Travel path conditions dictate the manner in which individuals avoid collisions.

The ability to perceive the motion of approaching objects and to make appropriate adjustments to avoid collisions is an essential component of safe locomotion through the environment. No previous study has looked at actual behavioural responses in a realistic collision avoidance task. We investigated individuals' collision avoidance behaviour with an approaching object in order to understand the visual information used to accomplish the task. We found that when individuals were walking towards a goal without any restrictions, a change in travel path occurred at the same time, independent of the object's approach velocity. However, the lateral rate of change in the travel path was significantly slower for the slower approach velocity. We found that when a restriction was present along the travel path, individuals were exposed to the object's properties for longer and a change in travel path occurred later for slowest approaching velocities than for the fastest approaching velocities. The results suggest that individuals are capable of determining TTC from an approaching object during actual self-motion, but the motor parameter it modulates is different for different circumstances.