The accident occurred when the driver of a second vehicle "failed to yield" to the Uber vehicle while making a turn, said Josie Montenegro, a spokeswoman for the Tempe Police Department.
"The vehicles collided, causing the autonomous vehicle to roll onto its side," she said in an email. "There were no serious injuries."
Two 'safety' drivers were in the front seats of the Uber car, which was in self-driving mode at the time of the crash, Uber said in an email, a standard requirement for its self-driving vehicles. The back seat was empty.
Photos and a video posted on Twitter by Fresco News, a service that sells content to news outlets, showed a Volvo SUV flipped on its side after an apparent collision involving two other, slightly damaged cars. Uber said the images appeared to be from the Tempe crash scene.
When Uber launched the pilot program in Pittsburgh last year, it said that driverless cars "require human intervention in many conditions, including bad weather." It also said the new technology had the potential to reduce the number of traffic accidents in the country.
The accident is not the first time a self-driving car has been involved in a collision. A driver of a Tesla Motors Inc Model S car operating in autopilot mode was killed in a collision with a truck in Williston, Florida in 2016. A self-driving vehicle operated by Alphabet Inc's Google was involved in a crash last year in Mountain View, California, striking a bus while attempting to navigate around an obstacle.
The collision comes days after Uber's former president Jeff Jones quit less than seven months after joining the San Francisco-based company, the latest in a string of high-level executives who have departed in recent months.
In February, Alphabet's Waymo self-driving car unit sued Uber and its Otto autonomous trucking subsidiary, alleging theft of proprietary sensor technology.