Prototypical railway signals?

[wjstix]

I guess a key point is that there are basically two types of RR signals - block signals and interlocking signals.

Block signals are like stop and go signs on a street, when a train enters a block those signals change to red to warn other trains that the block is occupied. They are usually just one headed with three lights (green, yellow, red).

Interlocking signals are used to indicate where the train is going - on the mainline or diverging - or to warn of another trainline crossing your line at grade. These signals are almost always two headed, although in many cases one head would be a dummy (like one head only showing red, while the other can be red or green). Two heads are often used just to clarify that these are not block signals, as different operating rules apply depending on whether it's a block signal or an interlocking signal. (For example as I mentioned earlier, most block signals are/were "permissive" allowing a train to run the red light at slow speed prepared to stop if necessary. That wouldn't work if you were coming from a branch line onto the mainline, if you see a red signal at the jct. it means the points are set for the mainline - if you proceed, you'll derail !!)

Now yes you could build a model rail signal system using single heads for both - but it wouldn't be that much more expensive or time consuming to 'do it right' and use two headed signals for your interlockings. No more difficult than doing intricate brake rigging for freight cars that don't have working brakes, or putting power lines up between power poles that will never carry power. It just looks better !! [:)]

[dehusman]

Part of the problem is that ABS in Australia is completely different than ABS in the US. Same acronym, very different systems.

A key element is whether the signal system conveys authority or just occupancy information. In N America an ABS system on single track conveys occupancy information. Authority is conveyed by other means. It is entirely possible in N America for a train to have a proceed (green) signal ahead of it and NOT have authority to pass it or have a stop (red) signal in front of it and HAVE authority to pass it.

Dave H.

[Anonymous]

In response to the talk comparing US and Australian practice, Victorian Railways at least use two main signalling systems.

The first system is the Absolute Block System (ABS) and can be divided into sub-types such as Double Line Block. Basically this system works as previously stated in an above post where the concept is that the line is broken up into blocks where only one train may occupy a block at a given time. The signals used under the this system mostly only display red or green indicating that a train may either enter the block or it may not. That is the basic concept and there are other signals that apply in this system such as distant signals, which are similar to permissive in that their stop position isnt actually stop but means that the NEXT signal (or one of) is at stop. It is a bit more complicated but that is the basics. Turnout positions consist of two standard signals on a single bracket positioned to the left and right of each other. At no time will both signals display green (interlocked) and it works on the basis of left signal = green, train will take the left route. Right signal = green, train will take the right route. Even tho the two signal heads are next to each other on a horzontal plane, often you will find one positioned higher than the other indicating the 'main' or non-diverging route. This ABS system was (and is) used extensively on rural lines where traffic is of a medium density and blocks generally extend the entire length between towns or junctions. This system (at least the victorian version) required a lot of man power but was without a doubt the safest form of track protection for reasons i wont go into right now.

The other primary system in Victoria is one i think you will find is similar to the US systems as i think that is what it was based on. This system is the Three Position System and the resounding difference between this and ABS (Victorian style) is that Three Position introduced the use of three signalling indications (red, amber or yellow, and green) as opposed to just red and green. This system was introduced i think about 1915 to better handle the congestion on the Melbourne Suburban system. It allowed trains to operate closer together because the signal system worked on speed indications and gave the drivers advance notice of what the next signal was indicating. IT consists mostly of a pair of signal heads mounted vertically on the same post. All targets are illuminated at the same time and thus indicate speed. The higher light indicates high (or 'normal') speed and the lower light medium or low speed. In some cases there many even be a third light for very low speed.

I.E. RED over RED = STOP.
RED over GREEN = medium speed CLEAR
GREEN over RED = normal speed CLEAR
YELLOW over RED = normal speed WARNING -> indicates that the driver should be prepared to stop.

There are at least seven possible indications on the victorian system i believe. One interesting note that i believe is different to the US is that the arrangements of lights indicate whether the signal is an automatic type or manually controlled. If the lights are perfectly vertical over each other then the signal is manual and doesnt not show a permissive stop. When a train comes across a manually controlled signal that shows stop is must STOP and not move past the signal. A signal where the targets are offfset or 'staggered' above each other is defined as an automatic type that is not controlled by anyone except a track circuit (and other things like level crossings). An automatic signal displaying stop -> the train must come to a complete stop but may then proceed at a speed whereby the train may be able to pull up short of ANY obstruction. Similar to US practice.

Although not strictly an indication of route it could be used as such by the drivers. For example a signal leading to a turnout. Providing the line was clear to begin with -> a RED over GREEN aspect would indicate MEDIUM SPEED therefore suggesting the turnout was lined for the diverging route. Or GREEN over RED would be a NORMAL SPEED aspect advising the driver the the turnout is aligned for the straight route. All in all i guess to the driver it doesnt matter where he is going as long as he knows what speed to go. One point is that ABS shows no speed indication. The system assumes that the drivers know the routes and the various speeds are posted on signs.

In Melbourne on some signals (3 position system) there are true turn out indicators. These are either white illuminated arrows or feather systems. These can be seen at North Melbourne station at the entrance to the underground. The reason there are here (and in other places) is that the speed is the same no matter which route the train takes and at this particular station there are large numbers of trains that go either way so the turnouts are changing position every minute or two.

One final note is that one some convential three position signals (particularly at Nth Melb) there signal has a display with a letter. This letter is a shorthand indication to the driver which way the route is lines up for a junction some kilometres down the track. "E" means he will be going to Essendon while "F" means he is going to Footscray. As far as i am aware this little feature is not an 'official' indication in that it should in no way affect the trains speed etc but is purely (i think) just to inform the driver the way route is lined up further along where he cant see yet. This is epecially true because departing north melbourne you have a choice of about four different routes all diverging within a couple of kilometres.


Thats enought rambling for me now!! In my opinion the ABS system is simple to use and easy to install. Especially for many of us who arent signalling or electronics experts.

[Anonymous]

At the Flagstaff (AZ) Model Railroad club we use Switchmaster turnout motors powered by relays. When the track diagram mounted toggle is "Off" the route aligns to normal. We use either three color LEDs or pairs of red/green LEDs wired to the power to the motor to indicate the position. We have found these to be 90% reliable, only when the motor breaks do we have problems.

[Jacktal]

First,I wi***o thank all you gentlemen for your most kind answers.Although there seems to be no definite signalling system,neither international or even on national basis,I'm most happy with what I learned with your inputs,thanks again.

From what I read,it seems that each railroad has its own rulebook pertinent to train circulation and do likewise with their signalling,meaning that for layout purposes,any signal system that would have a logic behind it could be called somewhat prototypical.

At a local electronics store,I believe I saw DEL's that glow either red or green depending on how the polarity is fed to them.I could use snap relays to do so,or have someone design a small electronic circuit for me maybe,but these LED's would certainly make neat red over green/green over red signals that would look quite prototypical,at least close enough for me.

Since don't plan on multitudes of turnouts on my layout,costs won't be much.On the other hand it would improve operations greatly by reducing the "unauthorized" entries to wrongly thrown turnouts.Thanks guys.

[markpierce]

When I did a search on "southern pacific railroad signals" I got a number of good hits, particularly one on www.deu.edu/(wiggly line)etuttle/rail/to" and "www.trains.com/content/dynamic/articles/000/003/035sexb.asp?" that applied to various railroad's practices, particulary on train order signals, interlocking signals, etc. You're unlikely to find the sites directly by typing in the www addresses, just do a google search on the topic and the two sites I found most productive should come up.

[John Busby]

Hi Mark
We have not had train orders that long and then only on lightly trafficed branch lines.
just changing the subject a little.
Was looking in the book Safe Signals
A history of the NSWGR signaling system
In the early days they had a twin arm signal that aparently did both main lines
the book is not that clear on it
Do you know anything about it like how it worked the roding arangement is not clear and it apears to be a sloted post signal with a common lamp
and weird spectical arangement.
Its a very early one a bit before our time
regards John

[marknewton]

QUOTE: Originally posted by John Busby

All railways in the EX colonies and protectorates of the United kingdom and a fair few of the European railways use absolute block. NSW acording to the S&C practices and princaples book I got from the S&C NSW office states absolute block working is what is used but that may have changed.

It has. Absolute block is now only used in limited circumstances in NSW, having been superseded by US-style systems such as Train Order working, or by modifications to existing systems such as Rail Vehicle Detection.

[John Busby]

QUOTE: Originally posted by dehusman

The absolute block system or staff system is very rare in the US since the early 1900's. Our signal systems are very much different. The only time anything close to an absolute block system is used is in non-signaled territory when cabooses are not being used or when a cab signal system on an engine fails.

If you are modeling the US, then signal systems outside the US won't be very close at all to US systems.

Dave H.

I dont concider that a problem[:D] I would adapt the indications to red is stop and wire it so you havn't got a choice.
Since I have not yet come across a model railroad that is large enough to acurately model a full signaling system.
So a couple of arrival and departure signals and any directing signals at a junction is about the maximum most layouts end up with
many don't even have that just a few thrown in for effect.
If I was modeling US railways since your system seems to go against every thing I have been taught about signal systems and what is right. .

I would use train orders then I could model those weird and visualy interesting two arm signals you use for those.
Any body got a decent drawing of one of those I might make one just for the hell of it

The signal system that pays for the model trains is fine by me.
the way our CTC and Automatic signaling works it keeps the trains at all times two signals appart so you end up with a maximum of one and a half trains in a block
as one is leaving the block another is allowed in
regards John

[wjstix]

[

[dehusman]

The absolute block system or staff system is very rare in the US since the early 1900's. Our signal systems are very much different. The only time anything close to an absolute block system is used is in non-signaled territory when cabooses are not being used or when a cab signal system on an engine fails.

If you are modeling the US, then signal systems outside the US won't be very close at all to US systems.

Dave H.

[nbrodar]

John,

Under CTC and Automatic Block Signals, you can stack as many trains in a block that will fit. Red signals, other then those designated as Absolute, may be passed at restricted speed. In a nutshell restricted speed, means traveling at a speed that will allow you to stop within one half the range of vision, short of any obstruction on the track.

Interlocking Signals have a whole other set of rules, which might be what you're thinking of. Interlocking Signals are absolute, and unless there are two or more non-conflicting routes through the it, only one train may occupy the interlocking at a time.

Nick

[John Busby]

Hi all
All railways in the EX colonies and protectorates of the United kingdom and a fair few of the European railways use absolute block
exept South Australia.
NSW acording to the S&C practices and princaples book I got from the S&C NSW office states absolute block working is what is used but that may have changed.
Absolute block block system at its most basic
States That only one train at any time may occupy a section of line
in that system a signal at red means stop the line a head is blocked
a yellow means bring your train under control too stop at the next signal it is red.
Green proceed at track speed.
We have automatic signals as well but they operate to absolute block principals as does our centralized traffic control system
a SPAD Signal passed at danger is not desirable and the train driver gets the choice of being hanged or cruccified being let off is not an option.
When an absolute block system fails the signals return to red for stop and
The paper work to pass the signal is very specific in its instructions and must be completed before the driver can pass.
If at a station then its pilot key working, which basicaly is a return to train staff
working and only the train with the pilot key can be in the section as once removed the departures at both end of the section go red and cannot be cleared.
That should make things a little more clearer my information is that the system is also used in the US as well.
regards John

[marknewton]

QUOTE: Originally posted by nbrodar

John,

What is Absolute Block System? I'm a professional railroader and have never operated under anything by that name.

It is a safeworking system - or rules - that originated in the UK, and is commonly used there and in countries where the railways developed under British influence. John is perhaps unaware of US rules, and how much they differ from those in Australia.

QUOTE: Also, US signals display speed information, rather then route information. Although, you can normally tell the how route is lined from the speed indication.

Most UK and UK-style signalling displays route information, which may be another source of confusion to non-US posters.

All the best,

Mark.

Nick

[marknewton]

QUOTE: Originally posted by John Busby

Hi all
Beware of sweeping statements like most red signals are permisive they most certanly are not.
it all depends on which system is being used there are two systems
permisive block and Absaloute block

John, the original statement is valid for most US railroads. Their safeworking systems and rules are in many ways quite different to those you would be familiar with in WA. Even in NSW we are now referring to automatic signals as permissive, since they may be passed at stop without a proceed authority from the signaller.

All the best,

Mark.

[marknewton]

QUOTE: Originally posted by John Busby

Hi mark We are talking specificaly about a point indicator. it has two triangle shaped heads one facing each direction.
They have a triangle pattern of three lunar white lights.
The indications given are
two lights one above the other points are normal
two lights at an angle aprox 45 degrees points reverse
Lights out STOP!!! the points are not right
It should be noted a point indicator is not a signal.
regards John

Must be a Sandgroper thing, John. [:)]

Point indicators in the eastern states - NSW at any rate - are quite different. I'd love to see a photo of a WA-style indicator.

All the best,

Mark.

[wjstix]

Well one of the interesting (annoying?) things about signals is that there are some general guidelines that all roads share, but railroads do different things based on their unique situation. I suspect some roads (at least in the past) have put in their rulebook that "all stop indications are permissive unless marked with an "A" for "absolute" and others have "all stop indications are absolute unless marked with a "P" for "permissive" !! Plus like I said in the last example I gave, you probably could do a simpler signalling system for a model RR than what the prototype has to do, like using a one head signal when coming from a diverging route etc.

[nbrodar]

John,

What is Absolute Block System? I'm a professional railroader and have never operated under anything by that name.

I've run under CTC and Automatic Block rules, under which most red signal (always marked with a number or P plate) are permissive, and only interlocking signals (without a number or P plate) are absolute.

Also, US signals display speed information, rather then route information. Although, you can normally tell the how route is lined from the speed indication.

Nick

[John Busby]

Hi all
Beware of sweeping statements like most red signals are permisive they most certanly are not.
it all depends on which system is being used there are two systems
permisive block and Absaloute block
and pretty much in both systems it is red stop the line ahead is occupied
I have often seen red point indicators but dont like them because it is red go
rather than the normal red stop.
In signal territory a diverging route generaly means two signal heads or arms
one higher than the other they are read top to bottom left to right
the top one allways being the main line the lower one always the diverging route.
regards John

[dehusman]

Actually coming south you ould have one head on the main and one head on the "diverging" track" There would be no need for a 2 headed signal since you can't "diverge".

Dave H.

[nbrodar]

Dave H. makes a good point with putting an bi-polar LED inplace of a switch stand. It's simple although not very prototypical, for a modern layout, now that lighted switchstands are a thing of the past.

Simple single head signals would give a more prototypical look. Few model railroads have signals at all, so the absence of a second head and other block signals will probably go unnoticed.

Also, while it is true most red signals are permissive signals they always marked as such. No number plate, P plate or other marking and it's stop and stay, even if there is only one head.

Nick

[wjstix]

Let's say you're on a single track mainline going north and there's a turnout ahead where the mainline goes straight thru, and a diverging line goes off towards the right (east). As you approach the turnout going north you'd see green over red if you're going straight, red over green if you're taking the diverging route east.

If you were on the same mainline only heading south, you would probably see a two-headed signal, but it would have one of the two a 'dummy' head that could show only red, probably the lower one in this case. So...you could see green over red (meaning you're clear on the mainline) or red over red (stop - the tracks set the other way).

If you were coming from the diverging line to the main, you would probably see a signal with the top light being a dummy red light, so you could see red over green (OK to go onto the mainline) or red over red (stop).

For modelling, you could replace the last two with a signal that just shows either red or green. On the prototype, most red block signals are "permissive" meaning you can go thru them slowly - kind of like a rolling stop at a stop sign in your car. This wouldn't work here so the two lights tells the engineer this is an interlocking signal, not a block signal.

BTW the lights would normally be very close to switch, almost right on top of it.

[dehusman]

If you put an LED AT each switch and wire it to be green when normal and red when reverse, it will substitute for a switchstand and can be seen in either direction.

What I do is use pushrods to control my switches. In is always normal, out is always reverse. You just look down the fascia. If a handle is out, its lined reverse.
Then I paint the pushrods (1/4" dowells) right behind the knob red for main track switches and yellow for other than main track switches. If the knob is out and the rod is red then a main track switch is lined against you.

Zero electronics. Just paint.

Dave H.

[John Busby]

QUOTE: Originally posted by marknewton

QUOTE: Originally posted by dehusman

Just remember the "3 light" arrangement is Australian. If you are modeling N America, that system isn't used.

Are you referring to three-aspect signal heads, or "rabbits-ears" route indicators?

All the best,

Mark.

Hi mark
None Of the above[:D]
We are talking specificaly about a point indicator. it has two triangle shaped heads one facing each direction.
They have a triangle pattern of three lunar white lights.
The indications given are
two lights one above the other points are normal
two lights at an angle aprox 45 degrees points reverse
Lights out STOP!!! the points are not right
It should be noted a point indicator is not a signal.
regards John

[Jacktal]

You're right Dave,I got somewhat carried away indeed.Block detection may eventually be part of my layout,but not for the moment.I'm just trying to be able to tell which way a TO is thrown,and doing this,I thought I might as well try to duplicate how the railways do it,in both directions.

A pair of DEL's that can be seen from both directions would do great,as layout TO's can also be approched from opposite directions too.I was overdoing it as I often do,but that's me......

[dehusman]

You are mixing apples and oranges here. Your question was about having signals that indicate turnout position.

If you want to add know when trains are approaching, then you need a full fledged signal system with block occupancy detection.

Its the difference wiring a light switch and wiring a house.

Dave H.

[Jacktal]

You know what?...You guys have me absolutely thrilled...and challenged.I love the G/R and R/G idea for discerning which way a TO is thrown when you are coming to it facing the option of going either way.So far so good...and great.But what about when you're coming to the TO the other way?Are there separate panels for each diverging route saying let's say G/R for the main and R/R for the diverging route when the TO is set for the main?And the opposite would say R/G for the diverging route and R/R for the main when there's an in coming train from the diverging track?

In my mind,such warning panels would have to be set at a fair distance from the TO for the train having sufficient stopping distance in case of emergency.So a single panel would be OK for the single end of the TO but what about the converging tracks?I don't think a common panel would suit in every case,would it?What I mean is what happens when a train comes out of a curve onto a straight main track and can't see the TO from a safe distance?

I believe I saw LED's that alternately glow red or green depending on the polarity of the current,which would call for more complex wiring,but I'm up to the challenge.And challenged I am,believe me.Thanks.

[jimrice4449]

The only place I've seen signals that indicate switch position only (as opposed to speed indications) on the 3 RRs I've worked for is in a yard w/ power switches. If you're going to use the Atlas relays, why not just install LEDs protruding from the fascia (so they'll be visible from a distance) at the location of each switch wire so that a red LED is illuminated when the switch is set for a diverging route and a green when it's set for normal?

[wjstix]

p.s. Bruce Chubb's book "Operating Your Model Railroad" from Kalmbach has a good chapter on prototype signals and adapting them to the model RR. Not sure if that's still in print but I'm sure you could find it at a flea market or on ebay.