Suggestions for Dawlish avoiding route(s)

[LateThanNever]

When someone at the DfT compares the quotes for re-routing the line and for lobbing a lot of metre cubed aggregate on the beach I suspect it will.

Not so 'DafT 'after all!
Actually compared with having earth moving equipment up and down the beach as there is now - and has been most of the year - I suppose it's not really so different, just more permanent... But the sea wall is listed of course. Still it would (be more likely to) exist - just not so pretty from the sea or the much diminished/non existent beach!

 

[amcluesent]

Just cementing a standard flat coping stone to the wall seems a very poor approach, the overhanging lip just gets the full force of the wave surge so no wonder they're already coming off. Surely they should have finished the re-built wall with curved top that reflects the force of the wave back out to sea rather than allowing is to break over the line?

Cheap and cheerful

Engineered

 

[LWB]

Sea walls are failed technology. Their use on British coasts date from Victorian times but even then the physics behind their fundamental flaw was well known. Indeed the Pelton wheel of that era was a conspicuously successful application of the same effect. Rock armour is not pretty but is a far better solution.

If I could refer you to my previous post. 'Reflecting things back' causes a doubling in the total momentum change incurred (momentum being a vector)and thus doubling the force exerted on the structure. My reference to the pelton wheel is to an improvement in the design of turbine blades which makes productive use of this fact. As others on here clearly appreciate, using rock armour allows an initial 'give' in the defence spreading the momentum change over a greater time, thus lowering the maximum force exerted. Not unlike a crumple zone in a car. Modern sea defence work such as Morecambe sea front etc try to avoid structures such as the one you show.

 

[jmc100]

Yesterday was a bad day for travel along the sea wall. If any members had a look at the video posted here or took a look at the live webcam you will know what I mean.

How was Brunel able to construct the sea wall in the first place without all the work being washed away during times of bad weather. Did he build a temporary retaining wall further away from the path of construction?

Another point I have thought about is electrification of the sea wall route, whenever it's due to take place. During times of bad weather, what effect will the spray have on the 25kv overhead lines when no more diesel traffic is running or available? The only problem I can see with the Dartmoor route in the winter would be snow. Other than that there should be no other problems.

 

[John S2]

How was Brunel able to construct the sea wall in the first place without all the work being washed away during times of bad weather. Did he build a temporary retaining wall further away from the path of construction?

Another point I have thought about is electrification of the sea wall route, whenever it's due to take place. During times of bad weather, what effect will the spray have on the 25kv overhead lines when no more diesel traffic is running or available? The only problem I can see with the Dartmoor route in the winter would be snow. Other than that there should be no other problems.

Electrification of the Dawlish route should be a non-starter given that this stretch of line will end up in the sea in due course.
The reason why this stretch of line is becoming more vulnerable is that sea level is rising. Given that our leaders are showing little enthusiasm for tackling the underlying cause of sea level rise, we can expect a substantial rise by the end of the century.

 

[starrymarkb]

Another point I have thought about is electrification of the sea wall route, whenever it's due to take place. During times of bad weather, what effect will the spray have on the 25kv overhead lines when no more diesel traffic is running or available? The only problem I can see with the Dartmoor route in the winter would be snow. Other than that there should be no other problems.

50kV insulation. See Saltcoats

 

[snowball]

Electrification of the Dawlish route should be a non-starter given that this stretch of line will end up in the sea in due course.
The reason why this stretch of line is becoming more vulnerable is that sea level is rising. Given that our leaders are showing little enthusiasm for tackling the underlying cause of sea level rise, we can expect a substantial rise by the end of the century.

If it gives several decades service it could well be economically worthwhile to electrify.

 

[John S2]

If it gives several decades service it could well be economically worthwhile to electrify.

I think we can predict with a high probability that there is little chance of getting several decades of reliable service on this line. Not every winter will see storms as severe as last winter with winds from the wrong direction, but each time there is a recurrence of this weather type with equal severity then the storm surge will be higher.

 

[21C101]

If it gives several decades service it could well be economically worthwhile to electrify.

The underlying cause of the sea level rising is the south coast slowly sinking because scotland is slowly rising as a result of the end of the last ice age meaning there is no longer the weight of a mile and a half deep ice pressing down on Scotland so the tectonic plate we are all on is slowly tipping back to equilibrium. Nothing HMG can do about that.

 

[John S2]

The underlying cause of the sea level rising is the south coast slowly sinking because scotland is slowly rising as a result of the end of the last ice age meaning there is no longer the weight of a mile and a half deep ice pressing down on Scotland so the tectonic plate we are all on is slowly tipping back to equilibrium. Nothing HMG can do about that.

It is correct that land in much of the South of England is slowly sinking due to the reason given above, but it is factually incorrect to suggest that this is the dominant cause of coastal structures becoming more vulnerable to the sea.
At Weymouth [I don't have a figure for Dawlish] the land is estimated to be subsiding at 0.41mm/yr, other locations in the South are subsiding at slightly less or slightly greater rates than this.
The point is that sea level rise due to man-made global warming is currently 8 times this rate. Land subsidence is relevant of course as it makes matters even worse, but it is not the dominant factor.

 

[47802]

Which despite the expense suggests there should be an alternate line but not Okehampton, one which leaves mainline services unaffected and provides the extra capacity needed between Exeter and Newton Abbot.

 

[MarkyT]

One thing noticeable recently is the way the signalling has remained fully operational during the heavy weather, due mainly to the use of axle counters instead of track circuits for train detection. Track circuits were also (mostly) absent in the days of Absolute Block prior to 1980s resignalling, which installed continuous track circuits together with the new colour light signals controlled by Exeter PSB. For safe operation, track circuits are adjusted finely to detect a very small change in resistance between the rails through the ballast. Salt water changes the normal ballast resistance quite significantly and with the amount of sea spray during winter storms, widespread track circuit failures were experienced with serious consequent delays, and normal operation could not be restored until the ballast dried out sufficiently which could be an extended period during storm conditions, all the while relying on talking drivers past red signals. Axle counters by contrast have no electrical connection to the rails, and the rail mounted sensor units are well sealed against the elements. I expect axle counters are also used at Saltcoats.

Quickly following the initial winters' poor performance along the Dawlish sea wall a special emergency Absolute Block system was set up for use during storms to clear signals under special instructions. It was operated by key switches on the panel, and only the supervisor held the keys, not the regular signaller. I never saw instructions produced, but I expect the supervisor had to set up a system for reporting 'trains out of section' by telephone from the extremities of the special long block. That system was only a stop-gap however and a project to replace all the track circuits with axle counters was commenced, starting with the Dawlish Warren - Teignmouth section, then the Exe estuary where spray was also a problem.

 

[Rapidash]

Yesterday was a bad day for travel along the sea wall. If any members had a look at the video posted here or took a look at the live webcam you will know what I mean.

Please don't exaggerate the issue. I commuted both ways yesterday. It was windy, sure, and a fair amount of water was flying all over the place, but it all added up to a whopping three minute delay in either direction.

If you want things to be better for XC, then perhaps you should encourage 'em to use their HST's down here in the winter, seeing as the Voyagers are doing a damn good impression of having aquagenic pruritis.

 

[starrymarkb]

Indeed a bigger problem in these conditions is leaf fall on the banks. It's possible to lose 10-15 mins through there if conditions are right (wet, windy and autumn)

 

[jmc100]

Please don't exaggerate the issue. I commuted both ways yesterday. It was windy, sure, and a fair amount of water was flying all over the place, but it all added up to a whopping three minute delay in either direction.

No exaggeration at all. I intermittently monitored what could be seen on the webcam from approx. 9.30am to just after noon and the waves were really getting angry. In fact, it looked pretty scary and this weather was mild compared to the storms earlier in the year. Suggest you view the replay for yesterday at the Dawlish Beach website.

 

[D1009]

Indeed a bigger problem in these conditions is leaf fall on the banks. It's possible to lose 10-15 mins through there if conditions are right (wet, windy and autumn)

Or in the case of yesterday's 1006 Padd, around an hour.

 

[Chris125]

It's good news if the South West peninsula speaks as one voice on this, and well done to Central Devon for getting the Okehampton route included in the package. Let's hope they keep up the pressure to make sure it doesn't get sidelined.

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

 

[LateThanNever]

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

They are credible as long as you realise it's the old technique of ask for a mile to gain a 100 yards. You can then claim some success even if you get only part of what you asked for....

 

[47802]

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

I think that's absolutely right, the idea that both a new Exeter Newton Abbot line and reopening the Okehampton route would be funded is beyond belief.

 

[D1009]

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

I think the point is that no-one really knows how much money the Govt. wants to throw at public transport in the South West, so it effectively puts the ball back in their court as to how to take the issue forward.

Leaving costs out of it, there is surely more benefit in the C options in the NR report, so if something more than the cost of reopening the Tavistock route can be afforded, it would be silly to say no we don't want it.

 

[Rich McLean]

In the long term, with more capacity required in the future, a new inland route EXD - NTA is more than likely that the Okehamton route is likely, but I won't expect to see this until around the 2030 mark. It is in an NR Report somewhere.

Currently plans is for 6tph down the sea wall post IEP introduction. By 2030 2tph Plymouth - London will more than likely be required, and possibly 1tph Paignton - Padd, making that 8tph (2 x XC, 3 x HSS, 2 x Locals, 1 x Semi Fast PZN - BRI). Not even the re-signalling scheme in 2025 will allow for that, so for that alone is the reason why the Okehampton route won't be implemented any time soon.

With a fast line they could have 4tph along the current route:
2 x Locals, 1 semi fast, 1 x HSS/XC (paignton alternate hours)

With the new direct line
2 x HSS,
2 X XC/HSS (paignton alternate hours)

But yes, you are looking at 2030 at the earliest for the above. Also, Newton Abbot would need a re-build

 

[Chris125]

I think the point is that no-one really knows how much money the Govt. wants to throw at public transport in the South West, so it effectively puts the ball back in their court as to how to take the issue forward.

I think we can safely assume they won't be funding two alternative routes!

What they are doing is asking government to fund a scheme with a questionable business case and suffer the backlash of choosing one route over another because they can't, or won't, decide amongst themselves - that's passing the buck, not 'speaking with one voice'.

Chris

 

[yorksrob]

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

Then it's vital that central and north Devon keep the pressure up and don't get sidelined.

 

[47802]

Then it's vital that central and north Devon keep the pressure up and don't get sidelined.

here we go again that sounds like trying to justify reopening Okehampton on the back of the Dawlish Problem.

The best solution is a new line between Newton Abbot and Exeter, that's what should be pushed, and if funding for that looks impossible only then should the Okehampton option be considered as a cheaper solution

 

[yorksrob]

here we go again that sounds like trying to justify reopening Okehampton on the back of the Dawlish Problem.

The best solution is a new line between Newton Abbot and Exeter, that's what should be pushed, and if funding for that looks impossible only then should the Okehampton option be considered as a cheaper solution

Or rather, build up Dawlish beach with those large rocks (which Dawlish town will need anyway) and let Okehampton act as a back up.

At any rate, they should counter the drivel from South Devon about a reopened route being "a disaster".

 

[The Ham]

That isn't my idea of 'speaking with one voice' - to be credible the 'The Peninsula Rail Taskforce' needs to decide whether they want the route via Okehampton reopened or a new Exeter-Newton Abbott line, asking for both is dodging the issue as the idea government would fund both is laughable.

Chris

But the new line options only cover part of the distance between Exeter and Newton Abbott, meaning that further work will need to be undertaken to provide the whole length required by the RUS (circa 2040).

Therefore, whichever is built further works will be needed. It then boils down to what is better in the long run and how much it costs.

If you build the new line (£3bn) and then spend a similar amount again, to get a time saving of upto 15 minutes.

Conversely, build the line Via Okehampton (£1bn) and then spend (say) £5bn on a new direct line between Exeter and Newton Abbott, there will be bigger time savings AND have the line via Okehampton.

Even if the second option costs more, it could still provide better value as there would be more benefits due to being a faster, more direct line and the line through Okehampton.

 

[Chris125]

Then it's vital that central and north Devon keep the pressure up and don't get sidelined.

If Exeter-Newton Abbott needs 4 tracks in the medium/long-term can hundreds of millions really be justified on a third route?

I'd love to the line via Okehampton reopened but the priority must surely be strengthening the existing route, with longer term capacity, electrification and journey time improvements catered for by an inland route in due course.

Chris

 

[21C101]

I don't want to sound flippant, but I do find the idea that a four track railway would be needed from Exeter to Newton Abbot laughable. For basically an hourly service each way from Plymouth to Padd, an hourly cross country, two suburban services an hour and the odd intercity to Paignton?

The Brighton line carries about three times that amount of trains (and most twelve cars to boot) and is only two track south of Three Bridges. No one is planning to quadruple that (or even build a flyover at Keymer Junction), so quadding Exeter-Newton Abbot really has to be wholly in fairytale territory.

 

[Rapidash]

Its less about the number of trains and more about the order they go in along the wall.

 

[LateThanNever]

I don't want to sound flippant, but I do find the idea that a four track railway would be needed from Exeter to Newton Abbot laughable. For basically an hourly service each way from Plymouth to Padd, an hourly cross country, two suburban services an hour and the odd intercity to Paignton?

The Brighton line carries about three times that amount of trains (and most twelve cars to boot) and is only two track south of Three Bridges. No one is planning to quadruple that (or even build a flyover at Keymer Junction), so quadding Exeter-Newton Abbot really has to be wholly in fairytale territory.

Think that is probably true- in part Exminster Marshes or even Marsh Barton could probably be four tracked to increase capacity - avoiding building out to the sea at Dawlish! But Brighton doesn't have long distance trains from Aberdeen or even Penzance (roughly 100 miles to Exeter) which gives a great deal of potential problems for delay when interspersed with all station locals. Brighton line is much more compact. If you want to go long distance from Brighton there is no choice but to change in London (regrettably!) It's a long, long time since there was a train from Brighton to Penzance..