wrote:
Bob wrote:
http://www.tfl.gov.uk/tfl/downloads/pdf/T2025.pdf

Comments?

First I've seen about segregation of the Northern line.

They reckon they can get 30 tph on both branches by sorting out the
restriction around Camden.

What's needed for this?

I'm not sure quite what restriction they are referring to here - perhaps
something signalling-related.

I would have thought they'd need to interlace the trains and get 60 tph
through Camden, which they could do by shutting Camden. Or is there a
depot somewhere?

Physically speaking, the junction at Camden can already handle
segregation of Northern line branches without any new tunnelling - there
is no need to interlace trains, as there are no flat junctions. Trains
between one pair of branches (e.g. Edgware to Bank) can pass through the
junction simultaneously with trains between the other pair of branches.

It does not matter which northern branch is paired with which southern
branch, as long as they are segregated (however, there may be some
signalling constraints I'm unfamiliar with that make one combination
more preferable). The current service pattern fails at Camden when a
train from either southern branch destined for a particular northern
branch reaches the junction at the same time as a train from the other
southern branch, destined for the same northern branch - one of the
trains must wait and blocks trains behind it (destined for the other
branch).

TfL actually claim it just needs Capacity Improvements at Camden. What?
New platforms?

Interchange passageways. If the Northern line were segregated,
interchange at Camden would significantly increase, and the station is
too cramped to handle it. Wider platforms might also be necessary.

There was a discussion on this not that long ago here.

Otherwise, sounds so sensible why hasn't it been done before?

I think mainly because of the interchange problem at Camden. Northern
line passengers would also be upset at the loss of direct services to
their preferred branch - although this is something which passengers
south of Kennington have now become used to.

An interesting possibility partly related to Northern line segregation
is that of an extension of the Charing Cross branch from Kennington to
the south-east, towards Camberwell - it's a very long term prospect
which sits with its alternative, a southern extension of the Bakerloo.

--
Dave Arquati
www.alwaystouchout.com - Transport projects in London