wrote:

So am I right in thinking that (roughly speaking) for continuous running a
conventional system is more efficient, whereas doing a lot of shuffling
along in heavy traffic a hybrid can be better? Has anyone done the figures

Quite probably. The prius gains some efficency from running the IC
engine in a non standard cycle that would usually be too lumpy to drive
with a conventional drive train, but then it also has to move all the
electric baggage about as well.

So in stop start conditions where it can accumulate surplus energy in
the electrics, it gets to spread out the demands on the IC engine, and
can (short term) produce more power than is available from the engine
alone. So good in city situations.

During sustained performance oriented driving however it will get hit
with the multiple whammy ofnot being able to sustain significant output
from the electric motor, carrying the baggage, and being forced to
divert a significant proportion of IC engines output to maintaining
battery charge (which must never be allowed to fall too low since the
enitre operation of the car depends on having electric motor power to
blend with the IC engine output since this is how the planatary gear
setup achieves the CVT).

(for current production technology conventional and hybrids) to work out
which would be better averaged out over national traffic patterns? In other
words, if you were to replace the entire national car fleet overnight with
equivalent hybrids would net fuel consumption increase or decrease?

It is a good question. I would expect the answer is "increase" since in
the real world you don't get something for nothing.

--
Cheers,

John.

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