The autonomous vehicle involved in a fatal crash in Arizona had its emergency braking system disabled according to a report by the US National Transportation Safety Board (NTSB).
The report also found that the modified 2017 Volvo XC90 included a number of driver assistance functions that were disabled while the vehicle was in computer control mode.
The data obtained from the self-driving system in the vehicle detailed the events of the crash:
- The self-driving system first registered radar and lidar observations of the pedestrian about six seconds before impact.
- The vehicle was travelling at approximately 39mph (63kph) upon impact.
- The system first classified the pedestrian as an unknown object, a vehicle and then as a bicycle.
- At 1.3 seconds before impact, the system determined that emergency braking was needed to mitigate a collision.
- Emergency braking manoeuvres are not enabled when the vehicle is under computer control to mitigate potential erratic vehicle behaviour.
- The vehicle operator engaged the steering wheel less than a second before impact and began braking less than a second after the impact.
The report revealed that the systems were not designed to alert the operator but relied on the driver to intervene and take action in potential emergency situations.
The NTSB stated that it was continuing to investigate the incident to determine probable causes.