Clive D. W. Feather wrote:

In message , David C
wrote:
I'm not saying it can't be done but it is a lot more complicated
to signal so tends to be avoided. The LUL 3rd & 4th rail
electrified tracks lie between platform 1 and the overhead
electrified tracks, don't they? So the Barking Riverside route
won't go near platform 1 so why keep it in service?

Sorry but you are not making any sense.

As has been mentioned, 25 kV AC electrification has co-existed with
the under-ground since 1962without any problems.

I think there's a misunderstanding here.

There are serious problems with having third (or third/fourth) rail
on the same line as 25 kV, to do with earthing and track circuits.
Therefore there's good reasons to avoid that.

But, on the other hand, I don't believe there's any significant
reason not to have 25 kV and third rail on adjacent tracks.
Particular with platforms in between.

I seem to recall that the reason the AC/DC changeover on the West
London Line isn't at Shepherds Bush station is because of possible
interference with the H&C line (and that isn't even adjacent).

Peter Smyth