Page 2 of 2
| Weird signal between WEA and EAL 23/10/2013 at 16:29 #50294 | |
Stephen Fulcher
2080 posts |
I didn't think JWI was the right term, but could find no reference to what they were. Thanks. Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 17:45 #50295 | |
|
GW43125
495 posts |
" said:" said:The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...Also if I recall correctly the reason for putting in a splitting distant there was because there is already a flashing aspect sequence to allow trains into Plat 5 at Reading Station. You cannot have 2 consecutive flashing sequences so a splitting distant was the only option other than approach released from red which would be very restrictive. Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 19:37 #50298 | |
lazzer
634 posts |
" said:The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...So what you're saying is, the signal that would ordinarily be single yellow with junction indicator can actually be a flashing yellow for a second diverging route? Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 20:36 #50299 | |
|
JamesN
1608 posts |
" said:" said:SN300 on the Up Airport at Airport Jn is Flashing Double Yellow and JI1 when crossing RL - ML at Southall West, although admittedly there isn't a flashing sequence leading to it.The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...So what you're saying is, the signal that would ordinarily be single yellow with junction indicator can actually be a flashing yellow for a second diverging route? Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 10:15 #50305 | |
|
clive
2789 posts |
" said:The rules don't allow consecutive or overlapping flashing sequences. They also don't allow a signal to show both a flashing aspect and a junction indicator. So the shortest sequence you can legally see is FYY, FY, Y+JI, FYY, FY, Y+JI on four aspect, or FY, Y+JI, FY, Y+JI on three aspect. If we've got signals 1, 3, 5, 7, and 9 in sequence, then it's legal for 5 and 9 to both be junctions with flashing aspects so long as this is the straight route at 5. That is, you either have a JI at 5 with 1=FYY, 3=FY, or you have a JI at 9 with 5=FYY, 7=FY, but you can't have FYY+JI at 5. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 10:21 #50306 | |
|
clive
2789 posts |
" said:Nowadays, they tend to install Junction Warning Indicators (http://www.davros.org/rail/signalling/articles/jwisystem.html), although I have never seen a yellow one.JWIs were a proposal that never got implemented. What you will have seen are Preliminary Route Indicators. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 10:25 #50307 | |
|
clive
2789 posts |
" said:" said:Hmm. This is explicitly forbidden by GK/RT0045 section 5.5.1.1:" said:SN300 on the Up Airport at Airport Jn is Flashing Double Yellow and JI1 when crossing RL - ML at Southall West, although admittedly there isn't a flashing sequence leading to it.The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...So what you're saying is, the signal that would ordinarily be single yellow with junction indicator can actually be a flashing yellow for a second diverging route? "The signalling system shall be configured so that the following aspect combinations are not used to display movement authorities: [...] f) (Junction method 2) A junction signal that is displaying a flashing aspect and a route indication (a junction signal may display a flashing aspect when the straight ahead route is set if no route indication is displayed)." Note that, under 5.2.3.4, if the signal that would show flashing double yellow is a junction signal as well, it shall show steady YY instead. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 10:46 #50309 | |
|
Stephen Fulcher
2080 posts |
" said:" said:I knew there was something with arrows from the time I was there - they were installed about a month or two before I left, but couldn't remember the technical name, only the operation. The only arrow-type thing I could find in the ten minutes I had to spare was your article, hence I got the name wrong!Nowadays, they tend to install Junction Warning Indicators (http://www.davros.org/rail/signalling/articles/jwisystem.html), although I have never seen a yellow one.JWIs were a proposal that never got implemented. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 13:24 #50310 | |
|
JamesN
1608 posts |
" said:" said:Attatched excerpt of Scheme Plan for Current phase of remodelling at Airport Jn" said:Hmm. This is explicitly forbidden by GK/RT0045 section 5.5.1.1:" said:SN300 on the Up Airport at Airport Jn is Flashing Double Yellow and JI1 when crossing RL - ML at Southall West, although admittedly there isn't a flashing sequence leading to it.The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...So what you're saying is, the signal that would ordinarily be single yellow with junction indicator can actually be a flashing yellow for a second diverging route?  Aspect Sequence is SN300 FYY + JI1 - SN284 FY - SN276 Y + JI4 Post has attachments. Log in to view them. Last edited: 24/10/2013 at 13:27 by JamesN Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 14:35 #50311 | |
|
Stephen Fulcher
2080 posts |
The scheme plan doesn't really help us with that as there are single flashing yellows shown on both SN284 and SN280 (I think thats the right numbers looking at the plan, but can't blow it up big enough to be sure). The control tables are what we really need. As the area is now SSI (on the ground at least) there is not a lot the detailed diagrams would show other than the flashing aspects being an output from a Signal TFM. As Clive says it was banned to have flashing aspects AND junction indicators. The relevant standard GK/RT0032 does not specifically mention that it is banned, but it does not mention that it is allowed either. There would certainly be a large risk of confusion if this were to be allowed, and the approaches to Paddington are not known for their simplicity. I wonder if FireFly can shed any light on this issue - if anyone has seen this sort of thing then I would bet he has! Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 15:18 #50312 | |
|
JamesN
1608 posts |
" said:The scheme plan doesn't really help us with that as there are single flashing yellows shown on both SN284 and SN280 (I think thats the right numbers looking at the plan, but can't blow it up big enough to be sure).No, SN280 is a flashing double yellow for crossing ML-RL at Southall East, not flashing single yellow. The forum shrunk the picture somewhat more than I expected, this link should work to the full resolution http://classmob.co.uk/files/AJSSP.PNG It definitely flashes double yellow with JI1, I've seen it! Last edited: 24/10/2013 at 15:20 by JamesN Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 15:31 #50313 | |
|
Stephen Fulcher
2080 posts |
Thats better, can see the image a lot clearer now. SN280 is actually a flashing double yellow, so two consecutive double yellows would not be allowed. I wonder when the standards were relaxed. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 15:35 #50314 | |
|
JamesN
1608 posts |
" said:Thats better, can see the image a lot clearer now. SN280 is actually a flashing double yellow, so two consecutive double yellows would not be allowed.After May 1997 
Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 18:02 #50316 | |
|
AndyG
1842 posts |
" said:" said:I was interested to see at Surbiton Station on the DS Platform 3 a signal showing fYY together with a P4 RI. Speaking to the driver, the aspect showing was for the DS>DF crossover at Hampton Ct Jn just over a mile away, despite there also being a DS>FD crossover a short distance in advance. I didn't realise until them that a fYY and feather could be displayed together." said:Hmm. This is explicitly forbidden by GK/RT0045 section 5.5.1.1:" said:SN300 on the Up Airport at Airport Jn is Flashing Double Yellow and JI1 when crossing RL - ML at Southall West, although admittedly there isn't a flashing sequence leading to it.The minimum allowed is: G,DFY,SFY,DFY&JI,SFY, etc...So what you're saying is, the signal that would ordinarily be single yellow with junction indicator can actually be a flashing yellow for a second diverging route? I can only help one person a day. Today's not your day. Tomorrow doesn't look too good either. Last edited: 24/10/2013 at 18:02 by AndyG Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 18:04 #50317 | |
|
Ron_J
331 posts |
As with any Railway Group Standard, you can obtain a derogation against any of the requirements of GK/RT0045 so long as you can demonstrate you have evaluated the risks and taken appropriate steps to make them ALARP. We've certainly installed some interesting things recently in Scotland which do not comply with the Standard but which are legitimate nonetheless.
Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 22:28 #50327 | |
|
Firefly
521 posts |
As has already been mentioned the standards do not require retrospective action. So far as I can tell the clause that Clive is referring to only came into being with the introduction of GK/RT 0045 in April 2010. Prior to that GK/RT 0032 contained no such clause. Obviously with scheme plan shown above you cannot get two consecutive flashing yellows. SN300 will flash with double yellows and position 1 junction indicator for a route set towards SN284. It will not flash if a route is set towards SN280. As clive mentions this does contradict the current standard:- Quote: (Junction method 2) A junction signal that is displaying a flashing aspect and a route indication (a junction signal may display a flashing aspect when the straight ahead route is set if no route indication is displayed) I'm fairly certain this arrangement was commissioned prior April 2010. Hope this helps. Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 23:24 #50328 | |
|
jetblast787
62 posts |
" said:" said:Out of interest, where can I find diagrams like that?The scheme plan doesn't really help us with that as there are single flashing yellows shown on both SN284 and SN280 (I think thats the right numbers looking at the plan, but can't blow it up big enough to be sure).No, SN280 is a flashing double yellow for crossing ML-RL at Southall East, not flashing single yellow. The forum shrunk the picture somewhat more than I expected, this link should work to the full resolution Log in to reply |
| Weird signal between WEA and EAL 24/10/2013 at 23:24 #50329 | |
|
clive
2789 posts |
" said:I accept that there are examples in the field: presumably they have derogations. Quote: Sorry, on four aspect you can legally have FYY, FY, Y+JI -> YY+JI, FY, Y+JY, using the special rule I mentioned previously. Log in to reply |
| Weird signal between WEA and EAL 25/10/2013 at 08:22 #50334 | |
|
kbarber
1742 posts |
" said:" said:I accept that there are examples in the field: presumably they have derogations. It may help to remember that, so far as the sequence seen by the driver is concerned, FY is equivalent to YY in that it reads to Y - the flashing is additional information, namely that the road is set for a turnout. Or at least it was so when flashers were first introduced (at that time the junction signal remained Y+JI until the train had passed over the AWS inductor, then stepped up if conditions allowed). Although modern practice is to step up the junction signal much earlier, I suspect that old thinking is preserved implicitly in the modern sequence. So in Clive's amended sequence, there's YY over the turnout followed by the equivalent of [YY with turnout warning]; as the driver should be expecting Y at that signal there's no harm in going from steady Y to FY. That's how I understand the logic anyway. And it just goes to show that, even in modern signalling, historic practice and thinking can be surprisingly influential. Log in to reply |
| Weird signal between WEA and EAL 25/10/2013 at 08:47 #50335 | |
|
Stephen Fulcher
2080 posts |
" said:" said:Unless you work for the Railway, not through legitimate means, although even working for the railway they are not always that easy to obtain." said:Out of interest, where can I find diagrams like that?The scheme plan doesn't really help us with that as there are single flashing yellows shown on both SN284 and SN280 (I think thats the right numbers looking at the plan, but can't blow it up big enough to be sure).No, SN280 is a flashing double yellow for crossing ML-RL at Southall East, not flashing single yellow. The forum shrunk the picture somewhat more than I expected, this link should work to the full resolution Log in to reply |
