The nation's first pedestrian death involving an autonomous vehicle may have been unavoidable, according to local authorities, although the National Transportation Safety Board (NTSB) investigation into the incident continues.

The accident occurred Sunday night around 10 p.m., when 49-year-old Elaine Herzberg was struck by an Uber self-driving vehicle as she walked across a busy street outside of a crosswalk.

The Volvo, which was in autonomous mode when it struck Herzberg, is part of the company’s self-driving fleet. The vehicle did have a backup operator behind the wheel, 44-year-old Rafaela Vasquez.

The NTSB’s investigation will address the operating condition of the vehicle, driver interaction with the vehicle and opportunities for the vehicle or driver to detect of the pedestrian.

The agency says its investigative team will be in the Tempe area for the remainder of the week. On its “to do” list:

• Meeting with representatives of Uber, the National Highway Traffic Safety Administration and the Tempe Police Department
• Examining the accident vehicle, a Volvo XC90 and the accident site
• Viewing a copy of a video that captured the crash from an aftermarket dash camera mounted in the test vehicle
• Gathering information about the technology on the test vehicle
• Collecting information about the pedestrian and the safety driver
• Beginning collection of any and all electronic data stored on the test vehicle or transmitted to Uber

According to news reports, Tempe police said preventing the accident would have been difficult whether the car was in either autonomous or human-driven mode, based on how the victim emerged from the shadows onto the roadway.

The Volvo was traveling five miles over the area’s 35 mph speed limit. After the accident, Uber suspended its self-driving car operations in Phoenix, San Francisco, Pittsburgh and Toronto.