IEEE Technology and Society Magazine - June 2016 - 34

ETHICAL DILEMMAS

Karl Stephan

ow much stuff do
you carry on your
key r ing? Besides
keys, I mean. Some
minimalists like my
wife carry car keys separately from
other keys, with nothing attached
except maybe a small plastic tag to
make it easier to find in her purse.
Other people, many of whom are
younger, may carry a whole bundle
of stuff on their keyrings: those little barcode cards that give you discounts at retailers, miniature plastic
poodles, handcrafted bits of knitted
yarn, and I don't know what all. But
it probably never occurred to you to
think that a heavy keyring could be
hazardous to your health.
Brooke Melton probably wasn't
thinking of her keyring one rainy
March night in 2010. She was driving her 2005 GM Cobalt when the
ignition switch suddenly moved
from "run" to "accessory." This had
the unfortunate effects of killing the
engine, disabling the power steering, and turning off the airbags.
The sudden loss of power caused
Melton to cross into oncoming traffic. The Cobalt crashed into another
car at 58 mph and wound up in a
creek, killing Melton and starting
a chain of events that revealed the
true cause of more than a dozen

Digital Object Identifier 10.1109/MTS.2016.2554445
Date of publication: 2 June 2016

GM Ignition
Switch Recall:
Too Little Too Late?
similar crashes going back more
than half a decade.
As long ago as 2001, engineers
at General Motors knew that a
certain version of ignition switch
assembly that was later used on a
number of car models had a problem. The mechanical design of an
ignition switch is a compromise, as
are so many things in engineering.
Most mechanical ignition switches
use a device called a detent, which
divides the continuous rotation of
the switch that would occur without the detent into a small number of discrete positions, typically
four: "off," "accessory," "run," and
"start." If the detent provides too
much resistance, the switch will
be difficult to turn and might eventually wear so much that it would
fail to work at all. But if the torque
(twisting motion) required to move
the switch is too small, you take
the risk that unbalanced forces
IEEE Technology and Society Magazine

resulting from heavy stuff on a keyring, for instance, may spontaneously make the switch turn from
one position to the other. This is
appa rently what happened to
Brooke Melton and the 12 or more
other drivers who died in ignitionfailure accidents in GM cars having
the suspect assembly.
At this remove, it is obvious what
GM should have done. The guilty
part, No. 10392423, should have
been redesigned with a more forceful switch detent plunger - a 57-cent
piece that consists of a rounded plastic cylinder backed by a coil spring.
It is the force exerted by this plunger
that sets the amount of torque needed to turn the ignition key from one
position to the next. Changing the
spring fixes the problem by increasing the torque needed to turn the
key from "run" to "accessory." Then,
the ignition assembly part number,
or some documentation somewhere,
∕

june 2016

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