Constraints matter: Virtual pedestrians with mobility constraints affect individuals' avoidance behaviours

Walking in urban settings requires people to negotiate crowds. In these situations, people typically want to maintain a level of personal space around themselves. Recent work on one-versus-one interactions demonstrated that whether one of the pedestrians looked distracted or interacted with an object (e.g., stroller, bike) predicted the medial-lateral separation between them as they walked past each other. However, this work did not distinguish between the type of object interaction (or mobility constraint) and thus, it is unclear whether different constraints have different effects on avoidance behaviours. Here we tested the hypothesis that the type of object an approaching pedestrian held or pushed would affect the extent of path deviation, which would also depend on the distractedness of the pedestrian. To address this hypothesis, we created an immersive virtual environment that consisted of a 3.5-m-wide paved urban path. Participants had to walk and avoid colliding with approaching virtual pedestrians that often held a shopping bag or pushed a bike or stroller while looking straight ahead or off to the side as if distracted. Distraction did not affect avoidance behaviours. However, participants increased medial-lateral separation with the virtual pedestrian at the time of crossing when a stroller was present compared to the other mobility constraints. The type of mobility constraint also differentially affected onset of deviation and rate of progression before and after a path deviation. These results support the idea that characteristics of the obstacle to avoid (in this case, a virtual pedestrian) influence collision avoidance behaviours.