On 26 Nov 2020 10:33:55 GMT
Marland wrote:
On sections shared with third rail trains the positive rail has always
been at the full potential whether
that has been 630V or 750, the fourth rail becoming neutral like the
running rails to which it is bonded. I don’t know what the arrangements

I can't seem to find a definative answer about that line, but it would
seem that you're right about thr 4th rail being bonded to the running rails
and the way tube trains can run on the Watford line is that the 3rd rail
was only at 630V so mainline trains were running on a lower voltage rather
than tube trains running on a higher one which makes more sense. I'd guess
the Richmond and Wimbledon routes are the same. Or were until the S stock
came along.

Crossposted to utl.