How safe should self-driving cars be? This question is becoming increasingly
important as companies like Waymo, Uber and others test their self-driving
vehicles on public roads. But answering it turns out to be more complicated than
it might first seem. Around the world, something like 1.3 million people are
killed each year by vehicles. If self-driving cars could put a dent in
this, it would be a great achievement. Many of these deaths are down to human
error. In contrast, self-driving cars don't
drink. They don't text. And they don't fall asleep at the wheel. Reducing deaths
and injuries from these causes shouldn't be too hard for self-driving car
manufacturers. But it'll only count if their technology is so good that it
doesn't end up killing or injuring people in other ways! Here, manufacturers
are going to have to work hard to ensure their cars don't fall into human-like
behaviors like mis-reading road conditions, or missing important safety
cues. But they're also going to have other challenges to grapple with, like
sensors that fail to detect pedestrians, or algorithms that misinterpret what are
the car sees. Or even machine brains that just plain make bad decisions. Because of
these new and as yet poorly understood risks, manufacturers are going to have to
take great care to ensure their vehicles are acceptably safe. But this still
leaves us with the question of how safe is safe enough? Human drivers are a good
place to start here, and where better to look than Arizona, where many of these
vehicles are currently being tested. It's also sadly where the first pedestrian
was killed by a self-driving car. In 2016, 952 people were killed in vehicle
crashes in Arizona, and many of these were down to human weaknesses. For
instance, 21 percent of the drivers involved in these crashes were impaired
by alcohol drugs or medication. And two percent of them by illness sleep or
fatigue. Imagine what these figures would look like if 30 percent of those
vehicles on the road were driving themselves. There's a chance that around
90 lives a year could be saved -- as long as the self-driving technology was
completely safe. But what if it wasn't? What are these autonomous
vehicles also ended up killing some people who otherwise would still be
alive? In this case, how do we work out what acceptably to be safe means? One way to
approach this is to use the number of fatalities per billion miles traveled.
In urban Arizona, there were 518 people killed by cars in
2016, or around 11 people killed per year for every billion miles traveled in the
state. This is equivalent to around a 1 in 13,000 chance of being killed by
vehicle each year if you live somewhere like Phoenix. Maybe this should be the
benchmark for self-driving cars, or maybe a slightly lower number; say 8 deaths per
billion miles traveled. This sounds like a reasonable target. The only problem is
it's not that easy to prove if and when it's been reached. According to research
from the RAND Corporation, if a company had a fleet of 100 vehicles driving
around the clock, and wanted to show a 20% improvement in car related deaths
somewhere like Phoenix, it would take around 15 and a half years of testing
with no fatalities to achieve this. Things look even worse if a tighter
standard of a 20% improvement in pedestrian deaths for self-driving cars
compared to human drivers is used. In this case, it would take closer to 53
years of death-free testing with a hundred vehicles on the road. These sort
of timelines are clearly unworkable for demonstrating safety. Ironically, they're
so long because relatively few people are killed by cars compared to the
number of miles driven in the US, and so it takes a long time to build up
statistically significant data. An alternative approach is to rely more on
performance standards that ensure self-driving cars are designed for
safety under the toughest of conditions, and to monitor for early warnings of
potential failures -- ideally before anyone's killed. And because this is an
evolving technology, such performance standards should evolve along with it.
This would help develop the technology safely while not slowing it down
unnecessarily. But on the way, there will inevitably be crashes. And this is where
regulators and manufacturers need to start working with
communities, so that they can work together on what being acceptable safe
actually means. For instance, it may be decided that testing around residential
areas is okay, but not around schools. Or it may be agreed that testing where
pedestrians are likely to be paying less attention -- college campuses for instance --
is not such a good idea. On the other hand, it may turn out that local
communities are pretty risk tolerant when they see the potential benefits. You
never know until you ask! The bottom line is that, while self-driving cars could
make roads safer if the technology is developed responsibly, it's up to
manufacturers, regulators, and everyone else affected by them, to decide how safe
is safe enough -- and what they're willing to risk to reach the benefits the technology.