On Wed, 27 Sep 2006 08:21 +0100 (BST), Colin Rosenstiel wrote:

OK, so it'd have to be "T5 via T123" and "T123 via T4". T4-bound
trains with a T5 service following a few minutes behind (close
enough that it will arrive at T123 first) could be shown as "T4 only".

How close behind a via T4 train would a T5 terminator have to be for the
latter to get passengers to T123 first?

Depends how long the T4 trains lay over at T4. Add to that the time
difference between going round the loop and going direct to T123, and
you have your answer.