Walking speed and trunk sway: Influence of an approaching person's gait pattern on collision avoidance

International audienceGait patterns provide a rich source of person-specific information such as age, sex, identity, and vulnerability. However, it is unknown to what extent person-specific gait information can affect collision avoidance behaviours with an approaching “person”. We sought to determine whether young adults’ spatiotemporal avoidance behaviours were affected by changes to a virtual agent’s gait parameters (i.e., speed or trunk sway). In a virtual environment (FOVE head-mounted display; 70Hz), young adults (n=21) walked along an 18m pathway towards a goal while avoiding an approaching virtual agent. The agent’s walking speed and trunk sway magnitude were a multiples of each participant’s average speed or sway: fast (x1.5m/s), normal (matched), or slow (x0.8m/s); large (2x), normal (matched), or small (0x) respectively. The agent was non-reactive and walked straight forward at a constant speed. Participants’ kinematics were recorded (Qualisys; 120Hz) to examine avoidance behaviours of initiation of path deviation and medial-lateral clearance at the time of crossing. Statistical analysis revealed that participants initiated a path deviation (i.e., estimate of time-to-contact, TTC) significantly earlier (F(2,40)=11.31, p<.001, f=.69) when the agent was walking fast (M=3.93s, SD=.56) as opposed to normal (M=4.31s, SD=.33) and slow (M=4.41s, SD=.44) walking speeds. However, the agent’s trunk sway magnitudes did not affect participants’ initiation of path deviation or medial-lateral clearance at crossing. Participants appear not to use temporal information to initiate an avoidance, but rather a point in space (i.e., TTC was affected by approach speed) due to awareness that the agent was non-reactive and always approaching. The agent’s sway magnitude did not affect medial-lateral avoidance behaviours most likely because there was little observable difference between conditions (i.e., ~3° normal sway). Conceivably, the study’s environmental conditions may underrepresent people’s behaviours in real-world. Future work is needed to understand the perception of an approaching person’s gait characteristics on collision avoidance