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Opposing signals have same aspect (yellow)

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#1
For a long time now, I have wondered why on single track, the west facing signal and the east facing signal have the same yellow aspect at the same time. They are on the same signal stand.
This is on the Alexandria Sub in Ontario.

Mike
 

W8RMH

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#2
Yellow - Used to warn the engineer of an impending stop or speed reduction for an occupied "block" ahead. Also used for low-speed movements.

A train crew seeing a signal with a yellow aspect will understand they are nearing an approach signal, which conveys an indication that might mean "proceed prepared to stop before your train passes the next signal; trains exceeding 35 mph must immediately reduce to that speed."
 

franks_ham

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#3
To properly answer your question Mike. There are multiple scenarios of HOW this can happen, one is listed below, but this is the hopefully "simplified" version of what is really happening out there. What you are seeing is a result of an age old technology called "tumble down". Those signals will remain at "Approach" or yellow, until an East or West man "demand" their attention.

For simplicity we will call your signal SIGNAL 2 (TWO).

Train 1 is headed Eastbound and will see a Green signal at Signal 1, when Train 1 enters the circuit for SIGNAL 2 (TWO), the signal will do 1 of 2 things, STAY YELLOW or "UPGRADE" to a Clear (Green). Signal 3 will then upgrade from a RED to a YELLOW if the "logic" allows it.

Meanwhile....

Train 2 is headed Westbound and will see a Green at Signal 1a, a Yellow at Signal 2a, and a Red at Signal 3a. Whatever HAPPENS, THIS train better not see that Signal 2 (TWO) that you see.

As all this is happening, Signal 2 (TWO) will go from Yellow to Red as Train 1 enters the circuit for Signal 2 (TWO). Signal 3a (mentioned below) will go from Yellow to Red as well, since that is probably the end of Double Track. Once Train 1 passes Signal 2 (TWO), Signal 2a will drop from Yellow to Red IF Train 2 has not already passed it.

Regards,

-Frank C.
 

RRR

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#4
In simplified terms, Amber is usually displayed as a default when the dispatcher doesn't have anything lined up for the signals, IE; nothing coming or going in either direction.
 
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#5
Thank you for the replies.

I think this must be the situation that you describe.

These two signals always display the yellow aspect when the track circuits are idle as you indicate.
When a route is selected on this subdivision, then they display a green in the correct direction.
This just seemed unusual as the other signals on this subdivision stay at red when there is no traffic.

I find signals and how they work very interesting.

Thanks again.

Mike
 
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Location
Henderson, KY
#6
Thank you for the replies.

I think this must be the situation that you describe.

These two signals always display the yellow aspect when the track circuits are idle as you indicate.
When a route is selected on this subdivision, then they display a green in the correct direction.
This just seemed unusual as the other signals on this subdivision stay at red when there is no traffic.

I find signals and how they work very interesting.

Thanks again.

Mike
Its highly likely that you are in an area with ABS or intermediate signal, dispatcher does not control(automatic block signals). Track is broken down into blocks or segments, and varies in distances. The normally red signals you mention are probably an absolute signal that is controlled by dispatcher.

As the yellow is an Approach signal on CSX. Having a yellow on both sides means that there are no trains on either side or occupying either block on any side of the signal. Could keep going but hard to describe without drawing something lol
 

Mojaveflyer

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#7
Yellow Block Signals On Opposing Signals

I too have seen that on the BNSF Brush Sub east of Denver. It is CTC and recently upgraded so that PTC is active on this line. From what I've seen, the intermediates will display yellow in both directions if nothing is lined through for the absolute signals at the ends of sidings.
 

PJH

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#8
Crowe has it most correct. Many railroads have enabled what is known is "approach lit lighting" to save on electricity and bulb costs (even though the bulbs and LED's last a LONG time). Not to be confused with "approach" signal (typically a solid yellow light).

It all comes down to how the signal system is designed and vintage.

Each block is always "showing an indication" based on the track occupancy, however if you can "see" it is another matter. Even if the signal is dark, the electronics are still set to what it should be showing.

Confused yet? :)

Depending on your area and railroad terminonlogy used by the railroad being watched, in CTC the track that is dispatcher controlled - uses controlled signals at "controlled points" (control points). These are signals that do not have milepost/signal numbers on them. They are known as control points, home signals, absolute blocks, "A" blocks, "CP's" or whatever the railroad called them.

The dispatcher mearly "requests" a signal, but does not control what light the crew see's. The signal system does that.

Now in between these controlled signals, the lights are still ABS lights. They are not controlled by the dispatcher but by the signal system based on track occupancy. If there are 5 ABS signals between a CP, the ones in the middle will most likely display green in both directions as there are no trains in the blocks in either directions. As soon as a train starts to come in to that block from another direction, it should drop from Clear (typically green), advanced approach or approach medium (or something like that on the east coast) (typically a flashing yellow) to approach (solid yellow) then to red (restricted proceed, stop and proceed or similar).

That is fairly true to relay based signals. The newer Safetran and other modern solid state systems may never do this and always be red in both directions until a movement is detected and then sets the signals accordingly. Areas that have old signal systems that have since been converted from the days of semaphores (remember those may not have been lit but the relays would properly show the blades in the correct way) carried over to the searchlights, and then to the color lights.

If you live in an area that still uses searchlights, and are approach lit, try shining a flashlight into the signal lens at night. Most likely you will see a reflection of what color the block system is set for based on the light reflecting through the roundel - as it typically operates the same way as the semaphore did internally.

**Each railroad operates on their own signal rules. Even though many railroad operates with similar rule books, you will find that no two signal rules may be the same - even on the same railroad. This is especially true on CSX and NS that have legacy signal systems from merged railroads. I think CSX has up to four different signal rules based on what railroad the line was built by.
 
Joined
Sep 27, 2007
Messages
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Location
Henderson, KY
#9
Crowe has it most correct. Many railroads have enabled what is known is "approach lit lighting" to save on electricity and bulb costs (even though the bulbs and LED's last a LONG time). Not to be confused with "approach" signal (typically a solid yellow light).

It all comes down to how the signal system is designed and vintage.

Each block is always "showing an indication" based on the track occupancy, however if you can "see" it is another matter. Even if the signal is dark, the electronics are still set to what it should be showing.

Confused yet? :)

Depending on your area and railroad terminonlogy used by the railroad being watched, in CTC the track that is dispatcher controlled - uses controlled signals at "controlled points" (control points). These are signals that do not have milepost/signal numbers on them. They are known as control points, home signals, absolute blocks, "A" blocks, "CP's" or whatever the railroad called them.

The dispatcher mearly "requests" a signal, but does not control what light the crew see's. The signal system does that.

Now in between these controlled signals, the lights are still ABS lights. They are not controlled by the dispatcher but by the signal system based on track occupancy. If there are 5 ABS signals between a CP, the ones in the middle will most likely display green in both directions as there are no trains in the blocks in either directions. As soon as a train starts to come in to that block from another direction, it should drop from Clear (typically green), advanced approach or approach medium (or something like that on the east coast) (typically a flashing yellow) to approach (solid yellow) then to red (restricted proceed, stop and proceed or similar).

That is fairly true to relay based signals. The newer Safetran and other modern solid state systems may never do this and always be red in both directions until a movement is detected and then sets the signals accordingly. Areas that have old signal systems that have since been converted from the days of semaphores (remember those may not have been lit but the relays would properly show the blades in the correct way) carried over to the searchlights, and then to the color lights.

If you live in an area that still uses searchlights, and are approach lit, try shining a flashlight into the signal lens at night. Most likely you will see a reflection of what color the block system is set for based on the light reflecting through the roundel - as it typically operates the same way as the semaphore did internally.

**Each railroad operates on their own signal rules. Even though many railroad operates with similar rule books, you will find that no two signal rules may be the same - even on the same railroad. This is especially true on CSX and NS that have legacy signal systems from merged railroads. I think CSX has up to four different signal rules based on what railroad the line was built by.
After 17 years on the RR I get something right every now and then haha... Thought I'd throw this in, one way to tell the difference between an absolute and intermediate is if there is a name or number plate on the signal mast. If it has one it is an intermediate, nothing then its an absolute.
 
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