Digitaltrends.com reporter Jeff Zurschmeide was aboard the van during the incident and described it in a web post.
"We had about 20 feet of empty street behind us (I looked) and most human drivers would have thrown the car into reverse and used some of that space to get away from the truck," Zurschmeide wrote. "Or at least leaned on the horn and made our presence harder to miss. The shuttle didn't have those responses in its program."
NTSB spokesman Chris O'Neil said the agency's investigation is its first of a collision involving a driverless car.
The investigation signals the NTSB's growing interest in the rapidly expanding use of automated systems in motor vehicles. In September, the NTSB issued a report critical of Tesla's semi-autonomous systems that allowed a driver in Florida to go for extended periods without putting his hands on the steering wheel. The Tesla Model S, which was steering itself, slammed into the side of a truck in Florida in 2016, killing the driver.
While citing the actions of the two drivers as the primary cause, the safety board ruled that Tesla's Autopilot design also contributed to the accident. Even though the car could be used for extended periods without human intervention, it was not designed to stop if a truck was crossing in front of it, the agency's report concluded.
The agency also recommended that vehicle manufacturers and federal regulators take steps to ensure that more advanced automation isn't used in situations it's not designed for.
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