Abstract : Safety is an important issue of driverless car. Yet, most current approaches fail to ensure safety even in a fully informed situation. In this paper we discuss how the safety criteria apply when the robot uses its on board sensors to evolve in a environment populated with static and moving obstacles. The sensors can only provide a partial and uncertain knowledge of the surroundings. We show that the usual safety notion does not apply for this relevant case and discuss which safety guarantees can be given and how to achieve them.