Movement conventions must be predictable
Aliases: predictable robot motion · social navigation conventions · passing-side consistency
What it is
Predictable shared-space navigation conventions let bystanders anticipate a robot's route, passing side, and speed changes in corridors, doorways, and crossings. Predictability does not require an immutable path. It requires similar situations to produce similar conduct and any revision to become legible early through continuous motion.
Why it happens
Pedestrian coordination relies on short-horizon prediction of future positions, not distance alone. A robot that oscillates between candidate paths or sidesteps late invalidates that prediction; both parties may choose the same escape side and correct repeatedly. A stable passing side, smooth curvature, and early path commitment narrow the set of plausible intentions. Collision-free arrival alone misses this burden because a successful encounter can still involve a startle or emergency stop.
Studying it
Controlled head-on, crossing, and overtaking encounters can compare a consistent convention with late choice or replanning oscillation. Useful factors include passing-side consistency, commitment onset, curvature, and pedestrian flow direction. Outcomes include avoidance onset, number of path corrections, minimum passing distance, traversal time, pauses, and perceived predictability and safety. Trajectories and subjective reports should be combined: a person may produce a clean path only by doing all the coordination. Arrival direction and trial order require counterbalancing, while local traffic customs must be reported.
Where it stops holding
A keep-left or keep-right convention may work in a directional corridor but fail during wheelchair encounters, queues, cleaning work, or temporary closures. Predictability must not become rigid path assertion when someone enters unexpectedly. Dyadic laboratory passing also underrepresents crowds, where groups, occlusion, and bystanders change who can see the robot's motion cue.
Applying it
- Define default passing sides and precedence separately for corridors, doorways, and intersections, then keep them consistent within a site.
- Make the main turn before entering the conflict area; if replanning is unavoidable, use continuous deceleration and a visible curvature transition instead of side-to-side oscillation.
- Replay repeated encounters and annotate first pedestrian avoidance, robot replans, and mutual pauses. Repeated second corrections call for earlier commitment, not merely more sensitive obstacle avoidance.