Task difficulty, risk feeling, and safety margin in the determination of driver behavior to prepare for traffic conflicts

Abstract

Unpredictable pedestrian and cyclist behavior associated with their appearance on the road in blind spots contributes to traffic near-misses or crashes. When experienced drivers are confronted with uncertainty, they take defensive measures called hazard-anticipatory driving, such as decreasing the vehicle velocity and/or increasing the lateral distance. Our research sought to understand the motivational determinants and perceptual processes that determine driver behavior in preparation for traffic conflicts with covert hazards.This study aimed to investigate the influence of driving experience on drivers’ perceptions and behaviors to prepare for traffic conflicts. Two experiments were designed with 8 experienced and 13 inexperienced participants. In Experiment 1, participants were asked to provide their subjective impressions of task difficulty, feeling of risk, and statistical risk pertaining to assess their perceptions of the separation between task demand and capability after viewing animation clips of road scenes with blind intersections under different forced speeds. In Experiment 2, participants drove using a driving simulator in scenes with blind intersections, similar to those in Experiment 1. We sought to explore the motivational determinants of behavior regarding the relationship between subjective feelings and objective safety margins.The results showed that the driver’s perception of task difficulty correlated with their driving speed, and inexperienced participants tended to underestimate task difficulty compared to experienced participants. The task difficulty and the feeling of risk were strongly correlated regardless of experience, and estimation of statistical risk differed depending on experience. The subjective task difficulty (and/or risk feeling) and objective safety margin were strongly correlated for experienced participants. Experienced participants who perceived a higher degree of difficulty in the forced-paced driving task tended to have greater safety margins in the self-paced driving task. These findings suggest that experienced participants with individually tolerable safety margins adjust their driving velocity and/or lateral distance in the control of task difficulty (and/or risk feeling) to prepare for traffic conflicts. Therefore, the underestimation of task difficulty should be considered when designing effective measures, such as driver assistance systems, to guide inexperienced drivers toward normative behaviors.