On Apr 14, 9:52*pm, MIG wrote:
On Apr 14, 8:39*pm, wrote:





On Apr 14, 4:12*pm, MIG wrote:

On Apr 14, 8:46*am, wrote:

On Apr 13, 4:59*pm, MIG wrote:

On Apr 13, 2:03*pm, Tom Anderson wrote:

On Mon, 13 Apr 2009, MIG wrote:
On Apr 13, 12:14*pm, Tom Anderson wrote:

Been reading the last issue of London Loop. In an article about work on
the Northern line, it says:

* There will be more trains too - making a total of 24 on the central and
* northern branches, and 32 on the Morden section.

Do they mean trains, or trains per hour? Or something else? And is that 24
on each branch, or between the two? I'm guessing the latter and the
former, respectively!

Are these the improvements that are due to resignalling but being
attributed to splitting the line in order to justify the inconvenience
caused by that, but then attributed to the signalling as well to justify
the disruption caused by the signalling work, thus having all cakes and
eating them?

I don't know, but now i want cake.

Are you suggesting that with the new signalling, the line could be run
un-split and be as frequent and reliable as in the split case?

Probably as reliably as now anyway and certainly as frequent. *I think
that the split is a case of the common tactic of reducing the service/
convenience in order to get browny points for "punctuality" (because
it takes less effort to run it on time). *But the signalling allows
for some compensation in increased tph.

I am pretty certain that the increased tph is due to the signalling
rather than the split, and that the movements are equally disruptive
whichever pair of branches is involved.

The gain will be in not having to deal with services from both
northern branches going different ways at the junctions south of
Camden Town.

Some increased slack for punctuality in the overall service may result
from the split, ie delays from one branch not affecting both branches
the other side of Camden. *I can't see that that has anything to do
with tph.

If there is a full split in service, for example, with the High Barnet
branch only serving the Bank route and the Edgware branch only serving
the Charing Cross route, then it will be possible to operate more
services through Camden without changing the signalling, as you don't
have to wait for point movement and locking between each train.

I can't see this making any difference. *Points would be changed while
the next train was standing in the station, given that it couldn't get
in till the previous one had left anyway.

But at the moment, there may be two services going the same way in
different platforms and allowance has to be made for this.

(In fact it might even allow more tph in that a train going a
different way at a junction doesn't have to wait for the previous one
to clear the section.)

You're forgetting that there are two routes potentially leading in and
it is the dove-tailing of these that decreases capacity.

There are no flat junctions to consider whichever way they go, so a
few seconds changing the points while a train is in the station can't
really make any difference to tph.

Some of the connections are too short to take a train, for example the
connection from the SB Edgware to SB City is too short to take a
train, until the preceeding train has made room. If the preceeding
train comes from the Barnet branch, it has to clear the section before
the pointwork can be set up for the ex-Edgware train.

The split may affect reliability, but I don't believe it can affect
tph.

Increased tph will, however, be offered as a mitigating factor when
people complain about the split.

What you are failing to see is that keeping the point work in one
position means that the trains don't have to wait at Camden Town for
the route to be clear and set. You get more trains through the
junction because you don't have to leave space for the two services to
intermix, trains will run more reliably through the junctions because
they (should) be coming at a fixed interval from the same branch. At
the moment, there has to be some allowance for a train arriving
slightly late from one of northern branches in the timings for the
other branch. The suggested 24tph is a train every 2 1/2 mins, whilst
20tph (which is the approx. frequency at the moment) is a train every
3 mins, that extra 1/2 min will come from not having to path trains
from the two northern routes into the two central routes.-

You may be right, but in that case what is the signalling work meant
to achieve?


As the resignalling work will include ATO, it should lead to shorter
times between stations and so quicker journey times. The automatic
operation on the Central line certainly did this.

My assumption (also in reply to Mr Thant) is that the potential
improved headways will not be exploited fully, and we'll get what they
could have been without the split, but with the split added to improve
reliability.

Timetabling more trains through the junctions with the current mix of
services looks like a recipe for unreliability to me, as the leeway in
the timetable at Camden will be less.