nbrodar wrote:Potter to Boundbrook is a bottleneck. The dispatcher will often "fleet" trains through the area...hold the E/Bs and run all the W/Bs, then run the E/Bs or vice versa.You didn't say what the trains were. When the UPS or Juice trains appear, they have top priority. Any other trains traveling in that direction, tend to get sucked right along, with the UPS or Juice trains.
The first e/b train was a unit train consisting of double stack containers. It could have been a priority movement. However, I saw no evidence of it being a UPS train. The second e/b as I recall was short and a mixed freight, notable only for a number of tank cars carrying corn syrup.
The two w/b trains were mixed freights and appeared to be mostly empties.If by Juice train, you mean a consist of white Tropicana cars or at least reefers, I have never seen these on the ex-LV, but my watching at Potter is hardly representative or comprehensive.
Trains move over this line 24 hours per day, Saturdays comprising the least movements. I get to watch only during daylight hours and usually only for a short period once a week at most, but I have been doing so for several years.
Again, the first E/B had a Restricting signal, meaning he would have to be able to stop short of anything ahead of him. He held up until the signal went up to a more favorable Medium Approach, meaning he only had to be able to stop at the next signal.
This is a key point I question. AFAIK, the next e/b signal is some miles distant on a track that was visibly clear for at least four miles. If by a yellow signal, the engineer must be prepared to stop WELL BEFORE the next signal (presumably red at the time the Potter signal is yellow), then that is different from my understanding. From my vantage point, I could see the track ahead was clear, but to be fair, the engineer of that first stopped e/b would not have been able to see what I could see.I thought a yellow signal simply meant proceed but be prepared to stop at the next signal. At Potter, I have seen plenty of trains move ahead on a yellow at what I would consider nearly full speed. In any event, on a yellow, the next block is clear, but the next block after that is not yet clear, or so I understood.
Regardless of empty or occupied blocks ahead, the yellow in this case covers a diversion, and any diversion over a switch probably mandates a yellow.I am certain the engineer of that first e/b did what he was told to do or at least followed all the rules. It still makes no logical sense to me why he did not proceed when I have seen so many other trains do so under the same type of yellow under the seemingly same circumstances.
It was that different behavior that prompted me to start this thread. In fact, it was the very first time I ever saw a flashing yellow at Potter. No other train that I observed ever waited for a flashing yellow before proceeding.
RJ Emery near Santa Fe, NM
rjemery wrote: n012944 wrote:Quick question, not remembering who got what in the Conrail split, is this CSX or NS track?To the best of my knowledge, NS and CSX could not agree how to divy Conrail assets in the NJ-NY-PA metropolitan area as well as in the Detroit area. They then formed a new corporation, Conrail Shared Assets Operations, of which NS owns 58 percent and CSX 42 percent. In that fashion, Conrail lives on. Other assets elsewhere of the old Conrail were transferred to either NS or CSX.Thus, when we speak of Conrail today, most often we mean the new Conrail Shared Assets Operation. And to answer your question, both NS and CSX own the ex-LV line where I do my trainwatching.Conrail locomotives I have seen are painted in the dress blues scheme. Along this ex-LV line, I see NS, CSX, Conrail and foreign flag locos in about equal numbers. I have even seen a number of fallen flag locos traverse this stretch, MP being the most notable. I have witnessed a number of BNSF locos in the new and the revived warbonnet paint scheme, and a goodly number of UP locomotives.
n012944 wrote:Quick question, not remembering who got what in the Conrail split, is this CSX or NS track?
You have the split story right except shared asset Conrail is owned 50/50 by NS and CSX.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
zardoz wrote: wabash1 wrote: and you say a engineer will stop his train after a air brake application with the slack bunched so as not to get a drawbar? I never knew this. I need to get here more often and learn these things. just how does this happen?Better try it on Train Simulator first.
wabash1 wrote: and you say a engineer will stop his train after a air brake application with the slack bunched so as not to get a drawbar? I never knew this. I need to get here more often and learn these things. just how does this happen?
and you say a engineer will stop his train after a air brake application with the slack bunched so as not to get a drawbar? I never knew this. I need to get here more often and learn these things. just how does this happen?
Better try it on Train Simulator first.
what i want to know is how much air do you need to get before you stop a train because it might break? How do you bunch a train? why would it break? Ive read several pages on what a yellow signal will do for you or against you , and a appology for someone, But nothing else
wabash1 wrote: zardoz wrote: wabash1 wrote: and you say a engineer will stop his train after a air brake application with the slack bunched so as not to get a drawbar? I never knew this. I need to get here more often and learn these things. just how does this happen?Better try it on Train Simulator first.what i want to know is how much air do you need to get before you stop a train because it might break? How do you bunch a train? why would it break? Ive read several pages on what a yellow signal will do for you or against you , and a appology for someone, But nothing else
What .. you've never heard of power bunching ??? Most useful with passenger trains !!! LOL !!
Randy Stahl wrote: wabash1 wrote: zardoz wrote: wabash1 wrote: and you say a engineer will stop his train after a air brake application with the slack bunched so as not to get a drawbar? I never knew this. I need to get here more often and learn these things. just how does this happen?Better try it on Train Simulator first.what i want to know is how much air do you need to get before you stop a train because it might break? How do you bunch a train? why would it break? Ive read several pages on what a yellow signal will do for you or against you , and a appology for someone, But nothing else What .. you've never heard of power bunching ??? Most useful with passenger trains !!! LOL !!
Interesting concept--bunching the slack to prevent a drawbar.
Of course, on a downgrade it would be the only way to stop (after bunching with the dynamic). Uphill, the only reason to try that would be if the grade was so steep that the train would not be able to start in one piece (slack all stretched). But starting a train in this condition would be tricky at best: applying enough power to JUST compensate for the releasing of air, otherwise if the brakes released too soon the rear end would fall away from the front part of the train (which has already began moving in the opposite direction). But on flat ground I cannot imagine any reason to stop with slack bunched, unless the stop was part of a switching move (set out, pick up, etc).
Being as much of my operating experience was in a, shall we say, 'urban' environment, I always tried to stop with the slack completely stretched to prevent unauthorized pin-pulling.
oltmannd wrote:You have the split story right except shared asset Conrail is owned 50/50 by NS and CSX.
Web sources report otherwise. Here are two:
http://www.trainweb.org/varail/news/crmerger.html
http://en.wikipedia.org/wiki/Conrail#Breakup_and_shared_assets:_1997-1999
If you can cite better information, please do. I often wonder why a minority partner would not be squeezed by a majority partner, as happens in so many other unevenly divided enterprises, especially when the two partners are fierce competitors. It could be that while financially they are 58/42 partners, when it comes to trackage rights and access, they are treated as 50/50.
I would presume the trains running over the tracks of Conrail Shared Assets are not dispatched by either NS or CSX but by Conrail employees at a centralized Conrail facility that arbitrates movements between the two big carriers. Is that not the case?
I also wonder if Conrail engines are used beyond Conrail territory. On the ex-LV, NS and CSX engines clearly outnumber Conrail power by more than 2-to-1.
I can think of two reasons why an engineer would elect to stop on your "take diverging route" signal. And both have to do with the fact that he(she) would have an "aproach prepared to stop" signal as their last signal prior to your signal in question.
1) Once you make a set sufficient to stop your train, you must be absolutely sure that you can continue on for the distance (time) it will take to recharge your release. Otherwise you risk trying to stop with insufficient brake power.
2) Unless your train is either streached or bunched, you will have uncontrolled slack action within your train. Cars that are coupled to each other will be trying to go at different speeds, even different directions, at the same time.
kenneo wrote:I can think of two reasons why an engineer would elect to stop on your "take diverging route" signal. And both have to do with the fact that he(she) would have an "aproach prepared to stop" signal as their last signal prior to your signal in question.
kenneo,
Good suggestions. I wrote earlier there were no yards in the vicincity, but I forgot that there is an industrial spur at South Plainfield about two miles west of Potter. I believe there is a permanent Conrail locomotive at that site that shuttles cars to various plants. There are three tracks at South Plainfield not including the spur, and there are times the local power ventures onto the mainline. The three tracks are one mainline, two sidings.
FWIW, that spur was once the mainline terminating in Perth Amboy, but around 1910, Lehigh Valley began building towards Newark. When it finally arrived, the former mainline became known as the Perth Amboy Branch. Now most of that branch track has been abandoned and removed, except for about a mile or two of track serving industry in South Plainfield. The old branch has become a greenway, but Conrail has not transferred title to local government and raised the possibility of reviving the branch.
Nonetheless, there were no movements through Potter for a long period while the w/b was being held. The time of day was such that operations at South Plainfield should have already ended. I suspect the e/b approaching Potter had a clear signal up until Potter. It remains for me a curious incident.
Once you make a set sufficient to stop your train, you must be absolutely sure that you can continue on for the distance (time) it will take to recharge your release. Otherwise you risk trying to stop with insufficient brake power.
If the brake system wasn't fully recharged, wouldn't it have been imprudent to move ahead in any event? One never knows if an emergency stop becomes necessary around the next bend.
Unless your train is either streached or bunched, you will have uncontrolled slack action within your train. Cars that are coupled to each other will be trying to go at different speeds, even different directions, at the same time.
I suspect the e/b was stretched at the time it stopped. When it got the flashing yellow, I could hear the engines revving up, see the smoke billowing out of the exhausts, and the train moving forward with its alternating ditch lights illuminated. The horizontal white stripes and center emblem clearly visible a half-mile distant on the front of the diesel marked it as being a NS engine. If the train was bunched, I was near enough that I should have heard the couplers pull apart.
rjemery wrote: nbrodar wrote:Potter to Boundbrook is a bottleneck. The dispatcher will often "fleet" trains through the area...hold the E/Bs and run all the W/Bs, then run the E/Bs or vice versa.You didn't say what the trains were. When the UPS or Juice trains appear, they have top priority. Any other trains traveling in that direction, tend to get sucked right along, with the UPS or Juice trains.The first e/b train was a unit train consisting of double stack containers. It could have been a priority movement. However, I saw no evidence of it being a UPS train. The second e/b as I recall was short and a mixed freight, notable only for a number of tank cars carrying corn syrup.The two w/b trains were mixed freights and appeared to be mostly empties.If by Juice train, you mean a consist of white Tropicana cars or at least reefers, I have never seen these on the ex-LV, but my watching at Potter is hardly representative or comprehensive.Trains move over this line 24 hours per day, Saturdays comprising the least movements. I get to watch only during daylight hours and usually only for a short period once a week at most, but I have been doing so for several years.Again, the first E/B had a Restricting signal, meaning he would have to be able to stop short of anything ahead of him. He held up until the signal went up to a more favorable Medium Approach, meaning he only had to be able to stop at the next signal.This is a key point I question. AFAIK, the next e/b signal is some miles distant on a track that was visibly clear for at least four miles. If by a yellow signal, the engineer must be prepared to stop WELL BEFORE the next signal (presumably red at the time the Potter signal is yellow), then that is different from my understanding. From my vantage point, I could see the track ahead was clear, but to be fair, the engineer of that first stopped e/b would not have been able to see what I could see.I thought a yellow signal simply meant proceed but be prepared to stop at the next signal. At Potter, I have seen plenty of trains move ahead on a yellow at what I would consider nearly full speed. In any event, on a yellow, the next block is clear, but the next block after that is not yet clear, or so I understood.Regardless of empty or occupied blocks ahead, the yellow in this case covers a diversion, and any diversion over a switch probably mandates a yellow.I am certain the engineer of that first e/b did what he was told to do or at least followed all the rules. It still makes no logical sense to me why he did not proceed when I have seen so many other trains do so under the same type of yellow under the seemingly same circumstances.It was that different behavior that prompted me to start this thread. In fact, it was the very first time I ever saw a flashing yellow at Potter. No other train that I observed ever waited for a flashing yellow before proceeding.
rjemery, I don't work under NORAC rules or signals, but from what nbrodar has posted, that first eastbound was stopped at a restricting signal, not a diverging approach signal. You can't just read the bottom head being yellow without also reading the top head being red. The signal's aspect was red over yellow, not yellow for the diverging route. nbrodar stated a restricting could be for either the normal or diverging route.
That being said, running on an approach (yellow) or a restricting (red over yellow) has different requirements. Under the restricting you must be prepared to stop short of a train ahead, a stop signal, switch not properly lined, men or equipment, watch out for a broken rail and not to exceed 15MPH in this case, not just the next governing block signal.
Even if that signal would be a diverging approach (like I'm used to) there are reasons that you might not want to take it. Staying off grade crossings, already mentioned, is the best one. Between where the eb was and the next signal, how far apart are the railroad crossings in between? That stack train engr may have decided that if he had to stop and stay at the next signal, he would be blocking a crossing. Once he got the red over flashing yellow he had more room to go and would have a general knowledge of where the train ahead of him was. The second eb being short may not have had to worry about blocking anything so he followed on a restricting signal. We use our radios quite often to ask what the train ahead is doing or to let the train behind know what we are doing. Sometimes for whatever reason you don't hear someone saying they are still moving, just real slow. Then you have to decide, do I stop where I know I fit or keep going and risk stopping on a crossing.
There are other things to consider when starting to move into a situation where you may have to stop soon after starting.
If I have to stop soon after releasing the brakes, will I have enough air to stop? If before stopping, that train had set and released a few times without sufficient time to recharge the brake system, stopping again might be a problem. For that matter, he may have released his brakes and have been charging the system when the signal became more favorable.
Do I have a dynamiter (one that goes into emergency braking under a normal service application, aka kicker) in the train? If so, I want to avoid having to use air. This also ties in with using up you air supply, affecting stopping perfomance.
I have stopped at yellow, flashing yellow, even green signals when I've been alerted by radio that the train ahead is stopped and I don't fit anywhere close behind it or would be on a hill that would be a hard pull to start. Just because you have a proceed signal and all the rules say you can go, other considerations come into play that may decide for you to wait for something better.
Ultimately, to know why that engr waited, you'ld have to ask him/her at the controls.
Jeff
jeffhergert wrote:Between where the eb was and the next signal, how far apart are the railroad crossings in between?
Re Amber flashing over amber...
This should be what is classified as a "limited approach." Train would reduce to 45 or 3/4 timetable speed for this aspect, must approach next signal prepared to stop.
Now... limited CLEAR would be 45 mph only thru divergent oves in an interlocking. Then at full speed afterwards.
Speeds are specified as thus:
Slow: 15 MPH, prepared to stop short of other train.
Medium: 30 mph or 1/2 TT auth speed. (e.g., train good for 79 mph is safe for 40, 60 mph 30, etc. (50% TTOS) TTOS = TimeTable Operating Speed.
Limited: 45 mph or 3/4 TT auth speed. In other words, a coal train only authorised to do 40 mph would reduce to 30; manifest freight authorised to do 60 would reduce to 45 and a psgr train authorised to do 79 mph would reduce just below 60 mph. (3/4 TTOS)
I worked as a block operator for the B&O / Chessie System / CSX, but also studied the rules for the Conrail, as at that time, our trains operated over a portion of the (ex PRR) into Potomac Yards, so we hadda know what the indications were.
In addition, the flashing amber was a "take siding" indication. The train crew would expect to have a stop aspect displayed at the absolute signal at opposite end of siding.
Yer Hillbilly friend in TN...
Ross
PROUD father of an American Soldier
Red over red would mean a complete stop, but that signal post must be a permissive red, because I have seen trains advance slowly past the red over red.
The situation that you describe is pertinent to a "tonnage signal." Under such rules, a train is a tonnage train if its lading is > 85% engine's max. capacity. A tonnage signal, a train may pass a red signal at restrictive speed, prepared to stop short of a train, or at the next signal, at best. At the pole on which the signal is displayed there should be the letter "P" which denotes it *is* a tonnage signal.
E.g., simply put, if an engine consist is good for 100,000 tons, and train's tonnage is < 85K tons, then it is a tonnage train.
Underw8 wrote:At the pole on which the signal is displayed there should be the letter "P" which denotes it *is* a tonnage signal.
Ross,
Many thanks for the additional clarification. On this particular signal tower, there is no number or letter plate. Had there been a 'P', what would the letter represent -- permissive?
FWIW, this particular grade crossing (Potter, Inman Ave., Edison, NJ) is a busy place. At times, trains seem to average one every ten minutes. Traffic on Inman Avenue gets backed up not only because of the grade crossing but because of a nearby non-synchronized traffic light (Inman & Grove). As a result, vehicles often straddle the single track when the gates come down. Two mornings ago, with no where else to go, a truck and a train met their destiny.
A slight direction change here, if you dont mind.
As I understand it, and subject to correction, there are two types of signalling systems. One is speed aspects (such as those above with limited speed, medium, and slow speeds) and the other is routing aspect (such as diverging clear, etc).
Which system is considered the better? Is the speed system (for lack of better term) generally used on a multi main track system to control speeds thru turnouts etc? Is it possible that both systems are used in a divisional run?
What are the benefits and drawbacks of each system?
thanks,
ed
An additional question: What would a letter plate showing an 'A' designate?
On the ex-Reading Port Reading branch, operated by Conrail, there is a single track that crosses Route 35 (St. George's Avenue) in Woodbridge. At that grade crossing, there is a one head signal e/b that can show either a red or yellow light, no green. On that pole is a letter plate showing a large 'A'.
FWIW, this signal point is about 1.5 miles from a junction with the ex-CNJ, now Conrail as well. E/b trains can either go north or south on the ex-CNJ or cross the ex-CNJ into the ex-Reading yards. All these lines are active at least 24/5 if not 24/7, and several Conrail locomotives are assigned to the yards all the time.
--
Post Script: I'm going to guess that a 'P' letter plate means permissive, while an 'A' letter plate means absolute. 'A' for absolute would fit on the signal tower in question on the Port Reading Branch.
MP173 wrote:A slight direction change here, if you dont mind.As I understand it, and subject to correction, there are two types of signalling systems. One is speed aspects (such as those above with limited speed, medium, and slow speeds) and the other is routing aspect (such as diverging clear, etc).Which system is considered the better? Is the speed system (for lack of better term) generally used on a multi main track system to control speeds thru turnouts etc? Is it possible that both systems are used in a divisional run? What are the benefits and drawbacks of each system? thanks, ed
Most railroads I work with have elements of both speed signaling and route signaling; I haven't seen a pure system in awhile. This is partly due to mergers that combined speed-signaled and route-signaled predecessors, and partly due to expediency.
In very broad terms, if you need to look up turnout speeds in the employee timetable you are on a route-signaled railroad, and if you need to look up signal aspects in the employee timetable you are on a speed-signaled railroad. Either one will give you the same outcomes; you just arrive at the end by either one of two parallel paths.
I'm reluctant to state which is better as the answer depends on the goals one wants to achieve. Capital cost, simplicity of training, crew misunderstandings leading to collisions or overspeed derailments are all factors, as are the desires to have a common system standard and achieve the maximum operational capacity. I grew up in a route-signaled environment so I think I am unduly biased toward thinking that is better. People smarter than me know more about this and most of them are speed-signaling people.
Underw8 wrote:Medium: 30 mph or 1/2 TT auth speed. (e.g., train good for 79 mph is safe for 40, 60 mph 30, etc. (50% TTOS) TTOS = TimeTable Operating Speed. Limited: 45 mph or 3/4 TT auth speed
Limited: 45 mph or 3/4 TT auth speed
That's 30 mph or 1/2 maximum, whichever is less-- right? Nobody's allowed 39.5 mph thru a Medium Clear, and nobody's allowed 59.25 mph thru a Limited Clear?
As far as a crew run including both Route Signalling and Speed Signalling -- used to happen on the UP across Wyoming, as I recall. For all I know it still does. Every Caltrain commuter train on the SP main from San Fran to San Jose passes such a change.
Thanks for the reply to my question. Looking at NS's ET for the old NKP line the turnouts are all indicated by speed, usually 25 mph. I am familiar with that system, obviously not from an operational standpoint, but by observing and listening in. It seems fairly simply. The signal aspects are fairly simple and logical.
I am not that familiar with the speed system, CSX uses it across Northern Indiana, but I am not that familiar with the line, the turnouts, and aspects.
Obviously, the goal is the safe and efficient movement of crews and lading. Are there vast improvements to be made to the system (such as GPS)? Or is the system pretty much in place for the future?
rjemery wrote: Underw8 wrote:At the pole on which the signal is displayed there should be the letter "P" which denotes it *is* a tonnage signal.Ross,An additional question: What would a letter plate showing an 'A' designate?On the ex-Reading Port Reading branch, operated by Conrail, there is a single track that crosses Route 35 (St. George's Avenue) in Woodbridge. At that grade crossing, there is a one head signal e/b that can show either a red or yellow light, no green. On that pole is a letter plate showing a large 'A'.FWIW, this signal point is about 1.5 miles from a junction with the ex-CNJ, now Conrail as well. E/b trains can either go north or south on the ex-CNJ or cross the ex-CNJ into the ex-Reading yards. All these lines are active at least 24/5 if not 24/7, and several Conrail locomotives are assigned to the yards all the time.--Post Script: I'm going to guess that a 'P' letter plate means permissive, while an 'A' letter plate means absolute. 'A' for absolute would fit on the signal tower in question on the Port Reading Branch.
Current NORAC rules do not include a "P" marker. The A plate designates Rule 293c "Approach Restricting" - proceed prepared to stop at the next signal not exceeding Medium Speed. *Note* Does NOT convey block or track information.
Only red signals bearing a number plate, "G" or "R" marker may be passed without permission.
Also, all the rule books I'm familiar with designate Medium Speed as 30 MPH - not 1/2 Normal Speed - and Limited Speed as 40 MPH (freight) or 45 MPH (passenger) - not 3/4 Normal Speed.
In addition, flashing amber over amber (or any aspect for Limited Approach) is NOT in the current NORAC book. However, the CSX book contains Limited Approach as Red - Flashing Amber - Amber.
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
MP173 wrote: A slight direction change here, if you dont mind.As I understand it, and subject to correction, there are two types of signalling systems. One is speed aspects (such as those above with limited speed, medium, and slow speeds) and the other is routing aspect (such as diverging clear, etc).Which system is considered the better? Is the speed system (for lack of better term) generally used on a multi main track system to control speeds thru turnouts etc? Is it possible that both systems are used in a divisional run? What are the benefits and drawbacks of each system? thanks, ed
Ed --- Better system? Depends on what your needs are.
Speed signaling is just what the name implies. It is designed to keep trains moving faster and increase track capacity with the ability to operate trains closer together.
Your other system is Block or Track Occupancy. If something "is there" in the block, you get a red, otherwise you get a green.
So much for over simplified explanations. As you can see, both systems are combined and mixed in various ways to get the job done as best as possable. Speed signalling is usually an overlay on a Track Occupancy system (usually ABS) and can either be done automatically or by dispatcher command. Automatic Speed signalling usually is combined with CTC, but does not need to be. Manual speed signal systems require an automatic underlay and are manual only in the sense that the dispatcher must authorize track occupancy by signal indication - and that is a manual function.
Why do you need two singalling systems? Because of the safety factor built into a system - in part by FRA rule. The problem is that it takes a certain distance to stop a train, and that distance is mandated to determine the MINIMUM spacing between block signals. So, if you have a basic R-Y-G system, either the trains must operate slower, or be shorter, or the blocks longer since the engineer must have the ability to control his train safely to a stop. Speed signalling adds aspects (such as flashing green, flashing yellow, and flashing red, as well as multiple heads) gives the engineer the ability to safely control his train and still operate at the fastest safe speed because he/she is being told about track conditions as many as 7 blocks ahead (depending on how the signals are set up).
So, you have (dark) with no signal protection, manual block, automatic block (ABS), ABS with with speed overlay, ABS (with or without speed overlay) with CTC overlay. An interlocking system can be set down square in the middle of any of those systems and sometimes be a whole world unto itself.
Underw8 wrote: Re Amber flashing over amber... This should be what is classified as a "limited approach." Train would reduce to 45 or 3/4 timetable speed for this aspect, must approach next signal prepared to stop.
Ross -- I, too, remember this aspect. It was used to indicate to the approaching train that the next block was clear, the next signal did not have "Proceed", that the switch was lined for the diverging rout (siding), that the siding was clear and the switch at the far end of thw siding was lined for the siding and authorization existed for exit back onto the main. A speed overlay on CTC and ABS.
The intent was pure good. By telling the approaching engineer what the dispatcher had lined up, the thought was that there would be considerable reduction in delay and a reduction in "train handeling derailments" - which there were until the dispatcher would "take away" the signal without the trains being able to stop. OOPS!!
It didn't take long for that provision to be hard wired out of the system and a rule change implimented. Depending on the RR, the approach signal for the siding (a combination ABS, CTC and interlocking signal) could only display the standard single-head ABS indications on its upper head and the lower head could only display the switch position and permission TO ENTER the siding and to stop at the far end of it.
The absolute signal at the siding switch could only do the same. Each RR had its own combination of aspects to convey this information, but the result had to be that the approaching engineer could not know the switch position and signal indication at the far end of the siding until he could actually see it with his own eyes. He had to approach it prepared to stop short of it.
Another result of this was a rule that NOBODY could advise another what a particular signal was indication except the engineer calling a signal back to his conductor in the caboose. The dispatcher could say that he had coded a certain signal to do a certain thing, but he could not under any circumstance say that the signal displayed that aspect. The approaching engineer must see it for himself and then act on it.
When I was dispatching, I could tell a train that I had coded a certain signal to "display an indication other than stop", but the engineer was required to operate his train using the last previous signal indication. The only other thing I could tell him is, when I wanted to take a signal away from him, was, first, to ask if he could safely stop short, and if so, I was going to knock down the signal. He would then have to bring his train to a complete stop, advise me of that, then I would take away his signal and advise him he could advance to that signal at restricted speed prepared to stop short of the signal.
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