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| Why not a BLUE aspect? 19/08/2010 at 13:17 #1643 | |
outofsection
149 posts |
Now in days of yore I can well underatand why blue was not chosen as an aspect as with a weak oil flame for illumination it was (almost) impossible to achieve a clear, vivid, bright blue light; but now with the advent of clear, distinctive, bright (3 watt and higher), vivid blue LEDs, why not use blue as an aspect? My first thought is to use it say on the London Underground where a double green is currently used (I believe) to show two clear sections ahead. A blue aspect could be used here as if there was any confusion between green & blue, well the next signal would still show green if as at present there was at least one section clear ahead. Just a thought! Log in to reply |
| Why not a BLUE aspect? 19/08/2010 at 13:17 #10820 | |
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outofsection
149 posts |
Now in days of yore I can well underatand why blue was not chosen as an aspect as with a weak oil flame for illumination it was (almost) impossible to achieve a clear, vivid, bright blue light; but now with the advent of clear, distinctive, bright (3 watt and higher), vivid blue LEDs, why not use blue as an aspect? My first thought is to use it say on the London Underground where a double green is currently used (I believe) to show two clear sections ahead. A blue aspect could be used here as if there was any confusion between green & blue, well the next signal would still show green if as at present there was at least one section clear ahead. Just a thought! Log in to reply |
| Why not a BLUE aspect? 19/08/2010 at 14:15 #10821 | |
flymo
135 posts |
Just FYI Over here in Hong Kong blue is used to indicate automatic train control is in use. I've see them mainly on the East Rail lines (the former KCR services) There is also the standard 4 aspect signalling as well. If the blue signal is on, none of the standard 4 aspects is illuminated.  The clock incidentally is not the time but the countdown to departure. Edit : Hopefully this size is viewable as the other try was a bit small. Log in to reply |
| Why not a BLUE aspect? 19/08/2010 at 15:16 #10824 | |
Danny252
1461 posts |
I don't know about others, but I find that Blue LEDs (such as outdoor christmas decorations) are very hard to focus my eyes on - they seem to just blend in at times. And, as was said above, it could be confused with green. Possibly a very light blue would avoid that - but then you could argue it blends in with the sky (on a similar note, do not normal, non-LED greens have a slight amount of blue to avoid blending in with vegetation?).
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| Why not a BLUE aspect? 19/08/2010 at 17:08 #10828 | |
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Jsun
212 posts |
In addition, the HK signal numbers are red meaning the train (if there is indeed one) has lost two minutes three seconds.
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| Why not a BLUE aspect? 20/08/2010 at 08:47 #10845 | |
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kbarber
1712 posts |
The Underground double-green is in fact equivalent to the big railway's semaphore home-over-distant combination showing "all clear" (also adopted by the GWR for their colour light installations). The main difference in indications on LU is that yellow is suppressed when the stop signal is at danger. The meaning is subtly different in that AIUI yellow on LU is normally used in a "repeater", which will only be provided when sighting of the main aspect is difficult. Where sighting is sufficient there is no caution signal and drivers are expected to stop within the sighting distance of a red signal. Technically that could apply where sighting is deficient but repeaters are provided so that trains don't have to slow where (e.g.) curvature reduces sighting distance (a way of keeping traffic moving). Combined stop/repeater signals are usually provided where there is a series of closely spaced signals with deficient sighting. (They can also be found approaching a station where sighting is OK as a way of encouraging approaching drivers to control their speed as they run towards an occupied platform; by timing the clearing of signals for the approaching train (and showing red-over-yellow at the first, sometimes also second and even third(?) signal) it's often possible to make time for the standing train to start away and the second then to run extremely closely behind it into the platform. One of these combined signals will carry 2 numbers; the white plate refers to the red/green signal and the yellow to the repeater and will be numbered "Rxxx" where xxx is the next signal it repeats, if it's part of a "closing up" system all the stop signals may have the same number with a subscript suffix letter to differentiate them and the repeater will be numbered something like "Rxxx b, c" (with b & c subscript). Very different to the sort of signals we're used to on the big railway. Log in to reply |
| Why not a BLUE aspect? 20/08/2010 at 19:19 #10865 | |
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clive
2738 posts |
The British Standard on signalling colours recommends against the use of blue because the eye tends to confuse it with white at a distance, much more easily than other colours. Keith's description of LU signals is mostly correct, but it only applies where 2-aspect signalling is in use. There are odd places (I think all now on the Metropolitan "country branch"  where 3- and 4-aspect signals are used. These are just like those on the big railway, except that fog repeaters show white when repeating an aspect other than red.
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| Why not a BLUE aspect? 21/08/2010 at 09:21 #10872 | |
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alan_s
152 posts |
I note blue lights are used on single lines with radio tokens - they show all the time, and flash when the driver has the token. Also I think in tunnels a blue light indicates an emergency exit, so I guess if there's a problem the idea is to aim to stop near one! Alan Log in to reply |
| Why not a BLUE aspect? 21/08/2010 at 21:16 #10885 | |
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UKTrainMan
1803 posts |
Just thought I'd share these three relevant screenshots I've just taken on the two excellent BVE4 routes of the Northern Line and part of the Jubilee Line (Green Park to Bermondsey). Green Signal, Red Repeater (on-approach to Tottenham Court Road, Northbound)  Green Signal, Green Repeater (on-approach to Tottenham Court Road, Northbound)  You'll have to ignore the signal plate numbers as they're generic across the route for each signal and not accurate. Interestingly enough, in the process of taking the above two screenshots a few green signals I saw in the distance did almost look like blue signals. alan_s said: Also I think in tunnels a blue light indicates an emergency exit, so I guess if there's a problem the idea is to aim to stop near one!Emergency exists are only provided on the part of the Jubilee Line Extension that is underground as they were in-built during the building process. This means that they are only between Green Park and North Greenwich (The line returns to the surface between there and Canning Town) Approaching an emergency exit (on the Jubilee Line) 
Any views and / or opinions expressed by myself are from me personally and do not represent those of any company I either work for or am a consultant for. Log in to reply |
| Why not a BLUE aspect? 21/08/2010 at 22:50 #10888 | |
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alan_s
152 posts |
Quote:Emergency exists are only provided on the part of the Jubilee Line Extension that is underground as they were in-built during the building process.Aren't they also in the channel tunnel rail link tunnels? Log in to reply |
| Why not a BLUE aspect? 21/08/2010 at 23:19 #10890 | |
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UKTrainMan
1803 posts |
alan_s said:Quote:Ahh, yes they are in the Channel Tunnel but I'm not sure how they are marked out. All I do know about them is that (if I've got this right) they are positioned a strategic places along the tunnel so that all trains using either tunnel have at least one exit next to the train at all times.Emergency exists are only provided on the part of the Jubilee Line Extension that is underground as they were in-built during the building process.Aren't they also in the channel tunnel rail link tunnels? That said, I cannot recall seeing any blue lights in the tunnel when I watched the Eurostar "Drivers Eye View" DVD I've got lying around somewhere nor do I remember seeing any when I recently went through it. Thinking about it, I seem to now be recalling that the emergency exits are marked out using reflective boards so that the train driver can see them and [hopefully] a member of the train crew will be able to find the nearest one by using a torch in the case of an evacuation Any views and / or opinions expressed by myself are from me personally and do not represent those of any company I either work for or am a consultant for. Log in to reply |
| Why not a BLUE aspect? 22/08/2010 at 13:55 #10901 | |
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taffy
28 posts |
Blue lights are also used in the Severn Tunnel to indicate to the driver where the bottom of the tunnel is. i.e a set on the downward incline to indicate approaching bottom, and another set on the up incline to indicate the approach to the upward gradient. Martin Log in to reply |
| Why not a BLUE aspect? 24/08/2010 at 07:32 #10942 | |
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ralphjwchadkirk
275 posts |
Can I just point out here, that blue lenses are (or were) very common on the national network. With paraffin lamp-lit signals, the lens is blue so as to produce a green aspect ;). Anyway, back to the topic. Why would we need a blue aspect? Do we need more aspects? Not really. Log in to reply |
| Why not a BLUE aspect? 24/08/2010 at 13:30 #10955 | |
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outofsection
149 posts |
Precisely because as someone said earlier: at present the LU uses the two greens in a similar way to the old semaphore "home over distant" i.e. if they're both off, both the current AND the next mandatory signal (i.e. red) are clear: but instead of showing two greens you show one blue instead. As was the case with semaphore distant signals the blue aspect would be an ADVISORY aspect NOT as is the case with red, a MANDATORY one. So if a driver mistook the blue for say a white or green, at the end of the day it would not be the end of the world BECAUSE the worst case scenario is that the next signal the driver would see up the track would be a green signal anyway upon entering the next section up the track! My point being that why use 2 lights instead of one? More electricty used, more equipment to install, to maintain etc... added to which, the driver, knowing that there are at least TWO completely clear signals in front of him, he can continue to accelerate up to or maintain maximum speed without any risk of being slowed shortly by a (double?) yellow in the next section following the two greens. More energy efficient all round... nes pa? AND without any form of safety compromise! Log in to reply |
| Why not a BLUE aspect? 24/08/2010 at 15:08 #10958 | |
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clive
2738 posts |
But a driver seeing one green should be accelerating up to full speed anyway. After all, why delay when the double yellow ahead might be going to change? Green means that it is safe to proceed at full line speed; there will be sufficient warning of any need to brake. So what does a fifth aspect gain?
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| Why not a BLUE aspect? 24/08/2010 at 21:19 #10988 | |
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alan_s
152 posts |
Actually there is a fifth aspect, on the ECML between Peterborough and Stoke summit. As I understand it, a flashing green means the next signal is green; and if the HSE had ever allowed it, this aspect means you can increase speed to 140mph! Stead greens and you must slow again, expecting double yellow etc ahead. Alan Log in to reply |
| Why not a BLUE aspect? 25/08/2010 at 00:10 #10994 | |
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UKTrainMan
1803 posts |
alan_s said:Actually there is a fifth aspect, on the ECML between Peterborough and Stoke summit. As I understand it, a flashing green means the next signal is green; and if the HSE had ever allowed it, this aspect means you can increase speed to 140mph! Stead greens and you must slow again, expecting double yellow etc ahead.A very good point and something that I had forgotten about! Indeed you can still see this in use as I have done personally at Tallington LC looking Southbound / London-bound and seeing a Class 158 on the Up Fast approaching a flashing green just beyond the crossing, although these days the flashing greens are simply treated exactly the same as steady greens. In-fact mentioning this raises a question as to why the flashing green isn't simulated on the Peterborough simulation - flashing yellows are simulated so why isn't flashing green simulated? Any views and / or opinions expressed by myself are from me personally and do not represent those of any company I either work for or am a consultant for. Log in to reply |
| Why not a BLUE aspect? 25/08/2010 at 08:22 #10997 | |
GeoffM
6282 posts 
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There appears to be some confusion here - some people are talking about LU signalling; others NR signalling. The two have different rules and aspects. FWIW, aside from experimental and/or obsolete aspects and banner repeaters, there are seven colour light aspects on the Big Railway: - Red - Shunt - Yellow - Flashing yellow - Double yellow - Flashing double yellow - Green Splitting distants show a subset of those seven so could be considered the same. SimSig Boss Log in to reply |
| Why not a BLUE aspect? 25/08/2010 at 11:38 #11002 | |
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clive
2738 posts |
Flashing green on SimSig: Geoff refused to put it in when I asked. However, there's some new facilities present since then, so I might experiment when I next refresh Peterborough. Geoff: you've forgotten PoSA (flashing shunt), which is an 8th (it's not experimental any more, it's mainstream). Log in to reply |
| Why not a BLUE aspect? 25/08/2010 at 12:14 #11003 | |
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GeoffM
6282 posts
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clive said:Flashing green on SimSig: Geoff refused to put it in when I asked. However, there's some new facilities present since then, so I might experiment when I next refresh Peterborough.A little strong - I didn't think it was worth it as it was experimental. clive said: Geoff: you've forgotten PoSA (flashing shunt), which is an 8th (it's not experimental any more, it's mainstream).Good point, forgotten that one. SimSig Boss Log in to reply |
| Why not a BLUE aspect? 25/08/2010 at 13:56 #11009 | |
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Danny252
1461 posts |
PoSA? Something of Shunt Something?
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| Why not a BLUE aspect? 25/08/2010 at 14:07 #11011 | |
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GeoffM
6282 posts
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Danny252 said:PoSA? Something of Shunt Something?Proceed on Sight Authority In brief: Shows a flashing pair of white lights in a shunt signal instead of the steady white lights. From our very own Clive: http://newsgroups.derkeiler.com/Archive/Uk/uk.railway/2006-03/msg00268.html In detail: http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Railway%20Group%20Standards/GERT8071%20Iss%201.pdf SimSig Boss Log in to reply |
| Why not a BLUE aspect? 02/09/2010 at 01:40 #11241 | |
kaiwhara
584 posts |
I cannot speak for NR but in New Zealand we use a blue aspect in several circumstances - both to indicate the position of point. The most common situation to find a Blue aspect is on a Facing or Trailing Points Indicator in Track Warrant Control areas (Track warrant being a form relayed from the Train Controller to the Locomotive Engineer ((or track gang / Hi-Rail Vehicle or Line Closure - a track warrant can be used for a number of purposes) which is the LE's authority to occupy a specified section of non-interlocked line. Most of these sections have one or many more crossing loops which, while not exactly fitted with signals per ce, are fitted with points indicators which will either have one or two heads stacked vertically - a two headed indicator being the facing indicator. This will show Blue over Red if set for the main route, Red over Blue if set for the diverging route, or All Red - which as in interlocked territory means stop. However an indication other than All Red is not authority to proceed - that authority is provided with the Warrant which will also stipulate crossing instructions as nessesary, and it does not confirm that the line is not occupied, obstructed, broken rail etc. On most occasions a train approaching a crossing station fitted with Points indicators will find the points set for the main and a blue over red by default. If the LE holds a warrant for the Loop at this station he has to get out, cancel the light, wait for the 90 second time delay and then reset for the Loop. If he then recieves the Red over Blue aspect, then he will enter the loop, and in most occasions will need to cancel his warrant and either get a new one if the line ahead is clear, or wait for the opposing train at which point both trains will need new warrants. One problem that has been experienced here is that the blue aspect is not very easy to see in a number of lighting conditions - which is fine in our situation as we use the aspect in a relatively low speed situation, but I doubt it would be acceptable in line speed situations. As it is, a number of the Facing indicators have been replaced with a single head which will show yellow for the main (authority to proceed is still via the warrant), All Red, or Red with an illuminated white 'L' below and staggered to the right of the main signal head - which indicates the loop. Sorry guys, I am in the business of making people wait! Log in to reply |
| Why not a BLUE aspect? 02/09/2010 at 13:33 #11248 | |
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Danny252
1461 posts |
kaiwhara said:If the LE holds a warrant for the Loop at this station he has to get out, cancel the light, wait for the 90 second time delay and then reset for the Loop.That seems an awfully long wait just to change a set of points - I'm sure there's some legitimate reason for the delay though. Could you enlighten us? Log in to reply |
| Why not a BLUE aspect? 02/09/2010 at 15:18 #11251 | |
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GeoffM
6282 posts
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Danny252 said:That seems an awfully long wait just to change a set of points - I'm sure there's some legitimate reason for the delay though. Could you enlighten us?I've heard of this arrangement elsewhere where there are no track circuits. The timeout in that case is to allow a train that might be approaching time to stop. SimSig Boss Log in to reply |