Basil Jet wrote on 14 November
2009 14:37:48 ...
Richard J. wrote:
Basil Jet wrote on 13
November 2009 10:46:44 ...
Richard J. wrote:
Basil Jet wrote on 13
November 2009 03:21:14 ...

But if you take David's plan and extend the Edgware Road
terminators back to Hammersmith (i.e. Hamm - KX - Vic - Edg Road -
Hammersmith, running in both directions) then you have ...

... confusion! Since your "extension" is actually a reversal, you
effectively have (a) a Hammersmith - Edgware Road shuttle, (b)
Hammersmith - KX - Vic - Edgware Road in both directions. You now
have two services terminating at Edgware Road, which is what David's
plan was trying to avoid.

No, you would have 12-16 trains an hour reversing without waiting.
Ha ha, very funny. :-)

baffled

Oh, I thought it was a competition to find the most impracticable
alternative to LU's plan. But if you're serious ...

"Reversing without waiting" implies stepping back, otherwise you'd have
to wait for the driver to walk the length of the train. Stepping back
two different services at one station would be seriously challenging,
especially if you're trying to do it within a normal dwell time, or in
practice probably 1½ minutes. LU aren't very successful with driver
changes in mid-route, e.g. Acton Town.

If the Wimbleware and Circle services both run at 6 tph in each
direction, you'll have 18 reversers per hour at Edgware Road (6
Wimbleware, 6 Hammersmith to inner rail, and 6 outer rail to
Hammersmith), not "12-16".

The point is that the recovery time would not be at Edgware Road but at
Hammersmith, Wimbledon and Barking etc.

Yes, that's the problem! If you don't provide any recovery time at
Edgware Road, any delay in one direction will automatically disrupt the
other direction too, partly because a late arrival at Edgware Road will
become a late departure, but also because conflicting moves at the
crossovers at Edgware Road and at Praed Street Junction will worsen the
delays. In other words, the reliability of the Circle Line will suffer
from the same problems that occur today.

Ensuring step-free changes at Edgware Road would probably become more
difficult too.
--
Richard J.
(to email me, swap 'uk' and 'yon' in address)