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Does the reversible signalling on the NLL get used much?

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martin2345uk

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Currently learning this route (from a freight perspective), just wondered what the main use of the sections of bi-directional running on the North London Line are, as it doesn't run right through on either line...?
 
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Bald Rick

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I was there when it was commissioned, nearly a decade ago, and have never known it used since. No doubt it *has* been used, but sparingly, for getting round a stranded train or a very specific infrastructure issue.

The bi di at Hackney Wick - “the cupboard” used to get regular use until the overground services increased in frequency. It was also a regular place for signaller errors, with ‘Mexican Stand Offs’ occurring every couple of months. I guess it is still used occasionally now.
 

Ianno87

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I was there when it was commissioned, nearly a decade ago, and have never known it used since. No doubt it *has* been used, but sparingly, for getting round a stranded train or a very specific infrastructure issue.

The bi di at Hackney Wick - “the cupboard” used to get regular use until the overground services increased in frequency. It was also a regular place for signaller errors, with ‘Mexican Stand Offs’ occurring every couple of months. I guess it is still used occasionally now.

I've seen the Graham Road curve in occasional use to turn back a late-running Stratford-bound service early to get it back on time again.
 

87015

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Occasionally when Highbury is open but Canonbury blocked do bi-di from Camden Road, including only stopping at Caledonian Road eastbound with westbounds via the back road. Now lots of discussion follows any proposal to beg for having Canonbury available to shunt due to general confusion caused by the above!

Various blocks see bits of it used to get to point of obstruction, ie Hackney Wick from the west when Stratford is shut.
 

The Planner

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Bi-di is a wonderful thing and is always questioned why we don't have more, however, we are very risk adverse to using single line working (SLW) and adjacent line open working (ALO) so it tends to sit there being bored showing red aspects for months at a time. If you need to cut costs in a re-signaling, any plans to have it are usually the first to go.
 

Bald Rick

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Bi-di is a wonderful thing and is always questioned why we don't have more, however, we are very risk adverse to using single line working (SLW) and adjacent line open working (ALO) so it tends to sit there being bored showing red aspects for months at a time. If you need to cut costs in a re-signaling, any plans to have it are usually the first to go.

Indeed - the NLL bi di was expensive, and extended the commissioning block too.
 

martin2345uk

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Was it basically just cost vs benefit that stopped them doing full bi-di that us freight guys could use too?
 

Y Ddraig Coch

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Bi-di is a wonderful thing and is always questioned why we don't have more, however, we are very risk adverse to using single line working (SLW) and adjacent line open working (ALO) so it tends to sit there being bored showing red aspects for months at a time. If you need to cut costs in a re-signaling, any plans to have it are usually the first to go.

I absolutely agree with you here, they seem very quick to just get a RRB out rather than use the infrastructure that they have spent millions installing.
 

Bald Rick

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Was it basically just cost vs benefit that stopped them doing full bi-di that us freight guys could use too?

It always is cost vs benefit.

The issue is that there’s not much work you can do with just one line closed. And even then, you need relatively low traffic levels to be able to make use of it. And the NLL doesn’t have that.
 

30907

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Occasionally when Highbury is open but Canonbury blocked do bi-di from Camden Road, including only stopping at Caledonian Road eastbound with westbounds via the back road. Now lots of discussion follows any proposal to beg for having Canonbury available to shunt due to general confusion caused by the above!

Various blocks see bits of it used to get to point of obstruction, ie Hackney Wick from the west when Stratford is shut.
I used it there some years ago to get past a block (failed unit IIRC when the 378s were new).
 

Class 170101

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I'm afraid people expect reversible signalling to be used and not sitting around waiting for incidents to be resolved ahead of them.

As for Single Line Working my limited experience suggests the extra time required is sadly almost as long as a Rail Replacement Bus between adjacent stations. The only reason it was was used was to keep a few passengers on trains and a few electric freights operating that had no alternative routes. Frankly the sooner the key routes are Bi-Di signalled the better I am afraid.
 

norbitonflyer

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Seen bidi used at Wimbledon when a broken down freight train was sitting on the "up St Helier" line, so "up" Thameslink trains ran "wrong line" from Wimbledon West Junction (the point where the St H line converges with the SW Main Line) to the normal beginning of the single track section through the station.

(For those unfamiliar with the area, Thameslink services through Wimbledon use platform 9 in both directions - it is a major constraint preventing increasing the service frequency - because Platform 10 was taken over by Tramlink in 1999. West of the station there is a ladder junction connecting the Thameslink tracks to the parallel SW Main Line, which allows freight (and the occasional steam special to/from Victoria) to transfer between the SWML and the former Central Division route towards Streatham Junction.
 

The Planner

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I'm afraid people expect reversible signalling to be used and not sitting around waiting for incidents to be resolved ahead of them.

As for Single Line Working my limited experience suggests the extra time required is sadly almost as long as a Rail Replacement Bus between adjacent stations. The only reason it was was used was to keep a few passengers on trains and a few electric freights operating that had no alternative routes. Frankly the sooner the key routes are Bi-Di signalled the better I am afraid.
As I said earlier though, we won't utilise it even if we have it. It is too expensive on new installations and unless ETCS solves it economically then its unlikely.
 
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