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Old December 1st, 2009, 04:08 PM   #3881
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I've had a close look at this, and casting my mind back to the line topography from my distant days as a Northern Line driver, I think you're right and here's why...

Moorgate is quite wide, so wide enough to accommodate two tracks side by side without encroaching under property, however Prince's Street is very narrow and therefore below this street the tracks would have to be stacked above one another. When you leave Moorgate southbound, you descend quite a steep gradient before the sharp turn to the left where Moorgate becomes Prince's Street. There's no perceptable uphill gradient approaching Moorgate Northbound, so it's clear to me that the Southbound is descending leaving Moorgate in order to run below the Northbound under Prince's Street. At the southern end of Prince's Street the two lines can again diverge and return to the same level, whilst doing so one needs to curve sharper than the other at the top end of Lombard Street before the platforms under King William Street, and it's logical that the sharper curve is reserved for the slower speed track, which is the Northbound because trains are accelerating on the level rather than decelerating up a gradient into the platform.

This difference in curve radii would explain why it was decided it was better for the Northbound and Southbound to switch round through Bank.

Probably.
If the cellars of houses and buildings in the olden days went quite far under the road there might only be the opportunity to have one tunnel at one level otherwise easements would have to be paid even if the road above was wide! This was a particular problem in the City and around Piccadilly. The obvious solution is to put one tunnel above another, but this will mean sometimes it is necessary to swap the SB and NB tunnels over for short sections when they are alongside each other (which is preferable at stations). AFAIK north of Moorgate station the Northern tunnels are on top of each other and the Northern city (NR into Moorgate) ones on top of each each other and the lower Northern tunnels. That's 4 tunnels in vertical alignment!
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Old December 1st, 2009, 06:19 PM   #3882
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what about the geologic formation (strata) or is the bed indeed just clay, coz I'm wondering if the water table there might be as to why?

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Old December 1st, 2009, 08:06 PM   #3883
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what about the geologic formation (strata) or is the bed indeed just clay, coz I'm wondering if the water table there might be as to why?
Wherever possible Tubes were built through London Clay. They're of course well below the water table, but London Clay is impervious to water so it's an ideal medium to tunnel through as it's soft and doesn't let water in.
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Old December 1st, 2009, 08:10 PM   #3884
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If the cellars of houses and buildings in the olden days went quite far under the road there might only be the opportunity to have one tunnel at one level otherwise easements would have to be paid even if the road above was wide! This was a particular problem in the City and around Piccadilly. The obvious solution is to put one tunnel above another, but this will mean sometimes it is necessary to swap the SB and NB tunnels over for short sections when they are alongside each other (which is preferable at stations). AFAIK north of Moorgate station the Northern tunnels are on top of each other and the Northern city (NR into Moorgate) ones on top of each each other and the lower Northern tunnels. That's 4 tunnels in vertical alignment!
Moorgate would certainly have been widened historically so that doesn't surprise me actually, I guess it would not have been uncommon when narrow City roads were widened that cellars were left as they were and therefore extend out under the new roadway.

I know the GN&CR is above the Northern Line between Old Street and Moorgate, but I don't think the four tracks are vertically stacked... sounds a little improbable. There would have to be some silly gradients between Old Street and Moorgate to allow for this, which I can't recall.
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Old December 1st, 2009, 08:41 PM   #3885
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I happened to have just read about the Northern city Lothbury extension in London's lost tubes. I keep re-reading that book! 4 tunnels on top of each other does sound crazy but that's what i read!

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what about the geologic formation (strata) or is the bed indeed just clay, coz I'm wondering if the water table there might be as to why?
Where the bed is clay it is not water-bearing like gravel beds or solid rock (none of which exists below London AFAIK). AFAIK the clay goes quite deep in most places north of the river, certainly through the City, though the deeper the tunnels the more cost whatever the geological conditions. Tunnelling through gravel beds has been too costly particularly in south London as it is necessary to tunnel using compressed air, which has been possible since the 1890's and only recently come down in cost.
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Old December 2nd, 2009, 01:55 AM   #3886
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When the Circle line is suspended (as it was today), where do all the trains go? Are they all diverted to Hammersmith and Wimbledon?
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Old December 2nd, 2009, 08:37 PM   #3887
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When the Circle line is suspended (as it was today), where do all the trains go? Are they all diverted to Hammersmith and Wimbledon?
They'll be chucked into the sidings at Edgware Road (x 2), Farringdon (x 3), Triangle Sidings (High Street Kensington, x 5), with others diverted to H&C Line destinations. They wouldn't be diverted to Wimbledon, as Circle Line drivers don't know the route beyond High Street Kensington.
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Old December 2nd, 2009, 11:24 PM   #3888
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I happened to have just read about the Northern city Lothbury extension in London's lost tubes. I keep re-reading that book! 4 tunnels on top of each other does sound crazy but that's what i read!



Where the bed is clay it is not water-bearing like gravel beds or solid rock (none of which exists below London AFAIK). AFAIK the clay goes quite deep in most places north of the river, certainly through the City, though the deeper the tunnels the more cost whatever the geological conditions. Tunnelling through gravel beds has been too costly particularly in south London as it is necessary to tunnel using compressed air, which has been possible since the 1890's and only recently come down in cost.
Then I wonder if the corridor additionally accommodates a buried river and other (old) conduits like telecom ones...
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Old December 3rd, 2009, 08:13 PM   #3889
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Then I wonder if the corridor additionally accommodates a buried river and other (old) conduits like telecom ones...
I'd guess 100 ft of clay will accommodate 4 tunnels and enough width without paying easements to property owners for one tunnel with the occasional widened section to allow tunnels to go level, swap over etc.

Sewers (assuming the Moorgate street wasn't on the main Bazalgette sewer system) and especially telecommunications would likely have come later, when easements didn't have to be paid and tunnels only had to avoid real obstacles in their way.
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Old December 3rd, 2009, 10:19 PM   #3890
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I wondered out loud coz that's what they did here late 1800s (less any metro), plus we weren't as wealthy here (still aren't) as you are over there...assuming's no good; it'd be better to research it.
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Old December 3rd, 2009, 10:41 PM   #3891
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Then I wonder if the corridor additionally accommodates a buried river and other (old) conduits like telecom ones...
The Northern Line crosses under the culverted River Walbrook around about Bank station, but the are not parallel. The Walbrook rose from springs in Finsbury and ran directly through the centre of The City (it still runs under the Bank of England), entering The Thames near Cannon Street bridge.

Subterranean rivers in London:



Walbrook sewer under the bank of England:

[IMG]http://i47.************/am9lro.jpg[/IMG]
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Old December 5th, 2009, 12:33 AM   #3892
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Thanks for the offer Tubeman.

2) Why does it take London Underground (and National Rail for that matter) so long to build extensions, when Madrid pulls them off cheaper and faster?

Mainly attitude and culture I think.
http://mindroutes.blogspot.com/2008/...rid-metro.html
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Old December 5th, 2009, 12:38 AM   #3893
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Tubeman, did you prefer driving in tunnel or on the surface?
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Old December 5th, 2009, 08:28 AM   #3894
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Have you ever seen anything in one of the tunnels? Like a ghost... or a homeless person?
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Old December 5th, 2009, 12:45 PM   #3895
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Tubeman, did you prefer driving in tunnel or on the surface?
Definitely surface, that's why I moved from the Northern to the District.

Single bore Tube tunnel is utterly monotonous, at least on the tunnel sections of subsurface you can wave at oncoming drivers, you can't even do that on Tubes. I'd often forget where I was on the Northern, especially between Clapham South and Morden because every station is on the same side and looks the same. At least on the old Hampstead Tube and City & South London sections, there was variety regarding the stations so it would generally register where the last stop was. There are more features in terms of distinctive twists & turns too, plus some funny little gradients, most notably two 'dips' between Angel and King's Cross, and one between Euston and King's Cross.

Open section can be a pleasure on a nice day, I used to love driving down to Wimbledon or Richmond with the cab doors open in the Summer, crossing the Thames, waving to pubgoers by the river, it's a nice feeling. The District had nice variety too, in that there were 2 stocks to drive (C and D) which are very different and a number of different branches / routes.

How drivers cope on the Victoria Line I'll never know.
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Old December 5th, 2009, 12:48 PM   #3896
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Have you ever seen anything in one of the tunnels? Like a ghost... or a homeless person?
No... sorry!

I once was spooked on the Northern Line because I was bombing along and saw something in the tunnel in the distance which was moving around, I slowed down and as I got closer it registered it was a bunch of helium balloons which had blown into the tunnel... They did look like a person walking down the tunnel toward me at first sight.
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Old December 5th, 2009, 02:33 PM   #3897
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Definitely surface, that's why I moved from the Northern to the District.

Single bore Tube tunnel is utterly monotonous, at least on the tunnel sections of subsurface you can wave at oncoming drivers, you can't even do that on Tubes. I'd often forget where I was on the Northern, especially between Clapham South and Morden because every station is on the same side and looks the same. At least on the old Hampstead Tube and City & South London sections, there was variety regarding the stations so it would generally register where the last stop was. There are more features in terms of distinctive twists & turns too, plus some funny little gradients, most notably two 'dips' between Angel and King's Cross, and one between Euston and King's Cross.

Open section can be a pleasure on a nice day, I used to love driving down to Wimbledon or Richmond with the cab doors open in the Summer, crossing the Thames, waving to pubgoers by the river, it's a nice feeling. The District had nice variety too, in that there were 2 stocks to drive (C and D) which are very different and a number of different branches / routes.

How drivers cope on the Victoria Line I'll never know.
Yes, but surely the W&C is worse!! You've put an end to my tube driver ambitions. Thanks.
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Old December 5th, 2009, 03:05 PM   #3898
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I listened to a programme on the BBC recently about the Moorgate disaster. Apparently there are various theories as to the cause. Any bias one way or the other?
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Old December 5th, 2009, 08:26 PM   #3899
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Yes, but surely the W&C is worse!! You've put an end to my tube driver ambitions. Thanks.
W&C is worked by Central Line drivers from Leytonstone Depot, so no-one is permanently on W&C duties... That's why I picked on the Vic Line, as those drivers are literally bombing up and down Tube and nothing else day in, day out... although if they're lucky they get to go in or out of Northumberland Park Depot and so see some daylight.

Nowt wrong with being a driver, I loved it for about 2 years then began to get bored, when Duty Manager came up after about 3 years it was timely. It's a great job if you don't mind solitude; £40k and the sort of job where the second you step out of the cab at the end of the day, you're absolved of all responsibility or care... A BIG contrast to my current roles in management, where you're effectively on duty 24/7 and have an eternal 'to do' list.
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Old December 5th, 2009, 08:41 PM   #3900
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I listened to a programme on the BBC recently about the Moorgate disaster. Apparently there are various theories as to the cause. Any bias one way or the other?
I personally think the guy was in some sort of daydream / seizure. There was too much evidence to point to it not being suicide, and he was sat bolt upright when the train crashed and was still alive at the point of impact.

Through sheer familiarity and repetition it's easy to slip into 'autopilot' as a Tube driver where you literally do largely shut down brain-wise and yet perform very complex physical actions to stop a train on a very precise spot. You're almost not conscious, and yet performing the role with aplomb and flawlessly.

Sometimes, this state of autopilot slips deeper into a weird stupour where you do make mistakes, and this is where I think the Moorgate driver was mentally. I did it myself once; you leave West Ham eastbound and off in the distance all the signals controlling Plaistow are always all red. There's a particular spot between West ham and Plaistow where as you pass it, all of a sudden all of the signals controlling Plaistow's Bay road and crossover turn green and you 'get the road' into Plaistow eastbound platform. 95 times out of a hundred as you pass that spot, all the red signals turn green and so you get into the habit of leaving West ham in 'full parallel' (all motors drawing full power), anticipating the signals to all turn green. One evening I left West Ham in 'full parallel' and as usual could see the signals for Plaistow all red in the distance. I remained motoring up until the point where all the signals should turn green and they didn't, but it didn't register. I was totally awake and totally alert, but I remained motoring toward a red signal. It literally didn't register until I was about a car's length from the red signal and sailed 4 cars past it just as a H&C Line train was coming out of Plaistow Bay road (I must have scared the shit out of them!). So, despite being awake and alert I was able to drive full pelt toward a red signal which was protecting a train heading toward me in the opposite direction... I just literally slipped into some sort of waking coma. This is what I think happened at Moorgate: the driver just had one of these bizarre waking comas where he remained in 'full parallel' and didn't snap out of it.
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