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| ELRs at Mountain Ash 18/09/2022 at 19:35 #148055 | |
clive
2789 posts |
Mountain Ash (aka Aberpennar) is on the Aberdare branch of the Cardiff Valley lines. According to the most recent Quail, the branch leaves Abercynon with ELR ABD with a mileage of 16m26c. Heading in the Up direction, it's single line to just before Mountain Ash, where there is a loop on the down side from 19m60c to 20m16c (i.e. 36 chains) through the station. It then continues as far as Cwmbach New Jn where the ELR changes to ALK and then shortly afterwards to VON. What's odd, though, is that the down loop at Mountain Ash has a separate ELR: MOA. I've never come across that before - a separate ELR for the two tracks of the same line. As best I can judge from both Google Maps and riding the line, it's a single alignment. So why has this been done? Modern Railways for August thickens the plot. If I'm interpreting it correctly, the entire line - both tracks - is now MOA for the length of the loop and the chainages are now 0m38 at the down end to 0m00 at the up end. Meaning that the line has grown 2 chains. MR's report also makes the chainage of the station 0m23c, which is 7 chains south of the 20m02c that Quail shows. Can anyone explain this? Log in to reply |
| ELRs at Mountain Ash 18/09/2022 at 19:46 #148056 | |
headshot119
4869 posts |
The loop was installed around 2002, and I suspect the MOA ELR applied to both lines from that point (Mountain Ash Deviation) certainly by 30/06/2008 the Table A of the relevant SA quotes MOA as the ELR for both lines applying from 19m 60c (00m 00c) to 20m 16c (00m 38c). I suspect quail has simply made a mistake in assuming MOA only applied to the loop line.
"Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| ELRs at Mountain Ash 18/09/2022 at 19:49 #148057 | |
Steamer
3984 posts |
There was a clarification to that item in the September issue, in which it's stated that MOA applies only to the Down Loop, and that the MOA 0m 00ch is in fact at the Down (south) end, increasing to 0m 38ch at the Up (north) end. This makes the station chainage tie in (almost- 1 chain difference) with the ABD measurement. Why MOA exists, and why they've decided to re-measure it, is beyond me though... "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| ELRs at Mountain Ash 18/09/2022 at 20:29 #148058 | |
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clive
2789 posts |
Thanks, Steamer. I haven't got round to reading that issue yet. Measuring the chainage the other way makes more sense; as you say, it makes the station chainage tie in. My best attempt with Google Maps gives me 750 metres for the loop from toe to toe, which is 37.5 chains. But there's no way there's a 2 chain difference; this must be a resurvey, presumably to do with the new points mentioned in the August MR. So it would actually make more sense for both tracks to be MOA to avoid the mess of a 2 chain discrepancy in ABD. The use of a separate ELR for one track still doesn't make sense, though. Given that there are places where the same ELR is used on wildly different tracks (I'm thinking of SSV, there there's no way that the loop to Mountnessing Jn is the same length as the main route of the branch, and Google Maps makes it 4 chains longer), why do it at this one place? Log in to reply |
| ELRs at Mountain Ash 18/09/2022 at 20:38 #148059 | |
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headshot119
4869 posts |
There's been no change between 30/06/2008 and an update to Table A of the sectional appendix on 28/05/2022, both imply the MOA ELR applies to both lines. Unless there's a more official source from Railtrack or Network Rail, I still go with the school of thought that an assumption has been made by external publications that MOA only applied to the loop line, and it's always applied to both lines since the second track was added in 2002. The discrepancy in distance is easily accounted for by a resurvey of that area. Further interestingly the scale diagrams the simulation are built from make no reference to a mileage change, everything around that area is between the 18m and 22m posts. "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Last edited: 18/09/2022 at 20:44 by headshot119 Reason: None given Log in to reply |