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| Question on 4-aspect signalling 27/03/2012 at 08:17 #30948 | |
sorabain
72 posts |
Hi there, I am relatively unfamiliar with signalling rules, conventions and constraints compared to the rest of you, so apologies if this question can be answered by some trivial reference to an appropriate document available on the web. I was sitting waiting for a train on Alexandra Palace's platforms 1 (towards Kings X) watching the non-stopping trains go by on adjacent platform 2. There's a 4-aspect signal at the end of platform 2, and looking down the lines I could see the next signal glistening in the heat-haze in the distance. A number of services rushed past me, and I thought I would take the opportunity to see what (if any) visible delays there might be in the changes of aspects of the signal at the end of the platform and the one down the line. I'll call the signal at the end of the platform signal 1 and the one further down the line signal 2 After a service passed by I was expecting to see the sequence signal 1 green & signal 2 green signal 1 red as train moves past signal 1 signal 2 red & signal 1 single yellow as train moves past signal 2 signal 2 single yellow, signal 1 double-yellow (i was hoping to see what delay there might be between these) signal 2 double yellow, signal 1 green signal 2 green however, between two non-stopping services it went signal 1 green & signal 2 green signal 1 red as train moved past signal 1 signal 2 red & signal 1 single yellow as train moved past signal 2 signal 2 single yellow, signal 1 no change (still single yellow) signal 2 double yellow, signal 1 double-yellow for fraction of a second, then straight to green signal 2 green I was wondering what the reason for signal 1 only passing through double-yellow momentarily was, it was effectively going straight from single yellow to green. thanks in advance for any responses, Sorabain Log in to reply |
| Re: Question on 4-aspect signalling 27/03/2012 at 09:58 #30949 | |
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Jan
906 posts 
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You're the not the first one to notice this, but no definitive conclusion was then reached whether this was some kind of fault, or done intentionally in order to provide additional braking distance. Edit: You can see it in this video as well. Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick. Last edited: 27/03/2012 at 10:01 by Jan Log in to reply |
| Re: Question on 4-aspect signalling 27/03/2012 at 11:22 #30950 | |
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Phil-jmw
675 posts |
Could be the top yellow lamp out in Signal 1. Phil. Log in to reply |
| Re: Question on 4-aspect signalling 27/03/2012 at 15:17 #30951 | |
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Danny252
1461 posts |
A lamp being out for 7 months seems like quite a stretch of the imagination. The signal spacing from 452 (platform) to 442 seems no different from 442 to 418, or 472 to 452. I wonder what aspects 472 shows? Log in to reply |
| Re: Question on 4-aspect signalling 27/03/2012 at 19:42 #30957 | |
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Underwood
748 posts |
I doubt the top lamp is out though, since the OP does mention that it shows double yellow, albeit very quickly.
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| Re: Question on 4-aspect signalling 27/03/2012 at 21:48 #30968 | |
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Stephen Fulcher
2078 posts |
It is definitely NOT the lamp out as it would not go momentarily double yellow if it was. My suggestion would be that this was intentional when the signalling system in this area was designed. There could be many reasons for this, some of which are touched upon in the other thread which is linked above. FireFly is more of an expert on this sort of thing! Log in to reply |
| Re: Question on 4-aspect signalling 28/03/2012 at 14:46 #30980 | |
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Phil-jmw
675 posts |
" said:A lamp being out for 7 months seems like quite a stretch of the imagination.I didn't notice anyone saying it had been like that for 7 months Danny. You must have divine insight. What I also didn't pick up on was it momentarily showed 2 x yellow as it stepped up from yellow to green. In that case, no, the top yellow lamp isn't out. Phil. Log in to reply |
| Re: Question on 4-aspect signalling 28/03/2012 at 14:49 #30981 | |
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Stephen Fulcher
2078 posts |
I think Danny was referring to the same discussion in the old thread, which was about that timeframe ago.
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| Re: Question on 4-aspect signalling 28/03/2012 at 15:23 #30983 | |
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Firefly
521 posts |
Quote:FireFly is more of an expert on this sort of thing!I can't add anything else on top of what I said in the previous thread. Sorry Log in to reply |
| Re: Question on 4-aspect signalling 29/03/2012 at 12:18 #31053 | |
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sorabain
72 posts |
Thanks for the responses all
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