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From: mart@utcsrgv.UUCP (Mart Molle)
Newsgroups: net.followup
Subject: Re: Fast driving
Message-ID: <3122@utcsrgv.UUCP>
Date: Mon, 16-Jan-84 09:36:47 EST
Article-I.D.: utcsrgv.3122
Posted: Mon Jan 16 09:36:47 1984
Date-Received: Mon, 16-Jan-84 10:35:47 EST
References: <199@we53.UUCP>
Organization: CSRG, University of Toronto
Lines: 59

 > "As power(and hence, fuel) used is directly proportional to the SQUARE of 
 >  velocity, and viscous drag factors to the fourth and higher powers, it is 
 >  totally without justification to assert that no more fuel is used at 70 
 >  mph than at 55..."

Sorry Brian, unlike all those massless springs and frictionless hinges we all
used in freshman physics problems, automobiles do NOT exhibit ideal behaviour.
Using your reasoning, then, am I to believe that my car's fuel mileage will
approach INFINITY at very slow speeds?  My car's certainly does not.
Does yours?

Don't forget that (1) there are speed-independent contributions to the
consumption of fuel (such as the alternator, engine driven fan, internal
friction in the drivetrain, etc.), (2) gasoline engines are EXTREMELY non-linear
in their conversion to fuel into power, based on load, throttle position,
rpm, etc., and (3) automobiles are equipped with a DISCRETE set of gear ratios
in their transmissions, so that, say 55mph, could easily fall BETWEEN the
optimum speeds in two adjacent gears.  Thus such generalities are no more
relevant to the discussion of whether the fuel consumption of my car goes
up or down when my cruising speed increases from 55mph to 65mph than a
comparison of the assymptotic complexities of the bubble sort and quicksort
is to the problem of deciding which C program sorts 20 integers in minimum time.

Lots of airplanes attain their maximum cruising range at speeds greater than
55mph.  Why shouldn't some cars?

 >  "... and so you can see that the 
 >   ASSertion that no lives are saved is invalid without even referring to 
 >   the 1974 statistics on highway deaths which showed the first DECREASE in 
 >   highway fatalities coinciding with the implementation of the 55 mph limit."

I suppose it does not matter that 1974 also happened to coincide with a gas
crisis, a downturn in the U.S. economy and lots of other things which correlate
better with changes in highway fatalities.  How do you rationalize the fact
that the fatality rate declined EQUALLY on all roads that year, including those
whose speed limit was ALREADY at or below 55mph?  There have been some excellent
articles on this subject in `Road & Track' and `Car and Driver' within the last
couple of years.  Apparently the changes in highway fatalities correlate most
strongly with changes in the GNP [perhaps because poor/depressed people are
less likely to joyride or drink and drive?].  I suggest you go to the library
and browse through some back issues.  I found the charts on pages 68 and 69 of
the July 1983 issue of `Car and Driver' very enlightening.  They show that the
55mph limit has not altered the long-term trend in the death rate per vehicle
mile, and that annual traffic deaths follow the Industrial Production Index.
`Road & Track' had a much better-researched article a while back, but I don't
have it handy.

Many people resent the 55mph limit because its supporters sound like they are
on a holy crusade.  Sometimes saving fuel and lives seem like excuses for
protecting the 55mph limit from its ``obviously'' irresponsible murderous
opposition.  If the object really is to save fuel, why not first implement
20 other things that are more cost effective, like annual vehicle inspections,
even roadside spotchecks for tire pressure!  If the object really is to save
lives, why not first try compulsory seatbelt usage, daytime headlight usage,
or teaching people how to drive?  I don't see the logic.  It reminds my of
children who don't want YOU to do anything THEY don't like.

Mart L. Molle
University of Toronto