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Post by Deleted on Aug 30, 2010 3:58:36 GMT
One of the capacity restrictions of the Victoria Line is known to be the scissors crossover at Brixton. Despite being a slick operation, it still limits the line to 28.5tph, although 33tph post upgrade has been quoted.
Here is a link to a video of Tokyo terminus of the JR Chuo Rapid Line, an outer suburban rail line, one of Japan's busiest and most frequent. It is timetabled at around 29-30tph in the peak.
This terminus a typical 2 track terminus with scissors crossover (and not much of an overrun). The trains are 200m long, which increases crossover transition time. In the video, trains can be seen departing at an average of 1:46 headway (2:04, 1:30, 2:05, 1:26). This impressive average headway can be put down to trains departing at uneven headways, which are probably evened out at the next station. It seems that as soon as the track ahead of the train in the outbound track is clear approx. 1:00 after the previous departure, the departure tune is played, and the train departs around 1:30. For trains waiting to depart from the inbound platform, the departure tune is not played until after the crossover is clear at about 1:40, which results in a headway of around 2:05.
So maybe if the new Victoria Line signalling allows for VE2 at Brixton to clear faster after a departure from the adjacent platform (it currently seems to take around 1:36 to clear), then a significant increase in frequency could theoretically be possible.
Another option to increase capacity at Brixton, could be to start the door closing procedure for a train at VE4 before the signal is green, rather than afterwards.
Any thoughts?
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Phil
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Post by Phil on Aug 30, 2010 6:53:33 GMT
It's the uneven headways that keep it sharp - why have we got to the stage over here where the planners hate them, thinking the slighest uneven headway results in a huge fall in customers??
And getting the doors closed before the crew get the green only works if you can GUARANTEE the stick will change to the second. And it does in Japan, but over here.......??
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mrfs42
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Post by mrfs42 on Aug 30, 2010 8:48:15 GMT
I suspect the acceleration rates are slightly higher than the Vic.
Interesting watching the opposing route being set across the scissors - that seemed to take slightly longer than I was expecting: perhaps the approach locking circuitry extends to the block joint beyond the departing route. I shall have to watch it again (several times!)
TVM for the pointer.
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Post by Deleted on Aug 30, 2010 10:26:35 GMT
It's the uneven headways that keep it sharp - why have we got to the stage over here where the planners hate them, thinking the slighest uneven headway results in a huge fall in customers?? The thing is, even if trains depart from Brixton at regular intervals, they can then end with uneven intervals at Stockwell depending on how many passengers are transferring. With the regulation possibilities of modern signalling, I'm sure that irregular terminus departures can be ironed out by a few stops down the line. It might add 30secs to journey time, but for a few extra tph it could be worth it. It's not done in Japan - which makes the frequency in the video even more impressive. However on Hong Kong MTR I've observed the driver starting the door closing process when the rear of the incoming train is in the middle of the crossover. Out of interest, on the lines such as the Central (and ?? now the Jubilee) where there is a countdown timer to departure, does the timer still countdown when there is red signal, or will it only countdown when the signal is clear? |
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Post by Chris M on Aug 30, 2010 10:41:09 GMT
Regarding the uneven headways, from a customer perspective I don't think it matters at a turn-up-and-go frequency. Especially if the difference between the headways is less than about 5 minutes. You don't even need to advertise the uneven headway, just say something like "trains at least every X minutes" where X is the larger of the headways (or "every X+n minutes" if you want to give some flexibility).
When you drop below about 4-5 tph though it does matter, as people start planning their journeys around specific trains. Then a "clockface" schedule is easier to remember and gives the impression of a more frequent and reliable (and thus more attractive) service.
If you're talking of uneven headways on the order of 30 seconds difference, then I doubt most people would even notice.
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Post by Deleted on Aug 30, 2010 12:40:28 GMT
Another option to increase capacity at Brixton, could be to start the door closing procedure for a train at VE4 before the signal is green, rather than afterwards. By doing this you are increasing the chances of a SPAD occurring. |
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mrfs42
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Post by mrfs42 on Aug 30, 2010 13:21:25 GMT
Another option to increase capacity at Brixton, could be to start the door closing procedure for a train at VE4 before the signal is green, rather than afterwards. By doing this you are increasing the chances of a SPAD occurring. Thereby hangs a tale or two. I'm sure the absolute paranoia that has been created in the british railway industry about SPADs is actually in some cases far more detrimental that would normally be thought. Let's face it - it would be a low-speed SPAD and unless there was a very peculiar chain of circumstances the move would have come well to a stand. Of course, it would bring the entire job to a stand these days - even if it were a 'technical' SPAD. Yes, signals are there to be obeyed, and what has been lost sight of is that these signals will be over-run no matter what mitigation plans you put in. In all honesty, is it that grevious a sin to start up against a red and then realise before being tripped or actually passing the signal? I do wonder if some quarters worry too much about the possibility of a SPAD, rather than the actuality! Note that I'm not particularly suggesting that SPADs don't matter, but perhaps there is too much emphasis on the prevention rather than the cause these days? |
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Post by North End on Aug 30, 2010 13:39:46 GMT
By doing this you are increasing the chances of a SPAD occurring. Thereby hangs a tale or two. I'm sure the absolute paranoia that has been created in the british railway industry about SPADs is actually in some cases far more detrimental that would normally be thought. Let's face it - it would be a low-speed SPAD and unless there was a very peculiar chain of circumstances the move would have come well to a stand. Of course, it would bring the entire job to a stand these days - even if it were a 'technical' SPAD. Yes, signals are there to be obeyed, and what has been lost sight of is that these signals will be over-run no matter what mitigation plans you put in. In all honesty, is it that grevious a sin to start up against a red and then realise before being tripped or actually passing the signal? I do wonder if some quarters worry too much about the possibility of a SPAD, rather than the actuality! Note that I'm not particularly suggesting that SPADs don't matter, but perhaps there is too much emphasis on the prevention rather than the cause these days? Like the minority of drivers who drive artificially slowly because they think this reduces their likelihood of having a SPAD. What it actually does is greatly increase the chance of the train behind having a SPAD because more red signals are created, often in unusual places. |
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Post by andypurk on Aug 30, 2010 13:43:15 GMT
Another option to increase capacity at Brixton, could be to start the door closing procedure for a train at VE4 before the signal is green, rather than afterwards. By doing this you are increasing the chances of a SPAD occurring. How does it increase the chances of a SPAD on the Victoria line occurring, where the trains are automatically driven? |
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Post by metman on Aug 30, 2010 22:15:40 GMT
Good point. Great video btw. Makes Elephant and Castle look a bit tame!!
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Post by djlynch on Aug 31, 2010 0:11:23 GMT
It's the uneven headways that keep it sharp - why have we got to the stage over here where the planners hate them, thinking the slighest uneven headway results in a huge fall in customers?? Show me someone who gets scared away by headways varying between 1½ and 2 minutes, and I will show you an easily frightened person with a very good sense of time. Although it must be said that I know quite a few people who cope just fine with multiple clockface services overlapping. The service between Glasgow Central and the station in the town where my father grew up is 6 tph, but you have three trains leaving Glasgow within 12 minutes followed by a gap of 18 minutes because it's really 3 services at 2 tph each. |
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Post by Deleted on Sept 1, 2010 7:15:34 GMT
Another option to increase capacity at Brixton, could be to start the door closing procedure for a train at VE4 before the signal is green, rather than afterwards. By doing this you are increasing the chances of a SPAD occurring. How can you SPAD an automatic train at a starter signal? If the signal is red, and you hit the start button, the train will not move! |
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Post by singaporesam on Sept 1, 2010 14:13:04 GMT
It's the uneven headways that keep it sharp - why have we got to the stage over here where the planners hate them, thinking the slighest uneven headway results in a huge fall in customers?? The thing is, even if trains depart from Brixton at regular intervals, they can then end with uneven intervals at Stockwell depending on how many passengers are transferring. With the regulation possibilities of modern signalling, I'm sure that irregular terminus departures can be ironed out by a few stops down the line. It might add 30secs to journey time, but for a few extra tph it could be worth it. It's not done in Japan - which makes the frequency in the video even more impressive. However on Hong Kong MTR I've observed the driver starting the door closing process when the rear of the incoming train is in the middle of the crossover. Out of interest, on the lines such as the Central (and ?? now the Jubilee) where there is a countdown timer to departure, does the timer still countdown when there is red signal, or will it only countdown when the signal is clear? Central on the Tseun Wan line in HK is impressive and is the example most often quoted as having high capacity. I seem to recall one on Skytrain in Vancouver. On the NSEW Line in Singapore we have one at Changi, but that is not used anywhere near its capacity. P way guys hate them. |
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Post by Deleted on Sept 1, 2010 19:50:46 GMT
Certainly some impressive turnrounds there... looks like a 'Step Back' procedure is carried out!
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Post by Deleted on Sept 1, 2010 19:54:00 GMT
Certainly some impressive turnrounds there... looks like a 'Step Back' procedure is carried out! Look at that first train coming in - looks like the driver is already in the cab! Not much of a Moorgate protection there either by the looks of it |
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Post by Deleted on Sept 1, 2010 20:28:24 GMT
Could be the conductor!
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metman
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Post by metman on Sept 1, 2010 20:54:36 GMT
Think that's correct.
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Post by Deleted on Sept 2, 2010 11:12:11 GMT
Certainly some impressive turnrounds there... looks like a 'Step Back' procedure is carried out! Look at that first train coming in - looks like the driver is already in the cab! Not much of a Moorgate protection there either by the looks of it There is a short overrun (and large drop after the overrun!). As far as I'm aware the Chuo Line has quite advanced signalling and ATP, which I can only hope would prevent an overrun. The Chuo Line has both a driver and conductor. The thing is, even if trains depart from Brixton at regular intervals, they can then end with uneven intervals at Stockwell depending on how many passengers are transferring. With the regulation possibilities of modern signalling, I'm sure that irregular terminus departures can be ironed out by a few stops down the line. It might add 30secs to journey time, but for a few extra tph it could be worth it. It's not done in Japan - which makes the frequency in the video even more impressive. However on Hong Kong MTR I've observed the driver starting the door closing process when the rear of the incoming train is in the middle of the crossover. Out of interest, on the lines such as the Central (and ?? now the Jubilee) where there is a countdown timer to departure, does the timer still countdown when there is red signal, or will it only countdown when the signal is clear? Central on the Tseun Wan line in HK is impressive and is the example most often quoted as having high capacity. I seem to recall one on Skytrain in Vancouver. On the NSEW Line in Singapore we have one at Changi, but that is not used anywhere near its capacity. P way guys hate them. Hong Kong MTR has two 2 tracks/scissors crossover termini that handle 28tph, and one that handles 30tph. Trains are approx 182m long. |
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Post by Colin D on Sept 2, 2010 11:42:56 GMT
Certainly some impressive turnrounds there... looks like a 'Step Back' procedure is carried out! Look at that first train coming in - looks like the driver is already in the cab! I think in Toronto both crew are drivers, one operates the doors in one direction and drives in the other, which would save time changing ends or stepping back. |
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Post by Deleted on Sept 15, 2010 2:20:19 GMT
Look at that first train coming in - looks like the driver is already in the cab! I think in Toronto both crew are drivers, one operates the doors in one direction and drives in the other, which would save time changing ends or stepping back. That is correct IIRC. It allows faster turnarouns or something like that, since they don't have to run up/down the platform... |
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Post by Deleted on Sept 15, 2010 2:25:32 GMT
Hong Kong MTR has two 2 tracks/scissors crossover termini that handle 28tph, and one that handles 30tph. Trains are approx 182m long. Which termini are they? Central and...? BTW while Changi has excess capacity, Jurong East need more during peaks, having only one platform to reverse in. |
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Post by Deleted on Sept 15, 2010 21:54:30 GMT
It's perfectly obvious.
First, you deliver the power supply overhead by pantograph rather than third rail, and then (this is the really clever bit) you paint orange Go Faster stripes on the trains.
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Post by Deleted on Sept 16, 2010 0:29:04 GMT
The bit at 1:21 gets me.....the points throwing right in front of a train. This railway looks a very different beast to the one I work on.
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Post by Deleted on Sept 16, 2010 10:46:26 GMT
Central on the Tseun Wan line in HK is impressive and is the example most often quoted as having high capacity. I seem to recall one on Skytrain in Vancouver. On the NSEW Line in Singapore we have one at Changi, but that is not used anywhere near its capacity. P way guys hate them. Hong Kong MTR has two 2 tracks/scissors crossover termini that handle 28tph, and one that handles 30tph. Trains are approx 182m long. Which termini are they? Central and...? [/quote] Central & Yau Ma Tei - 126sec headways Chai Wan - 120sec headways Po Lam used to handle 158sec headways with just one platform! The bit at 1:21 gets me.....the points throwing right in front of a train. This railway looks a very different beast to the one I work on. The signalling on the Chuo Line is quite advanced and allows a slow moving train to get pretty close to the junction which is set against it. It's not too different to moving block signalling systems such as the DLR allow trains to close in to around 40-50m of an "obstruction". Also if a train can approach a buffer stop under ATO/ATP slowly, is there any reason why it can't slowly approach a junction set against it? |
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Post by DrOne on Sept 16, 2010 11:27:06 GMT
Brilliant. Thanks for sharing stephenk.
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Post by Deleted on Sept 16, 2010 12:58:28 GMT
OMG under 3min!! That's fast...
BTW StephenK, why is Po Lam a "used to"? Have they built a new platform? Or is it because trains are being diverted to the other branch?
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Post by Deleted on Sept 16, 2010 23:21:26 GMT
Also if a train can approach a buffer stop under ATO/ATP slowly, is there any reason why it can't slowly approach a junction set against it? That's a good way of putting it! Nice one. Thing is, it's a totally different ball game from when I want a train to be close to points before throwing them - it's a case of train comes along, train gets all on track circuit, train stops, wait for little backlock release light (or put lever to mid and wait for the click or the buzz) to come up, put the lever back in the frame behind the train, move points, clear next signal.....just seems a total world away! |
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