The National Transportation Safety Board (NTSB) has wrapped up a more than year-long investigation into a low-speed crash between a self-driving shuttle and a delivery truck in Las Vegas on November 8th, 2017. The agency determined two main probable causes for the accident: the truck driver’s assumption that the shuttle would move to avoid him, and that the safety operator inside the shuttle didn’t have direct access to the manual override controls.

That the truck driver was somewhat to blame jives with the immediate descriptions of the crash, which happened on the shuttle’s first day of operation. On that day, a Las Vegas government official described the truck grazing the stopped shuttle as it backed into an alley, which is ultimately what the NTSB found in its investigation.

At the time of the crash, the policy was to keep the manual controller locked away

But the NTSB found that the safety operator inside the shuttle and at least one of the eight passengers were well aware that the truck was about to make contact. The problem was the operator had no immediate access to the manual controls for the shuttle, which came in the form of an Xbox controller.

At the time of the crash, the policy of operator Keolis was to lock that controller away in a storage compartment on the shuttle during rides. If the operator had been able to quickly access the controller he could have moved the shuttle out of the way of the truck, or at the very least triggered the horn to let the driver know that he was about to crash.

Instead, the nine people inside the shuttle were left to watch the crash play out in super-slow motion. “Oh, he’s gonna hit you,” one passenger said according to the NTSB report. The safety operator struck the shuttle window, waved his hands, and yelled “stop,” to no avail. A few seconds later, the same passenger said “Oh, he can’t see this,” and then the truck’s wheel clipped the front left corner of the shuttle.

“Oh, he’s gonna hit you.”

The NTSB says Keolis changed this policy after the crash, and that the Xbox controller was readily available during each subsequent trip across the rest of the year-long Las Vegas pilot.

The shuttle otherwise did slow down for the truck blocking its path, and would have stopped on its own if the operator hadn’t hit the emergency stop button himself, the NTSB found. After all, it was on a very simple route that only included four right turns, and one that had been mapped and plotted ahead of the trial.

The operator said he “considered” reaching for the manual controls, but ultimately didn’t believe he had enough time. “Things happened very fast. Even though he’s backing up slowly, there were a lot of things going through my mind,” he told investigators. “[M]y main thought or my initial focus was I need to get the shuttle stopped.”

The truck driver, meanwhile, did see the shuttle coming. But he told investigators that, after he saw it coming toward him, he figured it was a “reasonable assumption” that the shuttle “would stop a reasonable distance from a backing tractor trailer.” So he turned away to keep an eye on a crossing pedestrian. When he made his next move, he scraped the shuttle.

“I figured the thing was in control,” he told investigators. “I figured they must have had the thing worked out; [that] it was going to function fine. I figured someone could stop it if need be.”

The Las Vegas pilot, which was done in partnership with AAA, was billed as the first such autonomous shuttle test in live traffic in the country. The shuttle was made by a company called Navya, and operated by Keolis. Since then, a number of different companies have offered similar pilots around the country.