autonomous car could have the virtue of a (presumably) thoughtful decision-making script
to very quickly react in an opti mal way. If it is able to account for the many variables, then
it ought to, for the most informed decision possible.
First, suppose an object appears on the road directly in front of a car in autonomous
mode. Is there time to reasonably hand control back to the human behind the wheel?
(Probably not.) If not, is there time to stop the car? Would the car need to brake hard, or
would moderate braking be sufﬁcient? The decision to brake depends, again, on road
conditions and whether a tailgater (such as a big-rig truck) is behind you, including its
speed to determin e the severity of a possible rear-end collision.
Second, what is the object? Is it an animal, a person, or something else? If it is an
animal, are some animals permissible to run over? It may be safer to continue ahead and
strike a squirrel, for instance, than to violently swerve around it and risk losing control of
the car. However, larger animals, such as deer and cows, are more likely to cause serious
damage to the car and injuries to occupants than a spun-out car. Other animals, still, have
special places in our hearts and should be avoide d if possible, such as pet dogs and cats.
Third, if the car should get out of the way—either in conjunction wi th braking or not—
should it swerve to the left or to the right? In the US and other nations in which drivers
must stay on the right side of the road, turning to the right may mean driving off the road,
potentially into a ditch or a tree. Not on ly could harm to the car and occupants be likely,
but it also matters how many occupants are in the car. The decision to drive into an
embankment seems different when only one adult driver is in the car, than when several
children are inside too.
On the other hand, turning to the left may mean driving into an opposite lane, potentially
into a head-on collision with incoming vehicles. If such a collision is unavoidable, then it
matters what kind of vehicle we would crash into (e.g., is it a compact car or SUV?), how
heavy incoming trafﬁc is (e.g., would more than one vehicle be involved?), how many
persons may be involved (e.g., are there children in the other car?). Of course, here we are
assuming perfect sensing and V2X communi cations that can help answer these questions.
If we cannot answer the questions, then we face a possibly large unknown risk, which
makes driving into incoming trafﬁc perhaps the worst option available.
Other factors relevant to the decision-points above include: the road-shoulder type
(paved, gravel, none, etc.), the condition of the car’s tires and brakes, whether the car’s
occupants are seat-belted, whether the car is transporting dangerous cargo that could spill
or explode, proximity to hospital or emergency rescue, damage to property such as houses
and buildings, and more. These variables inﬂuence the probability of an accident as well
as expected harm, both of which are needed in selecting the best course of action.
From this short analysis of a typical crash (or possible crash) with an animal, we can
already see a daunting number of factors to account for. Sensing technologies today
cannot answer some or many of the questions above, but it is already unclear that braking
should be the safest default option— as a proxy for the most ethical option—given these
uncertain conditions, all things considered. Automated cars today can already detect
whether there is oncoming trafﬁc in the opposite lane. Therefore, it is at least possible that
74 P. Lin