An Uber autonomous SUV that hit and killed a pedestrian in Arizona in March registered the woman on its sensors about six seconds before hitting her, but the car’s emergency braking was disabled, the NTSB said in a preliminary report issued Thursday. The SUV’s safety operator, in the car for the test drive, would have been expected to intervene in such a situation.
The system had a fatal flaw, however. Its design doesn’t cause it to alert the safety driver to the presence of the pedestrian. The March 18 crash during the test in Tempe, Ariz., killed 49-year-old Elaine Herzberg as she crossed the street in front of the vehicle in the middle of the block, while walking a bike.
The NTSB’s report said the Volvo-manufactured SUV’s LIDAR and radar systems recorded observations of the victim about six seconds before impact as the car was going 43 mph, just below the posted 45 mph speed limit. The car’s software noted the presence first of an unknown object, then as a “vehicle” and then as a bicycle, and included several possible expectations of a future travel path for the object. Just before the collision, the system determined that emergency braking would be needed to mitigate a collision.
“According to Uber, emergency braking maneuvers are not enabled while the vehicle is under computer control, to reduce the potential for erratic vehicle behavior,” the NTSB said. “The vehicle operator is relied on to intervene and take action. The system is not designed to alert the operator.”
“The self-driving system data showed that the vehicle operator intervened less than a second before impact by engaging the steering wheel,” the report continued. “The vehicle speed at impact was 39 mph. The operator began braking less than a second after the impact. The data also showed that all aspects of the self-driving system were operating normally at the time of the crash, and that there were no faults or diagnostic messages.”
Uber’s CEO, Dara Khosrowshahi, has said that while the crash was tragic, the company ultimately believes autonomous vehicles will be much safer than those driven by people.
The report noted several other environmental factors that contributed to the crash. The roadway wasn’t well lit, and the median of the roadway, from which Herzberg emerged, was obscured by shrubbery. Herzberg was crossing in the middle of a block, and either didn’t see or ignored signs warning pedestrians not to cross there, but to use the crosswalk about 350 feet away. Toxicology reports for the victim were positive for methamphetamine and marijuana.
“All aspects of the crash remain under investigation as the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar crashes,” the NTSB said. Uber and Volvo are cooperating in the investigation.