  International discussions on the overarching topic of how to define and
quantify what a "safe enough" Automated Driving System (ADS) is are currently
hinged on the question of determining the relationship between "positive risk
balance" (PRB) and "absence of unreasonable risk" (AUR). In order to advance
the conversation on these important safety topics at the international level,
it is first important to start from a shared common understanding, grounded in
clear definitions and terminology. To that end, this paper will start with an
overview of the notions of PRB and AUR; it will then summarize different
positions of the present debate; finally, it will conclude that two possible
interpretations exist for PRB, and that failure to distinguish them can lead to
misunderstanding different parties' positions. The argumentation in this paper
is aimed at showing that the two interpretations for PRB can actually
complement each other, but can be considered independently, and can both be
subsumed within non-prescriptive guidelines toward ADS safety assurance.
