Ronald De Feo has watched robots take factory jobs for years. Now he sees them threatening a new class of worker: People who drive for a living.

“I am in Pittsburgh; it’s a test market for Uber’s autonomous vehicle,” says De Feo, CEO of the industrial materials firm Kennametal. “We see all these (automated) Ubers running around the streets of Pittsburgh, a confusing and difficult place to navigate. If they can make that work, what do you think happens to the job of being a taxi driver?”

Computer scientists and economists say the threat isn’t merely theoretical: Automated cars pose an existential threat to the many Americans who drive for a living: 2.9 million truckers and delivery drivers, 674,000 bus drivers, 181,000 cab drivers and chauffeurs.

The big question is how long it will take auto and tech companies to clear the technical hurdles to turning the streets over to driverless cars.

“I don’t see herds of robotic trucks running down the highway in the next few years,” says Vern Meyerotto, a 61-year-old truck driver in Denver. “There’s an awful lot of development that needs to be done on it.”

Meyerotto, who’s been driving since 2007, points to the self-driving Tesla Model S car that crashed in May, killing the driver, after the car’s cameras failed to detect a tractor-trailer crossing its path. He doesn’t expect to see robotic trucks doing much driving for 10 or 15 more years.