Switch signals

Ok, I'm a big dummy as far as switch signals are concerned. (is that even the right name?) I thought green meant "straight" and red meant "switched"?

But, take this photo:

http://www.flickr.com/photos/thomas-mer ... 2/sizes/l/

In the foreground, we have four red signals. Now, how can the two on the left both be red? To me, the switch / turnout looks straight. Same with #3. Then, in the distance, we have red, amber, and green. Is the amber a different shade of red, or is it a 3rd signal? It doesn't look like there are any switches there, so what's the deal -- why are they needed?

Finally, I'm only seeing one signal for southbound trains (on the left). ??

Do the signals in the distance refer to the switches before (south of) the signals, whereas the signals in the foreground refer to the switches after (north of) the signals ?? (if that makes sense)

Ok, now let's move to exhibit 2:

http://www.flickr.com/photos/nicksuydam/3121150086/

In this one, we seem to have one green for the 3-way in the center. Or is that referring to something else? What are the color possibilities for a 3-way switch like that?

Think routing and not a specific result from a specific switch. These are not replacements for the little flags on the top of the switch machines.

In the first photo no train on any of the foreground rails should proceed (red=stop). The signal for the furthest right rail is out of frame but one can assume from the switch position that it too is red. Nothing is clear to proceed up to the second signals at the road.

Beyond the crossovers the three signals show stop on the left, approach in the center and clear on the right. A train isn't going to get to that clear signal until one of the foreground signals turns green (is cleared by the dispatcher for that movement). Perhaps the first switch on the right will change and the furthest right rail will get an out of frame green? Until the decision is made red is a good default. The center approach signal is basically a "stop ahead" ... if the train could get to that signal it would be allowed to proceed prepared to stop at the next signal, which is red. (And I say "if the train could get to that signal" because it suffers from the same problem as the green signal ... the dispatcher hasn't cleared the route.)

BTW: There may be a train approaching on the left rails ... a good reason for STOP to be shown to a train opposing it at every conflicting signal. If one of the foreground left signals were green the train would only be able to pull through blocking the interlocking until it stops at the next signal at the road. There is no reason to allow a clear on the foreground signals until the next signal clears. Any of the points could change position at any time until the route is cleared through. It is best to keep the trains out of the interlocking until the exit is clear.

Kangaroo_of_72 wrote:Ok, I'm a big dummy as far as switch signals are concerned. (is that even the right name?) I thought green meant "straight" and red meant "switched"?
AH no! Red means STOP!!! Period! Green or clear in this picture is a clear restricting allowing you to move on a straight route or diverging route. Because this would be considered interlocking Limits.

But, take this photo:

http://www.flickr.com/photos/thomas-mer ... 2/sizes/l/

In the foreground, we have four red signals. Now, how can the two on the left both be red? To me, the switch / turnout looks straight. Same with #3. Then, in the distance, we have red, amber, and green. Is the amber a different shade of red, or is it a 3rd signal? It doesn't look like there are any switches there, so what's the deal -- why are they needed? The four red signals at the bottom of the pick protect the switches directly above. The signals above can display I believe three aspects Red Stop/Yellow or Amber/ Green Clear. All these signals in your pictures are restricting signals.

Red means STOP!!!
Yellow or Amber means proceed restricted speed being prepared to stop.
Clear or Green means proceed restricted speed no exceed 10 MPH.

The signals in the upper part of the picture a control points above those switches.
Finally, I'm only seeing one signal for southbound trains (on the left). ??

Do the signals in the distance refer to the switches before (south of) the signals, whereas the signals in the foreground refer to the switches after (north of) the signals ?? (if that makes sense)

Ok, now let's move to exhibit 2:

http://www.flickr.com/photos/nicksuydam/3121150086/

In this one, we seem to have one green for the 3-way in the center. Or is that referring to something else? What are the color possibilities for a 3-way switch like that?

Your picture does not show the whole interlocking so your not seeing the complete line-up in the CPT or OCT. But yes the signals can be for different routes through that one particular switch. The number of signal aspects is the same all restricting signals Clear/Yellow/Red.

Ok, so in summary, these signals have nothing to do with the status of the switch, and instead are purely for controlling movements?

"These are not replacements for the little flags on the top of the switch machines"

So I'm not completely crazy ... there are still indicators for how the switch is positioned? And are they also red and green?

There are switch point indicators but none of your pictures have switch point indicator in them. There are switch point indicator machines. The switch point indicators I have dealt with use colors light display of green and yellow. No red for indicator lights.

Kangaroo_of_72 wrote:Ok, so in summary, these signals have nothing to do with the status of the switch, and instead are purely for controlling movements?

"These are not replacements for the little flags on the top of the switch machines"

So I'm not completely crazy ... there are still indicators for how the switch is positioned? And are they also red and green?

There are indicators ... as qboy said, the switches in your picture do not have them. That is pretty common with dispatcher controlled switches. I'd only expect to see an indicator on hand thrown switches (local control) although to be fair, Metra isn't the system I'm most familiar with.

Red/Green or Red/Yellow would be appropriate on a trailing point switch (if the points are not set in your favor you need a STOP signal).
Yellow/Green would be appropriate on a facing point switch (the train is going somewhere ... yellow diverting, green straight).
The flags I've seen reflect the main line condition ... red allows movement to or from a siding and green means the main is aligned ... although it is possible to have other options.

To toss in some additional info: These are interlocking signals and confer movement authority more than switch position. THE SWITCH has to be lined properly for movement over the switch so the two go hand in hand.

What I think is troubling to you is: how you can have a green with reds preventing a train to get to the green. This can come from two things. 1. dispatchers don't always line signals in the order you think. Lets say a two trains are due off two tracks that converge in the foreground around the same time but will use the same track beyond a certain point where one will have to follow the other. The DS will line up the known signal needed in advance and then leave a signal (like your foreground reds) unlined until he see which train will actually get to the converging switch first. With delays and equipment problems it is not always cut in stone even when operating by schedule. Since these are real short clocks you leave the signal that might have to be changed at the last minute red until it it time to use it.

The second reason the green might be lined is something called fleeting. The DS can set a frequently used signal to fleet, which means it will auto clear it self each time a train clears that section of track. In this case the switches in the station are in constant use but the mains beyond the roadcrossing are more set in the pattern the trains depart on and would be an likely candidate to leave in fleet.