Apparently, the trucker thought the shuttle would stop at a "reasonable" distance from the truck. Although the shuttle began to slow down to 98.4 feet, it is not programmed to stop until 9.8 feet from obstacles. The attendant pressed the emergency stop button when the vehicle was 10.2 feet from the truck, but this was clearly not enough to prevent the incident.
During an interview with the investigators, the supervisor stated that they were considering switching to manual mode to move the shuttle, but that they did not have easy access to his portable controller. You see, Las Vegas standalone shuttles operate on a pre-determined route, but attendants could use a controller to activate the horn and switch to manual mode. When the accident occurred, the controller was stowed in a confined space at one end of the cockpit. After the incident, the operator started asking attendants to take the controller out of storage at the beginning of the trip and keep it accessible at all times.
The NTSB made it clear that it did not normally investigate minor collisions, but that the involvement of an automated vehicle deserved to be examined more closely. In light of the events, the agency will also continue to closely monitor automated vehicle testing. He wrote in the incident report:
"Pilot tests of highly automated vehicles on public roads are underway in various locations in the US The NTSB will monitor the evolution of these vehicles to better understand their potential safety implications and unintended consequences."