Clive D. W. Feather wrote:

[*] There are some specific exceptions, such as Turnham Green
on the Piccadilly, and the signalling in these places is altered
accordingly.

In the case of Turnham Green, both lines do have home signals - the EB
line's homes are A631^A and A631^B, and the WB's are A630^A and A630^B.
Would the overlaps on these homes simply be longer than usual, to allow
a train to alternately stop or pass through at linespeed?


[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be
stopped before the point of actual danger (e.g. another train).
Designing for the maximum possible speed of all trains would be
unduly restrictive, so designing to the speed limit of the line is
a sensible compromise.


This doesn't make much sense. Are you saying that if a train passes a
red signal at linespeed or higher and gets tripped, the signal in rear
could change to green if the entire train manages to exit that signal's
overlap?