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the third tunnel

additional tube line to ease rush hour congestion
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i'm sure you've all been rammed onto tubes in the morning heading into city centre, while the ones heading out are empty. and at the end of the day, it's vice versa. this is particularly bad on the northern line.

the idea is to build a 3rd tunnel running along with the current ones. In the morning, trains would run from the city outskirts to the city centre using the 3rd tunnel, so there are two tunnels running in, halving the congestion. the trains using the 3rd tunnel will terminate in the city centre. once the rush hour is over, this tunnel can shut as the tube copes fine for the rest of the day. then in the evening, the 3rd tunnel opens again, taking commuters from the centre to the outskirts.

the only tricky bit about this idea is where to put all the trains that terminate in the city centre. on london underground, trains run (in theory) every 3 mins or so, so over an hour, thats about 20 trains that need to park somewhere in the city centre, underground, until they are used again at the end of the day.

but with a bit of thought and a lot of money it could be done. now we just need red ken to pull his finger out of his arse.

karun, Nov 15 2002

History of the Tube http://www.thetube....tory/milestones.asp
First underground line: 1863, the Metropolitan Railway from Paddington (Bishop's Road) to Farringdon Street.
First tube: 1870, Tower of London to Bermondsey.
Logo introduced: 1913.
First Underground map: 1933. [DrCurry, Oct 04 2004]

History of the Subway http://www.mta.nyc....ct/facts/ffhist.htm
First line: 1904, IRT from City Hall to 145th Street (note the beautiful City Hall station is now disused and inaccessible, lying too close to City Hall itself for governmental comfort in these trying times). [DrCurry, Oct 04 2004]

[link]






       // the only tricky bit about this idea is where to put all the trains that terminate in the city centre. //   

       Whereas constructing all the extra tunnels would be a piece of piss.
sild, Nov 15 2002
  

       correct that, even the underground train park is not such a big thing to do. it will just cost a lot of money. the additional tunnel should not be difficult at all, the engineering behind it has been around for 100 years.
karun, Nov 15 2002
  

       The problem lies less in the engineering, more in the geography, or possibly geometry. There's nowhere left to put the tunnels.
angel, Nov 15 2002
  

       [karun] - I was being sarcastic I'm afraid.
sild, Nov 15 2002
  

       [SLID] - i know u were, but i don't think any of it is such a big job to do, engineering wise. i'm sure there's room down there for an extra tunnel either underneath or next to the existing ones. the train parks would have to be deep underground i reckon.
karun, Nov 15 2002
  

       OK, sorry. Didn't seem like you'd realised from your reply's wording.   

       Admittedly I know very little about excavating tube tunnels underneath very heavily built-up areas, but I would have thought that it is a tremendously large job, engineering wise.
sild, Nov 15 2002
  

       i don't know much about it either, i presume they could just use the same method they used to make the original tunnels.
karun, Nov 15 2002
  

       That worked when I did it.
angel, Nov 15 2002
  

       Actually [karun], I guess you're right :-)   

       It's probably possible to bore these tunnels without worrying too much about what's above - just need to make sure it can take the weight. After all, London was already pretty built up during the construction of the existing tubes.   

       I'm sure it would be prohibitively expensive though. Perhaps Red Ken will start saving up his Congestion Charge earnings and do it, but I doubt it.
sild, Nov 15 2002
  

       Excavating tunnels under London is hard because it's pretty crowded with water mains, cables, the Royal Mail's private underground railway, old pneumatic steam tube delivery systems, Victorian sewers, secret government stuff, priceless Roman remains, etc.
hippo, Nov 15 2002
  

       [hippo], surely that depends on how deep you dig ?
8th of 7, Nov 15 2002
  

       The deeper you dig, the more water mains, cables, etc. you need to negotiate to get to the deepness.
angel, Nov 15 2002
  

       electricity, sewers, watermains, etc were all there when the original tunnels were built (i think!). with the additional technology/engineering developed over the last 100years, it should be a simpler and cheaper job now, than it was back then. i presume they start digging on a clear bit of land on the outskirts, and just work their way into the centre.   

       they are currently planning to extend the eurostar to kings cross, by digging very deep under ground, so it must be possible.   

       as far as cost goes, the eurotunnel was built for nearly £12billion. eurotunnel is 2/3 tunnels which go under the sea for 20+ miles - a massive job. this was a badly run project which ended up costing too much. so lets assume that a few extra tunnels running under london would cost about £1billion. that's about the same as the millenium dome cost.   

       i have never been to the dome, but i was nearly squashed to death on the tube this morning. i know where i'd rather have my money go. pull the finger out ken.
karun, Nov 15 2002
  

       Interestingly enough, most NYC subway lines come equipped with four lines, the inner (or upper or lower) two running express stops only.   

       Furthermore, NYC does this for car lanes on bridges and tunnels.   

       Central London has the advantage of being built on clay, which can be bored through at very low cost, and so many tunnels follow their own paths deep below the surface. Manhattan is mostly on very hard rock (Manhattan Schist, actually) which is extremely difficult to bore, and hence most subway lines follow the streets they were excavated under.
DrCurry, Nov 15 2002
  

       //can be bored through at very low cost//   

       That would be a "low boredom threshold", no?
whimsickle, Nov 15 2002
  

       Hang on, why not just make both existing tunnels go the same way for as long as possible during rush hour?   

       The trains would still all end up at the city center or the outskirts at certain times, but you wouldn't need the extra tunnels. And there would be an annoying gap in the schedule for those people who live in the city center and work in the suburbs..   

       Of course, this logically leads to the even simpler, more convenient and environmentally friendly solution of just not having all the jobs in one tiny area, so people can live close to where they work.
Loris, Nov 15 2002
  

       if both tunnels go the same way then how do people go the other way???
karun, Nov 15 2002
  

       They don't, but its only for the 30 minutes or so of maximum crush. This is what I meant by the 'gap in the schedule'. As noted by you, karun, these trains are empty anyway.
Loris, Nov 15 2002
  

       if all the trains travelled towards one direction, even for 30 mins, there would be congestion for the people travelling the other way. plus all the trains would meet in the middle, so you'd still need to build some underground depot for the trains to go once they reach the centre.
karun, Nov 15 2002
  

       I do seem to have made both of those observations in the my original annotation. And responded to your complaint about congestion before, using your own point that there are no people going the other way.   

       What exactly are you looking for from me?   

       Yes - you still need the train-park. (although it may not need to be as large - you could for example quickly run all the trains back to their starting points a few times during rush-hour.)   

       No - there wouldn't be much congestion for people going the other way, since there are very few people traveling in that direction. These few people would however have to wait for a longer time for their train.   

       I can copy and paste this message again a few times if you want.
Loris, Nov 15 2002
  

       1) Invent a time machine.
2) Go back in time.
3) Imlpement express track system.
4) Stay in the past to make sure everything goes o.k.
snarfyguy, Nov 15 2002
  

       The problem is all the space between cars. Recently I was stuck in rush hour traffic outside Portland, Or , staring at the train tracks alongside the interstate. Once, a car came by. It was packed to the gills. I later found out it was the only car the city owned. If they had more cars, more people could ride.   

       Why not just add cars until congestion is relieved?
bungston, Nov 15 2002
  

       That's fine, as long as the length of all the cars in the train isn't greater than the length of the station platforms.
snarfyguy, Nov 15 2002
  

       //That's fine, as long as the length of all the cars in the train isn't greater than the length of the station platforms.//   

       Actually, on some of London's deep Underground lines, the trains are about half a car length longer than the stations (many of which opened in 1906). Since the end-most door on either end of the train is only for use by the motorman, the fact that the trains overhang the platform does not impede ingress or egress.
supercat, Nov 15 2002
  

       //the additional tunnel should not be difficult at all, the engineering behind it has been around for 100 years.//   

       Literally true. The first deep underground stations were built just before the turn of the century. IIRC the Central Line was the first to open in 1899 or thereabouts; parts of the Picadill and Bakerloo opened in 1906.
supercat, Nov 15 2002
  

       //i don't know much about it either, i presume they could just use the same method they used to make the original tunnels.//   

       Today's safety regulations and liability standards would make that impossible. A number of people were killed or crippled building the underground; such losses may have been acceptable around the turn of the century, but not today.
supercat, Nov 15 2002
  

       //Central London has the advantage of being built on clay, which can be bored through at very low cost, and so many tunnels follow their own paths deep below the surface. Manhattan is mostly on very hard rock (Manhattan Schist, actually) which is extremely difficult to bore, and hence most subway lines follow the streets they were excavated under.//   

       How deep are New York's subways? In London, there are two types of underground trains. The "shallow" underground trains, the first of which opened in 1863, were excavated by digging ditches, building a roof, and then piling dirt back on top. Because of the level of commotion, disruption, and destruction caused by such digging (any buildings in the way had to be demolished and rebuilt) such tunneling was forbidden within the city of London itself. It should be noted that large parts of the District, Circle, and Metropolitan lines are shallow stations produced using this method. It may be further noted that these lines were originally designed for use with steam locomotives; there is a reason the stations are so big and airy!   

       The "deep" tunnel lines first appeared just before the turn of the century. Because they could be dug without distrupting the city above, they were allowed within the city proper. All of the tubes that go within the area delineated by the Circle line are deep tunnel lines.   

       London's deep tunnel stations are really an engineering and architectural marvel. While they are not handicapped-accessible and there is in many cases no good way to make them so, they manage to create a very large amount of usable space in what's actually a very small amount of excavated volume. I forget the exact dimensions of a normal Underground station, but they're really not that big; I think a normal station platform is a tube that's 25' diameter by 400' long or somesuch. The trains themselves travel in tubes that are only 12'6" diameter. Unlike more recent metro systems, the London Underground does not have walkways on many of its tunnels--there's simply no room.
supercat, Nov 15 2002
  

       Several of NYC's subway lines started out as Els (elevated railways), and most of them still are out in the burbs. (As noted above, lacking rights-of-way, the lines were simply built above major roads.)   

       (See links.)
DrCurry, Nov 16 2002
  

       [Loris] - you can copy and paste your solution all you want. it simply does not make sense. of course there are people travelling the other way. if i said trains running the other way were empty, i didn't mean it literally. most people do travel to central london, but many people still need to cross london to get to other parts of the city. eg east to west, or north to south. there are many people i work with who live in north london and work in canary wharf in east london. if all trains run into central london, even for just 30 mins, then it means that for those 30 mins, no-one can CROSS london, so there would be massive congestion in the centre while people wait for the trains to start running to the outskirts again.   

       you can't simply 'quickly run all the trains back to their starting points a few times during rush-hour'... how can you do this when both tunnels are being used to run trains inwards???   

       i don't know if you live in london or have used the tube, but anyone who uses the tube to commute on a daily basis knows this won't work. if the solution was this simple, it would have been investigated or implemented by now.   

       can i just iterate that the reason those trains which run outwards seem 'empty' (i repeat, not literally) is because the frequency of the trains (one every 3-5 mins) ensures that people are kept moving in that direction without congestion. if you stop running those trains for even 30 mins, it wouldn't lead to 'an annoying gap in the schedule' , it would cause chaos for people trying to travel to any part of london not in the centre.
karun, Nov 18 2002
  

       Tidal flow traffic management is already in use for cars. Extending it to subways is fine except that subways in general are not flexible. Better to focus on surface traffic (buses and cars), so that one third of a highway system would switch from outbound to inbound as needed. Use solid barriers to separate these three areas so people don't get confused and drive the wrong way. Use traffic signals (and solid barriers where needed) to change the direction of city streets for rush hour.
horripilation, Nov 18 2002
  

       I am not sure that it would be even possible to run trains in the opposite direction. Are not some of the London lines 'profiled' with a steep descent leaving the station and a slow decelerating climb to the next? The locos might not be powerful enough to run in the other direction.
KiwiJohn, Feb 29 2004
  

       [KiwiJohn] Older tube stations had a slope up just before the platform and a slope down just after (assist braking in, accel out) but other inclines to follow geo. Think about it- no problems either way you run it.   

       Interesting to see [Loris]'s comments - clearly never been in London in the 'rush hour'...which lasts for 3 hours in the morning and 3 in the evening!   

       Scattering work around is also the cause of exessive car usage and a total nightmare - if anything, more should be done so that people live radially from vast centres of employment so they can use highly efficient mass transit systems instead of the nonsensical rats-nest of journeys the car creates.
timbeau, Feb 29 2004
  

       Ok Timbeau, my information came from a 1903 engineering book which said the trains (at that time) were constant power devices and were designed so that even at full power they had only just enough power to reach the top of the incline to the station. There was something like a 15% efficiency saving quoted.   

       If I understood it correctly there was a very steep decline leaving the station to get good acceleration with the weak locos of the time and a slow incline approaching the station. The loco was barely powerful enough to accelerate the train on level track.
KiwiJohn, Mar 01 2004
  

       KiwiJohn: While it would certainly make sense from an energy-efficiency standpoint to have the tunnels decend going either way from a station, I don't see that there's anything to be gained by an assymetric profile. Ignoring for a moment the effects of friction (which are relatively small for a railroad) if the tunnel between stations were 16 feet lower than the station platforms, then a train approaching at 25mph would deccelerate to almost nothing coming into the station as it converted kinetic energy to altitude; it would regain the kinetic energy after leaving the station.   

       While I do not doubt that the early trains were rather anemic compared to today's rolling stock, and that such a slope arrangement would help improve performance, I would think it better for the train to have a flat section of track, prior to the station, on which it could gain enough speed to climb the ramp to the station, than to try to have a long upsloping ramp to the station. If the train is 16 feet below station height travelling 25mph, most of its kinetic energy will be recoverable. If the train has climed up to be only 2 feet below station height and is still travelling 25mph, most of its kinetic energy will not be gravitationally recoverable.   

       Note that modern motors can use dynamic braking to convert kinetic energy into electricity, so the benefits from upsloping and downloping aren't nearly as great.
supercat, Mar 01 2004
  

       Supercat, if I recall correctly what I read the locomotives had only two power settings, stop and go.   

       If the trip time between stations was, say, two minutes, it was going to take so much average horsepower to cover the distance in that time. If the locomotive was not powerful it may have needed to deliver full power for the entire distance just to attain that average.   

       Then of course there was the matter of aerodynamic resistance which must be considerable in a tunnel. Such resistance occurs on some sort of square (cube?) law so to get the average speed high initial acceleration and a lower top speed would be the way to go.   

       Dynamic braking was also mentioned in the same book but with the level of electrical control they had available dynamic braking, where the braking effort was fed back into the supply circuit, caused other trains to lurch forward which was a nuisance if the other train was just coasting into the platform.   

       I would need to spend about three days travelling to reach London but if anyone there could make some observations on the early deep lines?
KiwiJohn, Mar 02 2004
  

       [KiwiJohn] 1903 sounds very close to the opening of the Central Line. These stations certainly had upramps in and downramps out for short sections. You can see the effects at some stations as they have been lengthened slightly and the begining of the decent or end of approach shows. Notting Hill on the Central line is an example.   

       It is also possible to detect the up...flat...down sections as you pass through the disused stations.   

       I doubt if they decended for the entire route in each direction as, if you think about it, even 16 feet per station. The early Central Line with 10 stations would have Liverpool St westbound 160 feet higher than Liverpoot St eastbound, and the tubes making a shallow X.   

       You are right about the feeble, rough motors. Even until 1903 the smallness of the tunnels still forced a separate loco. This was soon replaced as technology rapidly improved.
timbeau, Mar 02 2004
  

       //I doubt if they decended for the entire route in each direction as, if you think about it, even 16 feet per station. The early Central Line with 10 stations would have Liverpool St westbound 160 feet higher than Liverpoot St eastbound, and the tubes making a shallow X.//   

       Why would the effects of the grade be cumulative? The train would go down as it left a station and up on the approach. And 16 feet was to be sure an exaggeration, but the numbers worked out nicely (since it's the vertical distance an object will fall in 1 second). For trains that are underpowered, the steep grades required for a 16-foot vertical displacement would almost certainly be out of the question (if the ramp is 320 feet long, a 16-foot vertical displacement would require a 5% grade).
supercat, Mar 03 2004
  

       OK folks, I found the reference,'Engineering Wonders of the World' published by Thomas Nelson and Sons, 1903. Volume 1 page 310   

       Rather too much to quote in full but the slope leaving the station is 1 in 30 followed by a level section and an inclide of 1 in 60 nearing the next station.   

       An experiment in 1833 demonstrated to shareholders of the London and Birmingham Railway used a clock work model locomotive and a section of dipping line. The demonstration showed a trip could be done in two thirds the time for the same expenditure of power.   

       Greathead (I guess he was the engineer) applied this principle as far as possible on the original section of the City and South London Railway and it was carried through onto subsequent Tube lines.   

       The weird thing is that this description has the trains descending the 1 in 30 under gravity alone accelerating to about 25mph then running along the level section under little power until being braked by the 1 in 60 incline.   

       The book states maximum average speed with minimum cost of energy and braking.
KiwiJohn, Mar 03 2004
  

       Very clever, [KiwiJohn].   

       As for [Karun], the answer for this problem lies not in parallel debottlenecking (expensive and redundant except at peak hours), but in increasing the frequency of cars.   

       Through better control systems (fuzzy logic, etc.) and more powerful engines, you can decrease the spacing and increase the speed. This gives a much higher train frequency and you can run more passengers along the same track.
FloridaManatee, Mar 03 2004
  

       [supercat] //Why would the effects of the grade be cumulative?   

       I think I misunderstood what your '16 feet' concept was...I was imagining a loooong shallow decline. Maybe I was mixing KiwiJohn and your post.   

       Regardless, my last anno mentions what is reality in London - short up and down ramps at stations.   

       [FloridaManitee] hits the main problem in London - Headway is far greater than almost all other systems due to very old signalling and regulations thereof.
timbeau, Mar 03 2004
  
      
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