“Self-driving cars are here,” Dmitri Dolgov told the audience at MIT Technology Review’s EmTech Digital event this week. “It's not a matter of when or if. It’s a matter of how fast we can grow and how fast we can scale this technology in a responsible manner.”

Waymo’s CTO is right: The outfit that started off as Google’s self-driving car project is running a limited robotaxi service in the Phoenix metro area. (The company still uses safety drivers, so the cars aren’t yet totally driverless. Dolgov also told the audience that the company has tech yet to crack.) And it’s not alone. GM Cruise plans to launch a service this year. Uber is testing in Pittsburgh. Lyft and Aptiv have a limited self-driving service in Las Vegas. Nuro’s delivery bots are hauling groceries around Texas and Arizona. May Mobility is running robo-shuttles in Detroit.

So for the public sharing the roads with these things, a few long lurking questions are now more pressing than ever: How do we know these things are safe? The companies say they are, but how can they prove it to us?

One thing is for sure: The way we certify human drivers ain’t going to cut it. Just because software can pull off a three-point turn once doesn’t mean it will be able to do it every time, in variable conditions. Or that the people who built it even know why it worked. Algorithms are black boxes; developers can see whether a computer is doing something right, but they can’t necessarily tell if the computer understands why it’s right. If something goes wrong with self-driving software, though, researchers are going to need to understand how it works—so they can fix it.

A different sort of test, then, is in order. One made not for people, but for machines. That’s why some people in the self-driving space are talking about setting a new kind of standard.

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For decades, engineers who build anything, including software, have used standards to verify the quality of their work. Whether those standards are voluntary or government mandated, they’re less rules for what to do than processes for making sure that what you do works. Underwriters Laboratory, based in Illinois, writes standards and certifies that companies are following them for just about any product you can think of: outdoor furniture, horticultural lighting and grow systems, armored cables, robotic equipment, factory-built fireplaces, tin-clad fire doors. Check your favorite American electronic product or appliance and chances are you’ll find a safety certification stamp from Underwriters or a similar organization. (If you don’t, maybe rethink your choice.) Another group called the International Organization of Standards came out with a new standard called ISO 26262 eight years ago, which outlines safety in electrical or electronic car systems.

But no one has made this kind of standard, this variety of test, for a self-driving car. Underwriters Laboratories and a safety software company called Edge Case Research would like to change that, and quickly. They have a plan to bring together all sorts of players in this budding industry to do what others have done for automotive software and those tin-clad fire doors. The groups plan to write a new safety standard for autonomous products called—and this just rolls off the tongue—UL 4600.

Right now, UL 4600 is a draft, written by collaborators with backgrounds in standards writing and aviation and automotive software tech. To make the final version, they need to bring together a “supergroup” panel of advisers. They’d like to do that this spring.

“I have a balance of interests that I look for,” says Deborah Prince, the standards process manager for Underwriters Laboratories. She has put together many advisory panels for the standards that the company oversees. “I’m looking for my producers, I might have software people in there, insurance people, regulators. I want the right cross section.” For a self-driving software standard, that cross section might be made up of big developers like Waymo and Uber, small self-driving startups, independent researchers, car companies, and maybe even a few staffers from the Department of Transportation.