(Reuters) - The back-up safety driver behind the wheel of a self-driving Uber Technologies Inc. test vehicle that struck and killed a woman in Tempe, Arizona, in 2018 was charged with negligent homicide, prosecutors said on Tuesday.

Rafael Vasquez, age 46, who is also known as Rafaela, pleaded not guilty on Tuesday after being charged in the death of Elaine Herzberg on Aug. 27, court records show. She was released pending trial set for February 2021.

Ms. Herzberg died after she was struck while walking a bicycle across a street at night. The first recorded death involving a self-driving vehicle prompted significant safety concerns about the nascent autonomous vehicle industry.

Uber declined comment. A lawyer for Ms. Vasquez did not immediately respond to a request to comment.

A Tempe police report said Ms. Vasquez was repeatedly looking down instead of keeping her eyes on the road. Prosecutors in March 2019 said Uber was not criminally liable in the crash.

“Distracted driving is an issue of great importance in our community,” said Maricopa County Attorney Allister Adel. "When a driver gets behind the wheel of a car, they have a responsibility to control and operate that vehicle safely."

Police said previously the crash was "entirely avoidable" and that Ms. Vasquez was streaming "The Voice" TV program at the time of the crash.

In November, the National Transportation Safety Board (NTSB) faulted Ms. Vasquez's inactions and Uber for inadequate attention to safety and decisions in the company's autonomous vehicle development.

The NTSB said the probable cause was Ms. Vasquez's failure to monitor the driving environment “because she was visually distracted throughout the trip by her personal cell phone." She was supposed to act in the event of an emergency. Uber made a series of development decisions that contributed to the crash's cause, the NTSB said. The software in the modified Volvo XC90 did not properly identify Ms. Herzberg as a pedestrian and did not address "operators’ automation complacency."

Uber deactivated the automatic emergency braking systems in the Volvo XC90 vehicle and precluded the use of immediate emergency braking, relying instead on the back-up driver.