On 30 July, 11:54, Adrian wrote:
Andy gurgled happily, sounding much like they were
saying:

You seem to miss the subtle detail that the distances are massively
long for any even remotely competent and roadworthy vaguely modern
vehicle.
I don't think that they're massively long. If you look at the table in
the highway code, it gives the distances in terms of car lengths (being
4m):

20mph = 3 car lengths, 50mph = 13 car lengths, 70mph = 24 car lengths
(=96m) with the other speeds in between.

75m, actually - we're talking about the stopping distance. Whether the
average driver's reactions accord to the guesstimates in the HC is
another question entirely.

But as the thinking distance is probably under estimated in the
Highway Code for a real life situation, . The whole of the time from
recognizing the danger to being at a stop is the important
consideration (and not really covered in the HC) when actually
stopping from 70 mph in real life, whether you've traveled 15m less
than the calculated number for the braking distance doesn't really
matter.


And, yes, they are - hugely so.

A quick google tends to bury actual road test information under swathes
of HC related stuff, but here's one...

http://www.insideline.com/subaru/imp...t-2002-subaru-
impreza-outback-sport.html

So that's a roughly 8yo test of a fairly heavy non-performance-oriented
car, with drum brakes on the rear and "all-season" tyres (virtually
unknown in the UK, being a compromise between the tyres we see (known as
"summer" elsewhere) and winter tyres).

127ft from 60 to a stop. 38m. HC quotes 55m. 45% further.

And do you honestly think that these distances are representative of
real life situations (with passengers, luggage etc), in a range of
cars with normal drivers who don't do brake tests as part of their
job? Remember, if you get it wrong on the road, you've hit the vehicle
in front, better to have the number in the HC erring on the safe side
than trying to be an accurate representation of the latest and
greatest cars on the road.