[aussiesteve]

G'day electric traction boffins,
I have seen brief old BnW footage of third rail emu operation in the UK.
I don't remember the location, if detailed, and it would take a while to scan through my collection of DVDs.
There was a fourth rail, in the middle of the four-foot.
And sparks seemed to emanate occasionally when trains passed over gaps in this rail.
This infers that contact was being made with the fourth rail by the train.
I am wondering if this fourth rail was an additional traction current return rail.
OR, if this fourth rail was in fact the return current rail to separate traction current from signal rail circuits.
I assume that this fourth rail would need to be higher in profile than running rails.
To prevent fouling points, crosswalks and levelcrossings etc by the train central collector shoe.
I was told some time ago that a third rail was utilized on the smog hollow electrified network.
No contact with this rail was made by the train.
It was utilized to ensure that a positive return for DC traction voltage was maintained to substations.
But, I have not witnessed any evidence of this original third rail in Sydney.
And, don't recollect having espied any photos so depicting.
I think that I prefer the overhead supply system rather than third rail system.
OK, the atmosphere is cluttered with unsightly junk.
But, you can hoof around the track without getting zapped.
Mind you, you had better have that orange vest on these days.
AND, I remember one stringent instruction if the overhead was down and draped over the locomotive roof.
JUMP to the ground from the bottom step.
Steve.