On Sat, 21 May 2005, TheOneKEA wrote:

Tom Anderson wrote:

I might have lost the plot, but that seems to make no sense whatsoever
- making the line longer wouldn't have capacity implications. You could
run trains at exactly the same frequency (if you had a few more), so as
far as Brixton is concerned, it wouldn't be any different. Or am i
being stupid?

Extending the line and adding more stations increases the number of
passengers that the line must carry.

Right.

To ensure that loadings remain even, train frequency must be increased
to compensate, which is the problem at hand.

Okay. I don't understand that - why does the frequency have to increase?

All Victoria Line trains that can be used are in use, AFAIK. The only
way to get more trains is to build them - the 2009TS.

That's very true - even if frequency stays the same, on a longer line,
you'd need more trains.

However, what i really want to know is ...

A loop at Herne Hill is not the only way to increase capacity on the
Vic - a flying terminus would do the job just as well, without the
pain of turning trains around.

What the hell is a flying terminus? I'm getting visions of some sort of
Hayao Miyazaki sort of affair ...

http://216.55.161.203/theonekea/unde...g-terminus.txt

Ah, i see. Very good.

The person who invented this has done the math and discovered that
reversing capacity on this terminal layout is very high - capacity is
only limited by the run in time + dwell time + run out time; if these
values are kept low, frequencies as high as 40tph can be contemplated.

That's encouraging.

We talked about termini a while ago: there's a thread called "Diesel
Electric Trains on CrossRail" that veered off into terrminal arrangements
on the Victoria line (maybe some sort of transport version of Godwin's
law?), where James - if that is indeed his real name - suggested that the
two optimal termini are the loop and what we call the 'Sao Paolo' or, more
specifically, 'Corinthians-Itaquera', (or, more usefully, something like
'double-island three-track two-rank') layout, which looks like:

D
/-----\
C / ### +----
---+ A----+
\ ### +----
\-----/
B

Not the greatest diagram ever (in particular, there are links between the
junctions just outside the platforms, which i don't make at all obvious),
but trains coming in from the east can either go into the reversing road
in the middle (A), or the westbound road at the bottom (B). Trains in the
reversing road just back out and head back east; trains in the westbound
road run on to the reversing road on the left (C), then turn round and
come back into the eastbound road at the top (D), before heading east
again. The upshot of all this is that there are no conflicting movements -
while the first train is monkeying about in the reversing road, a second
train can be trundling round the outside route.

SubTalk has the skinny:

http://talk.nycsubway.org/perl/read?subtalk=713864

Says they can do 40 tph with it, and Alstom claims they can do 51 tph with
it.

The discussion says that something called a '4-track relay terminal with a
2-track relay' used to exist at Park Row on the New York subway. No idea
what that is, but the poster seemed to be impressed.

tom

--
I don't know kung fu, I am kung fu.