Safety assessment of Highly Automated Vehicles, including Advanced Driver Assistance Systems and Advanced Driving Functions, is of paramount importance for the acceptance and diffusion of these technologies. On-road testing alone is no option due to the enormous time requirements, so virtual testing is generally considered to be a necessary complement. While more time efficient than on road testing, also virtual testing cannot be performed for all possible situations.Moreover, virtual testing can be even misleading if the considered scenarios are not realistic or do not include the critical situations which can occur in the intended real traffic use. Against this background, we discuss different options and challenges as well as outlooks.