I do most of my train watching along single track railroads in central and south Texas.
When a train passes a green signal, it turns red. Assuming there are no other trains on the route at the time, in either direction, how long does the signal stay red before it turns off?
Also, how far in advance of an oncoming train does the signal switch on?
Rio Grande Valley, CFI,CFII
Some territories have 'constant lit' signals, other territories have 'approach lit' signals. Approach lit signals will turn on when a train enters the track segment in advance of the signal. The signal will display the condition of the next 2 or 3 track segments beyond the signal.
When a train occupys the track segment beyond the signal - the signal will display its most restrictive indication. When a train is occupying the 2nd track segment beyond the signal it will display some form of a Approach indication (be prepared to stop at the next signal). When a train is occupying the 3rd track segment beyond the signal, depending on the signal system being used it will display Clear or Advance Approach (proceed at maximum authorized speed prepared to comply with Approach indication at next signal).
With Approach Lit signals, when the train that lit the signal passes out of that track segment - the signal will extinguish. With constant lit signals, the signal will display a Red indication as long as the track segment beyond the signal; it will display some form of a Yellow indication when the train clears the track segment beyond the signal, it will display a Green indication when the train clears the 2nd track segment beyond the signal.
The Signal System on the railroad you are viewing may be different. This discussion DOES NOT interject how signals operate at or in approach to Control Points, where the control operator controls the lining of routes and signals.
Track segments are the distance between 'Intermediate' signals. The placement of Intermediate signals is a function of the speeds and train sizes that operate on a given territory and are predicated on service braking conditions of a maximum size train operating at maximium authorized speed. At one time intermediate signals were approximately a mile apart. During the 80's & 90's that was changed to approximately 2 miles apart. In the present day that spacing is being changed to approximately 3 miles apart.
Never too old to have a happy childhood!
BaltACD,
Thanks for your thorough and helpful explanation.
PTC will light up our approach lit signals for six miles ahead of the train.
Jeff
jeffhergert PTC will light up our approach lit signals for six miles ahead of the train. Jeff
And my grandson and I really appreciate that fact...
Brian (IA) http://blhanel.rrpicturearchives.net.
I am still foggy on what the difference is between an intermediate signal and a home signal.
Balt, could you explain this?
It sort of seems to me that it's all kind of a moving target, in that every signal is an "intermediate" signal in relation to the next one beyond it, as a train moves along.
What sets a "home signal" apart from the others?
Can't answer the home signal question. I think I know, but not authoritatively.
Watching the Deshler railcams has been an education on signals. Deshler is an interlocking, thus subject to the whims of the dispatcher - but still subject to track occupancy.
All signals at Deshler normally reside at "stop." When the dispatcher lines a train through, the route will get the least restrictive aspect possible at that moment.
I've seen the southbound CPLs at Deshler cycle through a full range of possible aspects. Train 1 will get a clear headed south and proceed through. Train 2 may be hot on their heels, or the DS may just be pre-loading the next route. The DS will line Train 2 though even as Train 1 is passing through the interlocking.
The first aspect we'll see will be "restricting." Train 1 is still in the protected block, but this will allow Train 2 to enter the block at restricted speed. Usually Train 2 isn't there yet, so we'll see the signal change to "approach," and then to "clear."
On a clear day - especially in the evening - you can usually see the next signal going south on the cam.
Once clear of the interlocking, I'm sure the signals are along the line described by Balt, with a two or three block sequence.
As a sidelight - the signals going south from the diamond are CPLs...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
With some exceptions, (I'm sure)*
Home signals are at dispatcher-controlled interlockings. Intermediates are the ones in between (normally have number plates) - also referred to as "automatics".
*2 most dangerous words on the railroad are "always" and "never".
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
Lithonia OperatorWhat sets a "home signal" apart from the others?
Helps to understand the principle behind ABS vs. fixed locations.
The pinciple of an automatic block system is to keep moving trains separated by at least the fixed distance assigned to the 'blocks' (think of them like building-blocks of a route, not 'block' in the sense of stop) net of physical stopping time. In normal practice, if you see 'red' it indicates there is a train somewhere in the physical block immediately ahead of you; yellow means in the block ahead of that one; green means at least two are unoccupied.
This does not mean that green means 'clear route'. Patenall's system for B&O improved on the ABS idea to permit route signaling: when you see a green anywhere on a CPL system it means explicitly that a train is cleared to proceed -- as one old &O engineer said 'if I see a green anywhere I go like hell!' All the other blocks ... whether vacant or occupied ... are signaled red. (Of course the automatic feature still shows red/yellow as appropriate on 'permitted' route if there is something occupying the track, or some kind of circuit fault).
The 'home' and 'distant' signals control the blocks leading up to some fixed feature requiring controlled access -- a crossing at grade or drawbridge, for example. The 'home' signal is the one governing actual access 'across' the protected stretch; the 'distant' is the warning that would let you stop in time (i.e. within 'one block') if the 'home' is red.
The principle of what to do at a 'red' signal may differ a bit, with some railroads allowing something like 'stop and proceed at restricted speed' into a red automatically-signaled block while requiring a full stop at a fixed home signal (which is, like a traffic light, governing absolute right-of-way).
Very often even when approach-lighting is in use for ABS you will find home and distant signals continually lit; in fact we have remarked a number of times that even long-abandoned routes at crossings may retain their home signals in working, lighted condition...
BaltACD At one time intermediate signals were approximately a mile apart. During the 80's & 90's that was changed to approximately 2 miles apart. In the present day that spacing is being changed to approximately 3 miles apart.
With cab signals we have 562 signalling - we have stretches of railraod with just home signals and cab signals. No intermediates at all. Other places you have one intermediate preceding the interlocking.
With PTC, will we get to the point where the signals will all be just on the screen and not standing in real life?
zugmannWith PTC, will we get to the point where the signals will all be just on the screen and not standing in real life?
There was some intensive discussion of this precise point over the years of various flavors of PTC before the current 'mandate but with overlay' business.
As I understand it, there will always be fixed indications at those 'home' locations where an absolute stop is necessary if the route is not lined to proceed. This is not just as a 'backup' to internal PTC operation; while it mirrors what the PTC cab/computer display indicates, it is still a fixed indication that crews will have to observe, call (or point and call for Big Brother, etc.)
This will probably not be true for things like crossovers used for CTC routing, although in my opinion it probably should be. Part of the reason for eliminating fixed intermediates is that as you go to a CBTC model the effective block length can change, so having any fixed-length signal confusion is counterproductive ... but you still need hard indication for potential physical full stops.
In theory laws could be passed to get rid of waysides altogether, both as block signaling and as route indication, and rely upon reasonably-robust cab signaling or CBTC for all running indications. In a perfect world that would be just great. However, the first time there's an accident on a crossing or bridge or whatever, look for the lawyers to be seeking blood of whoever was responsible for the idea... or treasure from any railroad trusting enough to implement it.
OvermodThis will probably not be true for things like crossovers used for CTC routing, although in my opinion it probably should be. Part of the reason for eliminating fixed intermediates is that as you go to a CBTC model the effective block length can change, so having any fixed-length signal confusion is counterproductive ... but you still need hard indication for potential physical full stops.
I run on cab signal territory without waysides. We know where the cut sections are (easy enough when you know what to look for).
I wouldn't put it past them to get rid of waysides in the near future.
Even with cab signals with no waysides you still have defined signal blocks. I used to know where all the boundries were, but have forgotten many of them now. When I started, most of the exCNW across Iowa was ATC/cab signal with no waysides. The few control points and some short areas where non-equipped engines to/from auxilary lines used a portion of the main had waysides.
When UP started expanding the CTC on the exCNW they added waysides. In a way it's more flexible when the cab signal fails. Without waysides if the CS failed you could only move at restricted speed until you received an absolute block. If their was a train between you and the next point (generally some kind of controlled point) that they used for limits of absolute authority, they couldn't issue an absolute block.
With waysides in the same situation they can issue authority with instructions to follow the rule that doesn't allow passing restricting/restricted proceed/stop and proceed without further authority. With waysides and no absolte block you can also proceed on those waysides not to exceed 40 mph.
With an absolute block and no waysides, speed is limited to 49 mph. With an absolute block and waysides, speed is limited to 79 mph.
I work with GCOR. I believe the rules Zug works with may be somewhat different.
zugmann With some exceptions, (I'm sure)* Home signals are at dispatcher-controlled interlockings. Intermediates are the ones in between (normally have number plates) - also referred to as "automatics". *2 most dangerous words on the railroad are "always" and "never".
Technically, under our rule book, we have neither 'intermediates' or 'home signals.'
Intermediate is a term people in the field started calling regular ABS signals between controlled points. Signals at their most restrictive normally allowed being passed under the rules without dispatcher authority.
Home signal has passed out of general usage. I have a 1968 Uniform Code that I carry with me and it no longer has Home signal in the definitions. I know older editions of the UCOR, and other rule books, had it. I bet most current working employees (at least where I work) wouldn't have a clue as to what a home signal was if you asked them. I'll ask my conductor when I go to work in a couple of hours.
Absolute signal somewhat fills in for home signal. However, not all absolute signals are controlled. The non-controlled ones can be passed in some situations under the rules without further authority.
Lithonia OperatorI am still foggy on what the difference is between an intermediate signal and a home signal. Balt, could you explain this? It sort of seems to me that it's all kind of a moving target, in that every signal is an "intermediate" signal in relation to the next one beyond it, as a train moves along. What sets a "home signal" apart from the others?
Railroad rule books that I am familiar with identify two kinds of signals - Absolute and Intermediate. Intermediate signals have number plates attached to their signal mast that display numbers, normally the Mile Post of the signals location. Absolute signals do not have number plates. The most restricive indication from a Intermediate Signal is Restricted Proceed. The most restrictive indication from a Absolute Signal is STOP! To pass a Absolute Stop signal, the train must get specific instructions from the control operator.
Note - in today's world 99% of the time the control operator is the Train Dispatcher, however, there are still a few locations where the Operator position controls switches and signals, at the direction of the Train Dispatcher.
For the most part, Absolute Signals are the signals at control points that, in addition to the switches, are manipulated by the control operator to hold or move trains on lined routes. In many cases, the Absolute signals for a control point are referred to as Home Signals.
In non-signalled territory there are railroad crossings at grade that are protected by interlocked signals. These absolute signals are normally 'protected' by a Distant Signal - that normally displays a 'Restricting' indication to approach the next signal prepared to STOP. The Absolute signal protecting the crossing is nominally referred to as a Home Signal for that location.
In some cases, there may not be any intermediate signals between control points, and if the signals have been lined by the control operator they will act in the same manner as intermediates. This got CSX into trouble when a created a new control point less than a mile from a existing control point - When the existing control point signals were at stop and the new control point was lined, the indication displayed was Approach - with there being less than a mile between the two locations a train moving at track speed when seeing the Approach indication did not have braking distance to stop at the old control point - The error was quickly corrected and if the old control point was at stop the new control point was configured to display restricting and the signal in advance of the new control point displayed Approach.
From what I have observed in my travels, all railroads in the USA follow the convention of no signal numbers on absolute signals, and numbers on the intermediate signals, with an odd digit at the end of the number(nearest odd tenth of a mile) for signals going away from the zero milepost and an even digit at the end of the number (nearest even tenth of a mile) for signals going towards the zero milepost. To add clarity, when all tracks are signaled for traffic in both directions, each numbered signal has the number of the track it controls in its number.
And, also from observation, in Canada, you can expect all signals to be numbered and, as I recall, absolute signals have two or more heads whereas intermediate signals have one head each (one of our good friends up north described the distinction in response to a question I asked several years ago).
Johnny
Thanks to everyone for the very thorough responses.
A couple of questions.
What does the term "absolute" block mean?
And, Jeff, you mentioned a situation in which a train can pass the most restrictive aspect without permission of the dispatcher. I don't get that. You mean, even if it's red? It seems I've read about passing red signals, but my impression was that first the train had to come to a complete stop, and then had to proceed at the speed (I can't remember the term) which assures that the train can stop within half the distance of the engineer's vision. Is that what you were referring to?
Lithonia OperatorThanks to everyone for the very thorough responses. A couple of questions. What does the term "absolute" block mean? And, Jeff, you mentioned a situation in which a train can pass the most restrictive aspect without permission of the dispatcher. I don't get that. You mean, even if it's red? It seems I've read about passing red signals, but my impression was that first the train had to come to a complete stop, and then had to proceed at the speed (I can't remember the term) which assures that the train can stop within half the distance of the engineer's vision. Is that what you were referring to?
The most restrictive signal a signal with a number plate can display is Restricted Proceed - signal can be passed without stopping and not exceeding Restricted Speed (15 or 20 MPH depending on whose rules are in effect) and being able to stop within 1/2 the range of vision. The Dispatcher does not need to be contacted to pass a 'red' signal with a number plate. The Dispatcher must be contacted and must issue authority for a train to pass a 'red' signal WITHOUT a number plate.
Absolute Block basically goes back to the days of the Manual Block system. Blocks could be 'given' to a train as Clear or Occupied (note these blocks apply to trains moving in the same direction). A train operating with a Clear Block is being told that there are no trains ahead. A train operating with a Occupied Block is being told that their are train(s) ahead. In the days of Manual Blocks, trains had to provide Flag Protection against following trains - unless - the train was given a Absolute Block - which meant that no trains would be permitted to follow the train holding the Absolute Block.
When CSX first implemented CADS and their Direct Traffic Control in unsignalled territory there was a item in the block authority that told the train if they had to provide Flag Protection or not (note - with 2 man crews riding the head end - crews were always relieved from flag protection).
On CSX's RF&P sub-division when a train has 'Train Control' failure they cannot be permitted to follow a passenger train into a track segment - a Absolute Block must be maintained between a passenger train and a following train wtih inoperative Train Control. This was before PTC was implemented on the RF&P, I have no idea what the current procedures are.
LO: Here's the current NORAC Signal Chart (which you've probably already seen a version of for one railroad or another). The various aspects are explained. While there are variations by railroad, the basics are there.
One condition that isn't shown there but I know is in use at least on CSX is the "G" marker on the signal mast signifying a grade. As I recall, a tonnage train (and possibly others) can pass such a signal without stopping, albeit at restricted speed.
Larry, did you forget a link?
Lithonia Operator Larry, did you forget a link?
Yeah, and I closed that window. Found it, though.
https://signals.jovet.net/rules/NORAC%20Signal%20Rules.pdf
Thanks!
Seems like a video illustrating how the signals change as a train moves past them - especially a video with different segments for different types and complexities - would be a good way to explain this, Anybody know of one?
- PDN.
tree68 LO: Here's the current NORAC Signal Chart (which you've probably already seen a version of for one railroad or another). The various aspects are explained. While there are variations by railroad, the basics are there. One condition that isn't shown there but I know is in use at least on CSX is the "G" marker on the signal mast signifying a grade. As I recall, a tonnage train (and possibly others) can pass such a signal without stopping, albeit at restricted speed.
DeggestyLarry, I would not be surprised if all roads that felt a need for such used the "G" signal; I know that the Southern did.
Nor would I - it just doesn't appear on the chart I linked.
Paul_D_North_Jr Seems like a video illustrating how the signals change as a train moves past them - especially a video with different segments for different types and complexities - would be a good way to explain this, Anybody know of one? - PDN.
I'll try to find one.
But I get the general idea. Let's assume a single-track line, and we're at a town called Jonesville. Train #3, facing west, is stopped, looking at Signal X (the signal faces east). Up ahead, going the same direction, is Train #1. Let's say Train #3 has no reason to move forward for a while (lunch break?). While #1 is in the first block past the signal, Signal X shows red (or equivalent). While #1 is in the second block, Signal X shows yellow. Once all of #1 is in the third block, Train #3, still sitting at Signal X, will see green.
But what about if, instead, #3 wants to get going ASAP? What I'm still not clear on is if a following train (like #3) is ever allowed to be in the same block as #1.
Let's say the block is three miles long, and the MP at Signal X is 17, with numbers ascending. Is there ever a situation where the dispatcher might say to Train #1, "Let me know when your engine passes MP 19," and then once he hears that, he lets #3 pass the red signal* and proceed at a certain prescribed speed, maybe even at the same speed as #1? (*or dispatcher causes the light to turn yellow or green? However, my understanding has been that in a simple ABS setup, the dispatcher would not be able to change that light's aspect.)
* * *
If the signals are approach-lit, would Signal X would be dark if no train was approaching in the block before Signal X (or sitting there like #3 had been), but there is traffic ahead in the next three blocks, either same-direction or opposing? In other words, let's say a particularly handsome railfan with the unlikely name of "LO" arrives at the track, at Signal X, shortly after #3 finally goes on his way westward. There is nothing approaching Signal X to trigger it. Will LO see anything lit while #3 is still in the first 2 or 3 blocks after Signal X? Will he see the signal go red-yellow-green?
Say LO hangs around a while at Jonesville. No more westward trains will run that day, to approach-trigger Signal X. But after a while, an eastbound (#2) starts making its way from distant Caseyville toward Jonesville. Will LO see Signal X go from green to yellow to red as #2 approaches? (Remember, I'm still talking approach-lit.)
Lithonia OperatorBut what about if, instead, #3 wants to get going ASAP? What I'm still not clear on is if a following train (like #3) is ever allowed to be in the same block as #1.
What I've seen at Deshler is that the following train will get a "restricting" of some sort - ie, proceed at restricted speed. Thus, your train #3 can follow Train #1 at a suitable distance. Keep in mind that this is an interlocking. In "intermediate" land, that would likely require permission of the dispatcher vs a signal indication.
If the signal is automatic (not controlled by the dispatcher) then a train can pass it at red, not needing anyone's permission, and run at 15 mph or so, watching carefully.
But they can't exceed that slow speed until they reach the next signal -- so might be faster to wait for the first signal to turn yellow, at least.
If our train (A) in this example has been sitting at a control point (end of a passing siding) and the train ahead (B) has cleared all of the track sections to the next control point (or siding) and the dispatcher has not changed the direction of traffic, train (A) will still have a clear signal displayed. If however the dispatcher wants to send train (Z) toward train (A) he will have to change the signal that (A) sees and wait for a timer to run (so the train would have time to stop if it was at speed.) After athe time has expired. the dispatcher could then clear the signal that (Z) would need to proceed toward (A). A section of track between control points has a direction of operation (I am assuming a single track situation here. Some double track stretches have assigned directions but most today have bidirectional capabiity) If our train (A) had been following another train (B) between control points and stoped at an intermediate signal before the next control point, then A still has the block and the dispatcher can NOT clear a signal for (Z) to enter the block.
Lithonia OperatorSay LO hangs around a while at Jonesville. No more westward trains will run that day, to approach-trigger Signal X. But after a while, an eastbound (#2) starts making its way from distant Caseyville toward Jonesville. Will LO see Signal X go from green to yellow to red as #2 approaches? (Remember, I'm still talking approach-lit.)
If this is single track, and a train is approaching handsome L.O. he will not see a green (clear) indication. He should see a red (STOP) indication because the block is occupied and the direction has been set toward him. Don't want no cornfield meets on this rairoad. On the BNSF racetrack (Chicago to Aurora) the three tracks are all bidirectional and always lit. And the signals are great for indicating when a track is cleared for a train except that sometimes there is no traffic scheduled so the dispatcher may have it set for "fleeting" so after a scoot has gone, it goes from Stop to Approach to Approach Medium, to Clear and stays that way until the next (hourly) scoot or a freight comes along.
Our community is FREE to join. To participate you must either login or register for an account.