How Amazon-owned Zoox designed its self-driving vehicles to prevent crashes

The hubbub surrounding the autonomous vehicle industry often focuses on venture capital rounds, speculation about IPOs and acquisitions. But the industry’s future also hinges on the high-stakes task of proving the technology can operate safer than human drivers do today and gaining the public’s trust. In short: safety matters.

Zoox issued a safety report Tuesday that aims to give new insight into its custom electric autonomous vehicle and describes in greater detail various design details aimed at preventing crashes and protecting if they do.

“As you know, and something everybody keeps talking about, is that part of the rationale for doing AVs is because of safety, safety, safety, but they never get to the next bullet [point] right? What are you going to actually do to prevent those crashes, to save those lives?” Mark Rosekind, the company’s chief safety innovation officer and former head of the National Highway Traffic Safety Administration, told TechCrunch in a recent interview.

Rosekind says this latest report answers those questions.

Zoox is a bit different from its rivals. It isn’t just developing the self-driving software stack. The company is responsible for creating the on-demand ride-sharing app and the vehicle itself. Zoox also plans to own, manage and operate its robotaxi fleet.

Zoox unveiled in December the electric, autonomous robotaxi it built from the ground up — a cube-like vehicle loaded with sensors, no steering wheel and a moonroof that is capable of transporting four people at speeds of up to 75 miles per hour. At the time, Zoox shared a few specs on the four-seat vehicle, including the face-to-face symmetrical seating configuration, similar to what a train traveler might encounter, and the 133 kilowatt-hour battery that the company said allows it to operate for up to 16 continuous hours on a single charge. But not everything was revealed, particularly details about how it would protect occupants in the vehicle as well as the pedestrians, cyclists and other drivers it will be sharing the road with.

To be clear, Zoox is not the only AV company issuing safety reports. Voluntary safety self-assessment reports, or VSSAs, have become fairly common in the industry. These voluntary safety reports, which are included in NHTSA’s Automated Driving Systems VSSA Disclosure Index, are supposed to cover 12 areas, including the vehicle’s design, crash simulation scenarios and benchmarks for testing, as well as protective measures for occupants and other road users.

Zoox’s first safety report came out in 2018, which outlined the company’s “prevent and protect” philosophy. This latest one reveals how Zoox plans to meet its safety goals, including specific details on the design of the vehicle. And more safety reports are coming — per a few hints in this latest one — including details about its collision avoidance system and the lighting system the vehicle uses for communicating with other road users.

Zoox has designed and included more than 100 safety innovations into its purpose-built vehicle. Rosekind shared details on nine of them that fall into three categories: driving control, no single point of failure and rider protection.

Driving control

Zoox at Coit Tower

Image Credits: Zoox

Zoox’s vehicle has independent braking and an active suspension system, which means that each of the brakes has its own electronic control unit, allowing for more control over traction on the road and weight distribution. All of that translates to shorter stopping distances.

The vehicle also has four-wheel steering, which Rosekind noted doesn’t exist on any AV car on the road today, and is bidirectional. Four-wheel steering allows the vehicle to simultaneously adjust where it is headed and its position within the lane.

“Once our software has determined the path for the vehicle, it’ll stay on that path down to centimeters accuracy — even at speed through a curb, Rosekind explained.

The four-wheel steering combined with the vehicle’s symmetrical design allows for it to travel bidirectionally. The bidirectional capability means no more U-turns or three-point turns, two maneuvers that are more complex, time consuming and can make occupants more vulnerable to oncoming traffic. 

No single point of failure

Rosekind said the company’s design objective was that there would be no single point of failure for its safety critical systems. For instance, the vehicle has two powertrains. The motors, drive systems and batteries work in conjunction with each other. If one component in the system fails, the other one will take over.

The vehicle also has two batteries as well as a safety diagnostics system that monitors all of the hardware, software and firmware. Sensors like lidar and radar are also placed on the four corners of the vehicle — each one provides a 270-degree field of view.

The diagnostic system goes beyond monitoring and will mitigate a failure or performance problem that it identifies. For instance, if a sensor has degraded performance from damage or debris, it will activate a cleaning system on the vehicle or turn it from bidirectional to unidirectional, placing the sensor in a position where it basically doesn’t matter if it is obscured, Rosekind explained. 

“Fail-safe operational means it’s going to continue the ride, let you out, and then go take care of whatever the issue is, or pull over to a safe spot,” he said.

Rider protection

Zoox Seatbelt Notification

Image Credits: Zoox

Zoox’s goal is for its vehicle to meet five-star crash protection for every seat in the vehicle. The vehicles are currently going through crash testing now, Rosekind said, adding that it is “going quite well and almost complete.”

The company also designed a new kind of airbag system that contains five different airbags. Curtain airbags are on each side of the vehicle, a frontal one is divided in two parts to protect the head, neck and chest. There are also rear and side seat airbags.

Within the system is an airbag control unit that can monitor where a collision is coming as well as the velocity and determine which airbags and in what order to deploy. Instead of every airbag deploying at once, they will inflate based on the collision location and the severity of the impact.

Finally, the vehicle has sensors in the seat, the buckle and even the coating on the webbing of the seatbelt to be able to tell if passengers are using the seatbelt. The vehicle will not start until everybody’s buckled up, Rosekind said.