Autonomous shuttle collision blamed on human error

On its first day of service in the first U.S. deployment of an autonomous shuttle carrying passengers in live traffic, the vehicle cruising downtown Las Vegas bumped into a tractor-trailer that was backing into an alley. The National Transportation Safety Board has determined that the fender-bender occurred because the truck driver and shuttle attendant both expected the autonomous vehicle to stop.

The NAVYA Arma shuttle was carrying seven passengers and an attendant on November 8, 2017, on a defined 0.6-mile loop when it came upon a tractor towing a refrigerated trailer. The truck driver told investigators he saw the shuttle approaching as he began to back into the alley.

The shuttle’s electronic devices spotted the truck too, NTSB wrote in its report. “The shuttle’s sensor system detected the truck at 147.6 feet and tracked the truck continuously while it backed up. The shuttle, which was programmed to stop 9.8 feet from any obstacle in its path, began to decelerate at a distance of 98.4 feet from the truck. When the shuttle was 10.2 feet from the truck and at nearly a complete stop, the attendant pressed one of the emergency stop buttons.”

As the truck completed turning while backing into the alley, however, its right front tire “caused minor damage to the lower left front of the shuttle’s body and a minor abrasion to the truck’s tire. The shuttle passengers, the attendant, and the truck driver were uninjured. The shuttle and the combination vehicle remained in service after the collision,” the report explained.

The truck driver “said that he knew the shuttle was automated and had seen it doing test runs. He said that he had no concerns about sharing a road with the shuttle. He stated that he assumed the shuttle would stop a ‘reasonable’ distance from the truck.”

Government investigators were told, “The shuttle could operate autonomously only on a predetermined path, on a route that had been fully mapped. As a vehicle designed primarily for autonomous operation, the shuttle did not have a steering wheel, a brake, or an accelerator pedal. Its design permitted manual operation, however, using a hand-held controller. The highest speed at which the shuttle was allowed to operate at the time of the crash was 16 mph.”

The controller, which looked like a video game controller, was used by the shuttle attendant to “load the shuttle on and off a tow truck (to take it to and from its route location), to maneuver the shuttle in the yard where it was stored, and to pull the shuttle into parking spaces. The attendant could also intervene and operate the shuttle manually if an obstacle blocked its path (the shuttle could not deviate outside its designated path, for example, to go around a stopped vehicle).”

As the shuttle approached the truck seconds before the collision, the attendant stopped it by pressing an emergency button by a door, the report stated. “Before the crash, the controller was stored in an enclosed space at one end of the passenger compartment. After the crash (the operator) put in place a new company policy to make the controller more accessible. Attendants were now to remove the controller from its storage space at the beginning of a trip and keep it available throughout the trip.”

The shuttle’s technology included eight lidar (light detection and ranging) sensors, two stereoscopic cameras, a differential global positioning system, an inertial measurement unit, a dedicated short-range communication system and a long-term evolution antenna that communicated with traffic signals. NAVYA could monitor the shuttle’s performance in real time from its control center in Lyon, France, by observing the vehicle telematics or viewing video from the shuttle’s cameras.

The National Transportation Safety Board determined that the probable cause of the collision was the truck driver’s expectation that the shuttle would stop at a sufficient distance from his vehicle. A contributing cause was the attendant’s inability to take manual control of the vehicle in an emergency.

During the year-long pilot, the shuttle operated for 1,515 hours and carried 32,827 riders.

“The NTSB would normally not investigate a minor collision, but the involvement of a highly automated vehicle warranted having our investigators examine the circumstances surrounding the collision,” said Kris Poland, deputy director of the NTSB’s Office of Highway Safety.


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