Traffic density at sea has constantly grown over the last years due to rising shipping of goods. As a consequence it has become a more and more difficult task for the ship's operating crew to assess a traffic situation and anticipate its future development. Automated collision avoidance systems can assist the crew in this task to reduce the number and severity of accidents. Such a system is the MTCAS (Maritime Traffic Alert and Collision Avoidance System). Before safety-critical systems like this can go to market they have to undergo a verification and validation process to ensure safety. An important part of this process is the hazard and risk assessment. In this paper we review the state of the art of existing methods for hazard and risk assessment with regard to their applicability to highly automated systems. After identifying the limitations of existing methods we propose a new method especially tailored for highly automated systems and exemplary apply it to MTCAS.