> I believe he was saying a length for every 10 mph of speed which, I believe,
> is legal, in optimum conditions.

I have never heard this method of calculation used by any official
entity--- mostly just people repeated "what they've heard". It just
seems like a vague and ill-defined rule. What, exactly, is a "car
length"? Well, we know a Vanagon is 14-15 feet, but who can really
calculate, by eye, on the fly, from the driver's seat,  6.5 Vanagon
lengths at 65mph? And is that really enough? The "rule" I've seen from
 most government safety busybody agencies is "2 seconds in good
weather". Two seconds following distance is 190 feet at 65mph... which
is a dozen "Vanagon lengths".

--
John Bange
'90 Vanagon - "Lastwagen"
'90 Vanagon GL - "Wiesel"