An Uber self-driving test vehicle that struck and killed an Arizona woman in 2018 had software flaws, according to a US agency's report which also reveals the company's autonomous test vehicles were involved in multiple crashes in the 18 months prior to the incident.

Key points: The report says the vehicle failed to identify the woman as a pedestrian as she was crossing a street with her bike

The report says the vehicle failed to identify the woman as a pedestrian as she was crossing a street with her bike The NTSB said in the 18 months prior to the incident Uber's self-driving vehicles crashed 37 times

The NTSB said in the 18 months prior to the incident Uber's self-driving vehicles crashed 37 times Thirty-three of those incidents involved other vehicles striking the self-driving vehicles

The National Transportation Safety Board (NTSB) will meet on November 19 to determine the probable cause of the March 2018 accident in Tempe, Arizona that killed 49-year-old Elaine Herzberg as she was walking a bicycle across a street at night.

In a report released ahead of the meeting, the NTSB said the Uber Technologies Inc vehicle had failed to properly identify her as a pedestrian crossing a street.

That accident prompted significant safety concerns about the nascent self-driving car industry, which is working to get vehicles into commercial use.

The independent US Government agency may use the findings from the first fatal self-driving car accident to make recommendations that could have an impact on how the entire industry addresses self-driving software issues or to regulators about how to oversee the industry.

In the aftermath of the crash, Uber suspended all testing and did not resume until December last year, in Pennsylvania with revised software and significant new restrictions and safeguards.

A spokeswoman for Uber's self-driving car effort, Sarah Abboud, said the company regretted the crash that killed Herzberg and noted it had "adopted critical program improvements to further prioritise safety".

"We deeply value the thoroughness of the NTSB's investigation into the crash and look forward to reviewing their recommendations," she said.

The NTSB reported at least two prior crashes in which Uber test vehicles may not have identified roadway hazards.

The NTSB said between September 2016 and March 2018, there were 37 crashes of Uber vehicles in autonomous mode, including 33 that involved another vehicle striking test vehicles.

Recommendations from the report could affect how regulators oversee the use of self-driving vehicles. ( Reuters: Natalie Behring, file )

In one incident, the test vehicle struck a bent bicycle lane post that partially occupied the test vehicle's lane of travel.

In another incident, the operator took control to avoid a rapidly approaching vehicle that entered its lane of travel.

The vehicle operator steered away and struck a parked car.

The NTSB said Uber conducted simulations of sensor data from the Arizona crash with the revised software and told the agency the new software would have been able to detect the pedestrian 88 metres or 4.5 seconds before impact.

The car's system would have started to brake four seconds before impact.

Vehicle identified bicycle too late to avoid the crash

In the actual accident, the test vehicle did not correctly identify the bicycle as an imminent collision until 1.2 seconds before impact.

Police say the driver was looking down and streaming The Voice just moments before the crash. ( Supplied )

It was too late for the Uber car to avoid the crash.

"The system design did not include a consideration for jaywalking pedestrians," the NTSB said in a statement.

The Uber car also initiated a one-second delay of planned braking while the vehicle calculated an alternative path or to allow the safety driver to take over.

Uber has since discontinued that function as part of its software update.

The NTSB said during its investigation it "communicated several safety-relevant issue areas [to Uber] that were uncovered during the course of the investigation".

In March, prosecutors in Arizona said Uber was not criminally liable in the self-driving crash.

Police investigated whether the safety driver who was behind the wheel and supposed to respond in the event of an emergency should face criminal charges.

Police have said the crash was "entirely avoidable" and that the backup driver was watching The Voice TV program at the time of the crash.

Reuters