On 25 Apr, 10:35, MIG wrote:

On 25 Apr, 10:27, Mizter T wrote:

(snip)

My questions is, would implementing ATO on the Northern line improve
performance enough so as to make unnecessary the plan to split the
line in two? Probably not is the answer...

I remember having trouble getting my head round this before. It
seemed that in order to justify the splitting of the line, it was
necessary to claim that the resignalling wasn't going to achieve very
much. But at the same time, the resignalling had to be worth the
money spent on it. The justification did seem to be working backwards
from the decision already made.


I suspect the argument is that ATO works best on a straightforward
'linear line' (as it were!) rather than one which has branches and
hence junctions, especially where those junctions for the branches are
at the heart of the line (Northern line at Camden) rather than at the
periphery (Central line). Having to send trains off onto different
branches means that the possible throughput of trains is
(significantly) reduced. Aiming for a situation akin to the Victoria
line (when it's working smoothly) where trains are coming through
every minute or two can't be done when one has to contend with sending
trains up different branches, and indeed merging trains coming in from
different branches.

In other words, you'll only get the optimum performance out of ATO if
you split it into two lines.