A video recording from the Uber self-driving car that struck and killed a woman on Sunday shows that she moved in front of it suddenly, a factor that investigators are likely to focus on as they assess the performance of the technology in the first pedestrian fatality involving an autonomous vehicle.

The Uber had a forward-facing video recorder, which showed the woman was walking a bike at about 10pm and came from a darkened centre median into traffic and "it's very clear it would have been difficult to avoid this collision in any kind of mode," Tempe, Arizona, police chief Sylvia Moir told the San Francisco Chronicle.

"The driver said it was like a flash, the person walked out in front of them," Moir said, referring to the back-up driver who was behind the wheel but not operating the vehicle. "His first alert to the collision was the sound of the collision."

Police later said in a statement that the department would defer to county prosecutors on whether to bring charges, but didn't dispute any of the information released by Moir.

In a news conference on Monday, Tempe police Sergeant Roland Elcock said local authorities had not come to any conclusions about who is at fault. Decisions on any possible charges will be made by the Maricopa County Attorney's office. Neither the victim nor the backup driver showed any signs of impairment.