Uber would not share financial information about the project, and Volvo did not immediately respond to a request for further comment.
Uber and competitors like Lyft ultimately hope to take the driver out of their vehicles since that is the single largest component in cost of a ride.
Uber agreed to use 100 XC90s for self-driving tests in Pittsburgh, while also striking a deal to include autonomous vehicles from Daimler AG's Mercedes-Benz in its network at some point.
Jeff Miller, Uber's head of auto partnerships said: "In a self-driving world there is no human, so you need redundant steering and braking and actuation systems, such that if there is an electrical or mechanical failure, the back-up system can kick in".
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Uber previously launched a self-driving Uber service in San Francisco in December 2016 but was pulled shortly after because the company failed to properly register the 16 vehicles.
The new XC90s that Uber is sourcing from Volvo will be more advanced in their self-driving abilities compared to the existing test cars.
Volvo Cars' worked with Uber to develop the SUVs to be supplied to Uber. The exact terms of the deal weren't initially disclosed, but an Uber spokesperson confirmed to Mashable via email that the fleet size will be around 24,000 vehicles.
"The issue is that we don't have any legislation in any city of the world that would remotely allow this sort of thing to happen at the moment", said Paul Newton, director at the consultancy IHS Automotive, about the idea of a totally driverless taxi service.
Uber, which didn't put a time frame on when it might introduce driverless rides, said its approach means anyone in the industry can "deploy its tech".