On Apr 14, 4:12*pm, MIG wrote:
There are no flat junctions to consider whichever way they go

But there are still inherent conflicts. Only one train at a time can
enter each of the northbound platforms at Camden, and only one
southbound train at a time can enter each of the Bank or Charing Cross
branches. So, for example, if an Edgware-Bank train leaves Camden on
time, and a High Barnet-CX train for whatever reason leaves 30 seconds
later, the Edgware-CX train behind the Edgware-Bank train is also
delayed by 30 seconds while it waits for the signals to clear
(assuming it was timetabled to run at the minimum signalling headway).
Then all of the trains behind are delayed. Your achieved tph drops a
notch each time this happens.

The split may affect reliability, but I don't believe it can affect tph.

I think you mean signalling headway (or something like that), which
indeed it doesn't affect. But you also have to add a bit of padding to
account for any small delays or variability in each train's progress
before you can pin down an achievable tph figure. And as I've tried to
illustrate above, the junctions at Camden mean you need a lot of this
padding. This isn't about disruption, this is about simple variations
in when trains arrive, which each and every train has a little (or a
lot) of.

U