Uber's autonomous test vehicles were involved in 37 crashes in the 18 months before a fatal March 2018 self-driving car accident, the National Transportation Safety Board (NTSB) said on Tuesday.

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

In one incident, the test vehicle struck a bent bicycle lane bollard that partially occupied the test vehicle's lane of travel. In another incident, the operator took control to avoid a rapidly approaching oncoming vehicle that entered its lane of travel. The vehicle operator steered away and struck a parked car. The NTSB will hold a probable cause hearing on the crash November 19. 

A spokeswoman for Uber's self-driving car effort, Sarah Abboud, said the company regretted the crash that killed Elaine Herzberg and noted it has "adopted critical program improvements to further prioritize safety. We deeply value the thoroughness of the NTSB's investigation into the crash and look forward to reviewing their recommendations."

The crash was the first death attributed to a self-driving vehicle, prompting significant safety concerns about the nascent self-driving car industry, which is working to get vehicles into commercial use. 

The NTSB said previously Uber had disabled an emergency braking system in the modified Volvo test vehicle. 

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

NTSB said Uber conducted simulation of sensor data from the crash with the revised software and told the agency that "the new software would have been able to detect and correctly classify the pedestrian at a distance of approximately 88 meters – 4.5 seconds – before the original time of impact."

NTSB added, "The system would have initiated controlled braking more than four seconds before the original time of impact."

In March, prosecutors in Arizona said Uber was not criminally liable in the self-driving crash. In July, police in Tempe closed a street to conduct a lighting test as it investigated whether the Uber 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.