On Tue, 22 Sep 2009 00:47:06 +0100
Charles Ellson wrote:
On the sub-surface lines there are still armoured cables (and in the
old days, lead-sheathed cables) and air pipes which don't take kindly
to traction currents taking a short cut through them. More modern
materials and methods possibly reduce the risk of stray currents but
the signalling systems in current use IMU are still designed around
running rails devoid of traction currents.

Just out of interest, does any current trickle down the running rails into
the tunnels on the bakerloo line at queens park or are there insulators
nearby that prevent that?

B2003