Re: Beware of high tech running amok

----- Original Message ----- 
From: "Brent P" <tetraethylleadREMOVETHIS@[EMAIL PROTECTED]
>
Newsgroups: alt.autos,rec.autos.driving,rec.autos.misc,rec.autos.tech
Sent: Wednesday, February 27, 2008 7:05 PM
Subject: Re: Beware of high tech running amok

> You mean like the 85th percentile speed limit and other well sup****ted
> contrarian to the general population items that the majority of the
> regulars of r.a.d. know to be true?  The problem isn't my conclusions,
> rather its that certain people, namely you Ed, refuse to have the same
> open mind to the facts as they do with the 85th percentile speed limit.


NOOOOOOOOOOOOOOOOOOO...not that. Where's the sup****t? I'll bet the best
you 
can trot out is a poorly constructed study from 25 or 40 years ago. There
is 
no verifiable"proof" that setting the speed limit using the 85th
percentile 
rule is any better than using the 80th percentile rule or the 90th 
percentile rule. Just determining the true 85th percentile speed is 
impossible in any meaningful way. Even if you determine the freely flowing

speed on a section of road under a particular set of conditions, exactly
how 
applicable would that me to a much longer section of the same road under
all 
conditions? As best I can figure the 85th percentile rule is favored by
two 
groups - traffic engineers who need to utter a justification for setting a

particular speed limit and people who think the speed limits are too low. 
The fact that people invoke the term often does not make it a scientific 
fact. You might as well say the earth is flat. For most practical purposes

it is. The 85th percentile rule is just a rule - convenient but not a 
scientific fact.

The best discussion of the 85th percentile rule I have seen is at 
http://www.dma.org/~ganotedp/85th.htm.
In the end I think they give you a 
fairly balanced argument for why the 85th percentile is useful, and they 
never fall into the trap of claiming that speed limits set using the 85th 
percentile rule are the "safest" speed limits. Their arguments tend more 
towards - speed limits set by the 85th percentile rule are the fairest
speed 
limits, or most democratic, or easiest to enforce. I can't disagree with 
these conclusions. What drives me crazy is people who try to claim there
is 
hard science that "proves" speed limits set by the 85th percentile rule
are 
the "safest" speed limits. That claim is total BS.

One more thing - how many speed limits are actually set using the 85th 
percentile rule? I don't mean how many are claimed to be set by the rule -

how many truly are?

C E "Ed" White (yes another Ed who doesn't like the way some people
wor****p 
the 85th percentile rule)