dumb signaling question

[pat390]

this is a stupid question, but if a signal is showing yellow over red does that mean a train could be through in as long as an hour or as short as 5 minutes, I know when it is green there will be a train usually in less than a minute, but on the NS line (if that makes a difference on signaling) until the last minute or so it is yellow over red or red over red, could someone please explain what is going on?!?!?!
thanks,
pat

[chad thomas]

The signal gives no indication of how long it will be before the next train. That's not what they are for. An exception would be an approach lit signal. They light up only when there is a train in the block, and sometimes by then you can already see / hear the train.(by block I mean signal block)

The aspect of the signal tells a train what conditions are ahead like if the next block or the one after that is occupied or if you are going to be taking a diverging route.

[jchnhtfd]

without knowing the exact district... but yellow over red is usually a restricted approach and red over red stop. Neither one will tell you when the next train is coming along, unless they are approach lighted in which case they won't show any light at all until a train enters the block before them... usually. Sounds like, off the top of my head, that that is the idle indication of the signals, and they won't clear (turn green) unless a train is approaching them and the way beyond is cleared.

[Mookie]

Perfect!

I can see one set of tracks that has a red over red most of the time. When the top one goes yellow, I know something will be coming to use those tracks to go into the yard.

When the engine passes the signal, it goes to solid red over red!

I keep meaning to ask the question and keep forgetting.

Thanx Pat!

(and Jaime and Chad for the answers!)

[chad thomas]

I have noticed that there are some lines that the signals come on when a dispatcher lines a movement through the signal. It's a good indication that a train is coming, but there is no telling how long it will take. As an example when I railfan the UP line east of the Feather River, around Doyle and I see the signal light up green it means a train has been lined through. The only thing is from where? When traffic is heavy the train being lined through is probably not more than a siding or two away. But when traffic is light that train being lined through could be as far away as Winnemucca (over 100miles away). You have no way of knowing.

[mudchicken]

The whole world is not CTC folks.

[CSSHEGEWISCH]

Yellow over red often indicates approach. There is a signal visible from the Oak Lawn station on Metra Southwest that usually shows this aspect. It also serves as a distant signal for Chicago Ridge crossing so when it changes to green over red, the route through the crossing has been cleared for a train, usually an outbound Metra train but occasionally a transfer run to the IHB.

[Mookie]

Hi big Muddy! I think we are CTC up to a point. But where and where not, I am still working on that. I know there are plenty of signs that say "End CTC" around....at least I think that is what they say....[%-)]

[oltmannd]

It sound most likely that this is the distant signal for an interlocking, since it has two heads. It will sit at yellow over red all day long unless a route is selected through the interlocking (by operator or dispatcher) and the signal cleared. Then it will display an aspect that indicates the position of the switches in the interlocking and the condition of the track ahead. If it's a straight route and ther are no trains ahead, then it will show green over red. If it is a divergent route with no train ahead, then the aspect could be yellow over green.

Either of these aspects indicate that a route has been cleared for an approaching train. When that train will arrive is not related to the aspect. It could be minutes or hours away.

A two headed signal could also be an intermediate block signal that's part of a 4 aspect block signal system, but this is not very common. If it's on track that's signalled in one direction, the signal will sit at clear (or dark if approach lit) most of the time and will only show a more restrictive aspect when there is a train ahead. If it's signalled in both directions, it will show clear for the current direction of travel and red if against it.

Where is this particular signal?

[chad thomas]

QUOTE: Originally posted by mudchicken

The whole world is not CTC folks.

Then I better call my ds for some block authority...It's been a while science I've seen the (search)light.

[pat390]

thansk guys, and the signal is in valparaiso indiana, ex nickle plate

[MP173]

Pat:

I know what signal you are referring to. It is an "approach" signal meaning be able to stop at the next signal...kinda like a yellow traffic light when you start driving.

The line is CTC with sidings in both directions about 2miles distant...Spriggsboro to the west and Nickel to the east.

Here is how to determine at that signal if something is coming:
You need to look at both signals (facing east and west).
If both are y/r you cannot expect a train within a few minutes...the dispatcher has not lined up or coded in a route for a train.

If you see r/r then a train may be coming or may have already passed. Look at the other signal and see what the indication is. If it is g/r (clear) then a train is coming in that direction. If it is r/r...wait and see, something may be coming. if it is y/y then something is coming as that is an advance approach signal, meaning be prepared to stop at the 2nd signal (this is usually for westbounds, giving them advance notice the route has not been cleared by the CN dispatcher to cross at Spriggsboro.

Basically, the dispatcher will line up a route a few minutes ahead of the train (up to 20 minutes). If you see both are y/r, then nothing is lined up and ride your bike to CN to see what is happening there.

Good luck and remember the best times to see trains on that line are outlined on my report. There are definate times the Nickle Plate runs trains...they are a scheduled railroad.

ed

[pat390]

thanks a lot ed: I plan to go and see some action later on tonight, at least now I know what is going on.

[MP173]

Listen to your scanner, as they call out the signals.

Things probably wont pickup for awhile until the evening parade begins. Then you should see 306/307, 262, 215, and 236, but the problem is it will be dark by 715.

323 and 280 have already headed east.

Be safe,

ed

[edblysard]

GCOR rule 9.1.3, yellow over red aspect.
Proceed prepared to stop short of next signal.


NORAC rule 285..procced prepared to stop at the next signal.
Trains exceeding medium speed must begin reduction to medium speed as soon as the engine passes the approach signal.

In ABS territory, indicates a train is in one of the proceeding blocks.
In CTC, gives no indication of the trains location, dispatcher may be setting up a move for trains miles away.

Ed

[Mookie]

OK - that makes sense! Now I am going to say - we are GCOR and CTC. My final answer.

I like it because it means don't leave, there is another train coming in and it is usually within the next 10 - 15 min. It is right at the edge of the yard, going into the yard. So this all makes sense!

Thanx Ed

M

[Anonymous]

Worthwhile link. Be sure to look at the pretty pictures under "Signal aspects and indications"

http://www.lundsten.dk/us_signaling/

[Mookie]

That helps. You can see where they can proceed, subject to stop with another train coming at them. (siding)

[MP173]

Ed:

Thanks for the "official" ruling. I probably should spend a little time learning the aspects.

On the signal in question, a y/r almost always means there is nothing lined up as that seems to be the default reading for the signal. Now that is not always the case as once in a while a train will follow on another's block, OR the train will have a stop indication at the next CTC siding.

Signals are a really interesting aspect (pun intended) of railroading. In many cases, it is our only clue as to what has happened or what will happen.

ed

[Anonymous]

Pat 390 there is no such thing as a dumb or absurd question. A question is a means of acquiring knowledge and that is what you were trying to do. You received sove very good answers to your question from some members who probable are in the operating arena of a railroad. By asking your question you have increased your knowledge base. This is the main purpose of these forums - fou us to obtain knowledge and to share knowledge. Keep up the good questions. Perhaps you may ask one that I will be able to answer some day with my very limited knowledge.

***

[kenneo]

Just to complete the above picture.

There are three basic types of signals -- CTC, SA, and ABS.

CTC signals are Absolute Signals and are controlled directly by the dispatcher.

SA signals (Semi-Automatic) almost always are distant signals controlled, in part, by an Absolute Signal. These signals control an approach to something.

ABS is Automatic Block Signal. Aspect controlled by track occupancy.

With the exception of interlockings, crossings and drawbridges in dark territory, you must have an underlying ABS system to have CTC. The actual CTC signals are at control points only. The approach (distant) signals are then SA signals, and the balance are ABS.

There is only one exception to the above paragraph. Track Occupancy. If the detection circuit BYOND the signal shows occupancy, then the signal into that block will show STOP no matter what any dispatcher may do to his board. How the train crew reacts to that signal depends on whether it is an "A", "SA" or "ABS" signal.

Approach lighting has been mention in above posts and only one other thing may need to be said. If the block byond the signal shows occupancy, the signal will show red whether on not any train is approaching. For example, a train approaches a green signal and the engine passes the signal and occupies the following block. That turns the signal from green to red and that signal will stay red until the last car of that train exits the block at its far end. Then the light will turn off unless another train is approaching it. Depending on the railroad, more than one signal in advance of an approaching train may be lit.

In approach lighting, if the train is coming toward you, you will see a dark signal until the block is actually occupied, and then it will go from dark to red. Then comes the train. If you have continuous lighting, then you will see a green signal, then yellow, then red, then the train.

[Anonymous]

Some yards work on a Red over Red all the time until a train is comming.

CN works like that, i'm not a big fan of it. The signals at the beginning of The Sources yard, or at the beginning of the CN CTC is always red/red and red/red/red until a train is approaching, or has been given a clearance.

Ed is right, in the CTC territory- Yellow over red means in my terms "clear to stop" Block is clear, next one is a stop. A train may be nowhere near you,there might not have even been a train all day- signals drop like flies in CTC territory.

In ABS teritory, where train movements govern the aspects, in is a pretty good indication that a train is either two blocks ahead, or is approaching that signal at a slower speed depending on it's length and what it is comprised of.

[kenneo]

QUOTE: Originally posted by pat390

this is a stupid question, but if a signal is showing yellow over red does that mean a train could be through in as long as an hour or as short as 5 minutes, I know when it is green there will be a train usually in less than a minute, but on the NS line (if that makes a difference on signaling) until the last minute or so it is yellow over red or red over red, could someone please explain what is going on?!?!?!
thanks,
pat

This is NOT a stupid question. Failure to comply with what those lights tell you kills people. You need to understand what the indications are telling you and also why.

[DaveBr]

One other question.Do the gates have their own power in case of power failure,like here in Los Angeles. Dave br

[edblysard]

Depends on what the local DOT determined needed to go there, but most do have battery back up for 48 hours on average...after they fail, the gates are designed to drop as the default setting, no power, they close by gravity.
Some use solar panels charging battery packs...

Ed

[Anonymous]

CP tests them once a month