If you are presented with a straight peice of mainline and nothing is ahead of your train you get a green signal.
Now place a switch with a diverging route in front of your train. Suddenly do you need a signal PRIOR to the switch? Or AFTER the switch?
The reason Im asking such a basic question is I have three simple but situations and need to learn where to place the signals and why.
What happens if the switch is part of a Passing siding that is a train length?
Where does the cross over signals go and why?
And finally but not last.
Do you have to put a signal on EVERY switch of some kind? Targets, dwarfs and highs or even bridges?
With my thinking signals go to the engineer or right side of the train and that kinds of complicate things when I think of a train going counter clockwise or “east bound” on a simple loop. I would need a signal on the opposite for the WESTBOUND every time right?
I understand one specific kind of signal. The Yard Limit Sign. Inside that yard, the road engines must keep a slow speed under control ready to stop for anything past that sign. But do THEY need to follow signals beyond such a sign like going into or out of a yard ladder?
I put up a diagram of my layout here to assist you where Im going and I placed numbers on potential situations for signals. The problem I think Im going to have is a Tower in the middle of the whole thing creating a self contained network that excludes the rest of the railroad.
Maybe also I should have put this into the layouts and layout building section, but am leaning on real life basics for signalling before I run out and buy signals.
First, most important question is, is the signal system ABS or is it CTC. Makes a HUGE difference in signal placement and indications.
If you don’t know what the difference is then you have additional research to do. Also are you wanting “prototypical signalling” or just switch position indication?
If is CTC then you want a signal with two heads to the left of sw 1 and a sw 2 there will be a signal on the main, the siding and the industry track. At the crossover there will be 4 signals (one on the main and siding to the left of the crossover and one on the main and siding to the right of the crossover) A sw 7 there will be one on the main and siding to the left of the switch and one on the main to the right of the switch (with two heads).
If its ABS-TWC/TO/DTC then there will be on to the left of sw 1 and one to the right of sw 7, maybe one to the left of sw 4 on the main.
NO other tracks require signalling.
Yard limits is a method of operation. It applies ONLY to the main track. Yard limits does not apply to the siding, it does not apply to the yard tracks. It applies ONLY to the main track. You can have ABS (or CTC) overlay yard limits (though with CTC, yard limits really don’t mean very much, it really doesn’t gain you anything).
What yard limits say is that with in yard limits trains and engines may move on the main track in either direction without flag protection clearing the times of first class trains and not protecting against other trains making all movements being able to stop within the range of vision/half the range of vision (depending on era). In ABS 2nd class and inferior trains may proceed at track speed if they have a signal better than approach. Rules will vary by railroad.
Actually thinking about it some more, I would make the crossover electric lock switches.
Then for ABS, all I would need is 4 signals. A pair of signals facing each way to the left of the point of sw 1 and a pair of signals facing each way to the right of the points of sw 7. Have yard limit signs about 5-10 cars to the left of sw 1 and the other end about 5-10 cars to the right of sw 7. Prototypically no other signals are required.
For CTC, I would use 7 signals. At sw 1 there would be a two headed signal to the left of the points (facing for trains moving left to right). The rest of the signals at sw 1 would be facing for trains moving right to left. Single headed mast signals would be on the main to the right of the clearance point between the main and the siding, and on the siding at the clearance point between the main and the industry track. On the industry track there would be a dwarf at the clearance point between the industry track and the siding. At sw 7 there would be a two headed signal to the right of the points (facing for trains moving right to left). The rest of the signals at sw 7 would be facing for trains moving left to right. Single headed mast signals would be on the main and siding to the left of the clearance point between the main and the siding, Yard limits wouldn’t be used (not needed in CTC). The only thing that would be sorta unprototypical would be the dwarf signal. A rea railroad would move sw 2 to the right enough that they needed only a signal on the siding and then wouldn’t need the dwarf.
Thank you for taking time to reply. After some thought I realized it will be easier to let the trains themselves determine the signals as a ABS system. The way I understand ABS from what I can read so far is that a train is on such a track, the circuts set a signal behind the train to red and one more block prior to that Yellow.
I think with some work today I can draw diagrams based on the information and post them later to see if I have the right idea.
In ABS the signals do not convey authority. All they do is provide information about track occupancy, switch position or broken rails. The switches are manually operated.by the train crew. The authority for a train is given by schedule, train orders, track warrants, DTC blocks, yard limits, etc. So if a train comes to a siding and has to clear for a superior scheduled train, it will do so. Even if the leaving signal is green, the train cannot depart the station because of the schedule times. Same with a meet order. If the train has an order to meet another train at a siding and the leaving switch has a clear signal, as green as green can be, the train still has to wait.
In CTC the authority to move on the main track is conveyed by the signals. The major switches (junctions, sidings, crossovers between two main tracks, switches into major yards) will be controlled by the dispatcher. And the dispatcher clears the signals/route. He doesn’t choose the exact singl, he tells the signal system to display the best signal possible and the signal system (just like ABS) figures that out). In CTC if the signal displays a proceed indication, the train can go.
I made a diagram of a train travelling Left to right on a mainline and another, same situation; entering passing siding.
Im thinking that this train already has the authority from a human to travel on this mainline. The Tower will know, ahead of time, that there is a train coming from Left to right. And that there are no trains coming from RIGHT to left at this time.
Im relying on a tower to throw the switches for this train in the diagrams I provided.
I find it easier to signal via ABS to presence of train on track. I will make presumption that there are humans authorizing orders for train to go here and do such and such at “Here”
Of the diagrams, I wrote a simple mainline diagram showing the train has nothing to do here, proceed at track speed straight through. Nothing else matters to it.
Now, if this same train is to go into a passing siding to EXPECT ANOTHER train later on, I think it would already have a meet order in hand and tower also knows this as well and has set the switches.
Another situation that is possible is that this train may be ARRIVING at the industry that is nearby and is to take the passing siding.
I deliberately left the crossovers out of this post for the time being. I fear a can of worms when the industry switcher comes out to work by running around cars during switching. Makes me think I need to put down a "LAP
If a "tower’ is throwing switches, then they aren’t “manual” or “hand throw” switches, then its either CTC or interlocking rules (which are more or less the same as CTC) and not straight ABS.
Tha absolute simplest way to do it is just put in yard limits. Put a yard limits sign (either a rectangular or oval sign that says “Yard Limits” or a yellow “V” ) 5-10 cars from the switches at 1 & 7 No signals whatsoever. No tower. The trains with in the yard limits operate at a speed prepared to stop short of any train or obstruction. They line all the switches manually.
I find it difficult to decide which way Im going to choose. ABS, Yard or CTC when thinking about the entire railroad overall. Staging is “Here” at point A connected to a town at B and this industry at C with passing siding.
I will have to do some thinking. Thank you once again for taking time to post.
I’m not sure if it’s still in print, but I’d suggest picking up a copy of Bruce Chubb’s “How to Operate Your Model Railroad” which has a good section explaining prototype signalling and simplifying it for model use.
If you are on a straight track and come to a diverging turnout, you normally would have a two-headed ‘interlocking’ signal slightly before you reached the turnout. If the top signal is green and the bottom red, you’re going straight on the mainline. If the top is red and the bottom green, you’re going on the diverging route. If both are red, the block ahead is occupied and you have to stop. It’s kinda like a traffic signal where you have a signal head for the main road, and a separate one for the left turn lane, only instead being next to each other they’re one on top of the other.
Coming from the other direction, you could have a one headed signal for each track (either green or red depending which way the switch is set) but often you would see a two headed signal with the lower head being a dummy that only showed red…so it would be green-over-red for proceed or red-over-red to stop. The problem you can get into is in railroading red sometimes is “absolute” (stop and wait until it turns yellow or green) and sometimes is “permissive” (go thru the red very slowly, slow enough you can stop if a train is stopped ahead of you). Each railroad has their own method of showing which is which…some say a red signal is permissive unless there’s an “A” on the signal meaning “absolute”, or that it’s always absolute unless there’s a “P” sign on the signal meaning it’s permissive. Two (or more) headed interlocking signals are always “absolute” so it eliminates any doubt over whether the signal is absolute or permissive. That’s why you’ll see two-headed signals used at a place where two rail lines cross at grade, even if there is no other trackage - if you go thru the red signal thinking it’s permissive, you might run into another trai
On western roads intermediate signals and signals that display a “stop and proceed” or the more modern “restricting” indication have a number plate on them. Absolute signals (those that display a stop indication) have no number plate or an “A” plate on them. In CTC pretty much any signal that governs movement over a switch will be an absolute signal.
If the siding isn’t bonded (occupancy detected or signalled) then instead of red over green for the diverging signal, the train could get a “Low” signal, red over lunar (bluish white) instead of a diverging clear (red over green).
If you go back to teh 1800’s the colors of the signals will be white-green-red instead of green-yellow-red.
If I see a Lunar (Opposite yellow) on a B&O CPL I think that train will be restricted to very slow speed and proceed into trackage that has no oversight or signalling. The Engineer will need to be ready to stop short of anything on that rail line past a restricting lunar.
I was thinking of placing a lunar dwarf on the entrance to the industry’s property off that runaround.
The thing Im beginning to understand about signals is that they may have different systems across the USA on different lines. A study of some of the rules show that in most cases the intent will be the same or very similar.
I tended to lean alot on the B&O because the colors added to the speed indicators top and bottom makes alot of sense in a way. However, the PRR’s signalling is similar but good for color blind.
When I examine some of the western roads search lights and other signals, they are even easier to see.
Here is a really dumb question in general. Suppose you come over the hill that is higher than you are and enter a tunnel?
They dont bother placing signals inside a tunnel. How are you going to know what to expect coming out of the bore? The best I can reason of is whatever is the last signal prior to the bore is what you will run.
I also learned something else tonight on reading. Cab signalling is useful because the engine somehow hears the signals in the track itself and in bad weather the engineer can maintain track speed on green high without actually placing eyeballs onto that signal yet unseen in the distance.
What rules or other considerations are provided for cab signalling post ww2?
Remember that signals tell you what is happening ahead of you, So if you have a stop signal at that signal over the hill, you passed an approach signal that told you you were going to have stop at that signal 2-3 miles before. Since that signal is at the same place its been the last 200 time you went by it you know right where its at.
The lunar signal tells you that you are leaving signaled track. So if you have a lunar leaving the siding (not runaround) then that means you have a signaled siding. That pretty much means you have a controlled siding and you are in CTC.
Cab signalling was mostly put in place where there was high speed passenger operation. If you are just running switchers out to work industries, they wouldn’t need cab signals.
Remember that every layer of control you put on is more and more restrictive on how trains operate (if you want to be prototypical). For example if you have cab signals a foreign engine can’t lead your trains (since most cab signals were incompatible).
I really shot myself in the foot that time. Forgetting the previous signal indicates what the next one will probably be.
And the cab signals not compatible with foreign roads.
So far I have four trains.
Local to work the industry and return.
commuter to the town and gone.
Local to work the town.
commuter back the other way to town and gone.
One more local to collect the output in the afternoon at the industry and gather any empties to go.
Simple enough with a few trains. Enough to keep a few people busy for a time.
At the moment, there isnt a problem working the plant job while the local pulls in and picks up the outbounds and gone. Then the commuter train goes by on the mainline while the plant switcher continues work towards the end of the day.
Another local will show up to drop off some cars for the next day and gather up the empties.
etc.
It’s not like the signal system is being overloaded with trains. It’s when maybe two trains show up near each other in the same amount of time that I get somewhat stressed because the signals in ABS will say such a track is occupied or soon to be occupied. Or in CTC I will see less oppertunity to clear the trains out of the area and on thier way.
For a little railroad layout like mine, it’s quite a workload. No complaints. Railroading is fun.
Maybe one day will go by and wife will find me hanging from the signal LED cables under the layout muttering numbers and letters to fit the things to the Se8c board. LOL.
Not that I am against signal systems, but they do add complexity, both electrically and operationally. most people don’t realize the space they take. To get the full range of signals on a 3 aspect system it would require 7 blocks each a train length long (3 on the east of the siding, the block with the siding and 3 on the west end of the siding). If you go to the higher speed, 4 aspect signals, you are now up to 8 blocks. So most model systems don’t have the full blown signalling. and many of the ones I have seen just use signals to indicate switch position (although I have operated on some large, full blown CTC layouts and it is way cool).
ABS signals aren’t used to tell a train when to clear. Train orders or track warrants do that (unless there are yard limits and the switcher is in them). As soon as the train leaves the block at the siding on either side of your station the signals will drop to red. The train might be 10 miles away, but they will drop from green to red.
In CTC the dispatcher will give the train switching track and time and the switcher can do whatever they want in those limits. When the commuters are due, the dispatcher will have the switcher clear up (and the switcher will know the commuter train’s schedule and know they have to clear up), run the commuter train and then put the switcher back out after the commuter train. I don’t know why you will have “less opportunity” in CTC, since CTC gives you/the dispatcher way more control over the train movements. BUT it
Switch indications are more important than train lenth stopping spaces between signals covering track large enough to fit entire trains. If I had to equipt my loop with a train lenth signal, it will fit in one set and there will be another block with a second set. Hardly enough signalling to do anything.
I see the passing siding on the mainline a better oppertunity to signal a small area with a reasonable amount of… what is the word… Minimum bull. I dont have miles of track to properly tumble down a train to that passing track with ABS signals and dont have a dispatcher busy enough for the widdle road that can all be seen through one glance. So… I think maybe I get away with learning a system and placing just enough signals to make it work reasonably well.
The Club railroad has a full CTC where I go occasionally and it will be something to see when you see several trains work thier way from one town to another controlled by the signals given to them. The system is not exactly working 100% but enough to assign track power on either main to a throttle.
That is another reason Im learning signals. I may want to develop that into something towards that Club road which is based on the UP and nearby roads.
Other signals that I have not gotten into yet are flares that are tossed down by engine crews after they are to stop at a point outside a yard area on a mainline. Those flares burn for a time and as far as Im concerned they are the same as stop and wait. The real question becomes, the flare is out. Now when does the choo choo get to leave? He already knows that there is a train somewhere in front.
One other thing. I think signals like to be fail safe. If something happens to the system somehow it displays the most restrictive option. If there is no power a dark signal needs to be “Stop” correct?
Well signalling can be as complicated or simple as you want. For example, as Bruce Chubb points out in the book I referenced before, yellow signals really serve little purpose in model signalling. Our models don’t have the momentum problems real trains have, so can stop quickly if they come to a red stop signal without a previous yellow signal warning the train to slow down and be prepared to stop. Just eliminating yellow makes block signalling a lot easier. Train in the block - signals are red. No train in the block - signals are green.
Flares and/or torpedos (explosives, kinda like big cherry bombs, that are attached to the track so a following train makes them go “boom” and alert the train crew that there may be a train stopped ahead) are generally temporary warnings. Let’s say a train stops because of a minor mechanical issue. A brakeman goes back from the caboose (when they had them) with a red flag, and walks back far enough that he can stop any train following his train before it would hit it, maybe a 1000-1500 ft. back.
When the minor problem is fixed, the engineer calls in the flagman by whistle signal. The flagman then would usually put down a fusee and perhaps a torpedo, and he or the conductor may put out another fusee as the train leaves. This is to let any following crews know that there is a train ahead of them that is stopped or in this case slowly getting started again. The crew of the following train would usually stop and then slowly proceed so they could stop if they catch up with
What you are talking about here are flagging signals and that is a whole nother ball of wax.
Rules for flagging vary by railroad and era, but here are the ones I am familiar with.
When the train stops or its speed falls to where the train can be overtaken (some roads have a minimum speed) the REAR crew has to provide flag protection. If the train is stopped the rear brakeman has to go back flagging distance (1-2 miles) and set two torpedoes on the rails, displays fussees if required, then comes back 1/2 the flagging disatnce to the train.and waits. If recalled the braken places more torpedoes and pops a fussee, then returns to the train.
If the train needs to be protected to the front (ex. the train is unable to clear the time of an opposing train) then the head end crew does the same thing ahead of the train.
If the train is moving but a a slow speed, the REAR end crew will drop fusees at intervals.
A train that hits torpedoes has to slow immediately to restricted speed and proceed for the flagging distance looking out for a flagman or train haed. A train moving at other than restricted speed that sees a fusee must stop and wait until the fusee burns out or if the fusee isn’t visible wait 10 minutes (the length of time a fusee burns). If the train is moving at restricted speed then the train must stop before passing the fusee and wait for it to burn out or 10 minutes.
On territory where the speed was less than 40 mph the flagging distance was typically a mile, on territory where the speed was over 40 mph the flagging distance was often 2 miles. So rather than 1000-1500 feet, the brakemen were required to go back 5000-10000 feet. considering it takes a train 4000-5000 feet to stop, if they only went back 1000 ft, that would mean the following train would be buried up about 20 or 30 cars into the rear of the stopped train before it came to a halt. “Short flagging” kinda defeats the purpose.
Ya before I put in an estimated distance I wrote something about going back far enough to stop a train given the expected speed of the following train etc. and then simplified it. Main point I was making is that the flagman didn’t stand behind the caboose with a flag, he had to go some distance back - normally trudging (according to most railroad stories) through waist deep snow or driving rain. [:)]
I suppose a lot of things would factor into it - if the railroad had block signalling, a train following the stopped train would be going at reduced speed since they would have most likely have gotten a red “permissive” signal at the last block signal. (If it wasn’t permissive, they would still be stopped at the red signal.) I suppose in a worst case scenario I train would have to stop just far enough into a block that they would clear the block immediately behind them, so the signal a train coming behind them would get would be yellow, although that would still mean the train should slow down prepared to stop at the next signal.
dehusman as usual has provided clear, accurate answers and I can’t think of anything significant to add to his responses.
One comment to your statement above – there are signals inside tunnels (and snowsheds), but just not very commonly because of clearance and maintenance. The clearance issue is usually not a show-stopper, at least on western railroads with their generally larger clearance gauges than eastern railroads, and are usually addressed by eliminating or cutting-down the target (the black metal disk behind the light). The maintenance issue is much more difficult to deal with. The primary problem with maintenance is that electrical circuits in damp, dirty places are hard to maintain, insulated joints inside tunnels are a maintenance nightmare, and trying to keep the resistor on each track circuit properly adjusted so that the circuit still detects a train, but the circuit does not also always show shunted condition, is practically a daily chore. Tunnels and snow sheds are usually short enough that signals can be placed just outside them, but not always. SP had quite a few signals inside snowsheds on Donner Pass, and UP I think still has a few of them in service.
