How Safe Are Self-Driving Cars?

Waymo Proves They’re Pretty Darn Safe

On Tuesday, Waymo (formerly called Google’s Self Driving Car program) announced a bold new step in the deployment of electric automated mobility services that will eventually reduce CO2 emissions by almost a gigaton per year and help limit global temperature rise to less than 2 degrees. Hundreds of Arizonans will be accepted into a pilot program to use Waymo autonomous vehicles to go about their daily business (within a radius around several areas near Phoenix—no Vegas road trips yet).

Waymo has logged over two million miles on U.S. streets and has only had fault in one accident, making its cars by far the lowest at-fault rate of any driver class on the road— about 10 times lower than our safest demographic of human drivers (60–69 year-olds) and 40 times lower than new drivers, not to mention the obvious benefits gained from eliminating drunk drivers.

However, Waymo’s vehicles have a knack for getting hit by human drivers. When we look at total accidents (at fault and not), the Waymo accident rate is higher than the accident rate of most experienced drivers (Figure 1). Most of these accidents are fender-benders caused by humans, with no fatalities or serious injuries. The leading theory is that Waymo’s vehicles adhere to the letter of traffic law, leading them to brake for things they are legally supposed to brake for (e.g., pedestrians approaching crosswalks). Since human drivers are not used to this lawful behavior, it leads to a higher rate of rear-end collisions (where the human driver is at-fault).

Figure 1. Autonomous vehicles can lower the number of teens involved in traffic accidents.


Motor vehicle accidents are the leading cause of death of teenagers in the United States—with as many as 8,000 deaths per year caused by drivers ages 16–20. Released to the roads by themselves after only a few months of training, the overwhelming new freedom and responsibility leads to immature and dangerous decisions. In addition to causing the largest percentage of vehicle fatalities, AAA found teen drivers cost the American society over $34 billion annually. This includes medical expenses, lost work, property damage, quality-of-life loss, and other related costs.

If every teenage driver in Phoenix took Waymo instead, there would be as many as 12,000 fewer accidents per year. If all U.S. teen drivers traded car keys for the Waymo service, we could eliminate one million accidents and countless teen fatalities. Since we allow teens to drive on our streets, it makes sense that we should allow autonomous vehicles—a safer option—to drive on our streets as well.


Many cities, states, and federal agencies are actively encouraging autonomous vehicle deployment, but this is not universal. Some politicians are trying to delay autonomous vehicles out of genuine fear of the technology and others from fear of disrupting major business such as auto dealers and insurance companies. Additionally, the new technology has not yet gained the same level of trust as other transportation systems, further holding back deployment.

Figure 2. Not unlike air flight, autonomous driving must earn our trust, but humans have been adapting to new technologies for centuries. Trading fear for adventure will improve the safety of our roads.

A 2017 study by Deloitte found that three-quarters of Americans do not trust autonomous vehicles. Perhaps this is unsurprising as trust in new technology takes time. Comparably, air flight took many years before most people lost fear of being rocketed through the stratosphere at 500 mph in a pressurized tube propelled by exploding jet fuel. But few air travelers bat an eyelash now, calmly completing crossword puzzles and productively working on wifi as if it’s normal for humans to fly.

The trust in technology takes time. However, with five automobile fatalities occurring every hour, we do not have time for fear to delay autonomous vehicle deployment. While autonomous vehicles may still be in their equivalent of Drivers Ed, we must embrace this phase of autonomous vehicle deployment in order to reap the potential benefits of tens of thousands of saved lives and millions of avoided accidents.


A near-term solution is for autonomous vehicles to prove themselves in demonstrations and pilots not unlike the way teenagers drive first with parents and instructors. To this end, RMI is developing autonomous vehicle pilots and programs on the ground in Austin, as a means to promote their commercial deployment and legality, and drive adoption by consumers. Determining the bar for driverless vehicle legality is critical. It must be fair when compared to our bar for human drivers. Once an autonomous vehicle and software meet this bar, it should graduate to a full license and be allowed full access to the roads. This is how society has taught every driver to drive, why not keep the same process for computer drivers?

Fortunately, this awkward phase will not be long, as autonomous vehicles learn much faster than their teenage human counterparts. Unlike a 16-year-old driver, autonomous vehicles know what to do in countless road scenarios, never forget their lessons, and never get drunk or text. In the long run, whom would you rather encounter on the road—a newly licensed teenage driver or an autonomous vehicle? And down the road, what if every driver you encounter is the best driver in the world? An interesting thought for your next road trip.