The crashes involving Tesla vehicles striking stationary objects—the crash attenuator in California, a stopped fire truck in Utah in May, and another fire truck in California in January—show the limitations of relying on just cameras and radar, says Raj Rajkumar, director of the Connected and Autonomous Driving Collaborative Research Lab at Carnegie Mellon University in Pittsburgh. Camera-based systems have to be trained to recognize specific images, and if they encounter something in the real world that doesn't match their expectations, the radar has to pick it up, Rajkumar said.