Exploring the Relationship Between "Positive Risk Balance" and "Absence of Unreasonable Risk"

TL;DR

This paper analyzes the concepts of positive risk balance and absence of unreasonable risk in automated driving safety, clarifying their interpretations and proposing that they can complement each other within safety assurance guidelines.

Contribution

It provides a clear overview of PRB and AUR, identifies two interpretations of PRB, and discusses their implications for international ADS safety standards.

Findings

Two interpretations of PRB exist and can be distinguished.

Misunderstanding PRB interpretations can lead to disagreements.

Both interpretations can be integrated into non-prescriptive safety guidelines.

Abstract

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.