Brian,

On Tue, 15 Jun 2004 13:53:32 +0100, Brian Clewer wrote:

> Mike, I see your point here, but I think there is one think motorists don't
> think of.  That is the formula for kinetic energy is   1/2Mass times
> Velocity squared.

I'm sorry, but I think this misses the point, and is the basis of the "speed kills" attitude of the UK
authorities.  I don't think of the equation of energy when I'm driving because I concentrate on not having the
accident, rather than the consequencies of doing so.

> If you hit a person and you are going 30mph, you will do a certain amount of
> damage, lets say 30 squared is 900.  If you are going 35mph the damage goes
> up 36 percent to 1225...

This assumes that transfer of energy is the sole cause of injury - there are many more factors involved,
including the shape of the vehicle, the physiology of the latter (children tend to go under the front of the
car, adults tend to go over), and so on.  Getting run over by a steamroller would be pretty-much 100% fatal,
even at 1mph!

> I am not saying I have never broken the speed limit, but 5 mph over the
> limit is enough to easily kill someone, rather than just break their legs.
> Or if you put it another way, you have to get rid of 36% more energy to stop
> the vehicle from hitting someone.

Sorry, you're pulling a single factor (and some very dodgy assertions) out of a very complex situation.  There
will be some cases where 35 in a 30 limit might kill someone, but others where someone stepping out from the
roadside missed the 35mph car because it was passing at the time, whereas they'd taken another step to be in
front of the 30mph one, too close for it to stop.  It really isn't anywhere near as simple as "speed-limit =
safe, speed-limit + 5 = fatal".

Cheers,

Howard Winter
St.Albans, England

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