John Rowland wrote:
"Dave Arquati" wrote in message
...

As another poster said, the platforms would be adjacent;
however, whether services actually run through from
Wandsworth Road - CJ - Imperial Wharf (& v.v.) is debatable;
for reliability's sake, an Orbirail service may just operate
CJ - Willesden - Dalston - Peckham - CJ and return.
The Circle line is an indicator that circular routes crossing
a variety of junctions perform poorly, as without a proper
terminus it is difficult for them to regain lost time.


The reliability depends on the time allowed at CJ, not on whether trains
return whence they came or proceed around again. (Actually there would be an
impact on reliability of circular trains caused by crossing each other's
path near Clapham Junction, but that would be minor.)

I meant that you can give them X minutes' turnaround at CJ, so if
they're a bit late arriving then they can still leave on time - whereas
on the Circle line they have some time at Aldgate but it doesn't seem to
be enough to counter much late running.

Publicising it as a "true" circular service, through from the SLL to the
WLL, whilst allowing X5 minutes at CJ, would be annoying to passengers
- much like existing waits at Aldgate or (until last week) on the
Heathrow loop. However, I accept that the direction the train departs in
doesn't really matter.

A connection-based approach might allow a relief time at CJ with faster
journeys for through journeys from West to South or vice versa. For
example, the following strategy would allow 7.5 mins' relief at CJ as
part of a 10 min service frequency, whilst only having a 2.5 min wait at
CJ for through passengers:

SLL - Platform 1 (0.0min)
Platform 2 - WLL (2.5min) Train 1
WLL - Platform 2 (5.0min) Train 2
Platform 1 - SLL (7.5min)

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London