How Waymo is teaching self-driving cars to deal with the chaos of parking lots - Popular Science

If you drive a car, you know that some maneuvers are harder than others. For example, an unprotected left turn—one with no green arrow to tell you when to go—will always be trickier than a standard right-hand turn. Humans aren't alone in those struggles. Unprotected lefts are also a challenge for cars driven by computers, and so they train for them in simulation. Autonomous car company Cruise even published a video highlighting the 1,400 left turns its vehicles tackle in San Francisco in a day.

A left turn is a tricky maneuver, but the driving environment itself is also a factor in what kind of obstacles the human—or the self-driving car—might encounter. A two-lane road on a sunny day with clearly painted lines and scant traffic offers an easy landscape. But an Ikea parking lot on a Saturday afternoon? Ouch.

In fact, parking lots are a distinctive enough environment that Waymo, the self-driving car company that’s a sibling to Google, specifically trains its vehicles to deal with them by setting up real-world scenarios in a controlled environment. We spoke with Waymo engineers to learn more about how.

Things can lurk near a dumpster

Parking lots may technically have stop signs, speed limits, and crosswalks, but drivers and pedestrians tend to do whatever they want in these environments. Shoppers carrying boxes might dart across an active driving route instead of using a crosswalk, carts can be left in the wrong place, and vehicles might drive the wrong way or over empty parking spots. “Parking lots are uniquely challenging from surface streets,” says Stephanie Villegas, who leads what Waymo calls its “structured testing” efforts. “They don’t really have standardized rules for how people should and can move about within them.”

“They’re just kind of lawless,” she adds.

Adding to the Wild-West vibe, social cues play an important role in ambiguous driving situations. If you're waiting for a parking spot to open up and see someone getting into a parked car, that person might wave to you to signal they're not going anywhere—or that space is indeed about to open up. Humans understand those signals intuitively, but self-driving cars need to be taught in different ways. "A self-driving car is not social," she says.

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