Avoidance behaviours while circumventing to the left or right of someone with different shoulder widths and facing directions: How do side, width, or orientation matter?

Background: Collision avoidance during locomotion is influenced by a variety of situational factors. When circumventing around an inanimate object, the amount of clearance is dependent on the side of avoidance. When avoiding other pedestrians, individuals most often choose to walk behind a moving pedestrian, and avoid people differently depending on their body size. However, side of avoidance has not been evaluated with human obstacles, nor facing direction of a stationary pedestrian, nor the size of a single pedestrian. Therefore, the aim of this study is to evaluate these knowledge gaps concurrently.

Research Question: How do people avoid a collision to the left-side or right-side of a single stationary pedestrian (interferer) of varying shoulder width and orientation?

Methods: Participants (n = 11) walked along a 10 m pathway towards a goal, while a stationary interferer stood 6.5 m from the start. The interferer faced one of three directions relative to the participant (orientation); forward, leftward, or rightward, with either their normal shoulder width or enlarged width created by wearing football shoulder pads. Participants were explicitly instructed as to which side of the interferer to avoid (forced-left vs forced-right). Each participant completed 32 randomized avoidance trials. Centre of Mass separation at the time of crossing was used to examine individual's avoidance behaviours.

Results: Results revealed no effect of interferer width, but a significant side of avoidance effect, where the centre of mass separation between the participant and interferer at the time of crossing was smallest when participants avoided to their left.

Significance: Findings suggest that changing the facing direction or artificially increasing the shoulder width of a stationary interferer will not affect one's avoidance behaviours. However, an asymmetry in side of avoidance is maintained similar to that observed in obstacle avoidance behaviours.