> Aside from all that nit-picking, studies show that at 25MPH (pretty
> close to 30KPH) significantly fewer deaths result due to car accidents
> than at the next higher speed.  It's not a matter of 'if' someone will
> be run into, it's a matter of 'when' and how bad it's going to be.  At
> 30KPH most people live no matter how they were hit.

As I noted previously, an empirical formula that gives a rough feel for
pedestrian death rate versus impact speed is

    Death % = V^2/50            v in kph

        kph        % killed
        20         8
        25         12
        30          18
        35          24
        40          32
         45         40
        50          50
        60          70
        70          100
        >70        Overkill

I produced this formula based on published speed versus death percent
figures.
As energy in vehicle rises with V^2 this makes some intuitive sense.

Obviously SOME people will die in a 5kph collision and some will survive a
100 kph collision but ther above gives a feel for probable results.
Obviously (but not apparently to some judging from some offlist criticism I
received) this is just a guide and makes a statement about probability.

Note that this is IMPACT speed. If you are travelling at 30 kph and get to
the brakes before impact you will be going even slower and the chancesof the
pedestrian living are excellent. At even 50 kph the reaction time carries
you further, you are further away from the pedestrian when they step out
(and especially for a child will be less noticeable) and the chances both of
impact and death are MUCH higher.



            Russell McMahon

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