On Sat, 27 Jun 2015 23:43:43 +0100, "Clive D. W. Feather"
wrote:

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.

It would have been converted at the same time as the rest of the DC
line (and the 4th rail has since been removed) so the same as the
shared lines into Euston. While the sectional appendix instructs that
non-LU trains are not to enter Stonebridge Park depot or Queens Park
sheds under any circumstances there seems to be no converse
instruction preventing a disabled LU train or vehicle from being
shunted into Willesden TMD if necessary.

In article ,
(Charles Ellson) wrote:

On Sat, 27 Jun 2015 23:43:43 +0100, "Clive D. W. Feather"
wrote:

In message

-september.
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.

It would have been converted at the same time as the rest of the DC
line (and the 4th rail has since been removed) so the same as the
shared lines into Euston. While the sectional appendix instructs that
non-LU trains are not to enter Stonebridge Park depot or Queens Park
sheds under any circumstances there seems to be no converse
instruction preventing a disabled LU train or vehicle from being
shunted into Willesden TMD if necessary.

And 4th rail provision exists south of Queen's Park towards Kilburn High
Road to allow for LU trains, surely?

--
Colin Rosenstiel