On Oct 9, 12:15*pm, Robin9 wrote:
You may well be right but that's a very negative line of reasoning.
First, how often do they have train break-downs? Second, why not have a
contingency plan for that kind split system in the event of a train
break-down but in normal circumstances operate a conventional circular
service?

A break down is the most obvious case. The far more common one is
gradual accumulation of delay seconds. A held door, a delay of a Met
service beyond Baker St., A District service running late due to a
passenger alarm...all these things can cause the Circle service to
start running late. Without a terminus...it can only get later and
later, and eventually, the lateness builds up and it starts missing
it's path at junctions and controller intervention is needed to fix
things by taking something out of service, probably at Edgware Road as
it's one of the few locations with the correct trackwork.

It's why I'd like to have the former widened lines as part of the SSL
system. Assuming connections made at Farringdon and Moorgate, give the
centre roads over to the Circles, and run the Mets on the outer lines.
Circles could be scheduled to simply bypass delayed units on these
sections. A similar arrangement could be instituted between Gloucester
Road and South Kensington (where it already kinda does, as the
westbound District and Circle are kept separate). Knock though the
bays at Mansion House and Tower Hill and you have another couple of
locations where you can do this as well. Maybe Aldgate too