Barnstaple for Christmas?

[whole diary]

[swrural]

May I suggest we merge this topic to the flooding thread? 

The strategic answer would appear to be that the GW^▸ (Great Western) line is taken across (following the M5 trajectory) to the LSWR^▸ (London South Western Railway) one before it descends as far as Stoke Canon.  This would be a reversal of the gauge war period when the LSWR considered going round the back of Exeter.  Central (Queen St) still has a lot of capacity despite building over the goods area and there is just the short run down the hill (Could St Davids be then closed?).  The line would be retained to Cowley Bridge and elevated over the Exe more than it is now.  Then the line would be reinstated via Tavistock as a strategic option against the problems via Dawlish.

There you are Strategy in one paragraph!  As a footnote to Super Guard, (see his post), please accept my sympathy as you are an ex-resident of Stoke Canon.  I noticed an awful lot of new bungalows etc, down in the flood plain there.  What were these hopeless planners thinking?   Stoke Canon is sandwiched between the Exex and Culm rivers, both meanderers. 

[SandTEngineer]

Looks strikingly similar, except I expect all the signals worked OK after the water receded!

I much suspect that the signalling equipment was working under the water........

[Chris from Nailsea]

May I suggest we merge this topic to the flooding thread? 

Hmm.   On this occasion, I'm rather more inclined to leave things as they are: this particular discussion is more specific to a shorter journey in Devon than the more general discussion about the wider disruption caused by the flooding to travel 'across the West'.

[ellendune]

The strategic answer would appear to be that the GW^▸ (Great Western) line is taken across (following the M5 trajectory) to the LSWR^▸ (London South Western Railway) one before it descends as far as Stoke Canon.  This would be a reversal of the gauge war period when the LSWR considered going round the back of Exeter.  Central (Queen St) still has a lot of capacity despite building over the goods area and there is just the short run down the hill (Could St Davids be then closed?).  The line would be retained to Cowley Bridge and elevated over the Exe more than it is now.  Then the line would be reinstated via Tavistock as a strategic option against the problems via Dawlish.

There you are Strategy in one paragraph! 

I think you need to add another (vertical) dimension to your strategy to take into account Stoke Hill which presents quite an obstacle to going that way round. The M5 goes through a very deep cutting.  Given

Fitting enough platforms in at Central might also be a challenge.  St Davids has 5 through platforms Central only has 2. It would need a major rebuild to get 4 and I am not sure more would be possible in the constrained site.  I am also not sure how easy it would be to do a west facing curve to get from Central to Plymouth.

When I start to consider the cost a viaduct on the existing alignment starts to sound cheap. Apart from Cowley Bridge, are there any other locations along there where the railway has flooded?  If it is just there then a short viaduct on both lines for about 50 metres where the tributary joins may well fix it possibly slightly raising the alignment, at worst that might need a replacement bridge for the A377.

[John R]

When I start to consider the cost a viaduct on the existing alignment starts to sound cheap.

But how long would the route be closed for whilst it was constructed? Many months at least, if you really mean on the same alignment. Surely the level of disruption during this period would outweigh the long term benefit.

I'm inclined to think that a tactical upgrade of the lines between Exeter, Yeovil and Castle Cary would be the most cost effective solution. A couple of passing loops to enable a basic FGW^▸ (First Great Western) service could be slotted in, which would probably be of use anyway if the service to Waterloo continues to grow. Prepare a contingency timetable and ensure enough crews have route knowledge, maybe by routing one off peak service a day along the line.

That would still leave the Cross Country service to cater for. Presumably it becomes logistically much easier to source adequate buses with fewer passengers to cater for, and the option of a diversion via Westbury and Yeovil would also exist, though would possibly be unattractive due to the added journey time.

Edited by Brucey to fix quotes

[ellendune]

When I start to consider the cost a viaduct on the existing alignment starts to sound cheap.

But how long would the route be closed for whilst it was constructed? Many months at least, if you really mean on the same alignment. Surely the level of disruption during this period would outweigh the long term benefit.

It depends how much you needed to lift the track by. It is not as easy as building it to one side and sliding it in as you have the river on one side and the pub on the other. You could probably put it together in the sidings and move it along the track into position. However with a good design that is optimised for rapid installation and some careful preparation of the site to build new piled foundations during a series of overnight or weekend possessions a week-long blockade might be enough. 

There is never going to be a good time for it but a Christmas break might be enough. 

[John R]

That sounds optimistic to me, although I'm certainly not an expert on the subject. But a viaduct to me implies a series of support pillars, which support beams, which then support the base on the viaduct on which the track is laid. That would certainly take months, so maybe you are looking at something which raises the track but stops short of a full scale viaduct?

For anyone interested in how to construct a viaduct (maybe slightly larger than the one we are talking about here) there is an interesting website on the Hitchin viaduct construction hitchingradeseparation.blogspot.com

[Southern Stag]

I'm inclined to think that a tactical upgrade of the lines between Exeter, Yeovil and Castle Cary would be the most cost effective solution. A couple of passing loops to enable a basic FGW^▸ (First Great Western) service could be slotted in, which would probably be of use anyway if the service to Waterloo continues to grow. Prepare a contingency timetable and ensure enough crews have route knowledge, maybe by routing one off peak service a day along the line.

There are paths and crews with route knowledge available now though, it just seems that NR^» (Network Rail - home page) haven't offered any paths for FGW via Honiton.

[ellendune]

That sounds optimistic to me, although I'm certainly not an expert on the subject. But a viaduct to me implies a series of support pillars, which support beams, which then support the base on the viaduct on which the track is laid. That would certainly take months, so maybe you are looking at something which raises the track but stops short of a full scale viaduct?

For anyone interested in how to construct a viaduct (maybe slightly larger than the one we are talking about here) there is an interesting website on the Hitchin viaduct construction hitchingradeseparation.blogspot.com

But for Cowley bridge we are not talking about anything on that scale.  The supports would be installed before the closure. They could be installed, for example, either side of the track, with a beam installed between them during the closure, before the bridge is intalled on the top. 

[Chris from Nailsea]

That would seem to be a very simple and inexpensive answer to all of the construction issues, ellendune; is there any precedent for such an innovative engineering approach?

[JayMac]

The approaches to such a structure (which need ruling gradients suitable for the rail traffic using the line) would require some major civil engineering and the connecting of each end of this bridge/viaduct to the existing lines will not be a quick fix and would require a fairly lengthy possession I suspect.

Then there is the issue of just where you site the junction for the Barnstaple line. This would also need raising or re-routeing to connect with the main line.

And what of the roads? Does the A377 go over or under this new rail structure? And what of its closely proximate junction with the A396?

Finally there are the local property owners. What happens to the Chinese restaurant at the Cowley Bridge Inn? 

I honestly don't think there is an easy, cheap or quick solution to the problems at Cowley Bridge. All the civils, both road and rail would need major engineering solutions to raise them above a level where they won't be susceptible to flooding.  Make do and mend will, I fear, be the only option going forward.

[Tim]

How about putting the signalling cabinets on little mounds to keep them out of the water?

That would be a start.

[ellendune]

That would seem to be a very simple and inexpensive answer to all of the construction issues, ellendune; is there any precedent for such an innovative engineering approach?

Its not that innovative, bridges are prefabricated and moved into position all the time and piled foundations are installed in advance on many occasions. Caversham Road and Cow Lane Reading were notable examples of whole bridge slides. Those were moved in sideways, which would not be practicable at Cowley Bridge. 

The bridge would therefore either have to be moved in length-ways, or lifted in.  Probably a bit big for a lift in one piece. However if you could make the main-line and branch structures separate it might be possible for a steel structure.  A slide would be easier if you separate them.

It all depends on how much longer the span needs to be to provide the necessary flow area for the river, as from the photographs this seems to be the issue here. Raising the line would help a bit, particularly if the site has ever been flooded from the Exe, but flow width is probably the most importance point for the tributary. 

[paul7575]

There are paths and crews with route knowledge available now though, it just seems that NR^» (Network Rail - home page) haven't offered any paths for FGW^▸ (First Great Western) via Honiton.

I'd really like someone to quote an official source explaining exactly where all these spare paths are, I keep reading that a 2 tph service is possible, but I don't believe it.  (I've also read that SWT^▸ (South West Trains) won't allow it, because they are in charge of the alliance with NR - and I don't believe that either.)

AIUI^▸ (as I understand it) if the normal SWT service is running, all that can be added is either an additional train in one direction each hour, or alternate directions in alternate hours.

A full 2 tph service is not possible west of Axminster - we know this already as the additional FGW additional Exeter - Axminster service (proposed in the new franchise ITT^▸ (Invitation to Tender)) is constrained to be two hourly by infrastructure limitations.

Paul

[ellendune]

How about putting the signalling cabinets on little mounds to keep them out of the water?

That would be a start.

That is done in my industry to keep electrical equipment from risk of flooding