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Using emergency replacement buttons to protect crossings

You are here: Home > Forum > Miscellaneous > The real thing (signalling) > Using emergency replacement buttons to protect crossings

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Using emergency replacement buttons to protect crossings 06/03/2013 at 10:25 #42098
kbarber
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1742 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.
On another note: I thought that if an aspect failed, the signal would change to caution or a stop aspect. In any event, if the any aspect was out, the rules and regulations fully cover that event.
Some older relay areas allowed signals to show a single yellow if the next signal was black.
<snip>

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.
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Using emergency replacement buttons to protect crossings 06/03/2013 at 11:32 #42099
mfcooper
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707 posts 		" said:
" 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.
On another note: I thought that if an aspect failed, the signal would change to caution or a stop aspect. In any event, if the any aspect was out, the rules and regulations fully cover that event.
Some older relay areas allowed signals to show a single yellow if the next signal was black.
<snip>

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.
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.

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
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Using emergency replacement buttons to protect crossings 07/03/2013 at 17:57 #42126
Firefly
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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).
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Using emergency replacement buttons to protect crossings 08/03/2013 at 22:13 #42189
Hooverman
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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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