Federal safety investigators say the autonomous Uber SUV that struck and killed an Arizona pedestrian in March spotted the woman about six seconds before hitting her, but didn't slow down because the vehicle's built-in emergency braking feature was disabled.
In a preliminary report on the crash, the National Transportation Safety Board said Thursday that emergency braking maneuvers are not enabled while Uber's cars are under computer control. That's a measure designed "to reduce the potential for erratic vehicle behavior," the NTSB said.
Instead, Uber's autonomous driving system "relies on an attentive operator to intervene if the system fails to perform appropriately during testing." The system is not designed to alert the driver.
In the crash, the driver of the Volvo XC-90 SUV began steering less than a second before impact but didn't brake until less than a second after impact, according to the preliminary report, which does not determine fault.
A video of the crash showed the driver looking down just before the vehicle struck and killed 49-year-old Elaine Herzberg in Tempe, Arizona.
San Francisco-based Uber said in a statement it has worked closely with the NTSB and is doing an internal review of its self-driving vehicle program. The company also has brought in former NTSB Chairman Christopher Hart "to advise us on our overall safety culture, and we look forward to sharing more on the changes we'll make in the coming weeks."
The NTSB report comes a day after Uber pulled its self-driving cars out of Arizona, eliminating the jobs of about 300 people who served as backup drivers and performed other jobs connected to the vehicles. Uber had suspended testing of its self-driving vehicles in Arizona, Pittsburgh, San Francisco and Toronto while regulators investigated the cause of the March 18 crash.
Sensors on the fully autonomous Volvo spotted Herzberg while the car was traveling 43 mph and determined that braking was needed 1.3 seconds before impact, according to the report.
Herzberg was pushing a bicycle across a boulevard in the darkness when the crash occurred on a part of the road that had no crosswalk and was not lighted, the report said. The speed limit at the crash site was 45 mph.
She was wearing dark clothing and did not look in the direction of the vehicle until just before impact. A toxicology report showed that she tested positive for methamphetamine and marijuana, according to the NTSB.
Also, the bicycle had no side reflectors and the front and back reflectors were perpendicular to the Uber SUV.
In an interview with the NTSB, Uber's backup driver said she had been monitoring the "self-driving interface." While her personal and business telephones were in the vehicle, she said neither was in use at the time of the crash. The agency said that although the driver was not tested for alcohol or drug use immediately after the incident, police reported she showed no signs of impairment.
The agency, which can make safety recommendations to other federal agencies, said information in the preliminary report can change as the investigation progresses and that no conclusions should be drawn from the report.
The NTSB preliminary report doesn't provide "any decisive findings or conclusions," said Daniel Scarpinato, spokesman for Arizona Gov. Doug Ducey. "We await the more thorough and final investigative report. Uber's self-driving vehicle suspension remains in place."