In article , The Natural Philosopher wrote:

No issue there. But people never used to switch off engines in jams
anyway. And you don't need steering when the car is staitonary..

I remember when they did. If nothing else, they would overheat if
you didn't. And, in the case of cars like the Citroen, I am afraid
that you DO need the engine when stationary and not parked.

2) Catalytic converters virtually eliminate carbon monoxide, but
increase the amount of nitrogen oxides. Worse, they work only after
the engine has warmed up (about 5 miles) and the average trip in the
UK is about 3 miles. Also, they don't work at all well when the engine
is idling (see (1). The reason that they "reduce pollution" is the
the government is very careful to measure only what they do reduce.

I don't think you are correct on that. The NO stuff anyway. The biggest
benefirt is that they do (once hot) redice hydrocarbon emmissions that
are teh bigger causes of smog. Not disagreeing with your main point tho.

I didn't say NO, but nitrogen oxides. Some are produced in the engine,
and they may be changed in valency but will not be destroyed, and some
will be added in the converter. You get slightly more, but a different
set - and lean-burn engines produce more, too, unless great effort is
taken to reduce that effect.

I agree on that. But I have noticed something different. I can drive the
M25 on a sunday, and not be badly affected. But on a weekday.....its hell.

The difference? No diesels. Diesels produce emormous quantities of very
nasty pollution and are not subject to legislation.

Yes, they are, but it is much weaker. The fines are risible for a
transport company. Blame Whitehall, again :-(

I agree on cycling. Too many cars for it to be safe.

That's not the reason, because the drop has occurred as much in areas
where there has been no increase in the number of cars. Saturation is
saturation.


Regards,
Nick Maclaren.