Uber's self-driving Volvo SUV, which observed Herzberg six seconds before the crash, didn't know "what" she was at first. The software originally classified her as an unknown object, then a vehicle, then a bicycle, the report said. At 1.3 seconds before the crash, the self-driving system realized emergency braking was needed to prevent a crash. But Uber had disabled the feature to reduce the potential for unwanted braking, such as for a plastic bag in the road. Some self-driving car companies use teams of two in their test vehicles. A person behind the wheel monitors the road, and someone in the passenger seat takes notes on a laptop.

http://money.cnn.com/2018/05/24/technology/uber-arizona-self-driving-report/index.html