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From: smh@mit-eddi.UUCP (Steven M. Haflich)
Newsgroups: net.flame
Subject: Re: Another 55 mph flame
Message-ID: <255@mit-eddi.UUCP>
Date: Sat, 18-Jun-83 11:32:50 EDT
Article-I.D.: mit-eddi.255
Posted: Sat Jun 18 11:32:50 1983
Date-Received: Sat, 18-Jun-83 22:21:05 EDT
References: pur-ee.924
Lines: 60

I'm sorry if my previous argument was poorly explicated.  I had intended
to say something like the following:
	1) If all automobile traffic were limited to a maximum speed of
	   5 MPH, then essentially all fatalities would be eliminated.
	   (Well, you might still occasionally get an especially vulnerable
	   pedestrian, but nevermind...)
	2) If all "freeway" traffic were somehow forced to maintain speeds
	   in excess of, say, 90 MPH, except when entering and exiting,
	   then probably most drivers would succumb to serious crashes
	   within an unacceptably short period.
Now, if you replace the "magical" constraints on speed above with some
notion of average traffic speed, one can hypothesize a curve relating
human cost (in accidents) against average speed.  Clearly, this cost,
however it is measured, as nearly zero for absurdly low speeds, and
unacceptably high for absurdly high speeds.

We are not concerned with this cost curve at absurd speeds, but the
shape of the curve at intermediate reasonable values is crucial.
55 MPH is a reasonable (that is, non-absurd) value to consider for
an average traffic speed, as is 70 or 75 MPH.  I ask what is the
shape of the curve between these points?  Is there a sharp knee
somewhere in this region?  If so, cost/benefit analysis might
dictate *setting the average traffic speed* somewhere lower than
the knee.

Before anyone flames back, let me recognise the difficulties with this
whole approach:
	1) Laws setting a fixed upper speed limit are a Procrustian means
	   of establishing an operating point on the curve.  Certainly
	   it would be nice to rely instead on the judgement of individual
	   drivers.  Of course I trust you, just like you trust me, but
	   what about the other guy?...  I suspect a lot of the difficulty
	   with the 55 law is that it is a crude mechanism for *setting the
	   average traffic speed* appropriately.
	2) There is no clear way to measure costs.  Lost driving time is
	   a real issue, certainly, but how do we measure lost lives against
	   a similar number of person-hours lost daily on the NJ Turnpike?
	   Should they be balanced on an equal basis, assuming statistics
	   to relate them were really available?
	3) Accident statistics are mushy -- it would appear that controlled
	   experiments are almost intrinsically impossible.  Lacking really
	   solid data, we probably just have to make rational guesses.  Ugh!

My best judgement is that, whenever there is other traffic within a couple
hundred yards, 55 MPH is an upper limit.  I have driven through Nevada at
90 MPH (before the 55 limit) and it seemed appropriate for the time and
place.  But if someone were to drive that speed on the Mass Pike, I would
want him boiled in oil.  Now a question:  Does anyone have a better
method for assuring (legislating) appropriate safe speeds than the
blanket 55MPH we now have?  I wonder if it can be done.  In particular,
I would not trust any law which left the matter up to the judgement of
John Q. Motorist.  I wouldn't doubt the good reasoned judgement of
any of our colleagues who spend time improving themselves reading net.flame,
but what about the other folks on the road?

				Steve Haflich, genrad!mit-eddie!smh

P.S.:  I point out again, the energy dissipated in a crash as well
as the distance needed to stop both have square-law components based
on speed!