With the growing demand of personal assistance to mobility and mobile service robotics, robot navigation systems must be "aware" of the social conventions followed by people. They must respect proximity constraints but also respect people interacting. For example, they may not break interaction between people talking, unless the occupants want to take part in the conversation. In this case, they must be able to join the group using a socially adapted behavior. This paper proposes a risk-based navigation method including both the traditional notion of risk of collision and the notion of risk of disturbance. Results exhibit new emerging behavior showing how a robot takes into account social conventions in its navigation strategy. agents. An approach to take advantage of o-space in robot autonomous navigation, is also described.