Tom Anderson wrote:
On Wed, 10 Jan 2007, Dave A wrote:

Tom Anderson wrote:
On Tue, 9 Jan 2007, asdf wrote:

On Tue, 9 Jan 2007 13:07:54 -0000, John Rowland wrote:

Personally I dont see why the Met line has to run to Barking?

Because at the moment, the Met trains empty out in one direction and
fill up in the other. It's better to have them filling up with new
people as the old ones get out.

And by swapping the eastern destinations of the Met and H&C, exactly
the same thing happens with the H&C...

But the Met east of Baker Street has 120 carriages per peak hour,
whereas
the H&C has something like 48 carriages per peak hour.

But if 15 Met tph are to head through Aldgate East, some Districts
will have to be cut back to Tower Hill (and/or Mansion House) to
make room, which just shifts the same situation onto those Districts.

No, because the Mets replace H&Cs.

asdf has a point - the current H&C service is only 8tph. If all 15tph
Met go to Barking, then 7tph will have to be removed from the District
service

Allowing another 7tph of Hammersmith trains to be Teacups rather than
Aldgates - by jove, Holmes, we've cracked it!

Assuming they reverse somewhere like HSK or Edgware Road, rather than
Tower Hill, of course.

- I imagine that demand for services along the southern Circle is
higher than for the northern Circle.

Ah, but between where? If the demand is along the actual circle bit
(Charing Cross to the City, say), then heavily pruning some Districts
back to a western point and replacing them with Teacups would be fine;
if the demand is actually from the western District suburbs to the south
side of the circle, it wouldn't, and the admittedly far more sensible
idea of reversing some Districts at Tower Hill would come into play. The
only case where you need to preserve the full District service beyond
Tower Hill is if there's much more demand for trips from the eastern end
of the District/H&C to the south circle than the north.

Hmm. I think i'm in knip there.

Anyway, yes, there you, all fun and games until someone loses a
peak-time through train.

OK, here's some data to chew on - Figure 4C.2 of the Mayor's Transport
Strategy is a particularly useful diagram showing Underground crowding
levels for 2001, with the following figure showing predictions for 2011
- so imagine something between the two. The width of the lines is the
magnitude of demand, and the colour is the crowding level. (You need
good zoom or good eyesight to check that you're looking at the correct
direction of travel.)

2001 shows a higher and crowded passenger flow from Aldgate East to
Tower Hill, and a much lower (but still crowded) flow from Aldgate East
to Liverpool Street.

2011 prediction (albeit this is meant to be without the Transport
Strategy) shows crowding again to Tower Hill and a still low but "very
crowded" service (i.e. crammed) from Aldgate East to Liverpool Street.

Demand from the western branches into Victoria and the City is very high
and very overcrowded, compared to that from the east.

The difference in the magnitude of demand in the east suggests that the
Tower Hill service should be much more frequent than the Liverpool
Street service (perhaps doubly so), which I think is about the shape of
things at the moment.

It's also worth bearing in mind that a reduced-frequency
east-District/southern-Circle service may push people onto the
very-high-frequency Central line at Mile End to get to Bank or St Paul's
(whereas they would have stayed on to Monument, Cannon St or Mansion
House), and the Central line already suffers worse overcrowding than
either the District or the H&C in this area.

To me this suggests that the District frequency to/from the east should
be maintained, as the balance is quite delicate.

Perhaps 7tph from the Met will terminate at Aldgate alongside 8tph
from the new H&Circle service.

Well, or that. So now we have both the Met and the H&C having half
Aldgate and half through trains. What fraction of District trains
reverse at Tower Hill rather than running through? ISTR it's actually
quite a lot.

As Clive mentions, it's about a third of the District service (Ealing
Broadways).

Trying to get my head around this service pattern is as difficult as
the multitude of proposals for the North London Railway.

I had a look at the service patterns on the railway south of the river
the other day.

*shudders*

Indeed. However, whilst the downside is that they're complicated, the
upside is that they end up matching demand more closely than simpler
Underground all-or-nothing service patterns.

They do also relieve some stress from the Underground by offering a
choice of termini...

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