An Uber self-driving car that struck and killed a woman last year in Arizona failed to recognise her as a pedestrian because she was jaywalking, United States transport regulators said on Tuesday.

The woman had been crossing the street "at a location without a crosswalk; the system design did not include a consideration for jaywalking pedestrians," the US National Transportation Safety Board (NTSB) said in a statement.

In a preliminary report, the NTSB had already determined that the car's software spotted the 49-year-old woman nearly six seconds before the vehicle hit her, as she walked across the street at night with her bicycle in Tempe, a suburb of Phoenix.

According to the latest report, which was issued ahead of a November 19 hearing to officially determine the accident's cause, the system at no time "classified her as a pedestrian" but rather, considered her an object.

When the software determined that a collision was imminent approximately 1.2 seconds before impact, it suppressed any "extreme braking or steering actions" to reduce the potential for erratic vehicle behaviour.

It did, however, produce "an auditory alert to the vehicle operator as it initiated a plan for the vehicle slowdown".

Following the March 2018 accident, Uber suspended its autonomous driving testing in all locations in the US but resumed the program several months later.

The company has assured the NTSB that new technology in the cars will correctly recognise pedestrians in similar situations and trigger braking more than four seconds before impact.

According to the report, 37 crashes involving Uber automatic test vehicles operating in autonomous mode occurred between September 2016 and March 2018, excluding the Arizona crash.