On 19 Dec 2003 05:17:01 -0800, (Stephen
Furley) wrote:

Spyke wrote in message ...

Of course, where there were tramlines already, they could use those, but
they were horrendously impractical.

Of course, you'd have to modify the tramlines with the return wire as
well. (Trams only need one wire as they return the current through the
rails).

Trollybus overhead infrastructure is a lot more complicated and
expensive than that for trams; it's not just a question of two wires
instead of one. This does not mean that there are no circumstances
where trolleybuses are the best answer, but it is a factor which has
to be considered.

Historically this is true because of the multiplicity of routes that
used to operate in London and therefore overhead junctions were a
common sight. Junctions aside, there is substantially less wiring in
the sky for trolleybuses than is the case for tramway operation.

If there were a rebuild of a London trolleybus system of a similar
route mileage, complex overhead junction wiring would not necessarily
re-appear. Indeed for 'sensitive areas' their may be no overhead
wiring at all since two factors would come into play, on board APUs
[or battary operation] and the ability to automatically lower and
raise the booms.

For electric street transit ,where a routing does not use any former
heavy rail routes trolleybuses are the only sensible answer. That is
the right factor to be considered, no others.

In September 2003 the Landskrona Trolleybus system opened and here is
a picture taken of one of the vehicles:
http://www.aveuk.nildram.co.uk/trans.../P9270037a.JPG
You will notice the lack of complexity of the overhead wiring and
don't be foolled into thinking that if this was a tram there would
only be one wire. Cast your eyses upward in Croydon and you will see
what I mean.

David Bradley