The effect of an occlusion-induced delay on braking behavior in critical situations

Abstract

Objective: To share results of an experiment that used visual occlusion for a new purpose: inducing a waiting time. Background: Senders was a leading figure in human factors. In his research on the visual demands of driving, he used occlusion techniques. Methods: In a simulator experiment, we examined how drivers brake for different levels of urgency and different visual conditions. In three blocks (1 = brake lights, 2 = no brake lights, 3 = occlusion), drivers followed a vehicle at 13.4 or 33.4 m distance. At certain moments, the lead vehicle decelerated moderately (1.7 m/s²) or strongly (6.5 m/s²). In the occlusion condition, the screens blanked for 0.4 s (if 6.5 m/s²) or 2.0 s (if 1.7 m/s²) when the lead vehicle started to decelerate. Participants were instructed to brake only after the occlusion ended. Results: The lack of brake lights caused a delayed response. In the occlusion condition, drivers adapted to the instructed late braking by braking harder. However, adaptation was not always possible: In the most urgent condition, most participants collided with the lead vehicle because the ego-vehicle’s deceleration limits were reached. In non-urgent conditions, some drivers braked unnecessarily hard. Furthermore, while waiting until the occlusion cleared, some drivers lightly touched the brake pedal. Conclusion: This experimental design demonstrates how drivers (sometimes fail to) adjust their braking behavior to the criticality of the situation. Application: The phenomena of biomechanical readiness and (inappropriate) dosing of the brake pedal may be relevant to safety, traffic flow, and ADAS design.