In message
-septemb
er.org, Recliner wrote:
This seems to imply that overhead + 4th rail is in some way harder to do
than overhead + 3rd rail... I would have thought it would be the
other way around.

I think it just so happens that no fourth rail DC trains normally share
tracks with any overhead line AC trains.

I can't think of any instances: I'm fairly sure the tracks are
segregated throughout at Barking and Upminster.

Euston used to have shared 4th rail and AC; that section was converted
to 3rd rail at some point in (IIRC) the 1980s.

Not sure if the Willesden TMD entry road is shared 4th and AC or just
shared 3rd and AC.

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