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Y2Julio

CPL signals in the Subway?

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what about the AK's, red circle K's, the yellow no key by or the red no key by? what happened to the train order signals. its not overly hard but if you dont understand what the signal does its going to get you in trouble.

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For anyone who doesn't know what a CPL (color position light) looks like, here's an example of a dwarf signal (small size)

 

dwarf12lightfront.jpg

 

The circular structure contains block information: A red horizontal -- means stop (no blocks clear), a yellow diagonal / means approach (1 block clear), and a green | means clear (2 or more blocks clear)

 

The 6 white lights around the main head modify the signal's meaning by conveying speed information:

 

cplprimer2.jpg

 

cplprimer3.jpg

 

 

This kind of signal is not really the most practical for the subway because of the space it takes up, the short blocks of the system, the amount of heads needed for each signal, and the need to convey more accurate route info. The reason the SIR uses it is because it used to be owned by the B&O, and is a more appropriate place for this kind of signal. More info about this kind of signal can be found here

 

 

With regard to cab signalling, I have to agree that it would cause more problems than it would solve. There is no reason to switch over from the current system, and as INDman said, the implementation of newer technology always seems to have something go wrong. This is not even considering the cost of upgrading the rolling stock and many other components

These aren't the CPLs SIR uses. The ones we use are a lot smaller and simpler. CPLs would be used at interlockings, you wouldn't need any other signals in between interlockings with pulse code CSS.

Also, what do you mean "more accurate" route info?

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With the CPLs, the speed shown on the signal implies what the route is (ie medium/limited clear or med approach med usually means a diverging route, and the slower speed aspects could mean either straight or diverge), but doesn't always tell you exactly where you're going. With the current subway signals, you can immediately see where you're going when the signal isn't red (bottom green for straight, bottom yellow for diverge, 3 yellows for yard or 2nd diverge) as well as the speed. This is what I mean by more accurate info.

 

And Julio do you have a pic of a SIR CPL?

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With the CPLs, the speed shown on the signal implies what the route is (ie medium/limited clear or med approach med usually means a diverging route, and the slower speed aspects could mean either straight or diverge), but doesn't always tell you exactly where you're going. With the current subway signals, you can immediately see where you're going when the signal isn't red (bottom green for straight, bottom yellow for diverge, 3 yellows for yard or 2nd diverge) as well as the speed. This is what I mean by more accurate info.

 

And Julio do you have a pic of a SIR CPL?

 

there are a few places where a bottom green is a diverge.

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but doesn't always tell you exactly where you're going.

 

Huh? It always tells you where you're going. White marker light lit on top; you're going straight, White marker light lit on the bottom; you're diverging. The only time you won't get any white marker lit is when you're diverging multiple times consecutive, I.E when going through the St. George interlocking going through multiple switches. Here's an image of a typical CPL on the RoW.

6017261668_0ab72a8c6e_b.jpg

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That would not fit in a subway tunnel. The signal system that is in place is the best for the subway.

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Julio-

 

When I said it doesn't always tell you exactly where you're going, I meant for 3 or more track rrs in general, not the SIR, because when there are more than 2 possible diverge moves at the same speed, all you'll see is a medium or slow speed aspect and not which track you'll be diverging to. I understand that SIR only has 2 possibilities with some exceptions, the full speed straight ahead or medium speed diverge, so it makes sense that in this case you know where you're going based on the marker alone.

 

I also find it strange that dwarves are used as high signals, both on posts and signal bridges. Why not just use the high signals instead?

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