I have a sneaky feeling that detecting whether a driverless car has hit a cyclist is not an easy problem. I can imagine scenarios where the contact took place towards the rear of the car (and therefore not at the primary focus of sensor attention), the cyclist goes careening off to the left or right and the car blithely goes on. I'm not saying such a scenario is impossible with a traditional car but it's a dam sight harder to ignore.

OnStar Corporation is a subsidiary of General Motors that provides subscription-based communications, in-vehicle security, emergency services, hands-free calling, turn-by-turn navigation, and remote diagnostics systems throughout the United States, Canada, China, Mexico, Europe, Brazil, and Argentina