Framework for a conflict typology including contributing factors for use In ADS safety evaluation

The aim of a successful conflict typology (also sometimes called crash or maneuver typology) is to group conflicts, some of which may result in a collision, into groups that have common characteristics influencing avoidability and potential severity. A conflict typology can be used in safety impact methodologies that analyze and predict the potential performance of a safety countermeasure or system within a set of defined crash modes. More generally, conflict typologies are used across many traffic safety analyses, including those related to evaluating the safety of an Automated Driving System (ADS). The objective of this paper was to describe a conflict typology including contributing factors that can be used in both Automated Driving System (ADS) and human driven vehicle safety evaluations. The proposed typology is comprised of 5 layers: (1) conflict partners - the types of the actors or objects involved in a conflict, (2) conflict group - the high-level description of a conflict, (3) conflict perspective - assigned to each actor based on their relative maneuvering, (4) the actor role - either the initiator of some surprising action that leads to a conflict or the responder, and (5) contributing factors - factors that in combination contributed to the conflict initiating or non-nominal response that caused the conflict. The main contribution of the proposed conflict typology and contributing factors are applicable conflicts from both retrospective crash data and near-crashes from a naturalistic driving study (NDS), and in the future ADS conflicts. The results also highlight potential difficulties reconciling differences in contributing factors observed in high-severity crash data having limited contributing factor information and those contributing factors observed in lower severity NDS data.