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Multiple Track AHB Crossings

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Multiple Track AHB Crossings

Unread postby Richard Lemon » Sun Sep 14, 2014 7:55 am

A question has been raised about the maximum number of tracks that can be protected by standard AHBs.

I have been sent a photograph of a six line crossing in Australia.

Anyone know the rules?

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Re: Multiple Track AHB Crossings

Unread postby ex Probationer » Sun Sep 14, 2014 8:28 am

The ORR guidance indicates a maximum of two tracks for an AHB (page 14).

The Guidance is here:

http://www.orr.gov.uk/__data/assets/pdf_file/0016/2158/level_crossings_guidance.pdf
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Re: Multiple Track AHB Crossings

Unread postby Richard Lemon » Sun Sep 14, 2014 8:45 am

Many thanks - this confirms what I suspected to be the case!

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Re: Multiple Track AHB Crossings

Unread postby StevieG » Sun Sep 14, 2014 9:33 am

For what it may be worth Richard, I have a strong memory from years ago that it was at one time AHBs were permitted to cross a maximum of three lines, and the permitted speed on lines crossed was a maximum of 100mph, but can't point you to a definite source of those details.
[Was Floriston (a few miles north of Carlisle), a 3-line example? - Doubtless someone else hereon will know].
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Re: Multiple Track AHB Crossings

Unread postby Richard Lemon » Sun Sep 14, 2014 10:19 am

I note that the ORR document refers to a maximum of two running lines at an AHB. Is this wording significant?

So, can there be sidings as well???? I'd hope not!

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Re: Multiple Track AHB Crossings

Unread postby Mad Mac » Sun Sep 14, 2014 3:28 pm

I think Floriston's layout was such that you could only have two trains running over it at once. Some of the "predictor" units in the US can handle eight!
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Re: Multiple Track AHB Crossings

Unread postby mossend4 » Mon Sep 15, 2014 3:38 pm

The mention of Floriston reminded me of a conversation in Rules & Signalling Section, Buchanan House following the Hixon accident of 1968 which was expected to have some effect on it. Memory fails, as I thought there were 4 tracks at Floriston, but a photo taken prior to the box closure confirms it was only 3. Auchengray was mentioned too, as it didn't have a protecting stop signal within the (new?) mandatory required distance from the crossing.

I felt it would be helpful if the pre-Hixon 1966 requirements for AHBs were linked to give 'before and after' comparisons. According to this document, prior to Hixon there was no limit on line speed nor number of lines passing over an AHB crossing.

http://www.railwaysarchive.co.uk/docume ... on1968.pdf
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Re: Multiple Track AHB Crossings

Unread postby John Hinson » Mon Sep 15, 2014 6:16 pm

I think there were two tracks when Floriston box closed, but under Kingmoor panel there was a crossing cabin with three tracks. The pictures at http://www.geog.port.ac.uk/webmap/thela ... k15316.htm suggest that the crossing is a Full Lifting Barrier crossing although those views don't show whether it is controlled from the cabin (which lasted to 1967) or CCTV. I susp[ect the latter as the blurred train looks a tad modern for 1967!

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Re: Multiple Track AHB Crossings

Unread postby mossend4 » Mon Sep 15, 2014 8:06 pm

Thanks John, from what you tell me and the absence of signals, the box in the 1st photo taken in the 1960s may be a gate box.

North of Floriston box, looking south.
http://www.railbrit.co.uk/imageenlarge/ ... p?id=29350

Floriston crossing, looking north.
http://www.railbrit.co.uk/imageenlarge/ ... p?id=22234

South of Floriston box, looking south.
http://www.railbrit.co.uk/imageenlarge/ ... p?id=21291

I saw from the 3rd photo that the Down goods loop / exit from Carlisle yard terminated south of Floriston box. Before seeing this, I had thought it continued over the crossing.

This Extract from Network Rail 2004 Business Plan shows that the crossing was an AHB until the early 2000’s:-

"Section 2: Route Plans …….page 251

Our continuous programme of structural maintenance and renewal work continues.

Signalling
We are planning to upgrade the level crossings at Cove and Floriston from AHB to MCB3, as part of the route upgrade to cater for the increased line speed."

http://www.networkrail.co.uk/BusinessPl ... Routes.pdf
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Re: Multiple Track AHB Crossings

Unread postby Bob Davies » Mon Sep 15, 2014 8:31 pm

John Hinson wrote:I think there were two tracks when Floriston box closed, but under Kingmoor panel there was a crossing cabin with three tracks. The pictures at http://www.geog.port.ac.uk/webmap/thela ... k15316.htm suggest that the crossing is a Full Lifting Barrier crossing although those views don't show whether it is controlled from the cabin (which lasted to 1967) or CCTV.

When I was working at Floriston in 1973 it was a three-track AHB supervised from Gretna Junction until Carlisle PSB took over. The conversion to full barriers took place much later (sorry I do not have a date).

Mad Mac wrote:I think Floriston's layout was such that you could only have two trains running over it at once.

I do not recall any such controls in Floriston Relay Room and the protecting signals on the Up Fast and Up Goods were both plated as autos but some of the controls were in location cases so there may have been some interlocking between the two Up lines.

I think it would have been rare to have three trains passing over the crossing simultaneously (although not impossible unless the signalling prohibited it) as it would have to have involved one of the infrequent Longtown MOD trips. However, I did work out that it would have been theoretically possible for four trains to pass over the crossing in a single closing sequence - Down Fast, Up Goods, Up Fast, Down Fast (from Down Goods), which I think must be something of a UK record. Whether this ever actually happened of course is another matter!
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Re: Multiple Track AHB Crossings

Unread postby John Hinson » Tue Sep 16, 2014 6:48 am

Bob Davies wrote:When I was working at Floriston in 1973 it was a three-track AHB supervised from Gretna Junction until Carlisle PSB took over. The conversion to full barriers took place much later (sorry I do not have a date).

Of course, sillly me - I had forgotten about the panel in Gretna which I think coincided time-wise with the opening of Kingmoor. So the temporary "gate hut" must have been replaced by AHBs in 1967.

Best wishes,

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Re: Multiple TRack AHB Crossings

Unread postby AndyB » Tue Sep 16, 2014 6:51 am

I have memories of the limit in more recent times being two running lines, and two sidings (although it sounds from all the above that it may now be only one siding). I would hope that the sidings would require the crossing to be transferred to local control!
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Re: Multiple Track AHB Crossings

Unread postby John Hinson » Tue Sep 16, 2014 6:59 am

mossend4 wrote:Thanks John, from what you tell me and the absence of signals, the box in the 1st photo taken in the 1960s may be a gate box.

North of Floriston box, looking south.
http://www.railbrit.co.uk/imageenlarge/ ... p?id=29350


Good point that there are no signals visible! And a re-check with my records shows that the box was not replaced by a hut but simply downgraded to a non-block post 18/2/63. Apologies for the red herring . . .

So that picture should be between 1963 and 1967 I think.

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Re: Multiple TRack AHB Crossings

Unread postby mossend4 » Wed Sep 17, 2014 12:23 pm

AndyB wrote:I have memories of the limit in more recent times being two running lines, and two sidings (although it sounds from all the above that it may now be only one siding). I would hope that the sidings would require the crossing to be transferred to local control!


The most recent photos from the same website were taken on 25/5/07 and show in combination that the upgrades to 100+ mph running and an MCB3 crossing have taken place, and that it was / is still 3 tracks.

Looking north
http://www.railbrit.co.uk/imageenlarge/ ... p?id=15311

Looking south
http://www.railbrit.co.uk/imageenlarge/ ... p?id=15316

The third track is / was the Up loop giving access at its south end to Carlisle New Yard. From memory, the Longtown MOD ‘long siding’ came off the north end of it and in 1990s there was a plan to extend it to a new railhead to load Keilder forest timber. Your point about local control now raises the question in my mind that this track over the crossing looks to have been bi-directional in normal working from the very beginning, and surely specially equipped for that, considering AHBs were retro-fitted for wrong direction working many years after their original installation?
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Re: Multiple Track AHB Crossings

Unread postby Danny252 » Wed Sep 17, 2014 12:46 pm

What is the "siding" that people keep referred to? I didn't think the Up Goods was ever used reversibly (as well as being a signalled line), whilst the Longtown Siding ends at Mossband Junction to the North.
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