Trams can also be battery powered.

http://www.google.com/search?num=100...+by+battery%22

To avoid unsightly overhead wires a third rail system can also be used as
was the case in central London and Washington DC.
wrote in message
ups.com...
On 19 Feb, 12:45, "Boltar" wrote:
On Feb 19, 9:46 am, "sweek" wrote:

How are they more attractive? Definitely not more attractive-looking,
and a tram has a higher capacity, unless they come up with a way of
letting double deckers under them. Trams also simply attract more
people since buses have a more negative and slower image.

If theres definately no option of a tram system being put in because
of cost then trolleybuses would have their place. Even if they don't
attract more passengers they wouldn't belch out any fumes into the
street which is always a good thing (even if the power station does -
but at least thats miles away).

B2003

In terms of pollution, the figures quoted on the website link are as
follows: -

CO2 Emissions Range (NYC Duty Cycle)
"Clean Diesel" 4,469 - 4,563 g/km
Hybrid Diesel-Elec 2,500 - 3,438
Trolley (UK grid) 1,744 - 2,189
Trolley(renewables) 0

So even with conventional electric power, trolleybuses emit less than
half the CO2 of conventional diesel buses and no particularates ( a
known cause of asthma)
Assuming the electricity was generated using renewables like Wind the
pollution levels approach 0.

The big advantage of the newer syle trolley bus over trams is their
ability to move round obstructions and the fact that they can be
independent of wires for several miles.
In Rome and Shanghai for example, they consciously chose this form of
operation in areas where overhead wires were excluded for
environmental/ conservation reasons.

While this requires a weight overhead in battery power, it makes them
flexible enough to compete with conventional diesel buses on certain
routes.

I am glad to hear the hybrid test is going well too.

Probably what will be needed will be a variety of systems such as
Tram, Trolley and Hybrid - aimed at reducing CO2 emissions.

P.S. The issue of hydrogen doesn't really belong in this thread, but
is debatable