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Thameslink Core congestion (01/02)
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RailUK Forums
Surreytraveller
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My be they're using the POSAs?
dk1
Veteran Member
Points failure St.Albans has caused many issues this morning & signalling issues at St.Pancras are adding to the disruption.
Dren Ahmeti
Member
Not just possibly...
“LNE is affected by melting ice & snow causing track circuit failures in the Thameslink Core. Southbound services are being delayed up to 8 minutes due to the failure of TCG and TCP track circuits between St. Pancras International and Farringdon. The train service has been reduced by 7 trains per hour as a result of this issue. No change is expected until the flood water recedes.”
They cancel trains.
dk1
Veteran Member
Loads. Some work, some don't. Every weather scenario is different. Only so much can be done.
The Box Photter
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For once, this doesn't seem to be GTR's fault (but they still have to react appropriately).
As they say:
"It has been discovered that this is the result of flooding within the tunnels that operate through Central London and specialist teams are currently onsite and are attempting to drain and pump away excess water to allow full testing and repair to be carried out to the signalling system. It was originally believed that melting snow and ice was the cause of the issue, however several leaks have been found in the tunnel walls so further assessments are ongoing to establish the exact cause of the water ingress."
On their App it also says:
"It was also discovered that part of the drainage system that allows water to drain away in this section has become blocked due to sediment build up ..."
Today's infrastructure failures seem to lie squarely on the shoulders of Network Rail. Inadequate knowledge of what's behind the walls of their tunnels and inadequate maintenance of the drainage system. Seems like a re-run of what happened a few years back and caused the Core to be temporarily closed whilst Network Rail groped about in the dark trying to find out, (1) where the water was coming from and (2) why it wasn't draining away.
Given the lack of snow and ice in Central London, it ought to have been obvious from the start that the water wasn't a glacial melt. More likely to be a rotten water main that they didn't know about, poorly maintained by the equally incompetent Thames Water.
This should be a wake up call to all those still tumescent at the prospect of splashing £90bn on HS2 as the rest of the network is falling apart around us. Cancel HS2 and spend the money on getting the existing track, signals and power supplies up to scratch.
As they say:
"It has been discovered that this is the result of flooding within the tunnels that operate through Central London and specialist teams are currently onsite and are attempting to drain and pump away excess water to allow full testing and repair to be carried out to the signalling system. It was originally believed that melting snow and ice was the cause of the issue, however several leaks have been found in the tunnel walls so further assessments are ongoing to establish the exact cause of the water ingress."
On their App it also says:
"It was also discovered that part of the drainage system that allows water to drain away in this section has become blocked due to sediment build up ..."
Today's infrastructure failures seem to lie squarely on the shoulders of Network Rail. Inadequate knowledge of what's behind the walls of their tunnels and inadequate maintenance of the drainage system. Seems like a re-run of what happened a few years back and caused the Core to be temporarily closed whilst Network Rail groped about in the dark trying to find out, (1) where the water was coming from and (2) why it wasn't draining away.
Given the lack of snow and ice in Central London, it ought to have been obvious from the start that the water wasn't a glacial melt. More likely to be a rotten water main that they didn't know about, poorly maintained by the equally incompetent Thames Water.
This should be a wake up call to all those still tumescent at the prospect of splashing £90bn on HS2 as the rest of the network is falling apart around us. Cancel HS2 and spend the money on getting the existing track, signals and power supplies up to scratch.
Failed Unit
Established Member
Who GTR? They would not be the first time...
ChiefPlanner
Established Member
A few years ago - we had Lake Farringdon - water mains burst - it has happened on and off since about 1866. The area is a sump for the Fleet River.
You mean questions like "How much time do you get to inspect the drains in the tunnels?" and "roughly how long would it take to clear out any build up of sludge that may cause potential blockages?"
Despite being forecast, there wasn't any snow in central London last night, although there was a lot of rain.
There have indeed been flooding issues at Ray Street, north of Farringdon, where the line dips down under the Circle Line, for more than a century. The Metropolitan Railway adapted one of their last steam locos with a steam pump to be sent there to deal with periodic inundations. You would have hoped part of the Thameslink expenditure would have been to deal with it once and for all.
There have indeed been flooding issues at Ray Street, north of Farringdon, where the line dips down under the Circle Line, for more than a century. The Metropolitan Railway adapted one of their last steam locos with a steam pump to be sent there to deal with periodic inundations. You would have hoped part of the Thameslink expenditure would have been to deal with it once and for all.
What is a POSA?
EM2
Established Member
Proceed On Sight Authority.
I'd expect it to be needed at regular intervals, not when totally blocked. That's what happened when my local council cut its budget to clean drains from annually to every two or three years, causing major floods (one road totally impassable for days after rain) and then needing a massive operation to clean.
A subsidiary signal to the main aspect (two small flashing white lights, set diagonally, normally on the same signal post, and looking like a shunt signal).
The signal is normally deactivated, but the signaller can activate it and ‘pull it off’ when the route ahead is known to be clear, and all points detected, but a train detection section still shows occupied (usually a track circuit or axle counter failure).
The signaller must cancel the signal after each train, and reset it for each train, having first confirmed that the previous train has cleared the section concerned and the next section where the train detection is working.
The driver ‘proceeds on sight’ and must’ve be prepared to stop short of any obstruction. The first train through the section under POSA working must also be advised by the signaller to check the section is clear of obstructions and report back before any other trains can be sent through.
In the Thameslink core alone, my very rough guess is that since commissioning it has saved over a thousand cancellations and around 50,000 minutes of train delay.
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OFFDN
Member
Today’s issue has been problems with the track circuits south of St Pancras station, with trains being talked past TWH1031 and TWH1033, although one of these TCF’s has now seemingly rectified (or at least, hasn’t blipped in a significant time). 1031 is the signal at the south end of St Pancras platform A, for perspective.
There have been a lot of roadworks in the area recently, and a burst main at least. Only last week, I think, I was off duty at King’s Cross and saw the water company digging up the road outside the Five Guys/McDonalds at the intersection of Euston Road/York Way/Grays Inn Road - which fittingly is around the area of today’s issues.
Water leaks in the Thameslink core, particular north of Farringdon, have been a problem for many many years.
There have been a lot of roadworks in the area recently, and a burst main at least. Only last week, I think, I was off duty at King’s Cross and saw the water company digging up the road outside the Five Guys/McDonalds at the intersection of Euston Road/York Way/Grays Inn Road - which fittingly is around the area of today’s issues.
Water leaks in the Thameslink core, particular north of Farringdon, have been a problem for many many years.
Well that all made sense to me so thanks all for the info. I decided to bypass most of the core on the way home by using the Vic. tube to St Pancras. Whilst waiting for a down MML train I saw a couple of southbound trains held in platform B until what I now know to be the POSA signal was flashing. I could be mistaken but I think that the main signal was showing red throughout. So I've learnt something new today.
ChiefPlanner
Established Member
We are indeed plagued by this in (wealthy) St Albans - fed up of acting as unofficial drain clearer , when I can find a handy stick. Much of it down to lack of outside the city centre street sweeping.
To be fair , the Farringdon area issue is very multi-organisation , not just Thames Water.
Yes, the main aspect signal can not clear if a train detection section ahead is shown as occupied as the interlocking prevents it. The POSA is not interlocked to train detection (but is to point detection). The POSA will only ever be used whenever the main aspect can not be cleared from danger.
It’s not just me then!
Off Topic, but since St Albans D.C. took over the highway cleaning, it has been much better. They are routinely cleaning the main roads now, but the drains are still blocked despite gully clearing.
ChiefPlanner
Established Member
I regard it as community service !
OFFDN
Member
...and as suspected;
“Due to Emergency water works on A501 Pentonville Road at the junction of York Way Bus routes 17,45,65,259,N63 are on diversion eastbound at the junction of Euston Road.”
“Due to Emergency water works on A501 Pentonville Road at the junction of York Way Bus routes 17,45,65,259,N63 are on diversion eastbound at the junction of Euston Road.”
It's a bit off-topic still, but Herts Highways still do the drain cleaning - once every 18 months. Leaves drop off trees annually......
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