In article .com,
(TheOneKEA) wrote:

Paul Corfield wrote:
On Sat, 26 Nov 2005 21:38 +0000 (GMT Standard Time),
(Colin Rosenstiel) wrote:

[Victoria line - Victoria line layout]

Victoria was built with a scissors crossover at the North end,
wasn;t it? Why on earth did they remove it?

I think you're right. No idea why they were removed.

Because Victoria has got a second scissors crossover south of the
station and two central reversing sidings. When the service is
buggered from Victoria to Brixton it can be used to reverse the
southbound service. The original scissors crossover (just like the one
that used to be at Highbury) is thus redundant.

http://www.trainweb.org/tubeprune/Vi...en%20Pk-rm.gif refers.

I appreciate it's redundant, but then it turns out not to be so on
occasion when other equipment fails. Some redundancy makes it easier to
cope with failures.

My surprise is that the facility was removed having been installed. It
would have cost very little just to leave it there.

--
Colin Rosenstiel

Colin Rosenstiel wrote:
In article .com,
(TheOneKEA) wrote:

http://www.trainweb.org/tubeprune/Vi...en%20Pk-rm.gif refers.

I appreciate it's redundant, but then it turns out not to be so on
occasion when other equipment fails. Some redundancy makes it easier to
cope with failures.

True, but in theory the simultaneous failure of the signalling in
Victoria South Sidings and the trailing crossover north of the station
should not happen. The fact that it did does not mean that having a
scissors crossover in position would have changed anything.


My surprise is that the facility was removed having been installed. It
would have cost very little just to leave it there.

Not necessarily - if that were the case the scissors crossover west of
Liverpool Street (Central) would not have been simplified either, and
yet it was - and Liverpool Street has the same arrangement as Victoria.

In article , Tom
Anderson writes
And can you reverse in both directions at Victoria, Warren Street and
Seven Sisters? Again, the tracks would allow it, but what about the
signalling?

From the diagram that Tubeprune posted, you can do it at Victoria: for
north-to-south, run north out of the platform to behind VF16, then
reverse into the southbound platform.

Going to his site: you can do it at Warren Street. For north-to-south,
run north out of the platform to behind VG8, then reverse into the
southbound platform. For south-to-north, simply run directly over the
crossover when given the road by VG4.

Seven Sisters: you can only do south-to-north from platform 4. Either:
* no route indicator at VL6, forward to VL7, change ends, signal VL20
takes you over the scissors to VL19 which protects the entrance to
the southbound platform.
* right-hand indicator at VL6, forward over the crossover to a fixed red
light behind VL22A, change ends, signals VL22A and VL22B take you
straight to VL19.

North-to-south is harder but possible: into platform 5, change ends,
signal VL8 takes you on to the depot exit road, over the scissors, and
up to VL7. Change ends again, pass VL20 at danger with permission[*]
and run forward to the fixed red light at the end of platform 4. Change
ends a final time and depart normally (VL6 with left-hand junction
indicator).
[*] VL20 is not shown as having a junction indicator. I'm assuming,
therefore, that the only route from it leads to VL19. It could be,
however, that the only route leads to platform 4. In which case the
first of my south-to-north cases doesn't apply and north-to-south
involves all signalled moves.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
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In article , I wrote:
Seven Sisters: you can only do south-to-north from platform 4. Either:

Checking an old rulebook, I have some amendments to make:

* no route indicator at VL6, forward to VL7, change ends, signal VL20
takes you over the scissors to VL19 which protects the entrance to
the southbound platform.
* right-hand indicator at VL6, forward over the crossover to a fixed red
light behind VL22A, change ends, signals VL22A and VL22B take you
straight to VL19.

This is correct, except that the fixed red is placed so that VL22A will
be mid-train and can be ignored.

North-to-south is harder but possible: into platform 5, change ends,
signal VL8 takes you on to the depot exit road, over the scissors, and
up to VL7.

This is wrong. VL8 doesn't have a junction indicator, but nevertheless
can clear for two routes: either to VL7 on the depot entry road (62
road) or to the fixed red on the depot exit road (63 road). VL22B also
doesn't have an indicator but can clear for routes to either platform 4
(northbound) or 5 (southbound). So the north-to-south reversal is done
by: into platform 5, change ends, VL8 takes you to the fixed red on 63
road, change ends, VL22B takes you over the crossover and into platform
4, change ends, depart normally (VL6 with left-hand indicator).

[*] VL20 is not shown as having a junction indicator. I'm assuming,
therefore, that the only route from it leads to VL19.

This is correct.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is: