On Thu, 22 Dec 2005 22:43:42 -0700, Clark W. Griswold, Jr. wrote:

"Alan J. Flavell" wrote:
Evidently, in the event of a problem
(road blockage, OHL or power failure) they would be capable of
continuing in service on the other power source.

As do some in the US - Seattle among other cities use them. Interestingly
enough, it appears that they are being phased out though. Note the last
paragraph:


Metro plans to rebuild them as
electric-only articulated trolley buses and bring them into service in 2004-2005
on high-ridership routes 7, 43, and 44.

http://transit.metrokc.gov/up/archiv...4-trolley.html

I bet they have traction batteries though - the weight of the diesel
engine and the fuel tank would hold quite a lot of battery power.


The new Roma (Italy) Route 90 trolley buses actually run the into the
city centre on battery - the wires stop at the old city wall. They stop,
drop their poles and drive in on battery.

The lights dim slightly, the air-conditioning stops, and the bus can't
accelerate as hard when the poles are dropped, but they are quite capable
of moving with the traffic at that point.