not sure about terminology
my basic understanding of signaling is to position signals at either end of a siding used to allow trains to pass one another on a single track mainline.
my small pt-to-pt layout has two station sidings. Each siding is intended to allow the engine to change positions so the train can reverse direction as well as switch cars on team track and nearby spurs. But if there is a signal at each end of the siding, this doesn't seem allowed if the blocks at either end of the siding are occupied (not clear).
it seems that there are sidings intended to allow trains to pass one another and there are sidings or run-arounds intended to support switching operations.
i hope someone understands my questions and can help clarify my understanding
greg - Philadelphia & Reading / Reading
gregcmy basic understanding of signaling is to position signals at either end of a siding used to allow trains to pass one another on a single track mainline.
Not necessarily.
Nothing requires signals at a siding or, especially, a runaround. The arrangement of signals depends on the signal system being used. In a TT&TO/ABS, TWC/ABS, DTC/ABS ssytem there will not be signals at the switch, there will be signals in both directions beyond the switches on either end. In CTC there will be three masts or heads at each controlled switch.
MR doesn't host photos and I haven't found a hosting service since Photobucket started charging, so I can't post a diagram.
The key thing is what signal system do you have? ABS or CTC? Are the switches controlled by a dispatcher or control operator or a interlocking operator, or just the crew?
You don't need signals, the runaround can be in a block and the switches hand thrown. That means it really won't be a passing siding and won't be listed on the timetable page as a passing siding, its just a station. The train can use the runaround at will, BUT before the train departs in the opposite direction, it would have to get permission from the dispatcher to move in the new direction.
Assume CTC. The control points are not at the switches but are beyond the runaround, the runaround is in the middle of a block. The eastward train drives into the block under signal indication. It gets track and time in the block. It finishes its switching and runs around the train to return, becoming a westward train. It calls the dispatcher, releases it track and time an asks permission to depart in a westward direction. The dispatcher grants permission and it runs to the first signal and is governed by signal indication from there.
Dave H. Painted side goes up. My website : wnbranch.com
I'm restating a lot of what Dave has said. And I do hope he will correct my errors.
If you want signals, there are two ways to go:
If the siding is NOT signaled/detected, but the mainline is, then you can view the siding as being in the "middle" of a block--an element of trackage in that block. Then you'll have signals facing each direction out at the block boundaries. Only the mainline is detected. Here's what you'll see out at the block boundary:
Thus, when a train, or any part of the train, is on the mainline, the block's signals will show red. BUT ALSO: Whenever any switch on the mainline is thrown to diverging, it will also trigger red block signals.
If the entire train is placed in the siding AND all switches are thrown to straight through, the block signals will show green and another train may pass through the block.
So, the signals you install will be the regular pair of signals out at the block boundary, wherever that happens to be. It might be just beyond the siding switches. Or it might be a long ways out. Your choice. And there might be more track switches on the signaled mainline than just the two siding switches. When ANY of those switches are set to diverge, they should drop the appropriate signals to red.
If the siding is to be detected and signaled also, then you would place 3 signals at each of the two track switches. A total of 6 signals. The signals at "the pointy end" of the switch will have two heads, one above the other. The signals facing the other way will be single head.
When you leave this assembly of two switches and 6 signals, going down the track for aways, the next signals you will see will be the regular signal pair at a block boundary.
And, also, any track switches in any of these blocks that can be thrown to a diverging route will also drop the appropriated signals to red.
I think that pretty much lays out your signal placement options. And a little bit about how they will act.
Ed
Dave and Ed
thanks.
both responses very informative and helpful.
Never mind.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
7j43kIf the siding is to be detected and signaled also, then you would place 3 signals at each of the two track switches. A total of 6 signals. The signals at "the pointy end" of the switch will have two heads, one above the other. The signals facing the other way will be single head.
This applies whether the siding is bonded or not. The difference is that if the siding is not bonded then the best signal you can get into the siding is a "lunar", low or restricting, indication that tells the train to proceed at restricted speed into the siding. Pretty much any time you have a signal into unbonded, non-signalled track (such as into a yard) the best signal you can get is a lunar or restricting.
Generally a run-around track like you're describing (in the OP) is only used at the end of a branch line, where there's only one train running at a time. There really wouldn't be a need for signals of any kind in that situation. I lived for many years on a branch line that ended in a run-around track, and it didn't have any signals.
Signals would be needed where you had a busy single-track mainline with side-tracks or stretches of double-track where trains could pass each other. As the trains approached each other, the signals would indicate which train stayed on the mainline and which went into the siding so the other could pass.
wjstix Generally a run-around track like you're describing (in the OP) is only used at the end of a branch line, where there's only one train running at a time. There really wouldn't be a need for signals of any kind in that situation. I lived for many years on a branch line that ended in a run-around track, and it didn't have any signals. Signals would be needed where you had a busy single-track mainline with side-tracks or stretches of double-track where trains could pass each other. As the trains approached each other, the signals would indicate which train stayed on the mainline and which went into the siding so the other could pass.
Only if a form of CTC is in effect do they indicate which train uses the main track or siding. Modelers I think seem to think that all signalled track is CTC or it's equivalent. There were many fairly busy single track main tracks that only had ABS, where train orders dictated who held the main/took siding.
Even today there are main tracks with ABS where a track warrant or it's equivalent, dictates which train holds or clears the main track. We have one segment where the ends of the sidings have dispatcher controlled switches and signals, but it's not CTC. It's in track warrant territory and the controlled switches/signals are considered to be manual interlockings. To occupy the main track between the interlockings, track warrant authority is needed.
Jeff
I'm not sure if CTC would be the only situation the signals would indicate that, but yes there are situations where train orders / timetable etc. would be used. I thought about going into that, but the OP's question was about signalling a run-around track at the end of the line. I was explaining it wouldn't be signalled, with an example of a situation with a somewhat-similar track arrangement that would need signalling.
sorry to revive this, but am working on implementation
for a station siding (not run-around). There's a signal on the main indicating whether it is safe to proceed into the siding. But the siding has two tracks.
i believe one way to implement this is that the signal should indicate stop if the siding turnout is in a position to route the train onto an occupied siding track and should be clear/approach if the turnout is in a position to route the train onto an un-occupied track.
if true, the signaling system depends on turnout position
is this correct?
gregc sorry to revive this, but am working on implementation for a station siding (not run-around). There's a signal on the main indicating whether it is safe to proceed into the siding. But the siding has two tracks. i believe one way to implement this is that the signal should indicate stop if the siding turnout is in a position to route the train onto an occupied siding track and should be clear/approach if the turnout is in a position to route the train onto an un-occupied track. if true, the signaling system depends on turnout position is this correct?
"...a signal", as opposed to the plural, implies to me stub-ended station trackage. As such, you don't need any signalling at all, because the trains are in yard limits, and cannot go faster than they can see and stop. For the trackage preceding the yard, they are expected to slow down enough so that they will comply with speed restrictions when they enter the yard.
Could it be designated "within Yard Limits" ?
http://www.pcrnmra.org/conv2012/handouts/allAboutYardLimits.pdf
93. Movement within Yard Limits
Yard limits are designated by Timetable and indicated by yard limit signs.
Within yard limits, movements may be made on a main track by verbal permission of the Dispatcher (or Operator when authorized by the Dispatcher).
The leading end of movement within yard limits must operate at Restricted Speed, with the following exceptions:
Within yard limits, movements against the current of traffic must not be made without permission of the Dispatcher, who must first ensure that no opposing movements have been authorized.
Regards, Ed
7j43k"...a signal", as opposed to the plural, implies to me stub-ended station trackage.
guess i'm using wrong terminology. by station siding, I should have said passing siding on a single track mainline, turnouts at both ends.
and i'm concerned about control of a signal protecting the siding from one direction. of course there should be multiple signals at either end of the siding and in both directions, both entering and exiting the siding.
i'm also unsure of how siding turnouts are controlled at either end of a passing siding. With ABS, does a turnout position, regardless of whether it is manally switched or not, affect an ABS signal?
Ok. So we're talking about a single track, a track switch creating a parallel track, and another track switch that reconnects the parallel track to the single track.
The "multiple signals" you're talking about are typical of a CTC track with siding. Or. Each track switch is a stand-alone interlocking. Which is very similar. Maybe identical. BUT. This setup is used for high-speed heavy use trackage. I get the feeling yours isn't.
Thus. IF there are signals, they would likely by ABS type. What this means is that the trackage is divided into blocks (THESE ARE NOT NOT NOT THE SAME AS OUR DC ELECTRICAL BLOCKS. Though slightly similar). Whenever a block is occupied, the signals change from green to the appropriate color, starting with red, and "spreading" outwards. The signals don't typically protect the siding in the manor I think you're thinking of. What usually happens is when one of the two siding switches is thrown against the main, the system acts like that trackage is suddenly occupied--reds in both directions, etc.
gregc i'm also unsure of how siding turnouts are controlled at either end of a passing siding. With ABS, does a turnout position, regardless of whether it is manally switched or not, affect an ABS signal?
gregc guess i'm using wrong terminology. by station siding, I should have said passing siding on a single track mainline, turnouts at both ends. and i'm concerned about control of a signal protecting the siding from one direction.
and i'm concerned about control of a signal protecting the siding from one direction.
The signals don't "protect the siding". Since this is ABS. There will be a signal on the main track, before the points. Assuming there is only one train out there, a train approaching the siding on the main will have a clear signal. If the train has to take the siding, it will stop and line the switch. If it hasn't passed the signal, the signal will display a low (lunar) signal into the siding. It doesn't matter what position any switches are or whether there are any cars or trains in the siding or other tracks, the signal will display a low signal. There could be an oppising train pulled right up to the clearance point in the siding and the signal will still display a low signal.
If the train is meeting an opposing train at the siding and the opposing train is on the main track waiting for your train, the signal will display stop. Your train can pass the signal displaying stop without talking to anybody in order to head into the siding.
of course there should be multiple signals at either end of the siding and in both directions, both entering and exiting the siding.
Of course that only applies in CTC, NOT in ABS.
i'm also unsure of how siding turnouts are controlled at either end of a passing siding.
In ABS the siding switches are manual.
With ABS, does a turnout position, regardless of whether it is manally switched or not, affect an ABS signal?
The switch position affects the signal indication. A trailing point switch lined reverse (against the movement) will cause the signal prior to the switch to display stop or stop and proceed (and appropriate indications on signals approaching that one). A facing point switch lined reverse will cause the signals to display a restrictive signal, depending on what is beyond the switch (and signal).
[/quote]
dehusmanIf the train is meeting an opposing train at the siding and the opposing train is on the main track waiting for your train, the signal will display stop. Your train can pass the signal displaying stop without talking to anybody in order to head into the siding.
dehusmanThe switch position affects the signal indication.
i think the above two statements are contadictory.
maybe i'm confusing the signals for entering and leaving the siding tracks.
7j43kWhat usually happens is when one of the two siding switches is thrown against the main, the system acts like that trackage is suddenly occupied--reds in both directions, etc.
7j43kTypically, under these circumstances, the red doesn't mean come to a full and complete stop and sit until the signal changes. It means to slow WAY DOWN and be real cautious about what's ahead.
my primary question is about a signal for entering block with a siding. My understanding is that the signal should indicate stop if the main (siding) is occupied or if either turnout is not lined for the main.
i'll leave for later my question about one of more signals for exiting either or both siding tracks onto the main.
appreciate the responses. I think there's terminology in the responses that i don't fully understand.
Hey Greg-
There's an old saying: one picture is worth a thousand words. And there's a reason such a saying is so popular: it's true. Trying to describe your situation in words alone is very complicated and a sketch would really help.
I don't have access to AutoCAD at the moment, so I cannot produce any sketches, but on my layout there are two 'sidings' that seem similar to the topic of this thread. There is a trackplan drawn to scale on my blog and on my layout thread called 'SNSR Layout Build' in the General Discussion section.
There is a passenger station siding on the right side of the layout and a siding that serves Talleyrand Intermodal on the middle peninsula. The passenger siding is single track, and the intermodal siding is double track. Each is about 10 feet long (in N-scale) and can hold entire trains, so they could fall into the 'passing siding' category.
I use Digitrax BDL168s and SE8Cs to detect occupancy and drive signals, and I use JMRI to control the whole shebang. All turnouts are actuated with Tortoise motors. The layout can function completely automatic as ABS or as CTC with a dispatcher setting routes (and throwing or closing switches) and whatnot through a JMRI control panel. The signal aspects are set based on track occupancy for the next two blocks and on the direction the affected turnouts are set. Notice: blocks and turnouts.
Looking at the trackplan, which 'siding' describes the situation you're concerned with? Or, can you whip out a quick sketch? I'm interested to see what you mean by the 'two track siding' phrase I highlighted in your post above.
Thanks, just trying to help.
Robert
LINK to SNSR Blog
gregc But if there is a signal at each end of the siding, this doesn't seem allowed if the blocks at either end of the siding are occupied (not clear).
I don't know of any dispatcher that would allow a runaround move if either block was occupied.
The local would stay on the siding until the second opposing train past.
Signaling is hard to get until you suddenly do, and then it's simple. Except for the stuff you still don't get.
gregc my primary question is about a signal for entering block with a siding.
my primary question is about a signal for entering block with a siding.
OK. We've got an ABS signal block. At each end of the block, there's a pair of signals facing each direction. Somewhere in that block is a double-ended siding. I believe you have also added at least one other double-ended siding off of the first one.
My understanding is that the signal should indicate stop if the main (siding) is occupied
No. Because those tracks have no detection. Thus the signal system would have no input.
or if either turnout is not lined for the main.
Leave off the "or". Then you are correct. If either switch is not lined for the main, the signal system will react. In my version, the "out facing" signals go red, with preceding signals going yellow and then flashing yellow. I believe Dave is leaning towards lunar white and some directionality. But the deal is the same, in that: It's the thrown switch that inputs to the signal system, not the non-existant detection on the various siding tracks.
The deal is that ABS is the basic signal system, and it's all over the place in this country. You can get fancier, and people did/do; but it costs the railroad more money. And thus has to be justified.
I like that you are persevering.
You will note that Dave and I don't always say exactly the same thing. I think that is because I am describing basic ABS, and he is describing what I guess would be called "advanced ABS". Pretty early on, it became obvious that you could safely "violate" basic ABS, if you did it a certain way. Or maybe you could say you could "upgrade" basic ABS to be more efficient, without losing any safety features.
Efficiency and safety UP. Always a good thing.
Theoretically if you have a railroad with say 5 signal blocks there is a train in blocks 1 and 5, the one in block 1 has proceed to block 2, the dispatcher tells them to take the siding, when train 1 proceeds to take the siding it enters block 3 and the signals go red, train 2 stops in block 4, once train 1 is in the siding and the switch thrown the block goes green because there's no longer a train in its detection purview, therefore train 2 proceeds with caution into and through block 3, when train 2 is clear train one exits the siding, is this correct?
Steve
If everything seems under control, you're not going fast enough!
NWP SWP Theoretically if you have a railroad with say 5 signal blocks there is a train in blocks 1 and 5, the one in block 1 has proceed to block 2, the dispatcher tells them to take the siding, when train 1 proceeds to take the siding it enters block 3 and the signals go red, train 2 stops in block 4, once train 1 is in the siding and the switch thrown the block goes green because there's no longer a train in its detection purview, therefore train 2 proceeds with caution into and through block 3, when train 2 is clear train one exits the siding, is this correct?
Yup.
I believe I now understand that a signal provides an indication for a block and that somewhere in the block may be a siding. In other words, there is not necessarily a signal just outside a siding.
NWP SWPonce train 1 is in the siding and the switch thrown the block goes green because there's no longer a train in its detection purview
make sense to me
i've tried to illustrate all the cases in the above. Blocks are numbered left to right from 1 to 13. All the even number blocks have sidings. Each siding has a mainline and a siding track. The mainline track is shown in line with the mainline and the siding track to the side (above).
sidings 2, 6 and 8 show both turnouts aligned to the mainline track. Sidings 4, 8 and 12 show the turnouts aligned to the siding track. Sidings 6 adn 8 show the siding track occupied. Sidings 10 and 12 show the mainline track occupied.
i don't believe my logic for determining signal indications is correct. I think 6 and 12 are wrong.
please tell me which signal indications are correct.
thanks for all the help
A couple of points, first:
You don't show the block boundaries. You sort of have them in the middle of each track switch. Doesn't happen. I will assume that the block boundaries are "just outside" the points of the track switch.
Also, there's no way to reference a particular signal. Consider that there is a signal at each end of a block. For any numbered block, there's no way to know which of the two signals is which. So you REALLY should add a way to identify each signal. The block number and the signal identifier are not the same thing. It would make sense to identify each signal with its milepost location, perhaps followed by an E or W to tell which of the two signals at the location you're talking about.
Also note that on single track, each of those signals would, in fact, be two signals facing outwards from each other.
Anyway, all that said:
the signals adjacent to blocks 5 and 6 should both be green, because the track switches are aligned to the main, and the main is un-occupied.
every thing else looks pretty ok, though.
In particular, over on the right with block 12, the signal adjacent to block 12 should be red (as it is) because both switches are thrown to the siding AND the block is occupied. The signal adjacent to block 13 is displaying green because it is unoccupied, and there are no track switches thrown against the main.
7j43kIn particular, over on the right with block 12, the signal adjacent to block 12 should be red (as it is) because both switches are thrown to the siding AND the block is occupied.
i tried to illustrate that the block 12 turnouts are aligned for the siding and that the mainline track is occupied.
is block 12 occupied if the turnouts are aligned for the siding and the siding is unoccupied?
gregc i tried to illustrate that the block 12 turnouts are aligned for the siding and that the mainline track is occupied. is block 12 occupied if the turnouts are aligned for the siding and the siding is unoccupied?
Well, there IS a train there. So, yeah. The main line has a detection circuit. It picks up the occupancy and "tells" the signals. You could argue that the signal(s) should be green, because the route goes around the train, and that route is clear. BUT. That's not how it works. Remember, there's no occupancy detection for sidings. So it can't be deemed un-occupied. OR occupied. The "system" just doesn't know. So it can't issue a proceed around the stopped train. In the real world, perhaps the stopped train, knowing that there was an approaching train coming, has the brakemen go out and throw the switches (which may well be a big no-no, I don't know). This will still allow the approaching train to go by, but at an appropriate restricted speed. Which is much better than having to stop.
In this situation, if the train was there, and the track switches were thrown to the main, the signal at location 12 would be red. That's because the block is occupied, and the detection senses it.
If the train wasn't there, and the track switches were thrown to the siding, the signal would also show red. That's because the switches are thrown, and that affects to signal indication.
Either situation will cause the signal to go red. In this case, BOTH do it.
Keep in mind that the purpose of ABS signaling is to tell nearby trains that a DETECTING block is occupied. And how far ahead it is, based on the display colors. A siding is not one of those. But fairly soon after some smart person got the basic idea down, another smart person said: "Wouldn't it be neat if we pretended that a track switch thrown against the main was a sort-of occupany, ALSO?" So they did.
Not to get too involved and confusing, but rock-slide fences are also tied into signal systems, pretty much the same way. Rocks slide, sensors are triggered, and signals go red. Not because there's a train there, of course. But danger, there sure is.
7j43kIn this situation, if the train was there, and the track switches were thrown to the main, the signal at location 12 would be red. That's because the block is occupied, and the detection senses it. If the train wasn't there, and the track switches were thrown to the siding, the signal would also show red. That's because the switches are thrown, and that affects to signal indication.
ok, this makes sense. Thanks
I had started to reason that the only time the signal can be clear is if a train can proceed through the block on the mainline track. It make sense that if a train does need to stop at the siding, it should stop in the siding track and align the turnouts for the main.
so what if there is indeed a station. Would there be only a single track next to the station and it would be the siding track described above?
What if a passenger train coming from the opposite direction needs to also stop at the station?
gregc so what if there is indeed a station. Would there be only a single track next to the station and it would be the siding track described above?
For the particular station I'm thinking of (Lyle WA), the passenger trains stopped on the main line, right in front of the station. There was a siding on the other side of the main. I would imagine another train could have used that one to pass. But, like I said the platform was on the main.
On the other hand, they COULD have put the station on the siding side. But that means the siding would have had to be clear when the passenger train arrived. Which can be a pain, if someone is working that track. With the Lyle example, above, the "arrival" track is almost always clear, being the main.
I imagine there were many varied track arrangements, all built to be useful.
But. There does not HAVE to be a siding there, at all. Lyle only had them because of "other business". Without that business, they'd be stopping on the main. Of course, under the circumstances, there then might not have been a station at all. Or perhaps only a flagstop.
Remember that passenger trains were, and are, run on a schedule. Which means, in theory, the meets for those trains were planned months ahead. And put in the schedule.
Anyway, if two opposite running passenger trains had to both stop at a station, they did. If it was a regular thing, they would put a platform in on both tracks. If it was unusual, the passengers might not have a platform, and would be standing in the ballast hoping someone from the station would come and get their luggage.
thanks Ed.
i have a better understanding of how a real railroad works. A real railroad is not hectic as our operating sessions.
gregcA real railroad is not hectic as our operating sessions.
Just don't tell a dispatcher that since his job can be very hectic.
A train crew's can be a day of hurry up and wait especially a local.
BRAKIEI don't know of any dispatcher that would allow a runaround move if either block was occupied.
If its ABS, how would he know? The dispatcher wouldn't have any idea whether the train was standing on the main when it was run around or was in the siding.