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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.auto
Subject: 55 mph kills
Message-ID: <77@ssc-vax.UUCP>
Date: Tue, 4-Sep-84 15:19:35 EDT
Article-I.D.: ssc-vax.77
Posted: Tue Sep  4 15:19:35 1984
Date-Received: Thu, 6-Sep-84 04:05:52 EDT
References: <3105@rabbit.UUCP>
Organization: Boeing Aerospace, Seattle
Lines: 32

[4 September 1984]

     The 55 mph speed limit kills as many lives as it saves.  The
calculation goes as follows:

     The fatality rate was quoted to decrease from 3.5 to 2.9 per
100 million vehicle miles from 1975 to 1982, presumably due to the
55 mph speed limit.  This is 0.6 deaths avoided.  Assume the average
age at death is 35 (weights toward the lower age drivers, who have
higher accident rates), and the average lifespan is 80 years.
The number of person-years saved = 0.6 x (80-35) = 27 person years.

     The 55 mph speed limit also wastes the lives of everyone who is
forced to take longer to get where they are going.  Assume 50% of
driving miles is at the speed limit, and that the limit was lowered
from a national average of 67 mph to 55 mph.  

     50 million miles/ 67 mph = 746 268 hours 
     50 million miles/ 55 mph = 909 091 hours
     an increase of             162 822 hours = 18.6 years

     Since each hour driving requires 1/2 hour sleep, the total time
wasted driving slower = 27.9 person years.

     I have used a number of assumptions in the above calculations,
but the conclusion is that the 55 mph wastes roughly as many lives
as it saves.  The waste is distributed differently.  The point is
never just look at the benefit of an activity, look at the associated
costs also.

Dani Eder / ssc-vax!eder / Boeing Aerospace Company / (206)773-4545