David Bradley wrote:

Considering the overhead aspect, a tramway service will use a pantagraph
system for current collection. The traction wires require to be at a
significant tension for the contact wire to be almost horizontal and there is
considerable upward pressure from the pantagraph itself. Such forces need
some quite chunky traction support post which are invarably girders and
horizontal "scaffolding poles" as the primary support. Hardly asthetically
pleasing and yet it seems to be acceptable because it is a tramway.

The photographs of Sheffield and Manchester, on your page:

http://www.tfwl.org.uk/sbt.html

don't seem to bear out that assertion. As for using H-section girder
for posts, the only place that seems to have done so is Croydon, and
that is now acknowledged as something of a mistake.


On the otherhand trolleybus current collection methods use twin booms wich are
more tollorant of the contact wires which are at a lower tension than that for
a tramway. Consequently lighter traction support poles can be used. The
amount of actual wiring in the sky is not significantly different between
either system.

Except that it has twice as many contact wires.