The problem echoes that of previous driverless car accidents, where sensors were blind to an unusual circumstance. In February, a Google driverless car was ruled at fault in a crash, as it changed into a lane prematurely and collided with a bus that did not see it signaling. When a Tesla car on autopilot crashed and killed its owner in the United States, it sparked a Federal investigation. The Tesla crash, where the car collided with a trailer crossing the road, was likely because the car's sensors couldn't tell the white side of a trailer apart from the blank space of the sky, and failed to stop in time.