SAN FRANCISCO — No one knows what the future of self-driving cars will look like, or how long it will take to get there. But every major player in the field is striking partnerships to be ready for the day when autonomous vehicles finally become mainstream.

That includes Uber, which on Monday announced a new deal with Volvo. Under the agreement, Uber plans to purchase as many as 24,000 self-driving Volvos once the technology is production-ready, putting the vehicles into its extensive ride-hailing network.

“Everything we’re doing right now is about building autonomous vehicles at scale,” Jeff Miller, Uber’s head of automotive alliances, said in an interview. “We don’t know exactly how an autonomous world will look. But we know that we want to be the platform that’s at the center of it, from a ride-sharing standpoint.”

The deal is an extension of an agreement Uber made with Volvo nearly two years ago, when the ride-hailing company started its research and development efforts in autonomous vehicles in earnest. Uber has worked with third-party component manufacturers to build software and hardware for driverless cars, then worked closely with Volvo to outfit the automaker’s XC90 vehicles with the technology.