Evaluating the comfort of robot paths in varying-width corridors: passenger vs. observer perspectives

In corridors shared by humans and robots, mobile robots should follow paths that are comfortable for passengers and observers. Previous studies have examined straight corridors with uniform width; however, actual environments include varying-width corridors, such as hallways connected to open spaces or containing static obstacles. Comfortable path design in such environments is unclear, and differences between passenger and observer preferences remain underexplored. This study provides initial, context-specific empirical evidence on comfort preferences among robot paths in varying-width corridors from passenger and observer perspectives. Through experiments (n = 35), three paths were examined: a straight wall-following path, a center path with a small heading change, and a wall-following path with a larger heading change. Each path was evaluated in two perspectives (passenger and observer) and two environments with sudden or gradual width changes. Comfort was measured by ranking the three paths. A Plackett–Luce model was used to test within-condition path preferences, the effects of perspective and environment, and their interaction. Across all conditions, the straight wall-following path was mainly preferred. In the sudden-change environment, path preference differed significantly between perspectives: passengers preferred the center path over the path with the larger heading change, whereas observers showed no such preference and rated the latter relatively higher. No significant effect of environment or interaction was detected. These findings suggest that, within the scenarios tested, smaller heading changes are associated with comfort, whereas less center-aligned motion may be particularly relevant when observer comfort is prioritized.