ABS question

[Anonymous]

I have some questions about ABS signaling. The way I understand it, there are 2 reds then 2 yellows behind (and in front) of a train, like this: (if this works)


G G G G G R R Y Y G
########################### TRAIN ############################
G Y Y R R G G G G G

G=GREEN Y=YELLOW R=RED

Is this correct ? If not please explain.


And what about in double track territory where each track is only signaled for one direction? would the same apply,or would there be less blocks of red for a following train. like this:


G G G G R Y G G
########################## TRAIN ############################

<------- direction of travel

Can someone that knows tell me if this is correct or if not what is ? I am building an ABS signal system for my model railroad and would like to be as prototypical as I can.

I would appriciate any input on this.

[Anonymous]

Well it did't work, let me try again.


----G-------G--------G---------G---------G---------------R-----------R-----------Y-----------Y--------G--
############################ TRAIN ################################
---G--------Y---------Y---------R---------R--------------G------------G----------G-----------G---------G

AND

---G--------G---------G--------G---------G---------------R------------Y----------G-----------G---------G
############################ TRAIN #################################

<<<< DIRECTION

[pmsteamman]

Wisser,, cool illustrations... The second one is right (on CSX anyway). I used ABS on a 40mi section of track between Erie Mich and Romulus Mich. As for double track its the same, but if the dispatcher wants to run a train against the current of traffic they must issue a "block" to that train. In essence it tells a train he has permission to go from point A to point B and be ready to stop at the next signal (unless the signal allowed the train to proceed). Hope this helps.

[Anonymous]

The simple pattern is like this for single-track, four-aspect signaling, train moving right to left (westward). FY = flashing yellow

G-Train-R-Y-FY-G for the westward signals
G-FY-Y-R-Train-G for the eastward signals

If an APB-ABS system is used, all eastward signals will drop to red up to the next siding, which will have an absolute signal leaving each end -- APB (Absolute Permissive Block) is absolute for opposing trains, permissive for following trains.

In Rule 251 double track, the westward signal pattern above will obtain for a westward train on the westward track. Rule 251 double track is not reverse signaled, so there are NO eastward signals present. The only trains are following trains, unless a train order (old days) or track warrant (today) authorizes a train to run wrong main.

Some railroads wire the signals to present two reds behind a train, but this is fairly uncommon.

[Anonymous]

Thanks guys, I would still like to hear about the differences that are found on the different railroads. I understand different signaling methods are one of the things that gives railroads there individuality, and this is something I have great interest in.

I also have another question about capacity. The question is what has more capacity, double track ABS (rule251) or single track CTC. I have read articles about railroads converting from DT ABS to 1MT CTC (IC's mainline,SP over Donner both under Mr. Moyers and a section of GTW). I can understand reducing the amount of track will reduce maintainance costs but how can they do this without decreasing capacity. I've seen where they claim that is not the case, claiming that DT ABS is like two one-way-streets where faster trains get stuck behind slower trains because of the inability to run around the slower ones outside of terminals. I can understand that concept. What I can't understand is how "two one-way-streets" would not have significantly more capacity than "one lane with sidings".
perhaps some of you can enlighten me on what's really going on here.

And while I'm on a question asking binge, one more. In the above scenario where
DT ABS is converted to 1MT CTC, how much of the old signal system is used ? Any, or does it require a whole new installation ? or is it just a matter of adding controll points at key locations (and reverse signaling the remaining track)?

[?]

[Anonymous]

One more question. Mark, you base your answer on a four aspect ABS system. I lived on the SP coast line and never saw a flashing yellow, does this mean it was a 3 aspect system ? And if so then what would the following aspects be ?

[Anonymous]

3-aspect vs. 4-aspect: Yes, some ABS systems do not have the fourth aspect -- in fact, most pure ABS systems on single-track (that is, without a CTC overlay) are only three-aspect. The only difference is the lack of the flashing yellow. Signal spacing may have to be adjusted to provide adequate stopping distances. Single-track ABS systems without CTC are becoming uncommon these days -- the Santa Fe passenger line comes to mind.

Capacity: Directional double track has more capacity than single-track CTC in the ideal case. But it's not that simple, of course. Taking one track out of service for maintenance results in serious train delays. A railroad with a broad mix of train speeds, and a lot of traffic, requires either outside (Santa Fe practice) or center (UP practice) sidings for runarounds. You can use these as very rough rules of thumb as maximum reasonable capacity: up to 35 trains/day, single-track CTC; up to 60 trains/day, double-track ABS; up to 100 trains/day, two main track CTC. Go much over those numbers and it will be pretty difficult to make it run with fluidity, depending on geography, train types, etc.

Upgrading from ABS to CTC: unless the ABS was designed and installed with this in mind, it's pretty much going to be mostly thrown away. You'll save the hardware and the pole line, but it will all have to be rewired and probably the signals respaced, too. Labor is the big expense. Many late ABS systems were designed to be upgraded to CTC (notably the Moffat Road).

[Anonymous]

Great info. , Thanks for taking the time to answer my questions Mark.

[kenneo]

The SP, about 1990, started using an ABS signaling system within the CTC overlay that included flashing aspects of all colors. In simple terms, as a train approached an Absolute Red, you have G, FG, FY, Y, FR, R, train. The reason for this was that they did not need to respace signals. This system was more a simple rewire than anything else. With 6 aspect ABS, you can run a pig at Class 1 speeds because you have doubled the stopping distance.

The cutover was to be as money was available, and I think the Oregon Division was the first to start cutting over. I do not know how far they got into the project nor whether the UP continued it.

The start was from three aspect to four aspect, then they published rules for 6 aspect. I know that several CTC segments on the Brooklyn Sub had been cutover by 1993 to four aspect. I don't know about their getting any six aspect cutover.

[Anonymous]

From what I remember riding in the dome car of the "Texas Chief" between Temple and Cleburne TX and on the "Super Chief" between Albuquerque and Raton NM as well as trips by car in Texas along various Santa Fe mains before TCS, the old ABS had three red signals behind a train, then a yellow, and finally the greens. This was in the days of upper quadrant semophores. There were still quite a few of these well into the 1970's and a few still remain in New Mexico. The small Raton Pass Yahoo group has been discussing them lately. One of the guys posted a recent photo. the link is http://groups.yahoo.com/group/RatonPass/. The signals are not expected to last much longer. The Southern Pacific line from Houston to Dallas had lower quadrant semophores along most of that route when I rode the 1984 "World'sFair Daylight" behind 4449. There were also some 3 color block signals and several stretches of CTC. In the mid '80's the SP replaced the old semophores with 2 or 3 lamp signals or searchlight signals, but otherwise kept the ABS system along with the hand-thrown infrequent passing sidings around here. The line between Flatonia and New Orleans is mostly ABS with various CTC islands. The UP hasn't seen fit to do any major upgrading. I live next to a stretch of double track that seems to be a favored meeting place in Houston. No wonder the "Sunset Limited" is often 12 to 14 hours late. The SP Dallas line had relatively little traffic compared with the Santa Fe, so their signals were approach-lit. I never really saw enough traffic to fully understand the SP practices. The Santa Fe mainlines in Texas have always had enough traffic in my lifetime for any lay person to casually observe the signal patterns, especially in places where I could see several signals in a row.

[CShaveRR]

CN recently (a year or two ago) replaced signals on the old CC&P at the east end, but as far as I know it's still single-track ABS, and not CTC. It's definitely strange to see two signals on one mast, facing in opposite directions, and both showing green!

[Anonymous]

How many major Amtrak lines have ABS? I know the Coast Line does

DOGGY

[kenneo]

Stephanie

ALL of SP's and UP's signals are approach lit --- to save on power. When you have to run a power feed for 25 or more miles between public grid connections as the SP and UP needed to do in some places, the amount of electricity carried becomes an issue. This became espicially true when CTC was installed and you had to power the switches, too.

I have only seen one instance where UP or SP had continuous lighting and that is at interlockings andwhere UP had trackage rights over BN (then Oregon Trunk) rails.

Perhaps I should restate the UP as mentioned above stopped at Omaha. I can not vouch for the former CNW and Wabash (between KC and St.L), MP system and such.

[Anonymous]

Well, i don't want to add more confusion, but there is also another form of Signaling known as ATSF, Complete signaling protection, i'll illustrate.

----G-------G--------G---------G---------G---------------R-----------Y-----------G-----------G--------G--
############################ TRAIN ################################
---R--------R---------R---------R---------R--------------G------------G----------G-----------G---------G

<<<< DIRECTION

Remeber, only the Signals on the RIGHT apply to the train.

The ones on the left have had a "tumble-down" effect; Once a train Enters the main block, the Signlas "tumble down" on the opposing track so a Train can not enter any of the blocks (Starting at the Absolute signal)

The major Difference is, No Train would be allowed to enter the same Set of blocks (A set of blocks is from one absolute to anothe Absolute Signal)

Remmebr, This is Strictly CP Rail, We don't have flashing yellow, and we are ABS.

Now the actual name of this system might be ABS, or ABPS, or ATSF, i'll have to look it up, But the system i'm illustrating differs from ABS.

[wabash1]

kevin

the system you posted is what i run on, or at least how it works . on a trailing move ( following another train) when the train i am following gets 1 signal ahead the sigmal i am at will turn yellow. when he gets 2 signals ahead it turns green. the perpose in this is to let you know where the train is at ( the rear end anyways) but if the train is comming towards me all signals in my direction will drop to red back to the opposing positive signal . so nothing can enter that block.. you gave a perfect example of a abs block system that i could relate to. not to say the others might not be correct its not what i work with.

[kenneo]

Kevin and Wabash -------- this is also called Absolute-Permissive Block Signaling. See telizyn message above. Abv is A-PB or APB or APB/ABS.

Once you are passed a permissive "A" signal, and unless someone is asleep on an opposing train to run a red "A" block, you can not have any opposing movement against you until you get to the next "A" block.

[wabash1]

I dont know about the A block or the A-pb or the apb/abs or just bs. All i can tell you is that if i have 2 red signals in front of me i stop. after stopping and i cant get any response from the dispatcher and i have a track warrent . then i pull by the signal and wait 5 minutes then proceed. real simple stuff. i run restricted till i get the head end by the first green one i come to. all them other red ones dont mean nothing more than keep going slow. There is no letters on the signal mast . And not all are home signals are at sidings we have 5 signals that are no where near sidings or interlockings that are positives.( meaning if they are red you haft to stop) .

[Anonymous]

Thanks everyone.
This is all great info. Exactly what I was looking for. My computer was down for a couple weeks or I would have responded earlier.
Please keep the info coming.