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| Using emergency replacement buttons to protect crossings 06/03/2013 at 10:25 #42098 | |
kbarber
1712 posts |
" said:" said:I agree. The ESR is purely there to replace the signal to red if there is an emergency (obstruction etc) ahead of it, requiring the stopping of trains.Some older relay areas allowed signals to show a single yellow if the next signal was black. I'm given to understand this was a standard provision in the early - mid 1960s schemes on the WCML; indeed I have an idea it was theoretically possible to have a yellow in the platform starter at Euston reading all the way to the stops at Manchester Piccadilly with all intervening signals black. Log in to reply |
| Using emergency replacement buttons to protect crossings 06/03/2013 at 11:32 #42099 | |
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mfcooper
707 posts |
" said:" said:At Victoria (Central & Eastern): If the signal is blank vice red, the previous signal shows red. If the signal is blank vice proceed, the previous signal shows its most restrictive proceed aspect." said:I agree. The ESR is purely there to replace the signal to red if there is an emergency (obstruction etc) ahead of it, requiring the stopping of trains.Some older relay areas allowed signals to show a single yellow if the next signal was black. And none of our signals will show an alternative aspect if the desired one is not available. We have to change controlled signals (and use replacements) if we want to use an alternative, working, aspect. Last edited: 06/03/2013 at 11:35 by mfcooper Log in to reply |
| Using emergency replacement buttons to protect crossings 07/03/2013 at 17:57 #42126 | |
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Firefly
521 posts |
Quote:In terms of the electrical "gubbins", what's different between a reliable and an unreliable ERS?It's decided by the SIL of the signalling system (SIL = Safety Integrity Level) SIL 0 = Non safety SIL 1 & 2 = Safety Related SIL 3 & 4 = Safety Critical Relay interlockings and SSI are considered safety critical (SIL 3 or 4). Many older ERS's were controlled via non-vital FDM (Frequency Divisional Multiplex) which is not safety critical therefore cannot be relied upon. Even if you send back a confirmation to the box as Geoff suggested you still cannot rely upon it unless the confirmation circuitry is safety critical. This has caused us many headaches over the last few years because it's Network Rail's policy that all alterations should bring signalling up to modern standards (R Button), however it's incredibly difficult to achieve a guaranteed replacement over TDM and FDM systems so 9 times out of 10 a derogation is sought and the signals remain as E buttons. Interestingly R does not always mean guaranteed either. I believe all of the replacement buttons in Feltham PSB have an R on them, however only a couple can be relied upon. When Feltham was built the standard was to use R, it was sometime later that somebody decided that E would be Emergency Replacement (Not relied upon) and R would be Replacement (Guaranteed). Log in to reply |
| Using emergency replacement buttons to protect crossings 08/03/2013 at 22:13 #42189 | |
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Hooverman
306 posts |
All of the emergency replacement buttons at Three Bridges ASC are marked with a R but only the four on panel 5 that protect level crossings and all of them on panel 7 are proven.
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