Skip to Content

How Google Tests Self-Driving Cars

A self-driving car at Google's headquarters in Mountain View, California.Photograph by Noah Berger—AFP via Getty Images

When Google first invited employees to join its self-driving car project, some of them doubted its future success.

One worker—a Porsche owner—said he only wanted to participate because he loved gadgets, Chris Urmson, Google’s director of self-driving cars, said during an MIT Technology Review conference in San Francisco on Tuesday. The whole self-driving car project was “stupid,” Urmson recalled the man saying.

But after spending time riding in Google’s experimental self-driving car, the man changed his tune and told Urmson that he didn’t want to return the vehicle. The employee said he learned a lot about his own driving skills by letting the car drive for him.

“It turns out I’m a terrible deriver,” Urmson recalled him as saying. “All these people are terrible drivers,” the man said about the typical driver.

Urmson said that at the time 140 Google (GOOG) employees tested its self-driving cars in different conditions designed to train the vehicles to more safely navigate streets and highways. It’s a critical hurdle that the cars must pass before they can be approved for sale to the public.

Get Data Sheet, Fortune’s technology newsletter.

Whenever one of its autonomous vehicles encounters a difficult driving situation, like bicyclists driving down the wrong side of the road or a child running into the street to retrieve a ball, Google can use the episode to train its entire fleet of self driving cars.

Urmson said the car’s software has gotten so good that it can essentially predict where pedestrians will walk before they do. If someone suddenly jumps out—as in one case in which a man wearing no pants approached a Google vehicle—the car’s technology can immediately spot the potential problem and brake or steer out of the way, he explained.

Urmson showed conference attendees videos of Google’s car in action as it faced a host of real-life situations on the road. In one instance, a Google car came across people crossing the street as they played a real-life version of the old arcade game Frogger during which they attempted to hop over each other. The car ended up recognizing the people and stopped.

For more about Google, watch:

In another, a cyclist unexpectedly darted from an intersection straight toward a Google car as it was preparing to make a right turn. The bicyclist’s sudden movement was so unexpected that some audience attendees gasped. It looked like an accident was about to take place, but the car stopped and didn’t crash into the bicyclist.

“I am convinced I would have clobbered that cyclist,” Urmson said, highlighting the contrast between his driving abilities and the car’s.