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Post by Deleted on Mar 30, 2018 15:42:26 GMT
From my understanding the Victoria Line is scheduled for 36tph however, about 95% of the time, when I'm standing on the platforms around peak times the time between one train closing its doors and the next train closing its doors is less than 100seconds, usually between 80-90 seconds.
Please forgive me as I don't know much about operations etc but if say at the southern end of the line, trains are 'squashed up' and running at 80 second intervals, does that mean that at some other section of the line trains are gonna be much more spaced out because surely there's a set amount of trains they put on in accordance with the timetable so if the timetable is written for a train every 100seconds there won't be enough trains for a service every 80seconds across the whole line.
Hope that makes sense and I apologise if this has been asked before.
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Post by will on Mar 30, 2018 16:15:29 GMT
It's a good question, I couldn't say in regards to the timetable but it most likely is due to the uneven loadings on the line stations such as Victoria, Oxford Circus Kings Cross ect. They will be busier and so will have longer dwell time's that will probably be the reason for the 80-90 seconds in a train arriving rather slowly behind at a busy station and in front there may be a 120+ second wait.
The line although simple must be hard to timetable as the line has 33 platforms and I believe in the peaks has 43 trains in service, must be a big challenge at times.
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Post by alpinejohn on Mar 31, 2018 6:39:31 GMT
Ethano - In short the answer to your question must be yes. At any one time trains can only be physically in once place, so if trains are mostly bunched up at one end of the line then without "intervention" they clearly cannot be at the other...
Underlying your question is that perennial problem of bunching - google "bus bunching" for plenty of explanations of the theory. But basically without intervention the same problem of bunching will occur with trains.
At peak hours, dwell time inevitably rises at the busiest stations meaning the train won't be able to depart quite so quickly as the one in front. Those few extra seconds delayed in platform obviously means that a few extra passengers (who would have just missed the train if it actually left on time) will instead manage to get on board just as the doors close. Meanwhile that means that when the train following behind arrives on the same platform it will find slightly fewer passengers waiting to load, so it is ready to depart a few seconds earlier, so the gap between the two trains starts to shrink as they travel along the route.
In an ideal world service control - with the benefit of experience - will know precisely when to ramp up the service frequency just before passenger numbers are expected to rise and thereby ensure trains can maintain a perfectly even spacing. Chaos theory ensures that almost never happens - especially as nowadays on many tube lines pretty much every available train is pressed into service and they are already running at peak frequency throughout the peak hours and often well beyond. Without extra resources to deploy, once services start to bunch up, it is then up to service controllers to hold the following service(s) long enough (typically at a platform) to reinstate the intended gap between services.
Add in all manner of external factors ranging from physical constraints such as the number of terminal platforms available to turn the service, train, track and equipment breakdowns and of course the endless ability of passengers to cause delays and it is a great testament to the staff that TFL can deliver a "Good Service on all lines" quite as often as they do. |
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Post by Deleted on Mar 31, 2018 12:56:23 GMT
Makes sense, thanks. The fact that trains have to wait for each other to pass the junctions in front of terminal stations must make even frequencies even more difficult to achieve
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Post by norbitonflyer on Mar 31, 2018 13:57:10 GMT
Makes sense, thanks. The fact that trains have to wait for each other to pass the junctions in front of terminal stations must make even frequencies even more difficult to achieve I understand departure intervals from the termini are slightly asymmetric in order to allow more time over the scissors for those trains doing so. The intervals are evened up by adjusting dwell times at the next station. |
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Post by will on Mar 31, 2018 15:49:34 GMT
The insane frequency is shown in this video. Towards the end you can see at Kings Cross the trains are slightly bunched with one constantly waiting down the tunnel for the occupying train to move down the line. What a marvel the service is, I can't wait for the NTFL upgrade and hopefully the Central and Piccadilly will be pushed beyond 30tph+.
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Post by banana99 on Mar 31, 2018 19:31:34 GMT
It's a similar phenomenon on the JL. If a train seems too crowded for the time of day, I just wait for the next one. Which is, invariably, far far less loaded.
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Post by superteacher on Mar 31, 2018 19:50:45 GMT
The Central does currently operate a 34 tph frequency in the am peak, although only for 30 mins WB.
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Post by whistlekiller2000 on Mar 31, 2018 19:52:23 GMT
It's a similar phenomenon on the JL. If a train seems too crowded for the time of day, I just wait for the next one. Which is, invariably, far far less loaded. And a few minutes waiting shouldn't ever be regarded as anything other than a mild distraction. Having recently encountered a situation at Stratford with people trying to force themselves onto a hopelessely packed Central Line train when another would be along a couple of minutes later, I had to ask myself, what on earth has happened to the mentality of the London commuting populace? It's gone to hell in a handcart. If it's that important to save a couple of minutes, make sure you fill the kettle at night before you go to bed ready for the morning, make sure you have matching socks available instantly and get your house keys and mobile phone to hand as you exit the house. The phone will help you get killed when you cross the road, running, blindly oblivious, in front of my car on a red crossing light.......  |
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Post by banana99 on Mar 31, 2018 20:05:40 GMT
It's a similar phenomenon on the JL. If a train seems too crowded for the time of day, I just wait for the next one. Which is, invariably, far far less loaded. And a few minutes waiting shouldn't ever be regarded as anything other than a mild distraction. Having recently encountered a situation at Stratford with people trying to force themselves onto a hopelessely packed Central Line train when another would be along a couple of minutes later, I had to ask myself, what on earth has happened to the mentality of the London commuting populace? It's gone to hell in a handcart. If it's that important to save a couple of minutes, make sure you fill the kettle at night before you go to bed ready for the morning, make sure you have matching socks available instantly and get your house keys and mobile phone to hand as you exit the house. The phone will help you get killed when you cross the road, running, blindly oblivious, in front of my car on a red crossing light....... I think a lack of analysis. The hoi polloi just want to get where they are going ASAP, and think that if they don't get on this train then they might not get on the next one etc. If I'm waiting for a JL train for longer than number then chances are it's going to be packed when it arrives at Baker Street SB. Except for 8:30 to 09:00 I'll happily wait for the one up its pipe. Don't want to talk about the JL (for thread drift reasons), but I thought that it (and presumably the VL) have the ability for the "late" train to catch-up to the timetable and therefore even-up the intervals. This doesn't seem to be the case however. |
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Post by superteacher on Mar 31, 2018 20:16:30 GMT
It's a similar phenomenon on the JL. If a train seems too crowded for the time of day, I just wait for the next one. Which is, invariably, far far less loaded. And a few minutes waiting shouldn't ever be regarded as anything other than a mild distraction. Having recently encountered a situation at Stratford with people trying to force themselves onto a hopelessely packed Central Line train when another would be along a couple of minutes later, I had to ask myself, what on earth has happened to the mentality of the London commuting populace? It's gone to hell in a handcart. If it's that important to save a couple of minutes, make sure you fill the kettle at night before you go to bed ready for the morning, make sure you have matching socks available instantly and get your house keys and mobile phone to hand as you exit the house. The phone will help you get killed when you cross the road, running, blindly oblivious, in front of my car on a red crossing light....... I never understand the actions of most passengers. However, I think the reason why people cram onto the first Central line train in the peak is because more often that’s not, the next few are equally rammed. I have let 8 or 9 trains go by without being able to board sometimes! |
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North End
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Post by North End on Mar 31, 2018 22:13:55 GMT
And a few minutes waiting shouldn't ever be regarded as anything other than a mild distraction. Having recently encountered a situation at Stratford with people trying to force themselves onto a hopelessely packed Central Line train when another would be along a couple of minutes later, I had to ask myself, what on earth has happened to the mentality of the London commuting populace? It's gone to hell in a handcart. If it's that important to save a couple of minutes, make sure you fill the kettle at night before you go to bed ready for the morning, make sure you have matching socks available instantly and get your house keys and mobile phone to hand as you exit the house. The phone will help you get killed when you cross the road, running, blindly oblivious, in front of my car on a red crossing light....... I think a lack of analysis. The hoi polloi just want to get where they are going ASAP, and think that if they don't get on this train then they might not get on the next one etc. If I'm waiting for a JL train for longer than number then chances are it's going to be packed when it arrives at Baker Street SB. Except for 8:30 to 09:00 I'll happily wait for the one up its pipe. Don't want to talk about the JL (for thread drift reasons), but I thought that it (and presumably the VL) have the ability for the "late" train to catch-up to the timetable and therefore even-up the intervals. This doesn't seem to be the case however. Not sure about the Vic, but with TBTC there’s little catching up - most of the time the trains go flat out. Indeed in the open sections they actually lose a bit of time thanks to the continued use of a low brake rate. The only recovery is stand time in the timetable and a very few sections where the run time is generous where if running early the train will often get a velocity ceiling imposed, which won’t happen if late. Generally on the Northern in real life the only places where velocity ceilings are generally seen is going southbound on the CX branch, occasionally between Old Street and Angel or KX to Euston northbound, and on the final couple of stops down to Morden. I’d imagine the Jubilee is similar. Of course you can only make up as much time as the train in front allows you to, and a lot depends on dwell times too, which in turn depends on how much of a gap you have in front. A few seconds saved on the inter-station run pales into insignificance if you then go 40 seconds over time in the station because you can’t get a pilot light thanks to people blocking the doors... Contrary to popular belief, with TBTC it’s also possible to make up time by switching to PM. Simply because the driver can drive through some of the glitches which cause unnecessary speed reductions in ATO - and in some places there’s quite a lot of those. Likewise if you have a train which keeps losing the pilot light whilst on the move, the slightly smoother actions of PM often prevent this. One prolonged loss of pilot light in the wrong place will cancel out all your efforts to make up time! The Vic is of course much less prone to this than the Jub and Northern. |
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Post by superteacher on Mar 31, 2018 22:21:09 GMT
Quite amazing that ATO has been in place for 4 years or so and they still haven’t fixed the glitches. Why is it so difficult to simply programme in a higher speed? Southbound leaving Angel it seems to crawl along, not accelerating to a decent speed until after City Road disused station.
EDIT: I’ve moved the thread to the signalling board as the discussion has broadened from just focusing on the Victoria line.
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Post by North End on Mar 31, 2018 22:47:07 GMT
Quite amazing that ATO has been in place for 4 years or so and they still haven’t fixed the glitches. Why is it so difficult to simply programme in a higher speed? Southbound leaving Angel it seems to crawl along, not accelerating to a decent speed until after City Road disused station. EDIT: I’ve moved the thread to the signalling board as the discussion has broadened from just focusing on the Victoria line.There’s various reasons - some are to do with the track, some software issues, and the brake rate issues particularly in the open. My own personal observation is that LU simply doesn’t appear to have the expertise and manpower to get all these issues resolved, and the Thales view is that they have delivered their obligations so that’s that as far as they are concerned. I hear LU have consultants on board with regards to TBTC - one wonders how much that is costing! |
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Post by superteacher on Mar 31, 2018 22:55:43 GMT
Quite amazing that ATO has been in place for 4 years or so and they still haven’t fixed the glitches. Why is it so difficult to simply programme in a higher speed? Southbound leaving Angel it seems to crawl along, not accelerating to a decent speed until after City Road disused station. EDIT: I’ve moved the thread to the signalling board as the discussion has broadened from just focusing on the Victoria line.There’s various reasons - some are to do with the track, some software issues, and the brake rate issues particularly in the open. My own personal observation is that LU simply doesn’t appear to have the expertise and manpower to get all these issues resolved, and the Thales view is that they have delivered their obligations so that’s that as far as they are concerned. I hear LU have consultants on board with regards to TBTC - one wonders how much that is costing! So are we expecting similar issues on the SSR? Thales are installing the TBTC when they haven’t yet sorted out the Northern. The Jubilee doesn’t seem anywhere near as bad. |
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Post by North End on Mar 31, 2018 23:30:25 GMT
There’s various reasons - some are to do with the track, some software issues, and the brake rate issues particularly in the open. My own personal observation is that LU simply doesn’t appear to have the expertise and manpower to get all these issues resolved, and the Thales view is that they have delivered their obligations so that’s that as far as they are concerned. I hear LU have consultants on board with regards to TBTC - one wonders how much that is costing! So are we expecting similar issues on the SSR? Thales are installing the TBTC when they haven’t yet sorted out the Northern. The Jubilee doesn’t seem anywhere near as bad. It’s hard to say. In truth I don’t know the Jubilee apart from in passing, so I can’t say if there’s as many issues under the surface, although my perception would certainly agree that it seems better. As to why this may be, again hard to say, but some possibilities are that the Jubilee learned the hard way and had to put more effort in simply to get the system to deliver the basics, perhaps the operations team on the Jubilee (ie the end users) were more adept at identifying issues, perhaps the Jubilee runs a more demanding timetable so issues are less masked in normal running so there was a greater impetus to identify and sort things, or perhaps the Jubilee is simply a less complex and awkward line whereas Thales were simply more out of their depth dealing with the Northern? It did surprise me how quickly the Northern Line project wrapped up. Indeed the SSR project is following the Northern Line format in many ways, and it’s noticeable how many people involved have found their way over from the Northern to SSR. Again purely personal opinion, but was there a desire to get the Northern wrapped up as quickly as possible in order to press on with SSR as quickly as possible - given SSR’s political sensitivity after LU’s catastrophic flirtation with CityFlo? Sadly the legacy on the Northern is a system that’s simply poor. It can, just about, deliver the current timetable, albeit January’s new timetable is noticeably less smoothly delivered than its predecessor - but struggles to deliver any more than that. The proof is how poorly the railway flows when the job is up the wall - all of a sudden all the little issues show up and bite - and in some cases they bite hard. SSR could well fall into a trap - that once every migration area is commissioned there will always be another one waiting to go and thus be the new focus of attention. Time will tell, but I think the SSR could struggle if there isn’t a lot more attention to detail compared with the Northern. In my view Thales need to up their game and deliver a product less ridden with bugs and glitches, and LU need to much more robustly hold them to that. There’s another pit that’s open for a fall, namely the changes to the trains management structure carried out last year. Along with service control the trains side is the ultimate end user, and there is now a management structure on the trains side which is simply not working well. Any radical change such as a resignalling needs the operations side to be at top of game. Things simply aren’t at that point at the moment with the current structure, and this certainly won’t help. |
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Post by banana99 on Apr 1, 2018 0:52:44 GMT
I thought that I read somewhere (probably on here) that the JL had slack built-in to its timetable (or maybe that the timetable's assumed max speed was (say) 10% less than max linespeed) so that in the case of a particular dwell time being longer than expected, that the train would run at higher than timetabled speeds until it had caught up.
I suppose that running at 97% (say) max speed gets more TPH than (say) 90%, but are we running so need max capacity that a few seconds extra dwell time in a central station leads to "bus bunching"?
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Post by superteacher on Apr 1, 2018 6:21:17 GMT
Some really informed posts North End, thanks. I agree that LU should have held Thales to account. If a software company delivered a bug-ridden package to a multi-national business, they would be made to fix it pretty quickly. |
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Post by 35b on Apr 1, 2018 8:09:34 GMT
Some really informed posts North End, thanks. I agree that LU should have held Thales to account. If a software company delivered a bug-ridden package to a multi-national business, they would be made to fix it pretty quickly. Don’t be quite so sure. If it met the contract spec, is operable, and the customer needs to release resources, then the tolerance levels will rise. Commercial disputes cost serious money and, far more importantly, time and focus. The results are also unpredictable and, if you lose, deeply embarrassing. |
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Post by alpinejohn on Apr 1, 2018 8:36:08 GMT
Beat me to it. If you follow the software analogy there are plenty of examples of people buying into and regularly using "bug riddled software" - I have lost count of how many "updates" have been made to Windows 10 let alone Windows 7, Windows ... Inherently if it reaches the standard required by whatever specs were agreed between supplier and purchaser then the fact it cannot handle other stuff which were not covered in the spec may be unfortunate but probably never going to result in compensation to the customer. If there are evident areas where the spec is not met then legal action is often the worst solution. Almost inevitably both sides then harden their positions and the potential for a practical compromise or just reaching a deal on equitable compensation often goes out the window. Often lawyers are the only real winners.
When it comes to transport systems things become even more murky as the capability of passengers to frustrate best laid plans cannot be overstated hence even something as potentially measurable as 30 trains per hour becomes pretty difficult to prove unless you were to close the whole system for a good few hours and test run it without any of those pesky passengers getting in the way and causing trains to bunch up or come to a complete halt whilst some fool decides to retrieve their iThing from the trackbed. To be honest Londoners do not really appreciate what an asset the tube and TFL is.
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class411
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Post by class411 on Apr 1, 2018 8:42:24 GMT
I thought that I read somewhere (probably on here) that the JL had slack built-in to its timetable (or maybe that the timetable's assumed max speed was (say) 10% less than max linespeed) so that in the case of a particular dwell time being longer than expected, that the train would run at higher than timetabled speeds until it had caught up. I suppose that running at 97% (say) max speed gets more TPH than (say) 90%, but are we running so need max capacity that a few seconds extra dwell time in a central station leads to "bus bunching"? I think this is an excellent point. It's absolute madness to run a system that it is known will partially break from time to time (and, in this case, that includes so many passengers trying to e/ingres that dwell time goes outside allowance), at maximum theoretical throughput. With a railway system, though, if you look at any line as a whole, it may be desirable to accept a certain amount of bunching in the busiest sections and provide the slack elsewhere. Determining the balance to get the highest sustainable throughput is the magic skill. |
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Post by superteacher on Apr 1, 2018 8:45:44 GMT
It’s just annoying that the ATO systems on the Central and Victoria don’t seem to suffer from these issues.
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class411
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Post by class411 on Apr 1, 2018 8:50:29 GMT
Beat me to it. If you follow the software analogy there are plenty of examples of people buying into and regularly using "bug riddled software" - I have lost count of how many "updates" have been made to Windows 10 let alone Windows 7, Windows ... Inherently if it reaches the standard required by whatever specs were agreed between supplier and purchaser then the fact it cannot handle other stuff which were not covered in the spec may be unfortunate but probably never going to result in compensation to the customer. If there are evident areas where the spec is not met then legal action is often the worst solution. Almost inevitably both sides then harden their positions and the potential for a practical compromise or just reaching a deal on equitable compensation often goes out the window. Often lawyers are the only real winners. Staying slightly off topic for a moment, the trouble with consumer software (and particularly Windows) is that just as it's really well bedded down, with most of the important bugs ironed out, they scrap it and foist a new, bug ridden, effort on the general public. Many years ago I christened this the 'kettle' syndrome: We've had electric kettles for many decades now, and it ought to be possible to make them nigh on perfect. What happens in practice, however, is that a manufacturer brings out a kettle, and instead of bringing out a revision that addresses it's faults in a couple of years, brings out a completely new design with its own niggling faults. At least with the railways, they do tend to stick with a major system for many years once it's well 'bedded in' (although not necessarily with every minor element of it.) |
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Post by 35b on Apr 1, 2018 11:02:38 GMT
I thought that I read somewhere (probably on here) that the JL had slack built-in to its timetable (or maybe that the timetable's assumed max speed was (say) 10% less than max linespeed) so that in the case of a particular dwell time being longer than expected, that the train would run at higher than timetabled speeds until it had caught up. I suppose that running at 97% (say) max speed gets more TPH than (say) 90%, but are we running so need max capacity that a few seconds extra dwell time in a central station leads to "bus bunching"? I think this is an excellent point. It's absolute madness to run a system that it is known will partially break from time to time (and, in this case, that includes so many passengers trying to e/ingres that dwell time goes outside allowance), at maximum theoretical throughput. With a railway system, though, if you look at any line as a whole, it may be desirable to accept a certain amount of bunching in the busiest sections and provide the slack elsewhere. Determining the balance to get the highest sustainable throughput is the magic skill. Let’s be honest, the issue with the Tube at peak is that you are running trains that need to stop, let people off & others on, then start again. The only way you could get the flows of the intensity that hits some lines to work is if you treated passengers like parcels, and tipped us onto the trains, then off again through hoppers, a bit like MGR coal trains. That raises some other issues... What interests me is the comparison between my morning peak journeys from a Kings Cross, which are either EB Circle or SB Victoria. Despite the problems tube gauge stock causes with crowds (especially when, like me, you can’t stand upright except in the middle 1/4 of the carriage), the Vic clears crowds far better than the Circle. The frequency is how, and it is a remarkable achievement. |
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rincew1nd
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Post by rincew1nd on Apr 1, 2018 11:14:29 GMT
Many years ago I christened this the 'kettle' syndrome..... <snip> ....(although not necessarily with every minor element of it.) I only spotted this because "April 1st syndrome" has put me on edge. Very droll. And what on earth are you doing to your kettles? I've had the same one for eleven years, and my only niggle with it is that I have to fill it up, and make the tea! HWMBO says I should just buy a Teasmade. |
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Post by MoreToJack on Apr 1, 2018 13:31:58 GMT
Many years ago I christened this the 'kettle' syndrome..... <snip> ....(although not necessarily with every minor element of it.) I only spotted this because "April 1st syndrome" has put me on edge. Very droll. And what on earth are you doing to your kettles? I've had the same one for eleven years, and my only niggle with it is that I have to fill it up, and make the tea! HWMBO says I should just buy a Teasmade. Get a ZipTap. Your kettle is a pain, and you can't even make Proper Railway Tea. 🙄😘 |
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Post by rincew1nd on Apr 1, 2018 13:59:28 GMT
Nothing wrong with my kettle, the fridge however.....
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class411
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Post by class411 on Apr 1, 2018 14:10:25 GMT
Many years ago I christened this the 'kettle' syndrome..... <snip> ....(although not necessarily with every minor element of it.) I only spotted this because "April 1st syndrome" has put me on edge. Very droll. I don't suppose anyone will believe me but I swear to God that that was unintentional. It's not that they break (well, one did but everyone who had the same model had the same problem: the lid mechanism failed after a couple of years). No, the problem was/is that every different type kettle has at least one niggle (switch/lid/spout/water gauge, etc.), and yet instead of instead of each manufacturer fixing the niggle, they go in for a complete redesign every couple of years, and never manage to get it 100% right. |
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