This image is why self-driving cars need many types of sensors

Autonomous cars often proudly claim to be fitted with a long list of sensors--cameras, ultrasound, radar, lidar, you name it. But if you've ever wondered why so many sensors are required, look no further than this picture. You're looking at what's known in the autonomous-car industry as an "edge case"--a situation where a vehicle might have behaved unpredictably because its software processed an unusual scenario differently from the way a human would. In this example, image-recognition software applied to data from a regular camera has been fooled into thinking that images of cyclists on the back of a van are genuine human cyclists. This particular blind spot was identified by researchers at Cognata, a firm that builds software simulators--essentially, highly detailed and programmable computer games--in which automakers can test autonomous-driving algorithms.