|
Post by xtmw on Jun 27, 2024 17:59:43 GMT
We unfortunately live in an age where nowadays saving money is more important
|
|
|
Post by spsmiler on Jun 27, 2024 18:08:51 GMT
I’d beg to differ about the Aldgate 1 reverse it is used regularly whenever the district falls over and its loss will have a huge impact on maintaining and recovering the circle line during disruption. Just as the removal of the crossover that allowed the reversal back north from baker 3 was a huge loss for the operation of the met this decision seems similarly short sighted and based purely on saving money rather than what’s best for the service . Just my opinion but one I feel is worth stating I understand what you are saying - its not an aspect that I had considered. Can outer rail Circles reverse in the Met platforms (if available?!) Moorgate is a very poor alternative, although the advent of the Elizabeth line's connection with this station does mitigate some of the draw backs.
|
|
|
Post by wonderwaller on Jun 27, 2024 19:55:39 GMT
I’d beg to differ about the Aldgate 1 reverse it is used regularly whenever the district falls over and its loss will have a huge impact on maintaining and recovering the circle line during disruption. Just as the removal of the crossover that allowed the reversal back north from baker 3 was a huge loss for the operation of the met this decision seems similarly short sighted and based purely on saving money rather than what’s best for the service . Just my opinion but one I feel is worth stating I understand what you are saying - its not an aspect that I had considered. Can outer rail Circles reverse in the Met platforms (if available?!) Moorgate is a very poor alternative, although the advent of the Elizabeth line's connection with this station does mitigate some of the draw backs. Yes they can use the middle platforms at Aldgate there’s booked trains early morning and late night that do that but you can’t use that during the day because there’s a full met service reversing there so if the outer rail is suspended normally one would reverse at Aldgate and two at Moorgate you can maintain a full inner rail service that way if you can run them or it gives options to get trains back to Hammersmith without completely destroying the met
|
|
|
Post by jimbo on Jun 27, 2024 20:12:53 GMT
The Baker Street plat 3 crossover was promised to return when the whole layout was renewed, but that was subsequently dropped!
|
|
|
Post by jimbo on Jun 27, 2024 20:17:04 GMT
There are plans to add an extra crossover to permit parallel met arrivals/departures I am surprised that this is not already possible. Even though it very much depends on which platforms the two trains are using it does sound like a welcome added benefit. It is already possible, you just cut the quote too short: "which compensates for the removal of the other single slip".
|
|
|
Post by jimbo on Jun 27, 2024 20:21:03 GMT
Yes and no. The two single slips are planned to be removed, which removes the possibility of reversing a Met or Circle train in Aldgate OR platform, but in practice it's not possible to berth an S8 in there and get all doors open (they have to draw forward into the trap road) and it doesn't get used a lot even for an S7. This has been compensated for by the provision of additional reversing capacity at Tower Hill (using the middle platform). Does this mean that an S8, entering the outer rail platform in error, can now continue to Tower Hill to reverse? A long while since that station saw an 8-car train!
|
|
|
Post by goldenarrow on Jun 27, 2024 20:35:36 GMT
Yes, Tower Hill can take an S8 in emergencies along with reversing east of Whitechapel
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jun 27, 2024 21:05:00 GMT
Can outer rail Circles reverse in the Met platforms (if available?!) Moorgate is a very poor alternative, although the advent of the Elizabeth line's connection with this station does mitigate some of the draw backs. Yes they can. Additionally since resignalling all four platforms at Moorgate can be used to reverse the service - previously Platform 2 was Westbound/Inner Rail only, there is now an EB move into it.
|
|
|
Post by jimbo on Jun 27, 2024 22:40:57 GMT
Yes, Tower Hill can take an S8 in emergencies along with reversing east of Whitechapel Are 'rusty rail' trips booked for S8 trains to keep staff familiar with these moves? I would like to see one! I believe the Whitechapel move can carry passengers, to cope with a situation when a Met train arrives at the junction, but a route into Aldgate cannot be obtained.
|
|
Colin
Advisor
My preserved fire engine!
Posts: 11,330
|
Post by Colin on Jun 28, 2024 8:55:13 GMT
No, there are no booked "rusty rail" trips for S8's to either Tower Hill or Whitechapel.
Similarly, there's a number of moves around Edgware Road, High Street Kensington and Gloucester Road that Circle and Hammersmith & City drivers are fully trained on but District drivers are not.
If such moves are required, a "pilot" must be sought to guide the driver. A pilot must be familiar with the moves concerned.
|
|
|
Post by dmncf on Jul 4, 2024 11:51:11 GMT
I understand that the CBTC signalling has axle counters to provide a secondary form of train detection. In the CBTC 'core' area where all passenger trains are fitted with CBTC signalling equipment, does the existence of axle counters create a constraint for passenger trains, i.e. does it create signalling block sections?
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jul 4, 2024 12:26:08 GMT
Only when there are non-communicating trains running around.
|
|
gefw
Gone - but still interested
Posts: 164
|
Post by gefw on Jul 4, 2024 17:55:32 GMT
I thought in points and crossing areas, Fixed track blocks (defined by axle counters) are always used by the SCS (local safety processing system) for point track locking. The size/boundaries of these Axle counter blocks and system delays in determining & communicating the status would therefore be a constraint affecting the releasing of points (after the passage of any train).
|
|
|
Post by notverydeep on Jul 8, 2024 12:58:36 GMT
I’d beg to differ about the Aldgate 1 reverse it is used regularly whenever the district falls over and its loss will have a huge impact on maintaining and recovering the circle line during disruption. Just as the removal of the crossover that allowed the reversal back north from baker 3 was a huge loss for the operation of the met this decision seems similarly short sighted and based purely on saving money rather than what’s best for the service . Just my opinion but one I feel is worth stating It is worth noting that the existing layout cannot be replicated with flat bottom rail components and these are now required by the LU Engineering Standards. Standard components tend to offer greater reliability. It was understood at the outset of the Sub-Surface Upgrade in the early 2000s that this move would eventually be lost when the junction work at Aldgate was renewed and the new (and fairly expensive) facility at Tower Hill was partly intended to provide a replacement. Despite this, options to include the reversal from platform 1 have been reconsidered recently, but would have added very significantly to the cost and complexity of the renewal...
|
|
|
Post by spsmiler on Jul 8, 2024 14:14:29 GMT
Wow, the type of rail is now determining train operations and service flexibility.
That said I have long wondered why bullhead rail is still used when its as much an antique as the heritage rolling stock. Its just that I never ever imagined that rail types could affect track layouts.
|
|
|
Post by xtmw on Jul 8, 2024 17:55:36 GMT
Would be a waste of money if I'm being honest, sections of the Underground still use perfectly good bullhead rail. If a section is re-railed then it'll get replaced with flatbottom rail. Although in the past 10 years sections have been re-railed with bullhead rail. Eg, Stratford in 2010 if I remember correctly?
|
|
|
Post by notverydeep on Jul 10, 2024 15:14:40 GMT
At an internal open day at the Lillie Bridge workshop making up switches and crossings that LU was the largest buyer of new bull head rail in the world. However, the problem with the existing layout and simply re-railing where required, is that it does not facilitate the higher frequency through Aldgate that is the key objective of the wider Sub-Surface upgrade and without which the benefits of all the other signalling works can't be realised.
|
|
|
Post by joshua on Jul 20, 2024 16:11:21 GMT
There is some doubt about the current signalling coping with 20tph to Wimbledon in that case. I am fairly sure that Wimbledon Branch is three-aspect signalling between East Putney and Wimbledon so couldn't that be upgraded to four aspects by replacing signal heads and installing extra signals halfway between the current signals? Also does the differential speed limit affect capacity with LUL trains allowed to do 45mph where as NR trains are limited to 30mph?
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jul 20, 2024 21:07:48 GMT
Wow, the type of rail is now determining train operations and service flexibility. Its just that I never ever imagined that rail types could affect track layouts. It used to, but TfL has also developed a new switch rail design and profile which enables a full-depth flat bottom switch to occupy a similar footprint to a bullhead one. As such the use of bullhead rail profile will continue to be reduced and ultimately eliminated.
|
|
Colin
Advisor
My preserved fire engine!
Posts: 11,330
|
Post by Colin on Jul 20, 2024 22:27:04 GMT
I am fairly sure that Wimbledon Branch is three-aspect signalling between East Putney and Wimbledon so couldn't that be upgraded to four aspects by replacing signal heads and installing extra signals halfway between the current signals? Also does the differential speed limit affect capacity with LUL trains allowed to do 45mph where as NR trains are limited to 30mph? If only it were that simple. Whilst it is a fact that more signals = more capacity, there is a limit as to how many signals you can bung in. Signals are positioned according to a number of factors, such as the fastest speed of trains, the weight of trains, the braking capacity of trains, gradients, etc. Four aspect signals would be pointless as the maximum line speed is 45mph; there is absolutely no need to know that you're three sections ahead clear at that speed! At one end of the National Rail signalled area you've got a 30mph LU signalled section and at the other end a 10mph four platform terminus with a number of conflicting moves. I can't really see what's to be gained over such a short section with those constraints at either end of it. And does the 30mph speed limit for South Western Trains restrict capacity? Absolutely! And more than that, they create havoc when they crawl into Wimbledon Park depot at 5 mph! It's also worth bearing in mind the reason why they are restricted 30mph; their braking capacity is much less effective compared to LU stock - in other words it takes them a far greater distance to come to a stop. That has to be factored into the signalling system!
|
|
|
Post by joshua on Jul 20, 2024 23:34:55 GMT
If I am not mistaken Thameslink core has four aspect signalling with 20mph limits in the core with ETCS L2 overlayed on top. By going to four aspects it would allow for more diversions and an increased number of underground trains. Was the NR 30mph limit based on current South Western Railway stock or did they use the Network South East slam doors when it was last resignalled? Would it be possible to upgrade the line speed into Wimbledon depot to 10 or 15mph? I knew that the speed limit is based on braking distance but I guessed it was also to allow NR trains to better match the average speed of the LUL trains, which seems to be an incorrect guess on my part.
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jul 20, 2024 23:48:49 GMT
I'm not so sure Colin. Once CBTC comes in on the branch as far as East Putney the traditional constraints associated with the signalling capacity are (in theory) gone, so it might well be the fixed-block section that becomes the pinch point.
Theoretically, if you go from 3 to 4 aspect but the line speed and braking distances don't change, this is what you do - simply halve the distance between signals and stick another in at the half way mark. The critical thing is making sure the braking distance from the first cautionary aspect to the red remains the same - I believe this has been done on some of the LTS section where it runs parallel to the District.
However, it does come with significant initial and whole-life cost and with all such things there is a law of diminishing returns - especially on a signalling system that is over 30 years old and getting near to the end of its design life.
I note the branch is heavily restricted in what national rail stock can run along it, but I would question if the braking capacity of EMU stock is much less effective - they were traditionally similar to LU in terms of braking systems and on four aspect sections where the signal spacing had to take into account a mix of traction and rolling stock, it was suggested that drivers of EMUs did not require the full braking distance from a double yellow to a red and were still able to stop comfortably from a single yellow (though the Human factors concerns about this practice are for another discussion!).
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jul 20, 2024 23:50:59 GMT
Was the NR 30mph limit based on current South Western Railway stock or did they use the Network South East slam doors when it was last resignalled? Would it be possible to upgrade the line speed into Wimbledon depot to 10 or 15mph? The signalling would have been designed around SR 1963-type EMUs, but the NR Sectional Appendix shows the 30mph restriction still applying to the current SWR fleet. Line speed across the junctions into Wimbledon Park is 15mph but that doesn't mean that they necessarily drive at it!
|
|
|
Post by d7666 on Jul 21, 2024 13:06:03 GMT
I'll throw my 5 eggs in here an suggest any capacity increase on NR metals in the SW area will await Waterloo area ETCS and no-one will upgrade or resignal anything before then.
I can't remember now where we are with these things, but it is something like NR ETCS on GN main line routes from Kings Cross is the first main line ETCS area scheme, second GW from Paddington, and third SW from Waterloo***; yes all this is yet a long way off - but it real terms but I'll suggest we'll get to that point in time way before anyone finds money to tear up signals and track circuits just to jump from 3 to 4 aspect signals along here.
& before someone mentions these things - yes I am aware Thameslink core and ex-Northern City have ETCS in some shape or form - I am talking about about main line area schemes not pockets where local specific circumstances take advantage of it.
There will be a need to interface LU CBTC with NR ETCS but that is manageable, including it's implementation on S-stock+++. Outside my domain but I can think of at least 2 ways it could be done.
Also, one other thing to remember is these days at least as far as main line trains are concerned, double yellow on a 4 aspect signal is much more restrictive than it used to be.
The original concept behind the YY aspect was, in simplified terms, freight trains (then majority unfitted) commence braking but passenger trains commence braking at Y.
In these days of main line defensive driving, YY is now commence braking for all trains; in turn has a negative knock on effect of throttling capacity. The theoretical capacity jump from 3 to 4 aspect signalling is much diminished.
Not braking at YY is pretty well standard checks carried out in random audits of main line train OTMR and is regarded as a serious issue almost possibly even treated equal to a SPAD.
How a LU train would be managed with in this respect I can not comment on.
*** one, of several, reasons behind the incumbent SW TOC went / going for total demolition / displacement of the mixed up 455 456 458 707 suburban EMU fleet and replace all with one type (701) is those 701 are all ETCS ready hence easier and cheaper to activate when needed. ((The issues with actually getting 701s into service are irrelevant.)).
+++ and once you have done that, it more or less hands you the solution to kill the retained Amersham Harrow clockwork signalling for Chilterns as by the time we get that far, Chilterns or whoever they are by then will almost certainly have had the fleet replaced by new whatevers sourced from whoever that will be ETCS ready.
|
|
Tom
Administrator
Signalfel?
Posts: 4,160
|
Post by Tom on Jul 21, 2024 17:39:17 GMT
I'll throw my 5 eggs in here an suggest any capacity increase on NR metals in the SW area will await Waterloo area ETCS and no-one will upgrade or resignal anything before then. I rather suspect you are right, but at that point the question will be: Will Point Pleasant to Wimbledon form part of an ETCS scheme? Remembering that from East Putney to Wimbledon London Underground is the owner of the track and signalling and the infrastructure manager - when the time comes to close Wimbledon panel, it would be pragmatic to extend CBTC to Wimbledon with an underlay arrangement similar to that being implemented on the Metropolitan Line, thus allowing Network Rail to be free of their obligations to LU in providing certain functions * and LU to be free of their financial obligations with regard to paying for those functions, leaving LU in control of their own destiny, so to speak. * - obviously the need to interface with NR will continue, and the method of providing train protection will naturally be a point of debate.
|
|
|
Post by d7666 on Jul 21, 2024 19:44:05 GMT
I'll throw my 5 eggs in here an suggest any capacity increase on NR metals in the SW area will await Waterloo area ETCS and no-one will upgrade or resignal anything before then. I rather suspect you are right, but at that point the question will be: Will Point Pleasant to Wimbledon form part of an ETCS scheme? Remembering that from East Putney to Wimbledon London Underground is the owner of the track and signalling and the infrastructure manager - when the time comes to close Wimbledon panel, it would be pragmatic to extend CBTC to Wimbledon with an underlay arrangement similar to that being implemented on the Metropolitan Line, thus allowing Network Rail to be free of their obligations to LU in providing certain functions * and LU to be free of their financial obligations with regard to paying for those functions, leaving LU in control of their own destiny, so to speak. * - obviously the need to interface with NR will continue, and the method of providing train protection will naturally be a point of debate. Well, yes, I had not thought of it that way, it certainly opens up alternatives, wherever / whatever train protection is in use.
|
|
|
Post by joshua on Jul 21, 2024 20:12:03 GMT
Is it better to have the transfer between signalling systems on plain line rather than at Wimbledon, with moves in and out of the depot, SWML services, diversions and London Underground services? If so would it not make sense to retain the change in signalling at East Putney? Also looking at the Network Rail website, there is a document which says that says the Wimbledon to East Putney section will not get resignalled until CP10. The Network Rail ETCS resignalling doc = www.networkrail.co.uk/wp-content/uploads/2019/06/Digital-Long-Term-Deployment-Plan.pdf
|
|
|
Post by spsmiler on Jul 21, 2024 21:51:36 GMT
Maybe the differential speed limit is because the SWR trains pass through stations without stopping?
|
|
|
Post by gigabit on Aug 2, 2024 23:26:53 GMT
Can somebody explain why they don't just abandon the SWR trains running over the LU track and then just allow the LU track to be properly signalled all the way to Wimbledon?
|
|
|
Post by 35b on Aug 3, 2024 12:10:24 GMT
Can somebody explain why they don't just abandon the SWR trains running over the LU track and then just allow the LU track to be properly signalled all the way to Wimbledon? Because it provides access to the depot at Wimbledon without impacting capacity on the main line out of Waterloo. London’s transport is a system, with SWR and the District Lines subsidiary parts of it. A change to one must affect the other. This stretch is shared infrastructure, required by both LU and SWR.
|
|