Could Nio's Safety-Certified Yoke Steer-By-Wire be Safer Than Tesla's?

Motor Trend

27-05-2025

We love the Tesla Cybertruck's steer-by-wire system's functionality so much we awarded it a Best Tech award for 2025. We like how it works and love the way Tesla continually challenges the status quo. But a recent trip to China introduced a tiny sliver of doubt as to exactly what authority—if any—signed off on the safety of that technology. The Tesla system is clearly built with redundancy—there are two steering motors fed by separate wiring, etc. But the Chinese EV automaker Nio claims that its steer-by-wire system, now in use in its Nio ET9 flaship, is the first in production to have undergone a full safety certification. The company collaborated with other manufacturers to develop a triple-layer redundancy system, one informed by aviation-industry best-practices, that then passed a Chinese government certification program.
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First Level Redundancy
At this level, all computer controls, communication, and electromechanical controls are duplicated. This much everybody does. Nio also uses separate electrical architecture zones to control the twin communication and power paths, with an independent monitor comparing signals. In the event of a discrepancy, the monitor determines a 'winner.' Nio, and many others offering steer-by wire use a single motor with multiple phases in the winding, wired to the disparate control systems—either of which has sufficient power to steer the vehicle (other systems provide for a fail-safe mechanical shaft connection). There are separate DC-DC converters, separate CAN bus connections, multiple steering torque sensors, and steering-yoke position sensors.
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Tesla Rear Steering Rack
Second Level Redundancy
Here's where we believe the Nio approach deviates from Tesla's in following aviation's lead. The separate zones and their communications networks were developed by different teams and sourced from different suppliers whenever possible. This helps minimize the chance of a common failure mode or use-case scenario crippling both systems at the same time.
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Tesla Cybertruck showing front and rear tires at max turning angle.
Third Level Redundancy
In an absolute worst-case scenario when a steering order fails to be executed by either of these disparate control, communication, and execution systems, the computer is programmed to utilize other approaches to execute the intended steering request. This can include activating the rear steering (which the ET9 and Cybertruck are both equipped with), and/or heavily braking one or both inside wheels on the side in which the car is intended to steer.
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Nio ET9 luxury sedan steering wheel.
Measuring Results
During the lengthy development of the Nio ET9's steering system, the company and the homologation reps from the government considered the job done when recorded failures could be measured in events-per-trillion-hours of operation. We're eager to learn more about the various layers of redundancy Tesla employs, and we'd love to know how Tesla's system would fare if subjected to this same new Chinese homologation testing, but for now the Cybertruck's form factor is disallowed in China.