In March 2018, a Volvo XC90 equipped with Uber autonomous technology hit and killed a pedestrian, 49-year-old Elaine Herzberg, in Arizona. Since then, it took nine months for the company’s autonomous fleet to get back on the road, and, according to head of Uber Advanced Technologies Group Eric Meyhofer, they have implemented a series of changes to improve the safety of its self-driving vehicles.

However, according to CNBC, it has now emerged that Uber’s prototypes were implicated in a quite high number of incidents preceding the one in Arizona. The National Transportation Safety Board (NTSB) said on Tuesday, November 5, that Uber Technologies autonomous test vehicles were involved in 37 crashes in the 18 months before the March 2018 accident.

In particular, the board said between September 2016 and March 2018, there were 37 crashes of Uber vehicles operating in autonomous mode at the time, including 33 that involved another vehicle striking said 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, the operator took control to avoid a rapidly approaching oncoming vehicle that entered its lane, steered clear but, unfortunately, struck a parked car. The NTSB will hold a probable cause hearing on the crash on November 19.

Also Read: Uber And Volvo Unveil Production-Ready, Fully Autonomous XC90

As for the fatal accident, the Yavapai County Attorney declared that there was no basis for criminal liability against Uber. The Attorney’s Office examined the case at the request of Maricopa County, where the accident happened, but hasn’t explained the reasoning behind their decision.

Prosecutors did say that the back-up driver behind the wheel of the semi-autonomous vehicle, Rafaela Vasquez, should be referred to the Tempe police for additional investigation. The Yavapai County Attorney’s Office has also called for further expert analysis of video from the crash to determine what Vasquez would have been able to see.

Uber has declined to comment about the prosecutor’s decision. However, the ride-hailing company still has a number of federal inquiries, lawsuits, and other things to deal with, as both the National Transportation Safety Board and National Highway Traffic Safety Administration continue to investigate the fatal accident.