Signal sequence

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wilric

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When overland trains are following another train further up the track can they receive two double yellows in a row?
 
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Cherry_Picker

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Yes, but only because the signals are clearing to double yellow ahead of you because of the passage of trains in front. The sequence is still G YY Y R. If you match the speed of the train in front identically, there is no reason why you cant receive 100 double yellow aspects in a row.
 

Railsigns

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Yes, but only because the signals are clearing to double yellow ahead of you because of the passage of trains in front. The sequence is still G YY Y R.
Where signals are closely spaced, you can have consecutive double yellows in the sequence: G YY YY Y R.
 

GB

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Yes, but only because the signals are clearing to double yellow ahead of you because of the passage of trains in front. The sequence is still G YY Y R. If you match the speed of the train in front identically, there is no reason why you cant receive 100 double yellow aspects in a row.

I think the OP means the train is approaching a double yellow with the next signal in the sequence also a double yellow..

Train1 > YY YY Y R Train2

...and the answer is yes you can.
 

ainsworth74

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I would have thought the same would apply to Single Yellows as well.

Surely it applies to every signal aspect (apart from Red I suppose seeing as that has to clear to another aspect before you can pass it)?
 

Cherry_Picker

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Where signals are closely spaced, you can have consecutive double yellows in the sequence: G YY YY Y R.

You learn something new every day! I guess this is one of those theory vs practice things though, because I have never answered g YY YY Y R on a rules exam (and I have had a few!) but always been passed competent.
 

The Planner

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It is done as a speed control as the braking distance has been deemed insufficient at some point, normally years after installation.
 

wessex

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I never knew that either, I dont think that happens on our route, if it does I wasnt told :)
 

Bald Rick

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On the GEML there are a few examples of 3 x consecutive YY on the Electric lines west of Gidea Park to deal with the short sections there. Much of this is being regularised for Crossrail.
 

westcoaster

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I never knew that either, I dont think that happens on our route, if it does I wasnt told :)

The only odd thing we have is the double blocking of purley ( g yy y r r ) on the fasts. Hence if your on the up quarry and get stopped at stoats nest, and he let's one across in front of you, you have to wait till it clears purley before you get a proceed aspect.
 

O L Leigh

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Yes, it's common on the "E" lines on the GEML east of Stratford where the signal spacing is very tight. If it all comes to a halt it's not uncommon to see what looks suspiciously like a traffic jam with trains nose to tail. We also have a signal like this on the 'Up' at Broxbourne where the normal sequence will be G YY YY Y R if the platform starter is at danger, again because of signal spacing and sighting issues. However, no this is not the normal signalling sequence for 4 aspect signalling as described in the Rule Book. "Double-blocking" is another topic altogether.

There's not much point adding to what has already been said in response to the original question as posed. I think it's already been covered.

O L Leigh
 
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