Self-driving cars are certainly on the way, but nobody knows when they will finally arrive. Google, considered by most to be the frontrunner, has said its plan is to commercialize self-driving cars by 2020. Many other players have said self-driving cars are just around the corner.

Uber CEO Travis Kalanick is not one of those players. Speaking at the annual TED conference in Vancouver this week, Kalanick said there’s been a lot of hype around self-driving cars, but that “it’s likely to take a lot longer” for them to hit the roads. He also said that when self-driving cars become reality, they won’t change the world overnight.

“It’s also going to be a long transition,” Kalanick said.”They will work in certain places and not in others.”

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Uber made a string of significant moves in 2015 that pointed to the development of self-driving taxis. Not only did Uber announce a self-driving car partnership with the University of Arizona, it raided the robotics lab at Carnegie Mellon and made several major hires that included former Google head of mapping Brian McClendon.

Self-driving taxis would certainly eliminate Uber’s top expense, its drivers, and that’s how Kalanick’s comments on the arrival of self-driving cars came about. TED’s Chris Anderson asked Kalanick what will happen to Uber’s drivers when self-driving cars arrive.

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“For us it is an interesting challenge,” Kalanick said. “The self-driving world is going to happen,” he added. “How do we optimistically lead through it? It is a world that is going to exist.”