Neophyte signaling questions

[wabash1]

You can pass a stop at a interlocking in abs if you follow the rules. if it is an automatic interlocking follow the rules posted if it is a manual interlocking you are at the mercy of that operator who controls the interlocking.

Mark you are right about restricted speed of 2 trains occupying the same block only if they are opposing moves. this is something i didnt mention. if both trains are going the same direction they can have overlapping limits and not haft to run restricted. the signal system keeps them far enough apart to keep any accident from happening. I didnt want to bring this up as not to confuse anyone. on opposing moves limits defined speed etc. Track warrents can be hard enough with out getting into all the exceptions. i was just trying to keep all the trains going one direction.

what we call positives ( i think absolutes as you define them ) is stop signals that cant be passed with out authority. my authority might be a track warrent or the dispatcher. the case i cited was if you couldnt get the dispatcher the rule says as long as i have a track warrant i can go. but i haft to pass the signal 100ft wait ten minutes then go at restricted speed.

Dave what is a stop and proceed signal ? I have never seen one that i know of.

[PNWRMNM]

Dave,

That is a new one on me. Never heard of absolute signal leaving a siding in ABS.

This was a fun talk though. Thank You.

Mac

[dehusman]

On the ABS I am familiar with the signal system is set up so, as you approach a siding, the signal over the first switch is a stop and proceed and the leaving signal is a stop signal (absolute). When the signal system was set up you had to get the DS's permission to pass the Stop signal, so as original set up it was an "absolute" signal. Since then the rule books changed to permit a train to pass the signal after the 10 min wait.

Dave H.

[PNWRMNM]

Dave,

I think we are closing in on the point. I do not recall seeing an absolute signal outside interlocking limits, the headline of Rule 9.12.4.

If it was automatic interlocking at a railroad crossing Rule 9.12.4 does not apply. If a drawbridge, you would again be in interlocking and Rule 9.12.4 does not apply.

For what reason would you have an absolute signal in ABS ouside of an interlocking? I agree that this rule gets you by a stop siganl in ABS. It is the notion of an absolute signal in ABS that I am having a hard time getting around. Kind of like a spotted zebra!

Mac

[dehusman]

Mac,

We may be having a difference of opinion due to differences in the signal systems between railroads. Yes, I was talking about ABS-TWC with 9.12.4A.

And yes it will get you by an absolute stop signal, which is defined in the GCOR as "A block or interlocking signal without a number plate, or designated by an A marker. " You can have signals in ABS territory without number plates (the trerritories I am familiar with do), so that makes them absolute signals and they do display a Stop indication. Rule 9.12.4A is the rule that applies to get past them. It is entirely possible that your road doesn't have absloute signals in ABS (every signal has a number plate) so you may not have seen that.

If that rule doesn't apply, what rule would you use to pass a signal displaying Stop (red light, no number plate) in ABS-TWC (not CTC, not at an interlocking)?

Dave H.

[Anonymous]

Dear everyone,
Thank you for everything you have taught me. I never imagined signaling was so complex. I am deeply grateful.

Most sincerely,
Daniel

[Anonymous]

First off, let me say that all these questions and my answers revolve around single-main-track operation. Multiple main tracks or double-track (they are not the same thing!) are different. Double-track is directional, handed, one-way. Multiple main-track is either direction, either track. (GCOR has recently fuzzied this distinction, which I don't think is a good idea, but what do I know.)

In DTC, a block has fixed, permanent limits, listed in the timetable and posted at trackside.

In TWC, a block has temporary limits that last only until the warrant is fulfulled or annulled.

In CTC, the block is between absolute, controlled, signals. They must be controlled -- you can have an automatic interlocking in the middle of CTC (and often do), but those are not controlled signals and therefore cannot be the beginning or end of an authority.

Scott, your example of following trains would work like this. What you've described is a main train operated by CTC. Both trains can have authority within the same CTC block so long as they are (a) directional and in the same direction (following); (b) directional and moving away from each other; (c) both on track-and-time moving in either direction.

The CTC signal acts like an ABS in the example of a following train. Suppose the first train has just passed the absolute signal. It displays red, because the signalling block it protects is occupied. Now the first train passes the first intermediate beyond the absolute. Now the absolute can be cleared for the following train, and will display yellow. The dispatcher may have already requested the signal, but it won't clear until the first train is past the first intermediate. And so forth -- the absolute goes to flashing yellow, then green, as the first train proceeds past additional signals.

To just complicate things further, most ABS systems in the U.S. today are APB-ABS -- absolute permissive block. That is, they are Absolute for opposing moves and Permissive for following moves. Early single-track ABS systems were not ABP, and allowed only one train at a time to move between sidings -- not so hot when you want to run a lot of trains.

A dispatcher can also talk the following train past the signal, which you would do, for example, for a helper that needs to come up to the first train and couple on. I don't have the rule book in front of me, and after three years I'm increasingly fuzzy on details, but I believe you do not have to tell the first train you are doing this, because the following train will by rule have to move at restricted speed, and if the first train wants to make a reverse move (which it can within the same block without permission) it also has to do it at restricted speed. But I would tell the first train anyway that there was a move permitted behind them.

The key point to remember about CTC is that all it really is, is an ABP-ABS system that a dispatcher can make requests of. The dispatcher cannot actually clear a controlled signal, he can only REQUEST that it be cleared. If the signalling system sees no conflicts, it will grant the request. All the dispatcher controls is the direction of movement and the position of controlled switches (normal for the main track, reverse for the siding or spur or junction track). The dispatcher can prevent controlled signals from clearing -- that is, the controlled signal will not clear on its own unless the dispatcher has asked it to. That's essential so you can protect a track-and-time in a block -- it wouldn't do to have a maintainer out there on track-and-time and the signal clear for a train to enter the block!

The dispatcher has no control over ABS signals at all. They do their own thing.

As for TWC and DTC, trains can only be within the same limits if they are joint, both operating at restricted speed.

[Anonymous]

Yeah, That cleared it up. Evvery single Absolute I go by (There are 4 for the 55 miles travelled) are CTC controlled. So thats where my mistake is.

Yeah, I got it now Wabash, thanks.

[PNWRMNM]

Dave,

You are in ABS territory with rule 9.12.4A. This rule does not get you past an Absolute signal as you claimed in next previous post. I stand by my previous answer.

Mac

[wabash1]

Kevin

What i was saying is that in track warrent territory with abs signals this is the way it is done. EXcept ( i didnt put this in as not to confuse anyone) at interlockings . the dispatcher wont have controll of the interlockings in abs territory.

In other words as long as i have a warrent to proceed past the absolute signal and i cant get radio contact with the dispatcher provisions allow me to go 100ft past signal wait 10 min then proceed at restricted speed. dont mix ctc with abs they are 2 differant critters.

In the senerio i gave the absolute would be at the end of another siding .

mac and kevin in ctc territory the absolute are differant than in abs. to understand track warrents( this is what i was trying to clear up) just think of them as a ticket to go from point "a" to point "D" . On the ns are track warrents are only 1 small page with 12 boxes. the BNSF has at least 25 i know of.. less is better. the way the ns likes it is give all the info in the smallest amount of words. but back to the lesson in twc once granted and the ik time is recieved the only way this warrent is no good is if i give it up. it cant be changed or altered. so if the dispatcher made me mad i can run slow and hold up the railroad and there is nothing he can do about it. in ctc he can take a signal back ( if you are not close and no chance of running a stop) and hold you for a opposing train. with out telling you. this is why in abs and track warrent territory you can pass a stop with out being fired as long as you have athority to go further.

hope this clears it up some.

[dehusman]

9.12.4 A.
On a main track, after stopping, a train authorized beyond signal must comply with one of the following procedures:
1. If authority beyond the signal is joint with other trains or employees, proceed at restricted speed.
or
2. Proceed at restricted speed when crew member has contacted the train dispatcher and recieved permission to pass the Stop indication. However if the train dispatcher cannot be contacted, move 100 feet pest the signal, wait 5 minutes, then proceed at restricted speed.

[PNWRMNM]

Dave,

I do not find the provision you are quoting in my GCOR.

Rule 9.12.1 and 9.12.2 provide for dispatcher or control operator to talk a train by Stop indications in CTC and Manual Interlockings respectively. That is only way by an absolute stop signal that I know of.

Mac

[dehusman]

Under the GCOR trains stopped at a Stop signal (absolute stop signal, no number plate) are to attempt to contact the dispatcher. If they cannot, and have authority past the signal, they pull 100 feet past the signal, wait 10 minutes then proceed at restricted speed.

Dave H.

[Anonymous]

QUOTE: Originally posted by wabash1


Now lets say that there was no number plate at the 49 it was a absolute signal and it was red i must stop. get permission by the signal and proceed at restricted speed. because of the track warrent i have i proceed to outback (mp22) and lets get goofy here the radio just caught fire the conductors battery went dead on his radio and no way we can use cell phones ( no signal ) i pull up and stop at the 49 a stop signal. can i pass it? yes i can, i have athority to proceed but i must pass the signal , stop wait 10 min and then proceed at restricted speed. My athourity to out back allowed me to proceed with out communication with the dispatcher.

Wabash, Everyhting you said was perfectly Clear, Except that paragraph above. I might be looking at htis like a dumb Idiot, But up here, apssing Absolute signals is a no no, unless I get a 567 from the disspatcher.

Thats never happened, and doesnt happen often, But I don't see how a 567 would affect Absolute signals and the movement of trains and the ability to pass them, however the 567 is what we need to be able to pass an absolute signal.. Someone know how these two corrilate?

QUOTE:
567 JOINT WORK AUTHORITY TRAINS AND ENGINES

(a) More than one train and/or engine may be given joint work authority which permits movement in either direction within the specified limits. Each crew requesting such authority will communicate with the RTC. Such communication must include the occupation and name of the crew member, the train or engine designation, the location, the required limits and the track or tracks to be used. Each such train or engine must be instructed:

'Protecting against each other.' When so instructed, and protection other than that prescribed by Rule 99 is to be provided, the conductor and locomotive engineer of each train or engine must first have a thorough understanding in writing with respect to the movements of each train or engine and the protection to be provided.

(b) Before issuing joint authority, the RTC must;

(i) ensure that there are no trains or engines in the affected limits, other than the trains or engines which are to be authorized; and

(ii) block at Stop all devices controlling signals governing trains or engines into the affected limits.

(c) The RTC must maintain signal blocking against all trains and engines and must not authorize any train or engine, other than one which is thereby protected, to enter the affected limits until the work authority has been cancelled. Each train or engine must be clear of the affected limits before the work authority is cancelled.

EXCEPTION: If the work authority remains to be cancelled to only one train or engine, it may be cancelled while that train or engine is within the affected limits. In such case, the conductor or locomotive engineer must inform the RTC of the intended direction of movement. The RTC must maintain signal blocking against opposing trains or engines until the protected train or engine has cleared the controlled block.

(d) When the authority specifies: "Call RTC_________," the conductor or locomotive engineer of each train or engine so instructed must communicate with the RTC as instructed.

(e) The authority granted and instructions received from the RTC must be in writing. The locomotive engineer, of a train or engine so authorized, must be made aware of the track limits before any movement is made by that train or engine.

Or Am I mixing apples and Oranges?

[wabash1]

maybe i can help clear the mud to just dark water .

In abs system it is a signaling system that tells track condition only. nothing more nothing less. A block is the section of track between to signals governing movement in the same direction. and a absolute block is a section of track that can only be occupied by 1 train or engine at a time.

TWC - track warrent controll can be in abs or dark territory . you can have trains overlapping in twc in dark territory following each other but you must have the rule 99 flag protection not required for following trains . ( it gets worse but hang in there) if i am running in dark territory with a train following we stay in radio contact knowing where each person is and knowing train size helps. if i am at milepost 5 and i am 1 mile long my rear just cleared mile post 6. the train at mile post 10 is 4 miles behind and safe. if i go into emergency i must announce this over the radio and the following train will stop. this keeps me from having the conductor get off the train run 2 1/2 miles back to flag stop the train behind . rule 99 says we dont haft to flag the train.

the other way it is done in same circumstance is the dispatcher will give a warrent to the following train only to my last "os" I might get a warrent from mile post 20 to mile post 0 a procede with a rule 99 checked. in 10 min the dispatcher might ask for my location . this is a must not lie or strecth the truth ever. if i am at mile post 17 dont tell him 12. cause they will "os" ( last location) of rear of train 3miles ( mile post going down 20-19-18 etc.) back. so he says i am clear of the 15mp.( remeber i said i was at the 12 when i am realy at the 17 we stopped for icecream) and at mp 16 we go into emergency. train "B" has a warrent to the place i said i was clear of 15 and hits the rear of my train at the 17mp ( remeber this is dark territory no signals.) this is the reason for good communications and absolute blocks.

Now we go to TWC and ABS. the signals in abs are set to tell track conditions. ( remember that a block in abs is section of track governed by signal in same direction) Ok i have my train I am heading south at 43 mph down hill ( darn ge engines) and at the 51mp the signal is clear that tells me that the track is clear to the 50mp.My track warrent tells me to go to outback and hold the main ( out back is at the 22mp) when i get to the 50mp its yellow ( approach) i must slow to 30 mph and proceed prepared to stop at next signal. the yellow tells me nothing is in the block ahead but at the 49 might be a red . so i get to the 49 mp and it is red with a number plate. I am now going to run restricted speed. ( not hard for a ge engine to do) the red tells me that something is wrong in the next block. broken rail train or engine track equipment or a railcar switch lined improperly or derail left off. or a trainmaster doing a banner check. I dont haft to stop at the signal cause of the number plate. the signal at the 48mp is green so i can resume track speed after headend goes past the signal.

Now lets say that there was no number plate at the 49 it was a absolute signal and it was red i must stop. get permission by the signal and proceed at restricted speed. because of the track warrent i have i proceed to outback (mp22) and lets get goofy here the radio just caught fire the conductors battery went dead on his radio and no way we can use cell phones ( no signal ) i pull up and stop at the 49 a stop signal. can i pass it? yes i can, i have athority to proceed but i must pass the signal , stop wait 10 min and then proceed at restricted speed. My athourity to out back allowed me to proceed with out communication with the dispatcher.

the twc is a athority to move or occupy a section of track the block signals is only a condition of how i will move. both work together but are seperate. In TC ( what they might be calling DTC) is signal indication green go red stop only way you pass the red is by a green or a dispatcher giving you the right to do so.

I hope this helps.

[Anonymous]

Dear Mr. Hemphill,
I would like to thank you very much for your time, information, and above all else, patience. They are most appreciated.

Most sincerely,
Daniel

[Anonymous]

Daniel:

A good question. I'm not sure I can explain it satisfactorily (can someone else?). At this point, you really need a rule book to go into this kind of detail.

I have to partially start over to try to answer it. An ABS -- automatic block signal system -- does not convey authority to occupy the main track. It merely advises of track conditions ahead. The following things will turn an ABS signal red: a broken rail (most of the time), an open switch, and a train in the block. This gives you a higher degree of safety than no signal protection, and the FRA (and before that the ICC) allow you a higher maximum track speed as a result. Since an ABS system conveys no authority, you must have something that gives it: a train order, track warrant, DTC authority, yard limits, timetable, signal indication from an absolute controlled signal -- one of these. These signals are called automatic because they respond to track conditions entirely on their own. They are not controlled by anyone.

A manual block is merely a paper system that divides the railroad into blocks. It's called manual because a human assigns the block. The block limits are established and fixed, but they only exist on paper (and a signpost at their entrance). Unlike an ABS, they do not automatically clear themselves or assign themselves. And unlike an ABS, they DO convey authority but DO NOT tell you anything about track conditions.

In manual block, by rule you cannot have two trains in the same block at the same time unless both are at restricted speed (prepared to stop in half the limit of vision short of train, engine, red signal, men and equipment, and open switch, keeping a sharp eye out for a broken rail and not to exceed 20 mph). In ABS-TWC, there are no blocks per se, only "signaling blocks" which have no authority attached to them at all. TWC rules allow you can have two trains in the same signalling block at the same time without both being at restricted speed, so long as train ahead is directional and moving away from the following train, and so long as the trailing train is running at restricted speed. Thus it is less positive of a system, and so is restricted to 49 mph maximum unless it's got a ABS system on top of it.

If you pencil this out, you'll see why manual block is more positive. Since you can't put two trains in the same block without both going to restricted speed, a following train cannot enter a block until the train ahead has completely left it. So there will usually be a full block of space inbetween the trains. But in TWC (with or without ABS), you can put the following train right up to the train ahead's rear end all the time.

Take a look again at what Mac pointed out in a previous answer, that CTC sits on top of ABS. In between the absolute signals at control points (no number plates) are ABS signals (with number plates). An absolute signal gives you authority all the way to the next one, regardless of how many ABS signals are inbetween, and regardless of what the ABS signals might indicate. The block, in this case, is absolute signal to absolute signal.

I think where you're getting confused is that there are two types of blocks -- one that grants authority, and one that's a wiring block between two signals. The first grants authority, the second doesn't. They can be the same physical dimension, or not.

Laps are overlaps of authority. Since an ABS system conveys no authority, they cannot create laps. They might protect a train crew from them, however. If two opposing trains both have authority to occupy the same piece of track -- they have a lapped authority -- the signal system will tell them that there is something out there, first by turning yellow, then red. To pass the ABS signal the train must reduce to restricted speed. In the worst case scenario, assuming everyone is obeying the rule and really IS running at restricted speed, the two trains will meet and the two front couplers will kiss . No damage done, but clearly a rules violation by someone.

Ain't no shame in asking questions, my rules instructor used to tell me: "The only dumb question is the one you didn't ask."

[Anonymous]

Dear everyone,
I would like to express my greatest gratitude for all you have taught me. I have learned more about how railroads operate in the past half hour reading your responses than I have learned in the past five years.
However, what you have taught me has raised two new questions in my mind. Please forgive me if I missed something in what you have written that already answered these. Firstly, what if anything is the difference between ABS and manual blocks? Secondly, if TWC systems are designed to prevent lapping, why does TWC territory have signals? If I have misunderstood what you have been telling me, then I am quite sorry.

Deeply grateful,
Daniel

[Anonymous]

Scott: I think I am correct in not inferring that you said I said DTC was foolproof. I only said that it's perceived to have certain safety advantages over TWC.

"After arrival of" provisions have been stripped out of TWC on some railroads as well. I can think of at least 10 recent collisions, some fatal, mostly between trains and maintenance-of-way equipment, due to failure to wait for the train specified in the "After arrival of" line. There's nothing inherently unsafe with that aspect of the rules so long as people obey the rules. If they don't ... God help them.

OK, so people seem to get the After arrival of feature wrong. But stripping it out isn't a perfect solution, either. Without that line, you force two authorities instead of one onto the dispatcher and train crew: one to get the train to a meeting point, and a second at some later time to get the train out of the meeting point. That slows everything down, and doubles the opportunity for a missed repeat.

I am baffled how "dispatcher error" could have any inclusion in the cause of the accident you discuss, based on the information you provide. I read the NTSB report you linked (which is only a summary, unfortunately). All dispatcher transmissions are taped. He or she either issued a valid DTC authority, or they issued an invalid DTC authority. The crew said one thing, or they said another thing. Period. There's no room for argument here in the example you cite. DTC authorities are created on a computer, which has built in logic-checks that prevent lapping authorities. You cannot override the machine and create a lap. However, you CAN read one thing on the screen, and tell the crew another thing -- and I know of instances of it, both accidental and believe it or not, intentional. But that would show up on the tapes, because the DTC computer records every key stroke and display. If it showed one thing, and you said another thing, you are pulled from service on the spot, and in this case, probably fired.

After an accident, the tapes are impounded. The rules men show up, get the tapes, go to an empty console, and replay the display and the radio and telephone conversations in real time. In about one minute, they will know who made the error. The NTSB investigators listen to the tapes, too. I suppose it's possible that conspiracies to cover things up occur, but since there's no percentage in a cover-up for the rules men, the railroad, or the NTSB, one might as well also think it's possible for the sun to come up in the west tomorrow morning.

I went through one investigation during my time as a dispatcher. It started like this: about three hours after my turnover, the Chief called me at home and woke me up. "Markie," he asked, "Do you recall telling the crew on train such-and-such to do such-and-such at about 1 a.m.? "Sure do," I replied, "and if you go listen to the tapes, you'll know it for yourself." "Oh, you know we'll be doing that," he said. "Now get some sleep and we'll see you tonight."

What the Chief was doing was offering me a "Come to Jesus" in case I really had screwed up. In fact, he'd already listened to the tapes, and was only checking to see if I knew something that wasn't there. If you lie, and they catch you, you will be SO fired. If you confess, you might only be fired for a few days or a few months, depending on your record and the egregiousness of the rules violation in question.

There is no substitute for vigilance and adherence to the rules.

[Anonymous]

Larry's post came in while I was typing.

QUOTE: Originally posted by tree68

(Random thought - they should name it something. "South end siding Philadelpia" is a bit wordy compared to the examples above.)

If you think that's bad, the Montana Rail Link has a siding called "West End," complete with siding end names "West West End" and "East West End."

Scott

[tree68]

I listen regularly to radio traffic on the Montreal Secondary - Syracuse to Massena, NY. Mark's comments on tracking locos are reinforced every time I hear a NORAC "Form D" given out. The only question the NE dispatcher ever has for the crew is which unit is in the lead, most often on the locals, as they can get turned around.

The "Form D's" I hear usually refer to specific landmarks (those little signs along the side of the track - KALB, RIVER, RICE), although I do hear an occasion reference to a milepost, usually for the locals, and the south end of a siding that is the location of many meets. (Random thought - they should name it something. "South end siding Philadelpia" is a bit wordy compared to the examples above.)

The track usually given a train by the DS ranges from one section (between two adjacent landmarks), to the entire line (from current location to terminus of that train). It all depends on traffic at the time. If there is a lot of traffic, the DS will ask the crew to "Give me BRAD (or whatever) when you can" so he can give that block to a following train.

While I've seen references to "Form B" in the forums, I'm pretty sure that I hear the track foreman getting Form D's if they take a section of track out of service. If the track is capable of handling a train during the maintenance window, the train crew must clear it with the foreman who has the Form D.

[CShaveRR]

Hmmm...there are signals I've wanted to give to some neophytes, but you won't find them in the GCOR!

[dehusman]

DTC has its origins in manual block.

TWC has its origins in train orders.

Dave H.

[edblysard]

Kevin,
Neophyte signal are the signals given by brand new conductors and switchmen.
Usually ignored by old head engineers, thank god!
Stay Frosty,
Ed[swg]

[Anonymous]

Daniel: Mac and Dave have done an outstanding job of providing concise yet accurate answers for you, not at all easy given the great complexity of the questions asked you asked. I would highly recommend you search in Google for GCOR (General Code of Operating Rules). You can find it as a pdf, but expect to print out a few hundred pages. It has a list of definitions at the end which will answer some of your questions and explain stuff that we can't get into here, unless we want to retype the whole thing!

I dispatched extensively in DTC territory at Kansas City Southern, and learned TWC at BNSF, so I think I can add a few things to Dave and Mac. SP was a major user of DTC, but as far as I know UP has by now converted all SP DTC territory to TWC. KCS continues to use DTC. Of interest, KCS DTC is actually a manual block authority, which allows trains faster maximum speeds. Normally, "dark" (unsignalled) territory is limited to 49 mph for freight, but if you have manual blocks you can exceed that.

Originally, all railroads dispatched by timetable and train order. The timetable established authority for every scheduled train, designating meeting points and the exact time a train left a station -- the train could run behind its timetable time, but NEVER early. The timetable stated a hierarchy of precedence: eastward trains (usually) had rights over westward, first class over second, second over third. If all goes perfectly, every train can run entirely by the timetable and a watch, needing only a clearance card from the dispatcher to leave its originating station. You can even run an "extra" train -- a train which has no timetable authority whatsoever, and not even need a train order to grant you authority, assuming the railroad is not too busy. All the engineer and conductor have to do is run against the authority of the scheduled trains, that is, inbetween their times, ducking out of the way into a siding when a scheduled train becomes due.

But since things never go perfectly, the train order is needed. The train order modifies the timetable: in effect, it temporarily suspends it for the trains to which it is issued. For instance, if your scheduled train No. 6 is running four hours late, you wouldn't want inferior trains to get out of the way for it four hours early. So you issue a train order stating No. 6 runs four hours late, which is MANDATORY on No. 4 and ADVISORY on inferior trains. That allows inferior trains to modify the timetable this one time and keep moving, and tells No 6 that it cannot leave any point one minute less than four hours behind its timetable schedule. This is necessary because No. 6 might make up some time.

Timetable and train orders worked very well back when passenger trains were prevalent. Since passenger trains do the same thing every day, and by nature are not supposed to ever be late, you could run a railroad very efficiently with this method. Most days, you didn't have to issue very many train orders. But once passenger trains disappeared, the advantage of the timetable method of operation evaporated. Now you wanted to run every train as an "extra," that is, with no fixed schedule at all. That meant the work load on train orders got out of hand. So the Track Warrant and DTC authority were invented. All they are, in effect, are simplified train orders, with all the timetable-modification stuff stripped out.

Two similar types of oral authority arose to replace the train order and timetable: DTC and TWC. The principal physical difference is that DTC has fixed, constant blocks designated by signs to the right-hand side of the main track at the entrance to each block. TWC has "floating" limits designated by the dispatcher, which can extend between mileposts, station signs, siding switches, or any combination thereof. Basically, any point that's in the timetable can be an endpoint of a TWC authority. You can see how convenient this is: TWC blocks can be one mile long or 100 miles long, just like that.

Typically DTC blocks extend from siding to siding, say, from east siding switch to east siding switch. Sometimes there will be additional blocks on the main track between siding switches.

DTC is obviously less flexible but less subject to misunderstanding as to where authority begins and ends. They present fewer chances of "missed repeats," where a crew either writes or hears the information from the dispatcher incorrectly, and when they repeat the authority the dispatcher doesn't catch the change.

Missed repeats are a common way to create a "lap" (two trains with overlapping authority), and have led to disastrous, fatal collisions, even in recent years. In dispatcher class, we all watched video of a headon collision of two BN trains at Ledger, Montana, a decade ago that killed the headend crewmen, which was caused by a missed repeat. I later read the NTSB report on the wreck. This was a line with one train a day each way. Normally the northward train arrived at its home terminal before the southward train left -- they met in the yard. This day the southward train was early. The afternoon trick dispatcher knew the southward train would leave early, so issued an authority to the northward train to a siding south of the yard. The crew on the northward train was so used to getting the track warrant all the way to the yard, that they filled it out that way and repeated it to the dispatcher that way. The dispatcher didn't catch the change! She OK'd it and that was that. Two hours later, she goes home, and the midnight trick dispatcher comes in, takes the transfer, and when the southward train is ready to leave, he looks at the track warrant book and sees the northward train is cut off at the sidng. So he goes ahead and issues a TWC authority to the southward to the siding. And off the southward train goes. Meanwhile, the northward train, holding what it thinks is a valid authority, runs past the meeting point and in a curve the two meet at a combined speed of 90 mph. The headend crews are killed, and eight locomotives and 40 or so cars destroyed in the collision and fire. The video showed the next day, using side-boom Cats to pick up the equipment and tracked front-end loaders gingerly scooping up spilled grain in the search for the dead crewmen.

They intended that video to scare us, and it did. All you have to be is inattentive for one second, and you kill someone.

I'll disagree with Mac on the "easier" part of DTC; they are actually just as time consuming to issue as a Track Warrant. If you issue more than 50 of these in eight hours, you are busy. I think the most I ever issued in one shift was 80. I never left the console even to go the restroom and never ate my lunch.

Authorities to occupy the main track also include yard limits, block register (usually seen on one-train-a-day branch lines), track permits, track-and-time (CTC), and work-and-time (track permit territory). Oh, and by the way, this all just applies on GCOR railroads --railroads that subscribe to the General Code of Operating Rules, which is most of those in the West. Eastern railroads use different rules which are similar but not identical to GCOR, and Canadian roads have yet a third set. I assume Mexico is different again.

The difference between an Absolute Signal and a Block Signal is, well, absolute. ANY signal with a number plate is a block signal. It does not convey authority: it only advises of track conditions ahead. Any signal without a number plate is an Absolute Signal. A block signal with a red aspect indicates stop, but then you can proceed at restricted speed. An absolute signal with a red indication may NOT be passed, unless verbally authorized by the train dispatcher. This is a fail-safe method: you can see that a block signal can "become" an absolute signal if the number plate falls off one day, but an absolute signal cannot become a block signal.

The only other common type of signal is a Distant, indicated with a "D" plate. These are used to provide advance information as one approaches signalled territory or an interlocking, and do not convey authority or information on the track condition beyond them. They only tell you about the indication of the next signal.

One common modification to a block signal is the addition of a "G" plate -- a grade signal. Signals so modified can be passed at restricted speed WITHOUT first stopping, and are used on heavy ascending grades to avoid difficulties in restarting a train. Some railroads, like the D&RGW, used to use a lunar head for the same purpose (you could see them farther away), but I think that practice is going away.

Your last question addresses how railroads keep track of locomotives and cars. Locomotives are tightly tracked, because you WANT to keep track of them. They're expensive and critical. Large railroads have a "power desk," which knows where every locomotive on the system is at: on a train, in a terminal, in a shop. Each dispatcher's console includes a trainsheet (it's displayed electronically now) which lists every train they are currently handling. Information for eacn train includes the locomotives. The train electronically "OS's" (reports its location) to the train sheet each time it passes a control point in CTC territory or gets a new TWC or DTC authority, and the screen updates itself. So you can look at the trainsheet and know exactly where a given locomotive is, or at least where it was four or five minutes ago, which is good enough because you know which direction it's going. That information is accessible to the power desk, if not directly updating into their display screens. So at a glance they get the whole picture.

Cars are less tightly tracked, because they don't need to be. All you need to know is that it's going in the right direction and on the right train, and when it left the last terminal. Each train has a trainlist that shows every car in that train -- hopefully the list is accurate and not missing some cars that are there, or showing cars there that actually aren't, and in order. Railroads used to employ clerks to check car numbers as trains entered and left yards, by standing next to the track and writing them down. Now they use electronic readers which check the transponder attached to each car, as well as fixed video cameras which allow you to look at the train and write down the car numbers from the office. Very frequently, you'll run a train list as a train passes a reader, because you want to verify its consist.

Beyond that, car tracking gets hard to explain. There's a broad variety of methods, ranging from the yellow legal pad on your desk to a computer database with automated inputs, with inputs ranging from the reader at the end of a yard to GPS transceivers that constantly update their location. It's a fair question to ask why railroads don't have the location of every car at their fingertips every second, and the answer is that they don't need that information -- why spend money on something unimportant? For example, if you have a 117-car unit-train set cycling between the same mine and the same power plant 150 times a year, all you need to know is that no cars have entered or left the set (the legal pad works fine for this) and a rough location of the train. It's usually irrelevant what order the cars happen to be in. In this instance, railroads often use the "tracer car" system: they track just one car in that train and assuming the other 116 are still coupled to it.

[PNWRMNM]

Daniel,

Suggest you back up a step.

Authority is required to occupy the main track. Your questions all revolve around authority.

The timetable is one way to grant authority. Train orders are another.

In CTC any absolute signal indication other than stop grants authority to the end of the system or the next absolute signal.

DTC and track warrants are used in non CTC territory to grant authority. While they seem quite a bit different at first they really are not in a logical sense. The difference is in how you designate track segments. In DTC it is by blocks. With warrants it is from station to station or between stations. I think DTC is a bit more intuitive and easier to use on a busy territory but to my knowledge only SP used it. Track warrants may be given by radio and copied by the crew, but there is more "stuff" on them than was used in DTC.

ABS signals do not convey authority. ABS signals are usually identified by a number plate. Controlled signals (in CTC do convey authority) to not have a number plate. In the past some railroads marked these as "A" (absolute) signals. You absolutely can not pass them at stop, where most block signals you can stop and then go on at restricted speed.

This is not a complete discussion of authority. The authority rules are very basic to safe operation and they are "just so" rules, meaning that the proceedures involved with them must be done "just so."

Mac

[Anonymous]

Dave - I am really impressed however.. what is a Neophyte and what do those signals look like

Also, Dave.. you should add your E-mail Etc to your profile, because if people have REALLY stupid questions they can e-mail you seeing as you have a very good bank of knowledge

[dehusman]

1. ABS is Automatic Block System. CTC is Centralized Traffic Control. The dispatcher can control the positions of some switches and can clear signals over those switches. The signals between the controlled points are basically ABS. DTC is Direct Traffic Control is not a signal system. It is a method of granting track authority verbally. It is a modern version of manual block control (more or less). DTC can be used on a territory with ABS.
2. Track warrants, DTC and Form D's allow main track authority to be granted verbally and are much easier to issue and understand.
3. see Q2.
4. Computers. Its not like they can wander off. AEI helps.

Dave H.

[Anonymous]

When it comes to my railfan knowledge, signaling and train dispatiching is my "Achilles heel." As such, I have several rather basic questions:

1.) What are ABS, CTC, and DTC, how do they differ from standard signal blocks, and how do they work?

2.) Why do railroads use Track Warrants, instead of just standard timetables and train orders like they used to, telling trains where to go and when?

3.) Why did railroads switch in the first place?

4.) How do railroads keep track of their massive fleets of cars and locomotives?

These may seem like very basic questions, but I am truly in the dark in this area of railroading. Any help you could give me would be most appreciated.

Thank you,
Daniel