The “Out-of-the-Loop” concept in automated driving: proposed definition, measures and implications

TLDR

Despite widespread use of the term “Out of the Loop” (OOTL) in automated driving research, there is no consensus on its definition, measurement, or practical implications. This paper aims to establish a shared understanding of the OOTL concept for academics and practitioners. By reviewing existing definitions, outlining concepts from human‑factor literature, and convening a multinational working group, the authors propose a precise definition of being in, out, or on the loop in driving. The proposed definitions link driver physical control and monitoring demands, and the paper discusses how to operationalize them and their implications for automated driving development.

Abstract

Despite an abundant use of the term "Out of the loop" (OOTL) in the context of automated driving and human factors research, there is currently a lack of consensus on its precise definition, how it can be measured, and the practical implications of being in or out of the loop during automated driving. The main objective of this paper is to consider the above issues, with the goal of achieving a shared understanding of the OOTL concept between academics and practitioners. To this end, the paper reviews existing definitions of OOTL and outlines a set of concepts, which, based on the human factors and driver behaviour literature, could serve as the basis for a commonly-agreed definition. Following a series of working group meetings between representatives from academia, research institutions and industrial partners across Europe, North America, and Japan, we suggest a precise definition of being in, out, and on the loop in the driving context. These definitions are linked directly to whether or not the driver is in physical control of the vehicle, and also the degree of situation monitoring required and afforded by the driver. A consideration of how this definition can be operationalized and measured in empirical studies is then provided, and the paper concludes with a short overview of the implications of this definition for the development of automated driving functions.