Video of a fatal crash involving a self-driving Uber suggests the pedestrian who was killed should have been within range of the car's laser and radar sensors, two experts have said.
Authorities investigating the crash in a Phoenix suburb released video of the Uber SUV that cuts out just before the woman was struck as she walked from a darkened area onto a street.
The second part of the video shows the reaction of the driver filmed from inside the car.
Tempe Police Chief Sylvia Moir has said the SUV would probably not be found at fault, but two experts who viewed the video said the SUV's sensors should have spotted the 49-year-old woman and her bicycle in time to brake.
They said it appears there was enough time and distance to avoid the collision.
The lights on the SUV did not illuminate 49-year-old Elaine Herzberg until a second or two before impact, raising questions about whether the vehicle could have stopped in time.
The crash on Sunday night in Tempe was the first death involving a full autonomous test vehicle.
The Volvo was in self-driving mode with a human back-up driver at the wheel when it struck Ms Herzberg, police said.
The video shows the human back-up driver looking down until seconds before the crash. The driver looks up and appears startled in the last moment of the clip.
Bryant Walker Smith, a University of South Carolina law professor who studies autonomous vehicles, said: "The victim did not come out of nowhere. She's moving on a dark road, but it's an open road, so Lidar (laser) and radar should have detected and classified her" as a human.
Mr Smith said the video may not show the complete picture, but "this is strongly suggestive of multiple failures of Uber and its system, its automated system, and its safety driver".
Sam Abuelsmaid, an analyst for Navigant Research who also follows autonomous vehicles, said laser and radar systems can see in the dark much better than humans or cameras and that Ms Herzberg was well within the range.
"It absolutely should have been able to pick her up," he said. "From what I see in the video it sure looks like the car is at fault, not the pedestrian."
Mr Smith said the Uber driver appears to be relying too much on the self-driving system by not looking up at the road.
"The safety driver is clearly relying on the fact that the car is driving itself. It's the old adage that if everyone is responsible no one is responsibl.
"This is everything gone wrong that these systems, if responsibly implemented, are supposed to prevent."
The experts were unsure if the test vehicle was equipped with a video monitor that the back-up driver may have been viewing.
Uber immediately suspended all road-testing of such cars in the Phoenix area, Pittsburgh, San Francisco and Toronto.
The National Transportation Safety Board, which makes recommendations for preventing crashes, is investigating the crash.
An Uber spokeswoman did not answer specific questions about the video or the expert observations.
"The video is disturbing and heartbreaking to watch, and our thoughts continue to be with Elaine's loved ones. Our cars remain grounded, and we're assisting local, state and federal authorities in any way we can," the company said in a statement.