On Tue, 12 Feb 2008 05:02:55 -0800 (PST), Mizter T
wrote:

I've never really used a sat-nav system to compare true speeds with
indicated speeds, so I've never really been aware of the difference
between the 'true' speed I've been travelling at as opposed to the
'indicated' speed.

Be careful if you do use a sat-nav. If you're going up or downhill,
it will read slower because (so far as the satellites can see) you've
slowed down because your speed has a vertical component as well.

I guess that implementing a very accurate vehicle speedometer system
is hard to do, so I wonder if most vehicle (and in particular car)
manufacturers design their speedometers "on the safe side", so as to
indicate a faster speed than the true speed - based on the rationale
that it's better for drivers to think they're going faster than they
are, rather than think they are going slower than they are?

Yes, as it's illegal for one to read even 1mph under, but may read up
to 5% (I think) over. Thus, they all read over.

Neil

--
Neil Williams
Put my first name before the at to reply.