|
|
Post by spsmiler on Mar 13, 2021 11:55:11 GMT
Thanks for the replies ... certainly at busy times the northern side of the Circle (Aldgate - Baker Street) can become so swamped with trains that they are constantly catching up the train in front and therefore having to travel 'more slowly'. Automation allowing trains to travel more closely to each other will increase train capacity - but on a route with closely spaced stations it won't increase speeds.
But at quieter times the gaps between trains is wide enough for this to not happen, and this is when lower speed limits will be the reason for increased journey times.
Some passengers will not notice, others will!
My reference to speed limits which were previously deemed as 'safe' now, decades later, being deemed as 'unsafe' is a comment transferred from the situation regarding road traffic where advocacy of slowness with speed limit reductions has become commonplace.
|
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,763
|
Post by Chris M on Mar 13, 2021 14:33:07 GMT
My reference to speed limits which were previously deemed as 'safe' now, decades later, being deemed as 'unsafe' is a comment transferred from the situation regarding road traffic where advocacy of slowness with speed limit reductions has become commonplace. Road traffic speed limits and railway speed limits are different things and are not comparable. A railway speed limit is the maximum speed it is safe for a train to travel at. Hence differential speed limits for different types of train. The only difference between the safe speed and the signed speed (on traditionally driven lines) is rounding down to the nearest round number and avoiding many changes of limit in quick succession. A slower corner in the middle of two long straights will have it's own associated speed limit that is lower than the straight bits of railway. The safe limit is determined by multiple factors including kinematic envelope, dynamic load on structures, corner radius, signal sighting (although this is also partly dependent on the speed limit) and signal overlaps. A road speed limit was, and should be, a guideline for the maximum speed it issafe for a typical driver in a typical, well-maintained vehicle* to travel in good conditions (daytime, dry roads, etc) in the absence of other hazards (pedestrians, other traffic, etc). Studies have shown that, in most cases, the speed limit should correspond with the 85th percentile speed (the speed 85% of traffic travels at or below) with prosecutions only for drivers exceeding the 90th percentile speed without authorisation (e.g. emergency services). The speed limit is average over long stretches of road - a road with two long straight stretches with a slow corner in the middle will have just one speed limit, the corner will have a warning sign and at most an advisory limit. The safe maximum speed was/should be/still sometimes is determined by stopping distance and visibility of hazards (with occasional, usually temporary, limits for weak structures). Since roughly the 1990s (in the UK) there has also been a political element to road speed limits, such that a road may have a speed limit lower than is safe because people don't want faster traffic on it for some reason or just want slower traffic in general (in practice this rarely works without physical changes to the road) and rigid, spot enforcement through static speed cameras has eroded the direct link between speed limit and safe maximum speed. (*although the biggest single variable in stopping distance is the road surface, vehicle weight and brake strength are also important) |
|
vincenture
Quiz tryhard, and an advocate for simpler, less complicated rail routes
Posts: 885
|
Post by vincenture on Mar 13, 2021 15:12:22 GMT
I think one of the factors which affected speedlimits is that the S stock is longer than the A stock which the latter was also used when legacy signalling existed.
|
|
Tom
Administrator
Signalfel?
Posts: 4,196 
|
Post by Tom on Mar 13, 2021 15:49:46 GMT
I think one of the factors which affected speedlimits is that the S stock is longer than the A stock which the latter was also used when legacy signalling existed. Not really. We did a lot of work to optimise the signalling for S stock operation, particularly around the Met City area. The difference in length between A stock and S8 stock was very small - the issue was around sightlines from the cab. |
|
|
|
Post by Dstock7080 on Mar 13, 2021 15:50:38 GMT
I think one of the factors which affected speedlimits is that the S stock is longer than the A stock which the latter was also used when legacy signalling existed. 1.87m difference, S8>A8 |
|
vincenture
Quiz tryhard, and an advocate for simpler, less complicated rail routes
Posts: 885
|
Post by vincenture on Mar 13, 2021 15:57:54 GMT
Ah thank you for the insight!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 13, 2021 17:18:46 GMT
What’s the length difference between the S7 and C/D stock?
|
|
|
|
Post by Dstock7080 on Mar 13, 2021 17:52:01 GMT
What’s the length difference between the S7 and C/D stock? S8 133.08m A8 131.20m S7 116.84m D6 110.62m C6 94.06m |
|
|
|
Post by philthetube on Mar 13, 2021 18:58:07 GMT
Thesse numbers amaze me as the A stock would fit in Wembley sidings and the S8 would not.
|
|
Tom
Administrator
Signalfel?
Posts: 4,196
|
Post by Tom on Mar 13, 2021 19:05:34 GMT
Remember it's not just the dimensions of the train, it's the position of the seat and the sightlines from the cab. The field of vision from an S8 cab is much more restricted than from an A60.
|
|
|
|
Post by philthetube on Mar 13, 2021 19:16:13 GMT
Remember it's not just the dimensions of the train, it's the position of the seat and the sightlines from the cab. The field of vision from an S8 cab is much more restricted than from an A60. True, but stopping marks can be placed to the side, as they are at stations so that should not be an issue. |
|
|
|
Post by Dstock7080 on Mar 13, 2021 19:37:01 GMT
Thesse numbers amaze me as the A stock would fit in Wembley sidings and the S8 would not. Yes apologies- figures corrected |
|
|
|
Post by t697 on Mar 13, 2021 21:56:44 GMT
Thesse numbers amaze me as the A stock would fit in Wembley sidings and the S8 would not. Not enough room for modern standards train arrestor and an S8 I seem to recall. |
|
Tom
Administrator
Signalfel?
Posts: 4,196
|
Post by Tom on Mar 13, 2021 22:26:13 GMT
Remember it's not just the dimensions of the train, it's the position of the seat and the sightlines from the cab. The field of vision from an S8 cab is much more restricted than from an A60. True, but stopping marks can be placed to the side, as they are at stations so that should not be an issue. That's true, but it's not just the stopping mark; it's the signal at the other end plus any other signage, etc. There's not a lot you can do when there's no space to extend the siding and the berth is already tight (as no doubt we're going to see on the Piccadilly line in a few years). |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 13, 2021 23:00:38 GMT
South Harrow springs to mind
|
|
Tom
Administrator
Signalfel?
Posts: 4,196
|
Post by Tom on Mar 13, 2021 23:13:22 GMT
At the risk of going off-topic, South Harrow isn't too bad - there's space beyond the buffers to extend and the land ownership goes quite some distance beyond the current sidings - possibly as far as Wood End Road, which is the next overbridge towards Sudbury Hill.
|
|
|
|
Post by jimbo on Mar 20, 2021 3:00:02 GMT
The Government funding deal with TfL expires at the end of March, but it looks like they are pushing to delay a new agreement until after the Mayoral elections in a couple of months. The March TfL Board meeting mentions that the current agreement required them to consider reducing capital investment by up to a third, but that even an agreement like that with Network Rail, with renewals protected but enhancements cut by only 10%, would delay or cancel some long-planned LU frequency enhancements. This must mean the sub-surface lines, where PPP promised resignalling before new trains, leaving service upgrades some ten years late already!
|
|
Colin
Advisor
My preserved fire engine!
Posts: 11,346
|
Post by Colin on Mar 20, 2021 10:40:53 GMT
The 4LM project was fully financed* before Covid hit so isn’t affected by the current financial postering that’s going on.
* the 4LM project has been scaled back in that the west end of the District won’t now be getting CBTC, but part of the reason for the scale back is to keep the 4LM project within its original already funded budget despite the delays it’s experienced thus far.
|
|
|
|
Post by jimbo on Mar 20, 2021 19:30:17 GMT
So there may be money set aside for new signalling, but not for operating costs of service improvements. For those who can still recall the A stock on the Met, they provided nearly half as many seats again as the current S8 trains. Passengers were assured that more frequent services would compensate! Some say that the middle seats of three were rarely used, but there were still a fifth more seats on A stock without those! (A stock 448 seats, S8 stock 306 seats.) Assuming passengers return to at least 80% of prior levels, that will again become a problem.
|
|
|
|
Post by t697 on Mar 20, 2021 22:19:28 GMT
So there may be money set aside for new signalling, but not for operating costs of service improvements. For those who can still recall the A stock on the Met, they provided nearly half as many seats again as the current S8 trains. Passengers were assured that more frequent services would compensate! Some say that the middle seats of three were rarely used, but there were still a fifth more seats on A stock without those! (A stock 448 seats, S8 stock 306 seats.) Assuming passengers return to at least 80% of prior levels, that will again become a problem. A very significant proportion of those Met line passengers who were promised the restoration of the number of seats per hour back in the early 2000s have probably moved house, changed workplaces, retired etc, etc! And LUL hasn't restated the promise for a long time now! |
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,763
|
Post by Chris M on Mar 20, 2021 22:48:40 GMT
Nor can it really be held against LU if the reason the promise isn't kept is because central government slashed its grant and then refused to give it the funds it needed during and following a global pandemic. Indeed, it should be shouting loudly and often about all the funding shortfalls it has and the reasons for them - it is rather notable that the government's review of TfL's financial management has never been published.
|
|
rincew1nd
Administrator
Junior Under-wizzard of quiz
Posts: 10,286
|
Post by rincew1nd on Mar 21, 2021 8:58:37 GMT
For those who can still recall the A stock on the Met, they provided nearly half as many seats again as the current S8 trains. Passengers were assured that more frequent services would compensate! Some say that the middle seats of three were rarely used, but there were still a fifth more seats on A stock without those! (A stock 448 seats, S8 stock 306 seats.) Seats ≠ capacity (I mean the train not the service) |
|
vincenture
Quiz tryhard, and an advocate for simpler, less complicated rail routes
Posts: 885
|
Post by vincenture on Mar 22, 2021 16:44:57 GMT
Just like how we're trying to compare standing space and sitting space. Apple and orange, except this time apple is the subset of orange
|
|
|
|
Post by jimbo on Mar 24, 2021 0:15:20 GMT
Seats may not matter in Zone 1, but become more important for longer journeys out on the Met. They went for a design with more seats for the new tube train design, because there are more weekend and off-peak hours when seating is desirable, than peaks hours when a bare car floor may offer maximum capacity.
|
|
vincenture
Quiz tryhard, and an advocate for simpler, less complicated rail routes
Posts: 885
|
Post by vincenture on Mar 24, 2021 4:00:14 GMT
I suppose they can do some research on which carriages are popular off-peak, which can help determine which carriages they should add more seats
|
|
|
|
Post by alpinejohn on Mar 24, 2021 8:46:25 GMT
So back to topic - apart from cost is there any technical reason why the SSR signalling system could not be progressively installed on the Piccadilly and other deep tube routes to make best use of any new trains they are able to afford?
Replacing conventional signalling with automatic control should allow closer headway between trains and assuming TFL can recruit extra staff and afford extra rolling stock increasing the service frequency is probably the cheapest way to deliver extra seats.
Obviously if TFL cannot afford new rolling stock, I am not sure there is much merit in debates about different styles and layouts of seats in older/new trains, as like it or not, I suspect we are going to be stuck with what we have for a very very long time.
|
|
|
|
Post by goldenarrow on Mar 24, 2021 12:46:47 GMT
So back to topic - apart from cost is there any technical reason why the SSR signalling system could not be progressively installed on the Piccadilly and other deep tube routes to make best use of any new trains they are able to afford? Most if not all of the technical challenges in rolling out Automatic Train Operation (ATO) systems on “brownfield” railway have already been encountered in the previous conversions. Financial security beyond a smattering of months is the single biggest obstacles to line upgrades. Ironically this obsession with cutting costs from Central Government will actually cost somebody more in the long term because patching up the likes of signalling on the Piccadilly is still relying on life expired or technologically obsolete equipment on the ground even it has a shiny new control interface. |
|
|
|
Post by nig on Mar 24, 2021 15:24:00 GMT
I suppose they can do some research on which carriages are popular off-peak, which can help determine which carriages they should add more seats Of course the trains are walkthrough with no doors in-between carragies so passengers could just walk to a vacant seat wouldn't of thought all the seats would fill up off peak |
|
metman
Global Moderator
5056 05/12/1961-23/04/2012 RIP
Posts: 7,421
|
Post by metman on Mar 24, 2021 21:15:12 GMT
The problem with the sort of loadings experienced on the Piccadilly Line for example is in crush loaded conditions it is too difficult to get through to the next car easily.
It is not so bad on the SSLs but can be busy (obviously not at the moment with Covid!)
We will have to see post Covid what the conditions are like.
|
|
|
|
Post by superteacher on Mar 29, 2021 14:35:15 GMT
A few posts are veering off-topic towards train capacity - can we stick to the SSR resignalling please?
|
|
