Temporal Characteristics in Detecting Imminent Collision Events on Linear Trajectories

Previous research (Andersen & Kim, 2001) has shown that a linear trajectory collision event is specified by objects that expand and maintain a constant bearing (the object projected location in the visual field). In this research, we investigated the temporal characteristics in detecting such imminent collision events. Two experiments were conducted in which participants were presented with displays simulating a single approaching object in the scene while observers were either stationary or moving at one of the 3 speeds (24, 36, or 48 km/h). An object traveled for 9 seconds before colliding with or passing by the observer and the relative speed between object and observer remained constant. Participants were asked to report whether the object was on a collision path or not. In the first experiment, 3 seconds or 4 seconds of displays were presented that ended at the same 2-second time to contact (TTC) position. In the second experiment, 3 seconds of displays were presented that ended at different TTC positions. Results show that observers were more accurate in collision detection in stationary condition than in motion. More importantly, results suggest that observers used information on bearing change rate to distinguish noncollision objects from collision objects.