA, MSTL, SOO, NP, SPS).  Another popular rule book was the Uniform Code of Operating Rules (UCOR).  Trick is there were two UCOR's, a US version and a Canadian version.  The US UCOR was used by railroads in the Southern half of the mid-west (MP, SSW, MKT, C&EI, TP, CRIP).  Many railroads used their own rule book (ATSF, SP, UP, KCS).

In many ways I prefer the '68 UCOR (US) to the '59 or '80 CCOR, the UCOR is simpler and only has one train order form, as opposed to both a form 19 and 31.

7j43k
I expect there might be very special and specific signal rules in an employee timetable, but nothing comes to mind.

The location of the signal rules varies by road and time frame.  For example, on the UP, in the 1970's the signal aspects and indications were in the rule book, in 1985 (with the GCOR implementation) they were in the timetable (special instructions), and by 2000, they were in the system special instructions booklet.

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Posted by 7j43k on Tuesday, January 01, 2019 3:01 PM

dehusman

 

 
7j43k
I've got a copy of "The Consolidated Code of Operating Rules". It was used by most/many western railroads.

 

It was used by the roads that eventually became the BN (MILW, GN, DSSA, MSTL, SOO, NP, SPS).   

And UP Or-e-gun, and some other small roads.  In 1959, anyway.

 

 

Ed

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Posted by dehusman on Wednesday, January 02, 2019 7:45 AM

7j43k
And UP Or-e-gun, and some other small roads. In 1959, anyway.

Yes, that portion of the UP used the CCOR because a large portion of the division was trackage rights over other railroads that used the CCOR, so it made sense to just use that rulebook for that division.

Similarly the MP, MKT and SSW all had a lot of trackage rights over each other, so they shared a rule book.

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Posted by jeffhergert on Wednesday, January 02, 2019 5:26 PM

I always figured that UP used the CCOR up in the Pacific Northwest was because  that set of rules were originally used on railroads that became UP subsidiaries.  Such as the Oregon-Washington Railroad and Navigation Company and the Oregon Short Line  (Both lasted on paper until the end of 1987.)  Their original foot print was where the CCOR was used at first.  Looking at various ETTs, the subdivisions governed by CCOR in the northwest diminished over time before GCOR came along.

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Posted by cv_acr on Sunday, January 06, 2019 2:19 PM

mbinsewi

You need to search and "bone up" on railroads signals.  The top light is for the section of track right after the signal, and the bottom light COULD be for the next "block", or the siding right after the signal.

That's not how any North American signal system works.

You read the entire combination of lights *as a whole* to determine its meaning, the lights on a mast don't independently indicate the status of different tracks or blocks. While indications and rule books can vary, the specific combination Red over Green usually means "Diverging Clear" or "Slow Clear" i.e. pass through switch at reduced speed and then go. Speed signalling systems also have other multiple-head signals that can be found nowhere near any switches that indicate some version of "pass NEXT signal at reduced speed".

There is a bit of variation between the signal systems and rules used by different railroads and what the specific colour combinations mean in each system, but the following concepts are more or less universally true in NA signal systems:

1 - each signal applies to one track and one track only

2 - each signal applies at the point where it is located

3 - if there are multiple heads on one vertical mast, they are read together as a combination

VERY Generally, and just in a pinch or as a rule of thumb, and with a big huge heaping of asterisks and fine print, but helps to understand the logic of signal system designs:

1 - All red means "stop" (but depending on the specific arrangement, also Stop and Proceed, and other rules exist to allow passing a Stop signal, etc...)

2 - Any combination that has at least one non-red light means "go", but may imply speed or other restrictions depending on the specific colour(s)

3 - The lower down on a multi-head signal the non-red light is, the more restrictive

4 - yellow is more restrictive than green

5 - a flashing light (in a system that uses such a thing) is less restrictive than a solid light of the same colour

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Posted by BATMAN on Sunday, January 06, 2019 2:54 PM

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1

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Posted by dehusman on Sunday, January 06, 2019 7:32 PM

Chris gave a very good synopsis.

I will say there is one caveat to the "top light belows to one track/block, middle to another and bottom to another" theory.  If someone is modeling an interlocking back in the 1800's those explanations might be true, and is probably where they started.  But once you get past about 1900, they don't apply at all.  If somebody is modeling an 1870's interlocking with semaphore signals it might be true.  Would be willing to bet that's not the situation, and would go with Chris' explanation.

As he said every signal is a "proceed" (go signal) except stop.

Every proceed signal other than clear has a reduced speed asociated with it.  

Any signal with the word "approach" in its name means that the next signal or the signal after that may be stop and the purpose is to slow the train to lower speed to be able to stop or comply with a very restrictive signal indication.

I may have said it before, but the general rule for a model railroad is if its all red - stop, if its green on top - go and anything else - slow down.

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Posted by BNSF UP and others modeler on Sunday, January 06, 2019 10:01 PM

I actually watched a few of those in that series, but I was still in the dark about signalling. There is just so many different kinds of lighting and signal configurations...

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Posted by mbinsewi on Monday, January 07, 2019 2:35 PM

cv_acr
That's not how any North American signal system works.

I know one thing Cris, you and Dave have forgotten more about the real world of railroading than I'll ever know.

Now for what I'm watching,  CN main line, part of the Waukesha, WI sub., single track main, Fond du Lac, WI to Chicago, IL., a siding in between named Midway.

There is a mast at each end with two heads each, 3 lights per head.  The top head shows red, yellow, flashing yellow, and green.  One color is on at a time, and shows the status of the main track.

The lower head, 3 lights, same as the upper, red, yellow, flashing yellow, green, with one color on at a time, shows the status of the siding.

Watching a north bound train from the south end of midway, before the train gets there, the upper head is green.  As the train goes past, it turns to red.  The siding light stays red pretty much all of the time, unless you happen to catch it just before a train enters the siding, as I believe the dispatcher at Homewood sets the siding light as needed, depending on which direction the train is moving.

Pretty straight forward, and simple.  If guess I didn't convey it that way in my reply to the OP's post.

All of the old signals from the Soo, and the WC days have been replaced, within the last couple of years with all new equipment, cabinets, and everything.  It sure looks good.

Mike.

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Posted by 7j43k on Monday, January 07, 2019 3:05 PM

mbinsewi

...single track main, Fond du Lac, WI to Chicago, IL., a siding in between named Midway.

There is a mast at each end with two heads each, 3 lights per head.  The top head shows red, yellow, flashing yellow, and green.  One color is on at a time, and shows the status of the main track.

The lower head, 3 lights, same as the upper, red, yellow, flashing yellow, green, with one color on at a time, shows the status of the siding.

Watching a north bound train from the south end of midway, before the train gets there, the upper head is green.  As the train goes past, it turns to red.  The siding light stays red pretty much all of the time, unless you happen to catch it just before a train enters the siding, as I believe the dispatcher at Homewood sets the siding light as needed, depending on which direction the train is moving.

 

 

That sounds like a classic route signal: green over red for route on main, red over yellow for route on siding:  act accordingly.

It is overlaid by ABS signaling.  Hence the change to red as the train passes the signal, and goes into another detection block.

There are likely two other signals at that location, both single head and facing the other direction.

 

Keep in mind that the least restrictive indications are shown when there's no other train anywhere near.  As other trains get involved, increasingly restrictive indictions start AUTOMATICALLY showing, because of the ABS system.

 

Ed

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Posted by mbinsewi on Monday, January 07, 2019 4:01 PM

7j43k
There are likely two other signals at that location, both single head and facing the other direction.

Yes, at the other end of the siding, as I mentioned.  And within that section/block, there are signals on the main and the siding track, facing each other, on each end.

Just measured the siding on maps, 1.70 miles long.

If I knew how to draw it in here, I would.

Just trying to explain what I said in my original post to the OP's question, as I'm not around any busy huge yards, multitrack mains, or interlockings.  Just simple signaling in the country, on a single track main.

Mike.

 

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Posted by dehusman on Monday, January 07, 2019 4:13 PM

mbinsewi
There is a mast at each end with two heads each, 3 lights per head.

Actually there should be three signals at the end of the siding, one on the single main track past the switch, one next the siding and one next to the main beween the siding switches.  That is typical of CTC.  If it was straight ABS, there would be only two signasl, both past the switch on the single main.

The top head shows red, yellow, flashing yellow, and green. One color is on at a time, and shows the status of the main track.

The signal doesn't show the "staus" of the main track, there might not be a train for a hundred miles and the signal could be red, yellow or green.  The condition of the main track will have an effect on which signal is displayed.

The lower head, 3 lights, same as the upper, red, yellow, flashing yellow, green, with one color on at a time, shows the status of the siding.

It isn't showing the status of the siding.  The condition of the siding will have an effect on which signal is displayed, the siding "status" isn't what's indicated.  If the siding is clear the signal could be either yellow or green. 

Once again.  The signal heads don't correspond to the siding or the main. The combination of colors on the head mean different things and the combination is what is important.

 

 

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Posted by mbinsewi on Monday, January 07, 2019 4:18 PM

dehusman
Actually there should be three signals at the end of the siding, one on the single main track past the switch, one next the siding and one next to the main beween the siding switches.

That's whats there, as I just tried explaing to Ed.

Mike.

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Posted by 7j43k on Monday, January 07, 2019 5:04 PM

dehusman

  

Once again.  The signal heads don't correspond to the siding or the main.* The combination of colors on the head mean different things and the combination is what is important.

 

 

 

It's my impression that they do correspond, for route signaling (speaking of two-head signals at a siding entrance, here).  The upper corresponds to the through route, the lower to the siding.  That holds not only for the routing, but the occupancy.  Here, we're talking about aspects--what color they are, and how that comes about.  As far as what to DO about it, that is a matter for the rulebook.  And those rulebooks frequently show a signal with multiple heads, and tell what action to take, based on the COMBINATION.

 

Ed

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Posted by dehusman on Monday, January 07, 2019 7:06 PM

7j43k
It's my impression that they do correspond, for route signaling (speaking of two-head signals at a siding entrance, here). The upper corresponds to the through route, the lower to the siding. That holds not only for the routing, but the occupancy.

Cool. 

You are on the BN and you see the next signal is yellow over yellow.  Are you going down the main or down the siding?   What position is the switch at the other end?  Is the main or the siding occupied?  According to your interprestation the top signal pertains to the main and the bottom signal pertains to the siding.  They are both yellow.  You can't be going down both.

You are on the UP and you see the next signal is yellow over green.  Are you going down the main or down the siding?   What position is the switch at the other end?  Is the main or the siding occupied?  According to your interprestation the top signal pertains to the main and the bottom signal pertains to the siding.  

You come up to a signal that is red over yellow over red and at another location you come up to a signal that is red over red over yellow.  What's the difference in meaning between the two signals?  If the different heads pertain to different tracks, then there should be a difference.

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Posted by 7j43k on Monday, January 07, 2019 7:31 PM

dehusman

 

You are on the BN and you see the next signal is yellow over yellow.  Are you going down the main or down the siding?   What position is the switch at the other end?  Is the main or the siding occupied?  According to your interprestation the top signal pertains to the main and the bottom signal pertains to the siding.  They are both yellow.  You can't be going down both.

 

Looks to me like a not-permitted indication.  As in:  can't happen.

If it did happen, how?

 

 

 

Ed

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Posted by cv_acr on Monday, January 07, 2019 8:10 PM

7j43k

 

 
dehusman

 

You are on the BN and you see the next signal is yellow over yellow.  Are you going down the main or down the siding?   What position is the switch at the other end?  Is the main or the siding occupied?  According to your interprestation the top signal pertains to the main and the bottom signal pertains to the siding.  They are both yellow.  You can't be going down both.

 

 

 

Looks to me like a not-permitted indication.  As in:  can't happen.

If it did happen, how?

 

 

 

Ed

 

Wrong. It's absolutely permitted and if you look up a BN/BNSF signal chart (google "BNSF signal rules" and it's the first result) you'll see its called "Approach Medium".

In Canadian rulebooks it would be "Approach Slow". Yellow over green would be "Approach Medium". But the route signaling rules used by BNSF don't distinguish between different speeds. Canadian speed signals distinguish between Slow (15 mph), Medium (30 mph) and Limited (45 mph) speeds for different switches.

With feeling again - the signal heads do **NOT** independently indicate the status of different tracks. They light up in a particular combination to give the required indication.

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Posted by 7j43k on Monday, January 07, 2019 8:27 PM

I still look forward to hearing about how the yellow over yellow indication comes about.

 

Ed

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Posted by dehusman on Monday, January 07, 2019 8:33 PM

7j43k
Looks to me like a not-permitted indication. As in: can't happen. If it did happen, how?

It does happen.  Since the signal heads DO NOT correspond to particular tracks its very easy.

What Chris said.

Each signal indication means what it means.

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Posted by dehusman on Monday, January 07, 2019 8:45 PM

In the 1968 Uniform Code of Operating rules, the yellow over yellow is rule 282,  advance approach, proceed reducing to 50 mph before reaching the next signal.

In the 1980 Consolidated Code of Rules, BN signal rules, the yellow over yellow is rule 501A, advance approach, proceed prepared to stop at the second signal.  

In the 2003 UP General Code of Operating Rules, the yellow over yellow is a version of rule 9.2.5, Approach diverging, proceed prepared to advance on diverging route at next signal at prescribed speed through the turnout.  Not to be confused with Diverging Approach, red over yellow which is proceed on diverging route at prescribed speed through the turnout, immediately reducing speed to 30 mph (passenger trains 45 mph).

In all of these cases the signal means begin to slow down and be prepared to do something at the next signal.  Its a signal used to give additional stopping/slowing distance.

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Posted by 7j43k on Monday, January 07, 2019 8:58 PM

7j43k

I still look forward to hearing about how the yellow over yellow indication comes about.

 

Ed

 

 

And then there's this:

 

For a route-signaled two-headed signal at the entrance to a siding, how likely will the switch be set for the main if the signal is green over red?  And how likely will it be set for diverging if the signal is red over yellow?

 

I am well aware that an engineer is supposed to do what the signals tell him to do, according to the rules of the railroad.

I am talking about how those indications arise.

 

Ed

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Posted by cv_acr on Monday, January 07, 2019 9:04 PM

7j43k

I still look forward to hearing about how the yellow over yellow indication comes about.

 

Ed

 

 

Try this on for size:

(Only eastbound signals are shown for clarity)

Copy and past link if image doesn't work: http://vanderheide.ca/files/route_signals.png

A train is travelling west to east on double track track, and is lined up by the dispatcher to be routed through crossovers around a stopped train, or MOW work block, or just because...

A block away from the crossover, which is already lined and cleared by the CTC dispatcher, the train sees an "Approach Diverging/Approach Medium" signal showing it it needs to slow to take the diverging route at the next signal.

(Bonus signal, just for fun) At the crossovers, the signal "Diverging Approach Diverging" because the train will be again taking a diverging route at the next set of crossovers which are at the next set of signals down, no intermediates between here. (All other conflicting routes not lined into the interlocking show "Stop").

At the final set of crossovers the signals show "Diverging Clear" as it will be straight sailing from here on at least for the next block or so.

If the train were to simply go straight at the last set of crossovers, the overall signal progression would be "Approach Diverging" (Yellow/Yellow), "Diverging Clear" (Red/Green/Red or Red/Red/Green on this signal), "Clear" (Green/Red) instead of "Approach Diverging", "Diverging Approach Diverging", "Diverging Clear"...

If the signals at the last set of crossovers aren't cleared by the dispatcher yet, they'd be at stop, so the signal progression would be "Approach Diverging" (Yellow/Yellow), "Diverging Aproach" (Red/Yellow/Red or Red/Red/Yellow), "Stop" (Red/Red). The last signal would remain at stop until the dispatcher clears it, giving either "Clear" (Green/Red) or "Diverging Clear" (Red/Green) depending on whether the route is lined through the crossover or not.

 

Indications based on this chart of BNSF signals: http://utu199.progressthroughunity.org/documents/Signals

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Posted by cv_acr on Monday, January 07, 2019 9:15 PM

7j43k

For a route-signaled two-headed signal at the entrance to a siding, how likely will the switch be set for the main if the signal is green over red?  And how likely will it be set for diverging if the signal is red over yellow?

100% likely in both cases because Green over Red is the indication for "Clear" and Red over Yellow is the indication for "Diverging Approach".

It is 100% unlikely that a Green over Red signal will be displayed if the switch is routed into the siding because that *must* display an indication with "Diverging" in the name. Likewise, the straight route will not display a "Diverging" indication because it's not diverging...

None of this is because "one light is for the siding and one is for the main".

In either case the signal could simply be "Stop" if this is CTC track and the dispatcher has not set the signals to allow a movement through (or if the movement has been cleared in the opposite direction, even if that movement is still miles away and the blocks are clear...)

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