🚀 go-pugleaf

In article <1992Mar27.160239.8237@seas.gwu.edu> declan@seas.gwu.edu (Declan McCullagh) writes:
>I'll not comment on the editorial, save for questioning one of the
>Post's main arguments - will highway speeds of 55 mph save any gas
>over 65 mph speeds?  Extemporaneous evidence suggests a 65 mph limit
>will _not_ increase gas consumption.

Since I started this whole discussion, I'll throw in two more cents
on the issues the Post editorial brings up.  I would have responded
directly to Karl Anderson's request for references except that I
haven't been in the vicinity of my archive of National Motorists'
Association propaganda in the past three weeks.

The fact of the matter is that thanks to aerodynamics, it is pretty
much always possible to construct a car that is more fuel efficient
at 55 than at 65.  Of course, the same holds true for 45 and 35.  In
fact, if you remove the need to withstand accidents at those speeds,
you end up with an optimal speed of something like 18mph.  What the
people opposed to 65 on fuel economy grounds don't tell you is that
there is no magic point on the curve at 55 mph above which fuel
economy suddenly takes a precipitous drop.

What they fail to understand is that a car's efficiency at the speed
limit is governed by the speed of the engine and the power necessary
to maintain that speed, NOT by the speed of the _car_ itself.  When
the limit was lowered in the early seventies, cars were unaerodynamic,
their engines were built for peak horsepower at high RPMs in order to
win the advertising game, and their transmissions had fewer and lower
gears.  Almost no modern cars suffer from any of these liabilities
anymore.  Most are built to win the economy race, which means that top
gear is selected to provide optimal mileage at low RPMs on a level
surface at 55mph.  Unfortunately, the real world is full of hills, and
at these speeds the engines are incredibly inefficient when presented
with more fuel, so you'll actually see higher overall efficiency at a
slightly elevated speed.  My car, which isn't even geared for the US
market, posted its highest ever gas mileage at a constant speed of 78,
which suggests to me that the fuel-efficiency naysayers are unable to
appreciate the complexity of the problem.

Will raising the limit dramatically raise the death rate?  The evidence
suggests not.  Michigan actually saw a slight drop in its death rate
after going to 65, but part of that can be attributed to higher seatbelt
compliance.  In every state which has raised the limit, however, the
observed overall increase in speed on those stretches has been around
three mph, which suggests that 55 was artificially low.  The Post article
also neglects to mention that 270 north of 124/117 may be _considered_ for
65 under the bill, if the traffic engineers so deem it safe.  It's hardly
an automatic increase, and the prima facie speed limit law remains in full
force.

So, why does your insurance company want to keep the limit at 55?  Yes,
they do want to make the highways safer, but mostly they're just paying
lip service to that line.  It's the point surcharges.  Each point on
your license means roughly $600 to your insurance company over the life
of the point.  To be fair, they didn't stand to gain this profit when
55 was first introduced; they didn't even know it existed.  But if you
were a private corporation who had the legal right to demand, in exchange
for nothing, an additional $600 every year from each of two million people
who were doing nothing particularly risky, dangerous or abnormal, wouldn't
you fight to keep it that way?

-dave

-- 
David Hsu    hsu@eng.umd.edu      "There you stand like a duck in a
U of Md Systems Research Ctr       thunderstorm again - aren't you ever
College Park, Md  20742-3311       going to understand?"
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