The basic elements of the collision between a driverless shuttle bus and a human-driven delivery truck this week in Las Vegas are straightforward.
According to police officers, a passenger, and officials from the company which manages the bus, the eight-passenger electric shuttle detected the truck in its path and yielded. It came to a complete stop. The truck continued backing up and struck the left-front side of the stationary bus. If this had been an everyday fender bender, that’d be the end of the story.
But because the minor crash involved a vehicle operating under the control of a self-driving system, the broader circumstances of Wednesday’s scrape have received considerable scrutiny and raised questions about how self-driving cars and human motorists interact on public roads.
Even though no injuries were reported and the shuttle resumed service Thursday morning, officials from the National Transportation Safety Board (NTSB), the federal agency tasked with examining major crashes and issuing safety recommendations, said Friday it will dispatch investigators to review the crash. The board’s interest and involvement underscore the importance of learning more about the safety of autonomous technology as automakers and tech companies ramp up testing and deployment.
The shuttle performed exactly how it’s designed.
– Chris Barker, Keolis
Chris Barker, senior vice president of new mobility at Keolis, the mass-transit company which owns and manages the affected shuttle, told Car and Driver that company engineers conducted a review of vehicle data recorded by onboard sensors before clearing it for service. He said the self-driving system, built by French manufacturer Navya, worked as expected and that no changes were made to its control algorithms before operations resumed.
“The shuttle performed exactly how it’s designed,” Barker said. “If there’s an object impeding its path, it will brake, stop, and yield to the moving object. Unfortunately, in this case it was a situation where there was the truck in front and traffic behind. You can only move so much. And the truck kept moving and made contact.”
Traffic investigators from the Las Vegas Metropolitan Police Department issued a misdemeanor citation to the truck driver for unsafe backing, according to Laura Meltzer, a police information officer with the department. She said a formal crash report on the incident is expected to be released next week.
Timing of the incident couldn’t have been worse. The shuttle commenced what’s expected to be a yearlong pilot project roughly 45 minutes before the collision occurred. Dignitaries including Las Vegas mayor Carolyn Goodman, magicians Penn & Teller, and race-car driver Danica Patrick all attended a ceremony that celebrated the arrival of the fully autonomous shuttle, which is the first of its kind to carry ordinary passengers on public roads in the United States.
Unlike most traffic crashes, which happen in fractions of a second, witnesses say this incident played out in slow motion. The shuttle came upon the truck, which was splayed across the road at an angle as its driver attempted to back into a nearby alley. Jeff Zurschmeide, a writer for Digital Trends, who was aboard at the time of the crash, said the truck’s trailer narrowly missed the shuttle. But shuttle occupants could foresee an imminent collision as the truck’s cab swung wide and its right tire moved rearward.
“The poor attendant is banging on the windows in the shuttle, yelling, ‘Hey! Hey!’ But it wasn’t going to help.”
– Jeff Zurschmeide, shuttle passenger
“I can’t emphasize enough that this was happening in super slow motion,” said Zurschmeide, who has written a firsthand account of the incident. “I’m sitting there taking pictures. People in front are saying, ‘He’s going to hit us all right.’ The poor attendant is banging on the windows in the shuttle, yelling, ‘Hey! Hey!’ But it wasn’t going to help.”
The shuttle bus does not have traditional controls such as a steering wheel, brake pedal, or accelerator. But it can be manually operated with a small device that looks akin to a video-game controller, and for the purposes of the yearlong demonstration there is an attendant, a Keolis employee, aboard for all rides along the vehicle’s 0.6-mile fixed route. Barker said the attendant can use the controller to guide the shuttle through thorny situations, such as if a traffic light is out and a police officer is guiding traffic through an intersection. It is unclear in this case whether the attendant may have had an opportunity to guide the shuttle out of the truck’s path Wednesday.
Accounts vary as to what happened in the final seconds before the collision. Barker said the shuttle is equipped with a horn that activates when the shuttle’s lidar sensors detect that an object, be it another vehicle or a pedestrian, is getting too close to the vehicle. He said it sounded prior to Wednesday’s crash; Zurschmeide said he did not hear the horn.
Passengers step onto a Navya Arma autonomous electric shuttle during a demonstration on Fremont Street in downtown Las Vegas on November 8, 2017.
Further, Barker said, traffic behind the shuttle prevented it from backing up a few feet and avoiding the oncoming truck. Zurschmeide estimated there was a 20-foot gap between the rear of the shuttle and the car behind it, which raises the possibility that the shuttle was not physically blocked by traffic but boxed in by programmed limits of how close it could move toward another vehicle.
Would a human driver had reacted differently? Taken action?
“When I saw the truck start to come near us, the first thing I did was look behind to see if there was space, and I wondered if we were going to back up,” Zurschmeide said. “If you are a human driver, you know where the back of your car is. You can back up within five feet of another car pretty safely. But I think, just based on what I saw with the way they’ve got the shuttle behaving, it tended to keep more of a buffer between itself and other vehicles, more than a human would.”
Such prudence raises questions about the nature of autonomous vehicles, their behavior on public roads, and, more important, how they interact with human drivers in a traffic environment that blends human and machine. Jim McPherson, a California attorney who specializes in autonomous-vehicle law, said the crash exposes shortcomings in how industry considers operational design and vague safety parameters for autonomous vehicles.
“This accident is amazing, because it brings into stark focus what safety is all about. It’s not just doing the legal thing.”
– Jim McPherson, attorney
“I think this throws into crystal-clear perspective exactly what safety standards we really need, which is knowing whether autonomous vehicles have the ability to avoid an accident as well as a human can avoid it,” he said. “This accident is amazing, because it brings into stark focus what safety is all about. It’s not just doing the legal thing. You should take reasonable care to protect yourself from other people on the road. We do it instinctively and don’t give ourselves credit for our willingness to accommodate the mistakes of others.”
In short, he fears autonomous systems are designed to follow a one-dimensional focus on doing merely what is legal. That may shield manufacturers from liability, but it won’t deliver the safety benefits that manufacturers of autonomous technology promise. Instead, McPherson said, developers ought to design systems that take action on what’s legal, what’s safe, and what’s expected in driving culture.
“I think of those three things as interlocking circles, and staying in one of those circles is never the right thing to do,” he said. “All of us and autonomous vehicles need to have the judgment to know when to jump from one circle to the next.”
Though no changes were made to the shuttle’s control software in the wake of the incident, Barker acknowledged the interaction between human motorists and self-driving systems still requires study. That’s one reason the pilot project in Las Vegas is running in the first place. Keolis has also operated driverless Navya shuttles in London and in Paris and Lyon, France. Barker said the shuttles have been in service for thousands of hours and prior to Wednesday had never been involved in an incident.
“Obviously, all autonomous technology is still new, and part of this project is learning how you interject an autonomous transit system into a live traffic environment and do that safely and effectively,” he said. “For us, it’s understanding how the shuttle will operate and how to be careful of the behaviors of drivers around the vehicle. So that’s a continuous learning process happening in all forms of autonomy, whether it’s transit buses or single-occupant vehicles.”
The NTSB will be interested in those answers as well. This marks the agency’s second investigation into a crash involving automated technology, with the first being the fatal crash involving a Tesla Model S with the car’s Autopilot feature engaged. In that investigation, board members focused on the nature of interactions between the human driver and the advanced driver-assist feature. This one will be notably different, in that the focus will be on a fully autonomous vehicle’s interaction with its broader surroundings, including human motorists.
Toward that end, the incident in Las Vegas may be one small scrape for an autonomous shuttle but may be an equally important benchmark on the road to a self-driving future.