Most self-driving companies say this tech is crucial. Elon Musk disagrees.

Radar waves will bounce under a tractor-trailer, according to Frankenberg, the radar startup CEO, making the car think there’s a clear path ahead. Cameras can struggle to differentiate a white side of a truck from a bright sky overhead.

“The system would be better and have higher reliability if it included lidar,” said John Dolan, a professor at the Carnegie Mellon University Robotics Institute. “It’s definitely going to see a large truck or vehicle that’s crossing in front of you.”

A Daimler research paper on state-of-the-art radar concluded that radar isn’t sufficient for full self-driving, and developments are needed to comprehensively understand stationary objects. In March 2018, a man died using Autopilot when his Model X crashed into a concrete barrier on a California highway.