The Information is reporting that the vehicle's onboard sensors likely did "see" Herzberg, but instead of correctly determining that she was an object that clearly needed to be avoided (either by applying the brakes or steering around the obstacle) it determined her to be a "false positive". As a result, the sensor suite acting as if she wasn't there and continued on its intended path (which tragically lead to the impact).
"Uber executives believe the company’s system was tuned so that it reacted less to such objects," writes The Information. "But the tuning went too far, and the car didn’t react fast enough, one of these people said."
While we can no doubt chalk this up a fatal error on the part of self-driving system, there was also a human failure as well. There was a human driver behind the wheel that should have been able to take over the controls in a situation just like this. However, as the onboard video showed, the "driver" wasn't even paying attention in the seconds leading up to the crash and was actually looking down and to the right. It is presumed that the human handler was either looking at the display screen in the dashboard or staring at a smartphone.
So, we have a case of the primary computer-aided collision detection system failing and the human backup failing as well. Add that to the fact that the pedestrian was not walking in a crosswalk at night, and there's a triple failure to contend with.
At this time, Uber is currently cooperating with investigators at the National Transportation Safety Board (NTSB). " Out of respect for that process and the trust we’ve built with NTSB, we can’t comment on the specifics of the incident," said a representative for Uber in a statement. "In the meantime, we have initiated a top-to-bottom safety review of our self-driving vehicles program, and we have brought on former NTSB Chair Christopher Hart to advise us on our overall safety culture."
It was reported back in late March that Uber's self-driving XC90s are actually using fewer LIDAR sensors than its previous fleet of autonomous Ford Fusion sedans (dropping from seven sensor to just one). "In scaling back to a single LIDAR on the Volvo, Uber introduced a blind zone around the perimeter of the SUV that cannot fully detect pedestrians," Reuters reported at the time. The XC90 also has seven cameras keeping an eye on everything go on around the vehicle, while the Fusion had 20.
Waymo, which is competing with Uber in the self-driving space, has said that its autonomous Chrysler Pacifica Hybrids would have never been involved in such an accident. “At Waymo, we have a lot of confidence that our technology would be able to handle a situation like that," said Waymo CEO John Krafcik.