"Why This Avoidance Maneuver?" Contrastive Explanations in Human-Supervised Maritime Autonomous Navigation

TL;DR

This paper introduces contrastive explanations for maritime collision avoidance systems to improve human understanding, balancing transparency with cognitive workload considerations.

Contribution

It proposes a method for generating human-centric contrastive explanations and evaluates their effectiveness in maritime navigation scenarios.

Findings

Contrastive explanations help marine officers understand system objectives.

Explanations are most valuable in complex multi-vessel encounters.

Explanations can increase cognitive workload, indicating need for scenario-specific strategies.

Abstract

Automated maritime collision avoidance will rely on human supervision for the foreseeable future. This necessitates transparency into how the system perceives a scenario and plans a maneuver. However, the causal logic behind avoidance maneuvers is often complex and difficult to convey to a navigator. This paper explores how to explain these factors in a selective, understandable manner for supervisors with a nautical background. We propose a method for generating contrastive explanations, which provide human-centric insights by comparing a system's proposed solution against relevant alternatives. To evaluate this, we developed a framework that uses visual and textual cues to highlight key objectives from a state-of-the-art collision avoidance system. An exploratory user study with four experienced marine officers suggests that contrastive explanations support the understanding of the system's objectives. However, our findings also reveal that while these explanations are highly valuable in complex multi-vessel encounters, they can increase cognitive workload, suggesting that future maritime interfaces may benefit most from demand-driven or scenario-specific explanation strategies.